| 1. |
- Gustafsson, Stig-Inge
(författare)
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Carpentry factory and municipal electricity loads
- 1998
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 39:3-4, s. 343-347
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Tidskriftsartikel (refereegranskat)abstract
- Load management of electricity loads has received more interest in recent years. At least in Sweden, this is natural because of a rather cheap energy price, while at the same time, the demand charge is high. If a company could save the precise kWh that build the peak demand, then these would have a value of more than 200 times the off-peak kWh. This paper deals with monitored electricity data for two carpentry industries and one municipality, both situated in the south of Sweden. The ideal ! situation would be if the industry could reduce their peak demand and, at the same time, reduce the peak for the utility. Both participants would, in that case, save money, and the payback time for load management equipment would decrease substantially. If, however, a load management system at the carpentry transfers kWh to peak hours for the utility, the industry will save money, while the utility gets higher costs. The result of the study is that the Swedish electricity rates in use today are a very poor means of encouraging worthwhile load management, and often, they even aggravate the situation.
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| 2. |
- Gustafsson, Stig-Inge, 1948-
(författare)
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Energy usage and conservation in surfacing lines
- 2000
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Ingår i: Energy Conversion and Management. - 0196-8904 .- 1879-2227. ; 41:15, s. 1649-1669
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with energy usage and conservation for a surfacing line in a carpentry factory. In this line, wood panels are coated with paint in a highly automated fashion. The products vary in shapes and the way they shall be coated, and therefore, a number of machines are present in the line which is about 100 m long. Sanding machines, roller coaters, dryers etc. are installed, and all machinery uses electricity for their operation. There are, however, other equipments coupled to the line. One example is the wood dust transportation system, and another is the steam system used for heating purposes. By use of a number of electricity meters, monitoring ventilation flow rates etc., it has been possible to analyze how much energy is used in the surfacing line and also to propose measures to reduce this amount.
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| 3. |
- Gustafsson, Stig-Inge, et al.
(författare)
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Heat Accumulators in CHP Networks
- 1992
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 33:12, s. 1051-1061
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Tidskriftsartikel (refereegranskat)abstract
- In a Combined Heat and Power (CHP) network, it is sometimes optimal to install a device for storing heat from one period of time to another. Several possibilities exist. If the electricity demand is high, while at the same time the district heating load is too small to take care of the heat from the CHP plant, it could be optimal to store heat from peak periods and discharge the storage under off-peak. It might also be optimal to store heat during off-peak and use it under the district heating peak load. The storage is then used for decreasing either the district heating demand or for decreasing the electricity load used for space heating. The paper shows how a mixed integer program is developed for use in the optimization process. As a case study, the CHP system of Malmö, Sweden, is used. Further, a sensitivity analysis is elaborated in order to show how the optimal solution will vary due to changes in certain input data.
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| 4. |
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| 5. |
- Rolfsman, Björn, 1971-
(författare)
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Optimal supply and demand investments in municipal energy systems
- 2004
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Ingår i: Energy Conversion and Management. - 0196-8904 .- 1879-2227. ; 45:4, s. 595-611
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Tidskriftsartikel (refereegranskat)abstract
- In many municipalities, there are district heating networks, which are quite commonly supplied by combined heat and power plants (CHP). A district heating network contains buildings of different types. In this paper, one such municipal energy system is analysed. In order to provide space heating and domestic hot water, investments could be made on the supply side in power plants, or on the demand side in the buildings, for example in the form of extra wall insulation. The electricity from the CHP plants is supplied to the municipality but can also be sold to the electricity market, and electricity can, of course, also be bought from the market. The variation in price on the spot market over any given day is significant. The need for district heat in the building stock also varies, for example due to climatic conditions. The energy system in the case study is analysed with a mixed integer linear programming model. The model has 3 h time steps in order to reflect diurnal variations, and an entire year is analysed. A case study is presented for the city of Linköping in Sweden. On the demand side, the options are: extra wall insulation, extra attic insulation and better types of windows. The building stock is divided into nine categories. © 2003 Elsevier Ltd. All rights reserved.
