The global encounter with the financial crisis is not the oil crisis, but the developed countries led by the United States have raised the development of new energy to an unprecedented height, and the investment in new energy has accelerated. In early April 2009, US Secretary of Energy Zhu Yiwen wrote an article in Newsweek, calling on the United States to abandon oil, master its own energy destiny, and build momentum for new energy development. The Obama administration hopes to use the guidelines of the New Energy Policy to greatly promote the transformation of the US economy. This will not only create a new energy industry, but will also increase millions of jobs, thus reversing the US economic downturn. The United States hopes and believes that the industry that will deliver the United States to the commanding heights of the world economy in the future is the new energy industry. In his inauguration speech, Obama also revealed that one of the new energy policies in the United States is to curb the rise in petrochemical energy prices. Failure to do so will fuel our hostile forces and threaten our planet. It can be seen that whoever can gain an advantage in the new energy strategy competition can continue to be the leader of the world's technological innovation, the locomotive of economic development, and the makers of new international standards in the next industrial revolution.
This article only makes a prediction on the trend of solar power technology in new energy. First, the price of key photovoltaic devices will be further reduced, from $1,500/W in the early 1950s to around $1/W (current price is $4/W); second, space technology, microwave The combination of technology and photovoltaic technology; third, China will increase the intensity of new energy development, in the urban planning of GDP growth will be a single piece, that is, the contribution of new energy in GDP growth, and gradually solve the problem of distributed power supply network.
1 Solar power generation and microwave transmission plan
1.1 Cosmic solar power generation
The temperature of the surface of the sun is about 2 yi 107, and the energy released is 1 1024 kW. Among them, the earth may use energy of 1.8 y 1014 kW. If averaged on the surface of the earth, the available energy is 183 W/m2 (the total amount of sunshine is 1 400 W/m2).
In addition to the above-mentioned energy available on the surface, people can also capture solar energy from the air. The SSPS plan is based on this.
The original idea was to start the basic research phase from 1973 to the end of 1984, to prototype the concept prototype by the end of 1992, and to start trial production of practical devices. By 1998, solar photovoltaic power generation and microwave transmitting and receiving devices that could be put into practical operation were given.
As a new energy system in the 21st century, nuclear fusion power generation systems and soft energy systems are promising. In the soft energy system, the Solar Power System (SSPS) is very eye-catching.
If the development process of the cosmic solar power system is classified, it can be roughly divided into five stages.
The first phase is the envisioned period. In 1967, the US Air Force Raytheon successfully conducted a test to provide power to a simulated helicopter via microwave. This test was carried out for 10 hours and successfully maintained the helicopter at a height of 18 m. This is the first power microwave transmission test in the world.
The second phase is that NASA began to establish a cosmic solar power system. NASA and the Department of Energy officially conducted the development and research of cosmic solar power systems during the first half of the 1970s and the first half of the 1980s. The system representing this research is the cosmic solar power system developed in 1979. This system is to build a space station with a huge solar cell with a width of 5 km and a length of 10 km on a satellite geostationary orbit with a height of 3.6 I and 104 km, and convert the generated electricity into microwaves and transmit it to the ground. It is said that the cosmic solar power system is expected to have a power generation capacity of 5 GW.
The third stage is that the United States continues to study whether it is possible to achieve a more economical cosmic solar power system and to report every 10 years.
The fourth stage is to study the period of the cosmic solar power system with new concepts and new ideas. Among them, the representative solar tower cosmic solar power system with a height of 6 000 km has been well received. The frequency of transmitting microwaves is 2.45 ya at 3.5 GHz, which satisfies the microwave conditions required for domestic microwave ovens.
The fifth stage was the conceptual design period. NASA implemented the conceptual design of the cosmic solar power system based on previous research results, according to the requirements of the National Assembly in September 1998.
The Japan Space Development Agency, the European Space Agency and the Canadian Space Agency also proposed matters that should be resolved as quickly as possible through international cooperation: research on the main core technologies; conduct wireless power supply experiments in the atmosphere; and investigate the long-term effects of microwave emissions on ecosystems. Conducting cosmic solar power system experiments through the International Space Station; taking advantage of the cosmic solar power system as an opportunity to develop international cooperation for new energy development.
