| 1. |
- Difs, Kristina, et al.
(författare)
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Biomass gasification opportunities in a district heating system
- 2010
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Ingår i: Biomass and Bioenergy. - : Elsevier Science B.V., Amsterdam.. - 0961-9534 .- 1873-2909. ; 34:5, s. 637-651
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates the economic effects and the potential for reduced CO2 emissions when biomass gasification applications are introduced in a Swedish district heating (DH) system. The gasification applications included in the study deliver heat to the DH network while producing renewable electricity or biofuels. Gasification applications included are: external superheater for steam from waste incineration (waste boost, WE), gas engine CHP (BIGGE), combined cycle CHP (BIGCC) and production of synthetic natural gas (SNG) for use as transportation fuel. Six scenarios are used, employing two time perspectives - short-term and medium-term - and differing in economic input data, investment options and technical system. To evaluate the economic performance an optimisation model is used to identify the most profitable alternatives regarding investments and plant operation while meeting the DH demand. This study shows that introducing biomass gasification in the DH system will lead to economic benefits for the DH supplier as well as reduce global CO2 emissions. Biomass gasification significantly increases the potential for production of high value products (electricity or SNG) in the DH system. However, which form of investment that is most profitable is shown to be highly dependent on the level of policy instruments for biofuels and renewable electricity. Biomass gasification applications can thus be interesting for DH suppliers in the future, and may be a vital measure to reach the 2020 targets for greenhouse gases and renewable energy, given continued technology development and long-term policy instruments.
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| 2. |
- Difs, Kristina
(författare)
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District Heating and CHP : Local Possibilities for Global Climate Change Mitigation
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Global warming, in combination with increasing energy demand and higher energy prices, makes it necessary to change the energy use. To secure the energy supply and to develop sustainable societies, construction of energy-efficient systems is at the same time most vital. The aim of this thesis is therefore to identify how a local energy company, producing district heating (DH), district cooling (DC) and electricity in combined heat and power (CHP) plants, can contribute to resource-efficient energy systems and cost-effective reductions of global carbon dioxide (CO2) emissions, along with its customers. Analyses have been performed on how a local energy company can optimise their DH and DC production and what supply-side and demand-side measures can lead to energy-efficient systems in combination with economic and climate change benefits. The energy company in focus is located in Linköping, Sweden. Optimisation models, such as MODEST and reMIND, have been used for analysing the energy systems. Scenario and sensitivity analyses have also been performed for evaluation of the robustness of the energy systems studied. For all analyses a European energy system perspective was applied, where a fully deregulated European electricity market with no bottlenecks or other system failures was assumed.In this thesis it is concluded that of the DH-supply technologies studied, the biomass gasification applications and the natural gas combined cycle (NGCC) CHP are the technologies with the largest global CO2 reduction potential, while the biomass-fuelled plant that only produces heat is the investment with the smallest global CO2 reduction and savings potential. However, the global CO2 reduction potential for the biomass integrated gasification combined cycle (BIGCC) CHP and NGCC CHP, the two technologies with highest electricity efficiencies, is highly dependent on the assumptions made about marginal European electricity production. Regarding the effect on the DH system cost the gasification application integrated with production of renewable biofuels (SNG) for the transport sector is the investment option with the largest savings potential for lower electricity prices, while with increasing electricity prices the BIGCC and NGCC CHP plants are the most cost-effective investment options. The economic outcome for biomass gasification applications is, however, dependent on the level of policy instruments for biofuels and renewable electricity. Moreover, it was shown that the tradable green certificates for renewable electricity can, when applied to DH systems, contribute to investments that will not fully utilise the DH systems’ potential for global CO2 emissions reductions.Also illustrated is that conversion of industrial processes, utilising electricity and fossil fuels, to DH and DC can contribute to energy savings. Since DH is mainly used for space heating, the heat demand for DH systems is strongly outdoor temperature-dependent. By converting industrial processes, where the heat demand is often dependent on process hours instead of outdoor temperature, the heat loads in DH systems can become more evenly distributed over the year, with increased base-load heat demand and increased electricity generation in CHP plants as an outcome. This extra electricity production, in combination with the freed electricity when converting electricity-using processes to DH, can replace marginal electricity production in the European electricity market, resulting in reduced global CO2 emissions.Demonstrated in this thesis is that the local energy company, along with its customers, can contribute to reaching the European Union’s targets of reducing energy use and decreasing CO2 emissions. This can be achieved in a manner that is cost-effective to both the local energy company and the customers.
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| 3. |
- Difs, Kristina, et al.
