The structure, problems and trends of China's electric power energy during energy transition

The fourth is to develop renewable energy heating, increase heat storage devices, and increase the flexibility of power plants. Compared with electricity storage, heat storage is technically easier to achieve, and the cost is relatively low.

The fifth is to use energy storage technology on the production side, the power grid side and the user side to improve the flexibility of these links.

At present, in addition to the flexible transformation of coal power units and the high cost of electrochemical energy storage, the remaining four ways are in our country because of various obstacles, either no action or very limited effect, resulting in the flexibility of the current power system is still very poor. Of course, more importantly, over the years, the development of power supplies and grid planning do not match, and thus there is a high proportion of wind power that cannot be connected to the Internet in the initial stage of energy transformation.

Secondly, there is an inherent contradiction between the large scale of thermal power units and the flexibility of power system.

At present, many power policy ideas largely ignore the impact of the energy transition. The most typical is the power industry energy-saving emission reduction and elimination of backward production capacity in the policy has been respected, and has been promoted to other industries on the "pressure on the small" policy. Since then, the standard for shutting down small thermal power units has been continuously improved. At present, it has been required that 200,000 and less kilowatt thermal power units must be closed, and to encourage large units. According to statistics, 600,000-kilowatt and above thermal power units accounted for more than 44% of all units.

However, increasing the size of thermal power units is inherently not conducive to improving the flexibility of the power system. Because with the further increase in the proportion of renewable energy generation units, thermal power units will change from base load power to backup power in the future. In other words, at the peak of solar power generation, a large number of thermal power units must stop or operate at low load to give priority to solar power generation; When the wind power output falls down, the thermal power unit should be topped up immediately. This requires the thermal power unit to have enough flexibility. Obviously, the larger the unit, the less flexibility. In addition, if the 600,000-kilowatt supercritical unit is operated at low load, coal consumption and emissions will be greatly increased, and the purpose of energy conservation and emission reduction can not be fully realized.

Third, the power grid structure with strong transmission network and weak distribution network cannot meet the needs of user-side changes.

Energy transformation for the power system, there will be at least two major directional changes: first, with the emergence of a large number of distributed photovoltaic, small biomass power stations, multi-energy complementary microgrids, etc., on the user side, the electric energy of the power system will be one-way flow from the production end to the consumption end, into a two-way flow (the user also produces electric energy - that is, prosumer); The second is the transformation of power grid from vertically integrated centralized power grid to distributed flat power grid.

Both of these changes require a digital, intelligent and locally balanced local distribution network. Whether it is due to the need for the "integration" of a large number of small distributed power stations, or the need for distributed access of a large number of energy storage equipment, electric enterprises and other distributed access to optimize the operation and control of the distribution network, it is urgent to accelerate the transformation of the distribution network.

The technical level of China's transmission grid is considered to be the world's leading in the industry, but for a long time, China's investment is "heavy transmission light distribution", resulting in weak grid structure and low level of automation; The segmentation of basic data is seriously unable to be shared, and the level of informatization is low, which is far from meeting the challenges brought by the process of power system transformation, nor can it adapt to the requirements of future smart cities and low-carbon development.

Future trends of power structure

The future development trend of the power structure is described from two perspectives, one is a "scenario analysis" of the future power structure according to the requirements of energy transformation, and the other is that the energy transformation leads to changes in the power system from the structural aspect, that is, the power system transformation.

Institutions have different views on how low-carbon the future electricity mix (supply or consumption) should be. In general, renewable energy research institutions tend to be largely optimistic, while the various reports issued by fossil energy groups are largely conservative estimates. Whether optimistic or conservative, they simply reflect "scenario analysis" under given conditions. What matters is how the conditions for this scenario can be achieved.