The Space Development Corporation plans to invest approximately $80 billion over the next 25 years to conduct research and development work on the solar power system. According to this plan, it is planned to build a practical cosmic solar power generation system with a power generation capacity of 1 GW in 2010. In addition, not only the research and development of the above-mentioned basic and core technologies will be carried out, but also a cosmic solar power system satellite with a power generation capacity of 6 GW will be launched to orbit around the earth, and electricity will be transmitted from space to the ground through microwaves, and ionization will be performed. A pilot study of the same propagation characteristics of the layer and the atmosphere.
If the plan goes well, it is equivalent to constructing a technology that is faster and more practical than the fast neutron breeder reactor and nuclear fusion reactor, which is worthy of attention.
1.2 Overview of the SSPS Plan
Some years ago, people imagined using microwaves to transmit electricity from distant places. In 1969, WC Brown of Raytheon Company launched microwaves from the ground to the sky, and returned the received power to a helicopter through the receiving antenna. The helicopter equipped with an antenna flew in the air with the received electrical power, which was the earliest successful pioneering test.
By the 1970s, countries had successively developed experiments on microwave transmission and receiving electricity. The electric power is generally around 2 450 MHz and 10 kW. In 1974, the University of Miami published a paper entitled "The Large-Scale Project on Power Generation and Transmission from the Universe." The conceptual device model is shown in Figure 1, referred to as the SSPS (Satellite Solar Power Station) program, which is the first to put solar photovoltaic power generation and The two latest concepts of microwave transmission are combined.
One of the important parts in Figure 1 is the panel in the transmission of solar photovoltaic cells. Its occupied space station area is approximately 6 km and 26 km, and can deliver 8 GW (1 GW = 109 W = 106 kW). It is then sent to the Earth as a microwave, removing losses and reaching a ground power of approximately 5 GW. The cost structure of the SSPS plan system structure and various parts of the system is shown in Figure 2. The first is that the cost of launching solar cells and microwave generators into the universe accounts for a large share, which is expected to account for more than 1/2. Secondly, the cost of photovoltaic power generation for solar cells also accounts for a large proportion; The cost of antennas, etc., is not expected to exceed 16%.
The efficiency of the solar cell in Figure 2 is 12.3%. If the conversion from sunlight to electricity is not considered, the power generation is 5 GW, while the solar cell power generation is 8.85 GW. Therefore, the overall system efficiency is calculated to be 56%.
1.3 Power transmission (emission) system
The quality of the power transmission system will affect the overall efficiency of the entire power generation system. This system includes the following four major changes:
1) solar power;
2) DC power 寅 high frequency microwave power;
3) Microwave electric power (satellite) 寅 microwave electric power (Earth);
4) Microwave 寅 commercial power.
The most technically advanced component of the system is the conversion of electrical power from solar photovoltaics into microwaves.
At the beginning of the study, a single ultra-high power microwave tube was used as a microwave transmitter, so the performance of various forms of microwave tubes was compared. It was originally thought that the klystron was more suitable for high-power transmission, but it was found to be inefficient; it was later switched to ultra-high-frequency power amplifier (CFA), but its disadvantage was high price and difficulty in heat dissipation; The power of the magnetron is connected in parallel.
As is well known, magnetrons are the most commonly used microwave tubes for domestic microwave ovens, which have the advantage of low cost and can change the output power by controlling the phase. Finally, a magnetron and a heat dissipating antenna are combined to form a unit, and the microwave transmitting array is composed of a plurality of units.
1.4 receiving system
The conceptual diagram of the receiving system is shown in Figure 4. If a reference RB (Reference Beam) is set on the ground, it is in communication with the satellite transmission and controls the direction and intensity of the satellite. After synthesizing the power density of the microwave emission point (on the satellite), the power density of the orientation point is 1 km (the Gaussian amount of the central part is Gauss is 23 kW/m2), so the power density around the directional point RB on the ground. Can be corresponding to:
A schematic diagram of the arrangement of the receiving antenna array is shown in Figures 6 and 7. From a distance, the receiving antenna array arrangement seems to be a group of roofs, but the flat part is made into a mesh curtain shed, which can completely block the microwave.
The purpose of this roof structure is to prevent the microwave from passing under the net, and also to allow sunlight and rain to flow out of the mesh, so that the bottom of the net is very safe. Of course, the size of the mesh hole needs to be determined through multiple field tests, it is best to completely block the microwave radiation, so as not to cause damage to the organism. If you can do this, you can of course set up the microwave receiving station in the suburbs of the city.
