Dutch heat battery cools and heats greenhouses while saving up to 30 percent energy

A heat battery that cools greenhouses during the day and heats them at night. Which uses no electricity and emits no gases. With which growers can save 10 to 30 percent on their energy use. After years of successful testing, Dutch start-up Thermeleon will deliver its first heat batteries to growers of vegetables and ornamental plants this year.

A greenhouse is a wonderful invention for growing crops all year round even where cold or hot climates make it difficult to do so. Daylight enters through the glass windows and is converted into heat, which the greenhouse retains. Only that heat is not always there at the right time. It can get too hot in the greenhouse during the day, while that heat is needed in the evening or at night because it is too cold then.

Thermeleon's heat battery stores that heat from the day for free and releases it at night, saving energy. During the day, it cools the greenhouse and the windows can stay closed more. Too much window ventilation now leaks out CO2, which is important for plant growth. When a grower actively cools, the Heat Battery also saves on electricity. The battery provides a more stable indoor climate, with less heat and cold stress for the crop, which is good for crop growth.

Brick wall

The concept is somewhat similar to the brick walls, the "fruit walls," introduced in Holland and Belgium in the late Middle Ages, where crops were planted next to them. Those bricks gave off the day's stored heat in the evening. Today's modern Chinese solar greenhouse still uses this effect. "Such a wall enabled us to grow the first Mediterranean fruits in Holland in the 16th century. In today's high-tech glass greenhouse, we have kind of forgotten that concept. What we are doing is bringing the old concept of heat-buffering elements back into the greenhouse in an innovative jacket," said Thermeleon founder and CEO Jildou de Jong.

World first

The Thermeleon heat battery is not a traditional battery with battery cells or electrolytes, but consists of different forms with so-called Phase Change Materials (PCM), which can be applied in different places in the greenhouse. Those elements charge and discharge passively through temperature differences. When those materials change from solid to liquid (melting) they absorb heat and cool the environment. When the temperature drops, they change back from liquid to solid (solidify) and return the stored heat.

"It is a passive system that uses no energy and emits no gases. The operation of these materials has been studied many times, but it has never been applied on a commercial scale in a high-tech greenhouse. We succeeded for the first time in designing a heat battery specifically for high-tech greenhouses, and launching it in a 1-hectare greenhouse. A world first," says De Jong.