Agriculture Reference
In-Depth Information
Heating with water at low temperature
is a particular case (e.g. used is association
with geothermal energy). It uses water at
temperatures of 40-50°C. It is a localized
heating system based on mobile or fixed
pipes combined with the use of radiant
sheets (radiant mulching) (Fig. 7.10). It is
used as a base heating, or associated with a
soil or substrate heating system, or as a sup-
port heating (Fig. 7.8).
The low-temperature heating system,
as implemented with plastic materials
in mild winter environments, is a cheap
investment, easy to install and manage
(Photo 7.5). It saves up to 30% of energy, in
relation to the traditional system (Urban,
1997a). Its main disadvantages are that its
response is slow, and that its power limited,
due to the lower water temperatures. Its
installation may require a large amount of
pipes, which may be an obstacle. In fact, in
order to maintain an air temperature of
20°C, it would be necessary to use four
times more pipes, if the water circulates at
40°C, than if the water circulates at 80°C, to
supply the same heat (Ellis, 1990). In cold
(a)
(b)
Heating pipe
Insulating plate
(polystyrene)
Fig. 7.10.
Common hot-water heating systems (low temperature) of (a) soil or substrate and (b) soil-air.
A soilless culture system is shown.
Photo 7.5.
Heat distribution pipes of a low-temperature heating system.
