The heating systems have more functions then just heating up the greenhouse.
The system can also be used as a transport system. Tube rail cars can run over the rails or mono rail cars can be used to transport items overhead.
The heating system can also be used to get rid of the humidity inside the greenhouse. By heating up the greenhouse in the early morning the heated air will rise and taking the humidity along through the opened ventilation system.
The hot air systems are heaters that are located in the greenhouse.
They burn on gas or light oil. The initial investment of these heaters is very different from the hot water system but also the functionality and quality is very different.
Some heaters have a exhaust pipe while others blow the exhaust gas directly in to the greenhouse.
The hot water system is used in the modern projects and can run on natural gas, coal, (heavy of light) oil, wood etc. The boiler is located in a separate area of the service building. Burning natural gas the CO2 can also be transported to the plants for better growth. The hot water is transported through pipes to the different compartments.