In general, there are two main reasons for future energy research. First, as a result of global warming, atmospheric and environmental pollution due to energy consumption, present day energy patterns, using predominantly fossil fuels, must be either improved in their quality or more significantly, they must be substituted with more environmentally reliable clean and renewable energy sources. The second reason for future research is the appreciation that the fossil fuel reserves are limited and bound to be exhausted sooner or later. If the necessary precautions are not taken from now on by radical innovations in energy systems and their technologies, then future human generations on the earth will face an extremely precarious position. Additionally, population increase places extra pressure on the energy resources and the energy consumption per capita per day in developing countries is about 10 oil-equivalent-liter, which is below one-tenth of that in industrial countries (Chap. 1). In order to produce new energy sources independent of fossil
and nuclear fuels, the following points must be considered in future research programs:
1. The solar beam collector with a Fresnel lens or concave mirror
2. Electric charge separation by solar radiation
3. Other natural processes that reduce entropy, such as the functions of a membrane, catalyst, biological organ, other chemical phenomena, etc.
In the long run, full consideration must be given to the amount of energy that is required to produce more energy. One of the constant research areas is storage and the two most promising new devices are silica gel beds and two-vessel storage (Ohta 1979). Silica gel beds try to improve the efficiency of pebble storages. It is possible to obtain the same performance with a volume fifteen times less. The silica gel beds are relatively unaffected by thermal losses so there is also a saving on insulation. On the other hand, the two-vessel store introduces a fresh storage technique. As Howell (1986) explained, the idea relies on the chemical reaction that occurs when acid and water are mixed; heat is then released. Hence, for heat storage it can be used to drive water and acid into separate vessels where they can remain for years as stored energy. By allowing the acid back into the water the stored heat is released.
It is necessary all over the world to reduce the cost of solar collectors although this may appear in the guise of increased efficiency at the same cost. This is tantamount to saying that as production increases and the days of handmade collectors pass, the labor content of the product will reduce to a minimum. As the only other major production cost is the cost of materials, the other move must be toward cheaper materials.
Although copper and aluminum make excellent devices to heat water, as collector material one must not forget that they are only intermediaries. The objective is to heat fluid not metal. Therefore, future research on solar collectors is into the use of plastics, and many more alternatives might follow which combine the advantages of suitability, mass production, cheap raw materials, and long life. Replacement of glass with a layer of clear fluorescent tubes reduces the cost almost fivefold.
It is expected that within the next two decades solar energy, whether transmitted through electrical lines or used to produce hydrogen, will become the cornerstone in the global energy policy. In the future, wherever solar energy is abundant, hydrogen can be produced without pollution and shipped to distant markets. For this purpose, the Sahara Desert in Africa can be regarded as the solar-hydrogen production area from where the hydrogen can be transmitted to consumption centers in Europe. Germany leads the effort to develop solar-hydrogen systems. There are demonstration electrolysis projects powered by PV cells already operating in Germany and the solar energy rich deserts of the Kingdom of Saudi Arabia. Germany spends some $ 25 million annually on hydrogen research projects.
The invention of optical fibers has led to extensive studies on the traditional methods of illumination and sterilization using the sun’s radiation. Optic fibers provide a pathway to transmit solar beams almost anywhere. £rnar (1995) has explained such transmission of solar energy from sunshine-rich desert areas to exploitation
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Fig. 7.14 Evolution of modern civilization (Barbir 2005, unpublished) |
centers. The solar radiation incident on the Fresnel lenses is focused at a point where the entropy of the system is greatly reduced. If the temperature of the point of focus is 300 °C and the ambient temperature is 27 °C, then the entropy of the focus is reduced by about half. Searching for similar entropy-reducing natural phenomena is an important task in energy science. The application fields of solar energy are well known and rather traditional, but new technologies will have an impact and will eventually be put to practical use.
In the two past centuries there were many revolutions that propelled society into a new mode of development and the majority of these revolutions are energy related as shown in Fig. 7.14. It seems that in the future energy-related revolutions are going to take place in addition to stress on water resources, which might be relieved through use of the practically inexhaustible solar energy supply and desalination plant production of additional water for the survival of humanity. Hydrogen energy is also related to water production in this respect.
