Off-grid power generation system consists of solar panels, battery and charge and discharge controller, and an off-grid inverter, solar controller (pv controller and scenery complementary controller) to adjust and control of all electricity. On the one hand, the adjusted energy is sent to the DC load or the alternating current load, and on the other hand, the excess energy is sent to the storage battery. when all electricity can not meet the needs of the load, the controller sends the battery energy to the load. When the battery is fully charged, the controller controls that the battery is not overcharged. When the power stored in the battery is exhausted, the controller should control the battery not to be over-discharged and protect the battery.
Grid generation system is photovoltaic arrays, wind turbines and fuel cells will produce renewable energy without a battery energy storage, reverse feed into the grid directly by grid inverter power system. Because the electricity can be input directly into the power grid, the storage battery is eliminated, the storage and release process of the battery is eliminated, and the power produced by the renewable energy can be fully utilized to reduce the energy loss and the system cost. The grid-connected power generation system can use municipal power and renewable energy as the power source of local ac load in parallel to reduce the load power shortage rate of the whole system. At the same time, the renewable energy grid-connected system can regulate the peak of the public power grid. Grid-connected power generation system is the development direction of solar and wind power generation, which represents the most attractive energy utilization technology in the 21st century.
In the photovoltaic off-grid system and photovoltaic grid-connected system, we compare the following aspects:
In the off-grid system, batteries and solar charge and discharge controllers need to be adopted, which increases the cost.
The service life of the battery is generally about 5 years (with the different depth of charge and discharge, the life of the battery is different. Under the condition of daily charge and discharge, the battery life is generally not more than 3-5 years). This is a great investment when replacing the battery, and it also needs to be maintained regularly, and the workload is increased.
We tested the same component of the battery in both off-grid and grid-connected systems, and the tests showed that the system would be relatively efficient.
1. The grid system is used in the equipment design are carried out in accordance with the normal work for 25 years, and the equipment design life is generally in the off-grid system for 8 to 10 years, even in a relatively short operation time, also differ in terms of reliability;
2. There are many off-grid system components, and the fault points increase correspondingly, which reduces the reliability, and the performance of the battery will decrease with the use.
3. Although mains complementary system can improve the system or the reliability of the fault cases in rainy weather, but the switch\'s impact on the load and the device itself is also the important cause of system failure;
4. Grid pv system without any energy storage and switching unit, power is by the system automatically allocate, and equipment for automatic control work in the best condition to run, stable performance and high reliability.
In order to monitor the state and efficiency of the system, a DC meter is connected to the DC output end of the solar cell array and an AC meter is connected to the output end of the inverter. The monitoring software is compiled to monitor the DC and AC tables, because the frequency of the ammeter is relatively high and is not well achieved in the software writing. So high frequency, meter box display system accuracy is also different, display data will be different from the data displayed by the meter, so the monitoring and display software is a gross estimation. The grid-connected inverter integrates the rs-485 and Ethernet communication interfaces, and transfers data to the computer through the 485/232 converter for easy viewing and operation. Monitoring system to monitor and display of the following parameters: the solar cell array voltage and current, ac output voltage and current, the current power, the power generation, the cumulative power generation, solar radiation, solar panels power parameters such as temperature, ambient temperature, and show the data such as carbon dioxide and fault state.
Compared with conventional energy, solar power has the following advantages:
1. Solar energy is inexhaustible and inexhaustible, and solar energy will not cause environmental pollution in the process of transformation;
2. Solar power generation is a static operation, without moving parts, it has a long life and requires little or no maintenance;
But relatively grid pv system, off-grid photovoltaic systems need to use to produce electricity for storage battery, and extensive use of raw materials - metal lead battery, and battery life is relatively short, waste will cause serious pollution to environment.
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