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Mining the Earth's Heat to Generate Geothermal Power

In your country, are there hot springs? Japan has hot springs scattered nationwide. Hot water drawn up from underground is used to make hot spring baths. Do you know who heats the water? The answer is the Earth. The water in a hot spring is heated by geothermal heat, which is the heat from deep down inside the earth.

The temperature increases as you dig deeper inside the earth. At 50 kilometers below the earth's surface, the temperature goes up to 1,000 degrees Celsius. Hot springs are places where milder geothermal heat is obtained from reservoirs (areas for storing a large amount of water) a little closer than 50 kilometers to the surface. Japan is blessed with abundant geothermal heat nearby.

The world's first geothermal electricity was generated in Italy about 90 years ago. To generate geothermal power, hot water is pumped from underground, and the hot steam that is brought up is used to drive a turbine. Then, the water is sent back down to the reservoir to continue the cycle. Sending water from the surface of the earth down to the hot reservoir is also a useful way to produce hot steam. Magma (melted rock found beneath the earth's surface) is also being studied as a source of electric power.

The good things about geothermal power generation include the following.
1. It's right there in your country. There is no need to import from other countries.
2. The power can be generated forever in geothermal power generation, unless the earth somehow cools down.
3. The amount of carbon dioxide (CO2) that comes out of geothermal power plants is minimal. It is only one twentieth of the CO2 that comes from thermal power generation.
4. Stable power can be generated throughout the day and night, all year round, in good and bad weather.

However, there are weak points too.
1. The sites where geothermal plants can be built are limited.
2. The maximum amount of geothermal power that can be generated in one location is not great and is limited.
3. It costs a lot of money to build a geothermal power plant.
4. About half of the possible sites for generating geothermal power are in protected national parks, and these sites cannot be used for it.

In Japan, there are about 20 geothermal power plants, mostly in the Tohoku region, northeastern Japan, and in Kyushu, the southern part of Japan. There is a geothermal power plant in Hachijyo Island, off shore of Tokyo, which runs for 24 hours a day. Thanks to the operation of this power plant, Hachijyo has decreased by 40 percent the amount of CO2 that comes out of the power plant.

About 20 countries are using geothermal power generation in the world. Twenty percent of the total power produced in the Philippines is geothermal and the government plans to increase the number even more. In Nicaragua and El Salvador, geothermal energy is 15 percent of the total power, while it is 7 percent in New Zealand, and 5 percent in Costa Rica and Iceland.

The total geothermal energy that comes through the earth's surface in a year is four times greater than the total energy humans use in a year. Only 0.2 percent of the total electric power in Japan is generated by geothermal power, but it has huge potential because there are about 200 geothermal sites nationwide.

Geothermal heat can be used as thermal power as is, and it doesn't have to be generated and changed to electricity to make it useful. In Iceland, household heating must use geothermal heat, and electricity cannot be used. In hot spring tourist towns in Japan, they still use electricity or oil to heat the dressing rooms for the tourists, but it would be better if they could more efficiently use the "heat" available at the hot springs.

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