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Application Principles
As mankind enters the 21st century, people are faced with both appealing development opportunities and serious challenges. The mankind ’s ever-increasing demand on energies and the increasingly serious environment pollution due to acquisition of these energies have some bearing on the existence environment of the mankind himself and the sustainable development of world economy. To meet this challenge, the governments and scientists of various countries have been exploring and researching for dozens of years in order to discover a non-pollution and reproducible energy. At present, people can affirmatively say that this unremitting exploration and research has achieved huge progress-utilize reproducible energies to meet the mankind’s need of energies, for example, solar energy, wind energy, biology energy, etc. Among these energies, solar energy (PV technology) is a kind of reproducible energy with sophisticated technology, reliable performance, long life, convenient usage, no pollution, no noise and easiness for large-scale production. |
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The sun is a massive energy source. It emits energy of 3.8×1020MW per second in the form of ray radiation to the outer space. One in a 2.2 billion of the energy is projected to the earth, and the energy the earth receives from the sun is in a year can be up to 1.8×1018KWH, which is an extremely huge energy irreplaceable with any other form of energy. Solar cell is a semiconductor device that directly converts solar energy into electric energy. By combining large numbers of solar modules (mainly silicon solar modules), a PV power station can be established, which can provide reliable energy to industry agriculture, communication and human life s a convenient power station. From 1970s to the beginning of 1990s, PV power stations were mainly used to provide household electricity for residents in areas short of electricity or without electricity and also to provide maintenance-free power sources for communication, microwave relay station, petroleum pipeline and gas delivery pipeline cathodic protection, maritime navigation marking lights, etc., which achieved great success. Since 1990s, cost of PV power station has dropped substantially, and more importantly, unending usage of conventional energies causes serious pollution to the environment the mankind lives on, therefore utilization of solar energy in a massive scale has been an effective way of preventing pollution and improving the existence environment of the mankind himself.
Developed countries like America, Japan, Germany, the Netherlands and Australia all increase investment in PV power technology and production in succession, thus expanding the scale and field of its application. One measure is to build large-capacity PV power stations, for example, America has built a PV power station with a capacity of 7MW,supplying power for a small city. Another measure is to quickly apply the PV power system in buildings, for example, install the system on the roof to provide urban residents with electricity for living, combine photovoltaic modules and the buildings to replace the present glass walls when constructing public buildings, like airports, hotels, etc., and establish the so-called solar energy buildings. |
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This kind of solar energy building has multiple functions. In the daytime, it not only can generate power and store the power in batteries or be combined to the electric grid, but also can let some sunshine permeate, providing lighting and heat source for the room. In the evening, energy inside the batteries or electric power of the electric grid can be used to provide electricity for lighting and warming, etc. In the long run, it plays an important role in greatly reducing the shortage of electricity at peak time in large cities. In the meantime, since solar modules can be designed and manufactured according to requirements of buildings and conform to the style of modern architecture, they are more beautiful and scientific than the currently extensively used curtain-wall glass, and become a new eye-catching landscape in modern metropolises. |
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Engineering Implementation
During the installation and construction of PV power station or household system, consideration should first be given to the following factors:
1．PV power system shall be designed in such a way that its highly reliable performance and normal operation under severe conditions can be guaranteed. Meanwhile, the system is required to be easy for operation and maintenance, thus convenient for users’ operation and daily maintenance.
2．Considering the low-cost design, manufacturing and construction of the complete set of PV power system, standardized and modularized design of the equipment and enhancement of the versatility and interchangeability of spare parts, it is required that the system shall reserve expansion interface for the future increase of scale and capacity.
3．During concrete implementation, the solar module shall be installed with appropriate azimuth angle and inclination angel, so as to ensure that the solar module achieves most optimized performance. Selection of the installation place shall guarantee that the module can be irradiated by sunlight from 9:00 AM to 3:00 PM during days with minimum exposure time throughout the year in the local area.
4．Installation structure of the module shall be able to resist environmental stress of wind, snow, etc. and the mounting holes shall guarantee easy installation and protection from mechanical stress. It is recommended to use correct materials for installation structure so that corrosion of the module frame, installation structure and materials could be reduced to the minimum. |
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As required, PV power system is generally installed outdoors to endure the test of wind, rain, sun, etc. Continuous and stable power supply is required. As for natural and weather conditions, most consideration is given to continuous overcast and rainy days. Therefore energy balance design shall be made for the power system, and the operation mode with most severe requirement for PV power system shall be adopted for design. In this way, it can be ensured that the system can provide normal power supply to the loads at different times, in different seasons and under different climatic conditions.
When the photovoltaic module operating, it shall be installed in a direction so that sunlight irradiation can be received at the maximum. In consideration of the change of sunlight incidence direction in a day and the difference of solar altitude from the horizon line in winter and summer, it is recommended that generally the module shall be installed inclined towards the equator. That is to say, in the Northern Hemisphere the light-receiving surface of the module shall be directed towards the sough and in the Southern Hemisphere the light-receiving surface of the module shall be directed towards the north. Generally, for the angle between the module and the ground, reference shall be made to local latitude±(5°~10°)。 |
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