1.5 SSPS plan test results
The different components of the Cosmic Power Transmission Plan (SSPS) have been subjected to low-power simulation tests on the ground, and preliminary results have been achieved. The most important consideration is the cost, which is being continuously improved to minimize the system cost.
The cost budget is classified as follows.
2 Recent advances in space solar power generation
2.1 US private solar companies involved in space solar power plants
The SSPS program developed by the National Aeronautics and Space Administration (NASA) and the Pentagon in the 1960s was slow to develop because of the high cost. Today, many private solar companies have been involved in this research. For example, the US Pacific Gas Power Company (PC&E) has recently announced that it will work with and purchase electricity from a solar energy company (SolarEnCorp) that claims to be able to efficiently harvest energy in space. As a result, they took the first step in developing solar energy in outer space—setting solar panels in orbit around the Earth, then converting the DC power into radio waves for transmission back to Earth, and then receiving it from the ground's power reserve. It is converted into low-frequency AC power and supplied to thousands of households.
The project plans to provide 200 MW of electricity by 2016 and 250,000 homes in 15 years. If the progress is smooth, the dream can come true in the year.
Obviously, the plans of these private companies are very similar to those of the original park. The satellites carrying photovoltaic panels are first launched into orbits of 22,000 miles (about 35 400 km) from the equator and remain in position with the Earth. Relatively unchanged. The width of the solar panel will be several kilometers, and the system will convert it into electrical energy after collecting solar energy, and then convert it into radio waves to return to the earth. The ground receiving station is to be built on the outskirts of Fresno, California.
According to Pacific Gas Power Company's rough estimate, the project will cost about US$2 billion, mainly for the construction and launching of satellites for the Earth's solar energy base. Daniel Carmen, a professor of energy and resources at the University of California, Berkeley, believes that the most serious challenge facing space solar power today is the cost of implementation, especially at a time of the current global economic downturn. This plan requires billions of dollars in capital investment, which is much higher than the 100 million US dollars needed for other renewable energy projects of the same size.
However, SolarEn CEO Garry is confident in completing the project. He said that the company has the ability to provide 1.2 billion watts of electricity and can commercialize power in the next seven years. The price of space solar energy can also be compared with other renewable energy sources. Prices are basically flat.
2.2 Japan's space solar market
Coincidentally, the Japan Aerospace Development Center (JAXA) is also studying a similar cosmic solar power system (SSPS), which is expected to start before 2030. The basic principles are similar to those in the United States, but Japanese scientists use microwave transmission at 2.45 GHz and 5.8 GHz. This technology has been used in industrial and medical equipment in Japan. At the research base in Hokkaido, Japanese scientists conducted ground-based microwave reception experiments using a 2.4 m diameter instrument. The ultimate goal of JAXA is to build a ground-based receiving station of approximately 5,000 square kilometers, producing 1 million kW of electricity and powering 500,000 homes.
However, space solar power is not perfect, and high-intensity radiation is likely to bring another environmental pollution problem. But proponents believe that as long as the area of ​​the ground-based solar receiving station is large enough, it will not harm humans, animals and plants. Therefore, the ground receiving station should choose a place with sparsely populated areas and a wide area, and it must also be equipped with an effective power transmission system.
Although it seems that these ideas are somewhat unrealistic now, the success of any project, whether in the United States or Japan, means a major breakthrough in the field of renewable energy.
3 10 years (1999-2010) new energy plan centered on solar power generation in Iwaki, Japan
Iwaki is one of the leading cities in Japan to develop new energy using large-scale solar energy. The city has a geographical advantage in enabling solar power generation because the annual sunshine time is as high as 2,100 h, surpassing Tokyo and other places.
3.1 The overall goal of the 10-year plan
The goal of the 10-year plan is to install 21 000 kW (21 MW) of solar power, in addition to wind power, solar thermal utilization, waste combustion power generation, and waste heat supply for steam turbines. Converted to crude oil to save 82 195 kL / g. The CO2 emission reduction is 31 130 t/g. The two slogans put forward are the city of clean energy recycling and the new 21st century city, Iwaki City.
