In some industries and businesses with high electricity consumption, the electricity price is relatively high, and the peak valley price difference is large. The monthly electricity bill is a significant expense, and it cannot be delayed. It must be paid in cash every month. At present, there are many methods to save electricity. One is throttling, which means using energy-saving equipment such as frequency converters, energy-saving lamps, energy-saving doors and windows, etc. The second is open source, which means finding other energy sources besides the power grid. With the price reduction of materials and equipment such as photovoltaic modules, installing photovoltaic power generation on rooftops is a good choice. After the issuance of the 823 policy by the Energy Bureau, there were no subsidy targets for distributed photovoltaics in the second half of 2018. However, the National Development and Reform Commission and the Energy Bureau issued documents to support the development of energy storage. With the large-scale application of batteries, the previously high battery prices will also be rapidly reduced. Therefore, installing energy storage on the basis of photovoltaics or user side energy storage can bring good benefits.
Below is an analysis of the characteristics and investment economy comparison of three projects: photovoltaic, photovoltaic storage, and user side energy storage.
Taking a certain industrial plant in Guangzhou as an example, the peak electricity price in the area is 1.0348 yuan/kWh, and the time period is from 14:00 to 17:00 and from 19:00 to 22:00; The average electricity price is 0.6393 yuan/kWh, and the time periods are from 8 to 14 o'clock, 17 to 19 o'clock, and 22 to 24 o'clock; The off peak electricity price is 0.3351 yuan/kWh, and the time period is from 00:00 to 8:00. The peak load power of the factory is 500kVA. The factory starts at 8am and ends at 6pm. The annual working time is about 280 days.
At present, there are no subsidies for both photovoltaics and energy storage. Relying on payment for these three projects has no investment value. Therefore, the following model is set as the factory owner has spare funds to invest, and photovoltaic power generation or energy storage is used to offset electricity expenses, without calculating the cost of payment for funds, as well as various expenses such as taxes and rent.
1. Photovoltaic grid connected system
Characteristics: Photovoltaic grid connected system, where solar energy is prioritized for the load. When the load cannot be used up, excess electricity is sent to the grid. When the photovoltaic power is insufficient, both the grid and the photovoltaic can supply power to the load. Photovoltaic power generation relies on the grid and sunlight. When the grid is cut off, the inverter will activate the islanding protection function, and solar energy cannot generate electricity, and the load cannot work; The system output power is synchronized with the lighting, and is not related to the peak and valley electricity prices of the power grid.
According to the company's electricity load power and usage situation, a 400kW photovoltaic power station will be installed. During the start-up period, all photovoltaic electricity can be used for self consumption. The surplus electricity will be connected to the grid before 8am and after 6pm on normal working days, as well as on rest days. The electricity will be sold to the power grid company at a desulfurization price of 0.4153 yuan. The comprehensive calculation shows that the proportion of self use is 80%, and the proportion of surplus electricity connected to the grid is 20%.
The initial installation cost of the entire system is 1.8 million yuan. 400kW is located in the Guangzhou area, with an average annual power generation of 400000 kWh and a self use ratio of 80%, about 320000 kWh. The peak period is about 120000 kWh. Calculated at a price of 1.0348 yuan per kWh, the annual revenue is 124000 yuan, and the average period is about 200000 kWh. Calculated at a price of 0.6393 yuan per kWh, the annual revenue is 128000 yuan, with a surplus grid connection ratio of 20%. It is sold to the power grid company at a desulfurization price of 0.453 yuan, with a total cost of 36000 yuan, totaling 292000 yuan.
2 Photovoltaic energy storage systems
Compared to grid connected power generation systems, photovoltaic energy storage systems have added charge and discharge controllers and batteries, resulting in a system cost increase of about 30%, but with a wider range of applications. One is that it can be set to output at rated power during peak electricity prices to reduce electricity costs; Secondly, it is possible to charge during valley periods and discharge during peak periods of electricity prices, and make money by utilizing the price difference between peak and valley periods; Thirdly, when the power grid is cut off, the photovoltaic system continues to operate as a backup power source, and the inverter can switch to off grid working mode. The photovoltaic and battery can supply power to the load through the inverter.
The above project is to add an energy storage system to the photovoltaic power station. The photovoltaic power is set at 250kW, and the energy storage system is equipped with a 250kW PCS bidirectional energy storage converter and a 1000kMH lead carbon battery. The initial installation cost of the entire system is 2 million yuan. The average annual power generation of the photovoltaic system is 250000 kWh. During 80% of the start-up period, the system is designed to output power at the peak of electricity prices, 20 * 1.0348=20700 yuan. During 20% holidays, it is sold to the power grid company at a desulfurization price of 0.453 yuan, and 5 * 0.453=22700 yuan. By using the price difference of 0.7 yuan per kWh between peak and valley, it can charge 500 kWh per day, with a charging and discharging efficiency of 0.85. During peak periods, it can discharge 425 kWh, saving 272 yuan in electricity bills per day; A power outage in the power grid can cause significant losses to factories. An hour of power outage can result in losses of several thousand to tens of thousands of yuan. Installing an energy storage system and using it as a backup power source is estimated to cost around 21000 yuan per year, which adds up to approximately 327000 yuan.
3 User side energy storage systems
The user side energy storage system mainly consists of bidirectional energy storage inverters and batteries, which can be charged during valley and peak electricity prices, and used as a backup power source during power outages. As for the above project, we will design a 500kW PCS bidirectional energy storage converter and a 2200kWH lead carbon battery. The initial installation cost of the entire system is 1.8 million yuan.
By utilizing the peak valley price difference for charging and discharging, the efficiency is calculated to be 0.85, and the designed peak discharge is 1500 degrees. The total price difference is about 980 yuan, which is approximately 274400 yuan for 280 days per year; A power outage in the power grid can cause significant losses to factories. An hour of power outage can result in losses of several thousand to tens of thousands of yuan. Installing an energy storage system and using it as a backup power source is estimated to cost around 40000 yuan per year, which adds up to approximately 314400 yuan.
