Views:9 Author:Site Editor Publish Time: 2018-08-20 Origin:Site
solar thermal power generation has the following advantages compared with photovoltaic power generation:
1) Solar thermal power generation output power is stable, power is adjustable, easy to be connected to the grid
At present, solar thermal power generation systems can improve the output characteristics by adding heat storage units or by supplementing combustion or operating in conjunction with conventional thermal power. Photovoltaic power generation is greatly affected by the intensity of solar radiation. After the Internet, it brings a lot of pressure to the power grid. The power generation form is unique, and it is difficult to merge with traditional power plants.
− Improve the output characteristics of CSP by tank heat storage (tank and tower CSP). Excess heat is stored during the day, and stored heat is used to release electricity during the night. This enables continuous power supply of CSP to ensure current stability and avoid the problem of peaking in the network that is difficult to solve by photovoltaic power generation and wind power generation. According to different heat storage modes, the utilization hours and power generation of power stations can be improved to different degrees, and the regulation performance of power stations can be improved.
− Improve the output characteristics of CSP by supplemental combustion or combined with conventional thermal power. Solar thermal power stations can be supplemented by fossil fuels or combined with conventional thermal power, so that they can continue to generate electricity at night or on a continuous cloudy day, and even run the base load with a stable output, so that the annual power generation can be obtained for about 7000 hours.
2) Solar thermal power generation without pollution
Photothermal power generation is a clean production process, which basically uses physical means for photoelectric energy conversion, which has minimal environmental hazard. The CO2 emission of solar thermal power station has a life cycle of only 13~19g/kWh. The Achilles heel of photovoltaic power generation technology is that the solar cell has a large loss to the environment during the production process, and it is a production process with high energy consumption and high pollution. Industry experts believe that the energy saved by solar cells during their life cycle is not economical compared to the resources they consume to produce solar cells themselves.
According to different ways of concentrating, CSP technology is mainly divided into: tower, trough, dish and linear Fresnel. The common point is to use different technologies to heat the working fluid, and then drive the steam turbine to generate electricity. It can also use the Stirling engine in the process of converting thermal energy into electrical energy. Both trough and tower photothermal power plants have now achieved large-scale commercial operation, while the dish and linear Fresnel are in the system demonstration stage.
1. Trough solar thermal power generation
A parabolic reflector is used on the solar collector to focus the sunlight onto the central focus line. Under the effect of the day tracking system, sunlight is continuously concentrated on the collector tube at the focus line position. The hot fluid flowing in the heat collecting tube continuously transfers heat to the high pressure steam generator, and heat is exchanged through the heat exchanger to generate hot steam. If the generated steam is used for power generation or heat supply, the hot steam is subjected to work or heat release, and then compressed and condensed and returned to the hot steam generator, and is again heated to become a circulating steam of the closed loop system; if the produced steam is used for If other production processes are consumed, water is required. At the same time, the heat medium fluid passing through the heat exchanger will also be returned to the heat collecting field and heated again. In order to produce steam when the solar energy is insufficient, a heat storage tank can be placed in the system to store surplus energy, and the system can be replenished when the solar energy is insufficient, thereby increasing the utilization efficiency of the solar energy.
2. Dish solar thermal power generation
The disc type is also called the disc type, and its main technical feature is the disc-shaped parabolic concentrating collector, which is also a point-focusing collector, which can collect hundreds to thousands of times, which can produce very High temperature. A thermoelectric conversion device, such as a Stirling engine or a Rankine cycle heat engine, is installed on the receiver to directly convert thermal energy into electrical energy. It can be used in single or multiple units in parallel, suitable for small-scale power generation, so it is more suitable for remote mountainous areas away from the power grid area, and distributed off-grid power supply.
3. Fresnel-type collector power generation
The Fresnel-type heat collection system is shown in Figure 8. In 1990, Australian scientists summarized the experience of trough and tower, and proposed the concept of compact linear Fresnel reflector concentrator and steam generation system. Designed by FRAUNHOFER in Germany in 2002, Solamendo of Belgium produced a 5,000 m2 Fresnel solar concentrator. Compared with the trough type, a key advantage of this system is that Fresnel's focusing ratio is large, and relatively high temperatures can be obtained. The basic and motor required per square meter of mirror are few. The system needs to be replaced by using a standard plane mirror. The method of processing the curved mirrors keeps all the mirrors close to the ground, reducing the use of wind loads and steel, thereby reducing costs.
