Heat transfer to drinking water mains

The warming of the soil around a drinking water main can make the temperature of the water in the main rise above 25 °C, which means that the water no longer satisfies the requirements of the Dutch Decree on Water Quality. This occurs occasionally and in a localised manner during heat waves, but it can also occur sooner if there is a heat pipeline or power cable in the vicinity of the water main. The combination of a lengthy period of hot weather and a neighbouring heat source can therefore be critical in this context.

The installation of heat pipelines underground is expected to increase rapidly in connection with planned city-heating projects and the strong growth of aquifer thermal energy storage (ATES) systems in the Netherlands.

We can expect that water mains with relatively long drinking water residence times – i.e., the distribution mains to the end-users – will be subject to the greatest risks.

Controlling undesirable warming of drinking water mains

The undesirable warming of drinking water mains can occur because of heat waves, heat pipelines and power cables. This project involves the development of a design-calculation model. For new situations, this method generates recommended distances between water mains and heat pipelines or power cables. For existing situations, the calculation model can be set up in such a way that, in a follow-up process, it can also be operationally used in an early-warning system to control the drinking water temperature and quality, and thus allow for the timely implementation of measures to prevent exceedingly high temperatures.

Modelling drinking water temperature in the network under influence of power cables and heat networks

This applied research project is being conducted by Deltares and KWR; field measurements carried out at concerned water companies are to be used for validation purposes.

To begin with, a 2-D model is made of the soil surrounding a drinking water main that is subject to thermal load from the surface and from a neighbouring, parallel heat pipeline (or power cable). The thermal load below the surface is taken from the 1-D soil-warming model, which was developed in the TKI Calorics project. The results of the 1-D Calorics model and the 2-D model are compared. Then, the WANDA Heat model (Deltares) is extended with a dynamic modelling of the soil shell in 2, 3 or 4 parts, so that the dynamic warming and cooling of this soil shell around the water main can be correctly modelled under the influence of heat fluxes from the surface and a lateral heat flux from a heat pipeline or power cable. Available field measurements are used to test the improved modelling. If necessary, a limited and targeted measurement campaign will be set up.

Recommended minimum distances between drinking water mains and heat pipelines or high-voltage cables

Based on the validated models, recommendations are to be made to improve the design methodology regarding minimum-recommended distances between drinking water mains and heat pipelines or power cables.

This will be the basis of a draft Netherlands Technical Agreement (NTA), whereby the results can be implemented nationally.