Chinese – Dutch cooperation on the Chinese Solar Greenhouse experiment in Shouguang

The Chinese Solar Greenhouse is simple but has a low productivity. To improve this, the inner greenhouse climate will have to become more controllable. To contribute to this, but keeping the passive character of the greenhouse, meaning that it doesn’t need additional heating, the Chinese Academy of Agricultural Science has developed the Active Heat Storage and Release System (AHSRS). By switching on and off a pump that runs water along large panels along the north wall the gathering of heat and the release of heat can be controlled. This project shows that the AHSRS does not affect the diurnal average temperature in winter, but can elevate the minimum temperature by some 2 °C. On dull days, however, the AHSRS doesn’t give an improvement since it doesn’t add anything to the shortage of energy. The fact that the Chinese Solar Greenhouse prevents frost, despite outside temperatures that may go down far below ‑10 °C is largely due to the high insulation applied. The insulation can be further increased by using screens inside the greenhouse. This project shows that such a screen may elevate the temperatures on the coldest days with about 1.5 °C and in Chinese Solar Greenhouse with the AHSRS even slightly more. When using a transparent screen like the Ludvig Svensson Luxous screen, the elevated temperature in winter comes together with a slightly increased amount of light entering the greenhouse. In warmer months of the year, the light entrance to the greenhouse will be reduced somewhat when using a thermal screen. Apart from temperature, also the humidity is often unfavourably high in the Chinese Solar Greenhouse. This report shows a simple system to reduce the high humidities in winter at the expense of about 7 kWh/m² of electricity per year. Another topic studied in this project was the use of soilless cultivation. The equipment, consisting of a irrigation and nutrient supply system, drippers and coco fiber slabs, worked well and contributed to a good an healthy crop. To achieve this, the greenhouse operator was helped a lot by the Delphy advisory service. The control of all actuators and measurement of the greenhouse and outside climate was carried out by the Hoogendoorn ISII greenhouse climate computer. After a short period the operator of the greenhouse learned how to use the outputs of the climate computer and its control capabilities to realize the best possible climate with the given, limited number of control possibilities of a Chines Solar Greenhouse. The harvest in terms of tomatoes in this first experimental period was about 5.5 kg/m². This is still very low, but largely due to the start-up character of this first year. It is stated that a production of 20 kg/m² is reasonable to expect, providing a good support by a knowledgeable adviser