| 1. |
- Magnusson, Mimmi, 1980-, et al.
(author)
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Biogas from mechanical pulping industry : Potential improvement for increased biomass vehicle fuels
- 2012
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In: Proceedings of the 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes, ECOS 2012. - 9788866553229 ; , s. 56-67
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Conference paper (peer-reviewed)abstract
- Biogas is a vehicle fuel of the first generation of biofuels with great potential for reducing the climate impact from the transport sector. Today biogas is mainly produced by digestion in Sweden and the total amounts to 1.4 TWhLHV/year (2010) of which about 0.6 TWhLHV is upgraded and used in the transport sector. Using industrial wastewater, e.g. from a pulp and paper mill, as substrate for production of biogas, the amount of renewable fuel to the transport sector could be increased. In the pulping industry, substantial amounts of organic matter are generated; this is commonly treated aerobically to reduce the chemical oxygen demand (COD) in the effluent streams before discharge to a recipient. Treating these effluent streams mainly anaerobically instead could contribute to the transport sector's energy supply. The aim of this study is to investigate the potential for using effluent streams from the Swedish mechanical pulp and paper industry to produce biogas. A typical Swedish mechanical pulp mill is considered for anaerobic treatment of the wastewaters. This type of pulp mill presently uses conventional methods for wastewater treatment to reduce COD, but converting most of this to anaerobic treatment would increase the amount of biogas produced. When considering this conversion in a larger context, supposing that anaerobic treatment would be applied to all Swedish mechanical pulp mills, which stand for about 30% of the total Swedish pulp production, it is shown that the production could amount to as much as 0.5 TWhLHV/year of biogas. This represents about one third of the biogas produced in Sweden today. The main conclusion of this study is that if anaerobic treatment of effluent streams from the pulping industry were introduced, the biogas production in Sweden could be significantly increased, thus moving one step further in reducing the transport sector's climate impact.
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| 2. |
- Persson, Johannes, et al.
(author)
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Simultaneous production of domestic hot water and space cooling with a heat pump in a Swedish Passive House
- 2012
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In: Proceedings of the 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes, ECOS 2012. - 9788866553229 ; , s. 251-260
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Conference paper (peer-reviewed)abstract
- Passive Houses have gained popularity the last ten years as a way of improving the energy efficiency in the housing stock. During the cold winter in Sweden, space heating is at times needed but a Passive House is limited to a maximum use of energy for space heating. The challenge of avoiding space heating during the cold wint er climate in Sweden has pushed the design of a Passive House in a direction where problems with excessive indoor temperatures might occur summertime. This paper evaluates a comfort cooling strategy for reaching comfortable indoor climate summertime while maintaining good energy efficiency. The strategy is to use the free cooling from a heat pump while producing domestic hot water. A literature study on heat pumps for simultaneous heating and cooling (HPS) was made in order to make assumptions of the cooling and heating capacities of the HPS for the building simulations. The effect this free cooling has on the indoor climate was thereafter simulated with IDA Indoor Climate and Energy. The building model is based on an actual Passive House in the district of Lambohov in Linköping, Sweden, where continuous logging of temperatures are available. Without comfort cooling, the simulations show excessive temperatures summertime, which is consistent with field measurements from the actual house. Further, the simulation results demonstrate a substantial removal (60-80 %) of excessive indoor temperatures summertime with the cooling strategy implemented.
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| 3. |
- Romão, Inês, et al.
(author)
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Carbon dioxide storage by mineralisation applied to a lime kiln
- 2012
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In: PROCEEDINGS OF ECOS 2012. - Firenze : Firenze University Press. - 9788866553229 ; , s. 226-1-226-13
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Conference paper (peer-reviewed)abstract
- This paper describes a design, for a pilot-scale application, of a two-staged process that is under study at Åbo Akademi University (ÅA), for Carbon dioxide Storage by Mineralisation (CSM). The ÅA route implies the production of brucite (besides Ca- and Fe- based by-products) from a magnesium/calcium silicate rock, using recoverable ammonium sulphate (AS), followed by carbonation of the Mg(OH)2 in a pressurised fluidised bed at ~ 500°C, 20-30 bar CO2 partial pressure. An assessment is reported for operating the CSM process on waste heat from a limekiln (lime production: 210 t/day) in Pargas, Southwest Finland, i.e. without external energy input apart from what is needed for crushing the rock to the required particle size (a few % of the overall CSM process energy requirement) and compressing the flue gas to be treated. Part of the off-gas from the limekiln (CO2 content ~21%-vol) will be processed without a CO2 separation step. The feature of operating without CO2 separation makes CSM an attractive and cost-competitive option when compared to conventional CCS involving underground storage of CO2. An exergy analysis is used to optimise process layout and energy efficiency, and at the same time maximise the amount of CO2 that can be bound to MgCO3 given the amount of waste heat available from the kiln. Also, experimental results are reported for producing Mg(OH)2 (and Fe,Ca(OH)2) from local rock material.