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| 6. |
- Sundberg, Gunnel, et al.
(författare)
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Investments in combined heat and power plants : Influence of fuel price on cost minimised operation
- 2002
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Ingår i: Energy Conversion and Management. - 0196-8904 .- 1879-2227. ; 43:5, s. 639-650
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Tidskriftsartikel (refereegranskat)abstract
- Liberalisation of the electricity market and governmental politics influence heat and power supply in Sweden, like in many other countries. In this paper, the impact of subsidies and fuel and electricity costs on a representative Swedish district heating system is analysed. The energy system model MODEST (model for optimisation of dynamic energy systems with time dependent components and boundary conditions) was used to optimise investments and operation for heat and power production plants. At higher electricity prices, combined heat and power introduction may be profitable in the studied system. With current fuel prices, a natural gas fired combined cycle would primarily be favourable. A lower woodchips price and a governmental grant would make cogeneration with a biomass fired steam cycle more beneficial. © 2002 Elsevier Science Ltd. All rights reserved.
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| 7. |
- Ahlgren, Benjamin, et al.
(författare)
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A simplified model for linear correlation between annual yield and DNI for parabolic trough collectors
- 2018
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 174, s. 295-308
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a simple method for estimating annual thermal performance of parabolic trough collectors (PTCs) based on a linear relation with annual DNI for a certain latitude. A case study with simulations for a novel concentrating solar collector in 316 locations for three operating temperature scenarios worldwide was carried out and showed promising results for the latitudes and continents investigated. For a certain latitude and mean operating temperature, the annual yield of a PTC was found to be linearly proportional to yearly DNI. The proposed method will serve as a simplified alternative to the steady-state and quasi-dynamic methods already used. Estimating performance based on yearly DNI can be used by design engineers to do quick preliminary planning of solar plants. Customers can also use this method to evaluate existing solar collector installations. A TRNSYS/TRNSED tool that uses a steady-state model has been developed to carry out the simulations and it has been validated against a PTC array at Technical University of Denmark (DTU). The results show that the simplified method can give reliable estimates of long-term performance of parabolic trough collectors.
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| 8. |
- Ahlström, Johan, 1990, et al.
(författare)
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Economic potential for substitution of fossil fuels with liquefied biomethane in Swedish iron and steel industry – Synergy and competition with other sectors
- 2020
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Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- In Sweden, the iron and steel industry (ISI) is a major source of greenhouse gas (GHG) emissions. Most of the emissions result from the use of fossil reducing agents. Nevertheless, the use of fossil fuels for other purposes must also be eliminated in order to reach the Swedish emissions reduction targets. In this study, we investigate the possibility to replace fossil gaseous and liquid fuels used for heating in the ISI, with liquefied biomethane (LBG) produced through gasification of forest residues. We hypothesize that such utilization of fuels in the Swedish ISI is insufficient to independently drive the development of large-scale LBG production, and that other sectors demanding LBG, e.g., for transportation, can be expected to influence the economic potential for the ISI to switch to LBG. The paper investigates how demand for LBG from other sectors can contribute to, or prevent, a phase-out of fossil fuels used for heating purposes in the ISI under different future energy market scenarios, with additional analysis of the impact of a CO2 emissions charge. A geographically explicit cost-minimizing biofuel production localization model is combined with heat integration and energy market scenario analysis. The results show that from a set of possible future energy market scenarios, none yielded more than a 9% replacement of fossil fuels used for heating purposes in the ISI, and only when there was also a demand for LBG from other sectors. The scenarios corresponding to a more ambitious GHG mitigation policy did not achieve higher adoption of LBG, due to corresponding higher biomass prices. A CO2 charge exceeding 200 EUR/tonCO2 would be required to achieve a full phase-out of fossil fuels used for heating purposes in the ISI. We conclude that with the current policy situation, substitution of fossil fuels by LBG will not be economically feasible for the Swedish ISI.
