Glasshouse ornamental growers were offered some tips for reducing energy use for the winter ahead at a seminar held at Bordon Hill Nurseries in Warwickshire last month.
Tim Pratt and Jonathan Swain, energy specialists at the Horticultural Development Company-funded consultancy GrowSave, offered a range of suggestions:
- "Air leakage is the big killer - check whether any panes have slipped," Pratt urged. Insulate not only pipes but also valves and pumps. "It will pay for itself in a year. Start at the boiler and work forward, and make sure it's not getting wet."
- Position measuring boxes with care. "They are the single biggest thing influencing how much fuel you use," said Pratt. "They tend to be located for convenience, but they shouldn't be too far from the crop. It's worth getting an electronic humidity sensor for about £50 rather than the wet/dry bulb model."
- Consider replacing high-pressure sodium light bulbs. "Their efficiency drops over time, even if you clean them," said Pratt.
"You should reckon on changing them every five years. There are probably a lot out there that are older than that. And check you are getting the light levels that you are supposed to get."
- Light reflectors also require regular cleaning and can be re-anodised at £30 a fitting, which growers should also expect to do every five years, Pratt added.
- For lighting other areas, Swain advised replacing T12-type fluorescent tubes with the narrower T5 type. "They give a 25 per cent energy saving and last longer," he said.
- Thermal screens may also require replacing, especially if they have become "gappy", said Pratt. "There was a rush into thermal screens in 2005-07 and materials have moved on since then."
- Buy fans with caution, checking the energy-efficiency ratio first, Pratt suggested, pointing out: "A cheap fan can be very expensive." He added: "Air movement is a black art. If you lack temperature uniformity, it's better to get to the root cause rather than use fans as a sticking plaster."
LED trials: Potential for seedling production
Bordon Hill Nurseries general manager Peter Byrne said: "We have been trialling LEDs for seedling production and could have something operating commercially within two years, not necessarily in a glasshouse at all."
GrowWise expert Tim Pratt added: "The capital cost of LEDs is still very high - around four times that of high-pressure sodium lights. You need a crop benefit to justify that. But there is no fall-off in efficiency. Your glasshouse will fall down first."