Domestic and foreign geothermal power generation technology development status and trend

Global distribution of geothermal resources

Inside the Earth lies an unimaginable amount of energy. It is estimated that only within the outermost 10 kilometers of the Earth's crust, there are 125.4 billion coke heat, equivalent to the total heat of the world's current coal production 2000 times. If the total amount of geothermal energy is calculated, it is equivalent to 170 million times the total coal reserves. By some estimates, geothermal resources are 100 times greater than the potential for hydroelectric power. Even if the geothermal energy available is calculated at 1%, the heat energy that can be exploited within 3 kilometers underground is equivalent to the energy of 2.9 trillion tons of coal!

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Globally, the distribution of geothermal resources is uneven. The geothermal anomaly areas with obvious geothermal gradient greater than 30℃ per kilometer depth are mainly distributed in the regions of plate growth, rift-ocean spreading ridge, plate collision, declination-subduction zone. There are four major geotropics of global nature:

(1) Pacific Rim Geotropics: many famous geothermal fields in the world, such as Geisels, Long Valley and Roosevelt in the United States; Cerro, Prieto, Mexico; Wairakai, New Zealand; Taiwan manger in China; Japan's Matsukawa, Dayue and so on are in this area.

(2) Mediterranean-Himalayan geothermal zone: The world's first geothermal power station, Italy's Radero geothermal field, is located in this geothermal zone. China's Yangbajing geothermal field in Xizang Province and Tengchong geothermal field in Yunnan Province are also located in this geothermal zone.

(3) Mid-Atlantic Ridge Geotropics: Some geothermal fields in Iceland, such as Clafra, Namafiar and the Azores, are located in this geotropics.

(4) Red Sea - Gulf of Aden - East African Rift Valley geothermal field: including Djibouti, Ethiopia, Kenya and other countries.

3. Iceland is a country rich in geothermal resources. It is located near the Arctic Circle, and despite the cold climate, there is a huge amount of heat energy underground. Iceland accounts for almost a third of the world's rock flows, and in recent centuries, volcanic eruptions have occurred on average every five years, giving it a unique opportunity to generate geothermal energy. According to statistics, Iceland has more than 1,500 hot springs, hot springs, steam springs, geysers, etc.

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The United States is also rich in geothermal resources, according to geological surveys, the United States high temperature geothermal power generation potential equivalent to 755 to 729.7 billion tons of standard coal, or 60 to 475 billion barrels of oil; The medium and low temperature heat energy that can be directly used is equivalent to 1606 to 913.9 billion tons of standard coal. In addition, Japan, New Zealand, Italy, the former Soviet Union, India, the Philippines, France, Hungary, Mexico, Kenya and many other countries have geothermal resources.

China is also rich in geothermal resources. At present, more than 2,700 geothermal outcrops have been discovered (including natural and artificial outcrops), and there is a large amount of geothermal buried underground to be discovered.

Besides Tibet, Yunnan and Taiwan Province belong to high temperature geothermal areas. The coastal provinces such as Fujian and Guangdong belong to the medium and low temperature geotropics. There are low-temperature geothermal fields in some inland basins.

5. Distribution of conventional geothermal resources in China

Development of geothermal power generation technology

Geothermal power generation is a new power generation technology using underground hot water and steam as power source. The basic principle is similar to thermal power generation, and it is also based on the principle of energy conversion, first converting geothermal energy into mechanical energy, and then converting mechanical energy into electrical energy. Geothermal power generation is actually the conversion of underground thermal energy into mechanical energy, and then the mechanical energy into electrical energy, or geothermal power generation.

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After nearly a hundred years of development, geothermal power generation technology has a variety of types, including dry steam power generation, expansion steam power generation, double medium cycle power generation and Karina cycle power generation.

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1. Medium-low temperature geothermal energy

At present, the geothermal power generation projects are mainly developed by ordinary dry steam and flash steam. In the past 10 years, the dual-working medium medium and low temperature geothermal energy generation has developed rapidly. For specific geothermal resources, it is necessary to comprehensively consider the geothermal temperature, total geothermal reserves, geothermal water quality and other aspects, combined with power generation efficiency, operation and maintenance, equipment investment, environmental protection and other factors, and then determine the specific power generation technology route suitable for the geothermal resources.

Medium and low temperature (t<130℃) geothermal resources occupy a large proportion in the current proved geothermal resources, of which the temperature of about 90℃ geothermal resources account for about 90% of the total amount of such resources. For this type of geothermal resources, the dual-medium cycle power generation technology is more suitable. Dual Cycle power generation, also known as Organic Rankine Cycle (ORC), ORC power generation technology can use a wide variety of waste heat, coupled with the advantages in efficiency, process simplification, operation and maintenance costs, making this technology a development trend of low-grade heat recovery and utilization.