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NIRE Annual Report
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1996

Development of Gaia Snow-Melting System

Geo-Energy Division
Mining and Geotechnology Department
Objectives
The objectives of the present research are to carry out the studies on the Downhole Coaxial Heat Exchanger (DCHE) system for establishing the new heat extraction technology for the exploitation of the potential geothermal resources including shallow and low-grade formation, Hot Wet Rock, fluid systems of magmatic origin and magma.
The Gaia Snow-Melting System
The new system, named the Gaia Snow-Melting System, was developed through this research jointly with Mitsui Engineering & Shipbuilding Co., Ltd. and four other private enterprises including Akishima Laboratories (Mitsui Zosen) Inc., Kubota Ltd., Koken Boring Machine Co., Ltd. and Daikin Industries, Ltd.. This system utilizes low temperature ground which is universally distributed as its main heat source, and the solar heat stored in the ground over the summer is used as an auxiliary. The system consists of a heat pump, the highly efficient DCHE, and heating tubes embedded in the road, as shown in Figure.1. In summer, the solar heat absorbed in roadbed is recovered by circulating antifreeze inside heating tubes embedded in the road. The antifreeze heated in this manner is then circulated inside the DCHE and the ground is heated for heat storage. In winter, the geothermal energy and the solar heat stored over the summer are extracted from the ground by circulating antifreeze in the DCHE and are transferred to a heat pump. After the temperature is increased up to a sufficient level for snow melting with the heat pump, the thermal energy is then transferred to the antifreeze circulating inside heating tubes. This system is applicable virtually anywhere, regardless of ground temperature and existence of ground water. Another benefit is the absence of pollution such as ground subsidence or combustion products emission. Hence, the Gaia Snow- Melting System is one of the most appropriate one for the global environment among the various kinds of snow melting system.
Results
The Gaia Snow-Melting System has been introduced in Ninohe city, Iwate Prefecture, and has been in operation since December 1995. Through the experimental operation in this winter, it was demonstrated that the electric power consumption and the operation cost of this system were only one-seventh and one-fourth those of conventional electric heater system, respectively. Thus, it was demonstrated that the present system can contribute greatly in energy and environmental issues.


Selected Publications
1) Development of the Downhole Coaxial Heat Exchanger System : Potential for Fully Utilizing Geothermal Resources, GRC Bulletin 24(3), 83-92(1995)
2) Measurement of the In Situ Thermal Conductivity of Formations in a Geothermal Field Method and results of measurement, Proc. of the WGC 1995, Vol..2, pp771-776(1995)

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