1. INTRODUCTION
In most people’s minds, fujitsu T4220 Battery electricity is a clean source of energy when using lamps, televisions, refrigerators, air conditioners and other appliances, perhaps we did not realize the power of the damage to the environment, the actual coal-fired power generation on the environment damage is significant. China is now the world’s No. powers of greenhouse gas emissions, while the conventional electricity production using coal, oil, natural gas, power generation, has become China’s carbon dioxide and other greenhouse gases, one of the major sources of emissions, but also a large number of coal-burning emissions of harmful gases such as sulfur dioxide . When we use conventional electricity, we are in fact an indirect polluters, because we only created the demand for electricity supply, and thus indirectly on the environment caused by pollution. At the same time we are also victims of pollution.
The 21st century, mankind will face the realization of economic and social sustainable development fujitsu lifebook T5010 Battery, major challenges with limited resources and environmental protection under the stringent requirements of the dual constraints of economic development has become the world’s hot spots. The energy issue will be more prominent. Energy shortages in most countries of the world’s shortage of energy supply can not meet their economic development needs. In the long run, the world’s proven oil reserves can only be used in 2020, natural gas can only last until 2040 or so, even if the reserves are abundant coal resources can only be maintained Ersanbainian.
As the burning of coal, oil and other fossil fuels, every year hundreds of thousands of tons of sulfur and other harmful substances thrown the sky, the atmosphere has been seriously polluted the environment, directly affecting the health of residents and quality of life; the formation of acid rain in some areas, serious pollution of soil and water. The use of fossil fuels produces large amounts of greenhouse gases caused by the greenhouse effect; caused by global climate change. This issue has been referred to the global agenda, the relevant international organizations have held many meetings and restrict FPCBP95 , FPCBP95ap , FPCBP155 CO2 and other greenhouse gas emissions. Thus, in addressing the energy problems of mankind to achieve sustainable development can only rely on scientific and technological progress, large scale development and utilization of renewable and clean energy.
Solar energy has the reserves of the “unlimited nature of the” Solar radiation energy per second is about 1.6 × 1023KW, within one year of the total solar energy reaching the Earth’s surface of standard coal equivalent to a total of about 1.892 × 1013 100 billion tons, is the world’s proven reserves of primary energy ten thousand times. Relative to the finite nature of conventional energy, solar energy has the reserves of the “unlimited nature of” inexhaustible. For the other sources of energy, the solar energy for most areas on the planet with the existence of universality, capable of being drawn. This is the conventional energy-deficient countries and regions that solve the energy issues of the prospects. The use of solar energy as clean wind energy, tidal energy and other clean vgp-bps2 energy sources, like its development and utilization of time does not produce almost no pollution. The economics can be used two ways to see the economics of solar energy utilization. First, solar energy inexhaustible, but also in receiving solar energy without the imposition of any “tax” can be anywhere access; 2 in the current level of technological development, the utilization of solar energy is not only possible and feasible. In view of this, solar energy will convert the energy structure in the world to assume a heavy responsibility, an ideal alternative energy sources.
2. Solar Cells
No. 1 50’s the advent of practical silicon solar cells, photovoltaic technology, opened the curtain, but also opened a new chapter for human use of solar energy. Since the solar cells into space 60 years, since the 70’s into the ground application, solar photovoltaic technology is developing rapidly. Since 1990, the global market for solar photovoltaic power generation sales to an annual average rate of 16% increments, the vgp-bps2a , vgp-bps2b current total generating capacity reached 800MW, equivalent to 20 million U.S. households annual energy consumption. 1997, the worldwide sales of solar cells increased by 40%, has become the world’s fastest-growing source of energy.
