ENERGY SAVING IN PROTECTED CULTIVATION: A SHORT INTRODUCTION

ISHS Acta Horticulturae 312: European Seminar New Technologies for the Rational Use of Energy in Greenhouse Horticulture in Northern Europe

ENERGY SAVING IN PROTECTED CULTIVATION: A SHORT INTRODUCTION

Abstract:
Although today energy saving in protected cultivation is an important, and maybe even a fashionable issue, there exists a divergence in the appreciation of the problem. Because fossil energy represents a non renewable resource for now and for the future, and because its use is associated with a rise in the CO₂ concentration in the atmosphere and global warming, there is a general feeling that its use should be reduced. For others the emphasis will be rather on the yield per amount of fossil energy consumed. For the grower energy saving will be no objective on itself. He will consider the consumption of fossil energy and investments in energy saving measures within the framework of the overall management of the nursery, where apart from the economic implications also other objectives are taken into consideration, such as quality of the product and the avoidance of risks. For application in practice, the evaluation of energy saving measures, irrespective of their theoretical contribution to the reduction of energy consumption, should be based on production per unit of energy consumed and economic feasibility. In this introduction a general view on the problem of energy saving in greenhouse cultivation will be presented, where the principle solutions are indicated and the coherence of various processes within the system is emphasised.

When considering the problem of reduction of consumption of fossil energy at the level of a nursery it is useful to distinguish 3 elements with distinct tasks (Figure):

Generation of heat, electricity and CO₂
The greenhouse responsible for the creation of the greenhouse climate
The crop with a double role: the "factory" where the product is formed, but also with a strong influence on the greenhouse climate

Graphic available in full text only

Figure - Essential elements, and their relations, in the problem of energy saving in greenhouse cultivation

This distinction, though useful for analysing the problem, has the disadvantage of neglecting the numerous interactions that exist and as a result partial problems may be solved while creating problems elsewhere. Moreover, in many cases the solution of one problem may exclude potential solutions of other problems. It is therefore essential to consider the overall problem, while solving sub-problems!