What kind of energy storage system is needed for photovoltaic power generation (I)

There is no future for photovoltaics without energy storage. Last year, he talked with a big man in the industry, Zhu, and he put forward the idea that the development of energy storage technology is the lifeblood of the development of the photovoltaic industry. When the entire grid only accounts for 1% of renewable energy, no one cares; it can project the future according to the current industry development speed of more than 20%, and the PV penetration rate of 10% and 20% is not far away.

The role of energy storage is in the large time scale (hours), mainly for peak shaving, that is, matching between the power generation side and the power side. That is basically what is cheap, lead-acid, lithium batteries used in cascades, flow batteries, water storage and storage are all options, not discussed in this article. In the smaller time scale, energy storage is also extremely important. Photovoltaic and wind energy are called “garbage electricity” because of the unkindness. It is because the power and voltage output of wind power generation is unstable by day, and the problem of unsatisfactory waveform and uncoordinated frequency in DC-to-AC has caused great pressure on the power grid. And energy storage can solve these fatal problems to a great extent. However, energy storage technology is varied. What kind of energy storage is needed for photovoltaic power generation?

The “Suitability of representative electrochemical energy storage technologies for ramp-rate control of photovoltaic power” of the University of New South Wales, Dr. Jiang Yu’s “Applicability of mainstream electrochemical energy storage technology for the control of photovoltaic power generation climbing rate”, clarified the train of thought for everyone. .

In order to reduce the pressure, the grid has put forward requirements for the stability of photovoltaic power plants, which has become a major trend. For example, Germany has proposed a climbing rate of up to 10% per minute, which means that the difference in power output of photovoltaic power plants cannot be higher than 10% at each time and one minute before. Newly introduced grid-connected standards in many countries require photovoltaic power plants to have power-down and reduced output when necessary, as well as smooth climb rate requirements. In cloudy weather, 50% of the rate of climb is also common, so it must be treated (see figure below). Power electronics such as component optimizers and micro-inverters can achieve smoothing to a certain extent, but the processing power is very limited, and the method of solving the problem is simple and rude, or is it to make the component power generation deviate from the optimal power point, or It is to cut off the extra output, in order to meet the stability requirements of the grid must be cut. At this time, the energy storage system is the key to play a role: once the power generation surges, it will be charged (instead of cutting off the excess power directly); once the power generation bursts, it will discharge and achieve continuous and stable power to the power grid.