2.1 The impact of photovoltaic technology issues
Large-scale application of photovoltaic cells that affect the main obstacle is its high manufacturing costs. In many power generation technologies, solar PV is still the most expensive a form, therefore, the development of power generation technology, the main objective of the sun through the improvement of existing manufacturing processes, design of new battery structure, and development of novel battery materials to reduce manufacturing costs, etc. improve the photoelectric conversion efficiency. In recent years, show the steady development of photovoltaic industry trends, developments of the features are vgp-bps2c , VGP-BPL2 : increased production, conversion efficiency, cost reduction, applications are expanding. In 1998, the world’s solar cell output for more than 150MW, is more than double the 1994 output. Monocrystalline silicon solar cell, the average efficiency of 15%, laboratory efficiency reached 24.4%; polycrystalline silicon solar cell efficiency up to 14%, maximum efficiency of 19.8%; the stability of amorphous silicon solar cell efficiency, single-junction 6 ~ 9% laboratory of 12% maximum efficiency, multi-junction cells of 8 ~ 10%, the highest efficiency of 11.83% lab.
Recently, the Swiss Federal Institute of Technology M · Gretzer developed a titanium dioxide solar cells, its photoelectric conversion rate as high as 33%, and successfully introduced a amorphous organic materials to replace the electrolyte, so that it’s cheaper than a similar a large glass of your not much better and more convenient to use. It is expected that as technology advances and market expansion, the cost of photovoltaic SONY VGP-BPL2C cells would be substantially reduced. Can be drawn, in 2010, due to the decline in the cost of solar cells is expected to make photovoltaic technology into large-scale development period.
2.2 PV development of new technologies
In recent years, around the solar battery materials, conversion efficiency and stability issues such as photovoltaic technology has developed rapidly. Crystalline silicon solar cell research is high-efficiency monocrystalline silicon cells and low-cost polycrystalline silicon cells. Restrictions on single crystal silicon solar cell conversion efficiency of the main technical vgp-bps8 , vgp-bps8a barriers are: the surface grating cell shading effects; surface light reflection loss; light conduction losses; within the compound losses; surface recombination losses.
To solve these problems, in recent years developed a number of new technologies, mainly include: single-layer anti-reflection film; laser engraved groove buried gate line technology; Suede technologies; back point-contact electrode to overcome the surface of gate line shading issues; efficient back reflector technology ; optical absorption techniques. As these new technologies invented many new types of batteries, which greatly improved the conversion efficiency of solar vgp-bps8b cells, such as laser engraving tank buried gate lines, and new technologies, the high purification of crystalline silicon solar cells conversion efficiency of up to 24.4%.
MAnother characteristic of the development of photovoltaic technology is the thin-film solar cells made significant progress in a variety of new solar cells are emerging. Of crystalline silicon solar cell conversion efficiency may be high, but its cost was difficult to significant decline, while the thin-film solar cells to lower manufacturing costs has a very wide attractive prospect. Some years ago, the use of multi-layer film vgp-bpl8 structure, low-grade silicon material has made the cost of solar cells plunged 80 percent, is expected to 1O years to make the technology commercially.
And efficient development of new solar cell technology is to reduce the cost of photovoltaic cells a viable way to another in recent years, some new high-performance batteries continue to come out:
Copper selenide steel (CUINSE2, CIS) thin-film solar vgp-bpl8a cells: 1974 CIS batteries in the United States came in 1993, the U.S. National Renewable Energy Laboratory to make it the intrinsic conversion efficiency of 16.7%, due to CIS solar cells with a low cost (film Only silicon thickness of 1 / 100), can increase the band gap increase conversion efficiency (30% of the theoretical value of single crystal, polycrystalline 24%), there is no light-induced decline down, anti-radiation can be good, etc., all countries are competing to research and development, and actively explore the large-scale application of mass production techniques.
Silicon – Si tandem solar cell structure: Adoption of a-Si and a narrow band gap materials, cascading, is the effective use of long-wave sunlight, increased conversion efficiency of amorphous silicon solar cells a good way. It has low cost, low energy consumption, process a vgp-bps9 , vgp-bps9/b small, cheap and efficient and so on.
Chemical beam epitaxy (CBE) technology to produce multi-junction III-V compound solar cells: III-V compound (eg, GAAS, INP) has a high photoelectric conversion efficiency, these materials can match the multi-layer solar cell conversion efficiency to 35% or more. Multi-layer structure which is easy to use CBE law making, and can reduce the cost, ultra-efficient.
