Approach now available for monitoring the ecological effects of aquathermal energy

Published: 26 June 2020

Monitoring the ecological effects of the large-scale introduction of aquathermal energy is important if it is to be used as a sustainable source to heat homes and business premises. In the context of the WarmingUP knowledge programme, Deltares has developed an approach for monitoring the ecological effects of extracting thermal energy from surface water (TEO). TEO is a form of aquathermal energy. Water authorities and heat suppliers can use the approach to properly monitor the effects of cold water discharges and to observe the ecological functioning of a water system.

TEO systems take heat from surface water in summer and store it in the subsurface so it can be used in winter to heat homes and other buildings. Extracting heat from the surface water means that colder water is returned to the system. Systems in operation at the district level in recent years have not yet given us a complete picture of the effects on the ecology. There are indications that cold discharges can lower the temperature and therefore improve clarity and reduce nutrient concentrations. However, we do not yet know how the large-scale deployment of TEO will affect ecology in the longer term. It is important to monitor TEO installations, not only to make sure the ecology of different water systems is not negatively affected by TEO, but also so that we can use the data to establish a picture of the effects of TEO: how does a cold water discharge spread through a water system and how do algae, plants and fish respond? This knowledge about effects can help water managers during permit procedures.

Three monitoring levels

What to monitor depends on the expected scale of the cold discharge, the expected sensitivity of the receiving surface water body and the degree of interest in knowledge development. Three monitoring levels have therefore been defined: the basic level ‘know what you are discharging’, a more extensive approach to monitor the ecological status on the basis of WFD monitoring, and an extended version that involves monitoring the direct impact on species and their development. ‘The idea is to measure and monitor what you extract and discharge, and to keep an eye on what is happening so that you can intervene where necessary,’ says Ida de Groot-Wallast, a Deltares expert. The largest effects are expected in the spring and it is important to conduct measurements over a period of several years.  We can use the data from the most detailed monitoring option to investigate possible links between temperature differences, spread, water biochemistry, and flora and fauna. The monitoring plan can be downloaded (available in Dutch only) from the WarmingUP website.

WarmingUP and aquathermal energy

The monitoring plan is part of the WarmingUP knowledge programme and it is one of the first products to be completed for the Aquathermal Energy theme. WarmingUP is a collaborative venture involving more than forty parties from the entire heating sector who are working together to develop practical knowledge so that collective heating systems will be reliable, sustainable and affordable for the purposes of the heating transition. On the basis of the development of knowledge in this programme and the collaboration with the Aquathermal Energy network, we will combine our efforts to ensure that aquathermal energy becomes a genuine alternative for the collective heating and cooling of homes and other buildings.