- Energy Saving
Thermal screens - essential for an energy efficient greenhouse?
It is now well proven that retractable thermal screens can save energy without having a detrimental effect on plant growth or quality; and you might even argue that a screen is now also an essential tool for both energy saving and
greenhouse environment optimisation.
HDC projects, such as PC 197 at Mill Nurseries and PC 227 at Valley Grown Nurseries, have shown the huge advantages of having a screen. So why in this time of high energy prices are some growers still overlooking the technology?
Obviously, if you are growing a low energy crop, or if your greenhouse does not lend itself to having a screen installed, the payback on an installation may make it uneconomic. However, because of the recent dramatic increases in energy prices, paybacks on most installations are now between 18 months and three years.
For example, if you are growing a crop throughout the winter months at greenhouse temperatures of 18 degrees C or more, you can expect to get savings of at least 90 kilowatt-hours per square meter (kWh/m2). Based on current energy prices, this translates to a saving in heating costs of around £30,000/hectare (Ha).
Obviously installation costs depend on the complexity of the site, but they are typically in the range of £50,000 to £90,000/Ha. This means that even with an old greenhouse with a difficult installation procedure the payback should still be no more than three years.
With this level of payback, installing a thermal screen is still more attractive than facing the difficult task of managing the installation and operation of a greenhouse with a temporary polythene screen.