Research On Highly Efficiency Control System Of Heliostat In Center Solar Receiver

The contradiction between the ecological environment and natural resources on the one hand and economic and social development on the other is becoming increasingly conspicuous. The evil effects on human population of the so-called global warming have been well publicized. China is a developing country, now it is confronted with the dual task of developing the economy and protecting the environment. How to achieve sustainable development is the urgent need to address one of the main contradictions. Development and deployment of clean energies in a more cost-effective manner to phase in the fuel switch from coal-dominance to more shares of clean energy types such as natural gas and electricity are a serious problem. New energy resources such as geothermal energy, solar energy, wind energy and biological energy will be exploited, and energy saving will be encouraged. Large-scale development of solar energy markets can reduce electricity costs, energy and environment conducive to the harmonious development. Like other developing countries, China's per capita energy consumption level and the emitted sulfur dioxide are much lower than the world average level at present, and it will remain so by the end of this century. The UN's International Panel on Climate Change called on governments to step up efforts to curb global warming by reducing emissions of greenhouse gases such as carbon dioxide, which are produced by burning fossil fuels. Cleaner energy sources must be put to use quickly and broadly, both in the energy-guzzling industrial world and in developing nations, which cannot be expected to cut back on their energy use. For this part of China, especially the western areas, the most outstanding advantage lies in rich solar energy resources, promising huge potentials for development. It will actively develop new sources of rural energy; try to slow down the destruction of vegetation and the deterioration of soil quality caused by the shortage of energy in rural areas. While extensively expanding the traditional market, we should energetically explore potential markets worldwide.Because of the energy density of sunlight is relatively low and solar radiation is also intermittent, the technology of solar thermal power was blocked to a certain extent. The heliostat is a key factor to realize the solar power tower technology and is an important part to enhance the energy density of sunlight in the solar thermal power technology. As the first component in the energy transferring, the function of heliostat is tracking the sun orbit, sending out and focusing the sunlight, and reflecting the optical line to the receiver of solar power tower successfully. To undertake that the entire power system is under safe operation, the running of heliostat and the energy reflection must be reliable, stable and efficient. The system controlling isn't so convenient because of the mechanical error and any other factors however. All of the cautions can relatively leading to that the solar position shows some evidences such as the non-linear changes, and the external environmental factors may also cause an imprecise tracking precision. As we all knows, the generating capacity depends on the degree of solar radiation which is reflected by heliostat, to balance the working mode of the solar thermal power we should find a suitable way to increase the amounting of solar radiation as much as possible when the solar intensity is too weak, contrarily, we eager to decrease the amounting of solar radiation appropriately if the solar intensity is too strong. An urgent situation appears that we should discuss a way to minimize the difference of the radiation, and the total amounting of radiation of the year should be larger as much as possible. The effective way is to explore an optimum angle between the heliostat normal and the sunlight during the different situations of the weather. So a reasonable way of the controlling system must be researched because of the different hardware error and the unexpected weather conditions.This paper introduces the mechanical structure of the heliostat arrays; the control principle and the system design of the device, the mechanical structure of the automatic sun-tracking concentrating system as well as the way of the automatic sun-tracking have been given. The method for designing the system of tracking the solar energy is introduced and the possibility of the realization of this system is studied. We proposed an advanced way of the sun-tracking, according to the development of DCS, we suggest one kind of overall project of the DCS at solar power tower plants as well as the control function of its various subunits, and proposes the monitoring network and control system structure. Some main achievement has applied in the control system of solar power tower plants to realize the tracking of azimuth and zenith of the sun. Some achievements have applied in the field test; all of this application can be widely applied to the devices which need solar-trace in order to enhance the solar energy utilization efficiency. This paper also introduced the devices, configuration and basic principle of the tracking system and presented several common sun-tracking methods and application example of azimuth. The relationship among the solar azimuth and zenith and other parameters such as longitude, latitude and time was derived by Celestial theory. We raise the solving conditions of solar azimuth as well as the zenith angle and the solution formula was given using the characteristic analysis of the relationship curve. The formula can reflect the orbit of sun moving by the experiments.To the problem that the heliostat control system of solar power tower is a complex nonlinear multivariable process and the mathematical model is hard to establish, the traditional control is difficult to apply to such a system. Most of fuzzy control strategy applied to the occasion that the mathematical models are difficult to establish, the strategy has good robustness and stability. The scene with actual situation and the operational experience, proposed an expert system to determine the optimum angle between the heliostat normal and the sunlight. We will apply the control system to the solar power tower in Yanqing. In base of the Control Builder AC800F system and AC500 Programmable Logic Control, we developed a control system of solar power tower. The operation results demonstrate that some of the controlling ways can realize the expected target, and all of this has a good application prospect. The practicality can be a valuable reference to the future of designing of solar power tower.