project

Calorics

The temperature of water in the distribution network is influenced by the weather, the surroundings and the soil. Climate change and urbanisation will also in the future possibly lead to excessive warming of the drinking water. Water at a temperature that rises above 25°C no longer meets supply stipulations, since increased microbial activity can occur under these circumstances. Water companies recognise that this is a serious problem and study possible means of preventing it.

Challenge

The objective of this project is to research the technical and financial feasibility of solutions for a climate-proof distribution network by means of case studies. The measures involved should prevent the undesirable warming and microbial regrowth resulting from climate change. One of the solutions involves to cooling the water through the implementation of aquifer thermal energy storage (ATES) systems, so that the thermal energy that is present in the drinking water can be made use of.

Solution

This project has provided insight into the technical and financial feasibility of four solutions for a climate-proof distribution network, namely: changing installation requirements; changing pipe materials; shortening residence times; and active cooling, including the implementation of ATES; as well as combinations of these solutions. The investment and operational costs of these measures were also studied. Flushing is the cheapest option, while the deeper installation of pipes is very costly and thus not opportune. The use of a heat exchanger with ATES would be about half as costly as deeper pipe installation; the option has the added advantage that excess cold can be used to satisfy local cooling demand (cooling water). This has a positive impact on the business case.

The use of a heat exchanger with ATES prior to distribution is an interesting option at the water-energy interface. Cooling the drinking water before its distribution does not increase the energy used by households to heat the water. To research the combination of temperature and residence time, a surrogate parameter for water quality was used. The use of a heat exchanger with ATES has a positive impact on this surrogate parameter. And no negative impact was found when, in the winter, heat is added to the drinking water in order to load the ATES with cold. This is positive for the ATES, because cold can possibly be extracted from the drinking water without there being any significant consequence for the quality of the drinking water in the pipe. Flushing has a similar impact on the surrogate parameter. Follow-up research is needed to better determine the consequences for water quality.