**1. Introduction**

Building a resource-conserving society is important after an in-depth study of the history of the political, economic, and social development at home and abroad, in accordance with China's social and economic development, and it is also a scientific plan for China's future social development model. Energy saving is an important part of building a resource-saving society, and as one of the three major sectors of energy consumption, building energy consumption represents about one-third of the energy consumption of the whole society, and is the biggest potential energy-saving area [1].

Energy revolution is the first step to build a resource-saving society, and the fundamental task of energy revolution is to change the energy structure dominated by fossil fuels into a low-carbon energy system dominated by renewable energy, so as to cope with the threat of climate change, reduce China's external dependence on energy, and achieve sustainable energy development. Among the many renewable energy sources, solar energy is focused on because of its unique cleanliness, low cost, high efficiency, and abundant reserves [2].

China has a vast territory, abundant solar energy resources, and huge resource potential. The maximum annual solar radiation in all regions of mainland China is 8364 MJ/m2, the minimum is 3324 MJ/m2, and the average is 5749 MJ/m2; The total annual solar radiation received by the land surface of the country is about 50 × 1018 kJ, which is equivalent to 2.4 × <sup>10</sup><sup>4</sup> million tons of standard coal, which provides a good prerequisite for the utilization of solar energy resources in the country [3]. As a typical technology form of

**Citation:** Zhang, W.; Zhao, Y.; Huang, F.; Zhong, Y.; Zhou, J. Forecasting the Energy and Economic Benefits of Photovoltaic Technology in China's Rural Areas. *Sustainability* **2021**, *13*, 8408. https://doi.org/ 10.3390/su13158408

Academic Editor: Carlos Morón Fernández

Received: 22 June 2021 Accepted: 23 July 2021 Published: 28 July 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

solar energy application, photovoltaic (PV) power generation uses the photovoltaic effect to directly convert solar radiation energy into electric energy, which is one of the most promising renewable energy technologies to realize sustainable development, and it is also a means to realize zero energy building [4]. At the same time, PV power generation, as a solution to the increasing demand for electricity, can also minimize environmental and social problems related to fossil fuels and nuclear fuels [5]. Driven by energy and environmental benefits, PV systems have developed rapidly in recent years, with an average annual growth rate approaching 50%, and have begun to gradually replace coal-fired power generation. With the advancement of technology and the increase in market demand, solar power generation has formed two more mature power generation models—centralized and distributed. Compared with the distributed PV power generation system, the centralized PV system has a relatively early development and mature technology, and its proportion in the cumulative installed capacity is higher than that of the distributed PV system [6]. In 2017, the new installed capacity of China's centralized PV power generation system reached 33.49 GW. In contrast, from 2013 to 2016, the cumulative installed capacity of the distributed PV power generation accounted for only 15% to 20% of the total PV power generation. However, in recent years, distributed PV systems have received more and more attention because of their unique advantages over remote large-scale centralized PV power plants. Its main advantages include being able to be installed on the roof near the electricity consumption area so as to obtain a lower transmission cost and power loss [7,8]. The new capacity of the distributed PV system increased significantly from 4.26 GW in 2016 to 19.44 GW in 2017, which shows the huge development potential of distributed systems [9].

There are considerable solar resources on roofs, which are also convenient for the installation of PV systems. Therefore, PV roofs have become one of the main application forms of distributed PV systems. Vardimon R et al. [10] used a complete set of GIS data covering the whole country to evaluate the available PV roof area in Israel. There are also some studies on the calculation and analysis of the roof PV power generation potential in some areas such as the United States and Austria [11,12]. In addition, Fina B [13], Senatla M [14], and Miranda R F C [15] et al. also analyzed the economic potential of rooftop PV systems in Australia, South Africa, and Brazil, respectively. However, with the rapid development of the urban economy, land value in urban areas is getting higher and higher, and there are more high-rise buildings. For high-rise buildings in urban areas, the roof area is very limited, and the area of PV systems that can be installed is also very limited. In rural areas, because the building density is smaller than in cities, and it is mostly one-story or two-story buildings, more roof area can be used to install PV systems, so there is a greater application potential for PV systems. Especially in Xinjiang, Inner Mongolia, Qinghai, Tibet, Ningxia, Gansu, Yunnan, and remote mountainous areas, where power is scarce, power transmission costs are high, but solar energy resources are abundant and land costs are low. Moreover, with the deepening of the country's new rural construction and PV precise poverty alleviation policies, the PV power generation industry has developed rapidly in the countryside, so these areas have great potential for installing PV power generation systems. On the other hand, because of the wide range of rural areas, the rural distribution network generally consists of a simple radiation chain structure, with a scattered power load, long distribution distance, and relatively unstable power supply quality. Using the performance characteristics of PV power generation, applying distributed PV power generation to rural areas according to local conditions can not only solve the impact of rural grid voltage instability, three-phase imbalance, and other problems, thus solving the power demand of rural users, but also promotes the high-quality development of the PV industry [16].

