Research shows that surface water can be a substantial source of sustainable heat, as an alternative to natural gas. It is a potential source for heating and cooling of buildings (STOWA, 2018). Aquathermal is a technology that enables to extract thermal energy from water, store it, upgrade it to a higher temperature using a heat pump, and finally deliver it to buildings. There are three different heat sources that can be used: 1) surface water such as lakes or rivers 2) waste water and 3) drinking water. Waste water and drinking water have lower potentials compared to surface water (CE, 2018). This factsheet focuses on aquathermal from surface water.
Surface water has a temperature varying between 7 and 25°C over the year making it a very low temperature heat source. Aquathermal comprises a storage technique that works in a way similar to aquifer thermal energy storage (ATES). During summer months surface water is stored in a reservoir (aquifer) and used for heating in winter months. The stored water can also be used for cooling. If necessary, the surface water can also be used as a supplement to the cooling capacity of an ATES (CE, 2018). The heat cold balance of the aquifer is restored by adding surface water. The technique makes use of pumps and heat exchangers at the reservoir. A heat network is used to transport low temperature heat to consumers. A collective heat pump is used to increase the temperature to a suitable level for space heating and hot water. Alternatively, an individual heat pump can be used.
This factsheet includes the above mentioned system components: heat extraction, storage, heat network and heat pump.