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Maintaining proper levels of reactive power is a growing challenge across the U.S. energy grid. The reactive power problem is fairly simple – if the grid is unable to maintain a stable level of reactive power, the system will be unable to balance voltages across infrastructure and maintain consistent energy delivery. This becomes an issue as power travels over long distances or is transmitted across different lines. Energy storage can simplify load balancing and provide cost-efficient reactive power.
According to an Oak Ridge National Laboratory study detailing the causes and implications of a major outage in Ohio in the early 2000s, issues pertaining to reactive power can gradually erode the stability of the electric grid to the point that even a small disruption to generation or transmission can snowball into a large and extended outage.
"Battery systems can be a reactive power source when problems emerge."
Considering the implication of reactive power imbalances
In an ideal AC current, reactive power will be maintained at a fairly constant rate, allowing active voltages to move through the transmission grid and provide working power. Failure to sustain reactive power levels has lead to numerous major outages, caused by issues like voltage drops and voltage swings. According to the ORNL, there are few vital considerations when working to maintain reactive power in an increasingly complex utility grid. Proximity is one of the most important issues.
When it comes to reactive power, quickly resolving any problems is essential. If reactive power levels drop precipitously, the ability to distribute power through the grid diminishes and resolving reactive power issues becomes nearly is possible. This is the chain reaction that leads to extended and damaging outages. The document from the ORNL explained that having generation sources in close proximity to areas where reactive power levels tend to sag is incredibly important in terms of nipping any problems in the bud and preventing outages.
Using energy storage to support consistent reactive power delivery
While putting generation sources in close proximity to places where reactive power capabilities are an issue sounds like a simple solution, it is usually an incredibly expensive and disruptive problem. The reality is that reactive power tends to sag most dramatically in areas that are either already far away from existing generation sites or in locations where the grid is so complex that balancing workloads is difficult. In either case, quickly ramping up generation to maintain proper levels of reactive power is extremely difficult.
This problem is becoming more complex as grid operators move away from traditional fossil fuel generation sites and integrate diverse renewable generation sources into the grid. Many emerging generation models can not ramp up energy delivery as traditional power plants. Renewable sites are also restricted in terms of where they can be deployed based on issues like land availability and locations where environmental conditions can support consistent power generation. This is where energy storage systems can cost-efficiently improve grid conditions.
Battery systems can store power when the grid is healthy and quickly deliver that energy as a reactive power source when problems emerge. Furthermore, batteries can be distributed throughout the grid where it will have the most impact in overcoming proximity challenges, letting you resolve reactive power issues without taking on major upgrades to transmission lines and other supporting infrastructure.
This ability to simultaneously resolve reactive power generation issues and defer major construction projects leads to considerable value creation for grid operators. On one level, you are providing a significant reliability and resiliency improvement for your grid, something that leads to major customer-facing benefits. At the same time, avoiding high construction costs offsets the price of energy storage, adding substantially to the return on investment that comes from battery systems.