After installing a photovoltaic (PV) system, businesses can consider installing an energy storage system, but a comprehensive evaluation of the following factors is necessary:
I. Load Assessment
Load data from the power grid transformers can be retrieved and analyzed.
1) If the PV load is fully fed into the grid during the day, the PV power is not being used up, so energy storage is unnecessary.
2) If it’s a 24-hour load, and the nighttime grid electricity price is cheaper than the PV grid connection, then energy storage is also unnecessary.
3) If there are plans to achieve a green point absorption rate for green factories, or if there are backup power needs (such as electric furnaces or equipment that cannot be shut down), adding energy storage can be considered. This can improve the PV absorption rate and provide necessary power support during power curtailment, or allow for dynamic capacity expansion based on operational strategies.
4) If PV output is less than the load, and most of the deviation occurs during peak hours, adding energy storage can be considered. The energy storage can be charged at night and used during the day in conjunction with PV output and energy storage peak discharge to reduce grid power consumption, lower electricity costs, or generate arbitrage opportunities.
Solar power backfeeding indicates a problem with the company’s power grid integration, making energy storage a poor choice. Check the load data; if backfeeding occurs during the energy storage charging period, it’s unaffected; however, if backfeeding occurs during the discharging period, energy storage is not recommended.
II. Economic Assessment
1) Peak-Valley Electricity Price Difference: This is a key factor in assessing the economic value of an energy storage system. If the company’s region implements time-of-use pricing policies and the peak-valley price difference is significant (generally recommended to be above 0.8 yuan/kWh), then arbitrage through charging during off-peak hours and discharging during peak hours can generate substantial economic benefits for the company, with a relatively short payback period.
2) Investment Costs and Expected Returns: The initial investment cost of the energy storage system needs to be considered, including equipment purchase, installation, and commissioning costs. Simultaneously, considering the company’s electricity consumption and pricing policies, estimate the annual electricity cost savings from the energy storage system, as well as potential other benefits such as demand-side response subsidies. This will allow for the calculation of the payback period and internal rate of return, determining the feasibility of the investment.
3) Transformer Capacity and Expansion Costs: When the energy storage system is charging, it acts as an electrical load. If the existing transformer does not have sufficient spare capacity to charge the energy storage system during off-peak and peak periods, it may be necessary to expand the transformer’s capacity. At this point, the cost of expansion must be weighed against the benefits brought by the energy storage system. If the expansion cost is too high, it may reduce the economic viability of the energy storage system.
III. Technical Feasibility Assessment
1) Compatibility between Energy Storage and Photovoltaic Systems: It is essential to ensure that the energy storage system can seamlessly integrate with existing photovoltaic systems, including electrical parameter matching and control strategy coordination. For DC-coupled and AC-coupled systems, the choice needs to be made based on the specific circumstances of the enterprise. DC-coupled systems have lower costs but lower flexibility, suitable for scenarios where users have lower daytime loads and higher nighttime loads; AC-coupled systems have higher costs but higher flexibility, suitable for applications where photovoltaic power generation systems have already been installed.
2) Energy Storage System Capacity Configuration: The capacity of the energy storage system should be rationally configured based on factors such as the enterprise’s electricity load curve, peak and off-peak electricity demand, and transformer capacity. For example, during peak daytime electricity prices, the power of energy storage charging plus the maximum load during that period should be less than 80% of the transformer capacity to prevent transformer overload. Simultaneously, during peak daytime electricity prices, the load should exceed the peak discharge power of the energy storage to fully utilize energy storage arbitrage.
3) Energy Storage System Charging and Discharging Strategy: A suitable charging and discharging strategy needs to be developed to ensure the energy storage system can be fully charged during off-peak hours and effectively discharged during peak hours, while avoiding impact on the power grid. This requires consideration of local grid policies, the company’s production plans, and the performance parameters of the energy storage system.
IV. Safety Assessment
1) Battery Safety: The battery is the core component of the energy storage system, and its safety is paramount. Batteries that meet relevant safety standards should be selected, such as those that have passed drop, nail penetration, and short-circuit tests. At the same time, attention should be paid to the battery management system (BMS), which can monitor the battery status in real time and prevent abnormal situations such as overcharging, over-discharging, and overheating.
2) Fire Prevention and Protection Measures: The installation site of the energy storage system needs to have good fire protection conditions, such as sufficient fire extinguishing equipment and fire-resistant barriers. Simultaneously, according to the requirements of the local fire department, safety protection passages and isolation passages should be reserved to ensure the safe evacuation of personnel in the event of fire or other emergencies.
3) System Stability: The connection of the energy storage system may have a certain impact on the enterprise’s power system, therefore, it is necessary to assess its impact on grid stability. For example, it is necessary to ensure that the charging and discharging process of the energy storage system does not cause grid voltage fluctuations, frequency anomalies, or other problems that affect the normal operation of other equipment.
V. Site and Environmental Assessment
1) Installation Site Conditions: The installation of the energy storage system requires a suitable site. The site should be located outdoors, flat, dry, waterproof, and fireproof, avoiding direct sunlight to reduce machine temperature and the energy consumption of the equipment’s temperature control. At the same time, a location should be chosen close to the access point’s power distribution room (ideally within 100m) and convenient for cable routing. If indoor configuration is adopted, the area should be located away from office areas and densely populated areas as much as possible.
2) Environmental Adaptability: Local environmental conditions, such as altitude, temperature, humidity, and rainfall, should be considered, and appropriate anti-corrosion, explosion-proof, and foundation elevation treatments should be carried out for the energy storage system. In addition, the potential impacts of noise and electromagnetic radiation generated during the operation of the energy storage system on the surrounding environment and people should be assessed.
VI. Policy and Market Environment Assessment
1) Policy Support: Understand local government policies regarding commercial and industrial energy storage systems, such as subsidy policies, entry thresholds, and grid connection requirements. Some regions may offer subsidies or preferential policies to companies installing energy storage systems, which will help reduce their investment costs.
2) Market Demand and Development Trends: Pay attention to the development trends and market demand of the energy storage market, and assess the application prospects and value changes of energy storage systems in the future. With the acceleration of energy transition and the emphasis on renewable energy utilization, the demand for energy storage systems may continue to increase, but market competition may also intensify.
In conclusion, whether to install an energy storage system after installing a photovoltaic system requires comprehensive consideration of multiple factors. Only when it is economically feasible, technically reliable, safe, has suitable site and environmental conditions, and a favorable policy and market environment can installing an energy storage system bring the expected benefits and value to the company.
