| Abstract |
A number of commercial crops can be raised in greenhouses, making geothermal resources in cold climates particularly attractive; however, growth can even be optimized in warmer climates. These include vegetables, flowers (potted and cut), house plants, and tree seedlings. As an example, the optimum growth temperature of cucumbers, tomatoes, and lettuce is shown in Fig. 1 below (Barbier and Fanelli, 1977). Cucumbers grow best in the temperature range 25o- 30oC, tomatoes near 20oC, and lettuce at 15oC and below. The growing time for cucumbers is usually 90 to 100 days; while, the growing cycle for tomatoes is longer, in the range 9 to 12 months. The use of geothermal energy for heating can reduce operating costs (which can amount for up to 35 percent of the product cost) and allows operation in colder climates where commercial greenhouses would not normally be economical. In addition, greenhouses are suited to large quantities of relatively low-grade heat. Furthermore, better humidity control can be derived to prevent condensation (mildew), botritis, and other problems related to disease control. (Schmitt, 1981). |