(författare)
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Energy conservation measures in buildings heated by district heating - A local energy system perspective
- 2010
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Ingår i: Energy. - : Elsevier Science B.V., Amsterdam.. - 0360-5442 .- 1873-6785. ; 35:8, s. 3194-3203
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Tidskriftsartikel (refereegranskat)abstract
- The extensive energy use in the European building sector creates opportunities for implementing energy conservation measures (ECMs) in residential buildings. If ECM are implemented in buildings that are connected to a district heating (DH) system, the operation of DH plants may be affected, which in turn may change both revenue and electricity production in cogeneration plants. In this study a local energy system, containing a DH supplier and its customer, has been analysed when implementing three ECMs: heat load control, attic insulation and electricity savings. This study is unique since it analyses economic and CO2 impacts of the ECMs in both a user and a supplier perspective in combination with a deregulated European electricity market. Results show that for the local energy system electricity savings should be prioritised over a reduction in DH use, both from an economic and a global CO2 perspective. For the DH supplier attic insulation demonstrates unprofitable results, even though this measure affects the expensive peak load boilers most. Heat load control is however financially beneficial for both the DH supplier and the residences. Furthermore, the relation between the fixed and variable DH costs is highlighted as a key factor for the profitability of the ECMs.
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| 4. |
- Difs, Kristina, 1977-, et al.
(författare)
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Increased industrial district heating use in a CHP system : economic consequences and impact on global CO2 emissions
- 2009
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Ingår i: 5th European Conference on Economics and Management of Energy in Industry.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of district heating (DH) in industrial processes is relatively limited compared to other fuels and electricity. Hence, the industrial sector has great potential to convert from electricity and fossil fuels to DH. In addition, DH is mainly used for space heating and hot tap water, which makes the DH demand strongly seasonally dependent. By converting industrial processes like cooling, drying and industrial heating to DH, the heat load curve will be more evenly distributed throughout the year, thus utilizing the DH production resources better. This paper analyses how conversions from electricity or other fuels to district heating (DH) in industrial processes will affect an energy system. The effect of a more evenly distributed heat load profile is analysed with different policy instruments, fuel prices and electricity prices. In this study, three CHP plants acting as base load plants, which utilize different fuels (biofuel, waste and natural gas), are analysed. The result shows that when the use of district heating in industrial processes is increased it will lead to reduced system cost in both the biofueled and waste-incinerated combined heat and power system. Furthermore, when considering European electricity production in coal condensing and natural gas power plants, conversion to DH will also lead to possible reduced global CO2 emissions.
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| 5. |
- Difs, Kristina, et al.
(författare)
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Increased use of district heating in industrial processes - Impacts on heat load duration
- 2009
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 86:11, s. 2327-2334
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Tidskriftsartikel (refereegranskat)abstract
- Current knowledge of the potential for an increased use of industrial district heating (DH) due to conversions of industrial processes to DH is limited. In this paper, a Method for Heat Load Analysis (MeHLA) for exploring industrial DH conversions has been developed. This method can be a helpful tool for analyzing the impact different industrial processes have on the local DH system, when processes that utilize electricity and other fuels, convert to utilizing DH instead. Heat loads for different types of industries and processes are analyzed according to characteristics such as temperature levels and time dependency. MeHLA has been used to analyze 34 Swedish industries and the method demonstrates how conversion of industrial processes to DH can result in heat load duration curves that are less outdoor temperature-dependent and more evenly distributed over the year. An evenly distributed heat load curve can result in increased annual operating time for base load DH plants such as cogeneration plants, leading to increased electricity generation. In addition to the positive effects for the DH load duration curve, the conversions to DH can also lead to an 11% reduction in the use of electricity, a 40% reduction in the use of fossil fuels and a total energy end-use saving of 6% in the industries. Converting the industrial processes to DH will also lead to a potential reduction of the global carbon dioxide emissions by 112,000 tonnes per year.
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| 6. |
- Difs, Kristina
(författare)
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National energy policies: obstructing the reduction of global CO2 emissions? An analysis of Swedish energy policies for the district heating sector
- 2010
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Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215 .- 1873-6777. ; 38:12, s. 7775-7782
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Tidskriftsartikel (refereegranskat)abstract
- The effect of national energy policies on a local Swedish district heating (DH) system has been studied regarding the profitability of new investments and the potential for climate change mitigation. The DH system has been optimised regarding three investments: biomass-fuelled CHP (bio CHP), natural gas-fuelled combined cycle CHP (NGCC CHP) and biomass-fuelled heat-only boiler (bio HOB) in two scenarios (with or without national taxes and policy instruments). In both scenarios EU’s tradable CO2 emission permits are included. Results from the study show that when national policies are included, the most cost-effective investment option is the bio CHP technology. However, when national taxes and policy instruments are excluded, the DH system containing the NGCC CHP plant has 30% lower system cost than the bio CHP system. Regardless of the scenario and when coal condensing is considered as marginal electricity production, the NGCC CHP has the largest global CO2 reduction potential, about 300 ktonne CO2. However, the CO2 reduction potential is highly dependent on the marginal electricity production. Demonstrated here is that national policies such as tradable green certificates can, when applied to DH systems, contribute to investments that will not fully utilise the DH systems’ potential for global CO2 emissions reductions.
