A 1350 MWe saturated steam Turbine-Generator power plant utilizing the naturally occurring heat generated from the Earth can be built with existing hardware. It will consist of a tunnel to access the Earth’s heat and a standard power plant on the surface to produce electricity. This type of facility would replace two large coal fired electric plants or one large nuclear plant, produce no pollution, can be constructed in any country on the planet, and is less expensive to build and operate than current electrical production facilities. This type of plant along with an all electric economy will eliminate human induced climate change, air pollution and future disposal of radioactive and coal fly-ash waste.
The Earth’s core generates heat due to radioactive decay and residual heat from planet formation. The temperature of the core is approximately 8000 F and as heat conducts towards space it forms a temperature gradient. The air temperature of the Earth’s surface is influenced primarily by the temperature of the atmosphere. However, the temperature of the crust increases at a rate of approximately 25 - 30 C per Kilometer of depth. This provides an opportunity to harvest this energy for non-climate changing electrical production.
The use of a Tunnel Boring Machine (TBM) will be used to create a 7 meter (~23 Ft.) diameter tunnel, angled at 30 degrees, to a depth of 16 Km (9.9 miles). At this depth, the heat from the earth will be approximately 400 C to 480 C (752F to 896F). Total tunnel length will be 27.7 Km (17.1 Miles). Existing technology and experience is available to construct this tunnel. Construction and operation below two (2) Km will be performed tele-robotically and through the use of spacesuit like protection. The use of a tunnel with a 30 degree incline allows the tunnel wall and steel liner to support the weight of all the equipment and also permits human and machine travel along the tunnel’s length.
Electrical sales of this size electrical plant is approximately 250 million USD. Construction costs is estimated to be one billion USD for the tunnel and two billion USD for the power plant. As the facility consumes no fuel for operation, and require an operations staff of five personnel, cost break even will take 12 years at full power operation. The plant is designed to operate for 100 or more years. In addition, the tunnel is large enough to accommodate a second set of feedwater and steam lines to allow a second 1350 MWe plant to be constructed on site. Based on hard rock tunneling and power plant construction experience, construction of the plant will take approximately five years.
Figure 1 shows the general layout of the electric plant and tunnel system. The use of steam pressure to raise the working fluid to the surface and the use of gravity to raise feedwater pressure eliminates the need for piping and pumps normally seen in similar size power plants.
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