Heat source systems (Chapter 9.2.1 and 9.2.2) and heat pumps (Chapter 9.2.3) are integrated into overall systems that enable the utilisation of ambient air or shallow geothermal heat as end and useful energy respectively. Therefore firstly typical system configurations for characteristic applications are described. Afterwards system aspects of such overall systems will be discussed.
System configurations. In the following, a heating system with exhaust air heat recovery and exhaust-air to inlet-air heat pump, with a ground-coupled heat pump and a heat pump system for heating and cooling purposes will be introduced as typical overall system configurations.
Heating systems with exhaust-air to inlet-air heat pump. Over the last few years, exhaust-air to inlet-air heat pumps have been especially developed for houses with a very low heating energy demand and controlled ventilation systems. Not only do they cover the entire demand for space heating energy by heating up the inlet air, but can also cover the domestic hot water demand to a large extent. Fig. 9.14 shows exemplary such a heat pump unit. The inlet air is heated further by the heat pump condenser after exhaust air heat recovery. The evaporator is allocated in the exhaust air duct after the exhaust air heat recovery heat exchanger. In order to reduce icing of the evaporator on the exhaust air side, one option is to position a ground-coupled heat exchanger between ambient air and the exhaust air heat recovery heat exchanger. Thus the exhaust air in the heat exchanger cannot cool down so much. The way the cooling fans are allocated enables their exhaust heat to contribute to the heating process (i.e. in the exhaust air duct before the heat exchanger of the exhaust air heat recovery and after the condenser in the intake air duct). If enough heating energy is available for the house, the heat pump switches to the condenser of the domestic hot water generation system. Furthermore, an additional thermal solar system can be used to generate domestic hot water. During cold and cloudy periods in winter, an electric immersed heater is available as a back-up for the domestic hot water supply. Such heat pump systems can achieve SPFs of up to 3.5 /9-15/.
Heating systems with ground-coupled heat pump. As an example, Fig. 9.15 shows a heat pump heating system with a horizontal ground-coupled heat exchanger. The heat pump primarily supplies space heating water in this case. Domestic hot water generation that would require a higher temperature level, in principle could also be realised using a heat pump, but also using a separate heater. The heat pump directly feeds a low-temperature floor heating system. Due to the storage capacity of floor heating systems, a buffer storage might not be required. Only for an increased demand towards indoor temperature quality (e.g. balancing of temperature within a building, for example with appropriate solar radiation) or if throttling of individual heating circuits is required, a buffer storage may be needed. An appropriate control device steers the heat pump that is normally run with On/Off operation - depending on the required space heating inlet temperature and ambient temperature. Due to the high storage mass of the heated building surfaces (e.g. stone floor, concrete floor) the On/Off operation of the heat pump does not lead to a loss in comfortable room temperatures.
Floor heating system
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