P2G (power to gas), or electric-to-gas technology, converts electricity into natural gas or hydrogen, stores the resulting gas in a natural gas pipeline or natural gas storage device, converts and stores it during the peak period of renewable energy output, and supplies energy when power is shortage, thereby improving the system's renewable energy consumption capacity.
P2G includes two types in practical applications: electric to hydrogen and electric to natural gas, where electric to hydrogen is the pre-reaction of electric to natural gas.
The basic reaction principle of electro-to-hydrogen is to electrolyze water to produce hydrogen and oxygen. At this stage, the energy conversion efficiency of electrolyzed hydrogen can reach 75% to 85%. The hydrogen produced by electrolyzed water can be directly used in fuel cells, liquefaction or other storage, but the unit energy density of natural gas generated by hydrogen reaction is 4 times that of hydrogen, and hydrogen is difficult to store and transmit, so the method of electric conversion to natural gas is generally used. The principle of electric conversion to natural gas is to use carbon dioxide and hydrogen to react in a high temperature and high pressure environment to form natural gas based on electrolyzing hydrogen. The energy conversion rate of electric to natural gas is 45% to 60%, connecting the natural gas generated by electrolysis to the natural gas pipeline network, and the two-way flow of energy between the electrical network and the natural gas network can be achieved without additional investment.
The research on P2G is very extensive, and there are many corresponding projects and applications. Especially with the rapid increase in the proportion of renewable energy such as wind power, biomass power generation, photovoltaic power generation, some cities have launched empirical experiments to use excess electricity to electrolyze water to generate hydrogen and use hydrogen in various forms. For example, using the residual electricity from wind power and solar power generation to electrolyze hydrogen to create water, and then store the hydrogen in a hydrogen tank. On the contrary, when the power supply is insufficient, the stored hydrogen is used to generate electricity by using the fuel cell, and power and waste heat are used. The development of
P2G provides technical support for large-scale power generation of renewable energy, can indirectly reduce the power generation use of fossils and other fossils, and also promote win-win results for many parties in the energy Internet. In terms of power systems, this technology is a new way to solve the problem of connecting renewable energy to the grid, which is conducive to improving the output of renewable energy; at the same time, natural gas companies can make profits by storing and transmitting natural gas. In terms of social and economic benefits, this technology strengthens the connection between the power system and the natural gas system, helps to achieve coordinated and optimized operation of multi-energy systems and improves economic and social benefits. On the public side, this technology can make full use of green energy, reduce carbon dioxide emissions, and help improve the living environment.
We believe that with the continuous development of science and technology and the establishment and improvement of the carbon emission trading system, the application prospects of P2G will be broader.
This article was scientifically checked by Li Honglian, associate professor of the School of Communications of Beijing University of Information Technology.
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