Implementation, diversification and coupling of different renewable energy sources and renewable energy systems in local and district heating networks

Abstract

In local heating networks and district heating networks, where heat is supplied to heatconsumers, it is known that different energy sources can be used to generate heat. Inaddition to fossil fuels (such as coal, oil, gas), also renewable energy sources (such asbiomass, solar energy, geothermal energy, electricity, etc.) can be used. Climateprotection targets of countries and associations of countries such as the European Unionwill regulate among other things the generation of heat in local and district heatingnetworks in the future. The goal of the European Union is the defossilisation anddecarbonisation of all energy sectors by 2050. Some countries, such as Austria, havecommitted to achieve climate neutrality already in 2040, which means that onlyrenewable energy sources can be used for energy generation from then on. For local anddistrict heating networks, this will result in challenges that have to be solved on severallevels.On the one hand, there will be a strong conversion boom in the space heating sector toreplace existing heating systems that are based on fossil fuels by renewable heatingsystems. In future, existing heating systems based on coal, oil and gas will be replaced byheat pump heating systems, biomass heating systems or local and district heating systems.In places where a local or a district heating network already exists, additional householdswill be connected to the local or the district heating system. The strong expansion of theexisting local and district heating network infrastructure and the construction of new localand district heating network infrastructures will increase the demand for heat to operatethese local and district heating networks. In addition to an increasing demand for heat,the heat generation in local and district heating networks must also be transformed torenewable energy sources. Nowadays, renewable local and district heat is generated frombiomass (e.g. wood), solar energy, geothermal energy, heat pumps, renewable waste,residual heat, or electricity.In most local and district heating networks, wood is used to provide renewable heat,because the utilization of the other mentioned renewable energy sources is technicallyand / or economically difficult or even impossible.But also, wood as a renewable energy source is limited if the forest is cultivated in asustainable way so that it can be assumed that the generation of renewable local anddistrict heat cannot only be based on wood as a biomass source in the future. Instead, itcan be expected that renewable local and district heat generation will be based on varioussources in the future.In the course of this master's thesis, various technologies will be presented that can beused to generate renewable local and district heat in existing and growing local anddistrict heating networks as well as in local and district heating networks that will beerected in the future. A major focus in the master's thesis will be put on the coupling ofall energy sectors. The sector coupling will be an essential factor in the energy system ofthe future to ensure a reliable and efficient utilization of all renewable energy sourcesdespite their volatility. In addition to the presentation of the generation technologies,measures to increase the efficiency will be presented. The applicability of the generationtechnologies and the efficiency improvement measures will be analyzed anddemonstrated based on a technological analysis as well as on a technical and an economiccalculation.Finally, the master's thesis should enable the derivation of an optimal system constellation(best practice) for local and district heating networks which need to be expanded as wellas for new local and district heating networks taking into account technical and ecologicalframework conditions. The conclusion will reflect the experience and knowledge that hasbeen gained as well as problems that must be solved in future. A future perspective willprovide a rough forecast on the local and district heating networks of the future.