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1.	Börjesson, Pål, et al. (författare) Regional Production and Utilisation of Biomass in Sweden 1996 Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 21:9, s. 747-764 Tidskriftsartikel (refereegranskat)abstract Regional production and utilization of biomass in Sweden is analysed, considering the potential of replacing fossil fuels and producing new electricity. Extensive utilization of biomass will decrease biomass-transportation distances. The average distance for biomass transportation to a large-scale conversion plant suitable for electricity or methanol production will be 30–42 km when the conversion plant is located in the centre of the biomass production area. The total energy efficiency of biomass production and transportation will be 95–97% and the emissions of air pollutants will be small. In areas where energy crops from agriculture constitute the main part of the biomass, the transportation distance will be two to three times shorter than in areas where logging residues from forestry dominate. When present Swedish fossil-fuel use for heat and electricity production is replaced, more than 75% of the biomass required can be produced locally within the county. The average transportation distance of the remaining part will be between 130 and 240 km, increasing the cost of this biomass by 15–20%. Increased use of biomass by 430 PJ/yr, the estimated potential for increased utilization of energy crops, logging residues and straw, will lead to an excess of about 200 PJ/yr biomass after fossil fuels for electricity and heat production have been replaced. This biomass could be used for methanol or electricity production. The production of biomass-based methanol will lead to a low demand for transportation, as the methanol produced from local biomass can mainly be used locally to replace petrol and diesel. If the biomass is used for electricity production, however, the need for transportation will increase if the electricity is cogenerated in district heating systems, as such systems are usually located in densely populated areas with a deficit of biomass. About 60% of the biomass used for cogenerated electricity must be transported, on average, 230 km. Changing transportation mode when transporting biomass over large distances, compared with short distances, however, will lead to rather low specific transportation costs and environmental impact, as well as high energy efficiency. Replacing fossil fuels with biomass for heat and electricity production is typically less costly and leads to a greater reduction in CO2 emission than substituting biomass for petrol and diesel used in vehicles. Also, cogeneration of electricity and heat is less costly and more energy efficient than separate electricity and heat production.
2.	Christiansson, Lena (författare) Time Dynamics of Electricity Demand in Air-Distribution Systems for Commercial Buildings in Sweden 1996 Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 21:10, s. 879-888 Tidskriftsartikel (refereegranskat)abstract This paper illustrates the potential for reducing future electricity demand for air distribution in commercial buildings in Sweden. We have developed a general, quantitative, scenario-based framework to describe electricity demand for air distribution and to analyze how governmental and utility-sponsored policy measures affect electricity demand. The results suggest that higher electricity prices will not be very effective in reducing electricity demand, whereas significant electricity savings can be achieved by implementing desirable policy programs.
3.	Gustavsson, Leif, et al. (författare) Heating Detached Houses in Urban Areas 2003 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 28:8, s. 851-875 Tidskriftsartikel (refereegranskat)abstract District heating systems using cogeneration, as well as local fuel-based and electric heating systems for detached houses, are analysed. The analysis includes the whole energy system, from the natural resource to the end user, with respect to primary energy use, emission and cost. The end-use technologies studied are heat pumps, resistance heaters and boilers. It was assumed that the base-load electricity, except for the cogenerated electricity, was produced in stand-alone power plants using wood chips or natural gas, while peak-load electricity and fuel used for transportation were produced from crude oil. The heat pump and district heating systems are found to be most energy efficient, followed by the local fuel-based systems. The wood-fuel-based systems emit about one tenth of the greenhouse gases emitted by the natural-gas-based systems. The sulphur and nitrogen oxide emission, however, is higher for wood-fuel-based systems. Systems based on natural gas are less expensive than the corresponding wood-fuel-based systems. Decarbonization and carbon dioxide sequestration, however, do not reduce the carbon dioxide emission to the low level of the wood-fuel-based systems and, in addition, make the natural-gas-based systems more expensive than the wood-fuel-based systems.
4.	Johansson, Bengt, et al. (författare) Energy and environmental costs for electric vehicles using CO2-neutral electricity in Sweden 2000 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 25:8, s. 777-792 Tidskriftsartikel (refereegranskat)abstract Electric vehicles (EVs) may provide an alternative for CO2-neutral transportation services. This article analyses the cost of energy and emissions from using electricity produced from Swedish renewable energy sources in electric vehicles, and compares it with the cost of an alternative in which biomass-based methanol is used in internal combustion engine vehicles (ICEVs). These costs do not include vehicle and battery costs. Cost estimates of electricity, calculated using a marginal cost perspective, include production costs as well as the cost of distribution and vehicle recharging. The energy cost per km for vehicles using electricity is calculated to be 30-70% of the cost of biomass-based methanol, depending on the general level of electricity demand, the need for grid upgrading, and the assumed cost of biomass-based methanol. A high general electricity demand in society would require expensive condensing plants to supply the vehicles, whereas with a lower demand, cheaper cogeneration and wind power plants could be utilised. An electric vehicle, used as the average Swedish car, would, during its lifetime, have energy and environmental costs 30 000-40 000 SEK ($4000-5400) lower than the current state-of-the art ICEVs using biomass-based methanol. An electric vehicle used mainly in the city centre might have energy and environmental costs which are 130 000-140 000 SEK ($17 000-19 000) lower than a current methanol-fuelled car. With future improvements in the energy efficiency and environmental performance of ICEVs the difference will be significantly reduced. If battery costs were included in the cost calculations, EVs would not be cost competitive with future ICEVs, even if battery costs are reduced to $100/kWh. (C) 2000 Elsevier Science Ltd. All rights reserved.Electric vehicles (EVs) may provide an alternative for CO2-neutral transportation services. This article analyses the cost of energy and emissions from using electricity produced from Swedish renewable energy sources in electric vehicles, and compares it with the cost of an alternative in which biomass-based methanol is used in internal combustion engine vehicles (ICEVs). These costs do not include vehicle and battery costs. Cost estimates of electricity, calculated using a marginal cost perspective, include production costs as well as the cost of distribution and vehicle recharging. The energy cost per km for vehicles using electricity is calculated to be 30-70% of the cost of biomass-based methanol, depending on the general level of electricity demand, the need for grid upgrading, and the assumed cost of biomass-based methanol. A high general electricity demand in society would require expensive condensing plants to supply the vehicles, whereas with a lower demand, cheaper cogeneration and wind power plants could be utilized. An electric vehicle, used as the average Swedish car, would, during its lifetime, have energy and environmental costs 30 000-40 000 SEK ($4000-5400) lower than the current state-of-the art ICEVs using biomass-based methanol. An electric vehicle used mainly in the city centre might have energy and environmental costs which are 130 000-140 000 SEK ($17 000-19 000) lower than a current methanol-fuelled car. With future improvements in the energy efficiency and environmental performance of ICEVs the difference will be significantly reduced. If battery costs were included in the cost calculations, EVs would not be cost competitive with future ICEVs, even if battery costs are reduced to $100/kWh.
5.	Johansson, Bengt (författare) Will Swedish Biomass be Sufficient for Future Transportation Fuel Demands? 1996 Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 21:12, s. 1059-1069 Tidskriftsartikel (refereegranskat)abstract There is a potential to increase the annual use of biomass in Sweden by 125 TWh between 1994 and 2015. 125 TWh of biomass would satisfy most of the transportation-fuel demand in Sweden in 2015. Even if the biomass is primarily used for heat and electricity production, a significant fraction will be available for transportation-fuel production, if other non-fossil energy sources are utilized for electricity production and/or substantial energy-efficiency improvements are realized. Improved energy efficiency and the use of renewable energy sources will be required in all sectors to achieve CO2 emission reductions greater than 50%.
