Mitigation of shady-sunny slopes effect on subgrade by photovoltaic sheltered boards in permafrost regions

Abstract

With the great demand of global carbon reduction, a novel method, such as photovoltaic shelter board (PSB), is proposed to mitigate the shady-sunny slope effects in permafrost. The idea of PSB is an extension of traditional shelter board, which can potentially eliminate the shady-sunny slope effect in theory. However, its quantitative performance is still unclear due to limited application and research. To overcome this gap and explore the application possibilities of PSB in cold regions, this paper introduces a novel photovoltaic sheltered board subgrade and numerically investigates its effectiveness in mitigating the shady-sunny slope effect. Initially, a heat transfer model incorporating solar radiation and air convection was developed and validated with field-monitored ground temperature data. Analyses based on this model compare the thermal imbalance effects on exposed subgrade, traditional insulation boards subgrade, and the novel photovoltaic sheltered board subgrade. Results indicate that the photovoltaic sheltered board exhibits superior mitigation effects to traditional insulation boards, primarily due to enhanced heat dissipation by air convection in the suspension region. In the study area, the photovoltaic sheltered board significantly lowers sunny slope temperatures by over 3 ℃ on average and thaw depth by more than 1m compared to exposed subgrade. The photovoltaic sheltered board’s suspension height should not be less than 5.3cm to mitigate the sunny-shady slope effect effectively in this region. In summary, this study provides a reference for mitigating the shady-sunny slope effects and reducing carbon release in permafrost subgrade engineering.