To pump the thermal energy from the dark world

Abstract

With a global average temperature around 300 K, the surface of the Earth emits a huge thermal energy in the form of long wave radiation, making it a warm thermal source in the cold universe. While living on the surface of the Earth, theoretically we are merged in the ocean of thermal radiation at the nominal rate of 100-300 Wm -2 at different seasons and in different regions. Here we present a proposal for pumping and utilizing this kind of thermal energy, even from the dark world at night or under the ground.Keywords: Thermal radiation; blackbody radiation; infrared electromagnetic wave; photovoltaic device. I. Endless solar energy sourceThe development of human civilization faces a tough problem that the most easily available "fossil energy", in the forms of petroleum oil, natural gas and coal, is going to exhaust in a one or a few hundred years. People in rich areas have been consuming more energy and natural resources than they should. For example, with its 4.5% of the world population (7.0 billion in 2014), the United States consumes around 20% of the total yearly energy cost by human being. China, with a 20% of the world population, is now taking more than 20% of the yearly energy the world consumed. These is no sign that people are going to change their 26 Shengyong Xu and Xiaohui Suways of living on the earth in the near future, in terms of enjoying the benefits of electricity and zillions of industry products, such as semiconductor devices, car, airplane, as well as city life. Clearly this mode is not sustainable in the time scale of one thousand year.The best and probably final solution for the energy crisis is to develop fusion technology that uses the almost infinite hydrogen element in seas and oceans.[1] The International Thermonuclear Experimental Reactor (IETR) project [2] in Europe has been going on for 7 years. It indeed aims at making a manmade sun on the surface of the earth, which faces incredible technical challenges and may cost a century or longer.Fortunately, the solar energy we received on the earth is also "endless". It is known that the surface temperature of the sun is around 6,000 K. By a rough estimation, considering the sun as a blackbody, its radiation spectrum follows the Plank formula. In Figure 1a, curve "A" plots this spectrum of the sunshine flux at the surface of outer atmosphere, and curve "B" is the sunlight flux measured at the surface of earth. The missing part is reflected, or scattered, or adsorbed on its way penetrating the atmosphere. The Solar Constant, 1.3 kW/m 2 , is the energy flux received at the surface of the earth atmosphere. As a result, 0.9 hour of this radiation energy at the earth surface is currently equal to the total energy consumed by human per year, i.e., 5.24 × 10 20 J. However, to date the solar energy only contributes around 2% in the total world energy recipe.[3] If in the next half a century, if this portion is increased to 50%, we may earn more time for the development of fusion technology. Figure 1Energy intensity spectra of electroma...