By the year 2020 the glasshouse industry could be a supplier of energy rather than a consumer. Future blocks of glasshouses could be constructed within housing developments to supply heat to residential properties or above sports centres and supermarkets. In Holland 10% of the natural gas produced is consumed by the glashouse industry which in turn creates 4.5% of all CO2 emissions. Future systems must be developed to generate excess energy. Today, energy costs in Holland account for about 50% of total floricultural production costs while this was about 30% in the 1990's. The first development is likely to be the construction of 'closed greenhouses systems'. They will be fitted with solar panels to generate electricty and heat exchangers to 'store' surpluss heat in the summer. By closing greenhouses completely, better product yields and quality can be obtained with a much reduced requirement for water and chemicals to control pests and diseases. Growing conditions for tomatoes in a closed system under trial provided an energy saving of 30%, RH of 75-85%, CO2 level of 1,000ppm and a 50% saving on irrigation water. At the same time productivity rose by 22%. But the closed greenhouse also needs systems for dehumidification and cooling. The use of plastic glazing panels such as Lexan ZigZag, energy reduction of up to 40% can be achieved. Innogrow's 'ClosedGreenhouse' won the 2003 Reed Horti Fair Award at Horti Fair.

Another likely development will be to build glasshouses above reservoirs to facilitate the collection of rainwater and the recycling of irrigation water and nutrients. This is especially appealing where land is expensive and in short supply. Such reservoirs are already under trial in Holland and an ambitious project to build a 50,000mq reservoir under a 2ha site with a water depth of 2.5m is planned.

Another futuristic idea is to build floating glasshouses. A project by Dura Vermeer and I & F Innovations is at the planning stage. Glasshouse technology will improve plant photosynthesis using refex coatings and photoselective materials. Artificial lighting will become more powerful (individual lights will increase to 16,000 and 24,000 lux as opposed to the more common 8,000lux of today. Currently 80% of rose production in Holland is under artificial lighting and 50% of the chrysanthemums. The burning of fossil fuels to provide energy will be hugely reduced. These and other ideas under trial in Holland were presented at theInternational Conferenze on Greenhouse Technologies and The Market - Horticulture and Floricultureat the RAI Centre in parallel with the NTV (Hortifair), Amsterdam, 2003. Steven Vale, "Commercial Greenhouse Grower" Organized by Europoint. Contact Ingrid Looijmans Fax 0031 20 6445059 E-mail i.looijmans@rai.nl www.europoint-bv.com/events/greenhouse2003