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1.
  • Alvfors, Per, et al. (författare)
  • Forskarskolan Program Energisystem : Kunskapsutveckling genom samverkan mellan teknik- och samhällsvetenskap : slutrapport 2016, Forskningssyntes för konsortiet Byggnader i energisystem
  • 2016
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Denna rapport ger en kortfattad översikt och syntes av tvärvetenskapliga forskningsresultat från verksamheten i konsortiet Byggnader i energisystem inom forskarskolan Program Energisystem. Tonvikten ligger på tiden från forskarskolans start 1997 till dess 15-årsjubileum 2012, men hänvisningar görs även till forskning publicerad därefter. Utgångspunkten har varit att lyfta fram det tvärvetenskapliga inom forskningen för att visa hur forskarskolan har bidragit till tvärvetenskaplig kunskaps- och metodutveckling.I rapporten ges en översikt över fallstudier och avhandlingar inom konsortiet och de tvärvetenskapliga forskningsresultaten sammanfattas inom tre huvudsakliga tematiska områden: (1) Passivhus: boende och energieffektiva byggnadstekniker,(2) Energieffektivisering: processer och aktörer, samt (3) Energianvändning, vardagsaktiviteter och småskalig solenergi i hushåll. Tvärvetenskapliga metoder och resultat sammanfattas och utvecklingen av samarbeten och angreppssätt beskrivs. Rapporten avslutas med några sammanfattande reflektioner kring hur framgångsrik tvärvetenskaplig forskning bör bedrivas.
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2.
  • Alvfors, Per, et al. (författare)
  • Forskarskolan Program Energisystem : kunskapsutveckling genom samverkanmellan teknik- och samhällsvetenskap : slutrapport 2016, Forskningssyntes för konsortiet Lokala och regionala energisystem
  • 2016
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Forskarskolan Program Energisystem har med sina fem deltagande forskningsavdelningar från Chalmers tekniska högskola, Linköpings universitet, KTH och Uppsala universitet varit banbrytande inom tvärvetenskaplig energisystemforskning och dess tre konsortier har spelat en viktig roll för forskarskolans utveckling. Konsortierna är inriktade på byggnader i energisystem, industriella energisystem samt lokala och regionala energisystem. I varje konsortium har doktorander och seniorer från minst två av de deltagande avdelningarna bedrivit tvärvetenskaplig forskning.I det lokala och regionala konsortiet har forskningsfrågorna kretsat kring aktörer och processer av betydelse för energisystemen i svenska kommuner, län och regioner. Inom konsortiet har frågeställningar om miljömässigt, socialt och ekonomiskt hållbara lokala och regionala energisystem bland annat studerats genom att analysera aktörers agerande och politiska processer inom de tekniska, ekonomiska och institutionella villkor som utgör begränsningar och möjligheter för energisystemen. En tydlig trend inom konsortiets forskning under forskarskolans arton år är att inriktningen gått i riktning från lokal till regional och från stationära till mobila energisystem. Den förskjutningen följer också den ökande betydelse som regioner i form av länsstyrelser har fått för samordningen av energi- och klimatplaneringen i Sverige under det senaste decenniet. Kommunerna har fortfarande en dominerande position genom den energirelaterade infrastruktur som de förfogar över men en förskjutning mot ett mer regionalt inflytande är tydlig.Totalt har 26 doktors- och en licentiatexamen avlagts av konsortiets doktorander och dessa alumner är nu verksamma inom energirelaterade verksamheter Sverige. Den främsta representationen finns inom myndigheter och akademier.
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4.
  • Alvfors, Per, et al. (författare)
  • Forskarskolan Program Energisystem : kunskapsutveckling genom samverkanmellan teknik- och samhällsvetenskap : slutrapport 2016, Huvudrapport
  • 2016
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Idén att samhällsvetenskaplig och teknisk energisystemforskning måste vävas samman för att utveckla ny kunskap och få ökad samhällsnytta var utgångspunkt när Program Energisystem startade år 1997.Program Energisystem identifierade tidigt kärnvärden som visades vara viktiga framgångsfaktorer:Energisystem med tyngdpunkt på användarsidanTvärvetenskaplig, universitets- och fakultetsöverskridandeforskning och forskarutbildningSammanhållen forskarskolaFinansiering av hela doktorandprojektSamarbeten i tematiska forskningsområdenKontinuerlig tvärvetenskaplig utvecklingLångsiktig finansiering av samordningsstrukturProgram Energisystems arbete har kännetecknats av:Val av samhällsrelevanta projekt av hög vetenskaplig kvalitetGemensamma tvärvetenskapliga kurser och projektarbetenTvärvetenskaplig handledningKontinuerligt arbetande fora för diskussionoch kontakter över ämnesgränserForskningssamarbeten mellan seniorer i olika ämnenAktivt doktorand- och alumninätverkForskarutbildningens målsättning har varit att utbilda bättre samhällsvetareoch bättre ingenjörer, inte att göra samhällsvetare av ingenjörerna eller ingenjörerav samhällsvetarna.I den kontinuerliga utvecklingen av Program Energisystem har ett förtroendefullt samarbete utvecklats som möjliggjort kontinuerliga förbättringar av forskningen och forskarutbildningen.Arvet från Program Energisystem har förts vidare i den nya Forskarskola Energisystem. Forskarskola Energisystem har en delvis annan struktur men bygger innehållsmässigt vidare på centrala idéer från Program Energisystem. Det finns ett fortsatt stort behov av tvärvetenskaplig kunskapsutveckling på energiområdet som främst handlar om att förstå komplicerade samband och processer och hur dessa kan påverkas.
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5.
  • Alvfors, Per, et al. (författare)
  • Forskarskolan Program Energisystem: Kunskapsutveckling genom samverkanmellan teknik- och samhällsvetenskap : Slutrapport 2016, Forskningssyntes för konsortiet Industriella energisystem
  • 2016
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Denna syntesrapport är en sammanfattning och analys av den forskning som bedrivits inom ramen för det Industriella konsortiet från år 1997 (konsortiets verksamhet startade 1999) inom ramen för forskarskolan Program Energisystem. Under denna tid har 25 doktorsavhandlingar och en licentiatavhandling producerats inom det Industriella konsortiet. Avhandlingarna sammanfattas och analyseras i denna syntesrapport och arbetet avgränsas då till att studera avhandlingarnas Problemområde, Verktyg/Metod/Teori, Systemgräns, studerad Sektor och Övergripande resultat. Vidare ges, med utgångspunkt från dessa forskningsresultat, förslag på fortsatt forskning för hållbara och effektiva energisystem.Många viktiga problemområden har studerats inom ramen för forskarskolans Industrikonsortium. Ett flertal avhandlingar behandlar möjligheter att minska utsläppen av växthusgaser från industrin och här har flera sektorer studerats, bland annat massa- och pappersindustrin, järn- och stålindustrin, kemiindustrin och oljeraffinaderiindustrin. Ett centralt tema i avhandlingarna är potentialer för energieffektivisering i industrisektorn, inte minst vid införande av bioraffinaderikoncept i framtiden. Här analyseras t.ex. tekniska potentialer, kostnadseffektivitet för energieffektiviseringsåtgärder, samt betydelsen av energiledning och styrmedel.I avhandlingarna har en mängd olika metoder och verktyg använts. Den i särklass mest använda vetenskapliga metoden är intervjuer (15) följt av scenarioanalys (10), dokumentstudier (9), simuleringsberäkningar (9), pinchanalys (9) och optimering (8). Fallstudiemetodik där mer än en metod används för att studera ett specifikt fall, t.ex. ett företag, förekommer i flera avhandlingar. En grundtanke i forskarskolan Program Energisystem har varit att forskaren måste vara medveten om att resultat från energisystemanalyser kan påverkas av vilka systemgränser som valts. I flertalet av Industrikonsortiets avhandlingar har Europas elsystem utgjort systemgräns då effekter av förändrad elanvändning eller elproduktion analyserats.Industrikonsortiets forskningsresultat visar på många intressanta slutsatser. Det påvisas att det finns energieffektiviseringspotentialer både i nya investeringar och i energiledningsåtgärder, som att justera driftsbetingelser för befintlig teknisk utrustning och ändra beteenden. Det konstateras också att energisamarbeten mellan industri och energibolag med syfte att öka användningen av industriell överskottsvärme i många fall är en hållbar lösning som minskar regioners behov av primärenergi och reducerar utsläppen av växthusgaser. Hinder mot sådana samarbeten kan vara att detta inte är en del av industrins kärnverksamhet. Det konstateras även att energisamarbeten mellan närliggande anläggningar i ett industrikluster kan leda till avsevärt större energieffektiviseringspotentialer än om var och en av de ingående industrierna arbetar enbart med interna åtgärder. Hinder mot denna typ av samarbete är brist på etablerade affärsmodeller. Forskningen visar på ett behov av fortsatta studier kring begreppet kärnverksamhet och dess påverkan på energifrågan i svensk industrin. Avskiljning och lagring av koldioxid (CCS) från industrin har studerats och här konstateras att denna lösning inte är ekonomiskt lönsam med dagens förutsättningar. Det rekommenderas därför att framtida forskning bedrivs för att studera vilka styrmedel som skulle behövas för att CCS ska bli ekonomiskt intressant för industrin. En annan viktig fråga är hur energitjänsteföretag ska formulera affärsmodeller och strategier kring CCS, samt hur de kan samarbeta med industrin för att på affärsmässiga grunder få till stånd CO2– avskiljning, transport och lagring. Även framtida forskning kring styrmedel, t.ex. energitjänster, för ökad energieffektivitet i industrisektorn förordas. Resultat från Industrikonsortiets avhandlingar visar att processintegrationsverktyget pinchanalys kan kombineras med optimeringsverktyg (i detta fall MIND) vid analys av industriella energisystem. Denna metodkombination ger intressanta resultat varför fortsatt forskning förordas kring kombinationer av olika processintegrationsmetoder. I flertalet avhandlingar har företagsdata använts som indata vid exempelvis modellering och processintegrationsstudier. Detta har accentuerat behovet av ett standardiserat protokoll vid insamling av företagsdata. Ett sådant protokoll kan öka reliabiliteten på indata och förslagsvis användas vid fallstudier.Avslutningsvis kan konstateras att trots närmare 20 års tvärvetenskaplig forskning mellan samhällsvetare och teknikvetenskaperna finns det fortfarande mycket mer att beforska och utveckla.
