Existing areas energy-neutral with an innovative solar heat network

Published: 9 December 2020

A solar heat network has proven to be technically and financially feasible for making existing areas more sustainable and eliminating the use of gas, finds a consortium of scientists and companies led by Delft University of Technology. The consortium has worked on the technical side of this concept. It has also made the technical and financial calculations for the area Ramplaankwartier in Haarlem that was built in the 1930s. In addition, a test array in The Green Village in Delft has demonstrated that the system works. So there is now a design in place for the sustainable heating of houses in an entire area, without an external heat source being needed.

In order to achieve the goals of the climate agreement, a lot of hard work is going into finding ways to make existing areas and buildings more sustainable and to disconnect them from the gas mains. The solar heat network is one of the possible solutions that has been developed and tested over the past year. The solar heat network consists of PVT panels (solar panels that generate both heat and electricity) on roofs, a very-low-temperature heat network linked to a heat/cold storage system below ground and a heat pump in every home. The homes are supplied in an energy-neutral way with hot water, heating in winter and cooling in the summer.

Smart heat distribution

A special ‘delivery set’ – a cabinet with pipes, pumps and valves – ensures that the heat from the heat network and the PVT panels is used optimally. In summer, all the surplus PVT heat is stored in the underground store using the network. In the intermediate seasons, heat is supplied by both the PVT panels and the network from the thermal energy store. In winter, the heat mainly comes from the thermal energy store, maximising the efficiency of the heat pump. A test array with the solar heat network has been built and successfully tested at Delft University of Technology’s Green Village.

Design completed for a sustainable area solution

The results of the study in Haarlem and the test array in Delft are convincing. The detailed design of the solar heat network has now been completed: the required number of PVT panels for each home has been determined, as have the required temperature levels for heat storage and heat distribution. In addition, the stable functioning of all the settings in conjunction has been tested. The conclusion is that the system works in technical terms and that the houses in the area can be supplied with enough heat all year round with the help of the panels and the solar heat network. There is enough electricity from the panels to drive the heat pump.
That means the system is energy-neutral for heating. Ivo Pothof, a researcher at Delft University of Technology and Deltares, is enthusiastic about the solar heat network: ‘It is the most sustainable area solution for existing buildings that I know of because it maximises the use of local energy with the PVT panels. The concept has been extensively compared with other solutions for existing residential areas and comes out at the top.’

Financial feasibility

The solar heat network has also proved to be an interesting concept financially. It requires a substantial investment at the outset but, after that, there are no more variable energy costs. That means that the solar heat network will be cheaper than gas and most other alternatives after a few years. The annual costs then consist solely of maintenance and the repayments of the investment. The electricity supply for the heat pump is generated by the PVT panels and no upgrade of the electricity mains is needed because there is no peak consumption in winter. Assuming adequate levels of participation in the area, and low interest rates, the solar heat network is therefore a promising solution in financial terms as well.


The consortium, which consists of Delft University of Technology, Deltares, Greenvis, Stichting SpaarGas, Triple Solar, Fortes Energy Systems, the WarmteTRansitieMakers, ENGIE and the city of Haarlem, hopes that the solar heat network will go into widespread use for making existing areas more sustainable.

The website www.zonnewarmtenet.nl (in Dutch only) describes the results of the research. Administrators and other decision-makers can also find more information here about the solar heat network. Ivo Pothof: ‘Now that the effectiveness of the solar heat network has been proven, it is important to inform interested parties about the potential as clearly as possible. The aim is to make even more existing areas energy-neutral.’

This project DeZONNET was made possible in part by the Top Sector Energy Subsidy, TKI Urban Energy, of the Ministry of Economic Affairs and Climate, reference TEUE018017 for Low temperature feed-in solar heat networks.