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[Display omitted] Over the last few decades, great deals on ground-source heat pumps (GSHPs) have been broadly addressed. Various systems of GSHP have been employed worldwide for residential and nonresidential buildings due to their attractive advantages of high energy and environmental performance. The present paper aims to review comprehensively the previous investigations concerning the recent technologies of GSHPs. A brief description of GSHPs and their types, such as open and closed loops and vertical and horizontal GSHPs, is presented. The effects of the employed working fluids and the backfill material on the thermal performance of GSHPs are discussed. Various simulation models that describe the boreholes, such as Kelvin's line-source model, the cylindrical-source model, the finite-length line-source method, Eskilson's model, etc., are discussed. Simulation models utilized in the boreholes as one- and two-dimensional, or quasi-three-dimensional, are studied. The thermal resistance in the borehole, considering the properties of grouting materials and the configuration of borehole flow channels, is evaluated. In addition, different applications of GSHPs integrated with solar systems, cooling towers, ice storage systems, and air-conditioning systems are presented. Finally, the sustainable developments, challenges, and future work of GSHPs are introduced. [ABSTRACT FROM AUTHOR]

• Three designs of photovoltaic-based skylights are proposed to save energy in buildings. • The integration of vacuum glazing with photovoltaic skylights is evaluated. • Using a vacuum layer at the backside of the PV layer is favorable for thermal insulation. • Using a vacuum-based PV skylight reduces the total U-value from 6.3 to 1.9 W/m2.K at ASTM. • Using the vacuum layer with the PV-skylight slightly decreases the power generation of the PV. In commercial buildings with large glazing facades, transparent facades and skylights play a considerable impact on energy consumption. In this study, three different photovoltaic (PV) -based skylights are compared to save energy in these buildings. The first skylight uses a vacuum glazing sample as a substrate at the backside of the PV layers. The second design integrates a vacuum glazing layer in front of the PV layers. And lastly, the PV layers are attached to a single layer of glazing with a solar cells covers 25% of the whole area. A 3D thermal model is developed and validated with data from the literature to compare these designs. it is concluded that using a vacuum layer at the backside of the PV layer is favorable for thermal insulation and attains relatively similar power generation to the case without a vacuum layer. In more detail, replacing the single glazing PV skylight with the first skylight design reduces the total U-value of the glazing from 6.3 to 1.9 W/m2.K for a glazing sample with an area of 0.4 m by 0.4 m at ASTM boundary conditions. Furthermore, at received solar irradiance of 1000 W/m2, an ambient temperature of 25 °C, and a wind speed of 1 m/s, replacing the third skylight design with the first skylight design slightly reduced the electricity generation from 37.4 W/m2 to 36.4 W/m2, significantly decreased the heat flux transfer from 91.1 W/m2 to 50.5 W/m2 and lowers the indoor surface temperature from 32.1 °C to 27.1 °C. [ABSTRACT FROM AUTHOR]