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Heat Roadmap Europe by mapping the location of the resource, and comparing it to the location of the heat demand that is suitable for district heating (see Figure 3). The results suggest that there is enough renewable heat to supply approximately 90% of the heat demand that is suitable for district heating in Europe (which is 50% of the EU’s total heat demand). Some of these district heating systems will be able to supply all of their heat with renewables and some will be able to provide very little, depending on the local conditions. Overall, if the urban areas in Europe are converted to district heating, then there will be enough renewable heat to supply almost all of their heat demand, primarily in the form of deep geothermal. Again, none of these renewable heat sources can be accessed if a district heating network is not in place, which is a waste of sustainable energy resources.
Figure 1: Primary energy supply (total fuel in e.g. coal, oil, etc.), final energy consumption (total fuels produced e.g. electricity, heat, etc.), and end-use demand (e.g. space heat, hot water, etc.) in the European energy system in 2010 [2]. District heating provides the connection between energy demand in buildings and homes, and this inefficiency in the electricity, industry and waste sectors. Without a district heating system in place, none of these excess heat sources can be used to heat the buildings nearby and alternative, additional, heat supplies must be used. For example, an extract from the Pan- European Thermal Atlas (Peta), which is available on the Heat Roadmap Europe website (www.heatroadmap.eu), demonstrates the scale of this potential for Belfast in Northern Ireland. As displayed in Figure 2, the heat demand suitable for district heating (blue area with blue-boxed feature data) is over 16 PJ/ year. This is located next to a power station (black triangle) that could supply up to 12.68 PJ/year of excess heat. If a district heating system is installed, then up to 75% of the heat demand in Belfast could be supplied using excess heat from this single power plant. Without the district heating network in place, all of this energy is wasted in the sea nearby, and gas has to be imported to heat the buildings.
Figure 3: Mapping of various renewable heat resources in Heat Roadmap Europe [6], [7].
Integrating renewable electricity with district heating The final source of sustainable energy that is accessible using district heating, and which also relies on the integration of the system, is renewable electricity such as wind and solar power. Heat pumps, especially large scale, play a crucial role in this. The key to this is the cost of energy storage: thermal storage on a district heating network is approximately 100 times cheaper than electricity storage (see Figure 4). By connecting the heating sector with the electricity sector, renewables can be introduced into the heating sector and thermal storage options can be used to store (electric) renewable energy. Consequences of this are evident from the scale of energy storage that is installed in Denmark compared to other countries without district heating. Denmark has approximately 65 GWh of thermal storage on its district heating network, whereas Britain has approximately 27 GWh of electricity storage installed on its electricity grid. This means that Denmark has almost double the energy storage capacity of Britain and Denmark is already utilising this thermal storage to integrate renewable electricity, primarily wind power.
Figure 2: Image of Belfast from the Pan-European Thermal Atlas [5]: www. heatroadmap.eu. It displays the heat demand in the city by heat density and it is possible to select the area in the city that is suitable for district heating (it is selected in this image and therefore highlighted in blue). Upon selecting the potential district heating area, a variety of statistics are displayed on the left panel: for example, the heat demand in this selected area is 16,370 TJ/ year. It is also possible to select potential heat sources to identify the maximum potential for excess or renewable heat nearby. In this case, a power plant to the North of the city is selected, indicating that there is 12.68 PJ/year of potential excess heat available. Integrating renewable heat with district heating Similarly, there are also various forms of renewable heat that can only be utilised if a district heating network is in place. These include large-scale solar thermal, shallow geothermal, and deep geothermal. Each of these resources is analysed in
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