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Heat Pumps Technology Guide SEAI Injecting waste heat into the ground increases heat recovery, which improves heating efficiency. This strategy can also reduce the size requirements of the collector system, as heat is removed (in heating mode) and injected (in cooling mode) throughout the year. When a ground-source (or water-source) heat pump system replaces chillers for cooling, both cost and emissions can be significantly lower. The feasibility of this option should be considered at the design stage, to ensure that the design of the ground- (or water-) source system can accommodate it, the heat pump can be appropriately specified, and the hydraulic system in the building can be appropriately designed. Disadvantages In a ground-source heat pump system, particularly horizontal collectors, there is a finite thermal resource that can be depleted. Systems that extract only naturally occurring (renewable) heat depend on solar gain, rainfall or geothermal energy which may vary. That is why ground-source heat pumps are more sensitive to the operating hours, profile of heat supplied, and total heat delivered, than other types of heat pump. For example, particular care needs to be taken with delivering heat to dry out a new building after construction (e.g. if it has underfloor heating with solid floors). This can be a significant heat load that can deplete the ground energy store if it has not been not allowed for. Close to the surface, geothermal energy is negligible, so horizontal trenches rely on solar gain or rainfall to replace the heat extracted by the heat pump system. Excessive removal of heat (which exceeds the capacity of a site to recover the temperatures) can result in low ground temperatures around the heat source system, making the system inefficient. Solutions include: • Injecting waste heat; • Increasing the capacity of the ground-source system (if possible); and • Reducing the load on the ground-source system, for example by installing an air-source heat pump to provide some of the heat. Monitoring the amount of heat extracted (kWh) and the heat source temperatures using a heat meter can help to ensure that the system is operating within its design conditions. This also provides an early warning of any problems, so that remedial work can be planned. Ground-source heat pumps use antifreeze in the source loop to prevent it freezing. The viscosity of the antifreeze can vary significantly at low temperatures. So, if the source temperature does fall (e.g. because of lack of circulation caused by a blocked filter or an unexpectedly high heat load), this can increase the viscosity of the antifreeze, in turn increasing the pumping effort required. The increased pumping effort can mean that the optimum flow rates required are not achieved and the system stops working (low refrigerant pressure fault). The careful design and installation of monitoring equipment can identify these potential issues early on. More details are given in the accompanying Operation & Maintenance Guide. 3.2.4. Water-to-water Heat pumps can extract heat from surface water bodies including rivers, lakes and the sea, and from groundwater. Water-source heat pumps can be used at any scale, but the largest heat pump systems, which can be more than 10 MW, tend to use water sourced from the sea or major rivers. 15PDF Image | Heat Pumps Technology Guide
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CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
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