Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
Greenhouse production systems produce in the Netherlands
and Flanders economical important quantities of vegetables,
fruit and ornamentals. Control of the crop environment has led
to a high primary energy use (1500MJ/m²/year). This high
primary energy use affects the economical and environmental
sustainability. Research projects in the Netherlands and
Flanders are launched to achieve sustainable greenhouse
systems with high crop yields and low primary energy use.
Until now, these projects didn’t result in the desired primary
energy savings. On the contrary, the civil building industry
succeeds by the passive house technology in a magnitude’s
reduction for primary energy use.
The primary energy saving research in greenhouse systems
was mainly based on analysis of energy balances. However, the
thermodynamic theory indicates that an analysis based on the
concept of exergy (free energy) and energy is preferred. Such
analysis could reveal possibilities for primary energy savings.
The different processes and in/outputs of the greenhouse
system are outlined. The appropriate equations for exergy
calculations are developed. First, analyses are performed on the
processes of transpiration and ventilation. Further, a total
system assessment is performed.
The exergy analysis indicates that primary energy saving in
greenhouse systems could be the same as in the building
industry, but adapted technologies need to be developed.
The Institute for Agricultural and Fisheries Research
(ILVO) will use this exergy analysis as a basis for the
development of an exergy efficient greenhouse prototype
(EXEkas).
