| 1. |
- Difs, Kristina, et al.
(författare)
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Biomass gasification opportunities in a district heating system
- 2010
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Ingår i: Biomass and Bioenergy. - : Elsevier Science B.V., Amsterdam.. - 0961-9534 .- 1873-2909. ; 34:5, s. 637-651
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates the economic effects and the potential for reduced CO2 emissions when biomass gasification applications are introduced in a Swedish district heating (DH) system. The gasification applications included in the study deliver heat to the DH network while producing renewable electricity or biofuels. Gasification applications included are: external superheater for steam from waste incineration (waste boost, WE), gas engine CHP (BIGGE), combined cycle CHP (BIGCC) and production of synthetic natural gas (SNG) for use as transportation fuel. Six scenarios are used, employing two time perspectives - short-term and medium-term - and differing in economic input data, investment options and technical system. To evaluate the economic performance an optimisation model is used to identify the most profitable alternatives regarding investments and plant operation while meeting the DH demand. This study shows that introducing biomass gasification in the DH system will lead to economic benefits for the DH supplier as well as reduce global CO2 emissions. Biomass gasification significantly increases the potential for production of high value products (electricity or SNG) in the DH system. However, which form of investment that is most profitable is shown to be highly dependent on the level of policy instruments for biofuels and renewable electricity. Biomass gasification applications can thus be interesting for DH suppliers in the future, and may be a vital measure to reach the 2020 targets for greenhouse gases and renewable energy, given continued technology development and long-term policy instruments.
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| 2. |
- Difs, Kristina
(författare)
-
District Heating and CHP : Local Possibilities for Global Climate Change Mitigation
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Global warming, in combination with increasing energy demand and higher energy prices, makes it necessary to change the energy use. To secure the energy supply and to develop sustainable societies, construction of energy-efficient systems is at the same time most vital. The aim of this thesis is therefore to identify how a local energy company, producing district heating (DH), district cooling (DC) and electricity in combined heat and power (CHP) plants, can contribute to resource-efficient energy systems and cost-effective reductions of global carbon dioxide (CO2) emissions, along with its customers. Analyses have been performed on how a local energy company can optimise their DH and DC production and what supply-side and demand-side measures can lead to energy-efficient systems in combination with economic and climate change benefits. The energy company in focus is located in Linköping, Sweden. Optimisation models, such as MODEST and reMIND, have been used for analysing the energy systems. Scenario and sensitivity analyses have also been performed for evaluation of the robustness of the energy systems studied. For all analyses a European energy system perspective was applied, where a fully deregulated European electricity market with no bottlenecks or other system failures was assumed.In this thesis it is concluded that of the DH-supply technologies studied, the biomass gasification applications and the natural gas combined cycle (NGCC) CHP are the technologies with the largest global CO2 reduction potential, while the biomass-fuelled plant that only produces heat is the investment with the smallest global CO2 reduction and savings potential. However, the global CO2 reduction potential for the biomass integrated gasification combined cycle (BIGCC) CHP and NGCC CHP, the two technologies with highest electricity efficiencies, is highly dependent on the assumptions made about marginal European electricity production. Regarding the effect on the DH system cost the gasification application integrated with production of renewable biofuels (SNG) for the transport sector is the investment option with the largest savings potential for lower electricity prices, while with increasing electricity prices the BIGCC and NGCC CHP plants are the most cost-effective investment options. The economic outcome for biomass gasification applications is, however, dependent on the level of policy instruments for biofuels and renewable electricity. Moreover, it was shown that the tradable green certificates for renewable electricity can, when applied to DH systems, contribute to investments that will not fully utilise the DH systems’ potential for global CO2 emissions reductions.Also illustrated is that conversion of industrial processes, utilising electricity and fossil fuels, to DH and DC can contribute to energy savings. Since DH is mainly used for space heating, the heat demand for DH systems is strongly outdoor temperature-dependent. By converting industrial processes, where the heat demand is often dependent on process hours instead of outdoor temperature, the heat loads in DH systems can become more evenly distributed over the year, with increased base-load heat demand and increased electricity generation in CHP plants as an outcome. This extra electricity production, in combination with the freed electricity when converting electricity-using processes to DH, can replace marginal electricity production in the European electricity market, resulting in reduced global CO2 emissions.Demonstrated in this thesis is that the local energy company, along with its customers, can contribute to reaching the European Union’s targets of reducing energy use and decreasing CO2 emissions. This can be achieved in a manner that is cost-effective to both the local energy company and the customers.
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| 3. |
- Difs, Kristina, et al.
(författare)
-
Energy conservation measures in buildings heated by district heating - A local energy system perspective
- 2010
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Ingår i: Energy. - : Elsevier Science B.V., Amsterdam.. - 0360-5442 .- 1873-6785. ; 35:8, s. 3194-3203
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Tidskriftsartikel (refereegranskat)abstract
- The extensive energy use in the European building sector creates opportunities for implementing energy conservation measures (ECMs) in residential buildings. If ECM are implemented in buildings that are connected to a district heating (DH) system, the operation of DH plants may be affected, which in turn may change both revenue and electricity production in cogeneration plants. In this study a local energy system, containing a DH supplier and its customer, has been analysed when implementing three ECMs: heat load control, attic insulation and electricity savings. This study is unique since it analyses economic and CO2 impacts of the ECMs in both a user and a supplier perspective in combination with a deregulated European electricity market. Results show that for the local energy system electricity savings should be prioritised over a reduction in DH use, both from an economic and a global CO2 perspective. For the DH supplier attic insulation demonstrates unprofitable results, even though this measure affects the expensive peak load boilers most. Heat load control is however financially beneficial for both the DH supplier and the residences. Furthermore, the relation between the fixed and variable DH costs is highlighted as a key factor for the profitability of the ECMs.
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| 4. |
- Difs, Kristina
(författare)
-
National energy policies: obstructing the reduction of global CO2 emissions? An analysis of Swedish energy policies for the district heating sector
- 2010
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Ingår i: Energy Policy. - : Elsevier BV. - 0301-4215 .- 1873-6777. ; 38:12, s. 7775-7782
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Tidskriftsartikel (refereegranskat)abstract
- The effect of national energy policies on a local Swedish district heating (DH) system has been studied regarding the profitability of new investments and the potential for climate change mitigation. The DH system has been optimised regarding three investments: biomass-fuelled CHP (bio CHP), natural gas-fuelled combined cycle CHP (NGCC CHP) and biomass-fuelled heat-only boiler (bio HOB) in two scenarios (with or without national taxes and policy instruments). In both scenarios EU’s tradable CO2 emission permits are included. Results from the study show that when national policies are included, the most cost-effective investment option is the bio CHP technology. However, when national taxes and policy instruments are excluded, the DH system containing the NGCC CHP plant has 30% lower system cost than the bio CHP system. Regardless of the scenario and when coal condensing is considered as marginal electricity production, the NGCC CHP has the largest global CO2 reduction potential, about 300 ktonne CO2. However, the CO2 reduction potential is highly dependent on the marginal electricity production. Demonstrated here is that national policies such as tradable green certificates can, when applied to DH systems, contribute to investments that will not fully utilise the DH systems’ potential for global CO2 emissions reductions.
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