6.	Andersson, Maria, 1965- (författare) Shadow prices for heat generation in time-dependent and dynamic energy systems 1994 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 19:12, s. 1205-1211 Tidskriftsartikel (refereegranskat)abstract Shadow prices for heat generation are used to study the impact of changes in heat demand on the total system cost of an existing district-heating system in Sweden. The energy system may be considered to be both dynamic, because there is energy storage, and time-dependent since the electricity tariff is time-differentiated and the heat demand varies over the year and day. The energy system has been analysed with and without energy storage. The analysis shows that despite a reduction in system cost, the use of energy storage can result in higher shadow prices for heat generation in some time periods.
7.	Dai, X W, et al. (författare) Pyrolysis of waste tires in a circulating fluidized-bed reactor 2001 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 26:4, s. 385-399 Tidskriftsartikel (refereegranskat)abstract Using a circulating fluidized bed (CFB) as the main reactor, an integrated process development unit was operated aiming at the pyrolysis of waste tires. The main chemical processes in the CFB can be divided into two zones corresponding to pyrolysis and secondary reactions. The pyrolysis of tire powder was carried out at various pyrolysis temperatures, particle sizes of tire powder and feed positions. The effects of temperature, residence time and heating rate on pyrolysis were analyzed based on the experimental data. The main trends are that (1) a long residence time contributes to secondary reactions and (2) lower temperature and heating rate favor carbonization, which reduces the oil yield. Analysis of the pyrolytic oil shows that the predominant components are aromatics, followed by alkanes, non-hydrocarbons and asphalt.
8.	Gong, Mei (författare) Optimization of industrial energy systems by incorporating feedback loops into the MIND method 2003 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 28:15, s. 1655-1669 Tidskriftsartikel (refereegranskat)abstract The MIND (Method for analysis of INDustrial energy system) method has been developed for multi-period cost optimization of industrial energy systems. Existing industrial processes can be represented at the desired level of accuracy, i.e. one modeling unit may represent a part of the production process or the whole plant. The optimization method includes both energy and material flows. Nonlinear relations, energy conversion efficiencies and investment costs are linearized by mixed-integer linear programming. A flexible time-scale facilitates the performance of long- and short-term analyses. In order to meet the requirements with regard to sustainable development, the recycling of energy and material flows is becoming more common in many industrial processes. The recycling or reuse of energy and material is managed by feedback loops, which are incorporated into the original MIND method to improve the model and reduce the calculation time. The improved MIND/F method (MIND method with feedback loops) model is applied to a pulp and paper mill in Sweden. A comparison between the original MIND method with manual handling of the feedback loops and the MIND/F method gives highly satisfactory results. Cost optimization using the improved MIND method is well within the given accuracy and computer time and manual calculation time are both reduced considerably. The reuse of energy and material resources is not only an economic advantage, but also implies a reduction of the environmental impact.
9.	Gustafsson, Stig-Inge, et al. (författare) Factorial design for energy System Models 1994 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 19:8, s. 905-910 Tidskriftsartikel (refereegranskat)abstract Mathematical models are extensively used in energy analysis and have increased in scope as better and faster computers have become available. With complicated systems, it is difficult to predict accurate results if doubtful input data are changed. Traditionally, sensitivity analysis with a change of one or more of the parameters is used. If the influence of a change is very small, the first result is believed to be accurate. Problems may arise when sensitivity analysis is applied to a vast amount of data. The aim of this paper is to examine whether the calculation effort can be decreased by using factorial design. Our model, called Opera (Optimal Energy Retrofit Advisory), is used to find the optimal retrofit strategy for a multi-family building. The optimal solution is characterised by the lowest possible life-cycle cost. Three parameters have been studied here: length of the optimisation period, real interest rate and existing U-value for an attic floor. The first two parameters are found to influence the life-cycle cost significantly, while the last is of minor importance for this cost. We also show that factorial analysis must be used with great care because the method does not reflect the complete situation.
10.	Gustafsson, Stig-Inge, et al. (författare) Natural gas in Optimized Bivalent Heating Sytems 1990 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 15:11, s. 993-999 Tidskriftsartikel (refereegranskat)abstract In accordance with a public referendum held in 1980, Sweden will phase out nuclear power completely by 2010. One way to compensate for an immediate, appreciable scarcity of electric power is to construct new fossil-fuel power stations. Another is to reduce the burden on electric power by converting some end-user facilities to operate on natural gas (NG) imported from Denmark through a new pipeline to southern Sweden. We show how an optimal solution can be found for NG operation of a system incorporating an NG boiler and an electric heat pump. Electricity is priced by a time-of-use tariff (TOU) requiring a discrete optimization method. The optimal solution is characterized by the lowest life cycle cost (LCC) for the building as an energy system.
11.	Gustafsson, Stig-Inge, et al. (författare) Optimal heating-system retrofits in residential buildings 1997 Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 22:9, s. 867-874 Tidskriftsartikel (refereegranskat)abstract The optimal heating-system-retrofit strategy for existing buildings differs due to varying prices of energy, building and installation features, climate conditions, etc. We have examined a test building situated in Linköping, Sweden. By using the OPERA model, we were able to arrive at the optimal retrofit strategy, which includes a ground-coupled heat pump using electricity to run the compressor. Unfortunately, the price of electricity differs according to the time of day, month, etc. These variations are not included in the OPERA model. In OPERA, the price should be divided into 12 segments, one for each month of the year since climate data are divided in this manner. Fine tuning of a dual-fuel system (an oil-fired boiler handles the peak load and a heat pump the base thermal load) is optimized using the Mixed Integer Linear Programming (MILP) method. Adding a hot-water accumulator also makes it possible to use low electricity prices for space and domestic hot-water heating. This system competes in the model with traditional heating devices such as district heating. The optimal method of heating the building was found for using the heat pump alone.
12.	Gustavsson, Leif, et al. (författare) CO2 Mitigation Costs of Large-scale Bioenergy Technologies in Competitive Electricity Markets 2003 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 28:14, s. 1405-1425 Tidskriftsartikel (refereegranskat)abstract In this study, we compare and contrast the impact of recent technological developments in large biomass-fired and natural-gas-fired cogeneration and condensing plants in terms of CO2 mitigation costs and under the conditions of a competitive electricity market. The CO2 mitigation cost indicates the minimum economic incentive required (e.g. in the form of a carbon tax) to equal the cost of a less carbon extensive system with the cost of a reference system. The results show that CO2 mitigation costs are lower for biomass systems than for natural gas systems with decarbonization. However, in liberalized energy markets and given the socio-political will to implement carbon extensive energy systems, market-based policy measures are still required to make biomass and decarbonization options competitive and thus help them to penetrate the market. This cost of cogeneration plants, however, depends on the evaluation method used. If we account for the limitation of heat sinks by expanding the reference entity to include both heat and power, as is typically recommended in life-cycle analysis, then the biomass-based gasification combined cycle (BIG/CC) technology turns out to be less expensive and to exhibit lower CO2 mitigation costs than biomass-fired steam turbine plants. However, a heat credit granted to cogeneration systems that is based on avoided cost of separate heat production, puts the steam turbine technology despite its lower system efficiency at an advantage. In contrast, when a crediting method based on avoided electricity production in natural-gas-fired condensing plants is employed, the BIG/CC technology turns out to be more cost-competitive than the steam turbine technology for carbon tax levels beyond about $ 150/t C. Furthermore, steam turbine plants are able to compete with natural-gas-fired cogeneration plants at carbon tax levels higher than about $ 90/t C.
