Lessons learned from experiments with semi-closed greenhouses

In the past decade, experiments and a large number of model studies with closed and semi-closed greenhouses have been carried out. Technical, horticultural and engineering problems were solved and high production levels were achieved. Due to the capture of condensate and the reduced air exchange, water and CO2 demands can be reduced significantly. However, the investments for a semi-closed greenhouse are high. Moreover, the running costs can be high as well, especially in situations where seasonal heat storage is difficult. This paper gives an overview of the results obtained by several research institutes as published in international accessible literature and discusses the key parameters that affect the technical and economic viability of semi-closed greenhouses.