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| 4. |
- Toffolo, Andrea, et al.
(author)
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An organic rankine cycle off-design model for the search of the optimal control strategy
- 2012
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In: ECOS 2012. - Firenze : Firenze University Press. - 9788866553229 ; , s. 28-41
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Conference paper (peer-reviewed)abstract
- Power generation from low enthalpy geothermal resources using Organic Rankine Cycle systems is markedly influenced by the temperature level of the heat source and heat sink. During plant operation the actual temperature of the geofluid may be different from the value assumed in the design phase. In addition, the seasonal and daily variations of the ambient temperature greatly affect the power output especially when a dry condensation system is used. This paper presents a detailed off-design model of an Organic Rankine Cycle that includes the performance curves of the main plant components. Two capacitive components in the model have the key function of damping the temporary disequilibrium of mass and energy inside the system. Isobutane and R134a are considered as working fluids, mainly operating in subcritical and supercritical cycles, respectively. The off-design model is used to find the optimal operating parameters that maximize the electricity production in response to changes of the ambient temperatures between 0 and 30°C and geofluid temperatures between 130 and 180°C. This optimal operation strategy can be conveniently applied both to already existing plants and in the choice of new design plant configurations. --------------------------------------------------------------------------------
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| 5. |
- Wikström, Martina, et al.
(author)
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Biogas or electricity as vehicle fuels derived from food waste-the case of stockholm
- 2012
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In: Proceedings of the 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes, ECOS 2012. - : Åbo Akademi University Press. - 9788866553229 ; , s. 68-77
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Conference paper (peer-reviewed)abstract
- The demand for renewable energy is increasing in Stockholm as well as the rest of the world. Imperative factors, such as the need to reduce anthropogenic green house gas emissions and security of supply, force this development. The European Commission distinguishes the organic compound in municipal solid waste as food waste. Food waste may be digested, form biogas and after upgrading, the biogas may be used as fuel in automotive applications. This study is based on the food waste potential estimations performed by the Stockholm County Administration Board in the County of Stockholm, both in 2009 and in 2030. The County Administration Board aim for this food waste to be converted to the vehicle fuel biogas since this would improve the share of renewable transport fuels and, simultaneously, decrease the green house gas emissions coupled with the degradation of organic material. In 2009, Stockholm generated 122 000 tonnes of food waste which could have been converted to 130 GWh biogas. This amount of biogas corresponds to approximately 15 million litres of petrol. In 2030, the County Administration Board estimates the food waste has increased to 152 000 tonnes, which converted would correspond to 170 GWh biogas. This study will expand the analysis and will consider the option where the biogas from the food waste is use to generate electricity to fuel electric vehicles in Stockholm. In 2009, no large-scale introduction of electric vehicles in Stockholm had begun but it is vital for decision-makers to assess this option for 2030 in order to obtain a resource and energy efficient Stockholm.When considering electricity as vehicle fuel, converting the energy carrier will include additional steps such as electricity generation, distribution, charging of the vehicle as well as the electric powertrain. The overall energy efficiency, from biogas to electric propulsion, is in the order of 40 %. Even though when adding process steps, which imply losses, the more energy efficient energy carrier is electricity. Converting the biogas from the food waste to electricity adds approximately another 10 % of driving distance. Assuming an annual driving distance of 15 000 kilometres, in 2030 this would imply either 27 450 biogas or 30 200 electric passenger cars in the county of Stockholm. The most resource and energy efficient usage of the biogas from food waste would be to convert it to electricity for electric vehicles.
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