What is geothermal energy that Li Siguang misses? Read an article

What is geothermal resource?

Geothermal energy refers to the renewable heat energy stored in the earth, which is generally concentrated at the edge of tectonic plates and comes from the decay of molten magma and radioactive materials on the earth.

Because geothermal energy is stored underground, it will not be affected by any weather conditions, and geothermal resources have all the characteristics of other renewable energy sources, and can be used at any time without producing harmful substances.

There are many hypotheses about the source of geothermal energy. It is generally believed that geothermal energy mainly comes from the external and internal heat sources of the earth. External heat sources include solar radiation. The internal heat sources include radioactive element heating and core heating. According to the calculation, the temperature of the core is about 6000°C, and the temperature of the lower crust is 900 ~1000 C. In the range of about 15 km below the thermosphere of the earth's surface (about 15 m above the ground), the ground temperature increases with the depth, and the average heating rate is about 3 C//kl. The area close to the average heating rate is called geothermal normal area, and the area above the average heating rate is called geothermal abnormal area. Geothermal anomaly area is the main object of geothermal resources research and development. The crustal plate edge, deep faults and volcanic distribution zones are obvious geothermal anomaly areas.

02

The difference between geothermal energy and other resources

Geothermal energy spreads heat to the earth's surface in various ways, reaches the upper crust that people can collect, and forms geothermal resources that people can develop and utilize. It is an inexhaustible source of heat energy that coexists with the earth, and geothermal energy is not limited by time and region, and it is everywhere at any time.

Geothermal resources are different from traditional mineral resources such as coal, oil and natural gas. Water, rocks and other substances that are buried underground and can absorb, conduct and contain geothermal energy can be called geothermal resources. People can get geothermal energy through them. Once they are out of the supply of underground geothermal energy, the heat contained in them will dissipate quickly. Just as wind energy is contained in wind speed and solar energy radiates through air, geothermal energy is transmitted to the ground through various media in the earth's crust. Only with the help of some media can people effectively collect and use it can it be called a resource.

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How to exploit geothermal resources?

The exploration depth can be determined according to the main thermal storage types, burial depth, technical and economic conditions of current mining and market demand. For naturally exposed banded thermal reservoirs, the exploration depth is generally controlled within 1000 m; The exploration depth of buried basin layered thermal reservoirs is generally less than 4000m m.

Geothermal exploration should implement the principle of "combination of exploration and mining". Geothermal geological exploration drilling can be used as a well, which should be implemented according to the technical requirements of well completion; Drilling geological logging, logging, completion test and geological data collection and arrangement of geothermal exploitation wells should be carried out in accordance with the technical requirements of well completion, and various geothermal geological data should be accurately obtained according to the requirements of geological exploration.

1. The deeper the well is drilled, the higher the cost.

2. Complexity of geological structure in geological factor drilling The more complex the geological structure is, the more the diameter is changed, and the higher the cost.

3. The geographical location of drilling determines the transportation mode and power source of drilling equipment, which further affects the drilling cost.

4. Drilling footage, power and aperture Generally speaking, the deeper the footage, the greater the power required and the higher the cost.

04

Why geothermal resources are not the main source of new energy?

Theoretically speaking, the reserves of dry-hot rocks are very rich, but the existing exploration technology can't drill deep underground, so it can only mine dry-hot rocks with shallow burial and simple terrain.

Moreover, before mining dry-hot rocks, workers need to determine the direction of cracks in these rocks in advance in order to extract heat more effectively.

If large-scale mining is to be carried out, it is necessary to have a clear and comprehensive understanding of the distribution of the whole dry-hot rock resources and rock fractures, with the aim of reducing the cost of energy exploitation and improving the utilization value of energy.

China Geothermal Energy Development Report (20 18) jointly issued by China Geological Survey of the Ministry of Natural Resources and the Department of New Energy and Renewable Energy of the National Energy Administration (hereinafter referred to as the report) points out that the annual recoverable resources of shallow geothermal energy in 336 major cities in Chinese mainland are equivalent to 700 million tons of standard coal, and the heating (cooling) building area can reach 32 billion square meters, among which the Huanghuaihai Plain and the middle and lower reaches of the Yangtze River are the most suitable for the development and utilization of shallow geothermal energy.

The geothermal energy industry was once highly anticipated. As the first special plan for the development and utilization of geothermal energy in China, the 13th Five-Year Plan for the Development and Utilization of Geothermal Energy (hereinafter referred to as the 13th Five-Year Plan) released on 20 17 predicts that geothermal heating will boost investment by about 220 billion yuan and geothermal power generation will boost investment by about 40 billion yuan, totaling about 260 billion yuan.

Why is the development of geothermal energy with a market scale of 260 billion so slow?

"Develop and utilize geothermal energy according to local conditions." The national "14th Five-Year Plan" published recently made the above statement on the keynote of geothermal energy development.

Geothermal energy is a kind of green, low-carbon, recyclable and renewable energy, which has the characteristics of large reserves, wide distribution, cleanliness, environmental protection, stability and reliability. At present, China's geothermal energy mainly includes geothermal power generation and geothermal direct utilization (heating), which is highly consistent with the goal of clean heating and "double carbon".

The geothermal energy industry was once highly anticipated. As the first special plan for the development and utilization of geothermal energy in China, the 13th Five-Year Plan for the Development and Utilization of Geothermal Energy (hereinafter referred to as the 13th Five-Year Plan) released on 20 17 predicts that geothermal heating will boost investment by about 220 billion yuan and geothermal power generation will boost investment by about 40 billion yuan, totaling about 260 billion yuan.

However, the reality is very skinny.

Zheng Kekun, director of the Expert Committee of Geothermal Professional Committee of China Energy Research Association and director of the Expert Committee of China Ground Source Heat Pump Industry Alliance, once wrote that during the "Thirteenth Five-Year Plan" period, the newly installed capacity of geothermal power generation in China was 18.08 MW, accounting for 3.6% of the "Thirteenth Five-Year Plan"; The total installed capacity of geothermal power generation in operation in China is 44.56 MW, accounting for about 8% of the planned installed capacity.

Zheng Kekun believes that geothermal power generation has not completed the planning task, mainly because geothermal power generation has not enjoyed the subsidy of the Administrative Measures for Additional Distribution of Renewable Energy Electricity Price.

Take Xiyangyi Thermal Power Station in Tibet as an example. The power station will be connected to the grid in 20 18 years and 20 19 years. At present, the on-grid electricity price is 0.25 yuan/kWh, and there is no subsidy, so the power plant is difficult to operate.

Wind energy and solar energy, which are also renewable energy sources, have enjoyed relevant subsidies in recent years and achieved leapfrog development.

In addition, according to the resource tax law that came into effect on September 1 2020, geothermal energy is included in the category of energy minerals, and the tax rate is 1%-20% ad valorem or 1-30 yuan per cubic meter. This further curbed the competitiveness of geothermal energy in renewable energy, and also inhibited the enthusiasm of large-scale capital entry.

In the field of direct utilization of geothermal energy, China ranks first in the world for many years, but there is still a gap compared with the 13 th Five-Year Plan.

In addition, the initial investment and installation cost of geothermal energy is higher than that of coal and natural gas. According to the above data of China Petrochemical Company, it is assumed that the initial investment of coal-fired boiler room is 1 and the initial investment of underground water source heat pump system is about1.25-2.8; The initial installation cost of ground source heat pump is nearly ten thousand yuan.

This has become one of the important factors restricting the application of geothermal energy heating (cooling).

(The above knowledge is compiled from the Internet, and the copyright belongs to the original author. )