The 2SaveEnergy greenhouse is reconstructed last fall. With these adaptations we can make a next step in reduction of the energy consumption, without having adverse effects on the crop.
Double aluminium screen plus a transparent screen
A second screen installation to further reduce heat loss is installed. After extensive consultations and calculations we concluded that the optimal combination of screens would be a double aluminium screen on the existing system and a transparent screen on the new system will result in the lowest energy consumption. On a cold day during daytime just one screen can be closed. The cold and dark days mid of February this was noticeable. But the profit comes from the high saving of the double aluminium screen during the long winter nights.
Dehumidification with recovery of latent heat
Another important change is made to the dehumidification. In the old situation there was a simple external air inlet with a heater to bring the cold outside air towards greenhouse air temperature. The disadvantage was that both, sensible and latent heat from the dehumidification was lost. By placing a heat pump we can produce cold and thus we can dehumidify through condensation. The heat from the heat pump is not completely necessary to reheat the dry but cold air after the condensation phase towards greenhouse temperature again. What is left over is brought into the pipe-rail system to heat the greenhouse. When the installation is running, there is a constant flow of water from the condensation unit, so it functions properly. End of March there was a total of 10 l/m2 dehumidified with the aid of the heat pump. We have used 6 kWh electricity for the heat pump, which has yielded another 21 kWh of heat per m2. Now with this beautiful weather end of March you can see its limitations, we have some excess heat. On gas, there is in total from January 4th 4.6 m3/m2 used.
Snow on the cover
Snow is one of the topics that calls attention to this greenhouse concept. Unfortunately, snow cannot be ordered on demand, but two and a half years after completion, we had the first good opportunity to test the melting of the snow. The heating tube inside the gutter appeared to do what was expected of it.
On January 4, the tomato variety Cappricia (RijkZwaan) with a stem density 2.5 pc/m2 was planted in the greenhouse. On February 3td, the plants were replaced to the plant hole on the slab. In week 6, there is one on two stems an additional shoot started. Unfortunately by the low light conditions in week 7 the shoots showed too much inequality so that the next shoot is used to increase stem density to 3.75 per m2. It is grown as much as possible according to the principles of The New Cultivation method. By maintaining fairly high temperatures we tried to create a not too heavy crop. Now with the 9th truss flowering the first fruits starts colouring, next week begins the harvest.
The 2SaveEnergy-greenhouse is financed by the program ”Kas als Energiebron”, the innovation and action program of LTO Glaskracht Nederland, the ministry of economic affairs, Van der Valk systems, VDH foliekassen, Ludvig Svensson and Lek Habo.