13.	Johansson, Lars, et al. (författare) An open absorption system installed at a sawmill : Description of pilot plant used for timber and bio-fuel drying 2000 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 25:11, s. 1067-1079 Tidskriftsartikel (refereegranskat)abstract This work describes a pilot plant and its different parts in a system used for bio-fuel drying and timber drying with an open absorption process. This technique has not been used previously in Sweden in this application. The open absorption system has been installed on four timber dryers and one bio-fuel dryer at a sawmill located in the northern part of Sweden. The annual energy demand for the dryers has decreased considerably. The specific heat demand for a conventional drying system is about 5970 kJ/kg of evaporated water. For the open absorption system, the corresponding value is a heat demand of approximately 1400 kJ/kg of evaporated water. At the same time, an additional 360 kJ/kg of electricity has to be supplied. Here, 45,000 m3 per year of dried bio-fuel has been sold on the market as a result of the decreased heat demand in the wood dryers at the sawmill. The plant has been working well and has had a high availability. The pay-off time for the investment will be approximately 3 years for nondiscounted cash-flows
14.	Jonsson, M., et al. (författare) Ammonia-water bottoming cycles : a comparison between gas engines and gas diesel engines as prime movers 2001 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 26:1, s. 31-44 Tidskriftsartikel (refereegranskat)abstract Ammonia-water cycles can produce more power than steam Rankine cycles in several applications. One of these applications is as a bottoming cycle to internal combustion engines. In the present study, ammonia-water bottoming cycle configurations for spark-ignition gas engines and compression-ignition gas diesel engines have been compared, Single-pressure Rankine cycles have been used as a basis for the comparison. Low heat source temperatures should increase the difference in power output between the ammonia-water cycle and the Rankine cycle. However, in this study, the results of the simulations show different trends. In most cases, the ammonia-water bottoming cycles with gas engines as prime movers generate more power compared to a Rankine cycle than when gas diesel engines are the prime movers. The temperature of the most important waste heat source, the exhaust gas, is approximately 100 degreesC higher for the gas engines than for the gas diesel engines. Therefore, for the gas engines, most of the waste heat available to a bottoming cycle is in the form of relatively high-temperature exhaust gas, while for the gas diesel engines more of the waste heat is in the form of relatively low-temperature heat sources.
15.	Mollersten, K., et al. (författare) Potential and cost-effectiveness of CO2 reductions through energy measures in Swedish pulp and paper mills 2003 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 28:7, s. 691-710 Tidskriftsartikel (refereegranskat)abstract Using the two criteria of potential CO2 reduction and Cost Of CO2 reduction, technical energy measures in Swedish pulp. and paper mills are investigated. Principal CO2-reducing measures analysed are: decreased specific energy utilisation, fuel switch, and CO2 capture and sequestration. Among the investigated measures, conventional technologies for electricity conservation and improved electrical conversion efficiency in existing systems for cogeneration of heat and power are identified as the most cost-effective alternatives that also have large CO2 reduction potentials. For commercially available technologies, the results indicate an accumulated reduction potential of up to 8 MtCO(2)/y (14% of the Swedish net emissions). If emerging technologies for black liquor gasification (BLG) with pre-combustion CO2 capture and sequestration are considered, the CO2 reduction potential increases by up to 6 MtCO(2)/y (10% of the Swedish net emissions). Commercialised BLG, CO2 capture and reliable CO2 sequestration technologies are identified as important potential contributors to Swedish compliance with Kyoto Protocol targets, especially in a scenario of nuclear power closure.
16.	Möllersten, Kenneth, 1966-, et al. (författare) Potential and cost-effectiveness of CO2-reducing measures in the pulp and paper industry 2003 Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 28:7, s. 691-710 Tidskriftsartikel (refereegranskat)abstract Using the two criteria of potential CO2 reduction and cost of CO2 reduction, technical energy measuresin Swedish pulp and paper mills are investigated. Principal CO2-reducing measures analysed are: decreasedspecific energy utilisation, fuel switch, and CO2 capture and sequestration. Among the investigated measures, conventional technologies for electricity conservation and improved electrical conversion efficiencyin existing systems for cogeneration of heat and power are identified as the most cost-effective alternativesthat also have large CO2 reduction potentials. For commercially available technologies, the results indicatean accumulated reduction potential of up to 8 MtCO2/y (14% of the Swedish net emissions). If emergingtechnologies for black liquor gasification (BLG) with pre-combustion CO2 capture and sequestration areconsidered, the CO2 reduction potential increases by up to 6 MtCO2/y (10% of the Swedish net emissions).Commercialised BLG, CO2 capture and reliable CO2 sequestration technologies are identified as importantpotential contributors to Swedish compliance with Kyoto Protocol targets, especially in a scenario of nuclearpower closure
17.	Sundberg, Gunnel, et al. (författare) Interaction effects in optimising a municipal energy system 2000 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 25:9, s. 877-891 Tidskriftsartikel (refereegranskat)abstract A study is presented where factorial design is used to find how some selected economic and technical factors affect the profitability of an investment in a combined heat and power plant. The study is performed on a Swedish district heating system. The minimal cost for supplying the demanded heat is calculated with a developed energy system optimisation model, MODEST. The effects on the resulting parameters, such as system cost and optimal size of steam cycle, are calculated from a series of experiments performed using high and low levels of the most relevant factors. The conclusion of the study is that both the main factors and the interactions between them have to be analysed to establish an accurate ranking of the technical and economic factors. (C) 2000 Elsevier Science Ltd. All rights reserved.
18.	Toffolo, Andrea, et al. (författare) Evolutionary algorithms for multi-objective energetic and economic optimization in thermal system design 2002 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 27:6, s. 549-567 Tidskriftsartikel (refereegranskat)abstract Thermoeconomic analyses in thermal system design are always focused on the economic objective. However, knowledge of only the economic minimum may not be sufficient in the decision making process, since solutions with a higher thermodynamic efficiency, in spite of small increases in total costs, may result in much more interesting designs due to changes in energy market prices or in energy policies. This paper suggests how to perform a multi-objective optimization in order to find solutions that simultaneously satisfy exergetic and economic objectives. This corresponds to a search for the set of Pareto optimal solutions with respect to the two competing objectives. The optimization process is carried out by an evolutionary algorithm, that features a new diversity preserving mechanism using as a test case the well-known CGAM problem.
19.	Wall, Göran, 1951- (författare) Thermoeconomic Optimization of a Heat Pump System 1986 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 11:10, s. 957-967 Tidskriftsartikel (refereegranskat)abstract We present the application of thermoeconomics to the optimization of a single-stage heat-pump cycle. The method is well suited for application to thermodynamic processes and yields exergy losses. The marginal cost of an arbitrary variable can also be calculated. The efficiencies of the compressor, condenser, evaporator, and electric motor are chosen as decision variables which are to be optimized. Parameters such as the price of electricity and the temperature of the delivered heat may vary among optimizations, and results are presented for different parameter values.
