Hot water using the sun's rays

Marleen Gysen and Kristof Severijns, Innovation Support Consultants


Practical example

A French calf shed with 200 calf places

This farm in Livré-La-Touche needs 800 litres of water at a temperature of 75 ° C twice a day to prepare calf feed. Before they put the solar thermal system into use, the water was completely heated with a gas boiler. For this, they had to purchase about 4.4 tons of propane annually. That corresponds to a total energy content of 56,320 kWh (1 kg propane = 12.8 kWh, so 4400 x 12.8).

In 2013, with the help of the agricultural cooperative CAM-Inovia (Cooperative des Agriculteurs de la Mayenne), a solar thermal system was installed with a patent from Fengtech. The installation consists of 4 modules, with a total of 120 vacuum tubes and 4 boiler vessels with a total volume of 1200 litres. Such systems capture 3 types of solar radiation: direct, diffuse and reflected radiation. The energy collectors (the vacuum tubes) work even in cloudy weather and are protected against overheating. The vacuum is a natural insulator, so the system is not very sensitive to the outside temperature. The boiler tanks are made of stainless steel and insulated with 60 mm polyurethane. The pipes at this calf farm have a surface area of ​​18 m², with which the radiation can be collected.

When there is no radiation, a back-up system (in this case the original gas boiler) takes over the heating of the required water. The system is not under pressure. In most French companies, this installation is on the ground, on a concrete slab that is painted white for optimal reflection of the solar radiation.

Thanks to the savings they achieve with the solar boiler, the veal farm only needs to purchase around 2.8 tons of propane annually. This corresponds to an energy-saving of 20,480 kWh / year and a CO2 reduction of 6.3 tonnes/year.

Are you eligible for project support?

Marleen Gysen, innovation consultant Innovation support centre: "Do you need hot water at your company every day, even during the summer? Are you interested in installing a solar thermal system yourself and thus reducing your heating costs for the production of hot water? with you whether you are eligible for project support.

Marleen Gysen and Kristof Severijns are ready to guide you. Interested? Send an email to

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