Solar energy in progress and future research trends

Photo-optical collection and transmission of solar energy

The need for new and renewable energy alternatives due to the depletion of conservative energy sources brought along also the studies on the efficient usage and transmission of available energies. As is well known, the major criticism against these energy alternatives is the problem of the energy storage [137]. Especially, unevenly distributed solar energy potential on the world causes unbalance in their production among various regions, some of which are relatively richer then the others. Such unbalances can be avoided only through an efficient energy transportation system.

If the storage or transmission of solar energy can be achieved then the coal, fuel oil and natural gas purchase of any country will reduce significantly. Such a solar energy transmission system will provide benefits for great trade centers, factories, and especially its application to photo­optical plants will lead reduction in the fossil energy consumption to a possible minimum level, and provide continuity (sustainability) in the renewable energy alterna­tives. Among the photo-optical transmission methods, Cinar [24] has considered the collection of radiation by focus - collectors. On the other hand, Baojun et al. [9,10] have investigated the solar energy relationships with fiber-optic radiation.

The most advanced recent technologies of solar energy collection as well as transmission are the fiber-optic applications. Collection of energy directly as light by concentrator collectors causes almost no energy loss in the transmission. Besides, since the collected solar radiation is

in the form of light, it can be consumed directly in the lighting problems. However, it can also be used in the heating and converted into electrical energy, if desired.

After the collection of the solar energy through focusing, it is refined by means of a lens system and finally, directed towards a fiber-optic glass transmission cable. The trans­mission is affected without any further loss to desired area in far distances as shown in Fig. 35. It is obvious that large diameter convex collectors collect the incoming radiation, and then lead it to another small diameter convex reflector. This small dish reflects the incoming radiation to the refining lens system, which refines the radiation twice after the focusing. The light ray that is refined down to the size of a needle, goes through a collector which includes a set of lenses that render the radiation into a parallel beams. Such a condensed solar ray enters without any loss into fiber-optical cable, which has a high transmission capability. The following items are used for the description of collector system in Fig. 35.

1. large diameter convex collector,

2. small diameter convex reflector,

3. refining lens system,

4. lens system that renders the solar rays into parallel form, and finally,

5. fiber-optic glass transmission cable.

Through the aforementioned system, the transmission of solar energy will be possible without losses from solar radiation rich regions of the world to poor regions. For this purpose, a regional energy transmission network must be constructed. In this manner, the solar energy can be transmitted to consuming countries where the solar radiation
possibilities are rather poor. In the case of central European and Arabian conditions, because of the low solar potential of the central Europe, the solar energy transmission from Arabian deserts is possible. Fig. 35 includes the fiber-optic glass cable transmission system among the selected regions of Arabia and northern Africa desert regions to European countries. The significance of this topic can be appreciated from the solar energy figures presented in Table 6 concerning the central Europe and Arabian Rub-Al-Khali desert. It covers about 660,000 km2 and from its each square meter it is possible to generate 1 kW/h solar energy. Solar energy collection area is about 360 X 109 m2, and hence, 360 X 109 m2 X 1 kW/ h = 360 X 109 kW/h = 360 X 109 MW/h solar energy can be harvested which is equal to 1.440 X 109 MW/year. By considering about 6 m2 of surface area for each collector, it is possible to find the number of necessary collectors as 360 X 109/6 = 60 X 109.

Due to the location and planning of some housing complex the lighting problems might exist and such undesirable situations can be avoided with fiber-optic system in the architectural designs. This system may even provide facilities for multi-story greenhouse activities. On the other hand, by leading the solar radiation over the fruits, vegetables and flowers in multi-story buildings, a covered agricultural production area may be established, and consequently, cheap and healthy food productions may become available in the market.

The application of fiber-optic electric energy production plants in the future may minimize the demand on the fossil energy, and may provide sustainability in the renewable energy availability, especially by exploiting abundantly existing solar radiation potential in the world. The collection of solar energy through fiber-optic glass and lens systems causes no losses, and additionally, transmission takes place instantaneously.

Especially the transmission of solar radiation to regions with very little variation will give opportunity for its direct use as light in heating, electric energy and hydrogen gas generation purposes. Photo-optical energy plants help to use the most significant renewable energy source of solar irradiation at low costs, and hence the demand on fossil fuels such as coal, petroleum and natural gas is expected to decrease leading to clean atmospheric environment. The solar energy obtained in this manner may also be used for electrolysis of water into hydrogen and oxygen elements

with the purpose of hydrogen energy production. This will increase the efficiency of solar-hydrogen energy prospects and future usages.