Large-scale photovoltaic nano-batteries: 1991, Switzerland M. GRATZEL research team led by Dr., aqueous solution for nano-TIO2 powder coating, and containing a variety of transition metal organic dyes and glass and other materials to produce ceramic pigments sensitive to solar cells, referred to as nano-battery. Calculations show that the conversion efficiency can be manufactured by at least 12% of low-cost vgp-bps9/s , vgp-bps9a batteries. The battery is used for large area of the outer surface of the building provides a broad prospect.
3. Development of solar cells
The progress of solar cells can be from their performance indicators, output, prices, etc. to assess. Performance solar cells have open circuit voltage, short-circuit current, fill factor, photoelectric conversion efficiency over the top, of which the most important indicator is the photoelectric conversion efficiency is about the efficiency of light energy into electrical energy.
Solar cell silicon solar cells and the main can be divided into two major categories vgp-bps9a/b of compound semiconductor solar cells. The following are described separately.
3.1 silicon solar cells
Silicon is the second most abundant earth element, but also non-toxic, with its production of high efficiency solar cells, so it is the most suitable for production of solar cell semiconductor material. In 1997, the world’s solar cell output of about 120MW, of which more than 99% of silicon solar cells. In silicon solar cells can be divided into the silicon, polycrystalline silicon and amorphous silicon solar vgp-bpl9 , vgp-bps10 cells three categories.
1. Monocrystalline silicon and polycrystalline silicon solar cells
Monocrystalline silicon and polycrystalline silicon solar cell is a P-type (or n-type) silicon substrate through the phosphorus (or boron) made the proliferation of P / N junction and the system gets. Monocrystalline silicon solar cell, high efficiency, long life, excellent performance, but the cost is high, and limited to the single crystal size, single cell area is difficult to do large for the relatively large diameter of 10 ~ 20cm of the wafer. Cast polycrystalline silicon cell is made of polycrystalline silicon ingot slicing, cost less than the monocrystalline silicon cells, single cells can also be done relatively vgp-bps10/b , vgp-bps10/s large (for example, 30cm × 30cm square pieces), but due to complex factors such as grain boundaries exist, less efficient than silicon cells.
Now, monocrystalline silicon and polycrystalline silicon battery research work focused on the following aspects:
(1) a buried layer of electrode surface passivation, secret back-gate electric field process optimization and contact electrodes to reduce the photo-carrier compound losses, improve the carrier collection efficiency, thereby enhancing the efficiency of solar cells. University of South Wales, Australia, the pro-Green laboratory using these methods, has created the current silicon solar cells under AM1.5 world-recognized 24% of the maximum vgp-bps10a , vgp-bps10a/befficiency.
(2) with excellent anti-Chinese shooting film, embossing the surface, high reverse back electrodes way to reduce light reflection and transmission losses, to improve the efficiency of solar cells.
(3) directional solidification method growth of polycrystalline silicon ingot casting instead of silicon, the estimated positive back electrode of silver paste, aluminum paste screen-printing technology to improve the silicon cutting, grinding, polishing and other processes, doing everything possible to reduce costs to improve the efficiency of solar cells. Currently the largest weight of vgp-bpl10 silicon ingot has reached more than 270 kilograms.
(4) thin-film silicon cells are also strong research and development. Calculations show that if in metal, ceramics, glass substrates were prepared by low-cost, thickness 30 ~ 50?m large area of high-quality polycrystalline silicon thin film, then the solar cell manufacturing process can be further simplified, costs can be significantly reduced. Therefore, polycrystalline silicon thin-film solar cells is becoming a hotspot.
Single crystal and polycrystalline silicon solar cells is now the world’s annual output has reached approximately 120MW. The highest efficiency silicon solar cells up to 18% ~ 24%. Aviation and aerospace, high-quality solar cells used in the AMO under the conditions of efficiency is about 13.5% ~ 18%, while the ground used for the mass production of solar cells efficiency under AM1 mostly in the 11% ~ 18% sony PCGA-BP1N , sony PCGA-BP2E or so.