20.	Westerlund, Lars, et al. (författare) Theoretical investigation of the heat demand for public baths 1996 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 21:7-8, s. 731-737 Tidskriftsartikel (refereegranskat)abstract Public baths normally use outdoor air to remove moisture from the building. This procedure results in large heating demands. A theoretical hour-based method for estimation of the heating demand has been developed. The method allows for dynamic behaviour with correct time periods for each mass-transfer level. Results of predictions with this method have been compared with yearly estimates of the heating demand based on actual measurements in a public bath. The difference is 3%. A parametric study shows that the air temperature and relative humidity in the building strongly influence the heating demand. Comparisons with other prediction methods based on use of the duration curve or mean annual outdoor temperature show differences less than 5% from results obtained with the hour-based method. The simpler approaches (use of a duration curve or mean value) fail when minimum outdoor airflow must be considered, as will be the case, for instance, when comparing different energy-saving systems or design of components for the climate system.
21.	Abdelshafy, Alaaeldin M., et al. (författare) Optimized energy management strategy for grid connected double storage (pumped storage-battery) system powered by renewable energy resources 2020 Ingår i: Energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-5442 .- 1873-6785. ; 192 Tidskriftsartikel (refereegranskat)abstract This paper presents a grid-connected double storage system (DSS) consisting of pumped-storage hydropower (PSH) and battery. The system is supplied by photovoltaics and wind turbines. In the proposed hybrid system, batteries absorb excess renewable energy that cannot be stored in PSH and they cover loads that cannot be supplied from the water turbine. To improve the system performance, a novel energy management strategy for the DSS is proposed. The strategy is based on an optimized factor that governs the charging process of the DSS. The problem of the optimal system design is solved by a non-dominated sorting genetic algorithm (NSGA-II). The multi-objective function considers simultaneously the minimal investment cost and minimal CO2 emissions. A comparative study of photovoltaic/wind/pumped-storage hydropower and photovoltaic/wind/double storage system is performed to show the effectiveness of the proposed strategy in terms of system economic and environmental performance. The considered location of the PSH station is on Attaqa Mountain at Suez (Egypt). The results indicate the effectiveness of the proposed energy management strategy for the storage system from economic and environmental perspectives. Coupling the battery with the PSH reduces the electricity cost by 22.2% and results in minimal energy exchange with the national grid (5% of the annual demand). A sensitivity analysis shows the largest variation of the electricity cost with changing the capital cost of the solar and wind generators. Also, it is observed that when the load increases, the optimal size of the system components increases, but it isn't proportional with the demand increase as could be expected. (C) 2019 Elsevier Ltd. All rights reserved.
22.	Adanez-Rubio, Inaki, et al. (författare) Use of a high-entropy oxide as an oxygen carrier for chemical looping 2024 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 298 Tidskriftsartikel (refereegranskat)abstract One mixed oxide with 5 cations in equimolar proportions in the sublattice, to fulfil high-entropy oxide (HEO) criteria, has been developed and investigated as oxygen carrier for chemical looping combustion processes. As far as we know, nobody has explored this class of material for chemical looping combustion. Material is prepared by direct mixing of five metal oxides (CuO, Mn2O3, Fe2O3, TiO2, MgO), followed by calcination at 1000, 1100 and 1200 °C for 6 h in air. XRD characterization provides strong evidence that the synthesized oxygen carriers possess the hallmark properties of HEO, and SEM-EDX analysis shows an overall homogeneous metal distribution. Materials have one main cubic phase with the empirical formula MnCuMgFeTiO7, dominating under all conditions. One of the key objectives of this study is achieved, reduce chemical stress during redox cycles. Oxygen transfer capability is investigated by thermogravimetric analysis and batch fluidized bed reactor experiments for different fuels and atmospheres. Mass-based oxygen transport capacities for lattice oxygen and oxygen uncoupling are around 5.5 wt% and 1.1 wt%, respectively. This work opens up a new dimension for the future preparation of oxygen carriers for chemical looping processes, since the vast compositional space of HEO provides opportunities to tune both chemical and physical characteristics.
23.	Adom, Philip Kofi (författare) Business cycle and economic-wide energy intensity: The implications for energy conservation policy in Algeria 2015 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 88, s. 334-350 Tidskriftsartikel (refereegranskat)abstract Despite the prevalence of voluntary and involuntary energy conservation policies, developing countries in Africa continue to struggle to achieve energy efficiency targets. Consequently, energy intensity levels have risen threatening the security of the energy system. This raises the important question: is there an economic state that induces agents to be energy conscious? In this study, we study the case of Algeria's energy intensity from 1971 to 2010. First, the paper argues that there is a certain economic state that economic agents find investing in energy conservation a viable option. Any state different from that would mean not investing in energy conservation. Second, the paper argues that the economy can do better even with an infinitesimal reduction in fuel subsidy, and that the gains in revenue from the policy can compensate for the negative socio-economic and equity impacts associated with such a policy. Third, the paper argues that, so long as, industrial expansion in the country move parallel with investment in technological innovation, long-term sustainable growth and energy conservation targets are jointly feasible. Fourth, the paper shows that income elasticity evolves with the business cycle, and the absorptive capability of the host country affects how FDI (foreign direct inflows) impact energy intensity. (C) 2015 Elsevier Ltd. All rights reserved.
24.	Adom, Philip Kofi (författare) Determinants of energy intensity in South Africa: Testing for structural effects in parameters 2015 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 89, s. 334-346 Tidskriftsartikel (refereegranskat)abstract A cursory look at South Africa's energy data reveals that, energy intensity has consistently declined for the past two decades. The logical question that ensues is; what might have contributed to this phenomenon? The current study aims to investigate how different phenomena have contributed to the decline in South Africa's energy intensity. The study also tests for structural effects in the model parameters. The result showed that the de-industrialisation since 1980 and the changes in trade structure in favour of more imports have contributed significantly to the decline in energy intensity, in South Africa. Also, the current industry composition has induced technological transfer via FDI (Foreign direct inflows) and this has contributed to the decline in energy intensity levels, in South Africa. The individual effect analyses showed that each of the predictors shared significant amount of variance with the regression effect. Finally, there are significant structural effects in the parameters, and this has rendered the effects of regressors asymmetric. (C) 2015 Elsevier Ltd. All rights reserved.
25.	Ahmad, Waqar, et al. (författare) Benzene conversion using a partial combustion approach in a packed bed reactor 2022 Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 239:Part C Tidskriftsartikel (refereegranskat)abstract This study investigates the partial combustion technique for tar conversion using a modified experimental set up comprising a packed bed reactor with bed-inside probe for air supply. Simulated producer gas (SPG) and benzene were selected as a real producer gas alternative and model tar component respectively. The benzene conversion was investigated under different experimental conditions such as reactor temperature (650–900 °C), packed bed height (0–12 cm), residence time (1.2–1.9 s), air fuel ratio (0.2 and 0.3) and SPG composition. The results showed insignificant effect of temperature over benzene conversion while air fuel ratio of 0.3 caused high benzene conversion than at 0.2. Absence of packed bed lead high benzene conversion of 90% to polyaromatic hydrocarbons (PAHs) compared to similar low PAHs free benzene conversion of 32% achieved at both packed heights. In SPG composition effect, H2 and CH4 had a substantial inverse effect on benzene conversion. An increase in H2 concentration from 12 to 24 vol% increased the benzene conversion from 26 to 45% while an increase in CH4 concentration from 7 to 14 vol% reduced the benzene conversion from 28 to 4%. However, other SPG components had insignificant impacts on benzene conversion.
