Research On Photovoltaic Thermal Irrigation Water Warming System On Drip Irrigation Head Part

Objective:Adding renewable energy in agricultural production activities is an important new path to increase the yield and quality of economic crops,and an important way to reduce power consumption and carbon emissions.Solar energy is the most promising renewable energy because of its green,pollution-free and easy to use.The irrigation water in northwest China,especially in early spring in Xinjiang,mostly comes from the low melting temperature of alpine ice and snow,which limits the effect of drip irrigation on crop quality and efficiency,and reduces the yield and quality.However,Xinjiang has rich solar and thermal resources.Therefore,in order to effectively improve the temperature of irrigation water,reduce the adverse effects of low temperature irrigation water on crops,and further promote the development of intelligent precision irrigation agriculture,a new type of solar energy equipment is created to help agricultural production.In this study,based on the current photovoltaic photothermal technology with high solar energy conversion efficiency and various conversion forms,a plate-tube photovoltaic photothermal collector was designed,and a photovoltaic photothermal heating system for the first irrigation water under drip irrigation was proposed.However,the performance of the system under different working conditions,the actual operating performance and use efficiency still need further analysis.Methods:In this study,two groups of experiments were carried out by building a test model system of photovoltaic photothermal heating system for the first irrigation water of drip irrigation.Indoor simulation test conditions,through a comprehensive test method,set different mass flow rate,different initial temperature irrigation water and different solar radiation three different factors on the outlet water temperature,heating amplitude,current,voltage,irrigation water heating power,thermal efficiency,photovoltaic module output power,photoelectric efficiency,comprehensive energy efficiency and actual energy efficiency.The outdoor test under the actual working conditions,through the whole day operation system in different growth stages and under different operation strategies to test the system performance.According to the system performance measured by two groups of tests,the feasibility of the system is evaluated by economic benefits,energy saving benefits and environmental benefits.Results:（1）Under the fixed working condition,the outlet water temperature and the heating amplitude were negatively correlated with the mass flow rate.The outlet water temperature and the heating amplitude were up to 20.9°C and 12.5°C,respectively.The photoelectric and photothermal efficiencies were positively correlated with the mass flow rate,with the maximum values of 0.094 and 0.310,respectively.The actual energy efficiency increased first and then decreased,with the maximum value of 0.484.The lower the initial water temperature is,the higher the heat transfer efficiency of the collector is,the greater the warming amplitude is,and the higher the energy index is.However,the increase of mass flow rate makes the warming amplitude of irrigation water at different initial water temperatures tend to be the same,and the variation amplitude of outlet water temperature increases.The higher the solar radiation is,the higher the heating range and the outlet water temperature are.However,the increase of mass flow rate will weaken the improvement effect of solar radiation on the temperature of irrigation water.Photothermal efficiency and photoelectric efficiency are negatively correlated with the solar radiation intensity.When the mass flow rate is less than0.06 kg/（s·m²）,the actual energy efficiency is negatively correlated with the radiation intensity,and when the mass flow rate is greater than 0.07 kg/（s·m²）,the opposite is true.（2）Under the actual outdoor working conditions,the outlet water temperature,warming amplitude,warming power and output power increase first and then decrease in the whole day,and increase first and then decrease in the whole growth period;photothermal efficiency,photoelectric efficiency,comprehensive energy efficiency and actual energy efficiency are just the opposite,the inflection point appears at 14:00.The outlet temperature,heating amplitude and heating power of the dual-cycle mode are higher than those of the single-cycle mode.The performance of photothermal efficiency,photovoltaic module output power,photoelectric efficiency,comprehensive energy efficiency and actual energy efficiency is just the opposite.（3）The life cycle cost of the photovoltaic photothermal heating system for the first irrigation water under drip irrigation is CNY 89.04/m²,LCC is reduced by 17.6%,and coal saving is 26 024.25 kg/m².The emission reductions of CO₂,dust,SO₂ and nitrogen oxides are high.Conclusion:The photovoltaic photothermal heating system of the first irrigation water under drip irrigation has better heating effect and higher energy conversion efficiency for irrigation water under different working conditions.System flow,initial temperature of irrigation water,system running time and strategy are important factors affecting system performance.The system has high economic,energy saving and environmental benefits.