Objective
The project aims to demonstrate that a combination of passive solar energy collection and storage techniques, with microcomputer controllers, can offer an effective cost solution for winter heating and summer cooling of a greenhouse and also have quite attractive prospects concerning low maintenance cost, durability and simplicity of operation.
The greenhouse cover, a forrugated fiberglass type material, is destroyed (from 75% to 50% solar transmission) in one year, and reduces the plant growing.
The construction of the chemical heat storage is cancelled, due to its very limited market potential.
The solar system is used for space heating of a greenhouse with plastic cover.
The total area of the greenhouse is 1000 m2 (20x50m) and the main axis is East-West oriented.
The structure is of galvanized steel with side openings and has a transparent fiberglass cover. A ventilation system is also installed.
The greenhouse energy system is composed of 3 elements : the north side thermal storage wall (150 m2) which is a solar collector and thermal sotrage, the soil storage system (L=45m,D= 160mm) and a 100 kg chemical storage. The north side is composed of a thermal wall 35 cm thick built with concrete-filled cement blocks. Complementary to the storage wall an underground storage system is installed.
Lengthwise, at a depth of 1.5 m, PVC tubes are burried. They are equiped at the extremities with fans to establish the air circulation.
The system operates basically in two modes :
In the summer period a shading system shades the storage wall from the solar radiation. The openings in the north wall permit the air to flow through the greenhouse and getting out through the south windows, thus obtaining a natural ventilation.
On the other hand the inside temperature is much higher than that in the subsoil.
For this reason a circulation through the burried tubes is made, leading to the greenhouse cooling and the subsoil heating (to be partially recovered in the fall and winter season). During night time the cold outside air enters the greenhouse and the cold is stored in the wall. This reduces the operating start temperature and therefore the overheating temperature.
During wintertime, the space is preheated with the heat stored in the soil, while the main heating is provided by the thermal storage wall in addition to the thermochemical energy gain storage. During the day, solar radiation raises the storage wall temperature. The energy is transferred to the space by radiation and convection.
The expected energy savings amount to 280 GJ/year, reducing the auxiliary heating to 83 GJ/year. The repartition of the energy savins are 184 GJ by the north storage wall, 37 GJ by the ground storage and 21 GJ/year by the chemical storage.
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
10680 Athens
Greece