Tips for Selecting a Greenhouse Heating System
Boyan Dulitz – Engineering Department Manager
The greenhouse heating system is clearly one of the "heaviest" investments, both as an initial investment and the high, routine operational expenses.
Therefore, it is most important to invest in preliminary planning and to select the most efficient and the most economical system, in accordance with the geographical location of the project and the type of crops being grown.
Heating systems fall into two main categories:
- Hot Air Heating Systems (Heating by Convection)
- Hot Water Heating Systems (Radiated Heat)
The main parameters for choosing the appropriate heating system are:
- The conducting of a proper thermal calculation by a professional – according to the type of crop and the geographical location of the project, the project planner can offer the best array of greenhouse systems in order to turn the greenhouse into an effective and efficient production line. In countries with cold weather conditions, for example, heating expenses can reach up to 60% of all routine operational expenses. In many cases, the chances for achieving a successful and profitable project are determined by the planning of a proper heating system. Thermal calculations need to take various types of coverings into consideration, as well as levels of isolation, including thermal screens. The end result is a number that signifies the amount of energy invested per square meter. It is usually noted in kilocalories per hour or kilowatts per hour. Although this figure indicates the output of the system, additional criteria must be taken into account in order to choose the "right" heating system.
- Available sources of energy: this parameter is very important and an in-depth examination should be conducted. For example, if the project is located near a power station that uses water for cooling its systems, the station could become a supplier of hot water or steam for heating the greenhouse. This arrangement would significantly reduce the initial investment in a heating system and lead to considerable savings on routine heating expenses. Heating systems vary from country to country, depending on sources of energy. Radiation from the sun also serves as a source of energy and should be taken into consideration when planning a greenhouse project. The angle of the greenhouse rooftop should be determined by the latitude of the project site and the angle of the sun during the winter months to ensure optimal exposure to the sun's rays (as close as possible to a 90° angle between the rooftop and the sunrays).
- Fluctuations in temperature gradients: There are quite a few areas with relatively large fluctuations in day and night temperature gradients. In Israel, for example, even during the winter months there are many warm and clear days that require only minimal heating, if at all. In such cases, it is better to take advantage of heating by convection (hot air heaters), equipped with an on/off switch for quick, almost immediate response. Hot water heaters take relatively long amounts of time to begin operation and energy is "wasted" when the system is turned on and off at periodical intervals. These heaters are more effective in places requiring continuous heating over extensive periods.
Azrom is currently one of the world's leading companies for the production of greenhouses.
Every project, anywhere in the world, receives the proper, individual consideration, combining: local characteristics, design and planning, agronomic consultation, examination of growing conditions, construction and the planning of supplementary units and systems, including electricity, water, heating, trellising, climate control and fertilization. Only an overall, comprehensive solution, be it simple or complex, is the perfect response.
The company's quality control policy focuses on the supply of qualitative products for long term client use under difficult and challenging field conditions.