4. Tower solar thermal power generation
As shown in the figure below, the tower system has the characteristics of large scale, short heat transfer path, low heat loss, high concentration ratio and high temperature. It is the lowest power generation cost in several CSP systems. It uses an array of heliostats formed by a plurality of heliostats to reflect solar radiation onto a heat sink placed on top of a high tower, heating the heat absorbing medium to generate steam directly or to generate steam after heat exchange. The drive turbine drives the generator set to convert solar energy into electrical energy. The whole system is mainly composed of four basic parts: concentrating system, heat absorbing system, heat storage system and power generation system.
At present, trough and tower CSP have been commercialized, and the share of Fresnel and dish technology is still very small. In the short term, there is no sign of large-scale development. The world's trough-type CSP systems account for the highest proportion because of the high initial investment in tower-type CSP systems and the difficulty in energy storage in dish-type power generation systems. However, the tower-type CSP system has high comprehensive efficiency and is very suitable for large-scale and large-capacity commercial applications. In the planned construction of the CSP project, the proportion of towers has exceeded the trough technology. We believe that the future tower-type CSP technology will be the main technical genre of CSP.
At present, the trough concentrating system, which is widely commercialized, is mostly tubular truss type, which consumes a lot of steel, is self-important, has high cost, and is single-axis tracking, with low concentration ratio and low efficiency of photothermal conversion. The dish concentrating system has high optical efficiency and low tracking error, and adopts a high-efficiency collector, so that it has high thermoelectric conversion efficiency and the like. However, when the concentrating area is increased, the design difficulty of the supporting frame body is increased, and the amount of steel used is greatly increased due to the requirement of the wind resistance level, resulting in an increase in system cost. As a linear Fresnel concentrating system, although the construction and maintenance cost is relatively low, it has occlusion and shadow problems, resulting in low system efficiency, and the concentrating multiple is only tens of times. The problem of energy loss in the heat pipe is also a problem that cannot be ignored on linear Fresnel collectors.
Compared with the above-mentioned shortcomings, the composite disc of Qinhuangdao Yuyang Solar Energy Technology Co., Ltd. has the following advantages as a new type of concentrating system:
(1) Focus fixed design (ie, system heat collecting device fixed) - has the characteristics that the tower focus does not move. The invention reduces the design difficulty of the receiver of the solar concentrating system, and solves the problem that the pipeline installation is ubiquitous in other systems.
(2) High-precision dual-axis tracking, high-focus focusing design - high temperature utilization.
(3) Optimized arrangement of mirror field and receiver form - solves the problem of occlusion and shadow in the linear Fresnel mirror type collector system.
(4) Low-profile design - good wind resistance, simple structure, small amount of consumables, convenient installation and saving construction cost.
(5) Application of graphite column for heat collecting core component——Using graphite column with good thermal conductivity, corrosion resistance and chemical stability, the collector is integrated with the heat conduction energy storage device in a straight-through manner.
Qinhuangdao Dongyang Technology Co., Ltd. is a high-tech enterprise specializing in the research and development of solar thermal products. In 2014, relying on Qinhuangdao Yuyang Solar Energy Technology Co., Ltd. to complete the research and success of solar tracking servo organization, and formally form a strategic alliance.
The main products of Qinhuangdao Dongyang Technology Co., Ltd. are dish-type and trough-type automatic tracking solar thermal system. Dongyang can provide solution planning and implementation services for solar thermal cluster field system, as well as system design and implementation services for medium and high temperature photothermal utilization projects, such as heating, cooling, drying, fermentation and desalination, and completed cooperation with other units. Several photothermal power pilot projects.
The solar photovoltaic system and equipment of Qinhuangdao Dongyang Technology Co., Ltd. can be applied in a wide market space. In addition to power generation, it also covers agricultural, industrial auxiliary, solar building integration, desalination and other application fields.