For a future carbon-neutral society, it is a great challenge to coordinate between the demand and supply sides of a power grid with high penetration of renewable energy sources. In this paper, a general power distribution system of buildings, namely, PEDF (photovoltaics, energy storage, direct current, flexibility), is proposed to provide an effective solution from the demand side. A PEDF system integrates distributed photovoltaics, energy storages (including traditional and virtual energy storage), and a direct current distribution system into a building to provide flexible services for the external power grid. System topology and control strategies at the grid, building, and device levels are introduced and analyzed. We select representative work about key technologies of the PEDF system in recent years, analyze research focuses, and summarize their major challenges & future opportunities. Then, we introduce three real application cases of the PEDF system. On-site measurement results demonstrate its feasibility and advantages. With the rapid growth of renewable power production and electric vehicles, the PEDF system is a potential and promising approach for large-scale integration of renewable energy in a carbon-neutral future.

The liquid desiccant air-conditioning system is considered as an energy-efficient alternative to the vapor compression system. The dynamic response characteristics of the system under variable cooling load play an important role in the air temperature and humidity control performance of the system. However, the dynamic response characteristics have not been fully revealed in previous studies. Thus, a dynamic model for a heat pump driven liquid desiccant air-conditioning (HPLDAC) system is established to investigate the dynamic response characteristics of the system in this study. Subsequently, experiments were conducted to validate the accuracy of the dynamic model. The simulation results show a good agreement with the experimental data. The simulation results reveal that evaporating water from the solution is a time-consuming process, compared to adding water to the solution. It spends a long time for the HPLDAC system to decrease the high relative humidity of supply air to a low value, which limits the air temperature and humidity control performance of the system. The upper band for the water replenishing value opening (Δφ_up) is a crucial parameter to improve the limitation. When Δφ_up decreases from 1.0% to 0.25%, the time consumed to reduce the supply air relative humidity to the new lower set value can be saved by 30.6%.