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The present work investigated a solar assisted heat pump system for drying Chinese wolfberry. The kinetic characteristic was firstly analyzed through a series of lab experiments. It was concluded that the Page model was the most suitable for predicting the heat and mass transfer of the wolfberry. Based on the wolfberry kinetic model, solar collector model and chamber air model, the coupled drying system model was developed. The accuracy of the mathematic model was determined through comparing with the preliminary experimental results. The influence of operating conditions on the thermal and energy performance of the dryer for the different operating mode was discussed. The drying weight of no more than 75 kg may be preferable in the stand-alone solar drying mode, and less than 15 h was needed to be dried. The electric energy consumption in the solar assisted the heat pump drying mode was lower than that in the stand-alone heat pump mode, and it was recommended that about 50 kg of wolfberry to be dried in the solar assisted heat pump system. Compared to the autumn drying, the reduction in the electric energy consumption was around 9.1 kWh during the 11 h summer drying process. The obtained results demonstrated the feasibility of the combined system for drying wolfberry, and also can provide the basic theoretical and experimental data support for the following research. [ABSTRACT FROM AUTHOR]

Highlights • Mathematic model of hybrid solar heating system is built and verified by a rural building in Qinghai province. • Factors such as collector area and insulation layer of wall are discussed to find out the heating characteristic of the system • Operation of the system can keep indoor air temperature about 6°C when ambient temperature is just −7.8°C. • Thermal load of sleeping people can be hold in acceptable level when the beddings insulation value is kept at the value of 4.0clo during night time. Abstract A hybrid solar heating system combining a solar kang subsystem and a solar air heating subsystem for keeping indoor space within thermal comfort level is investigated in this article for the climatic conditions of Qinghai Province (35 °N 96 °E)- China. The main aim of the current research is to study the hybrid heating system's thermal characteristic and the sleeping comfort of occupants in rural buildings. A mathematical model to study the hybrid heating system has been developed and the results have been validated by conducting an experimental study at a building located in Qinghai province. The influence of the different solar thermal collector areas, insulation levels of wall, thermal sensation of the system and different operation strategies have been investigated. It has been observed that the indoor temperature can be improved by up to 6°C when the ambient temperature is −7.8°C (average). By changing the solar collector area from 4 m2 to 8 m2, the kang surface average temperature can be improved from 22°C to 31°C. Thermal load of sleeping can also remain within acceptable levels when the beddings insulation value is maintained at 4.0clo during night time. It has been observed that without auxiliary power, making the kang system work only at night would be more suitable in the experimental condition. [ABSTRACT FROM AUTHOR]

Solar heating should be recommended strongly for domestic buildings in the Qinghai–Tibetan plateau due to the area's high intensity radiation. In this paper, a novel hybrid solar heating system is presented, that includes a solar kang system, a Trombe wall and a direct gain window. The effects of five combined solar heating operation modes on the indoor hourly temperature for one case domestic building located in the Qinghai–Tibetan plateau were investigated by field measurement and numerical simulation. The optimal operation mode for improving the indoor thermal environment was determined. Furthermore, the effectiveness of each operational mode on the east room was quantitatively evaluated and ranked. The results show that the numerical simulation and field experimental results were well agreed, although there were some differences in specific values. In addition, the results it indicated that a solar kang running all days and Trombe wall running daytime played a significant role in improving the indoor thermal temperature. These relevant findings could provide a reference for solar heating system design and indoor thermal comfort improvement for rural domestic buildings in the Qinghai–Tibetan plateau. [ABSTRACT FROM AUTHOR]

Building integrated concentrating photovoltaic window (BICPVW) has been proven to be used in sustainable building transparent envelopes. Unfortunately, the balance between optical and electrical properties is difficult. This paper proposes a building integrated concentrating photovoltaic window coupling luminescent solar concentrator and thermotropic material (LT-BICPVW). The luminescent solar concentrator and thermotropic layer were fabricated by bulk polymerization and glass sandwich structure, respectively. Optical models are built based on the optical properties of optical waveguide and thermotropic layer, and optical simulations are performed with Monte Carlo ray tracing technology. Window prototypes are characterized under controlled indoor experimental conditions. The experiment found that as the temperature of the thermotropic film increased from 30 °C to 42 °C, the solar transmittance of LT-BICPVW decreased by 43.3%, and the maximum output power increased by 25%. Compared with, building integrated concentrating photovoltaic window coupled with thermotropic material (T-BICPVW), the power conversion efficiency was improved by 59% at the termination temperature. The LT-BICPVW system can effectively reduce solar heat gain and avoid glare hazards, while using renewable energy to significantly increase power output. A series of predictions are made using validated optical model and tracking technique to better guide the design of PV windows in actual buildings. • A BICPVW coupling luminescent solar concentrator and thermotropic material. • Dual functions of power generation and sunlight regulation. • PCE improvement of 59% compared to T-BICPVW. ΔT solar reaches a value of 43.3%. • The multi-window combination structure of lower and bilateral distributed PV cells. [ABSTRACT FROM AUTHOR]

• Effect of passive heating renovation on energy poverty alleviation was verified. • Coal consumption and thermal comfort were measured and compared respectively. • Air tightness, thermal defect and indoor air quality were measured and evaluated. • Potential of the passive heating renovation was explored and further optimized. • Affiliated issues for alleviating energy poverty in policy, technology, etc. were discussed. Energy poverty refers to a situation that people cannot access and use energy safely. It is a major challenge for the global energy system because of its negative impacts on household income, health, education, gender equality and environmental conditions. To solve this problem, many countries advocate the development and promotion of passive solar technology, but the effectiveness of them for energy poverty mitigation has not been evidenced. Therefore, based on empirical studies in the rural areas of Qinghai-Tibet Plateau, this paper aims at investigating the effectiveness of passive solar heating renovation to alleviate energy poverty in rural plateau areas. Specifically, this paper compared and analyzed the coal consumption and indoor air quality during the heating period before and after the renovation of a single-storey building. Further, based on the IES-VE numerical simulation, this paper analyzed the impact of building envelope structure performance on indoor air temperature. The results show that after building renovation, the coal consumption during the heating period could be reduced by 97 kg/week, while the indoor average temperature of two bedrooms were increased by 4.8 °C and 1.7 °C respectively. Setting up the coal stove as an auxiliary heating device, can alleviate the defects of insufficient heating of passive solar energy technology, and indoor temperature could be further improved. However, indoor air quality was lowered because of the high PM 2.5 concentration. In contrast, improving envelope performance could further improve the average temperature of two bedrooms and the sunspace to 16.7 °C, 15.9 °C and 15.6 °C, meeting the requirements of indoor space heating. In general, passive solar heating could achieve satisfactory results, but to alleviate energy poverty effectively in rural plateau areas, further attention should be paid to other technical, economic, social and policy issues. [ABSTRACT FROM AUTHOR]