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A Chinese research group has developed a novel method to estimate the photovoltaic potential of urban rooftops based not only on the area of ??the roofs, but also on installation parameters and economic feasibility. The novel methodology was demonstrated in Nanjing, eastern China, and was apparently superior to conventional methods in estimating the projected capacity. Researchers from the Nanjing University of Information Science and Technology (China) have proposed a novel method to calculate the solar energy potential of rooftops at the urban scale. While traditional methods largely focus their calculation on the available roof area, the proposed technique is based on installation parameters as well as economic feasibility. “The method assesses the economic viability of suitable rooftop areas for solar PV installation through required energy demand and payback times, and estimates the solar PV power generation potential of urban rooftops based on the placement of solar PV panels,” the team explains. “Few studies have taken into account the actual layout of solar PV installation in assessments of rooftop solar PV potential at the urban scale.” The proposed method consists of four steps. First, an empirical model based on sunshine duration uses three-dimensional data to calculate solar irradiance on building roofs. The second step considers the ideal arrangement of photovoltaic panels, calculating the minimum rectangle that delimits each roof. Next, an algorithm fed by previous scientific literature is used to place as many panels as possible, avoiding obstacles. Safety margins near the edges of the roof are also taken into account. In the third step, the method calculates a threshold for the minimum solar irradiance required for solar panels to be economically viable. The calculation parameters include installation costs, payback time, proportion of electricity sold to the grid, feed-in tariff, electricity price, panel surface area and efficiency. In the fourth and final step, a comparison is made of whether the solar irradiance received by each photovoltaic panel exceeds the solar irradiance threshold. “PV panels with an average solar irradiance below the calculated threshold are excluded,” the group explains. “This process results in the final arrangement of PV panels and the corresponding solar irradiance. The module efficiency of the PV solar panels is then applied to calculate the potential distribution of rooftop PV solar power generation.” To demonstrate the novel technique, a case study was conducted in Nanjing City, eastern China. Various remote sensing data, vector data and meteorological parameters were taken from sources such as AutoNavi map, digital elevation model (DEM), NASA and Nanjing Meteorological Bureau. Longis LR5-72HPH-550 M module was used as a reference for data on price, size and efficiency. “We calculate the solar irradiance threshold by setting the payback period at 10 years to ensure that most solar PV panel locations are economically viable,” the scientists add. “The electricity scenario parameter is set to 1, which means that all solar PV power generation is sold. The price of fully grid-delivered electricity is 0.49 yuan/kWh ($0.07/kWh) in Nanjing. The cost of a solar PV panel is 672 yuan ($94.8). The module efficiency is 21.3%.” According to the results of the new method, the available rooftop area for photovoltaic energy in Nanjing is 122 km2, with a potential of 28.87 TWh of electricity per year. These results could meet 39.85% of the citys electricity demand in 2022, which was 72.45 TWh. Compared with the traditional method of estimating solar photovoltaic potential, the novel technique avoids overestimating the generation potential per unit area by 13.08%. The new tool was presented in “ Evaluating solar photovoltaic potential of buildings based on the installation parameters of photovoltaic modules,” published in Solar Energy . |