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| 9. |
- Andersson, Jim, et al.
(författare)
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Co-gasification of black liquor and pyrolysis oil : Evaluation of blend ratios and methanol production capacities
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 110, s. 240-248
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Tidskriftsartikel (refereegranskat)abstract
- The main aim of this study is to investigate integrated methanol production via co-gasification of black liquor (BL) and pyrolysis oil (PO), at Swedish pulp mills. The objectives are to evaluate techno-economically different blends ratios for different pulp mill capacities. Furthermore, the future methanol production potential in Sweden and overall system consequences of large-scale implementation of PO/BL co-gasification are also assessed.It is concluded that gasification of pure BL and PO/BL blends up to 50% results in significantly lower production costs than what can be achieved by gasification of unblended PO. Co-gasification with 20–50% oil addition would be the most advantageous solution based on IRR for integrated biofuel plants in small pulp mills (200 kADt/y), whilst pure black liquor gasification (BLG) will be the most advantageous alternative for larger pulp mills. For pulp mill sizes between 300 and 600 kADt/y, it is also concluded that a feasible methanol production can be achieved at a methanol market price below 100 €/MW h, for production capacities ranging between 0.9 and 1.6 TW h/y for pure BLG, and between 1.2 and 6.5 TW h/y for PO/BL co-gasification. This study also shows that by introducing PO/BL co-gasification, fewer pulp mills would need to be converted to biofuel plants than with pure BLG, to meet a certain biofuel demand for a region. Due to the technical as well as organizational complexity of the integration this may prove beneficial, and could also potentially lower the total investment requirement to meet the total biofuel demand in the system. The main conclusion is that PO/BL co-gasification is a technically and economically attractive production route for production biomethanol.
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| 10. |
- Ansari, Danish, et al.
(författare)
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A gyroid TPMS heat sink for electronic cooling
- 2024
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 319
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Tidskriftsartikel (refereegranskat)abstract
- The trend toward thinner and lighter electronic devices necessitates developing advanced thermal management solutions to address modern microprocessors’ escalating heat dissipation demands. This study introduces an advanced thermal solution incorporating a gyroid TPMS structure with remarkable physical properties for microprocessor cooling. Detailed investigations were conducted using a full-scale heat sink model to understand the inner geometric structure, flow, and heat transfer characteristics within a gyroid heat sink (GHS). The thermo-hydraulic performance of the GHS design was systematically assessed against that of a pinfin heat sink (PHS) across different porosities and flow rates. Both heat sinks were evaluated under non-uniform heating conditions, considering three heating schemes, each with eleven randomly distributed hotspots. The thermohydraulic performance was assessed by calculating temperature non-uniformity, thermal resistance, and pumping power. A correlation was established using the cell size and cell wall thickness of a unit cell of gyroid TPMS to calculate its hydraulic diameter. The analysis revealed that the enhanced thermal performance of the GHS design can be attributed to its intricate and convoluted flow structure, along with a significantly large heat transfer surface area. However, these same factors contribute to a notably high-pressure drop. Compared to the PHS design, the GHS design showed better thermal performance at all the selected porosities and flow rates, albeit with higher pumping powers. The GHS design showed improvement in the thermal performance as the porosity decreased. Investigation under heterogeneous heating conditions showed substantially lower temperatures at the hotspots in the GHS design, along with reduced temperature variation among them. The study's findings provide valuable insight into the advantages and drawbacks of gyroid TPMS structure for their application in electronic cooling.
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| 11. |
- Arfan, Muhammad, et al.
