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CONCEPT OF THE HEAT-DISPATCH-CENTRE In Figure 1 the, (in the following stepwise explained), connection of two consumers, three storages and four heat generation units is visualized. The relevant components of the Heat-Dispatch-Centre are the generation and storage units as well as their control.
Derived from the fluctuating nature of solar thermal heat generation units (middle bottom), their smart integration depends on solar irradiation and the resulting outlet temperature as well as load. At times of high solar irradiation, the return from the high-efficiency consumer is directed to the solar system and reaches the low-efficiency consumers flow
temperature. At times of medium irradiation, the solar thermal plant provides a share of the overall temperature lift. Lastly, at times of low irradiation, the solar thermal low-temperature heat is added to the low-temperature storage and serves as energy source for the heat pump, allowing a more efficient operation of the heat pump.
TECHNOECONOMIC RESULTS FOR THE CASE STUDY
With a calculation tool, the reachable share of heat supply by heat generation unit for an exemplary customer is calculated. Here the provision of heat from heat pump and wood gasification with CHP is prioritized over heat supply from the primary heating network. In this case study, due to limitations in space for
Figure 1: Interconnection of different renewable heat sources in the Heat-Dispatch-Centre
seasonal storage tanks, the usage of solar thermal energy is neglected, also no low-temperature storage tank is included. For the case study scenario, funding of 20 % on all investments is available. The composition of final energies for heat supply for the case study is represented in Figure 2. In the set configuration and operation logic, the main heat source is the wood gasification with CHP. Here the heat provided by the heat pump is the sum of the two energy sources “Electricity from CHP” and “Environmental energy for heat pump”.
On the right side, the heat customers are illustrated. The one at the bottom is a high-efficiency building, requiring a low supply temperature, and the other at the top a low-efficiency building with a high flow temperature. In order to increase the difference between the overall flow and return temperature, these customers are connected in series. The required flow temperature can easily be provided by the two high-temperature heat generation units, namely primary heat network and biomass gasification with CHP (top left). Below these, the low-temperature generation unit, namely the wastewater heat pump, is depicted. It increases the temperature of the return of the high-efficiency building (blue line) to a level below the flow temperature of the low- efficiency building (yellow line). The preheated energy stream serves as input stream for the two high-temperature heat generation units. This interconnection of the heat generation units allows an efficient use of the heat pump, due to a low target temperature, and a decrease in energy demand from the high-temperature heat sources. The simultaneous operation of electricity generating (gasification with CHP) and consuming unit (heat pump) is favourable to avoid grid levies and make the generated heat 100 % renewable. The top storage tank is a buffer for high-temperature heat and allows a continuous operation of the gasifier with CHP, while the lower storage tank especially serves as hydraulic compensator between the heat pump and the high-temperature heat sources. For balancing the fluctuating wastewater stream, a third storage tank for low-temperature heat might be suitable (left to the heat pump).
Figure 2: Composition of heat supply by generation unit of overall 4.4 GWh
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