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In a photovoltaic–thermal (PVT) solar collector, a small percentage of the absorbed solar radiation can be converted into electricity and the rest become heat. The heat could be collected through various working mediums. It is of great practical significance to study PVT system and improve its performance further. In this study, an experimental PVT system using MPCM (Microencapsulated Phase Change Material) slurry as the cooling medium was designed and established. The comprehensive performance of the PVT system was studied. The measured electrical and thermal efficiency of the PVT system using MPCM slurry or tap water under various conditions were compared. Moreover, the MPCM slurry was also used as the working fluid in an outdoor PVT system. The practical performance was compared with those of a traditional water-cooled PVT system and a similar system with PCM layer. The results showed that increasing the flow rates of the MPCM slurry could reduce the temperature of PV cell and improve the thermal and electrical efficiency. The performance of the present PVT system using MPCM slurry is better than that using pure tap water or water with a PCM layer. The average electrical efficiency and the maximum thermal efficiency of the system can effectively increase by 0.8% and 13.5% respectively. The slurry containing low concentration MPCM could enhance the performance, indicating the feasibility of the actual application in solar PVT system.

PV windows provide thermal insulation, daylight use and power generation simultaneously. Present investigation aimed to evaluate the energy performance of 3 types of PV windows under 5 climates of China, and particularly to clarify the influences of transmittance and orientation on its energy performance. The present work involves: (i)the experimental testing that had been carried out; (ii)validation of the EnergyPlus model of natural ventilated double PV (NVDPV) window; (iii) prediction of the energy performance of the 5 PV windows under typical climates of China based on the validated model; (iv) applicability discussion of the PV windows under different climates and influence of transmittance and orientation. The results reveal the highest energy saving rate obtained by NVDPV window in the 5 cities. The NVDPV window integrated PV glass with transmittance of 10% delivered better energy performance than the window with transmittance of 5% under climates of Harbin, Beijing, Shanghai and Shenzhen. The south facing windows achieved least building electricity consumption under the climates of Harbin, Beijing, Shanghai, and Lhasa. Exceptionally, the east facing windows achieved least electricity usage under the climate of Shenzhen. The achievements from the present work provide a reliable criterion for the optimized design of PV windows.

The NOx emission of gas turbine is a key factor of air pollution. It is still a challenge to realize low-NOx generation for all the gas turbines with diverse types of combustors and operation schemes. In this study, a three-dimensional simulation of the internal flow and combustion in a double-swirler annular combustor of a heavy-duty gas turbine was carried out. The realizable k-e turbulent model and finite rate/eddy dissipation combustion model were employed for the numerical calculation. The effects of the swirl number and temperature of the inlet premixed gas flow on the thermal performance and the relationship between the velocity-temperature field synergy and the thermal NOx formation were investigated on the basis of field synergy principle. The results indicated that the change of the outer swirl number had a greater impact on thermal NOx generation than the change of the inner swirl number. The velocity-temperature field synergy in the combustor became better as the inlet swirl number or the inlet gas temperature increased. This synergy had a correlation with the thermal NOx generation. The formation rate of thermal NOx in the combustor should be controlled with the optimized velocity-temperature field synergy rather than the sole reduction of inlet gas temperature by considering the required thermal uniformity and capacity. The adopted field synergy is a promising concept to evaluate the thermal related performance of combustor. The obtained results on the generation characteristics under various inlet conditions may guide the design and operation of gas turbine combustors.

Phase change material (PCM) has important applications in the field of thermal energy storage due to its characteristic that the temperature is basically unchanged during the endothermic and exothermic processes. At the same time, it helps to achieve heat supply/demand balance and reasonable energy distribution. Nitrates are widely used as mid-temperature phase change material, but they have relatively low phase change latent heat than chlorine salt. In order to get a kind of material with high phase change latent heat, 50 wt% LiNO3–45 wt% NaNO3–5 wt% KCl (LNK) ternary mixed molten salt is prepared with static mixing melting method. Meanwhile, LNK/expanded graphite (EG) composite phase change materials are prepared with ultrasound smashing method. The experimental results show that the addition of KCl changes the performance. The melting temperature of LNK reduces 20.6 °C and its phase change latent heat increases 19.9 J/g, compared with 43 wt% NaNO3–57 wt% LiNO3 binary nitrate mixture. The thermal properties and thermal stability of the materials are tested and analyzed. The experimental results show that both the ternary phase change material and the composite phase change materials have high phase change latent heat and chemical stability. EG has greatly increased the heat conductivity of the composite phase change materials. The thermal conductivity of 85 wt% LNK/15 wt% EG composite phase change material increases by 778% compared to LNK at 20 MPa forming pressure.