(författare)
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Life cycle assessment and life cycle costing of hydrogen production from biowaste and biomass in Sweden
- 2023
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 291
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Tidskriftsartikel (refereegranskat)abstract
- In this study, an environmental and economic assessment of hydrogen production from biowaste and biomass is performed from a life cycle perspective, with a high degree of primary life cycle inventory data on materials, energy, and investment flows. Using SimaPro LCA software and CML-IA, 2001 impact assessment method, ten environmental impact categories are analyzed for environmental analysis. Economic analysis includes capital and operational expenditures and monetization cost of life cycle environmental impacts. The hydrogen production from biowaste has a high climate impact, photochemical oxidant, and freshwater eutrophication than biomass while it performs far better in ozone depletion, terrestrial ecotoxicity, abiotic depletion-fossil, abiotic depletion, human toxicity, and freshwater ecotoxicity. The sensitivity analysis of LCA results indicates that feedstock to biogas/pyrolysis-oil yields ratio and the type of energy source for the reforming process can significantly influence the results, particularly climate change, abiotic depletion, and human toxicity. The life cycle cost (LCC) of 1 kg hydrogen production has been accounted as 0.45–2.76 € with biowaste and 0.54–3.31 € with biomass over the plant's lifetime of 20 years. From the environmental impacts of climate change, photochemical oxidant, and freshwater eutrophication hydrogen production from biomass is a better option than biowaste while from other included impact categories and LCC perspectives it’s biowaste. This research contributes to bioresources to hydrogen literature with some new findings that can be generalized in Europe and even globally as it is in line with and endorse existing theoretical and simulation software-based studies.
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| 12. |
- Assefa, Getashew, et al.
(författare)
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Technology assessment of thermal treatment technologies using ORWARE
- 2005
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 46:5, s. 797-819
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Tidskriftsartikel (refereegranskat)abstract
- A technology assessment of thermal treatment technologies for wastes was performed in the form of scenarios of chains of technologies. The Swedish assessment tool, ORWARE, was used for the assessment. The scenarios of chains of thermal technologies assessed were gasification with catalytic combustion, gasification with flame combustion, incineration and landfilling. The landfilling scenario was used as a reference for comparison. The technologies were assessed from ecological and economic points of view. The results are presented in terms of global warming potential, acidification potential, eutrophication potential, consumption of primary energy carriers and welfare costs. From the simulations, gasification followed by catalytic combustion with energy recovery in a combined cycle appeared to be the most competitive technology from an ecological point of view. On the other hand, this alternative was more expensive than incineration. A sensitivity analysis was done regarding electricity prices to show which technology wins at what value of the unit price of electricity (SEK/kW h). Within this study, it was possible to make a comparison both between a combined cycle and a Rankine cycle (a system pair) and at the same time between flame combustion and catalytic combustion (a technology pair). To use gasification just as a treatment technology is not more appealing than incineration, but the possibility of combining gasification with a combined cycle is attractive in terms of electricity production. This research was done in connection with an empirical R&D work on both gasification of waste and catalytic combustion of the gasified waste at the Division of Chemical Technology, Royal Institute of Technology (KTH), Sweden.
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| 13. |
- Ayele, Getnet Tadesse, et al.
(författare)
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Optimal heat and electric power flows in the presence of intermittent renewable source, heat storage and variable grid electricity tariff
- 2021
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- To decarbonize and increase the flexibility in the heating and electricity sectors, large heat pumps, combined heat and power plants, renewables and storage technologies are increasingly being installed. This results in a tighter coupling between the electricity and heat distribution networks. Hence, the two networks need to be operated in an integrated way so that their synergies can be exploited. The main challenge in that regard is the lack of suitable tools that can capture the detailed operating parameters of both networks simultaneously. This paper proposes a population-based optimal power flow model for integrated heat and electricity distribution networks. An extended energy hub approach is used to model the components of the integrated energy system in a modular form. Active and reactive power balances, heat power balance and optimal management of storage technologies in the presence of intermittent renewables and variable tariffs are considered. The proposed method is then tested using a case study of highly coupled electricity and heat distribution networks consisting of a heat pump, a gas boiler, a combined heat and power plant, a wind turbine and a thermal storage together with a variable electricity tariff. It is found that above 97% of the surplus production from the wind power plant is effectively used in the system and 10.35% of the heat demand is effectively shifted from the peak hours to the cheap-electricity hours. The results show that the proposed method can be used as a decision support tool that can be used for the optimal integration of heat and electricity distribution networks. It also maximizes the synergy that can be captured from the multi-energy systems in general and from the heat and electricity distribution networks in particular.