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6.
  • Alvfors, Per, et al. (författare)
  • Modelling of the simultaneous calcination, sintering and sulphation of limestone and dolomite
  • 1992
  • Ingår i: Chemical Engineering Science. - 0009-2509 .- 1873-4405. ; 47:8, s. 1903-1912
  • Tidskriftsartikel (refereegranskat)abstract
    • The partially sintered spheres model, describing the sulphation of a sorbent particle consisting of CaO and inert content, is incorporated in a model taking into account the calcination of the limestone or dolomite and the sintering of the nascent oxide resulting from the calcination. The model is applicable, for example, to the sulphation of limestone or dolomite when injected into the furnace of a pulverized coal-fired boiler. The simulations show a temperature optimum in the calcium conversion. Increased calcium conversion is found when inert material is present. Satisfactory experimental verifications of the model are shown.
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7.
  • Alvfors, Per, et al. (författare)
  • Modelling of the sulphation of calcined limestone and dolomite—a gas-solid reaction with structural changes in the presence of inert solids
  • 1988
  • Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 43:5, s. 1183-1193
  • Tidskriftsartikel (refereegranskat)abstract
    • The partially sintered spheres model is further developed to account for the influence of inert material present in the solid reactant. This model is applicable, for example, to the sulphation of CaO with a variable amount of inert material. An example is the reaction between calcined dolomite, CaO·MgO, and SO2, when used as an SO2 sorbent in a boiler furnace. The results show that the rate of reaction increases and the active part of the sorbent reaches a higher degree of conversion when inert material is present.
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8.
  • Alvfors, Per, 1954-, et al. (författare)
  • Research and development challenges for Swedish biofuel actors – three illustrative examples : Improvement potential discussed in the context of Well-to-Tank analyses
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use. Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier.
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9.
  • Alvfors, Per, et al. (författare)
  • Research and development challenges for Swedish biofuel actors – three illustrative examples
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Currently biofuels have strong political support, both in the EU and Sweden. The EU has, for example, set a target for the use of renewable fuels in the transportation sector stating that all EU member states should use 10% renewable fuels for transport by 2020. Fulfilling this ambition will lead to an enormous market for biofuels during the coming decade. To avoid increasing production of biofuels based on agriculture crops that require considerable use of arable area, focus is now to move towards more advanced second generation (2G) biofuels that can be produced from biomass feedstocks associated with a more efficient land use.Climate benefits and greenhouse gas (GHG) balances are aspects often discussed in conjunction with sustainability and biofuels. The total GHG emissions associated with production and usage of biofuels depend on the entire fuel production chain, mainly the agriculture or forestry feedstock systems and the manufacturing process. To compare different biofuel production pathways it is essential to conduct an environmental assessment using the well-to-tank (WTT) analysis methodology. In Sweden the conditions for biomass production are favourable and we have promising second generation biofuels technologies that are currently in the demonstration phase. In this study we have chosen to focus on cellulose based ethanol, methane from gasification of solid wood as well as DME from gasification of black liquor, with the purpose of identifying research and development potentials that may result in improvements in the WTT emission values. The main objective of this study is thus to identify research and development challenges for Swedish biofuel actors based on literature studies as well as discussions with the the researchers themselves. We have also discussed improvement potentials for the agriculture and forestry part of the WTT chain. The aim of this study is to, in the context of WTT analyses, (i) increase knowledge about the complexity of biofuel production, (ii) identify and discuss improvement potentials, regarding energy efficiency and GHG emissions, for three biofuel production cases, as well as (iii) identify and discuss improvement potentials regarding biomass supply, including agriculture/forestry. The scope of the study is limited to discussing the technologies, system aspects and climate impacts associated with the production stage. Aspects such as the influence on biodiversity and other environmental and social parameters fall beyond the scope of this study. We find that improvement potentials for emissions reductions within the agriculture/forestry part of the WTT chain include changing the use of diesel to low-CO2-emitting fuels, changing to more fuel-efficient tractors, more efficient cultivation and manufacture of fertilizers (commercial nitrogen fertilizer can be produced in plants which have nitrous oxide gas cleaning) as well as improved fertilization strategies (more precise nitrogen application during the cropping season). Furthermore, the cultivation of annual feedstock crops could be avoided on land rich in carbon, such as peat soils and new agriculture systems could be introduced that lower the demand for ploughing and harrowing. Other options for improving the WTT emission values includes introducing new types of crops, such as wheat with higher content of starch or willow with a higher content of cellulose. From the case study on lignocellulosic ethanol we find that 2G ethanol, with co-production of biogas, electricity, heat and/or wood pellet, has a promising role to play in the development of sustainable biofuel production systems. Depending on available raw materials, heat sinks, demand for biogas as vehicle fuel and existing 1G ethanol plants suitable for integration, 2G ethanol production systems may be designed differently to optimize the economic conditions and maximize profitability. However, the complexity connected to the development of the most optimal production systems require improved knowledge and involvement of several actors from different competence areas, such as chemical and biochemical engineering, process design and integration and energy and environmental systems analysis, which may be a potential barrier. Three important results from the lignocellulosic ethanol study are: (i) the production systems could be far more complex and intelligently designed than previous studies show, (ii) the potential improvements consist of a large number of combinations of process integration options wich partly depends on specific local conditions, (iii) the environmental performance of individual systems may vary significantly due to systems design and local conditons.From the case study on gasification of solid biomass for the production of biomethane we find that one of the main advantages of this technology is its high efficiency in respect to converting biomass into fuels for transport. For future research we see a need for improvements within the gas up-grading section, including gas cleaning and gas conditioning, to obtain a more efficient process. A major challenge is to remove the tar before the methanation reaction. Three important results from the biomethane study are: (i) it is important not to crack the methane already produced in the syngas, which indicates a need for improved catalysts for selective tar cracking, (ii) there is a need for new gas separation techniques to facilitate the use of air oxidation agent instead of oxygen in the gasifier, and (iii) there is a need for testing the integrated process under realistic conditions, both at atmospheric and pressurized conditions. From the case study on black liquor gasification for the production of DME we find that the process has many advantages compared to other biofuel production options, such as the fact that black liquor is already partially processed and exists in a pumpable, liquid form, and that the process is pressurised and tightly integrated with the pulp mill, which enhances fuel production efficiency. However, to achieve commercial status, some challenges still remain, such as demonstrating that materials and plant equipment meet the high availability required when scaling up to industrial size in the pulp mill, and also proving that the plant can operate according to calculated heat and material balances. Three important results from the DME study are: (i) that modern chemical pulp mills, having a potential surplus of energy, could become important suppliers of renewable fuels for transport, (ii) there is a need to demonstrate that renewable DME/methanol will be proven to function in large scale, and (iii) there is still potential for technology improvements and enhanced energy integration. Although quantitative improvement potentials are given in the three biofuel production cases, it is not obvious how these potentials would affect WTT values, since the biofuel production processes are complex and changing one parameter impacts other parameters. The improvement potentials are therefore discussed qualitatively. From the entire study we have come to agree on the following common conclusions: (i) research and development in Sweden within the three studied 2G biofuel production technologies is extensive, (ii) in general, the processes, within the three cases, work well at pilot and demonstration scale and are now in a phase to be proven in large scale, (iii) there is still room for improvement although some processes have been known for decades, (iv) the biofuel production processes are complex and site specific and process improvements need to be seen and judged from a broad systems perspective (both within the production plant as well as in the entire well-to-tank perspective), and (v) the three studied biofuel production systems are complementary technologies. Futher, the process of conducting this study is worth mentioning as a result itself, i.e. that many different actors within the field have proven their ability and willingness to contribute to a common report, and that the cooperation climate was very positive and bodes well for possible future collaboration within the framework of the f3 center. Finally, judging from the political ambitions it is clear that the demand for renewable fuels will significantly increase during the coming decade. This will most likely result in opportunities for a range of biofuel options. The studied biofuel options all represent 2G biofuels and they can all be part of the solution to meet the increased renewable fuel demand.
