Solartechnology

1. Introduction

Solar energy is based on a modern technology that doesn’t need moving parts nor high temperatures to provide energy. Possibilities for using the solar energy are the photosynthesis, the photochemistry, the transformation into warmth and the direct transformation into electric current (photovoltaic).

In the following I would like to tell you something about the photovoltaic and the thermal energy.

2. History of Solar Energy

1839, A. Becquerel found the photovoltaic effect. His electrochemical experiment consisted of two metal plates which were put in acid.

Becquerel observed, that energy was produced, when sunbeams got on it.

About 50 years later, Fritts detected the same photovoltaic effect with an selenium cell. The efficiency of 1-2% and the costs for the selenium prevented the further development of the new technology.

In 1955 the “Bell-Laboratories” in the USA created the silicon-solar-cells with an efficiency of 6%.

In space engineering the new solar-cell proved its efficiency: The first satellite supplied with solar-cells was started successfully in 1958. The development moved on until today and goes further.

3. Warmth of the sun

Thermal solar-systems are already used for the support of the room heating, for heating the water you use in your household and in the swimming pool. For this, collectors, which turn the appearing sunlight into warmth, are used.

Through this the liquid in the collector, (water-glycol-mixture), heats up. This liquid will be transported into a heat exchanger where it passes its warmth to heating waters. After this it streams back.

If, once, the sun radiation doesn't suffice, especially in the winter, when the sun radiation isn’t as high as in the summer, then a boiler heats up the water to the desired temperature.

4.1. Current of the Sun

Besides from gaining warmth today the transformation of sunbeams into electrical current is in the center of interest.

Solar cells turn solar energy directly into electrical energy. This technology is called "Photovoltaic", in the technical language.

For the direct transformation of light into electric current solar cells, made of silicon, have proved to be successful. A plate from silicon is main part of solar cells.

The radiation of light causes a voltage between the metal contacts of the solar cell.

Appearing light loosens electrons from their structure inside the cell. These electrons are forced to move to the topside of the solar cell because they are attracted by the positive topside, which is formed while the sunbeams are appearing. At the topside the electrons form a surplus. Now the solar current can be used for electrical consumers.

To get an energy gain as good as possible, the single solar cells are linked together by metal contacts to efficient solar modules.

The voltage is independent of the light intensity. But the current which the cells can supply depends on the illumination.

The proportion of useful electrical performance and optical performance is called efficiency.

The solar cell doesn’t change itself because of this process; “almost endless”, it is able to produce energy.

When you want to use the photovoltaic effectively and economically, it requires a certain radiation intensity of the sun that is much lower in our area than in regions near at the equator.

To have current of the sun in times when the sun radiation is weak the current must be stored. Bridging the night hours or also some days with help of accumulator is already used on Pellworm.

To store energy of the sun in summer for the winter, it would require an enormous area need for solar cells, landscape consumption is growing simultaneously.

The great technical storage of the solar energy represents the real problem. There aren't any suitable methods for this today yet. So, solar cells don't make power stations dispensable in this country.

This manner of getting energy arouses economically interesting prospects for regions which are far away from current supply grids -- particularly countries in equatorial regions--.

The German current providers participate in the development of the solar power generation also.

You proceed with this on the principle of the division of labour: the possible applications of solar energy for the production of current and warmth are tested in great standard in the west.

And the main part for the support of the solar -- hydrogen technology lies in the south of the Federal Republic.

The current providers in the north of the Federal Republic however try to improve more the use of the wind energy.

4.2. Feeding the Current into the Net

The direct current, produced of the solar modulus, is led to a inverter over a module connection. In this inverter, the current will be transformed in alternating voltage. After that, you can use it in your household.

When you have got a current surplus, you can give it to the public mains and it will be reimbursed.

Current out of photovoltaic systems (also old systems): at least 50.63 euro/kWh.

5.1. Advantages of the Solar Energy

Our fossil resources like oil and natural gas become scarce, so we have to find and to use other technologies for getting energy.

In the moment the state support makes it quite possible to change to

regenerative energies. The Solar Energy is important for producing warmth. Its use is economical and its technology always becomes more efficient and is adaptable. Solar-installations can be integrated in every building - additional or from the beginning.

Solar Energy works

- noiselessly,
- exhaust-free,
- harmlessly and
- you can use it decentralized.
- Long-term usage or do-it-yourself it is very inexpensive.

Besides the costs for servicing and energy for the pump are no further running costs!

For example: A family of four persons needs about 150 liters of 45°C warm water each day. That corresponds to an energy-need of 6-8 kWh. In an average, you may economize about 60% of your warm-water-energy- need, in a year. In the summer you may cover your warm water costs up to 100% with free solar energy.

Solar energy is also

- environmentally friendly; 4 m²of solar panels reduce up to a ton of carbon dioxide every year, compared with a modern gas boiler! A projection showed that the installation of 400,000 solar-systems will economize about 75,000 tons of CO2.

This environment-friendly technology will be supported by the government, probably till 2003. With this support, the government wants to accelerate the installation of solar-systems in the private households.

5.2. Disadvantages of the Solar Energy

For getting current, the energy density of the radiation is relatively low in the Federal Republic.

At noon, when conditions are favourable, from about 1000 watt/m²10-15 can only be transformed into electrical useable energy because of to unavoidable losses.

The effort correspondingly is great.

For example: The solar power station Pellworm.

The area of the solar cells is about 3500 square meters all together, the solar cells are installed on an area of 28000 square meters. The performance 300 kW maximum sun irradiation corresponds to a power density of 10 watts per square meter. Modern hard coal -- and coal powered stations have a power density of 500 to 600 kW per square meter.

6. Support by the Government

Solar collectors of every manner are promoted with 170. DM per m². The promoting maximum amount for solar collector systems is 50.000, DM. Private persons, small and middle enterprise and also energy providers are able to make an application.

Since the beginning of the year 2000, renewable energies shall be supported with more than two billions DM. The support of solar collectors is a main emphasis.

Being promoted: Solar panels, Photovoltaic systems for schools.

On July 23rd 2001 the conditions of the Market incentive program have changed: No more promotion for: The expansion of available solar collectors.

The promoted systems have to be operated for at least 5 years.

Own constructions, prototypes and second-hand installations are excluded of the support. Solar collector systems for swimming pools also aren't supported.

7. The Future of Solar Energy

Our comprehension for technology has changed. Colossal and huge machines made of steal, fuming chimneys and the smell of petrol belong to the past. Today, people are fascinated by the possibilities of using energy which we find in our environment: Wind, water and especially the force of the sun. We have to go easy on with our fossil resources like petroleum! We should economize by using natural energy instead of using up fossil resources.

The environment will be protected, too, because emission will become almost nothing.

Producing electrical current and warmth by using the solar energy also means, that we would not spend so much money as we do today! More people will buy solar modules, so these will become much cheaper.

I think that we still can’t do without Solar Energy. Today a lot of people work very hard to improve these technologies every day. So it’s possible that the use of natural energy will replace the power stations in the futur.

8. Sources

Information material of the companies:

- PreussenElektra

- Wagner & Co

- Vaillant

- Kotulla, Solartechnik

Reference books about solar energy:

- BINE Informationspaket Solarenergie, 2. Auflage, Verlag TÜV Rheinland

- BINE Informationspaket Photovoltaik, 2. Auflage, Verlag TÜV Rheinland

- Strom aus der Sonne, Technik, Planung und Montage, Wagner & Co Solartechnik GmbH, Cölbe/Marburg 1998

Internet:

- www.solarserver.de/geld.html#markt

9. Vocabulary List