Wetenschap - 12 april 2017

WUR tests Chinese solar greenhouse

tekst:
Albert Sikkema

Today, a Chinese solar greenhouse was opened at the WUR Greenhouse Horticulture research location in Bleiswijk. This Chinese greenhouse allows for the cultivation of vegetables in sub-zero temperatures using only solar energy, but also has several drawbacks. WUR hopes to solve these in collaboration with Dutch companies.

Photo: WUR Greenhouse Horticulture

The highly productive Dutch greenhouse horticulture holds a leading position on the worldwide market, but it still depends on fossil fuels. Many vegetable farmers in China use a different kind of greenhouse, with which they grow vegetables using solar energy. These greenhouses, which consist of a plastic dome and a thick wall that stores solar heat during the day and releases it at night, resemble the lean-to greenhouses that were built in the Westland region 140 years ago, says Eric Poot of WUR Greenhouse Horticulture. A modern version of these greenhouses now stands in Bleiswijk.

Air humidity
Poot thinks the Dutch technology providers will be able to improve the production in this Chinese solar greenhouse, as it still has several drawbacks. The biggest is that the air humidity in the Chinese greenhouse is too high. This causes many diseases and plagues in the greenhouses, which the Chinese farmers suppress with large quantities of chemicals. The Chinese test greenhouse in Bleiswijk has a ventilation system to prevent this complication. The test greenhouse will cultivate vegetables on substrates. The advantage of this approach is that the farmer doesn’t suffer from soil diseases and can install environmentally friendly circulation systems for water and nutrients.

Insulation
Additionally, the test greenhouse in Bleiswijk will be insulated differently than the common Chinese solar greenhouses. In China, the greenhouses are covered at night using a kind of thick horsecloth that keeps the solar heat inside. In Bleiswijk, WUR slides an insulating and translucent panel beneath the plastic dome. The advantage of this is that the greenhouse also utilises the sunlight when it is cold.

Demonstration setup
WUR Greenhouse Horticulture is investigating whether the Dutch climate control in the greenhouse leads to a higher production and fewer diseases and plagues. WUR does this together with a consortium of Dutch companies that would like to sell their technology on the Chinese market. But are the Chinese interested? They are, observes Poot, who recently visited China to assess the greenhouses. ‘They immediately asked why we weren’t building this demonstration greenhouse in China. We are currently building it in Bleiswijk because many Chinese delegations visit us and want to know what we could contribute to the horticulture in China. If the results will be positive, I do not rule out that we will build another demonstration greenhouse in China. All contributing companies sell climate control equipment in China, but with this approach, we could set up an integral concept for a highly productive solar greenhouse.’

Curious
Conversely, Poot can also learn from the Chinese solar greenhouse. ‘I am curious about cultivation without the use of gas, merely using solar energy. We are also curious to see how much heat the greenhouse can store during the day and how much can be released during the night. Besides, how will the vegetables react to the differences in temperature?’

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