How Expensive Is Heating In Greenhouses
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by: derek fitzgerald
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How Expensive Is Heating In Greenhouses
How expensive is heating in greenhouses if we are to maintain an acceptable temperature range throughout the year in Britain. To grow certain plants there has to be some form of artificial heat , but we must ask ourselves the question "How Expensive Is Heating In Greenhouses " . There have been rapid developments in heating methods during recent years and further progress can certainly be expected. The emphasis is on entirely automatic, or at least semi-automatic, systems which absolve the gardener from any work or worry, although not all gardeners are prepared to pay for this level of sophistication, at the outset at any rate. There are many different ways of heating a greenhouse, or sections of it, i.e. the border soil or propagating bench. The following are the main methods:
I By an arrangement of water-containing pipes, the water being heated initially by a boiler 'fired' with solid fuel, oil, gas or electricity. Simple types of solid fuel boilers cannot be considered automatic, whereas more refined types operate with ease on a semi-automatic control system. There is no control problem at all with more refined oil, gas or electric boilers. Electricity also is of course required for the operation of the majority of automatic types.
2 Oil heaters with either free discharge or ducted heated air. These can be of either simple design, such as oil stoves, or with pressure jet or vapouriser burners, with or without assisted air discharge by means of fans. Electricity is again required for pressure jet burners, and the operation of fans. Simple types of oil heaters must he controlled manually
How expensive is heating in greenhouses if they are controlled electrically or be operated on a thermostat
3 Entirely by electrical apparatus in various forms, all of which are ideal for automatic control.
a) Soil or bench warming cables which have little effect on the greenhouse air temperature.
b) Mineral insulated (M.I.) cables for installation around the greenhouse perimeter, these being held in porcelain clips.
c) Tubular heaters of various sizes and designs which are generally fitted on perimeter walls.
d) Fan heaters which can be sited anywhere, but are generally freestanding in the centre of the greenhouse, unless of course they are the larger type fan heaters which can be sited at one end of the house, the hot air being distributed by perforated polythene ducts, as also can be done with oil fired fan heaters.
e) Storage heaters. Opinions vary concerning the use of these in a greenhouse owing to problems of temperature control.
How Expensive Is Heating In Greenhouses Using the Various Options Available
This depends on many factors, apart from the basic cost of the fuel. The main factors are the desired heat level and the percentage efficiency of the heat producing unit as, with all systems of heating involving combustion, there is always a proportion of heat wasted, generally into the atmosphere through the flue pipe. Although freestanding oil heaters have no outside flue, there is still an efficiency loss on combustion. Fuel supplying bodies are generally happy to provide reasonably accurate average running costs, based broadly on the general principles stated here.
DISTRIBUTION OF HEAT
Another important matter relates to the distribution of heat once it is produced, it being desirable to design a system which will give an equable and even heat dispersal throughout the whole greenhouse area, especially for heat demanding crops in cold weather. Hot water pipe systems are ideal, as they can provide a warm curtain around the outside of the greenhouse. They transmit the heat largely by convection currrents, as hot air rises. Heating can be most efficient, provided the pipes are maintained at the same temperature throughout their length. The pipes also transmit a considerable amount of radiant heat, which can be valuable for soil warming purposes where heat-loving crops such as tomatoes are involved, and also for many plant growing and propagation activities on benches.
Non-directional heaters of any type merely transmit their heat entirely by convection and consequently are not considered as ideal for uniform heat distribution, especially in very cold weather or where cold winds prevail along one side of the greenhouse. Directional heaters with fans are more efficient, but there can also be distribution problems naless perforated polythene ducting is employed to disperse the heated air uniformly around the greenhouse.
Heating engineers and equipment suppliers are well aware of the need for good design with any heating system, and a wealth of good advice is also available from the advisory bodies associated with all fuel suppliers.
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How Expensive Is Heating In Greenhouses
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