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10.
  • Chutichai, Bhawasut, et al. (författare)
  • Design of an integrated biomass gasification and proton exchange membrane fuel cell system under self-sustainable conditions : Process modification and heat-exchanger network synthesis
  • 2017
  • Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 42:1, s. 448-458
  • Tidskriftsartikel (refereegranskat)abstract
    • The design and analysis of an integrated biomass gasification and PEMFC system to generate heat and power demand for residential applications are presented in this study. Two biomass gasification configurations using sawdust as a feedstock are considered: air steam biomass gasification (AS-BG-PEMFC) and steam-only biomass gasification (SO-BG-PEMFC). The biomass processing consists of a biomass gasification which is used to produce H-2-rich gas (syngas), followed by high- and low-temperature shift reactors and a preferential oxidation reactor. Pinch analysis is performed to evaluate and design a heat-exchanger network in the two biomass gasification systems. The remaining useful heat is recovered and employed for a reactant preparation step and for a heating utility system in a household. The simulation results indicate that the SO-BG-PEMFC generates syngas with a greater H2 content than the AS-BG-PEMFC, resulting in higher fuel processor and electric efficiencies. However, the AS-BG-PEMFC provides a higher thermal efficiency because a high temperature gaseous product is obtained, and more energy is thereby recovered to the system. The total heat and power efficiencies of the AS-BG-PEMFC and the SO-BG-PEMFC are 83% and 70%, respectively. The Sankey diagram of energy flows reveals that the performance improvement depends entirely on the utilization of useful energy in the exhaust gas.
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11.
  • Folkesson, Anders, et al. (författare)
  • Real life testing of a hybrid PEM fuel cell bus
  • 2003
  • Ingår i: Journal of Power Sources. - 0378-7753 .- 1873-2755. ; 118:1-2, s. 349-357
  • Tidskriftsartikel (refereegranskat)abstract
    • Fuel cells produce low quantities of local emissions, if any, and are therefore one of the most promising alternatives to internal combustion engines as the main power source in future vehicles. It is likely that urban buses will be among the first commercial applications for fuel cells in vehicles. This is due to the fact that urban buses are highly visible for the public, they contribute significantly to air pollution in urban areas, they have small limitations in weight and volume and fuelling is handled via a centralised infrastructure. Results and experiences from real life measurements of energy flows in a Scania Hybrid PEM Fuel Cell Concept Bus are presented in this paper. The tests consist of measurements during several standard duty cycles. The efficiency of the fuel cell system and of the complete vehicle are presented and discussed. The net efficiency of the fuel cell system was approximately 40% and the fuel consumption of the concept bus is between 42 and 48% lower compared to a standard Scania bus. Energy recovery by regenerative braking saves up 28% energy. Bus subsystems such as the pneumatic system for door opening, suspension and brakes, the hydraulic power steering, the 24 V grid, the water pump and the cooling fans consume approximately 7% of the energy in the fuel input or 17% of the net power output from the fuel cell system. The bus was built by a number of companies in a project partly financed by the European Commission's Joule programme. The comprehensive testing is partly financed by the Swedish programme "Den Grona Bilen" (The Green Car). A 50 kW(el) fuel cell system is the power source and a high voltage battery pack works as an energy buffer and power booster. The fuel, compressed hydrogen, is stored in two high-pressure stainless steel vessels mounted on the roof of the bus. The bus has a series hybrid electric driveline with wheel hub motors with a maximum power of 100 kW. Hybrid Fuel Cell Buses have a big potential, but there are still many issues to consider prior to full-scale commercialisation of the technology. These are related to durability, lifetime, costs, vehicle and system optimisation and subsystem design. A very important factor is to implement an automotive design policy in the design and construction of all components, both in the propulsion system as well as in the subsystems.
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12.
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13.
  • Folkesson, Anders, 1976- (författare)
  • Towards sustainable urban transportation : Test, demonstration and development of fuel cell and hybrid-electric buses
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Several aspects make today’s transport system non-sustainable: • Production, transport and combustion of fossil fuels lead to global and local environmental problems. • Oil dependency in the transport sector may lead to economical and political instability. • Air pollution, noise, congestion and land-use may jeopardise public health and quality of life, especially in urban areas. In a sustainable urban transport system most trips are made with public transport because high convenience and comfort makes travelling with public transport attractive. In terms of emissions, including noise, the vehicles are environmentally sustainable, locally as well as globally. Vehicles are energy-efficient and the primary energy stems from renewable sources. Costs are reasonable for all involved, from passengers, bus operators and transport authorities to vehicle manufacturers. The system is thus commercially viable on its own merits. This thesis presents the results from three projects involving different concept buses, all with different powertrains. The first two projects included technical evaluations, including tests, of two different fuel cell buses. The third project focussed on development of a series hybrid-bus with internal combustion engine intended for production around 2010. The research on the fuel cell buses included evaluations of the energy efficiency improvement potential using energy mapping and vehicle simulations. Attitudes to hydrogen fuel cell buses among passengers, bus drivers and bus operators were investigated. Safety aspects of hydrogen as a vehicle fuel were analysed and the use of hydrogen compared to electrical energy storage were also investigated. One main conclusion is that a city bus should be considered as one energy system, because auxiliaries contribute largely to the energy use. Focussing only on the powertrain is not sufficient. The importance of mitigating losses far down an energy conversion chain is emphasised. The Scania hybrid fuel cell bus showed the long-term potential of fuel cells, advanced auxiliaries and hybrid-electric powertrains, but technologies applied in that bus are not yet viable in terms of cost or robustness over the service life of a bus. Results from the EU-project CUTE show that hydrogen fuelled fuel cell buses are viable for real-life operation. Successful operation and public acceptance show that focus on robustness and cost in vehicle design were key success factors, despite the resulting poor fuel economy. Hybrid-electric powertrains are feasible in stop-and-go city operation. Fuel consumption can be reduced, comfort improved, noise lowered and the main power source downsized and operated less dynamically. The potential for design improvements due to flexible component packaging is implemented in the Scania hybrid concept bus. This bus and the framework for its hybrid management system are discussed in this thesis. The development of buses for a more sustainable urban transport should be made in small steps to secure technical and economical realism, which both are needed to guarantee commercialisation and volume of production. This is needed for alternative products to have a significant influence. Hybrid buses with internal combustion engines running on renewable fuel is tomorrow’s technology, which paves the way for plug-in hybrid, battery electric and fuel cell hybrid vehicles the day after tomorrow.
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14.
  • Guan, Tingting, et al. (författare)
  • An overview of biomass-fuelled proton exchange membrane fuel cell (PEMFC) systems
  • 2015
  • Ingår i: CLEAN, EFFICIENT AND AFFORDABLE ENERGY FOR A SUSTAINABLE FUTURE. - : Elsevier. ; , s. 2003-2008
  • Konferensbidrag (refereegranskat)abstract
    • PEMFC fuelled by biomass-derived hydrogen is an efficient and sustainable energy system for small-scale residential applications. Gasification and anaerobic digestion combined with steam reforming are seen as the most suitable conversion processes for hydrogen production. Since the biomass-derived hydrogen contains many kinds of contaminants including CO, CO2, H2S, NH3 and N-2, extensive work has been done on the mechanism and mitigation methods for their poisoning the PEMFC. Although the biomass-fuelled PEMFC systems have been tested in several experiments and checked through simulation work for different perspectives, further research and demonstration work are required to improve the system efficiency and reliability. (C) 2015 The Authors. Published by Elsevier Ltd.
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15.
