Climate control & energy > Efficiency
High input and output
Typically, greenhouses have a very high input and a very high output of high-quality high-value products. For example, the output of a tomato cultivation in a modern well-controlled greenhouse can 10-20 times higher than of any outdoor crop (expressed in tonnes per hectare per annum). The high output is achieved by a high input of capital, labour, fertilizers and energy. This is all necessary in order to capitalize on the high investments. Thoughtless reduction of input would reduce the output to the point of crop failure and risking the business.
Energy input
One of the major inputs in a greenhouse is energy for maintaining optimal growing condition (temperature, humidity, CO2). In addition, electricity is needed for pumps, motors, machinery, etc. Like other industries, the greenhouse industry must reduce its energy input and carbon emission. The question is how can energy input be reduced without sacrificing the profitability of a greenhouse operation?
Energy efficiency
What is needed is an increase of the energy efficiency. This is the ratio between production (output) and fuel (input), or the ratio between energy usage (MJ) and yield (kg). A higher energy efficiency means more units products (kg) per unit energy (MegaJoules). Energy efficiency can be increased by growing more product for the same amount of energy input, either by increasing the output, or reducing the input, or both.
Benchmarking
Energy efficiency data enable comparison and benchmarking. They can be very helpful for internal comparison between years, or external compearion between colleagues, or for instance for assessing the effect of energy-saving measures or new growing practices. Energy efficiency can also be a tool in government policies. For instance the Dutch greenhouse industry aimed to achieve 65% improvement in energy efficiency by 2010 compared to 1980.
Further reading
Energy saving measures – options listed (2003)
Reducing greenhouse heating costs by low-cost energy saving actions (2003)
Calculating energy efficiency and carbon tax for greenhouses (2003)
Potential energy saving measures categorised (2006)
Energy study completed, opportunities assessed (2007)
