Solar energy in progress and future research trends

Future expectations

In general, there are two distinctive reasons for future energy researches. First, as a result of global warming, atmospheric and environmental pollutions due to energy consumption, present day energy pattern, dominantly fossil fuels, must be either improved in quality or more significantly they must be substituted with more environ­mentally reliable clean and renewable energy sources. The second reason for the future researches on energy progress 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 the future human generations on the earth might face extremely precarious positions. Additionally, population

Table 10

U-values of different types of window construction

Window type U-value (W/m2/°C)

Single-glazed window

6

Double-glazed window

3

With ‘low-E’ coating

1.8

With heavy gas filling

1.5

Experimental evacuated

0.5

double-glazed window

with transparent insulation spacers

For comparison: 10 cm

0.4

opaque fiberglass insulation

increase places extra pressure on the energy resources and the energy consumption per capita per day in developing countries which is about 10 oil-equivalent-liter and it is below one-tenth of that in industrial countries. In order to produce new energy sources independent of fossil and nuclear fuels the following points must be taken into future research programs.

1. the solar beam collector with a Fresnel lens or concave mirror,

2. electric charge separation by solar radiation, and,

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 the storage and the two most promising new devices are, ‘silica gel beds’ and ‘two vessel storages’. Silica gel beds try to improve the efficiency of pebble storages. It is possible to obtain the same performance with a volume of 15 times less. The silica gel beds are relatively unaffected by thermal losses, there is also a saving on insulation [92].

On the other hand, the two-vessel store introduces a fresh storage technique. As Howell [62] explained the idea relies on the chemical reaction that when acid and water are mixed then heat is 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.

With the world’s second hydrogen conference held in 1978, the possibility of hydrogen based energy concept started to draw perceptibly nearer. Whilst they are eminently suited to solar energy they are low in efficiency and the future works should concentrate on raising that efficiency.

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 material, the other move must be towards cheaper materials.

As collector material although copper and aluminum make excellent devices to heat water, one must not forget that they are only intermediaries. The objective is to heat fluid not metal. It is, therefore, sought in the future researches on solar collectors to use, especially, plastics, and many more might follow with combined advantages of suitability, mass production, cheap raw materials, and long life insurance. 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 Saharan 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 afford to develop solar-hydrogen systems. There are demonstration electrolysis projects powered by photo­voltaic cells already operating in Germany and solar energy rich deserts of the Kingdom of Saudi Arabia. Germany spends some $25 million annually on hydrogen research projects.

Invention of optical fibers let 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. Qinar [24] has explained such transmission of solar energy from sunshine rich desert areas to consumption centers. The solar radiation incident on the Fresnel lens is focused at a point where the entropy of the system is greatly reduced. If the temperature of the focused place 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 technology is having an impact and will eventually put into practical use.

[1] Environmental damage on:

2.1 crops and forests like flora,

2.2 cattle and fish like fauna,

2.3 global climate, and

2.4 materials.

[2] Impact on human health:

1.1 short-term impacts like injuries,

1.2 long-term impacts like cancer, and

1.3 intergenerational impacts due to genetic damage.

Solar energy in progress and future research trends

Spatial solar radiation estimation

In the previous sections, the modeling of solar radiation is discussed on a given site. However, in practical solar energy assessment studies, it is also necessary to have spatial (multiple …

Solar thermal collectors and applications

Extensive fossil fuel consumption in almost all human activities led to some undesirable phenomena such as atmospheric and environmental pollutions, which have not been experienced before in known human history. …

Heat transfer and losses

As explained earlier the easiest way of solar radiation collection is for low temperature heating purposes. It is well known that black surfaces absorb solar radiation more than any other …

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