Research On Several Key Issues Of CPV-T

Solar energy has the potential to play an important role in renewable energy. Inrecent year many research has been done in photovaltic and themal （PV/T） toimprove usage efficience. At present most reseach are about total efficiency and thefeasibility of PV/T. Several key issues always ignored because of they are belong todifferent subject. This thesis discusses these issues and do further investigation.PV/T system always adopt low-concentration, different concentration type leadto different optical efficiency. So it’s difficult to find out which method is best. Allconcentrating PV/T system has sun tracking equipment. The tracking accurateinfluences the efficiency. In this thesis the author analysis and compare the influencewith different type concentration in tracking error. Get a conclusion that theparabolic trough reflecter with tube receiver has minimum influence by the trackingerror. Fresnel reflecter has the same influence when the tracking error less than±3°.The tracking error impact on the efficiency of less than15%, and the total energyloss is less than33%. Lens refracter and surface receiver are more sensitive to thetracking error. In a word, the Fresnel reflection system is suitable for PV/T system.Concentrating solar systems always has equipment tracking the sun. It can bedivided into active tracking and passive following. Active tracking is more accuratethan passive following. At present less scholar focus on tracking algorithm and howto realize.Without these theories support the tracking system for PV/T is just testequipment and hard for practical application. In this paper analysis the trackingalgorithm, and use space coordinate system transformation derived the expressionfor altitude angle and azimuth angle with Julian time of day. At the same timeconsidered the affect with right ascension to the solar position. Compared with theexisting formula proved the derivation is correct, and provides an important theoryfor solar position algorithm. From experiment and analysis the maximum error whenconsider the right ascension factors is less than0.5°, azimuth error is less than0.8°,improve the calculation accuracy.Temperature is a significant effect for PV/T system, so cooling and heatexchange systems are very inportant. Traditional researches only concerned with theinlet and outlet temperature and flow rate, never considered about the channel layoutand thermal conductivity. In fact, the channel layout and form always decide thePV/T system efficiency. Because in series PV the temperature distribution the moreuniform the better for PV/T efficiency. In this paper analysis the PV cooling and theheat exchange. Through the flow channel arrangement uniformed the PVtemperature distribution. Through the orthogonal test derived that the channel gapand the corrugated angle is the most obvious effect on heat exchange in corrugatedchannel. During these conclusions optimized the channel structure. Made a kind ofγ-Al₂O₃nano-fluid, test the thermal properties, get the character in heat exchange, and provide original data for later simulation analysis.From PV/T system running in analysis software Trnsys, get a result that the highconcentration without colling system will cause the PV cell temperature raise anddamage itself. But when cooling system work and controlled solar cell temperaturebetween80¹00℃, will achieve ideal electrical and thermal energy output.Research shown that Fresnel reflection concentrator with active tracking PV/Tsystem can save PV cell use, and improve the solar energy utilization. Through thefull year analysis indicate that concentration PV/T system with colling system workin good condition and save PV cell use. The total solar energy utilization efficiencyreaches43.4%.