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| 14. |
- Azimoh, Chukwuma Leonard, et al.
(författare)
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Electricity for development: : Mini-grid solution for rural electrificationin South Africa
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; :110, s. 268-277
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Tidskriftsartikel (refereegranskat)abstract
- The objective of most rural electrification programs in the developing world is to bring about socioeconomicdevelopment to households. Governments have put in place a number of measures to achievethis goal. Previous studies on rural electrification programs in developing countries show that solar homesystems and mini-grid systems are the dominant technologies. Assessments of a pilot hybrid mini-gridproject at Lucingweni village have concluded that mini-grid projects are not feasible due to high electricityproduction costs. As a result efforts toward rural electrification have been focused on the solar homesystem. Nevertheless, previous studies of the South African solar home system program have shown thatthe development objectives of the program are yet to be met more than a decade after commissioning.Therefore, this study investigates the viability of a hybrid mini-grid as a solution for rural developmentin South Africa. Investigations were based on Lucingweni and Thlatlaganya, two rural Villages where themini-grid and solar home system have been introduced. The mini-grid systems were designed taking intoconsideration available natural resources and existing load profiles. The results show that a village of 300households needs about 2.4 kW h/household/day of electricity to initiate and sustain income generatingactivities and that the solar home system is not capable of supporting this level of demand. We also showthat in locations with hydro resources, a hybrid mini-grid system has the most potential for meeting theenergy needs of the households in a cost effective manner. The assessment shows that with adequateplanning and optimization of available resources, the cost of electricity production can be reduced.
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| 15. |
- Baldi, Francesco, 1986, et al.
(författare)
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Optimal load allocation of complex ship power plants
- 2016
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 124, s. 344-356
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Tidskriftsartikel (refereegranskat)abstract
- In a world with increased pressure on reducing fuel consumption and carbon dioxide emissions, thecruise industry is growing in size and impact. In this context, further effort is required for improvingthe energy efficiency of cruise ship energy systems.In this paper, we propose a generic method for modelling the power plant of an isolated system withmechanical, electric and thermal power demands and for the optimal load allocation of the different componentsthat are able to fulfil the demand.The optimisation problem is presented in the form of a mixed integer linear programming (MINLP)problem, where the number of engines and/or boilers running is represented by the integer variables,while their respective load is represented by the non-integer variables. The individual components aremodelled using a combination of first-principle models and polynomial regressions, thus making thesystem nonlinear.The proposed method is applied to the load-allocation problem of a cruise ship sailing in the Baltic Sea,and used to compare the existing power plant with a hybrid propulsion plant. The results show thebenefits brought by using the proposing method, which allow estimating the performance of the hybridsystem (for which the load allocation is a non-trivial problem) while also including the contribution ofthe heat demand. This allows showing that, based on a reference round voyage, up to 3% savings couldbe achieved by installing the proposed system, compared to the existing one, and that a NPV of11 kUSD could be achieved already 5 years after the installation of the system.
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| 16. |
- Bastholm, Caroline, et al.
