Many measures can reduce electricity needs for lighting, it found. The greatest effect is obtained by diffuse glass with anti-reflection coatings. This causes better use of sunlight. According to calculations, almost 15 per cent less lamp light is needed for the same winter production, while this glass type also gives a few per cent more stem weight in the summer period.
The latest LED lamps can give 50 per cent more PAR light per kWh electricity than high-pressure sodium (HPS) lamps. If, for example, half of the HPS lamps are replaced, the electricity bill will be sharply reduced. With a total of 22 measures the heat demand can be reduced even more than 50 per cent. Some of these measures are at the expense of winter production or require such high investment that cost-effectiveness is questionable.
Many steps can also be made in heat savings, the surveys found. The company Arcadia has already shown that dosing outside air in combination with an extra energy screen can save more than 8cu m per square metre of natural gas equivalents a year. Humidity and heat pipe settings should also be adjusted. Other measures include the use of drip irrigation instead of sprinkling so that the crop does not have to be dried with extra heat.
Cooling and dehumidification with air-handling units assure better summer quality and harvested heat can be used to heat the greenhouse with aquifers and a heat pump in winter. At a high gas price and low electricity price, this is a cost-effective option that brings the "chrysanthemum greenhouse without gas" within range. But an alternative is needed to steam for disinfecting the soil.