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| 7. |
- Difs, Kristina, et al.
(författare)
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Pricing district heating by marginal cost
- 2009
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Ingår i: ENERGY POLICY. - : Elsevier BV. - 0301-4215. ; 37:2, s. 606-616
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Tidskriftsartikel (refereegranskat)abstract
- A vital measure for industries when redirecting the energy systems towards sustainability is conversion from electricity to district heating (DH). This conversion can be achieved for example, by replacing electrical heating with DH and compression cooling with heat-driven absorption cooling. Conversion to DH must, however, always be an economically attractive choice for an industry. In this paper the effects for industries and the local DH supplier are analysed when pricing DH by marginal cost in combination with industrial energy efficiency measures. Energy audits have shown that the analysed industries can reduce their annual electricity use by 30% and increase the use of DH by 56%. When marginal costs are applied as DH tariffs and the industrial energy efficiency measures are implemented, the industrial energy costs can be reduced by 17%. When implementing the industrial energy efficiency measures and also considering a utility investment in the local energy system, the local DH supplier has a potential to reduce the total energy system cost by 1.6 million EUR. Global carbon dioxide emissions can be reduced by 25,000 tonnes if the industrial energy efficiency measures are implemented and when coal-condensing power is assumed to be the marginal electricity source.
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| 8. |
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| 9. |
- Trygg, Louise, 1966-, et al.
(författare)
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Absorption Cooling in CHP systems - old technique with new opportunities
- 2008
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Ingår i: The 10th World Renewable Energy Congress.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The threat of global warming is escalating and the redirection of our energy systems towards lower emissions of global CO2 is a vital measure. Electricity use is projected to almost double over the next two decades [IEO, 2005] and more than 10% of the worldwide electricity usage is due to refrigeration. The need for cooling is rising and a common way of producing chilled water for pipeline distribution, i.e. district cooling, is to use compression cooling. In Sweden, the electricity price is low compared to other European countries. On the European continent, the electricity price is characterised by changes over the day while the price in Sweden varies over the season. With a fully deregulated European electricity market, with no restrictions on transfer capacity, the electricity price in Europe will most likely level out at an equilibrium price. This means that Swedish customers will face higher electricity prices and prices that vary over the day instead of over the season. Increased electricity price will make it more attractive to increase the generation of electricity from combined heat and power (CHP) systems in Sweden. Production of cooling with district heating driven absorption chillers (AC) will enhanced the possibilities to produce electricity in these systems. This means that when compression chillers (CC) are replaced with AC, the need for electricity for cooling systems will decrease and at the same time the potential for electricity production in a CHP system will increase. In Europe, coal-fired condensing power plants have the highest variable cost and thus function as the marginal source of electricity production. Assuming marginal power production at 33% electrical efficiency, each megawatt-hour of electricity generated in such a coal-fired condensing power plant thus releases approximately one tonne of carbon dioxide (Sjödin, 2003). This argument means that coal condensing is the marginal source in Sweden as well as in the rest of the EU, which is an important assumption in this study.
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| 10. |
- Trygg, Louise, et al.
