1. Field of the Invention
The present invention relates generally to hybrid renewable energy systems using solar heat, solar light, geothermal heat, wind power and atmospheric pressure and, more particularly, to a hybrid renewable energy system having an underground heat storage apparatus which stores high-temperature heat energy, obtained from solar energy, in an underground heat storage so that the stored energy can be used as a stable energy source, and in which descending high-density low-temperature air that is adjacent to the ground because of gravitational force is drawn into a heat exchanger of the underground heat storage apparatus and is heated by the heat exchanger to produce vertically-ascending wind power, thus generating a large amount of electricity using the wind power.
2. Description of the Related Art
Generally, various kinds of renewable energies that are currently in use have disadvantages so that they cannot be continuously and stably used depending on their application field.
Use of solar heat and light are restricted by weather conditions and the time. For instant, they cannot be used when it is cloudy, raining or snowing or at night.
Wind power also is subject to the constraints of time and place, because the intensity of wind varies according to the time or place. Digging into the ground to a depth of several hundreds of meters in only a particular area is required to obtain geothermal heat. Thus, economic feasibility is limited, and there is the locales are restricted.
Efficiency of the energy utilization of solar heat (80% or more) is four times or more that of solar light (lower than 20%). However, the fact is that the coefficient of utilization of solar heat is lower than that of solar light. The reason for this is that technologies or products that use solar heat have low technological and economic competitiveness.
Presently, in well-known technology using solar heat, a solar heat collection plate heats water which is a heat medium, and the heat water is stored in a heat storage tank and is secondarily heated by a boiler to produce hot water or water for heating a room that is of a desired temperature. This is old solar technology which was proposed about 40 years ago and is still being used to date without any developments having been made in innovative technology.
Furthermore, the conventional solar heat collection plate comprises a planar heat collection plate. There are two kinds of heat transfer methods used in a planar heat collection plate, including direct heat transfer due to solar heat and indirect heat transfer owing to air. The heating temperature and efficiency of the conventional planar heat collection plate cannot help being basically low.
A copper plate of the planar heat collection plate absorbs solar radiant heat of 300° C. or more but the temperature to which water is heated is actually 45° C. or less. In other words, the efficiency of the planar heat collection plate is very low. The reason for this is that the structure of the planar heat collection plate has low heat transfer efficiency because the area of the direct heat conduction surface that is the most critical portion is very small on the scale of 1/45 of that of a heat absorption surface of the copperplate.
In addition, products, such as a dish concentrator, a parabolic concentrator, etc., were proposed, but these products have been mainly used for testing or research purposes in laboratories, universities, etc. or for low power generation. Moreover, because these products are very expensive and are economically infeasible, they cannot be used in building structures, such as general dwellings or the like. This is the reality of renewable solar energy technology.
The above-mentioned techniques imply background techniques in the art pertaining to the present invention rather than denoting the conventional techniques.