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　　The solar-thermal industry, since the solar water heater development, solar hot water project everybody should also slowly. But maybe a lot of friends may also just know some basic situation, in fact there are many kinds of solar hot water engineering, there are many kinds of, first of all, the main material is a vacuum tube, a tablet. In addition, from the aspects of operation principle of solar energy engineering system and mode to distinguish and can be divided into many different engineering system, using the same material, but different solar hot water engineering operation control system, the result can make a big difference. Here, we according to the present stage in the industry commonly used seven solar hot water engineering system to respectively describes the operation principle and advantages and disadvantages of each system.一、the constant temperature water system

Operation principle: constant temperature water system (see photo) is more widely used solar energy hot water project operation mode, but also fit for large and small solar hot water project. Under the condition of the sun, in the end of the solar collector water add a temperature probe (the water level of tank can use mechanical float ball control also can be used in a controller to control water level sensor).When the water temperature reaches set point inside the solar collector, the controller sends a signal to control open the electromagnetic valve, the cold water has reached a set temperature of hot water in the hot water tank storage and storage; When the water temperature is lower than the set value within solar collector, controller make the electromagnetic valve shut automatically. Such a cycle that store the high temperature of hot water in the water increasing, when the hot water storage in the water level reaches maximum level, system closed, no longer into the water.Advantage: the system is running relatively natural circulation system to produce hot water speed is greatly increased, system operation is controlled by controller, intelligent degree increase, system is relatively stable.Disadvantages: the high heat storage water tank insulation performance, when the hot water storage box temperature reduce and heat storage water tank is full of water, can't make the high temperature of water in the solar collector to continue into the water tank, wasteful. In addition, increase controller and temperature sensor system, equipment maintenance cost.二、Natural circulation system

Natural circulation system (see photo) is the most primitive solar hot water project operation mode, has extensive application at the beginning of the solar energy technology development, currently has been discarded in the large-scale solar thermal engineering.Operation principle: under the condition of the sun light, solar vacuum tube heat heating tube of water, but compared to store the water temperature of hot water box, water temperature difference is bigger. Therefore solar collector water quality smaller lighter, began to slowly rise to high heat storage water tank, and store the water because of the low temperature hot water inside, so quality grow heavy volume, natural water flow within the solar collector at a relatively low back. So continuously circulation, make the hot water storage box of the water temperature gradually raised, but it is a slow process. Store the water level of hot box usually adopts mechanical float ball control.Advantages: simple operation, low investment, less equipment maintenance cost, suitable for stand-alone solar water heater.Weakness: the heat storage water tank must be higher than the solar collector, and the height difference, usually 1 m to 2 m. Store hot water the water temperature in the cabinet more slowly, and there are strict requirements for pipes and slope, should not be made larger, solar hot water engineering (within 30 m2).三、Temperature circulation system

Operation principle: temperature circulation system (see photo), mostly used in large-scale solar thermal engineering. Under the condition of the sun, in the end of the solar collector water and hot water storage box add a temperature sensor, the controller control, temperature control function by setting, when the water temperature inside the solar collector with heat storage water tank in the difference between the water temperature to the set value, the controller starts to move, control start hot water circulating pump, hot water and heat storage water tank of the solar collector in the low temperature water circulation of exchange; When the water temperature in the solar collector with heat storage water tank in the water temperature is lower than the set value, the difference between the controller action, stop the hot water circulating pump; Such a cycle, so that the heat storage water tank water temperature increases.Advantage: the system is running relatively fixed temperature hot water production speed and greatly improve the water system, by using circulating pump, improve heat exchange frequency, you can always keep relatively high, the water temperature of the hot water storage box has greatly increased the utilization of solar energy collector.Disadvantages: increase the hot water circulating pump, system investment costs are relatively high. System maintenance cost also corresponding increase.四、Constant temperature water + temperature circulation system

Operation principle: + water temperature difference and temperature circulation system (see photo), the constant temperature water, make water into the hot water storage box is always a high temperature, when the store the water temperature of hot water in the lower the temperature cycle control system, and the water of the hot water storage box in exchange of the water in the solar collector. To keep the hot water storage temperature for high temperature in the oven, auxiliary heat source can be used at the same time, so it can ensure all-weather hot water production.Advantage: the system can be fully intellectualized, and alone than temperature circulation system greatly reduce operating costs, and maximize the utilization of solar energy collector, the auxiliary heat source can guarantee to supply hot water at any time, without being limited by the weather.Weakness: the system on the function demand is high, high cost of investment, equipment maintenance cost is relatively high.五、Deputy tank water temperature water system

Operation principle: deputy tank water temperature water system (see photo) in innovation on the basis of water and temperature, can be used in the way of 2, 4 typical system. Basic principle with constant temperature water system is consistent, but just water the way change, namely the deputy tank water and tap water advanced, vice water tank, and then water from a pair of the solar collector, water tank under way to agree with constant temperature water system. Advantages: can overcome the problem of the water pressure, to avoid the pressure is too large, the problem of the damaged tank.Disadvantages: investment cost increase, vice water tank size should pass reasonable calculation.六、Constant temperature water rationing
Operation principle: constant temperature water rationing (see photo) is in "+ water temperature difference and temperature circulation system" basis. This kind of system operation mode is not adopted usually in the use of auxiliary heat source. Tap water into the first store hot water tank, water level sensor in water temperature passing through the hot water storage box store hot water tank can be divided into a number of highly area, for the first time to use tap water to the height of a small area, through the "+ water temperature difference and temperature circulation system" to make this a small area of water temperature rise faster, and then the temperature reached set value, the controller open the electromagnetic valve, hot water in the water storage and upgraded to the height of a small area, and then water temperature rise, water again, so cycle, keep the water temperature in a fixed range of water level of the situation to improve the hot water storage box. We call this way fixed temperature water rationing.Advantages: improve the utilization rate of solar collector, water temperature speed is greatly increased, keep the water temperature of the hot water storage box in a fixed range, save the energy.Disadvantages: through concrete data calculation is needed to set the size of the partition.For example, set the temperature of 55 ℃, the minimum temperature 45 ℃, which is first calculated when filled with water in the solar collector volume V, and then calculate the solar collector with water when the water temperature by the heat released by the 45 ℃ to 55 ℃ Q, then calculate the Q (V1) volume of water can make much increased from 15 ℃ to 55 ℃. And then through the volume of the heat storage water tank and V1 to determine the size and number of partitions.七、Fixed temperature piping system
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Operation principle: fixed temperature pipe circulation system (see photo) in the end of the use of hot water heating water add a temperature sensor, automatic detection of water supply at the end of pipe water temperature, when the water temperature below the set temperature, a controller action, control of start-up piping hot water circulating pumps, water in the pipe with heat storage water tank in the water exchange, so that the pipeline of water temperature is not lower than set value, the user turns on the tap is hot water.Advantages: meet the demand of modern 24-hour hot water, can effectively prevent the pipeline was freezing.Disadvantages: increase the initial investment costs, system operation and improve the cost control function.Above are some commonly used several common solar hot water project or system operation mode. Solar project operation of the system is also as people living standard rise, the demand for living hot water is more and more high, thus engineering operation system is also constantly improved.

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