(författare)
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Optimala fjärrvärmesystem i symbios med industri och samhälle : för ett hållbart energisystem
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Med ökad medvetenhet om den pågående klimatförändringen är det av central betydelse att hitta åtgärder som leder till en omställning mot hållbara energisystem och ett hållbart samhälle. Fjärrvärme har en viktig roll i energiförsörjningen eftersom den ger möjlighet att ta tillvara värmeresurser som annars kan vara svåra att utnyttja, som exempelvis spillvärme från industrier och förbränning av avfall. Fjärrvärmesystemen möjliggör också elproduktion i kraftvärmeverk, med betydligt högre totalverkningsgrad än vid separat el- respektive värmeproduktion. Ett led i omställning mot hållbarhet är därför förändring av energisystemet mot en ökad användning av fjärrvärme och minskad användning av el genom dels effektiviseringar och dels via konverteringar från olja och el till fjärrvärme. Våra svenska fjärrvärmesystem är väl utbyggda och utgör en viktig resurs i detta arbete. Den pågående klimatförändringen kommer med största trolighet att medföra förändrat uttagsmönster för både värme- och kylbehov. Med ett varmare klimat minskar behovet av värme samtidigt som efterfrågan på kyla ökar. Förändrade uttagsmönster för fjärrvärme och kyla, ökad konkurrens och tydligare medvetenhet om den pågående klimatförändringen medför att fjärrvärmen står inför nya utmaningar där utveckling av nya affärer och nya marknader blir allt viktigare. Idag används fjärrvärmen främst för uppvärmning och tappvarmvatten vilket medför att utnyttjningstiden för fjärrvärme till stor del är utomhustemperaturberoende. För att minska utomhustemperaturberoendet och på så sätt få en lastkurva för fjärrvärme som är mer ”fyrkantig” i sin utformning krävs ett fjärrvärmebehov som är mer jämnt fördelat under året. Ett jämnare effektuttag över året leder till bättre utnyttjningstid och driftförhållande för baslastanläggningarna vilket är gynnsamt speciellt i ett kraftvärmesystem eftersom det möjliggör utökad elproduktion. Flera studier har visat hur utnyttjningstid och värmelasten är de faktorer som påverkar lönsamheten mest för ett biobränsleeldat kraftvärmeverk. Syftet med föreliggande projekt är att visa hur fjärrvärmesystemen kan bidra till resurssnåla energisystem med minskad klimatpåverkan. Men hjälp av systemstudier av olika fall lyfter projektet fram exempel där industrier och energileverantörer kan samarbeta kring fjärrvärmerelaterade åtgärder och hur detta leder till hållbara fjärrvärmesystem. Åtgärder som studerats är ökad användning av fjärrvärme inom industriella processer, absorptionskyla samt introduktion av bioenergikombinat i fjärrvärmesystem. För att få kunskap om hur dessa idéer kan gå från att vara potentiellt lönsamma åtgärder till att bli faktiska genomförda projekt, analyseras även vilka faktorer som driver fram ett värmesamarbete mellan en industri och ett energibolag. Resultatet från projektet visar att det finns stora potentialer att öka användningen av fjärrvärme inom industriella processer, från 100 GWh till 300 GWh för de 41 industrier belägna i 6 olika kommuner som analyserats. Konverteringen till ökad fjärrvärmeanvändning påverkar lastkurvan så att utnyttjningstiden ökar, vilket ger en bättre utnyttjandegrad av fjärrvärmeanläggningarna i systemet. På samma sätt är absorptionskyla för att möta ökat kylbehov en åtgärd som leder till mer uthålliga energisystem. När fjärrvärmedrivna absorptionskylmaskiner introduceras i Örebros energisystem minskar de globala emissionerna av CO2 samtidigt som systemkostnaden reduceras. Ett ökat framtida kylbehov i Örebro i samband med högre elpriser medför att absorptions kyla ersätter både frikyla och kompressionskyla med en optimal andel kyla från absorptionskylmaskiner på över 60 % och ökad ekonomisk lönsamhet med ca 6 MSEK per år. Ytterligare en åtgärd som bidrar till omställning mot minskad klimatpåverkan är investering i bioenergikombinat. Introduktionen av storskalig förgasning i Linköpings fjärrvärmesystem har en potential till en signifikant minskning av globala CO2-utsläpp jämfört med om endast konventionell biokraftvärme beaktas. Reduktionspotentialen varierar beroende på vilken typ av förgasning som investeras i. Intervjuer och enkätstudier i syftet att analysera hur dessa värmerelaterade åtgärder kan gå från potentiella åtgärder till att bli verkliga lönsamma projekt visade att finns ett antal högt rankade framgångsfaktorer som inte är främst ekonomiska utan snarare inomorganisatoriska eller individrelaterade till sin karaktär. Styrmedel är högt rankat, i synnerhet av industrin. En parameter som också visat sig utgöra en katalysator i flera samarbeten har varit att ett universitet varit involverat och byggt optimeringsmodeller över energisystemet på orten. Fjärrvärmesystemen har en viktig roll i den övergripande omställningen av våra energisystem mot ökad grad av hållbarhet. Med ökad medvetenhet om den pågående klimatförändringen är det av central betydelse att hitta åtgärder som främjar och påskyndar en sådan omställning. I detta arbete lyfts flera åtgärder fram som visar hur fjärrvärmesystem på ett tydligt sätt kan bidra till både minskad klimatpåverkan och ekonomiska vinster. Ökad fjärrvärme i industriella processer, absorptionskyla för att möta ökat kylbehov och bioenergikombinat är exempel på åtgärder som leder till utformning av optimala fjärrvärmesystem för ett hållbart samhälle. Detta arbete har också visat vad som krävs för att dessa värmerelaterade åtgärder mellan industrier och energileverantörer ska bli verkliga lönsamma samarbeten. Genom att identifiera dessa åtgärder kan vi på ett tydligt sätt visa på fjärrvärmens unika möjligheter att bli en ännu mer central aktör i den nödvändiga och mycket viktiga omställningen mot hållbarhet.
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