  • Guan, Tingting (författare)
  • Biomass-fuelled PEM FuelCell systems for small andmedium-sized enterprises
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Biomass-fuelled proton exchange membrane fuel cells (PEMFCs) offer asolution for replacing fossil fuel for hydrogen production. Through using thebiomass-derived hydrogen as fuel, PEMFCs may become an efficient andsustainable energy system for small and medium-sized enterprises. The aim ofthis thesis is to evaluate the performance and potential applications of biomassfuelledPEMFC systems which are designed to convert biomass to electricity andheat. Biomass-fuelled PEMFC systems are simulated by Aspen plus based ondata collected from experiments and literature.The impact of the quality of the hydrogen-rich gas, anode stoichiometry, CH4content in the biogas and CH4 conversion rate on the performance of the PEMFCis investigated. Also, pinch technology is used to optimize the heat exchangernetwork to improve the power generation and thermal efficiency.For liquid and solid biomass, anaerobic digestion (AD) and gasification (GF),respectively, are relatively viable and developed conversion technologies. ForAD-PEMFC, a steam reformer is also needed to convert biogas to hydrogen-richgas. For 100 kWe generation, the GF-PEMFC system yields a good technicalperformance with 20 % electrical efficiency and 57 % thermal efficiency,whereas the AD-PEMFC system only has 9 % electrical efficiency and 13 %thermal efficiency. This low efficiency is due to the low efficiency of theanaerobic digester (AD) and the high internal heat consumption of the AD andthe steam reformer (SR). For the environmental aspects, the GF-PEMFC systemhas a high CO2 emissions offset factor and the AD-PEMFC system has anefficient land-use.The applications of the biomass-fuelled PEMFC systems are investigated on adairy farm and an olive oil plant. For the dairy farm, manure is used as feedstockto generate biogas through anaerobic digestion. A PEMFC qualified for 40 %electrical efficiency may generate 360 MWh electricity and 680 MWh heat peryear to make a dairy farm with 300 milked cows self-sufficient in a sustainableway. A PEMFC-CHP system designed for an olive oil plant generating annual 50000 m3 solid olive mill waste (SOMW) and 9 000 m3 olive mill waste water(OMW) is simulated based on experimental data from the Biogas2PEM-FCproject1. After the optimization of the heat exchanger network, the PEMFC-CHP system can generate 194 kW electricity which corresponds to 62 % of the totalelectricity demand of the olive oil plant.The economic performance of the PEMFC and biogas-fuelled PEMFC areassessed roughly including capital, operation & maintenance (O&M) costs of thebiogas plant and the PEMFC-CHP, the cost of heat and electricity, and the valueof the digestate as fertilizer.
  •  
16.
  • Guan, Tingting, et al. (författare)
  • Biomass-fuelled PEMFC systems : Evaluation of two conversion pathsrelevant for different raw materials
  • 2015
  • Ingår i: Energy Conversion and Management. - : Pergamon-Elsevier. - 0196-8904 .- 1879-2227. ; 106, s. 1183-1191
  • Tidskriftsartikel (refereegranskat)abstract
    • Biomass-fuelled polymer electrolyte membrane fuel cells (PEMFCs) offer a solution for replacing fossilfuel with hydrogen production. This paper uses simulation methods for investigating biomass-fuelledPEMFCs for different raw materials and conversion paths. For liquid and solid biomass, anaerobic diges-tion (AD) and gasification (GF), respectively, are relatively viable and developed conversion technologies.Therefore, the AD-PEMFC system and the GF-PEMFC system are simulated for residential applications inorder to evaluate the performance of the biomass-fuelled PEMFC systems. The results of the evaluationshow that renewable hydrogen-rich gas from manure or forest residues is usable for the PEMFCs andmakes the fuel cell stack work in a stable manner. For 100 kWe generation, the GF-PEMFC system yieldsan excellent technical performance with a 20% electric efficiency and 57% thermal efficiency, whereas theAD-PEMFC system only has an 9% electric efficiency and 13% thermal efficiency due to the low efficiencyof the anaerobic digester (AD) and the high internal heat consumption of the AD and the steam reformer(SR). Additionally, in this study, the environmental performances of the AD-PEMFC and the GF-PEMFC interms of CO2emission offset and land-use efficiency are discussed.
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17.
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18.
  • Guan, Tingting, et al. (författare)
  • Investigation of the prospect of energy self-sufficiency and technical performance of an integrated PEMFC (proton exchange membrane fuel cell), dairy farm and biogas plant system
  • 2014
  • Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 130, s. 685-691
  • Tidskriftsartikel (refereegranskat)abstract
    • A PEMFC fuelled with hydrogen is known for its high efficiency and low local emissions. However, the generation of hydrogen is always a controversial issue for the application of the PEMFC due to the use of fossil fuel and the possible carbon dioxide emissions. Presently, the PEMFC-CHP fed with renewable fuels, such as biogas, appears to be the most attractive energy converter-fuel combination. In this paper, an integrated PEMFC-CHP, a dairy farm and a biogas plant are studied. A PEMFC-CHP fed with reformate gas from the biogas plant generates electricity and heat to a dairy farm and a biogas plant, while the dairy farm delivers wet manure to the biogas plant as the feedstock for biogas production. This integrated system has been modelled for steady-state conditions by using Aspen Plus (R). The results indicate that the wet manure production of a dairy farm with 300 milked cows can support a biogas plant to give 1280 MW h of biogas annually. Based on the biogas production, a PEMFC-CHP with a stack having an electrical efficiency of 40% generates 360 MW h electricity and 680 MW h heat per year, which is enough to cover the energy demand of the whole system while the total efficiency of the PEMFC-CHP system is 82%. The integrated PEMFC-CHP, dairy farm and biogas plant could make the dairy farm and the biogas plant self-sufficient in a sustainable way provided the PEMFC-CHP has the electrical efficiency stated above. The effect of the methane conversion rate and the biogas composition on the system performance is discussed. Moreover, compared with the coal-fired CUP plant, the potentially avoided fossil fuel consumption and CO2 emissions of this self-sufficient system are also calculated.
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19.
  • Guan, Tingting, et al. (författare)
  • The economic performance of an integrated biogas plant and Proton Exchange Membrane Fuel Cell Combined Heat and Power system (PEMFC-CHP) in Sweden
  • 2014
  • Konferensbidrag (refereegranskat)abstract
    • A Proton Exchange Membrane Fuel Cell Combined Heat and Power system (PEMFC-CHP) fuelled by the hydrogen-rich gas reformed from biogas may be seen as an efficient and sustainable technology. This system can provide electrical and thermal energy dynamically to residential applications. In this study, an assessment of the economic performance of an integrated biogas plant and PEMFC-CHP for Swedish electricity and heat prices is presented. The economic factors considered are the capital and operation & maintenance (O&M) costs of the biogas plant and the PEMFC-CHP, the price of heat and electricity, and the value of the digestate as fertilizer. The analysis includes two cases: 1) both biogas plant and PEMFC-CHP are located on the farm. The farm sells the electricity and heat to the power grid and district heating system, respectively; 2) the PEMFC-CHP is located in a centralized-biogas plant, not on the farm. The manure is transported from farms to the plant. The plant also sells the electricity and heat to the power grid and district heating system. The results show that the farm-based and the centralized biogas plant have almost the same biogas production cost. The electricity cost of today, expected for 2020, and for the break-even of this integrated system are 530, 305 and 197 €/MWh, respectively. With the current trend of the fuel cell industry development, this break-even price may be reached in the near future.
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20.
  • Görling, Martin, 1984-, et al. (författare)
  • Bio-methane via fast pyrolysis of biomass
  • 2013
  • Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 112:SI, s. 440-447
  • Tidskriftsartikel (refereegranskat)abstract
    • Bio-methane, a renewable vehicle fuel, is today produced by anaerobic digestion and a 2nd generation production route via gasification is under development. This paper proposes a poly-generation plant that produces bio-methane, bio-char and heat via fast pyrolysis of biomass. The energy and material flows for the fuel synthesis are calculated by process simulation in Aspen Plus®. The production of bio-methane and bio-char amounts to 15.5. MW and 3.7. MW, when the total inputs are 23. MW raw biomass and 1.39. MW electricity respectively (HHV basis). The results indicate an overall efficiency of 84% including high-temperature heat and the biomass to bio-methane yield amounts to 83% after allocation of the biomass input to the final products (HHV basis). The overall energy efficiency is higher for the suggested plant than for the gasification production route and is therefore a competitive route for bio-methane production.
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21.
  • Haraldsson, Kristina, et al. (författare)
  • A First Report on the Attitude towards Hydrogen Fuel Cell Buses in Stockholm
  • 2006
  • Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 31:3, s. 317-325
  • Tidskriftsartikel (refereegranskat)abstract
    • Surveys of the attitude towards hydrogen fuel cell buses among passengers and bus drivers were performed in Stockholm during the autumn of 2004. Another field survey of the attitude of the fuel cell bus passengers is planned towards the end of the CUTE Stockholm project, i.e. during the autumn of 2005.The main results from the surveys are:People are generally positive towards fuel cell buses and feel safe with the technology.Newspapers and bus stops are where most people get information about the buses.The passengers, furthermost those above the age of 40, desire more information about fuel cells and hydrogen.The drivers are generally positive to the fuel cell bus project.Although the environment is rated as an important factor, 64% of the bus passengers were not willing to pay a higher fee if more fuel cell buses were to be used.
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22.
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23.
  • Haraldsson, Kristina, et al. (författare)
  • Effects of Ambient Conditions on Fuel Cell Vehicle Performance
  • 2005
  • Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 145:2, s. 298-306
  • Tidskriftsartikel (refereegranskat)abstract
    • Ambient conditions have considerable impact on the performance of fuel cell hybrid vehicles. Here, the vehicle fuel consumption, the air compressor power demand, the water management system and the heat loads of a fuel cell hybrid sport utility vehicle (SUV) were studied. The simulation results show that the vehicle fuel consumption increases with 10% when the altitude increases from 0 m up to 3000 m to 4.1 L gasoline equivalents/100 km over the New European Drive Cycle (NEDC). The increase is 19% on the more power demanding highway US06 cycle. The air compressor is the major contributor to this fuel consumption increase. Its load-following strategy makes its power demand increase with increasing altitude. Almost 40% of the net power output of the fuel cell system is consumed by the air compressor at the altitude of 3000 m with this load-following strategy and is thus more apparent in the high-power US06 cycle.Changes in ambient air temperature and relative humidity effect on the fuel cell system performance in terms of the water management rather in vehicle fuel consumption. Ambient air temperature and relative humidity have some impact on the vehicle performance mostly seen in the heat and water management of the fuel cell system. While the heat loads of the fuel cell system components vary significantly with increasing ambient temperature, the relative humidity did not have a great impact on the water balance. Overall, dimensioning the compressor and other system components to meet the fuel cell system requirements at the minimum and maximum expected ambient temperatures, in this case 5 and 40 degrees C, and high altitude, while simultaneously choosing a correct control strategy are important parameters for efficient vehicle power train management.
