American and Israeli engineers at Trio Energy Systems have developed a system for commercial greenhouse heating and dehumidification that can save up to two-thirds of the energy used by conventional means.
Most heat loss from a greenhouse occurs via conduction through the greenhouse cover, especially in cold climates. In the Trio System, a thermal screen divides the greenhouse into two areas – the growing area and the upper chamber.
Trio heat pumps continuously recycle heat energy that escapes into the upper chamber back down to the growing area. The system is electronically controlled for maximum efficiency.
At the same time, the Trio System removes water vapour from the greenhouse, keeping the humidity at a healthy level for crops.
In moderate climates (night time temperatures down to 5°C), the Trio System can maintain a temperature inside the greenhouse growing area that is 6-9°C higher than the outside temperature - without a conventional boiler or furnace operating at all.
In addition, it keeps relative humidity in the growing area at 70-80 per cent - without venting air from the outside. In colder climates, or where the required temperature difference is greater, the Trio System works in tandem with a conventional boiler or furnace, but still reduces fuel consumption because of the recycling effect of the heat pumps.
Depending on heating hours per year, greenhouse insulation and the cost of alternative fuel, the Trio System can save as much as $15 (€12/£8) or more in heating and dehumidification costs per year per square metre.