Cooled soil as a cooling source for buildings

Two approaches have been tested for cooling oil in a given location to temperatures well below the "normal" temperatures in that location. The first approach has been tested in Sde Boqer Campus, in the Israeli Negev desert. The soil was covered with a layer of pebbles, about 10. cm. thick, and watered in the mornings. The second approach was tested at A&M University in Tallahassee, Florida. Temperature measurements were taken of moist soil under a wooden shack on stilts, about 60 cm above the ground. Thus the soil under it was permanently shaded. In Sde Boqer the pebbles have blocked solar radiation during the daytime while evaporation from the soil, kept moist in the desert by irrigation, could continue day and night. This system of soil cooling was tested in two series. First it was applied in a small area of 2x2 m. Soil temperatures were measured in the treated soil and in the nearby un-treated soil in depths of 10. 30 and 60 cm. below the surface. The measurements lasted for about 6 weeks in the summer. In the second series an area of 5x5 m. was covered by the pebbles and soil temperatures were measured, in the treated and in the un-treated soil, in depths of 0.05, 1, 2 and 3 m. for a whole year. This system for cooling a building was tested by my former student, Dr. Nasser Al Hemiddi, in Riyadh (Al Hemiddi, 1995). A concrete roof of a room was covered by soil and then by a layer of pebbles, and the soil was watered. One day's indoor temperature of the cooled roof, and of a "control" room without cooling, is shown in figure 1. In Tallahassee the second approach to soil cooling was tested. At the A&M University Campus there was a wooden shack on stilts, about 60 cm above the ground. Thus the soil under it was permanently shaded. As the summer is the rainy season in Florida the soil was naturally moist. Temperatures were measured at depths of 5, 50 and 100 cm throughout the summer in the soil under the shack. The cooled soil temperatures were below the outdoors' minimum temperatures, even during the peak of the summer, providing a heat sink for cooling buildings.