The large-scale application of distributed photovoltaic system is often impeded by the shading effect between buildings and mismatch between the solar power generation and building energy consumption. This paper explores the relationship between urban form and rooftop photovoltaic installation and utilization potential with implications for low-carbon city planning. This study first investigated the influence of the urban form on the installation potential of the solar rooftop photovoltaics for 12 cities across China which covering different solar climate zones. The significant impact of the urban density on the photovoltaic installation potential is only observed in the cities in high latitude areas with medium solar radiation, and the negative impact can be mitigated by reducing the building height differences, which up to 25% improvement can be expected. Then, taking Shenzhen as an example, the influence of the urban form on the photovoltaic power generation utilization was further investigated for residential, commercial and office type of district building energy consumption profiles. It is found that the densely developed urban built-up environment has positive effect on the solar power utilization in which high percentage of the self-consumption ratio is observed. The self-consumption ratio of the residential district which is the lowest can be effectively improved by mixing with office and business buildings. For typical urban form in Shenzhen which the BCR and FAR are 0.35 and 2.5 respectively, if carefully planned, the rooftop photovoltaics can provide 12.6~18.5% of the building energy consumption and 69.8~75% of the solar power can be directly used by the building, which make the rooftop photovoltaics an important clean and economical energy resource for low-carbon city development.

As a transitional layer between the electricity market and prosumers, Virtual Power Plants (VPPs) can effectively integrate distributed resources of prosumers to participate in the electricity market to improve the energy economy for prosumers. This study aggregates distributed resources such as photovoltaics, energy storage, and flexible loads into a VPP within the same community microgrid. A two-layer peer-to-peer (P2P) energy sharing model within and among VPPs is established to consume PV power and construct a stable power supply system. At the VPP-layer, a comprehensive energy management model is created to optimize the scheduling of flexible loads to achieve optimal energy economic performance of the community. At the market-layer, a VPP bidding model is established to organize P2P energy sharing among VPPs. The VPP-layer scheduling provides initial information for the marketlayer to participate in energy sharing, and energy sharing results of the market-layer are fed back to the VPP-layer as boundary conditions for re-scheduling. The energy economy analysis of the proposed system shows that the community's cost is reduced by participating in P2P sharing, and the two-layer interactive mechanism can further reduce the community's cost by increasing the quantity of shared energy in the P2P market, achieving dual technological and economic benefits.