Rural rooftop photovoltaic-a breakthrough to achieve low-carbon development
【Environmental Protection Talk】
"Strive to reach the peak of carbon dioxide emissions before 2030, and strive to achieve carbon neutrality by 2060" is our country's goal and commitment.
To achieve the dual-carbon goal, its central task is to replace the current fossil-based carbon-based energy with zero-carbon energy based on renewable electricity.
It is foreseeable that wind power and photovoltaics will be the most important power sources in the future renewable power system. In the future power system, the capacity will account for more than 80%, and the power generation will account for about 60%.
However, there are still difficulties in developing wind power and photovoltaic power in my country.
One is the installation space.
According to calculations, 100 million mu of land is needed to add 6 billion kilowatts of wind power and photovoltaic installations.
The second is effective consumption.
Unlike thermal power, wind power and photovoltaics are not easy to control, and their changes are inconsistent with electricity demand. How to coordinate the relationship between power and electrical load so as to effectively absorb its power generation is the key to the development of wind power and photovoltaics.
In contrast, my country’s vast rural areas have strong energy demand, but there is a large room for carbon reduction and coal reduction, and the transition to clean energy is urgently needed.
Relevant data shows that in 2019, my country's rural scattered coal consumption was about 140 million tons, accounting for more than 90% of the country's non-industrial scattered coal, and it was one of the focus of coal and carbon reduction.
The direct combustion of coal, diesel, and straw as the main energy sources has also become an important cause of environmental pollution such as the atmosphere.
Combining the above two factors, the author believes that the construction of a new rural energy system based on rooftop photovoltaics in rural my country may become an effective way to solve the plight of wind power photovoltaic development and promote rural economic and social development.
What is a new rural energy system based on rooftop photovoltaic?
That is, in areas where natural conditions are suitable, make full use of the idle roof space of various farmers, develop a new type of DC micro-grid with photovoltaic power generation as the core, and provide comprehensive energy for rural production and life.
At the same time, surplus electricity and processed or gasified biomass energy can be exported to cities, becoming a new economic source for grain-producing areas.
According to calculations, if each household’s roof is installed with more than 20 kilowatts of photovoltaics, the annual power generation can exceed 20,000 kWh, which can meet all the domestic electricity consumption of a household including winter heating (50 square meters of main room heating) and cooking. It can be charged with all kinds of vehicles, and there are still nearly 10,000 kilowatt-hours of electricity left for agricultural production and processing of agricultural and sideline products. The remaining electricity can also be connected to the Internet at a suitable time.
In addition, through the construction of village-level DC micro-grids and public storage batteries, the mutual circulation and supplement of electricity between households can also be realized.
In rural areas, various electric devices with storage capacity and most loads can respond to electricity consumption patterns according to demand, so that most of the rooftop photovoltaic power is effectively consumed. The remaining part is connected to the Internet after the integration of the village-level DC microgrid. Transform into an adjustable and controllable high-quality power supply.
Under such a model, the new rural energy system will realize the full electrification of production, life and transportation energy, and the rural atmospheric environment is expected to be completely improved.
From the perspective of construction costs, the above configuration includes village-level public parts. Each household is equivalent to an investment of about 100,000 yuan. The annual income from public electricity and Internet transmission can not only pay the operation and maintenance management fee, but also realize the installment of all initial investment. Repayment of debt and interest, so that all farmers' households use electricity for free.
At the same time, the source of engineering investment can be solved through low-interest bank loans.
So, how many rural roofs can be used in our country?
According to a cooperative survey calculation between Tsinghua University and the Satellite Information Institute of the former Ministry of Land and Resources, about 2 billion kilowatts of photovoltaic power generation devices can be installed on various roofs in my country’s rural areas. 40% of the total annual electricity consumption will reach 60% of the total photovoltaic power generation in my country's planned zero-carbon power system.
In the future, with the progress of urbanization, my country’s rural population may decline, but the scale of rural buildings and roofs will not decrease, and the scale of photovoltaic installations will also stabilize at this level.
It can be seen that rural rooftop photovoltaics can play an important role in the future zero-carbon power system in terms of power supply and capacity adjustment. In addition to meeting the energy consumption of rural production, life and transportation, it can also provide capacity for the grid. The adjustable power supply of 800 million kilowatts and 1 trillion kilowatt-hours of electricity is helpful to realize the flexibility and stability of the power system.
Therefore, the development of a new energy system based on rural rooftop photovoltaic as soon as possible is not only conducive to rural revitalization, but also plays a vital role in building a new power system based on new energy and achieving zero carbon in electricity as soon as possible.
It needs to be emphasized that under the guidance of the goal of "carbon peak and carbon neutrality", the construction of a new rural energy system based on rooftop photovoltaics will also become a breakthrough in the construction of my country's new power system.
The low-carbon transformation of the energy system will promote a series of revolutionary changes in my country’s existing power system—power will shift from centralized to a combination of centralized and distributed; the power grid will shift from the current one-way power receiving to two-way active power; the relationship between power supply and demand will change from The current "source varies with load" has changed to "load varies with source"; the stability of the power grid has changed from relying on the inertia of centralized power sources to relying on distributed power storage.
These changes are not only related to basic research and technological research and development, but also to the adjustment of power policies and pricing mechanisms. It also requires the adaptation of electricity usage patterns and the establishment of a new electricity usage culture.
Completing the construction of a new power system under the premise of ensuring power safety, social stability and sustainable economic development will be a revolution in power technology and power culture that needs to be explored in depth.
For the rural areas in central and eastern my country, the construction of the current power system is still relatively backward, and the capacity expansion and transformation of the rural power grid is being planned and underway.
The author believes that if the power system in these areas is re-planned according to a rooftop photovoltaic-based model, the funds for capacity expansion and transformation can be used to invest in this new method of transformation, or it may reduce the financial pressure on rooftop photovoltaic system construction.
At the same time, the transformation from a centralized power system to a distributed power system will not cause too much interference to rural economic and social activities.
Since the electricity market in rural areas only accounts for a small proportion of my country’s electricity market, the reform of electricity policies and mechanisms that correspond to the new power system will be piloted in rural areas and will not have an impact on the entire electricity market. Therefore, in this area The exploration and experimentation will possibly provide a reference for the subsequent reform of the power system.
In this way, the construction of a new rural energy system based on rooftop photovoltaics may be a breakthrough in the construction of a new power system in my country.
This is not only an important part of building a new socialist countryside and implementing the strategy of rural revitalization, it is also expected to be the first step that can be taken to realize my country's low-carbon development and complete the power system revolution.
(Author: Jiang Yi and Hu Shan, academicians of the Chinese Academy of Engineering, director of the Research Center for Building Energy Efficiency of Tsinghua University, and assistant researcher of the Research Center for Building Energy Efficiency of Tsinghua University, respectively)