China is committed to "peak carbon dioxide emissions" and "carbon neutrality" in the future. Photovoltaic is considered to be one of the main energy situations in the future. The distributed photovoltaic system combined with buildings has many advantages, and is considered to be one of the important technical solutions to achieve "peak carbon dioxide emissions" and "carbon neutrality" in the future. At present, China needs to

calculate the installed capacity and power generation that can be achieved by building integrated distributed photovoltaics. In this way, the relevant institutions can develop policies to improve data support and help. Recently, a number of provinces in China have formulated the building roof photovoltaic installation plans of cities and counties [17–21]. The calculation of the PV installed capacity in China's provinces in this study can provide assistance for the implementation of the plan.

#### **2. Methodology**

Firstly, this research analyzes the building types and converts the rural building area into the roof area. Then, the roof area is converted into the installation area of the PV modules, which can be used for power generation by considering influencing factors such as the optimal installation angle, installation spacing, roof slope, and surrounding environment. Then, according to the solar radiation data of different regions and the current PV module parameters and other data, we calculate the solar power generation potential, that is, energy efficiency. Finally, we calculate and analyze the economic benefits of the construction of distributed PV systems in rural areas under the relevant policies and measures of China. An overview of the methods used in this study is shown in Figure 1.

**Figure 1.** Overview of the methods used in the research.

### **3. Calculation of PV Module Power Generation Area**

#### *3.1. The Annual Solar Radiation*

Because of the vast land area in China, the solar radiation intensity also varies greatly in different regions. Therefore, in the calculation process, we first divided China into several sub regions (in each partition, the intensity of solar radiation is roughly the same) according to the annual total solar radiation level, and on this basis, the installed capacity and annual power generation of PV modules in each zone were calculated. In the process of regional division, we first divided different provinces into different regions, and then divided each province into several regions with different radiation levels according to the difference of total solar radiation in each province. The annual solar radiation intensity of typical cities in each radiation area was selected as the annual total radiation calculation data of the whole area.

As shown in Figure 2, taking Jiangxi Province and Gansu Province as examples, there was no significant difference in the solar radiation intensity of each city in Jiangxi Province. The annual solar radiation amount was about 5400 MJ/m2. Therefore, as an irradiated area, Jiangxi Province was no longer divided internally, and Ganzhou was taken as a typical city for calculation. In addition, the solar radiation resources in Gansu Province

could be roughly divided into the following three areas: rich area, relatively rich area, and available area. The solar-rich areas included Jiuquan, Zhangye, and Jiayuguan in the Hexi corridor. The total annual solar radiation of the whole area is more than 6100 MJ/m2, and the solar energy resources are stable. Jiuquan is regarded as a typical city in this area; solar energy resources are relatively rich in certain areas, including Jinchang, Wuwei, Minqin, Gulang, Tianzhu, Jingyuan, Jingtai, and Dingxi, Lanzhou, and Linxia. The total annual solar radiation in this area was between 5400~6100 MJ/m2, and Minqin was selected as a typical city. The available areas included Tianshui, Longnan, and Gannan. The total solar radiation was between 4700~5400 MJ/m2. Lanzhou City was used as a typical city in this area.

**Figure 2.** The solar radiation intensity distribution: (**a**) Jiangxi Province and (**b**) Gansu Province.

The annual total solar radiation data for each typical city came from the China Meteorological Data Network, and the main data come from the "Daily Data Set of Meteorological Radiation Basic Elements in China". The observation data collected in this data set include total radiation, scattered radiation, direct radiation, and net total radiation. The data used in this paper are the annual total radiation data of the radiation measurement stations in typical cities of each province, with the unit of MJ/m2.