26.	Aichmayer, Lukas, et al. (författare) Experimental evaluation of a novel solar receiver for a micro gas-turbine based solar dish system in the KTH high-flux solar simulator 2018 Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 159, s. 184-195 Tidskriftsartikel (refereegranskat)abstract This work presents the experimental evaluation of a novel pressurized high-temperature solar air receiver for the integration into a micro gas-turbine solar dish system reaching an air outlet temperature of 800°C. The experiments are conducted in the controlled environment of the KTH high-flux solar simulator with well-defined radiative boundary conditions. Special focus is placed on providing detailed information to enable the validation of numerical models. The solar receiver performance is evaluated for a range of operating points and monitored using multiple point measurements. The porous absorber front surface temperature is measured continuously as it is one of the most critical components for the receiver performance and model validation. Additionally, pyrometer line measurements of the absorber and glass window are taken for each operating point. The experiments highlight the feasibility of volumetric solar receivers for micro gas-turbine based solar dish systems and no major hurdles were found. A receiver efficiency of 84.8% was reached for an air outlet temperature of 749°C. When using a lower mass flow, an air outlet temperature of 800°C is achieved with a receiver efficiency of 69.3%. At the same time, all material temperatures remain below permissible limits and no deterioration of the porous absorber is found.
27.	Aichmayer, Lukas, et al. (författare) Thermo-mechanical solar receiver design and validation for a micro gas-turbine based solar dish system 2020 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 196 Tidskriftsartikel (refereegranskat)abstract This work presents the comprehensive development of a solar receiver for the integration into a micro gas-turbine solar dish system. Special focus is placed on the thermo-mechanical design to ensure the structural integrity of all receiver components for a wide range of operating conditions. For the development, a 3-dimensional coupled multi-physics model is established and is validated using experimental data. Contrary to previous studies, the temperature of the irradiated front surface of the absorber is included in the comprehensive validation process which results in a high level of confidence in the receiver design.Finally, a full-scale solar receiver for the integration into the OMSoP solar dish system is designed and its performance determined for a wide operating range to define its safe operating envelope using the validated model. It is shown that the receiver is capable of operating at 803_C with an efficiency of 82.1% and a pressure drop of 0.3% at the nominal operating point, while at the same time functioning effectively for a wide range of off-design conditions without compromising its structural integrity. At the nominal operating point, the maximum comparison stress of the porous absorber is 5.6 MPa compared to a permissible limit of 7.4 MPa.
28.	Alirahmi, Seyed Mojtaba, et al. (författare) An innovative four-objective dragonfly-inspired optimization algorithm for an efficient, green, and cost-effective waste heat recovery from SOFC 2023 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 263 Tidskriftsartikel (refereegranskat)abstract This work proposes a novel yet practical dragonfly optimization algorithm that addresses four competing ob-jectives simultaneously. The proposed algorithm is applied to a hybrid system driven by the solid oxide fuel cell (SOFC) integrated with waste heat recovery units. A function-fitting neural network is developed to combine the thermodynamic model of the system with the dragonfly algorithm to mitigate the calculation time. According to the optimization outcomes, the optimum parameters create significantly more power and have a greater exergy efficiency and reduced product costs and CO2 emissions compared to the design condition. The sensitivity analysis reveals that while the turbine inlet temperatures of power cycles are ineffective, the fuel utilization factor and the current density significantly impact performance indicators. The scatter distribution indicates that the fuel cell temperature and steam-to-carbon ratio should be kept at their lowest bound. The Sankey graph shows that the fuel cell and afterburner are the main sources of irreversibility. According to the chord diagram, the SOFC unit with a cost rate of 13.2 $/h accounts for more than 29% of the overall cost. Finally, under ideal conditions, the flue gas condensation process produces an additional 94.22 kW of power and 760,056 L/day of drinkable water.
29.	Andersson, Björn A., 1968, et al. (författare) Materials constraints in a global energy scenario based on thin-film solar cells 1998 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 23, s. 407-411 Tidskriftsartikel (refereegranskat)abstract Harnessing solar energy by using photovoltaic cells has the potential to become a major CO2-free energy source. Materials requirements for the solar cells based on four types of thin-film photovoltaics have been estimated and compared with global reserves, resources and annual refining. The use of solar cells based on Cd, Ga, Ge, In, Ru, Se and Te as a major energy-supply technology has severe resource constraints. Other systems such as a-Si without Ge and crystalline silicon do not involve such constraints. For some of these metals, there is the risk of enhanced, environmentally deleterious concentrations in the ecosphere due to leakage from manufacturing, use or waste handling.
30.	Andersson, Eva Ingeborg Elisabeth, 1956, et al. (författare) Comparison of pulp-mill-integrated hydrogen production from gasified black liquor with stand-alone production from gasified biomass 2007 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 32:4, s. 399-405 Tidskriftsartikel (refereegranskat)abstract When gasified black liquor is used for hydrogen production, significant amounts of biomass must be imported. This paper compares two alternative options for producing hydrogen from biomass: (A) pulp-mill-integrated hydrogen production from gasified back liquor; and (B) stand-alone production of hydrogen from gasified biomass. The comparison assumes that the same amount of biomass that is imported in Alternative A is supplied to a stand-alone hydrogen production plant and that the gasified black liquor in Alternative B is used in a black liquor gasification combined cycle (BLGCC) CHP unit. The comparison is based upon equal amounts of black liquor fed to the gasifier, and identical steam and power requirements for the pulp mill. The two systems are compared on the basis of total CO2 emission consequences, based upon different assumptions for the reference energy system that reflect different societal CO2 emissions reduction target levels. Ambitions targets are expected to lead to a more CO2–lean reference energy system, in which case hydrogen production from gasified black liquor (Alternative A) is best from a CO2 emissions’ perspective, whereas with high CO2 emissions associated with electricity production, hydrogen from gasified biomass and electricity from gasified black liquor (Alternative B) is preferable.
31.	Andersson, Eva Ingeborg Elisabeth, 1956, et al. (författare) Energy efficient upgrading of biofuel integrated with a pulp mill 2006 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 31:10-11, s. 1384-1394 Tidskriftsartikel (refereegranskat)abstract This paper presents and evaluates different energy efficient options for integrating drying and pelletising ofbiofuel with a modern energy efficient pulp mill process. When drying biofuel, a large amount of the heat input canoften be recovered. One option for heat recovery is to cover low-temperature heat demand in the pulping process.Alternatively available excess heat from the pulp mill can be used for drying. Both alternatives will contribute to abetter energy efficiency for the combined pulp mill and biofuel upgrading facility. Pinch analysis tools can be usedto estimate the excess heat potential at different temperature levels in the pulp mill. Three different technologies forpulp mill integrated biofuel drying were chosen for the study, namely steam drying, flue gas drying and vacuumdrying. The different technologies are evaluated on the basis of energy usage, global CO2 emissions and resultingpellets production cost, using stand-alone pellets production as a reference. The pulp mill assumed for thecalculations is the Eco-Cyclic reference pulp mill. The results of the study indicate that the most attractiveintegrated drying technology option is the flue gas dryer, using flue gases from the black liquor boiler. With theavailable flue gas stream at the reference pulp mill, a potential pellets production of 70,000 ton/yr could beachieved at a cost of 24.6 EUR/ton. The associated reduction in CO2 emissions compared to stand-alone pelletsproduction is 3136 kg/MWh-pellets.