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24.
  • Haraldsson, Kristina, et al. (författare)
  • Fuel Cell Buses in the Stockholm CUTE Project : First Experiences from a Climate Perspective
  • 2005
  • Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 145:2, s. 620-631
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper aims to share the first experiences and results from the operation of fuel cell buses in Stockholm within the Clean Urban Transport for Europe (CUTE) project. The project encompasses implementation and evaluation of both a hydrogen fuel infrastructure and fuel cell vehicles in nine participating European cities. In total, 27 fuel cell buses, 3 in each city, are in revenue service for a period of 2 years.The availability of the fuel cell buses has been better than expected, about 85% and initially high fuel consumption has been reduced to approximately 2.2 kg H-2/10 km corresponding to 7.51 diesel equivalents/10 km. Although no major breakdowns have occurred so far, a few cold climate-related issues did arise during the winter months in Stockholm.
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25.
  • Haraldsson, Kristina, 1970- (författare)
  • On direct hydrogen fuel cell vehicles : modelling and demonstration
  • 2005
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, direct hydrogen Proton Exchange Membrane (PEM) fuel cell systems in vehicles are investigated through modelling, field tests and public acceptance surveys. A computer model of a 50 kW PEM fuel cell system was developed. The fuel cell system efficiency is approximately 50% between 10 and 45% of the rated power. The fuel cell auxiliary system, e.g. compressor and pumps, was shown to clearly affect the overall fuel cell system electrical efficiency. Two hydrogen on-board storage options, compressed and cryogenic hydrogen, were modelled for the above-mentioned system. Results show that the release of compressed gaseous hydrogen needs approximately 1 kW of heat, which can be managed internally with heat from the fuel cell stack. In the case of cryogenic hydrogen, the estimated heat demand of 13 kW requires an extra heat source. A phase change based (PCM) thermal management solution to keep a 50 kW PEM fuel cell stack warm during dormancy in a cold climate (-20 °C) was investigated through simulation and experiments. It was shown that a combination of PCM (salt hydrate or paraffin wax) and vacuum insulation materials was able to keep a fuel cell stack from freezing for about three days. This is a simple and potentially inexpensive solution, although development on issues such as weight, volume and encapsulation materials is needed Two different vehicle platforms, fuel cell vehicles and fuel cell hybrid vehicles, were used to study the fuel consumption and the air, water and heat management of the fuel cell system under varying operating conditions, e.g. duty cycles and ambient conditions. For a compact vehicle, with a 50 kW fuel cell system, the fuel consumption was significantly reduced, ~ 50 %, compared to a gasoline-fuelled vehicle of similar size. A bus with 200 kW fuel cell system was studied and compared to a diesel bus of comparable size. The fuel consumption of the fuel cell bus displayed a reduction of 33-37 %. The performance of a fuel cell hybrid vehicle, i.e. a 50 kW fuel cell system and a 12 Ah power-assist battery pack in series configuration, was studied. The simulation results show that the vehicle fuel consumption increases with 10-19 % when the altitude increases from 0 to 3000 m. As expected, the air compressor with its load-following strategy was found to be the main parasitic power (~ 40 % of the fuel cell system net power output at the altitude of 3000 m). Ambient air temperature and relative humidity affect mostly the fuel cell system heat management but also its water balance. In designing the system, factors such as control strategy, duty cycles and ambient conditions need to taken into account. An evaluation of the performance and maintenance of three fuel cell buses in operation in Stockholm in the demonstration project Clean Urban Transport for Europe (CUTE) was performed. The availability of the buses was high, over 85 % during the summer months and even higher availability during the fall of 2004. Cold climate-caused failures, totalling 9 % of all fuel cell propulsion system failures, did not involve the fuel cell stacks but the auxiliary system. The fuel consumption was however rather high at 7.5 L diesel equivalents/10km (per July 2004). This is thought to be, to some extent, due to the robust but not energy-optimized powertrain of the buses. Hybridization in future design may have beneficial effects on the fuel consumption. Surveys towards hydrogen and fuel cell technology of more than 500 fuel cell bus passengers on route 66 and 23 fuel cell bus drivers in Stockholm were performed. The passengers were in general positive towards fuel cell buses and felt safe with the technology. Newspapers and bus stops were the main sources of information on the fuel cell bus project, but more information was wanted. Safety, punctuality and frequency were rated as the most important factors in the choice of public transportation means. The environment was also rated as an important factor. More than half of the bus passengers were nevertheless unwilling to pay a higher fee for introducing more fuel cell buses in Stockholm’s public transportation. The drivers were positive to the fuel cell bus project, stating that the fuel cell buses were better than diesel buses with respect to pollutant emissions from the exhausts, smell and general passenger comfort. Also, driving experience, acceleration and general comfort for the driver were reported to be better than or similar to those of a conventional bus.
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26.
  • Hedström, Lars, 1977-, et al. (författare)
  • Description and modelling of the solar–hydrogen–biogas-fuel cell system in GlashusEtt
  • 2004
  • Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; :131, s. 340-350
  • Tidskriftsartikel (refereegranskat)abstract
    • The need to reduce pollutant emissions and utilise the world's available energy resources more efficiently has led to increased attention towards e.g. fuel cells, but also to other alternative energy solutions. In order to further understand and evaluate the prerequisites for sustainable and energy-saving systems, ABB and Fortum have equipped an environmental information centre, located in Hammarby Sjostad, Stockholm, Sweden, with an alternative energy system. The system is being used to demonstrate and evaluate how a system based on fuel cells and solar cells can function as a complement to existing electricity and heat production. The stationary energy system is situated on the top level of a three-floor glass building and is open to the public. The alternative energy system consists of a fuel cell system, a photovoltaic (PV) cell array, an electrolyser, hydrogen storage tanks, a biogas burner, dc/ac inverters, heat exchangers and an accumulator tank. The fuel cell system includes a reformer and a polymer electrolyte fuel cell (PEFC) with a maximum rated electrical output of 4 kW(el) and a maximum thermal output of 6.5 kW(th). The fuel cell stack can be operated with reformed biogas, or directly using hydrogen produced by the electrolyser. The cell stack in the electrolyser consists of proton exchange membrane (PEM) cells. To evaluate different automatic control strategies for the system, a simplified dynamic model has been developed in MATLAB Simulink. The model based on measurement data taken from the actual system. The evaluation is based on demand curves, investment costs, electricity prices and irradiation. Evaluation criteria included in the model are electrical and total efficiencies as well as economic parameters.
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27.
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28.
  • Hedström, Lars (författare)
  • Fuel Cells and Biogas
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis concerns biogas-operated fuel cells. Fuel cell technology may contribute to more efficient energy use, reduce emissions and also perhaps revolutionize current energy systems. The technology is, however, still immature and has not yet been implemented as dominant in any application or niche market. Research and development is currently being carried out to investigate whether fuel cells can live up to their full potential and to further advance the technology. The research of thesis contributes by exploring the potential of using fuel cells as energy converters of biogas to electricity. The work includes results from four different experimental test facilities and concerns experiments performed at cell, stack and fuel cell system levels. The studies on cell and stack level have focused on the influence of CO, CO2 and air bleed on the current distribution during transient operation. The dynamic response has been evaluated on a single cell, a segmented cell and at stack level. Two fuel cell systems, a 4 kW PEFC system and a 5 kW SOFC system have been operated on upgraded biogas. A significant outcome is that the possibility of operating both PEFCs and SOFCs on biogas has been established. No interruptions or rapid performance loss could be associated with the upgraded biogas during operation. From the studies at cell and stack level, it is clear that CO causes significant changes in the current distribution in a PEFC; air bleed may recover the uneven current distribution and also the drop in cell voltage due to CO and CO2 poisoning. The recovery of cell performance during air bleed occurs evenly over the electrode surface even when the O2 partial pressure is far too low to fully recover the CO poisoning. The O2 supplied to the anode reacts on the anode catalyst and no O2 was measured at the cell outlet for air bleed levels up to 5 %. Reformed biogas and other gases with high CO2 content are thus, from dilution and CO-poisoning perspectives, suitable for PEFC systems. The present work has enhanced our understanding of biogas-operated fuel cells and will serve as basis for future studies.
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29.