3.2 Previous work
According to the staff's resentment, the new energy plan of the Ministry of Transport of Japan has taken Iwaki as a pilot, specifically introducing 300 kW of solar power plants in schools, parks, roads, public places, etc., and forming a new energy management network. The design was implemented during the 1997-Yuanyuanyuan source year, and the system's schematic diagram is shown in Figure 8. In the figure, each facility is powered by solar panels, and the system is connected by a DC 300 V bus and converted to AC 200 V by the inverter. The AC power is boosted to 6 600 V via a step-up transformer to form an AC power supply network. On the one hand, the communication network can communicate with the mains grid for two-way flow of energy; on the other hand, the signal is sent to the PV management center for centralized management, distribution and information storage of the power for safe and continuous operation of the system. When the utility power is cut off, it can be powered by the pre-stored 300 A·h battery pack, which can maintain the basic power consumption for one day. Therefore, the system also has urban disaster prevention capabilities.
The above-mentioned project cost estimate is 800 million yen (converted to 500 million yuan), and the state, municipal government, and regional development and revitalization companies are each responsible for one-third.
3.3 Summary of New Energy
According to the 10-year plan to take the path of resource recycling, the overall goal of the new Iwaki City is established, and the specific implementation and phase decomposition are as follows.
3.3.1 Background of policy development
1) The world's energy shortage energy consumption is increasing year by year; the dependence on oil is too high; the awareness of saving energy is weak.
2) Relying on new energy to solve problems solar power generation; solar thermal utilization; wind power generation; waste combustion power generation; using waste heat generated by steam turbines to supply heat.
3) The idea of ​​establishing an energy-recycling city solves the problem of environmental protection on the earth, and the awareness of environmental protection is continuously enhanced; the ability to resist disasters is enhanced; and the future becomes a city with long-term stability of energy supply.
3.3.2 Evaluation of various new energy economic and technical indicators
1) From the energy saving and emission reduction effects, solar power generation, wind power generation, electric vehicles, solar energy utilization, and waste generation are compared.
2) From the investment size compared to solar thermal utilization, waste generation, electric vehicles, solar power generation.
3) The amount of energy extracted from energy is compared with solar heat utilization, solar power generation, wind power generation, and waste power generation.
4) Comprehensive evaluation of solar power generation, solar thermal utilization, electric vehicles, waste generation, and wind power generation.
3.3.3 Energy saving and emission reduction indicators
1) New energy development, new power and machine number, solar power generation 21 000 kW; solar thermal utilization 15 100 kt; wind power generation 3 500 kW; waste heat utilization 760 kt; clean energy or electric vehicle 12 300 units; turbine exhaust heat supply 24 690 kW.
2) CO2 emission reduction solar power generation 3 820 t; solar thermal utilization 10 910 t; wind power generation 280 t; waste power generation and heat utilization 5 430 t; electric vehicle 36 000 t; turbine exhaust heat supply 7 090 t; 130 t.
3) Saving crude oil (after conversion) Solar power generation 5 285 kL;
Solar thermal utilization 15 100 kL; wind power 380 kL; waste power generation and heat utilization 7 510 kL; turbine exhaust heat supply 43 690 kL; total after 82 195 kL; accounting for 19.2% of total crude oil consumption.
3.3.4 Multi-sector division of labor throughout the city
1) Display of image projects and demonstration projects by the government and the administrative department to provide information and provide backup. The development sequence is solar power generation, thermal utilization, wind power generation, waste disposal, electric (or clean energy) vehicles, and the like.
2) The public mainly installs solar power installations and solar water heaters in their homes, using clean energy (such as natural gas) or electric vehicles.
3) Enterprise solar power generation and electric vehicle development; providing various energy-saving technologies and information; and launching various training courses to popularize new energy technologies to the public.
3.4 Energy saving effect of previous work
Iwaki City has established a 300 kW solar power generation system in 1997. The energy saving effects are summarized as follows:
1) Annual power generation capacity of 295,500 kW·h (about 80 households' annual electricity consumption);
2) The conversion amount of CO2 emission reduction is 56 t;
3) Saving crude oil (accounting) Court 2 000 t.
According to the development plan, an additional 560 kW solar power plant and a 350 kW wind power plant are planned to be launched in 2004.
The visual display of the city's PV management center was opened in December 2001 on Staff Day and Staff Day, as shown in Figure 9, which shows the intensity of daily sunshine and daily life of the staff in 2001. 00 Yao 19 : 00 different power generation.