32.	Andreasen, J. G., et al. (författare) Design and optimization of a novel organic Rankine cycle with improved boiling process 2015 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 91, s. 48-59 Tidskriftsartikel (refereegranskat)abstract In this paper we present a novel organic Rankine cycle layout, named the organic split-cycle, designed for utilization of low grade heat. The cycle is developed by implementing a simplified version of the split evaporation concept from the Kalina split-cycle in the organic Rankine cycle in order to improve the boiling process. Optimizations are carried out for eight hydrocarbon mixtures for hot fluid inlet temperatures at 120 °C and 90 °C, using a genetic algorithm to determine the cycle conditions for which the net power output is maximized. The most promising mixture is an isobutane/pentane mixture which, for the 90 °C hot fluid inlet temperature case, achieves a 14.5% higher net power output than an optimized organic Rankine cycle using the same mixture. Two parameter studies suggest that optimum conditions for the organic split-cycle are when the temperature profile allows the minimum pinch point temperature difference to be reached at two locations in the boiler. Compared to the transcritical organic Rankine cycle, the organic split-cycle improves the boiling process without an entailing increase in the boiler pressure, thus enabling an efficient low grade heat to power conversion at low boiler pressures.
33.	Andreasen, J. G, et al. (författare) Selection and optimization of pure and mixed working fluids for low grade heat utilization using organic Rankine cycles 2014 Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 73 Tidskriftsartikel (refereegranskat)abstract We present a generic methodology for organic Rankine cycle optimization, where the working fluid is included as an optimization parameter, in order to maximize the net power output of the cycle. The method is applied on two optimization cases with hot fluid inlet temperatures at 120°C and 90°C. Pure fluids and mixtures are compared to see how mixed working fluids affect performance and important design parameters. The results indicate that mixed working fluids can increase the net power output of the cycle, while reducing the pressure levels. The maximum net power output is obtained by fluids with a critical temperature close to half of the hot fluid inlet temperature. For some mixtures we find the maximum net power when the temperature glide of condensation matches the temperature increase of the cooling water, while for other mixtures there are large differences between these two parameters. Ethane is a fluid that obtains a large net power increase when used in mixtures. Compared to pure ethane, an optimized ethane/propane mixture attains a 12.9% net power increase when the hot fluid inlet temperature is 120_C and a 11.1% net power increase when the hot fluid inlet temperature is 90°C.
34.	Anglart, Henryk, 1954-, et al. (författare) Mechanistic modelling of dryout and post-dryout heat transfer 2018 Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 161, s. 352-360 Tidskriftsartikel (refereegranskat)abstract In this paper a new mechanistic model for the diabatic annular two-phase flow is presented and applied to prediction of dryout and post-dryout heat transfer in various channels. The model employs a computational fluid dynamics code - OpenFOAM (R) - to solve the governing equations of two-phase mixture flowing in a heated channel. Additional closure laws have been implemented to calculate the location of the dryout and to predict wall temperature in the post-dryout region. Calculated results have been compared with experimental data obtained in pipes and good agreement between predictions and measurements has been achieved. The presented model is applicable to complex geometries and thus can be used for prediction of post-dryout heat transfer in a wide variety of energy conversion systems.
35.	Anjo, J., et al. (författare) Modeling the long-term impact of demand response in energy planning : The Portuguese electric system case study 2018 Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 165, s. 456-468 Tidskriftsartikel (refereegranskat)abstract With the urge to decrease carbon emissions, electricity systems need to evolve to promote the integration of renewable resources and end-use energy efficiency. Demand Response (DR) can be used as a strategy, one among many, to improve the balance between demand and supply of electricity, especially in systems that rely heavily on variable energy renewable resources. Thus, it is important to understand up to what extent a countrywide system would cope with DR implementation. In this work, the impact of demand response in the long-term is assessed, using a model of the Portuguese electricity system in the modeling tool OSeMOSYS. The theoretical potential of DR is computed to understand better the impact on the overall system planning, by analyzing three scenarios – a business as usual scenario, a carbon-free system scenario in 2050, and a scenario without heavy carbon emission restrictions. DR impact in all three scenarios results in a decrease in the overall costs, on the capacity installed and in an increase in the percentage of renewable capacity. Further, an economic analysis showed that DR would take 15 years, on average, to influence the average electricity cost and that the reduction in total costs is mainly due to the avoided capacity investments.
36.	Arghand, Taha, 1982, et al. (författare) Combining direct ground cooling with ground-source heat pumps and district heating: Energy and economic analysis 2023 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 270 Tidskriftsartikel (refereegranskat)abstract Direct ground cooling (DGC) is a method used in cold climates to provide cooling to buildings without the use of any mechanical refrigeration. When DGC is utilized for providing cooling, ground-source heat pumps (GSHPs) and district heating (DH) are the two commonly used technologies for providing heating to the buildings. This article investigates the coupling of DGC with GSHPs and DH in terms of purchased energy and lifecycle costs. An office building equipped with active chilled beams for cooling and radiators for heating is used as a reference. Six cases based on different combinations of building envelope characteristics and thus different building heating and cooling loads are considered. The results show that using DGC-DH significantly reduces the amount of purchased electricity. However, the total energy cost is lower when DGC-GSHP is used. In addition, the DGC-GSHP can be more viable when the ground loads are well balanced. Investment costs, including borehole installation and equipment costs, are lower for the DGC-DH in the majority of the investigated cases. The lifecycle cost is lower for the DGC-DH in most of the investigated cases due to lower equipment costs.
37.	Arnaudo, Monica, et al. (författare) Heat demand peak shaving in urban integrated energy systems by demand side management - A techno-economic and environmental approach 2019 Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 186 Tidskriftsartikel (refereegranskat)abstract The integration of variable renewable resources and decentralized energy technologies generates the need for a larger flexibility of the energy demand. In order to fully deploy a demand side management approach, synergies between interconnected energy systems have to be systematically implemented. By taking this standpoint, this study proposes a new approach to explore the potential of multi-energy integrated energy systems. This approach is constituted by two main steps, which are (1) the performance simulation of selected energy infrastructures and (2) the estimation of related techno-economic performance indicators. Step (1) expands the work presented in previous literature, by including a novel co-simulation feature. In step (2), the levelized cost of energy and location-dependent emission factors are used as key performance indicators. In this paper, the presented approach is demonstrated by implementing two demand side management options for heat peak demand shaving. A Swedish residential neighborhood is considered as a case study. The first option explores the potential of storing heat in the thermal mass of residential buildings. The proposed strategies lead to a decrease of up to 70% of primary energy consumption, depending on the indoor comfort requirements. The second option estimates the techno-economic feasibility of a new set of scenarios based on the integration of geothermal distributed heat pumps within a district heating network. The district heating scenario is found to be the most techno-economical convenient. Nevertheless, a moderate penetration of distributed heat pumps (around 20%) is shown to have a good trade-off with the reduction of CO2 emissions.
38.	Arnaudo, Monica, et al. (författare) Techno-economic analysis of demand side flexibility to enable the integration of distributed heat pumps within a Swedish neighborhood 2020 Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 195 Tidskriftsartikel (refereegranskat)abstract The energy infrastructure in Stockholm faces an imminent problem caused by the saturation of the electricity distribution grid capacity. Given promising economic savings, a few city neighborhoods have decided to switch from district heating to domestic heat pumps. Thus, technical concerns arise. This study aims at proposing demand side management solutions to unlock the integration of distributed heat pumps. A techno-economic analysis is presented to assess the potential of using the buildings’ thermal mass as energy storage. By means of co-simulation, the electricity grid and the buildings are coupled through a feedback control. The grid capacity is monitored to avoid overloadings. The indoor temperature is controlled in order to serve as thermal energy storage. It is found that, given the grid's capacity limits, the infrastructure should still be partly connected to the district heating (around 7% of the heat demand). This dependency decreases of around 1% when the buildings’ thermal mass is used as thermal storage, with a range of ±0.5 °C. On a heat pump level, the disconnections decrease up to 50%, depending on the buildings’ thermal mass capacity. Thus better techno-economic (about −2% on the levelized cost) and environmental (about −1% on the CO2 emissions) performances are unlocked.
