The expanding grid-connected capacity of photovoltaic and the resulting grid impact have created more favorable conditions for the development of energy storage.
Photovoltaic energy storage differs from grid-connected power generation in that it utilizes batteries for storage and devices for charging and discharging the batteries; the initial investment will be greater, but the range of possible applications will be considerably broader. In this article, we present four PV + energy storage application scenarios that correspond to various applications: PV on-grid energy storage application scenarios, PV off-grid energy storage application scenarios, hybrid-grid energy storage system application scenarios, and PV micro-grid energy storage application scenarios.
1. Scenario for PV off-grid energy storage applications
Photovoltaic off-grid energy storage and power generation systems are increasingly utilized in remote mountainous regions, powerless areas, islands, communication base stations, and street lighting, among other places where they can operate autonomously without reliance on the power grid.
A PV array, a PV inverter, a battery storage, and a power load comprise the system. When there is light, the photovoltaic array transforms solar energy into electrical energy and simultaneously supplies power to the load via the inverse control integrated machine and charges the battery pack; when there is no light, the battery powers the AC load via the inverter.
Off-grid photovoltaic power generation systems are specifically engineered for deployment in regions lacking power grids or experiencing frequent power outages. These systems operate in a "storage and use" or "first storage and then use" fashion, analogous to how charcoal is sent through snow." "The snow embedded in the charcoal" In areas without a power grid or with frequent blackouts that affect families, off-grid systems are highly practical.
2. Scenarios for PV hybrid-grid energy storage applications
PV hybrid-grid energy storage systems are commonly employed during frequent power disruptions. High self-consumption tariffs prevent surpluses to the Internet; peak tariffs are significantly more expensive than valley tariffs and those for alternative applications.
Photovoltaic arrays comprised of solar cell modules, off-grid and grid-connected solar power integrated machinery, battery packs, loads, and other components comprise the system. In the presence of light, the photovoltaic array transforms solar energy into electrical energy and charges the battery bank while supplying power to the load via the solar control inverter; when light is absent, the battery charges the solar control inverter and subsequently supplies power to the AC load.
The inclusion of charge/discharge controllers and batteries in the grid-connected and off-grid system raises the overall cost by approximately 30%-50% in comparison to the grid-connected power generation system. However, this augmentation expands the system's potential applications. Firstly, it is possible to configure the PV system to generate power at its rated capacity during periods of high electricity demand in order to decrease electricity costs. Secondly, it is possible to charge the PV system during the off-grid working mode and discharge it during the peak electricity demand period, capitalizing on the price differential between the peak and valley segments. Lastly, in the event that the grid is unavailable, the PV system functions as a backup power supply, and the inverter can be deactivated to operate in an off-grid mode. Presently, this scenario is implemented more frequently in developed nations abroad.
3. Scenarios for on-grid photovoltaic energy storage systems application
On-grid energy storage photovoltaic power generation system, which operates in AC coupling mode predominantly using photovoltaic and energy storage components. In addition to increasing the proportion of self-generated self-consumption and ground-based photovoltaic distribution storage, industrial and commercial photovoltaic energy storage, and other potential applications, the system possesses the capability to store surplus power generation.
Solar cell modules comprise the photovoltaic array, which is complemented by a battery pack, charge/discharge controller PCS, and a power-consuming load. In situations where the solar power falls short of the load power, the system is powered in part by solar energy and the grid. Conversely, when the solar power surpasses the load power, a portion of the solar energy is utilized to supply power to the load, while the remaining portion is stored via the controller. Additionally, the energy storage system can be employed in demand management, peak and valley arbitrage, and other scenarios to augment the system's profitability model.
In China's new energy market, the PV grid-connected energy storage system has garnered considerable interest as an emerging renewable energy application scenario. By integrating an energy storage device, photovoltaic power generation, and an AC grid, the system maximizes the utilization of renewable energy.
4. Scenarios for micro-grid energy storage system applications
Due to its significance as an energy storage device, the micro-grid energy storage system is assuming a more prominent position in the power system and new energy development of China.
As renewable energy gains popularity and scientific and technological advancements continue to advance, the application scenarios for micro-grid energy storage systems continue to grow. These scenarios primarily concern the two aspects listed below:
1). Distributed power generation and energy storage system: Distributed power generation pertains to the placement of small-scale power generation apparatus in close proximity to the end user, utilizing sources such as wind energy, solar photovoltaic, and others. Any surplus power generated is subsequently stored in an energy storage system, serving as a backup power supply during periods of high electricity demand or grid outages.
2). Micro-grid power backup: For a reliable local power supply in remote areas, islands, and other locations with difficult grid access, micro-grid energy storage systems can be utilized as reserve power sources.
By leveraging multi-energy complementation, micro-grids can optimize the utilization of distributed clean energy's potential. This enables them to mitigate unfavorable aspects such as limited capacity, unreliable power generation, and unreliable independent power supplies, while also ensuring the secure operation of the larger power grid. As a result, micro-grids serve as a valuable supplement to the larger power grid. The scale of micro-grid application scenarios is considerably greater, spanning from a few kilowatts to tens of megawatts, and the variety of possible implementations is considerably broader.
The utilization patterns for photovoltaic energy storage are extensive and varied, encompassing micro-grids, off-grid systems, and grid-connected systems. Practical applications of renewable energy are characterized by the unique benefits and attributes of each scenario type, which collectively supply users with dependable and effective power.
As PV technology continues to advance and costs continue to decrease, PV energy storage will assume a more significant position in the energy system of the future. Simultaneously, the advancement and implementation of diverse scenarios will facilitate the swift progression of China's emerging energy sector and aid in the achievement of energy transformation and low-carbon, environmentally sustainable development.