2. Amorphous silicon solar cells
As the sunlight absorption coefficient of amorphous silicon on the large, and therefore non-chang thin silicon solar cells can be done, usually silicon film thickness is only 1-2?m, is a monocrystalline silicon or polycrystalline silicon cells thickness (0.5mm or so) 1 / 500 Therefore, resource consumption, less production of amorphous silicon cells.
Amorphous silicon solar cell is generally used methods such as high-frequency glow discharge to make silane (SiH4) gas decomposition of deposits made of. Deposition temperature is low due to decomposition (200 ? or so), so less energy consumption when production cost is relatively low, and this method is suitable for mass production, single cell area could have done much (for example, 0.5mX1.0m), neat beautiful. Another characteristic of sony VGP-BP2EA , sony PCGA-BP2NX amorphous silicon cells is a Blu-ray to respond to good, in general, even under fluorescent light can work, so it is widely used as electronic calculators and palm computer’s power, with an estimated usage of about 10 million per month and a . These advantages, so that amorphous silicon solar cells in the last 10 years to get the rapid pace of development, and in 1997 the world production is estimated to have reached more than 30MW.
Si because of its instability and internal structure of a large number of hydrogen atoms of deposit, with light fatigue effect (Staebler Wronski effect), so the stability of amorphous silicon solar cells after long-term problems. Over the past 10 years, after efforts to study, while improving, but not completely solve the problem, so as the power supply, not volume.
Amorphous silicon in crystalline silicon due to the lack of atomic arrangement in the rules of nature deficit. So simple a-Si p / n junction, the tunneling current is often dominant to render the yin properties, without rectification characteristics, would be unable to produce solar sony PCGA-BP2R , sony PCGA-BP2S cells. To obtain a good diode rectification characteristics, must be in the p layer and n-layer was inserted between the thick intrinsic layer i, in order to curb the tunneling current, so amorphous silicon solar cells typically have a pin structure. In order to improve
Efficiency and to improve stability, and sometimes made into a pin / pin / pin structure such as multi-layer laminated batteries, or insert some buffer layer.
Amorphous silicon solar cell research, are now mainly focused on improving the amorphous nature of film itself, in order to reduce defect density, precision design layers the thickness of the battery structure and control to improve the interface between the layers of the state, in order to achieve high efficiency and high stability.
The current single-junction amorphous silicon cells are able to achieve maximum PCGA-BP2SA , sony PCGA-BP2T efficiency of about 14.6%, a large number of production can reach 8% ~ 10%. The maximum efficiency of the battery stack can reach 21.0%.
3.2 compound semiconductor solar cell
In the compound semiconductor solar cells, the current research and application are more CaAs, InP, CuInSe2 and CdTe solar cells. As the compound semiconductor or less toxic, easy to cause environmental pollution, therefore low production PCGA-BP2V , sony PCGA-BP3T levels are often used in some special occasions.
1. GaAs solar cells
Potassium arsenide (GaAs) solar cells can be high efficiency, maximum efficiency laboratory has reached more than 24%, the general efficiency of space solar cells are used in 18% ~ 19.5% for. GaAs solar cells is currently mostly used liquid phase epitaxy method or metal organic chemical vapor deposition (MOCVD) technology to prepare, so costs are high, production is limited, reduce costs and increase productivity has become a focus. GaAs solar cells is currently mainly used in spacecraft.
At present, single crystal silicon film preparation technology is mature, low cost, and therefore silicon substrates, to MOCVD technology for the manufacturing of heteroepitaxial GaAs solar cells to reduce the cost of GaAs solar cells promising approach. At present, the efficiency of the battery has reached 20%. However, GaAs and Si crystal lattice constant related to a larger conducting guided quality epitaxial growth, the epitaxial PCGA-BP4V , sony PCGA-BP505 layer lattice mismatch serious, difficult to obtain high-quality epitaxial layer. To do this often begin by growing a layer of Si substrate with the GaAs lattice constant difference between the smaller Ge crystals as buffer layer, and then the growth of GaAs epitaxial layer, such Si / Ge / GaAs heteroepitaxial structure of the battery is constantly developing . Control the thickness of layers, appropriate changes in architecture, which allows sunlight photon energy of various wavelengths have been used effectively to present multi-layer structure of GaAs-based solar cell efficiency of nearly 40%.