39.	Arnaudo, Monica, et al. (författare) Waste heat recovery in low temperature networks versus domesticheat pumps - A techno-economic and environmental analysis 2021 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 219 Tidskriftsartikel (refereegranskat)abstract The planning of energy infrastructures in new districts often follows the practice adopted for the rest of the city. In Stockholm, district heating is a common solution for multi-apartment neighborhoods. Recently, because of an average clean electricity mix, heat pumps have gained interest. However, European studies suggest to limit the reliance on electrification to avoid an extreme demand increase. Thus, an effort is required to improve the environmental impact of alternative options. This study proposes waste heat recovery in low temperature networks as a promising solution. By means of a techno-economic and environmental analysis, this option is compared to domestic heat pumps. A new approach is proposed to combine a district level perspective with simulation tools able to capture sector-coupling interactions. Scenarios, for a real neighborhood, assess waste heat recovery potential and electricity grid loading status. Results show that a waste heat recovery capacity equal to 10% of the peak load can reduce fossil fuel use of 40%. Local grid limitations are shown to be a bottleneck for the feasibility of domestic heat pumps. Their heat generation cost is 28% higher than for district heating. The carbon footprint is strongly dependent on the emission factor of the electricity mix (+11%/-24%).
40.	Astaneh, Majid, 1990, et al. (författare) Multiphysics simulation optimization framework for lithium-ion battery pack design for electric vehicle applications 2022 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 239 Tidskriftsartikel (refereegranskat)abstract Large-scale commercialization of electric vehicles (EVs) seeks to develop battery systems with higher energy efficiency and improved thermal performance. Integrating simulation-based design optimization in battery development process expands the possibilities for novel design exploration. This study presents a dual-stage multiphysics simulation optimization methodology for comprehensive concept design of Lithium-ion (Li-ion) battery packs for EV applications. At the first stage, multi-objective optimization of electrochemical thermally coupled cells is performed using genetic algorithm considering the specific energy and the maximum temperature of the cells as design objectives. At the second stage, the energy efficiency and the thermal performances of each optimally designed cell are evaluated under pack operation to account for cell-to-pack interactions under realistic working scenarios. When operating at 1.5 C discharge current, the battery pack comprising optimally designed cells for which the specific energy and the maximum temperature are equally weighted delivers the highest specific energy with enhanced thermal performance. The most favorable pack design shows 8% reduction in maximum pack temperature and 16.1% reduction in module-to-module temperature variations compared to commercially available pack. The methodology for design optimization presented in this work is generic, providing valuable knowledge for future cell and pack designs that employ different chemistries and configurations.
41.	Averfalk, Helge, 1988-, et al. (författare) Economic benefits of fourth generation district heating 2020 Ingår i: Energy. - London, UK : Elsevier. - 0360-5442 .- 1873-6785. ; 193 Tidskriftsartikel (refereegranskat)abstract The main impetus for lower distribution temperatures in district heating systems is the lower heat supply costs obtained by these lower temperatures. In this paper, the differences in heat supply costs for two different temperature levels have been estimated for various future heat supply options. The estimations were obtained by modelling a district heating system characterised by typical climate conditions for Central Europe. High sensitivity to lower supply costs from lower temperatures was found for geothermal heat, industrial excess heat, and heat pumps, whereas low cost sensitivity was estimated for combined heat and power plants using waste or biomass. Lower heat distribution loss constitutes a minor component of the total cost reductions. The current use of high heat distribution temperatures was identified as an important barrier for the transition to renewable and recycled heat supply in district heating systems. Hence, lower distribution temperatures would facilitate this required transition because lower distribution temperatures provide higher profitability for these renewable and recycled heat sources. © 2019 The Authors. Published by Elsevier Ltd.
42.	Averfalk, Helge, 1988-, et al. (författare) Novel low temperature heat distribution technology 2018 Ingår i: Energy. - London : Elsevier. - 0360-5442 .- 1873-6785. ; 145, s. 526-539 Tidskriftsartikel (refereegranskat)abstract Lower future heat demands and lower availability of non-fossil high temperature heat supply are expected future market conditions that restrain the long-term viability of contemporary district heating systems. Hence, current district heating technology should be enhanced to increase system performance in new heat distribution areas. This paper aims to outline a proposal for technical improvements required to achieve lower annual average return temperatures in new residential buildings to improve viability in future market conditions. The proposed technical solution consists of three principle changes: three-pipe distribution networks, apartment substations, and longer thermal lengths for heat exchangers. The three technical modifications aims at addressing system embedded temperature errors. Furthermore, a simulation model was developed to assess the proposed technical solution concerning different energy performances of buildings and different thermal lengths in heat exchangers. The results show that implementation of the three technical modifications reaches time-weighted annual average return temperatures of 17–21 °C with supply temperatures of about 50 °C. The results also verify the increased necessity to separate the network return flows into delivery and recirculation flows in residential substations as energy performance in buildings increase.
43.	Axelsson, Erik Marcus Kristian, 1974, et al. (författare) A tool for creating energy market scenarios for evaluation of investments in energy intensive industry 2009 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 34:12, s. 2069-2074 Tidskriftsartikel (refereegranskat)abstract The energy intensive industry can be a major contributor to CO2 emissions reduction, provided that appropriate investments are made. To assess profitability and net CO2 emissions reduction potential of such investments, predictions about future energy market conditions are needed. Energy market scenarios can be used to reflect different possible future energy market conditions. This paper presents a tool for creating consistent energy market scenarios adapted for evaluation of energy related investments in energy intensive industrial processes. Required user inputs include fossil fuel prices and costsassociated with policy instruments, and the outputs are energy market prices and CO2 consequences of import/export of different energy streams (e.g. electric power and biomass fuel) from an industrial process site. The paper also presents four energy market scenarios for the medium-term future (i.e. around 2020) created using the tool.
44.	Ayele, Getnet Tadesse, et al. (författare) Optimal placement and sizing of heat pumps and heat only boilers in a coupled electricity and heating networks 2019 Ingår i: Energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-5442 .- 1873-6785. ; 182, s. 122-134 Tidskriftsartikel (refereegranskat)abstract Multi-energy systems are reported to have a better environmental and economic performance relative to the conventional, single-carrier, energy systems. Electrification of district heating networks using heat pumps and combined heat and power technologies is one such example. Due to lack of suitable modelling tools, however, the sizing and optimal placement of heat pumps is always done only from the heating network point of view which sometimes compromises the electricity network. This paper proposes an integrated optimization algorithm to overcome such limitation. A load flow model based on an extended energy hub approach is combined with a nested particle swarm optimization algorithm. A waste to energy combined heat and power plant, heat pumps (HPs), heat only boiler (HOB), solar photovoltaic, wind turbines and imports from the neighborhood grids are considered in the case studies. The results show that optimal placement and sizing of HPs and a HOB using the proposed methodology avoids an unacceptable voltage profiles and overloading of the electricity distribution network, which could arise while optimizing only from the heating network point of view. It also shows that up to 41.2% of the electric loss and 5% of the overall operating cost could be saved.