  • Hedström, Lars, et al. (författare)
  • Key factors in planning a sustainable energy future including hydrogen and fuel cells
  • 2006
  • Ingår i: Bulletin of Science, Technology & Society. - : SAGE Publications. - 0270-4676 .- 1552-4183. ; 26:4, s. 264-277
  • Tidskriftsartikel (refereegranskat)abstract
    • In this article, a number of future energy visions, especiallythose basing the energy systems on hydrogen, are discussed.Some often missing comparisons between alternatives, from asustainability perspective, are identified and then performedfor energy storage, energy transportation, and energy use invehicles. It is shown that it is important to be aware of thelosses implied by production, packaging, distribution, storage,and end-use of hydrogen when suggesting a "hydrogen economy."It is also shown that for stationary electric energy storage,fuel cell electrolyzers could be feasible. Zero-tailpipeemissionvehicles are compared. The battery electric vehicle has thehighest electrical efficiency, but other requirements implythat plug-in hybrids or fuel cell hybrids might be a betteroption in some types of vehicles. Finally, a simplified exampleis applied to the overall results and used to discuss the needsand nature of an energy system based on intermittent energysources. 
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30.
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31.
  • Johansson, Kristina, et al. (författare)
  • The Effect of Drive Cycles on the Performance of a PEM Fuel Cell System for Automotive Applications
  • 2001
  • Ingår i: Proceedings, ATTCE 2001-Automotive and Transport Technology Congress and Exhibition. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. ; , s. 417-426
  • Konferensbidrag (refereegranskat)abstract
    • The purpose of this system study was to compare the performance and fuel consumption of a pure fuel cell vehicle ( i.e. with no battery included) with an internal combustion engine (ICE) vehicle of similar weight in different drive cycles. Both light and heavy duty vehicles are studied. For light duty vehicles, the New European drive cycle, NEDC [70/220/EEC], the FTP75 [EPA] and a Swedish driving pattern from the city of Lund [ Ericsson, 2000 ] are utilised. The fuel consumption for these drive cycles was compared with ICE vehicles of similar weight, an Ibiza Stella 1.4 (year 2000) from Seat and a Volvo 960 2.5 E sedan (year 1995). For heavy duty vehicles, urban buses in this study, two drive cycles were employed, the synthetic CBD14 and the real bus route 85 from Gothenburg, Sweden. It can be concluded that marked improvements in fuel economy can be achieved for hydrogen-fuelled light and heavy duty vehicles. The fuel consumption of a small fuel cell vehicle was 50% less than the corresponding ICE vehicle in both the NEDC and the FTP75. With proper dimensioning of the system components, e.g. the engine, further reductions in fuel consumption can be achieved. The range of more than 500 km with 5 kg of hydrogen in a 345 bar fuel tank was comparable to an ICE vehicle. If the pressure is raised to 690 bar, a driving range of 600 km could be achieved. As the auxiliary system counteracts the increase in fuel cell efficiency, raising the minimum operating voltage from 0.6 to 0.75 V in a 50 kW fuel cell system, provides only a 5% reduction in fuel consumption. A fuel cell bus operated in the CBD14 and the bus route 85, compared with diesel-fuelled urban bus of similar weight, demonstrates a reduction in fuel consumption of 33 and 37 % respectively.
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32.
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33.
  • Larsson, Mårten, et al. (författare)
  • Bio-methane upgrading of pyrolysis gas from charcoal production
  • 2013
  • Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 3, s. 66-73
  • Tidskriftsartikel (refereegranskat)abstract
    • This article presents a novel route for bio-methane synthesis utilizing pyrolysis gas from charcoal production. It is a retrofit option that may increase overall process efficiency in charcoal production while adding a valuable product. The pyrolysis gas from charcoal production can be used for bio-methane production instead of burning, while the required heat for the charcoal production is supplied by additional biomass. The aim is to evaluate the energy efficiency of bio-methane upgrading from two types of charcoal plants, with and without recovery of liquid by-products (bio-oil). Aspen simulations and calculations of the energy and mass balances are used to analyse the system. The yield of bio-methane compared to the import of additional biomass is estimated to be 81% and 85% (biomass to bio-methane yield) for the syngas case and the pyrolysis vapour case, respectively. When the biomass necessary to produce the needed electricity (assuming ηel = 33%) is included, the yields amount to 65% and 73%. The results show that the suggested process is a competitive production route for methane from lignocellulosic biomass.
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34.
  • Larsson, M., et al. (författare)
  • Energy system analysis of the implications of hydrogen fuel cell vehicles in the Swedish road transport system
  • 2014
  • Ingår i: 20th World Hydrogen Energy Conference, WHEC 2014. - 9780000000002 ; , s. 2084-2091
  • Konferensbidrag (refereegranskat)abstract
    • The focus on pathways to reduce the use of fossil fuels in the transport sector is intense in many countries worldwide. Considering that biofuels have a limited technical production potential and that battery electric vehicles suffer from technical limitations that put constraints on their general use in the transport sector, hydrogen-fuelled fuel cell vehicles may become a feasible alternative. Introduction of hydrogen in the transport sector will also transform the energy sector and create new interactions. The aim of this paper is to analyse the consequences and feasibility of such an integration in Sweden. Different pathways for hydrogen, electricity and methane to the transport sector are compared with regard to system energy efficiency. The efficiencies for hydrogen and electricity are used for estimating the energy resources needed for hydrogen production and electric vehicles for a future Swedish transport sector based on renewable fuels. The analysis reveal that the well to wheel system efficiencies for hydrogen fuel cell vehicles are comparable to those of methane gas vehicles, even when methane gas is the primary energy source. The results further indicate that an increased hydrogen demand may have a less than expected impact on the primary energy supply in Sweden.
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35.
  • Larsson, Mårten, et al. (författare)
  • Energy system analysis of the implications of hydrogen fuel cell vehicles in the Swedish road transport system
  • 2015
  • Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 40:35, s. 11722-11729
  • Tidskriftsartikel (refereegranskat)abstract
    • The focus on pathways to reduce the use of fossil fuels in the transport sector is intense in many countries worldwide. Considering that biofuels have a limited technical production potential and that battery electric vehicles suffer from technical limitations that put constraints on their general use in the transport sector, hydrogen-fuelled fuel cell vehicles may become a feasible alternative. Introduction of hydrogen in the transport sector will also transform the energy sector and create new interactions. The aim of this paper is to analyse the consequences and feasibility of such an integration in Sweden. Different pathways for hydrogen, electricity and methane to the transport sector are compared with regard to system energy efficiency. The well-to-wheel energy efficiencies for hydrogen and electricity are used for estimating the energy resources needed for hydrogen production and electric vehicles for a future Swedish transport sector based on renewable fuels. The analysis reveal that the well-to-wheel system efficiencies for hydrogen fuel cell vehicles are comparable to those of methane gas vehicles, even when biomethane is the energy source. The results further indicate that an increased hydrogen demand may have a less than expected impact on the primary energy supply in Sweden.
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36.
  • Larsson, Mårten, et al. (författare)
  • Synthetic fuels from electricity for the Swedish transport sector : comparison of well to wheel energy efficiencies and costs
  • 2015
  • Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 75, s. 1875-1880
  • Tidskriftsartikel (refereegranskat)abstract
    • Synthetic fuels based on electricity, water, and carbon dioxide (CO2) may be necessary to cover the fuel demand in a sustainable transport sector based on renewable energy sources. The aim of this paper is to compare hydrogen, methane, methanol and diesel produced in this way. The main parameters for the analysis are well to wheel energy efficiency and costs, and the fuels are analysed in a Swedish context. The results indicate that methane and diesel could have the potential to be cost competitive in the near term, at least if common incentivesfor renewable transportation fuels are applied. Moreover, that hydrogen is the best option in terms of well to wheel energy efficiency, and that it in the longer term also may be cost competitive to the other fuels.
  •  
37.
  • Larsson, Mårten, et al. (författare)
  • Techno-economic assessment of anaerobic digestion in a typical Kraft pulp mill to produce biomethane for the road transport sector
  • 2015
  • Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 104, s. 460-467
  • Tidskriftsartikel (refereegranskat)abstract
    • Renewable waste-based fuels may decrease the resource use and environmental impact of the road transport sector; one of the options is biogas produced via anaerobic digestion of waste streams from pulp and paper mills. This paper describes process simulation and economic assessments for two options for integrating anaerobic digestion and production of liquid biogas in a typical Nordic Kraft pulp mill: (1) a high-rate anaerobic reactor in the wastewater treatment, and (2) an external anaerobic stirred tank reactor for the treatment of primary and secondary sludge as well as Kraft evaporator methanol condensate. The results revealed an annual production potential of 26-27 GWh biogas in an average Nordic Kraft pulp mill, which is equivalent to a daily production of 7600 L of diesel in terms of energy, and the production cost was estimated to (sic)0.47-0.82 per litre diesel equivalent, comparable with the Swedish price of (sic)0.68 per litre diesel.However, for the cases with liquid biogas (LBG), a discounted payback period of about 8 years may not be considered profitable by the industry. Other pre-requisites may, however, improve the profitability: a larger mill; production of compressed biogas instead of liquid biogas; or, for case 1, a comparison with the alternative cost for expanding the wastewater treatment capacity with more process equipment for activated sludge treatment. The results reveal that anaerobic digestion at pulp mills may both expand the production of renewable vehicle fuel but also enable increased efficiency and revenue at Kraft pulp mills.
