Ökad resurseffektivitet i kraftvärmesystem genom säsongslagring av värme
BorrhålslagerSäsongsvärmelagerKraftvärmeproduktionResurseffektivitetKompressionsvärmepumparAbsorptionsvärmepumparMATLABModellering
Increased resource efficiency in an energy system could result in large economic and environmental benefits. Tekniska verken i Linköping AB (Tekniska verken) is responsible for the district heating network in Linköping. Their vision is to create the world?s most resource efficient region. An important step towards this vision is more efficient usage of produced heat, something which could be achieved through integration of a seasonal heat storage in the energy system. The purpose of the Master?s thesis is therefore to explore the economic and technical potential for a seasonal heat storage in Tekniska verken?s energy system. The investigated technology is borehole thermal energy storage using two different kinds of borehole heat exchangers; u-pipe and annular coaxial heat exchanger.To evaluate how Tekniska verken?s energy system changes through integration of a seasonal heat storage a calculation model has been developed in MATLAB. The heat from the seasonal storage needs to be upgraded in order to be used in the ordinary district heating network. Therefore two kinds of heat pumps have been evaluated in the model; absorption heat pumps and compression heat pumps. The main method used for calculations on the heat transfer processes in the storage is the finite difference method. During economic calculations, the economic potential of the investment is expressed solely in relation to the scenario that the storage is not built.Four different combinations of borehole heat exchangers and heat pumps have been simulated over a twenty year period. The simulated storages have a depth of 200-250 meters and a radius of approximately 100 meters which relates to1500 boreholes. The result shows small differences between the two types of heat exchangers. The choice of heat pump has though a crucial importance of the economic result. The systems with absorption heat pumps uses drive heat from existing steam production and can cover a major part of the peak load during winter. Meanwhile the compression heat pumps have a large cost for electricity. This causes a negative net present value according to the result, while the systems with absorption heat pumps have a discounted pay-back time of 12 years. Another positive effect of the systems with absorption heat pumps is the decrease in carbon dioxide emissions from the heat production.The result of the Master thesis shows that both economic advantages and increased resource efficiency can be achieved through integration of a borehole thermal energy storage with absorptions heat pumps. To further investigate this potential seems therefore beneficial.