(författare)
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Techno-economic study of the impact of blackouts on the viability of connecting an off-grid PV-diesel hybrid system in Tanzania to the national power grid
- 2018
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 171:1, s. 647-658
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Tidskriftsartikel (refereegranskat)abstract
- National electrification plans for many countries with a low level of electrification promote the implementation of centralized and decentralized electrification in parallel. This paper explores different ways of utilizing an established off-grid PV-diesel hybrid system when the national grid becomes available. This is a rather unique starting point within the otherwise well-explored area of rural electrification. With particular focus on the impact of blackouts in the national grid, we evaluate the economic viability of some alternatives: to continue to use the off-grid micro-grid, to connect the existing micro-grid with or without battery backup to the national grid, or to use the national grid only. Our simulation results in HOMER demonstrate that with a grid without blackouts, there are few benefits to maintain the existing system. Low grid-connection fees, low tariffs and low revenues from selling excess electricity to the grid contribute to this result despite the fact that the system does not carry any investment costs. With a grid with blackouts, it is beneficial to maintain the system. The extent of blackouts and the load on the system determine which system configuration is most feasible. The results make clear the importance of taking blackouts in the national grid into consideration when possible system configurations are being evaluated. This is rarely quantified in studies comparing different electrification alternatives, but deserves more attention.
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| 17. |
- Behzadi, Amirmohammad, et al.
(författare)
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A comparative evaluation of alternative optimization strategies for a novel heliostat-driven hydrogen production/injection system coupled with a vanadium chlorine cycle
- 2022
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 267, s. 115878-
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Tidskriftsartikel (refereegranskat)abstract
- This paper introduces an innovative and cost-effective multi-generation plant, driven by the central receiverbased concentrated solar systems, to facilitate the desired global green-transition process. The vanadium chlorine thermochemical cycle, which uses hydrogen instead of natural gas in the combustion chamber, is used as an innovative approach for reducing greenhouse gas emissions. The proposed system also includes a thermoelectric generator (TEG) for excess power generation and a multi-effect desalination (MED) unit to reduce exergy loss. The suggested system's technological, economic, and environmental metrics are analyzed and compared to a similar system that stores the created hydrogen rather than burning it in the combustion chamber. Furthermore, the viability of the studied model is investigated under the optimal operating condition, using the example of Sevilla in order to make the conclusions more reliable. According to the findings, the suggested novel configuration is a better alternative in terms of cost and environmental impact owing to decreased product energy costs and CO2 emissions. The outcomes further indicate that the substitution of the condenser with TEG leads to considerably higher power production. According to the optimization findings, the multi-objective grey wolf algorithm is the best optimization strategy compared to the non-dominated genetic and particle swarm approaches. At the best optimization point, 2.5% higher exergy efficiency, 1 $/GJ cheaper product energy cost, and 0.12 kg/kWh lower levelized CO2 emission are achieved compared to the operating condition. The Sankey diagram indicates that the solar heliostat system has the highest irreversibility. The exergy analysis results further reveal that the flue gas condensation process through the Rankine cycle and MED unit lead to a 53.2% reduction in exergy loss. Finally, considerable CO2 emission reductions show that the suggested new method is an effective solution for cleaner energy production in warmer climate countries.
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| 18. |
- Behzadi, Amirmohammad, et al.
(författare)
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A rule-based energy management strategy for a low-temperature solar/ wind-driven heating system optimized by the machine learning-assisted grey wolf approach
- 2023
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 277, s. 116590-
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Tidskriftsartikel (refereegranskat)abstract
- This work presents an innovative, practical, and cost-effective solution for advancing state-of-the-art intelligent building energy systems and aiding the intended worldwide green transition with maximum renewable inte-gration. The vanadium chloride cycle, electrolyzer unit, and Alkaline fuel cell are powered by the sun's and wind's energy to produce/store/use hydrogen. A rule-based control scheme is designed to provide a sophisticated interplay between the demand/supply sides, components, and local energy networks to reduce peak capacity, lower emissions, and save energy costs. TRNSYS is used to analyze and compare the techno-economic-environmental indicators of the conventional system and the suggested smart model for a multi-family build-ing in Sweden. A grey wolf method is built in MATLAB with the help of machine learning to determine the optimum operating state with the maximum accuracy and the least amount of computational time. The results reveal that the suggested smart model considerably saves energy and money compared to the conventional system in Sweden while lowering CO2 emissions. According to the optimization results, the grey wolf optimizer and machine learning techniques enable greater total efficiency of 13 %, higher CO2 mitigation of 8 %, a larger cost saving of 38 %, and a reduced levelized energy cost of 41 $/MWh. The scatter distribution of important design parameters shows that altering the fuel cell current and electrode area considerably impacts the system's performance from all angles. The bidirectional connection of the proposed smart system with the heating and electrical networks through the rule-based controller demonstrates that it can supply the building's energy re-quirements for more than 300 days of the year. Eventually, the major contribution of the vanadium chloride cycle in the summer and the electrolyzer in the winter to the creation of hydrogen highlights the significance of renewable hybridization in reducing the dependence of buildings on energy networks.