2. InP solar cells: indium phosphide solar cells have a particularly good anti-radiation performance, so attention in space applications, the current efficiency of the battery has reached 17% ~ 19%.
3.CuInSe2 polycrystalline thin-film solar cells: the efficiency of the VGP-BPL1 , sony VGP-BPL4 battery has reached about 17.6%, and stable performance, as the polycrystalline thin-film batteries are very promising. But more complex components, manufacturing process repeatability is poor, affecting its development.
In addition, Cds / CdTe solar cell efficiency has reached 15.8%, but this battery-toxic and easy to result in environmental pollution.
4. The application of solar cells
Communications satellites are usually square to the various systems using solar power, and battery charging, water in the stars during the battery power to the satellite. In the past, extensive use of solar silicon photovoltaic cells square. At present, more advanced silicon photovoltaic conversion efficiency of up to 15%, but the battery can no longer meet the requirements of a large platform, now under development and the use of GaAs solar cells. The current single-junction GaAs solar cell conversion efficiency up to 18% in general, dual-junction GaAs solar cells up to 21-23%. This battery is not only efficient, but VGP-BPL4A , sony VGP-BPL5A also high temperature resistance, space radiation. Are now developing multi-junction GaAs solar cell, its conversion efficiency is expected to reach 30%. In order to further increase the efficiency of solar cell matrix, are now studying the use of solar concentrator panels, to increase the amount of solar energy, so that the solar constant increased to more than one. Over the past communications satellite battery commonly used nickel-cadmium batteries, with the increasing power of satellite, is being developed using nickel-metal hydride batteries. Ni-MH battery than the nickel-cadmium batteries depth of discharge depth, than the large capacity.
In order to “Deep Space 1? interplanetary probe become a reality, Air Force Research Laboratory made six key technologies, which are:
1. Lightweight solar phalanx. The future of solar panels using composite structures, connecting the various parts of the cable line will be eliminated, solar panels using plastic hinge. The use of thin-film solar cells VGP-BPL11 , sony VGP-BPL12, energy supply per kg weight of 116 watts, while the existing system for 40-50 watts. Multi-junction thin-film photovoltaic solar battery easy to start on the square in orbit. Light “smart” structure can be automated to eliminate vibration and thermal effects.
2. Flexible Integrated power supply and signal systems. By vacuum coating technology, so that battery and flexible thin-film battery components and barrier layer photovoltaic cells connected to form a multi-satellite buses. Flexible battery installed in the other sub-systems around.
3. Multifunctional structure.
4. Ultra-high density circuits.
5. Micro-electro-mechanical systems.
6. Light large optical system.
The United States October 24, 1998 launched the “Deep Space 1? interplanetary probe. Set-type solar cell using optical experiments. This solar cell matrix is actually only 13% of the area is coated with solar film, also with a 720 surface Filler lens, using a linear array of lenses Filler had gathered all the sunlight to these batteries. Since the battery is low, and the VGP-BPL13 , sony VGP-BPL14 battery light lens off than glass, so solar cells and reduce the weight matrix, and prices have changed cheaper. “Deep Space 1,” 2.6-kilowatt solar phalanx has four panels, the size of 1.1mx1.6m, total weight 58 kg. To enhance the capacity of radiation protection, the battery area on the thicker glass could have been done. There are two solar cells themselves, they are stacked together, can be 0.4?m ~ 0.85?m within the broadband spectrum of the energy conversion efficiency of 22% or more is expected. The disadvantage of this solar cell refers to a little square a little bit of error, capacity will be greatly inspiron 6000 battery reduced.
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