17-05-2013, 04:41 PM
The Optimum Sizing of Stand-Alone Photovoltaic Systems The Optimum Sizing of Stand-Alone Photovoltaic Systems
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Abstract
Stand-alone photovoltaicsystems should be of optimum sizing. Abstract: Stand-alone photovoltaicsystems should be of optimum sizing. This article introduces a concise,rational and practice-cal method. This article introduces a concise, rational and practice-cal method. The method adopts the calculating formula currently used abroad for determining the solar radiation on tilted surface. The method adopts the calculating formula currently used abroad for determining the solar radiation on tilted surface. According to the days of autonomy and the principle of energy equilibrium,the optimum tilt angle of photovoltaic arrays obtained first and then a series of capacity combinations of photovoltaic array and battery by means of cycle calculations. According to the days of autonomy and the principle of energy equilibrium, the optimum tilt angle of photovoltaic arrays obtained first and then a series of capacity combinations of photovoltaic array and battery by means of cycle calculations. The size of photovoltaic systems is finally determined after further economic accounting. The size of photovoltaic systems is finally determined after further economic accounting. Relevant computer program is worked outland a calculated example presented. Relevant computer program is worked outland a calculated example presented.
Introduction
In recent years, solar energy (also known as PV) power generation has been rapid development in China's photovoltaic systems and a variety of applications are emerging, encouraging an unprecedented situation. But a little analysis can be seen that a lot of products that have not been carefully optimized design, and some products are Zhaomaohuahu, incorrectly relay an erroneous message; some of them do not comply with the basic law of photovoltaic power generation and the characteristics of the work, so that does not guarantee Long-term, stable and reliable operation, or excessive capacity allocation, resulting in a large number of waste, affecting the application of photovoltaic power.
At this stage, the price of solar cells was also higher, photovoltaic system should be based on the load requirements of the local meteorological and geographical conditions to optimize the design, through the scientific method, reliability and economy to achieve the best combination However, because of the photovoltaic power generation system is running involves a lot of factors, the complex relationship between the design is very difficult to calculate. Some of the design is not very complicated, is not perfect. We work in the past on the basis of [1], so further amended and improved, summed up simple, reasonable and practical methods to optimize the design.
technology
nature of the load
Independent photovoltaic system means that no auxiliary power, photovoltaic power is the only source of the power system.
Actual load and the size of the possible use of the ever-changing from day to use up time distinction can be divided into daytime, evening and night of the three day load. For only the use of the load during the day, most can be directly powered by photovoltaic systems, due to a decrease of battery charging and discharging caused by wear and tear and so on, with the photovoltaic system capacity can be reduced. All night the use of its load of photovoltaic systems with the capacity necessary to increase accordingly. Even during the day and night, the load capacity is needed between the two. In addition, from time to use up the whole year distinction, can be divided into more or less balance the load, seasonal load and load random. To simplify, the average monthly changes in the power of not more than 10% of the load can have the same power as the average balance of the load [2]. This article discussed only for the balance of power load-independent photovoltaic systems to optimize the design.
The factors to consider
The impact of photovoltaic systems running a number of factors, the relationship is very complex, and some books even listed dozens of correction factor. In fact because the on-site conditions and the ever-changing operation, can not advance one by one to determine the size, and there is absolutely no need to distinguish between so meticulous, can be a small amount into a number of the necessary correction factor, may also need to add a certain safety factor to deal with.
The amount of solar radiation
Due to the randomness of solar radiation can not be determined after the installation of photovoltaic systems square on the surface of the sun every time the exact amount of radiation can only be based on the historical record of weather data as a reference. However, it is usually provided by the meteorological stations are level on the surface of the sun radiation, needs to be converted into a square tilted on the surface of the radiation exposure. For the average photovoltaic system, as long as the calculation of the surface of the tilt on the average amount of solar radiation can, and do not have to consider the transient (usually by an hour) solar radiation flux. Order to level the surface on the average amount of solar radiation converted into tilt on the surface of the average amount of sun exposure, many people Liu has also been applied in Jordan and in 1962 made the calculation [3, 4]. Although this method is relatively simple calculation, but in reality only a year in the sun two points (March and September at the spring and autumn) is correct. This method is used to tilt toward the equator on the surface of the average amount of radiation scattering of small results.
square dip
Fixed-square photovoltaic, as far as possible tilt towards the installation of the equator, the first increase this year to receive the amount of solar radiation, the surface of the square can also enhance the winter sun exposure, while at the same time to reduce the summer Radiation exposure. This battery for energy storage device to an independent photovoltaic system is very important. Now, there is a lot of Solar Garden Light, and other types of solar photovoltaic products using standard installation, the capacity of these products will be tight, but should not be used to install level.
Conclusion
independent photovoltaic systems must be optimized design, considering the reliability and economic indicators, to determine the best end-square solar cells and battery capacity of the portfolio.
Tilt on the surface of calculating the average amount of solar radiation, could be Klien and Theilacker proposed by the method of calculation.
Square the best angle in accordance with the nature of the load, the local meteorological and geographical conditions, as well as to meet the battery to maintain the number of days in different conditions, such as change, by comparing the different angles when they meet the minimum requirements of load capacity to determine the configuration. Usually for a different battery to maintain the number of days, the square is not necessarily the same as the best angle.