What are the heating systems based on conventional fuels?
Traditionally, glass greenhouse structures have been heated by hot water systems. Most of the largest commercial greenhouses are heated by using some kind of the boiler system. Gas-fired unit heaters for greenhouse heating deliver heat at approximately half of the cost of the steam/hot water systems. The hot air will be distributed through a perforated poly tube which runs along the length of the greenhouse. Both radiative and convective electric heaters are easy and convenient to control. As there is no electricity available and also because of the high cost, its use is limited to a small greenhouse and experimental greenhouse. The heating systems should not only raise the temperature of the greenhouse, but should also achieve uniformity in the distribution of temperature. Hence, selecting heating unit placement and the type of distribution system is the most important decision to be taken.