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| 19. |
- Behzadi, Amirmohammad, et al.
(författare)
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Supply-demand side management of a building energy system driven by solar and biomass in Stockholm : A smart integration with minimal cost and emission
- 2023
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Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 292
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Tidskriftsartikel (refereegranskat)abstract
- As part of the transition to a sustainable future, energy-efficient buildings are needed to secure users' comfort and lower the built environment's energy footprint and associated emissions. This article presents a novel, realistic and affordable solution to minimize the footprint of smart building energy systems and enable higher renewable energy use in the building sector. For this, an intelligent system is being developed using a rule-based automation approach that considers thermal comfort, energy prices, meteorological data, and primary energy use. In order to lower the installation cost and part of the environmental footprint, batteries are not used, and the heat pump's size is decreased via component integration. Also, different renewable resources are effectively hybridized using photovoltaic thermal panels and an innovative biomass heater to increase the share of renewable energy, enhance reliability, and shave peak load. In order to secure feasibility, the suggested framework is assessed from the techno-economic and environmental standpoints for 100 residential apartments in Stockholm, Sweden. Our results show that 70.8 MWh of renewable electricity is transferred to the local grid, and the remaining 111.5 MWh is used to supply the building's needs and power the electrically-driven components. The biomass heater meets more than 65% of the space heating demand, mainly at low solar power and high electricity prices, illustrating the value of integration strategies to reduce the system's dependability on the local grid. The results further reveal that most energy purchases during the cloudy days and nights are repaid through the sale of excess renewable production during the warmer hours, with a bidirectional connection with the grid. The monthly energy cost is less than 140 $/MWh for most of the years. The cost can be held low due to the exclusion of batteries and minimizing the heat pump size. The proposed system has a low emission index of 11.9 kgCO2/MWh and can reduce carbon dioxide emissions by 70 TCO2/year compared to using the supply from the Swedish energy mix.
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| 20. |
- Bjurström, Johan, et al.
(författare)
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Tunable spring balanced magnetic energy harvester for low frequencies and small displacements
- 2022
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Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 259
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a novel concept to efficiently harvest vibrational energy at low frequencies and very small displacement. We describe and evaluate an electromagnetic energy harvester which generates power from a magnetic circuit with motion induced variations of an air gap. External vibrations induce oscillations of the gap length around an equilibrium point, due to a linear spring counteracting the magnetic force. The relative position of the spring can be adjusted to optimize the harvester output for excitation amplitude and frequency. A simulation model is built in COMSOL and verified by comparison with lab measurements. The simulation model is used to determine the potential performance of the proposed concept under both harmonic and non-harmonic excitation. Under harmonic excitation, we achieve a simulated RMS load power of 26.5 μW at 22 Hz and 0.028 g acceleration amplitude. From a set of comparable EH we achieve the highest theoretical power metric of 1712.2 µW/cm3/g2 while maintaining the largest relative bandwidth of 81.8%. Using measured non-harmonic vibration data, with a mean acceleration of 0.039 g, resulted in a mean power of 52 μW. Moreover, the simplicity and robustness of our design makes it a competitive alternative for use in practical situations.
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| 21. |
- Bolívar Caballero, José Juan, et al.
