Heat generating greenhouse made from wood – Vacuum Insulation System (VIS)

Using birch plywood, Aalto University researcher Pasi Herranen developed a greenhouse element that is now in use in a greenhouse built in Piikkiö last spring.

The greenhouse elements have an aluminium coating less than one millimetre thick. This coating reflects light onto the plants and also enables element maintenance by vacuum drying. According to preliminary calculations, the amount of carbon sequestered by the wood frame is higher than the carbon emitted in the manufacture of the aluminium coating. Photo: Mikko Raskinen / Aalto-yliopisto

Compared to a traditional glass greenhouse, Herranen’s design saves energy, water, soil, and nutrients. His new invention consumes only half the usual amount of energy in year-round cultivation in Finnish climate conditions. The invention works in freezing Finnish weather and under the scorching Saharan sun alike.

Compared to a traditional glass greenhouse, Herranen’s wooden one consumes only half as much energy and 95 percent less water in Finnish conditions in yearround cultivation. The secret is the fully sealed wall and ceiling elements made of birch plywood. For their maintainance, Herranen came up with the idea of vacuum drying, which uses evaporation to remove excess moisture bound to the wood. He also designed a special wooden interior structure between the plywood boards to keep the element intact under the high pressure of vacuum drying. The invention’s patent is currently pending.

The elements are coated with aluminium, which reflects the light from the LEDs onto the plants. To grow, the plants use only four percent of the energy provided by the LEDs. They convert the rest into heat.

− In future, we will be able to dramatically increase vertical cultivation, which will further increase the hall’s heat load. According to my calculations, up to 90% of the energy used for lighting could be fed into the district grid as thermal energy, meaning that greenhouses could become heat producers, says Herranen.

Read the article in Finnish: Puinen lämpöä tuottava kasvihuone – Vacuum Insulation System (VIS)