4 Some ideas for the development of solar power generation in China
In the international arena, developed countries (such as the United States, Japan, Germany) generally promote two ways to promote the development of solar power: one is to purchase new energy devices (components) for private users, and grant a certain amount of subsidies, such as 50% of Japanese subsidies; Second, the privately-set solar power station can send surplus power to the national grid, commonly known as selling electricity, but need to apply for certain procedures, such as contract, the power company installs the counter-current power meter, and tests the solar power plant technology. Whether it meets the conditions of online access, etc. If the capacity of the device is large enough, the owner can get considerable benefits from selling electricity.
China has not yet formulated preferential policies for new energy development, but since 2009, energy conservation and emission reduction have been very high, and relevant departments have begun to demonstrate this problem. Relevant experts believe that it can be changed from centralized power supply to distributed power supply.
In modern society, users are not satisfied with the traditional power supply mode, and the requirements for the reliability and stability of power supply are getting higher and higher. The distributed power supply based on new energy is rapidly becoming popular in the world because it can be installed in the vicinity of users and can be used as a self-supplied power source for small and medium-sized factories. In this new situation, in order to achieve high power supply reliability, produce high-quality and low-cost electricity, and reduce the impact on the environment, it is necessary to build a distributed generation system that meets the requirements of the times. Distributed power generation has a good development prospect in the context of increasing contradiction between energy supply and demand and increasing environmental protection pressure.
The new energy sources used in distributed generation include natural energy such as solar energy, wind energy, tides, waves and geothermal energy. Distributed power generation has a concept called self-use, which is used by itself to reduce the proportion of power generation and Internet access, which will effectively alleviate the bottleneck problem that hinders energy development. In addition, distributed generation can also open up new ways to promote new energy.
Because wind power, solar energy or other forms of power generation have one thing in common, that is, low energy density and large area of ​​power generation equipment. The distributed power generation utilizes the roof and other places of each household, making it a small power point, which solves the problem of low energy density and large floor space.
At present, there are three major problems in the development of distributed generation in China.
First, there is insufficient understanding of the significance of developing distributed power generation. Since distributed power generation has just begun to spread in foreign countries, many scientific and technical personnel in China are not familiar with the basic concept of distributed generation, and it is not recommended to actively promote this work. For the above reasons, it is first necessary to popularize the concept, practice and significance of distributed generation, so that relevant personnel can understand what is distributed generation and the role of distributed generation in improving the reliability, energy conservation and environmental protection of power systems.
Second, there is a lack of corresponding laws and regulations. The establishment of a distributed generation system needs to solve the problem of access to the distributed generation equipment of the power system. Corresponding technical standards should be established, and relevant laws and regulations need to be established, which are currently restricted by the interests of certain power companies in the system. In addition, it is necessary to develop a feed-in tariff for distributed generation of electricity that takes into account the interests of all parties. Relevant regulations must also be formulated for related investments and returns.
The third is the lack of preliminary research. In the traditional power transmission mode, the power flow is basically stable, and distributed power generation will frequently change the power flow, so the protection and control of the distributed power system must meet the corresponding requirements. Although there are many related researches and equipment developments abroad, it is necessary to develop distributed power generation technologies and equipment suitable for China's national conditions while introducing foreign technology.
Power electronics and inverter technology workers must make due contributions to the development of new energy. For the most popular wind power and photovoltaic power generation, the most important protagonist is naturally the development of wind turbines and photovoltaic cells. But the controller is also an important part of the second place. This is the opportunity for power electronics technicians to play a role, such as solar photovoltaic systems, which are actually a frequency converter (including Internet access, two-way flow of energy, and multiple protections, such as islanding prevention). It is not difficult for a converter factory to switch to this type of product, but it needs to be re-opened and re-developed. It is not a simple change on the board and software. At least it is a dual PWM system. For example, Japan's Fuji and Hitachi have serialized products more than ten years ago. At present, some important solar photovoltaic image projects in China are mostly imported Japanese, American and German products. Therefore, the solar photovoltaic controller factory (or company) should be available for listing. Not only is it conducive to economic growth, but it can also expand employment opportunities. Two things in one fell swoop, why not do it.
5 Conclusion
This article is excerpted from the author's latest book "Solar Power Generation Technology and Applications", the power supply electronic technology industry peer reference, and please give corrections.
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