(författare)
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Advanced application of a geometry-enhanced 3D-printed catalytic reformer for syngas production
- 2023
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 287
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Tidskriftsartikel (refereegranskat)abstract
- Catalyst research on reforming processes for syngas production has mainly focused on the active metals and support materials, while the effect of the catalyst's geometry on the reforming reactions has been poorly studied. The application of 3D-printed materials with enhanced geometries has recently started to be studied in heterogeneous catalysis and is of interest to be implemented for reforming biomass and plastic waste to produce H2-rich syngas. In this study, a geometry-enhanced 3D-printed Ni/Al2O3/FeCrAl-based monolithic catalyst with a periodic open cellular structure (POCS) was designed and fabricated. The catalyst was used for batch steam reforming biomass pyrolysis volatiles for syngas production at different parameters (temperature and steam-to-carbon ratio). The results showed complete reforming of pyrolysis volatiles in all experimental cases, a high H2 yield of ≈ 7.6 wt% of biomass was obtained at the optimized steam-to-carbon ratio of 8 and a reforming temperature of 800 °C, which is a higher yield compared to other batch reforming tests reported in the literature. Moreover, CFD simulation results in COMSOL Multiphysics demonstrated that the POCS configuration improves the reforming of pyrolysis volatiles for tar/bio-oil reforming and H2 production thanks to enhanced mass and heat transfer properties compared to the regular monolithic single-channel configuration.
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| 24. |
- Broberg, Sarah, et al.
(författare)
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Biogas production supported by excess heat - A systems analysis within the food industry
- 2015
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Ingår i: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 91, s. 249-258
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper was to study the effects on greenhouse gases and economics when a change is made in the use of industrial organic waste from external production and use of biogas (A) to internal production and use (B). The two different system solutions are studied through a systems analysis based on an industrial case. The baseline system (A) and a modified system (B) were compared and analysed. Studies show that industrial processes considered as integrated systems, including the exchange of resources between industries, can result in competitive advantages. This study focuses on the integration of internally produced biogas from food industry waste produced by a food company and the use of excess heat. Two alternative scenarios were studied: (1) the use of available excess heat to heat the biogas digester and (2) the use of a part of the biogas produced to heat the biogas digester. This study showed that the system solution, whereby excess heat rather than biogas is used to heat the biogas digester, was both environmentally and economically advantageous. However, the valuation of biomass affects the magnitude of the emissions reduction. Implementing this synergistic concept will contribute to the reaching of European Union climate targets. (C) 2014 Elsevier Ltd. All rights reserved.
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| 25. |
- Broberg Viklund, Sarah, 1983-, et al.
(författare)
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Technologies for utilization of industrial excess heat : Potentials for energy recovery and CO2 emission reduction
- 2014
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 77, s. 369-379
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Tidskriftsartikel (refereegranskat)abstract
- Industrial excess heat is a large untapped resource, for which there is potential for external use, which would create benefits for industry and society. Use of excess heat can provide a way to reduce the use of primary energy and to contribute to global CO2 mitigation. The aim of this paper is to present different measures for the recovery and utilization of industrial excess heat and to investigate how the development of the future energy market can affect which heat utilization measure would contribute the most to global CO2 emissions mitigation. Excess heat recovery is put into a context by applying some of the excess heat recovery measures to the untapped excess heat potential in Gavleborg County in Sweden. Two different cases for excess heat recovery are studied: heat delivery to a district heating system and heat-driven electricity generation. To investigate the impact of excess heat recovery on global CO2 emissions, six consistent future energy market scenarios were used. Approximately 0.8 TWh/year of industrial excess heat in Gavleborg County is not used today. The results show that with the proposed recovery measures approximately 91 GWh/year of district heating, or 25 GWh/year of electricity, could be supplied from this heat. Electricity generation would result in reduced global CO2 emissions in all of the analyzed scenarios, while heat delivery to a DH system based on combined heat and power production from biomass would result in increased global CO2 emissions when the CO2 emission charge is low.
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