Study On The Small-scale Brackish Water Desalination System Driven By Combined Wind And Solar Power

Freshwater resources are important life resources extremely, however, a quarter of the population are also facing the shortage of fresh water supply in the world at present, which is the most prominent in the various provinces in northwest of China.Though the brackish water desalination is the effective method to solve human water shortages, the traditional desalination technology needs lots of fossil energy and power, which is the typical way with non-renewable energy in exchange for water, moreover, most of the fresh water shortage regions are remote or island regions where lack of energy resources relatively, the transportation, the power also very inconvenience, the obtain of freshwater resources can not consume at the cost of non-renewable resources. According to energy distribution and energy utilization in our country's northwest, the desalination system which drive by wind and solar united is put forward in this paper, and organic combine with solar technology, wind energy and traditional desalination system, the physical model and mathematical model also established; based on the design goal of system, the design calculation of selection is made for system; the thermodynamics model is established which based on the first law of thermodynamics and the second law, and make energy analysis and exergy analysis; then, the economic performance and ecological benefits evaluation is analysed.Firstly, the principle of desalination system drive by wind and solar united is introduced, and physical model and mathematical model of the system is established; Then, take the design calculation for each parts of a small desalination equipment system based on system model, finally, thermal performance analysis and economic performance analysis are made for this system. The research content and results of this topic are as follows:1. Based on the principle of horizontal pipe falling film evaporation, the desalination system which drive by wind and solar united is put forward in this paper, and organic combine with solar technology, wind energy and traditional desalination system, and mathematical model of evaporator, condenser and of the solar collectors are established.2. According to the design goal of system, the design calculation of selection is made for system, which based on the first law of thermodynamics and the second law.3. Based on the mathematical model, the evaluation index are set up, which include the water yield produced daily, unit heat consumption rate of freshwater, system performance factor (COP), exergy efficiency and thermodynamic properties, the thermal performance of the system is analyzed based on the first law of thermodynamics and the second law of thermodynamics, the influence of the solar radiation to freshwater production and heat consumption rate was obtained. The research shows that:This system can have a continuous freshwater output from January to December with the condition of solar radiation in Lanzhou area, and daily freshwater production has same change trend with the radiation; in May, June, July and August which the solar radiation is better, the water production rate of this system is very high, the highest water production rate of this system may achieve 2.0kg/m2·h, but the concentration factor is also very high. In this four months, increased spray appropriately can reduce the amount of scaling formation, and freshwater production can also increase. The coefficient of performance of the system in most of the month is over 0.5, we can see the effects of system operating in most of the month are better. From the exergy analysis of the black box model, we can find that system thermodynamics sophistication is 34.7% and the system still has much space for improvement. From the exergy analysis of gray box model, we can find that the system exergy losses mainly occurred in the evaporator and the key of enhance the system efficiency is exploiting the high-efficient evaporator.4. Using the method of dynamic economic to appraise the entire system.The results showed that the four evaluation indices, include the net present value, benefit, the internal returns ratio and the investment Recovery period are in line with the requirements. The promotion of this set of devices can generate good value for money, with good prospect of application and extension.5. The emission of carbon dioxide is analyzed, and the device has good ecological benefits and environment friendly degrees.The innovations and significance of this topic: The desalination system drive by wind and solar united, which is a set of minitype, stable, environmental protection for single family use, and drive running by renewable energy completely, this is a new design thought of desalination system which still had been done in the domestic and international.The seawater and brackish water underground are distribute abroad in our country; Most of the region in China, the status quo of drinking water is shallow or the water in deep wells where the fluorine content is high, which is harm for people's health if have long-term drinking; to take fresh water from the ocean, also becomes consensus of the world's coastal states. The desalination system aimed at combining human,financial resources and natural conditions of northwest, to realize ascension from low grade by solar thermal energy to high quality, low cost, no pollution and sustainable freshwater supply. In addition, this device can be applied to industrial technology of these areas completely, and have effective and stable for water yield, and good water quality.