Good case to share | business energy storage system design

Under the goals of "carbon peaking and carbon neutrality" and "building a power system dominated by new energy", wind power, photovoltaic and other new energy sources are developing rapidly, but the main bottleneck of new energy generation lies in intermittency, randomness and volatility. To solve such problems, the energy storage system needs to provide flexibility adjustment and key support.

Photovoltaic power generation curve on sunny days

Graph of photovoltaic power generation on a cloudy day

Electricity generation statistics of a power station in October

Energy storage can be applied to the various links of power/transmission/distribution/use, and play multiple roles.

The topic of this discussion is user-side energy storage design based on a series of industrial and commercial energy storage inverters.

Different from large-scale energy storage peak-modulation power stations, the main purpose of industrial and commercial energy storage systems is to realize the return on investment by using the peak-valley difference of the power grid, and the main load is to meet the internal power demand of industrial and commercial industries, to maximize the photovoltaic power generation for self-use, or to arbitrage the peak-valley price difference. The system is mainly composed of photovoltaic module, optical storage unit, battery pack, load and so on. The array of photovoltaic modules converts solar energy into electricity when there is light, and supplies power to the load through the optical storage unit, and also charges the battery pack at the same time. In the absence of light, the battery pack supplies power to the load through the fusioncube. The main application scenarios are office buildings, shopping malls, industrial and commercial parks, island micro-networks, villages, and large households.

01 Optical storage machine

Its function is to regulate and control the electric energy generated by the solar cell module into sine wave alternating current.

02 Battery String

Its main task is to store energy, ensure the energy balance and stability of energy supply, in the night or rainy days to ensure the load demand.

03 AC PDC

It mainly plays the role of switching off and protecting the AC output side.

04 Intelligent Energy manager SEM

It can communicate with optical storage machine, smart electricity meter and battery. It has dry contact and external oil control machine, and can access customers' emergency stop, fire protection, security and other systems to meet complex system linkage requirements.

05 Photovoltaic Module

The main part of a solar power system that converts solar radiation into direct current energy.

WIT Industrial and commercial light storage application scenario solution system diagram

WIT Outlying Island microgrid application scenario solution system diagram

Design Principles of industrial and commercial energy storage systems

01, load type and power determine the selection of optical storage all-in-one machine

Load is generally divided into inductive load and resistive load, central air conditioning, compressors, cranes and other motor load is inductive load, motor starting power is 3-5 times of rated power, the initial design of the equipment off-grid operation, generally take these load starting power into account, the output power of the inverter is greater than the power of the load. For monitoring stations, communication stations and other strict occasions, the output power is the sum of all the load power. However, in this energy storage system, WIT series (currently 50K/63K/75K/100K, 4 power segments) has strong load capacity, supporting motor loads and 100% three-phase unbalanced loads, and can overload 110% for a long time.

02. Single-day power consumption Confirm the power of components

The module is designed to meet the daily demand of the load under average weather conditions, which means that the annual output of the solar cell module is equal to the annual electricity consumption of the load. Because weather conditions can vary from below average to above average, solar modules are designed to meet the needs of the worst seasons, even when the battery can be fully charged almost every day. The power generated by the components cannot be fully converted into electricity. There is also the efficiency of the controller and the loss of the machine, as well as the loss of the battery pack, which can also lose 10-15% during the charging and discharging process. Available power of energy storage system = total power of modules * average hours of solar power generation * Controller efficiency * battery pack efficiency.

03, battery design capacity

The task of the battery pack is to ensure the normal power consumption of the system load when the solar radiation is insufficient. The capacity of the battery pack can be designed according to the actual situation. Three points should be paid attention to in the design: the voltage of the battery pack should meet the voltage of the optical storage system (WIT series battery operating voltage range is 600-1000V (under 3P3W) / 680-1000V (under 3P4W)); The amount of electricity stored by the battery pack should meet the requirements of the user (time shift of energy, peak valley arbitrage, etc.); When off-grid operation is required, consider the backup power supply in rainy days.

04. EMS scheme

Like large energy storage systems, commercial and industrial energy storage systems include energy management systems (EMS). Guruwatt EMS solution is SEM (Smart Energy Manager), using lithium battery as energy storage device, through the local and remote EMS management system, complete the power supply and power demand balance and optimization among the grid, battery, all-in-one machine, load, etc. Besides, EMS of industrial and commercial energy storage systems is also different from large energy storage power stations in that it does not need to consider the demand of power grid dispatching, but mainly provides power for local area. It only needs to have energy management and automatic switching within the local area network.

conclusion

"Photovoltaic + Energy Storage" Industrial and commercial energy storage is the most reliable and potential application at present, and it is also the most likely to be applied on a large scale distributed photovoltaic solution. In places with high electricity prices and large peak-valley price difference, reasonable design can achieve high investment returns.