45.	Badenes, Borja, et al. (författare) Development of advanced materials guided by numerical simulations to improve performance and cost-efficiency of borehole heat exchangers (BHEs) 2020 Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 201 Tidskriftsartikel (refereegranskat)abstract One promising way to improve the efficiency of borehole heat exchangers (BHEs) in shallow geothermal applications is to enhance the thermal properties of the materials involved in its construction. Early attempts, such as using metal tubes in the 1980s or the utilization of thin–foil hoses, did not succeed in being adopted by the market for diverse reasons (cost, corrosion, fragility, etc…). In parallel, the optimization of pipe size, the use of double-U-tubes, thermally enhanced grout, etc. were able to bring the measure for the BHE efficiency, the borehole thermal resistance, from 0.20 to 0.15 K/(Wm) down to 0.08–0.06 K/(Wm) in the best solutions today. A further improvement cannot be expected without development of new, dedicated materials, combining the versatility of plastic like PE with an increased thermal conductivity that matches the respective properties of the rock and soil. This goal was included in the Strategic Research and Innovation Agenda of the European Technology Platform on Renewable Heating and Cooling in 2013. Within an EU supported project, both BHE pipes and grouting materials have been produced prototypically in small amounts, suitable for the first tests in the intended environment. The present work explains the research pathways envisaged and the resulting sensitivity analysis to highlight the influence of some of the most critical parameters that affect the overall performance of a GSHP system. The results have allowed guiding the real development of more efficient new advanced materials for different scenarios representative of different European regions. Finally the developed materials and their properties are discussed, including a comparative assessment about their compliance with reference material properties as currently seen in the BHE market. © 2020 The Author(s)
46.	Bagge, Hans, et al. (författare) Measurements of household electricity and domestic hot water use in dwellings and the effect of different monitoring time resolution 2011 Ingår i: Energy. - : Elsevier BV. - 1873-6785 .- 0360-5442. ; 36:5, s. 2943-2951 Tidskriftsartikel (refereegranskat)abstract The use of household electricity and domestic hot water has been measured for 72 apartments in an apartment building located in the south of Sweden. The measurements were carried out with samples every 6 s, a tenfold increase in resolution compared to available published data, during a measurement period of five days, in the winter season, including a weekend. The influence of the time resolution on the distribution of data was analysed by integrating the 6 s data to represent longer logging intervals. Extreme values, especially the high values, are shown to be reduced if the time interval is increased. The maximum household electric power was 50% higher at a 6 s resolution compared to 60 s and the corresponding difference for domestic hot water flow was 40%. Daily variations has to be considered for photovoltaic installations and solar thermal collectors, energy simulations of buildings need at least hourly data and all kind of power design in a building or its services benefits from much more resolved data. (C) 2011 Elsevier Ltd. All rights reserved.
47.	Bahaj, AbuBakr S., et al. (författare) Shaping array design of marine current energy converters through scaled experimental analysis 2013 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 59:0, s. 83-94 Tidskriftsartikel (refereegranskat)abstract Marine current energy converters or tidal turbines represent an emerging renewable energy technology that can provide a predictable supply of electricity. Single devices are in operation around the world with aspirations to deploy farms or arrays of multiple devices. We present an experimental study that has characterised the downstream wake flow around a 1/15th-scale turbine in a large circulating water channel and a series of experiments involving static actuator disks at 1/120th-scale allowing simulation of multiple-device layouts. Our analysis demonstrates that the near wake is highly turbulent with structures generated by the rotor and support structure. This region of flow may prove difficult to numerically simulate with a high degree of accuracy. In the far wake the performance of static actuator disks can be matched to mechanical rotors reducing scale and cost facilitating replication of complex array geometries. Here the ambient turbulence and geometric properties of the device/channel drive the wake recovery towards free stream conditions. Devices operating downstream of others will be subject to a non-steady flow field making comparative performance difficult. We discuss the possibility of unequal device specification and rated power within an array (unlike wind farms) providing a more representative measure of array performance.
48.	Baigmohammadi, Mohammadreza, et al. (författare) Experimental study on the effects of mixture flow rate, equivalence ratio, oxygen enhancement, and geometrical parameters on propane air premixed flame dynamics in non-adiabatic meso-scale reactors 2017 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 121, s. 657-675 Tidskriftsartikel (refereegranskat)abstract In the present study, the effects of reactive mixture flow rate, adding oxygen to propane-air mixture, geometrical parameters, and equivalence ratio on propane-air/oxygen premixed flame dynamics in non adiabatic meso-scale reactors were experimentally investigated. During the experiments, seven flame regimes of blow-off, blow-out, asymmetric stationary, stationary-repetitive extinction and re-ignition (RERI), forced/self-RERI, RERI-flash-back, and flash-back were observed. The results showed that increasing the reactive mixture flow rate could generally promote variety of the flame regimes and also improve flame stability in the non-adiabatic meso-scale reactors, especially in 40% and 80% oxygen enhanced cases. Also, the results demonstrated that increasing the reactor inner diameter and equivalence ratio generally extended propane-air- oxygen flame stability and its presence range in the non adiabatic meso-scale reactors. Moreover, it was shown that increasing the reactor length and also increasing the added oxygen to propane-air mixture more than 40% promoted flame instability and consequently restricted propane-air-oxygen flame presence range in the non-adiabatic meso-scale reactors. Also, it was shown that variations in the mixture flow rate, the reactor length and inner diameter, equivalence ratio, and oxygen concentration in propane-air mixture could significantly influence the flame average propagation speed, acoustic, and chemiluminescence in the non-adiabatic meso-scale reactors.
49.	Balderrama, Sergio, et al. (författare) Surrogate models for rural energy planning : Application to Bolivian lowlands isolated communities 2021 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 232 Tidskriftsartikel (refereegranskat)abstract Thanks to their modularity and their capacity to adapt to different contexts, hybrid microgrids are a promising solution to decrease greenhouse gas emissions worldwide. To properly assess their impact in different settings at country or cross-country level, microgrids must be designed for each particular situation, which leads to computationally intractable problems. To tackle this issue, a methodology is proposed to create surrogate models using machine learning techniques and a database of microgrids. The selected regression model is based on Gaussian Processes and allows to drastically decrease the computation time relative to the optimal deployment of the technology. The results indicate that the proposed methodology can accurately predict key optimization variables for the design of the microgrid system. The regression models are especially well suited to estimate the net present cost and the levelized cost of electricity (R-2 = 0.99 and 0.98). Their accuracy is lower when predicting internal system variables such as installed capacities of PV and batteries (R-2 = 0.92 and 0.86). A least-cost path towards 100% electrification coverage for the Bolivian lowlands mid-size communities is finally computed, demonstrating the usability and computational efficiency of the proposed framework.
50.	Baldi, Francesco, 1986, et al. (författare) A feasibility analysis of waste heat recovery systems for marine applications 2015 Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 80, s. 654-665 Tidskriftsartikel (refereegranskat)abstract The shipping sector is today facing challenges which require a larger focus on energy efficiency and fuel consumption. In this article, a methodology for performing a feasibility analysis of the installation of a WHR (waste heat recovery) system on a vessel is described and applied to a case study vessel. The method proposes to calculate the amount of energy and exergy available for the WHR systems and to compare it with the propulsion and auxiliary power needs based on available data for ship operational profile. The expected exergy efficiency of the WHR system is used as an independent variable, thus allowing estimating the expected fuel savings when a detailed design of the WHR system is not yet available. The use of the proposed method can guide in the choice of the installation depending on the requirements of the owner in terms of payback time and capital investment. The results of the application of this method to the case study ship suggest that fuel savings of 5%–15% can realistically be expected, depending on the sources of waste heat used and on the expected efficiency of the WHR system.

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