Introduction of Geo-Thermal Cooling System (GeTCo System)

2016-05-16

Smart Life Ecology Co., Ltd.

The distribution of temperature at a depth of 50 cm below the ground is shown in the figure below (United States Department of Agriculture). Soil temperature at the Earth’s surface is approximately proportional to the amount of radiant energy from the Sun that reaches the Earth; therefore, it is high around the equator and lower near the North and South Poles.

The actual surface temperature is affected by factors such as distance from the ocean, rainfall, and ocean currents. However, the figure suggests that underground temperature is determined largely by the relative angle of solar incidence (latitude).

The underground temperature in desert regions (orange) is lower than that in tropical rain forests (red) and is approximately 22 °C.

At depths of 3–5 m below the ground in desert regions, the temperature becomes 22 °C or lower, which is close to the approximate global average surface/underground temperature of 15 °C, and remains stable throughout the year at about 20 °C. In contrast, the Earth’s surface temperature in desert regions is extremely dry and becomes very hot during daylight hours, rising to 40–50 °C under direct sunlight.

The Geo-Thermal Cooling System (GeTCo System), proposed by Smart Life Ecology Co., Ltd., aims to promote energy savings by optimizing the energy diffusion path in terms of exergy.

Specifically, very long tubes filled with water—whose heat capacity is approximately ten times higher than that of sand—are placed both on the ground surface and underground. With the aid of a circulation pump, water is continuously circulated through the tubes between the surface and the underground, day and night, allowing the surface and underground temperatures to approach each other when averaged over a 24-hour period.

Existing evaporative cooling systems and ventilation fans are used only for peak load reduction, making it possible to significantly reduce the amount of cooling water required.

As the demand for fresh vegetables in desert regions is high, many agricultural greenhouses have introduced evaporative cooling systems (pad-and-fan systems). Since these systems consume five times more water for cooling than for plant irrigation, the depletion of precious underground water has become a major issue in desert regions.

The geo-thermal cooling system (GeTCo System) is shown in the figure above. By utilizing well water for the heat exchange process, the total consumption of cooling water can be reduced. The temperature near the plants can be lowered by placing sufficiently long tubes around them. Furthermore, the system is attractive to users because it can be built by individuals using materials that are easily obtained in the local market at reasonable prices.