华中科技

According to a study, the traditional energy sources such as coal, oil and natural gas which are widely used today will face severe shortage in about 50 years. The severe energy crisis forces human beings to turn their eyes to the vast universe, and the moon is the first choice of human looking for energy beyond the earth.

Solving the energy crisis is full of difficulties

At present, scientists are trying to find ways to solve the energy crisis, and the moon with its unique environmental characteristics and huge energy storage has naturally become the first choice for human search of extraterrestrial energy.

Originally, scientists had pinned their hopes on solar power and nuclear reactors (both nuclear fission power generation and fusion power generation). However, the dense Earth atmosphere makes the use of solar energy on Earth less stable; The methods of obtaining electricity by nuclear fission reaction often produce large amounts of radioactive waste, which is easy to cause serious environmental pollution. Deuterium and tritium thermonuclear fusion reactors, which are being rapidly developed to produce energy, are also radioactive because of the powerful neutron radiation they produce.

Building solar power plants on the moon

Since there is almost no atmosphere on the moon's surface, solar radiation can penetrate. Calculations show that the amount of solar radiation reaching the moon each year is about 12 trillion kilowatts, equivalent to 25,000 times the total energy generated by all the energy currently consumed on Earth in a year. Based on a solar energy density of 1.353 kw/m2, assuming that the current solar power generation device on the moon has a 20% photoelectric conversion rate, the solar cells per square meter could generate 2.7 kwh per hour. If using 1,000 square meters of the cells, it could generate 2,700 kwh per hour.

Since the moon's rotation period coincides with the time that it takes to orbit the Earth, the moon has 14 and a half days of day and 14 and a half days of night. A day is the length of the Earth's month, so it can get more solar energy. Scientists think, if establishing a global parallel solar power plant on the surface of the moon, it can get very rich and stable solar energy, which not only can solve the problem of future lunar base of energy supply, and also can provide a steady stream of energy for the earth by microwave transmission of solar energy, with the development and improvement of human space conversion device and ground receiving technology.

The lunar soil is rich in He-3

A realistic way to solve the energy problem of the future is to build and use thermonuclear reactors with isotope He-3 (3He), which have no neutron radiation and pose no environmental hazard. However, it is a pity that the reserves of He-3 on the earth are very limited. The total theoretical content of natural gas in the earth is only 10-15 tons, while the lunar soil is rich in He-3.

Except for a few very steep impact craters and volcanic channel cliffs that may have exposed rock, the entire lunar surface is covered with lunar soil, which is on average about 5 meters thick in the lunar seas and about 10 meters thick in the lunar lands. These soils have been exposed to the sun for a long time and are enriched in volatile chemical elements and isotopes injected directly by solar wind particles. There are large amounts of He-3 in these rare gases. It is estimated that the total amount of He-3 resources in the lunar soil could reach 1 million to 5 million tons. He-3 is a clean, safe and efficient fuel for fusion power generation. According to experts' calculations, if using D-3He (deuterium and He-3 for nuclear fusion reaction to produce electricity) for nuclear fusion power generation, the total annual power generation in the United States only consumes 25 tons of He-3; China's total annual power generation in 1992 was only 8 tons of He-3, and 100 tons of 3He a year is enough for the whole world. Based on the current global electricity price and the cost of space transportation, 1 ton of He-3 is worth about $4 billion, and with the development of space technology, the cost of space transportation is sure to decrease greatly. Recently, French scientists announced that fusion power generation using He-3 will be commercialized by 2030. Therefore, the development and utilization of He-3 in lunar soil will be one of the most promising ways to solve the energy crisis of human beings.

(Zou Yongliao, Liu Jianzhong, National Astronomical Observatories, Chinese Academy of Sciences, Global Times)