The external characteristics of solar cells, from the perspective of application, the main concern is the external characteristics of solar cells. First of all, for a single solar cell, it is a PN knot, except when the sun shines on it, it can produce electricity, it also has all the characteristics of PN knot. Under standard illumination conditions, its rated output voltage is 0.48V. Solar panels are made up of a number of solar cell connections in the use of photovoltaic lighting fixtures. It has a negative temperature coefficient, every rise in temperature, voltage drop 2mV, for a number of solar cells composed of solar modules, this is a problem can not be ignored.
2 solar cells in the use of lamps must pay attention to the problem
2.1 Solar cell Power selection, we call the solar cell output power WP is standard solar illumination conditions, namely: the European Commission defined 101 standards, radiation intensity 1000w/m2, atmospheric quality AM1.5, battery temperature 25 ℃ conditions, solar cell output power. The condition is approximately the same as that of the sun before and after noon, (only near the lower reaches of the Yangtze River) This is not as some people imagine, as long as the sun will have a rated output power, even the solar cells in the night fluorescent light can also be used normally. This means that the output power of the solar cells is random, at different times, at different locations, the same solar cell output power is different. Table 1 is the solar illumination condition in different regions of China in order to more intuitively understand the average distribution of solar radiation every day, table 2 gives the corresponding relation between annual total radiation and daily average peak sunshine time (solar cell can receive the equivalent time of 1000w/m2 irradiance daily). Table 2 The total amount of radiation and daily average peak sunshine time corresponding table, through the above data can be seen, the design of solar lamps and lamps used in the area concerned. The relationship between the rated output power of solar cells and the input power of luminaires in east China is about $number: 1, the specific proportion according to the daily working hours of lamps and lighting requirements for continuous rainy days. In addition the output power of the solar cell is about 120w/m2.
2.2 Storage capacity of the battery because the input energy of solar photovoltaic system is very unstable, the general need to configure the battery system to work, solar lamps are no exception, the battery must be configured to work. There are lead-acid batteries, NI-CD batteries, ni-h batteries, their capacity selection directly affects the reliability of the system and the system price. The selection of battery capacity generally follows the following principles: first of all, in order to meet the night lighting, the energy of the day solar modules stored as far as possible, but also to meet the continuous rainy night lighting needs of electricity. Battery capacity too small can not meet the needs of night lighting, battery capacity is too large, on the one hand, the battery is always in a state of power loss, affecting the battery life, while causing waste.
2.3 Solar cell package in the form of choice, the current solar cell packaging form mainly 2 kinds, lamination and epoxy, laminating process can ensure that the solar cell working life of more than 25 years, the drop gum although beautiful, but the solar cell working life is only 1-2 years. Therefore, 1 W below the small-power solar lawn lamp, in the absence of high life requirements, can be used in the form of drip-gum packaging, for the use of solar energy lamps, the proposed use of laminated packaging form. In addition, a silicone gel is used for epoxy-encapsulated solar cells, which are said to have a working life of up to 10 years.
2.4 Solar cell installation tilt angle of choice and decorative housings, in order to beautiful, many solar lighting factories will be placed in solar cells, in this case, the output power of the solar cells will be reduced $number, if the solar cell is added a decorative housing, the output power of solar cells will be reduced by about 5%, solar cell prices are expensive, we have collected a lot of foreign solar lamp data, in the beauty and energy-saving, most of the choice of energy In the lower reaches of the Yangtze River solar cell Ideal tilt angle is about 40 degrees, the direction is positive south.
2.5 Heat island effect, monolithic solar cells are generally not used, the actual application of solar modules. Solar modules are assembled from multiple solar cells to achieve desired voltage values. Solar cell components in the use of the process, if a single solar cell is blocked, such as the leaf guano, alone blocked solar cells in the strong sunlight will be heat damage, so the entire solar cell components damaged. This is called the heat island effect. In order to prevent the heat island effect, it is generally to tilt the solar cells to place, so that leaves can not attach, while the solar module to install a bird-proof needle.
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