  •  
38.
  • Larsson, Mårten (författare)
  • The role of methane and hydrogen in a fossil-free Swedish transport sector
  • 2015
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Drastic reductions of greenhouse gas emissions are required to limit the severe risks associated with a changing climate. One measure is to disrupt the fossil-fuel dependency in the transport sector, but it appears difficult and costly in comparison to other measures.Vehicles and fuels are available, but no single alternative can replace petrol and diesel in all parts of the transport system. None of them are ideal regarding all of the following aspects: vehicle performance, fuel production potential, sustainability, infrastructure, technology development and economy. Instead, several fuels are needed.In this thesis, the aim is to investigate the role of methane and hydrogen in a fossil- free vehicle fleet in Sweden, and compare them with other fuels in terms of well-to-wheel energy efficiency and economy. Processes for producing methane from biomass, waste streams from pulp mills and electricity are studied with techno-economic methods. Furthermore, well-to-wheel studies and scenarios are used to investigate the fuel chains and the interaction with the energy and transport systems.Effects of policy instruments on the development of biogas in the Swedish transport sector are also analysed and policy instruments are suggested to increase the use of methane and to introduce hydrogen and fuel cell electric vehicles. The results reveal that tax exemptions and investment support have been and will continue to be important policy instruments, but that effective policy instruments are needed to develop fuelling infrastructure and to support alternative vehicles.Electricity will be an important transport fuel for several reasons; the electric powertrain enables high energy efficiency and electricity can be produced from various renewable energy sources. Nevertheless, other fuels will be needed as complements to electricity. The results reveal that methane and hydrogen and associated vehicles may be necessary to reach a fossil-free vehicle fleet in Sweden. These fuels have several advantages:-        The function of the vehicles resembles conventional vehicles but with lower local and global emissions.-        Methane is a well proven as a transport fuel and hydrogen infrastructure and FCEVs, are commercial or close to commercialisation.-        They enable high well-to-wheel energy efficiency.-        They can be produced from renewable electricity and act as energy storage.
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39.
  • Larsson, Mårten, 1983-, et al. (författare)
  • Upgraded biogas for transport in Sweden : effects of policy instruments on production, infrastructure deployment and vehicle sales
  • 2016
  • Ingår i: Journal of Cleaner Production. - : Elsevier. - 0959-6526 .- 1879-1786. ; 112, s. 3774-3784
  • Tidskriftsartikel (refereegranskat)abstract
    • Sweden is a leading country in the development of upgraded biogas for use in the transport sector. The introduction of a new vehicle fuel is complex when the production, infrastructure, and vehicle fleet must be developed simultaneously. The aim of this article is to present and analyse the development of upgraded biogas in the Swedish transport sector in relation to policy instruments and the availability of a natural gas grid. Plausible implications for the future development of the biogas system are also analysed.The development of upgraded biogas in Sweden's transport sector is heavily influenced in several ways by domestic policy instruments. Investment support schemes and exemptions from energy and carbon dioxide taxes have been key instruments in initiating the construction of new biogas production facilities and infrastructure. The study of the biogas development in relation to the natural gas grid presented in this article indicates that it may not be necessary to construct a comprehensive network of pipelines for methane (natural gas) to develop the market – at least not initially. In Sweden and elsewhere the biogas volumes will still be quite small in the near future and it is possible to achieve biogas development without an available methane gas grid.Public procurement, investment schemes and reduced fringe benefit tax have likely been important policy instruments in the introduction of biogas vehicles, whereas the support for private biogas cars has been short-sighted in some ways, and not sufficient to achieve a competitive cost of ownership for biogas cars in relation to diesel cars.The future strategy for biogas should be based on a realistic potential for using biogas in the transport sector; this would determine whether further market expansion is necessary or if incentives should be focused on development of the production side to cover the current demand for vehicle gas.The development of biogas production likely depends on continued tax exemptions, which are currently available only until the end of 2015; it is uncertain whether they will remain in place. If biogas should be promoted further among private car owners, more visible incentives for private cars are needed together with incentives for expanding the fuelling infrastructure network.
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40.
  • Magnusson, Mimmi, 1980-, et al. (författare)
  • Biogas from mechanical pulping industry : Potential improvement for increased biomass vehicle fuels
  • 2012
  • Ingår i: Proceedings of the 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes, ECOS 2012. - 9788866553229 ; , s. 56-67
  • Konferensbidrag (refereegranskat)abstract
    • Biogas is a vehicle fuel of the first generation of biofuels with great potential for reducing the climate impact from the transport sector. Today biogas is mainly produced by digestion in Sweden and the total amounts to 1.4 TWhLHV/year (2010) of which about 0.6 TWhLHV is upgraded and used in the transport sector. Using industrial wastewater, e.g. from a pulp and paper mill, as substrate for production of biogas, the amount of renewable fuel to the transport sector could be increased. In the pulping industry, substantial amounts of organic matter are generated; this is commonly treated aerobically to reduce the chemical oxygen demand (COD) in the effluent streams before discharge to a recipient. Treating these effluent streams mainly anaerobically instead could contribute to the transport sector's energy supply. The aim of this study is to investigate the potential for using effluent streams from the Swedish mechanical pulp and paper industry to produce biogas. A typical Swedish mechanical pulp mill is considered for anaerobic treatment of the wastewaters. This type of pulp mill presently uses conventional methods for wastewater treatment to reduce COD, but converting most of this to anaerobic treatment would increase the amount of biogas produced. When considering this conversion in a larger context, supposing that anaerobic treatment would be applied to all Swedish mechanical pulp mills, which stand for about 30% of the total Swedish pulp production, it is shown that the production could amount to as much as 0.5 TWhLHV/year of biogas. This represents about one third of the biogas produced in Sweden today. The main conclusion of this study is that if anaerobic treatment of effluent streams from the pulping industry were introduced, the biogas production in Sweden could be significantly increased, thus moving one step further in reducing the transport sector's climate impact.
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41.
  • Magnusson, Mimmi, 1980-, et al. (författare)
  • Biogas potential in the Swedish pulp and paper industry
  • 2012
  • Ingår i: Proceedings of ICCE 2012. - 9781771360425 ; , s. 61-68
  • Konferensbidrag (refereegranskat)abstract
    • The European Union target of 10 % renewable fuels in the transport sector by 2020 is still far off, with 2.6% renewables on the EU level (2007) and 5.7% nationally in Sweden (2010). Biogas today accounts for a minor share of the renewable vehicle fuels in Sweden, but has the potential to increase. This study estimates the potential for producing biogas by anaerobic digestion as a part of the wastewater treatment in Swedish pulp and paper mills. The technology is mature and is used for example in municipal wastewater facilities but not as yet in the Swedish pulp and paper industry even though many of the effluent streams are well-suited for it. The results show that applying anaerobic wastewater treatment at Sweden’s pulp and paper mills may render as much as 1 TWhLHV/year, which would increase the present biogas production of 1.4 TWhLHV (2010) by 70%.
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42.
  • Magnusson, Mimmi, 1980- (författare)
  • Energy systems studied of biogas : Generation aspects of renewable vehicle fuels in the transport system
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The transport sector is seen as particularly problematic when concerns about climate change and dependency on fossil energy are discussed. Because of this, bioenergy is strongly promoted for use in the transport sector, both on a European level and nationally in Sweden. Even though bioenergy is considered one of the key solutions, it is generally agreed that both supply- and demand-side measures will be needed to achieve a change to a more sustainable transport system. One of the reasons for this is the limited availability of biomass, especially agricultural feedstocks competing with food or feed production. Woody biomass, however more abundant, is also exposed to tough competition from other sectors. In this thesis, the role of biogas as a vehicle fuel in a future sustainable transport system is discussed together with the prerequisites needed to realise such a transport system. Biogas is a biofuel that could be produced in several different ways: by anaerobic digestion, which is a first-generation production route, by gasification, which is a second-generation process, and by catalytic reduction of carbon dioxide, a third-generation technology. The main focus in this thesis is on biogas produced by anaerobic digestion and the results show that there is a significant potential for an increase compared to today’s production. Biogas from anaerobic digestion, however, will only be able to cover a minor part of the demand in the Swedish transport sector. Considering biogas of the second and third generations, the potential for production is more uncertain in a mid-term future, mainly due to competition for feedstock, the possibility to produce other fuels by these processes, and the present immaturity of the technology. The limited potential for replacing fossil vehicle fuels, either by biogas or other renewable fuels, clearly shows the need for demand-side measures in the transport system as well. This thesis shows the importance of technical and non-technical means to decrease the demand for transport and to make the transport as efficient as possible. The results show that both energy-efficient vehicles and behavioural and infrastructural changes will be required. Policies and economic incentives set by governments and decision-making bodies have a prominent role to play, in order to bring about a shift to a more sustainable transport system, however, measures taken on individual level will also have a great impact to contribute to a more sustainable transport system.
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43.
  •  
44.
  • Magnusson, Mimmi, et al. (författare)
  • Introducing Renewable Electricity to increase Biogas Production Potential
  • 2010
  • Ingår i: International Conference on Applied Energy 2010.
  • Konferensbidrag (refereegranskat)abstract
    • Facing the challenge of CO2 reduction in the transport sector, the focus on alternative fuels has been growing rapidly. Several fuels and production methods have been proposed which illustrate various aspects of how to contribute to CO2 mitigation.This paper presents how biogas production from a given amount of biomass may be increased. To enhance biogas production, process improvements for today’s digestion process and also biogas produced from biomass gasification are suggested. Both biogas production via digestion and gasification of biomass produce CO2 as a by-product. To increase the biogas production, this green CO2 could be used to produce additional methane using the well-known Sabatier reaction. The hydrogen required for the reaction is proposed to originate from electrolysis of water, where the electricity needed is preferably produced from a renewable source, e.g. wind power. Reusing carbon in such manner reduces the need for fossil methane while supplying fuel to the transport sector.In this study, a base case scenario describing plants of typical sizes and efficiencies is presented for both digestion and gasification. It is shown that, using the Sabatier process on this base case, the methane production from gasification may be increased by about 140 %. For the digestion, the increase, including process improvements, is about 74 %. By using this method more biogas may be produced, without adding new raw material to the process. This would present a great way to meet society’s increasing demand for renewable fuels, while simultaneously reusing CO2.
  •  
45.
  • Mohseni, Farzad, et al. (författare)
  • Biogas from renewable electricity : Increasing a climate neutral fuel supply
  • 2012
  • Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 90:1, s. 11-16
  • Tidskriftsartikel (refereegranskat)abstract
    • If considering the increased utilisation of renewable electricity during the last decade, it is realistic to assume that a significant part of future power production will originate from renewable sources. These are normally intermittent and would cause a fluctuating electricity production. A common suggestion for stabilising intermittent power in the grid is to produce hydrogen through water electrolysis thus storing the energy for later. It could work as an excellent load management tool to control the intermittency, due to its flexibility. In turn, hydrogen could be used as a fuel in transport if compressed or liquefied. However, since hydrogen is highly energy demanding to compress, and moreover, has relatively low energy content per volume it would be more beneficial to store the hydrogen chemically attached to carbon forming synthetic methane (i.e. biogas). This paper presents how biogas production from a given amount of biomass could be increased by addition of renewable electricity. Commonly biogas is produced through digestion of organic material. Recently also biomass gasification is gaining more attention and is under development. However, in both cases, a significant amount of carbon dioxide is produced as by-product which is subject for separation and disposal. To increase the biogas yield, the separated carbon dioxide (which is considered as climate neutral) could, instead of being seen as waste, be used as a component to produce additional methane through the well-known Sabatier reaction. In such process the carbon could act as hydrogen carrier of hydrogen originating from water electrolysis driven by renewable sources. In this study a base case scenario, describing biogas plants of typical sizes and efficiencies, is presented for both digestion and gasification. It is assessed that, if implementing the Sabatier process on gasification, the methane production would be increased by about 110%. For the digestion, the increase, including process improvements, would be about 74%. Hence, this method results in greatly increased biogas potential without the addition of new raw material to the process. Additionally, such model would present a great way to meet the transport sector's increasing demand for renewable fuels, while simultaneously reducing net emissions of carbon dioxide.
  •  
46.
  • Mohseni, Farzad, 1981- (författare)
  • Power to gas : Bridging renewable electricity to the transport sector
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Globally, transport accounts for a significant part of the total energy utilization and is heavily dominated by fossil fuels. The main challenge is how the greenhouse gas emissions in road transport can be addressed. Moreover, the use of fossil fuels in road transport makes most countries or regions dependent on those with oil and/or gas assets. With that said, the question arises of what can be done to reduce the levels of greenhouse gas emissions and furthermore reduce dependency on oil? One angle is to study what source of energy is used.Biomass is considered to be an important energy contributor in future transport and has been a reliable energy source for a long time. However, it is commonly known that biomass alone cannot sustain the energy needs in the transport sector by far.This work presents an alternative where renewable electricity could play a significant role in road transport within a relatively short time period. Today the amount of electricity used in road transport is negligible but has a potential to contribute substantially. It is suggested that the electricity should be stored, or “packaged” in a chemical manner, as a way of conserving the electrical energy. One way of doing so is to chemically synthesize fuels. It has been investigated how a fossil free transport system could be designed, to reach high levels of self-sufficiency. According to the studies, renewable electricity could have the single most important role in such a system.   Among the synthetic fuels, synthetic methane (also called synthetic biogas) is the main focus of the thesis. Hydrogen is obtained through water electrolysis, driven by electricity (preferable renewable), and reacted with carbon dioxide to produce synthetic methane. The concept of the mentioned process goes under the name Power to Gas. The electricity to fuel efficiency of such a process reaches about 50 %, but if utilizing excess heat produced during the electrolysis and the reaction, the total process efficiency can reach much higher levels.The economics of the process is as important as the technology itself in terms of large scale implementation. The price of electricity and biogas are the most important influences on the economic viability. The minimum “spread” between purchase and selling price can be determined to obtain a general perception of the economic feasibility. In this case biogas must be sold about 2.6 times higher than purchased electricity per kWh.
  •  
47.
  • Mohseni, Farzad, et al. (författare)
  • The competitiveness of synthetic natural gas as a propellant in the Swedish fuel market
  • 2013
  • Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215 .- 1873-6777. ; 52, s. 810-818
  • Tidskriftsartikel (refereegranskat)abstract
    • The road transport sector today is almost exclusively dependent on fossil fuels. Consequently, it will need to face a radical change if it aims to switch from a fossil-based system to a renewable-based system. Even though there are many promising technologies under development, they must also be economically viable to be implemented. This paper studies the economic feasibility of synthesizing natural gas through methanation of carbon dioxide and hydrogen from water electrolysis. It is shown that the main influences for profitability are electricity prices, synthetic natural gas (SNG) selling prices and that the by-products from the process are sold. The base scenario generates a 16% annual return on investment assuming that SNG can be sold at the same price as petrol. A general number based on set conditions was that the SNG must be sold at a price about 2.6 times higher per kWh than when bought in form of electricity. The sensitivity analysis indicates that the running costs weigh more heavily than the yearly investment cost and off-peak production can therefore still be economically profitable with only a moderate reduction of electricity price. The calculations and prices are based on Swedish prerequisites but are applicable to other countries and regions.
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48.
  •  
49.
  • Sadegh-Vaziri, Ramiar, 1987- (författare)
  • Biomass to Biofuel : Syngas Cleaning and Biomass Feedstock
  • 2017
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis builds around the idea of a biofuel production process that is comprised of biomass production, biomass gasification, gas cleaning, and fuel production. In this work, we specifically looked into H2S removal as a part of cleaning the producer gas and flocculation of microalgae which is involved in the harvesting of microalgae after biomass production. One of the impurities to remove from the producer gas is hydrogen sulfide which can be removed by using a packed bed of zinc oxide. Despite the regular use, it was only recently shown that during reaction with H2S, nano-size particles of ZnO exhibit void formation and outward growth. In this work, a micro-scale model was introduced to describe the void formation and outward growth. On the macro-scale, the simulations captured pore clogging of pellets due to the outward growth. The pore clogging prevents the full conversion of pellets and consequently leads to shorter breakthrough times of beds. The second problem investigated here deals with the flocculation of microalgae. Microalgae is produced in relatively low concentrations in the incubator liquid medium and during the harvesting, the concentration is increased to an acceptable level. The harvesting process includes a flocculation followed by a filtration or centrifuge unit. During flocculation, microalgae are stimulated to aggregate and form clusters. The experiments showed that the mean size of clusters formed during flocculation increases with time to a maximum and then starts decreasing, resulting in an overshoot in the mean size profile. The size of clusters influence the efficiency of the afterward filtration or centrifuge, thus it is of interest to carefully track the size evolution of clusters, making the studying of overshoot a crucial research topic. In this work, the possible mechanisms behind this overshoot were investigated.
  •  
50.
  • Saxe, Maria, et al. (författare)
  • A follow-up and conclusive report on the attitude towards hydrogen fuel cell buses in the CUTE project : From passengers in Stockholm to bus operators in Europe
  • 2007
  • Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 32:17, s. 4295-4305
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper concerns the attitude towards the fuel cell bus and the hydrogen technology used in the CUTE project, represented by two passenger surveys performed in Stockholm, a survey performed among drivers in four cities and final statements as well as recommendations for future projects by project partners.Main results are:The passengers' willingness to pay for having more fuel cell buses in public transport was still low after one year of operation.Concern about safety is not an issue among passengers or drivers.The acceleration was rated as inferior to that of regular buses by 50% of the drivers; this differs from earlier findings in Stockholm.The operators were pleased with the reliability of the buses and the trust in the new technology grew stronger during the project period. Main problems were lack of spare parts and insufficient information sharing due to confidentiality.
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