By Mike Kulesky, director of marketing, energy storage and enclosures, EnerSys
Further complicating matters is the increased pressure to incorporate renewable energy from sources such as solar and wind power. With renewable energy usage and installations on the rise across the globe, demand for reliable backup also is growing. While these are clean power sources, they aren’t always reliable -- the amount generated fluctuates depending on how sunny or windy it is.
Energy storage helps utilities integrate renewable resources and also offers many other benefits. It helps to stabilize the grid by offering voltage regulation, frequency regulation, ramp control and peak shaving. Integrating a large-scale energy storage system also may help defer investments in new transmission and distribution lines.
Energy storage: The systems approach
Say hello (again) to the humble battery -- an energy storage solution that’s been drawing a lot of attention among utilities. That’s because a properly designed power-and-backup system with the right storage battery can have a major impact on performance, efficiency and longevity for renewable applications.
The same is true for backup power systems for rural settlements, communications systems and lighting systems -- all characterized by deep discharge-and-recharge cycles that are intertwined with partial state of charge (PSOC) cycles.
That said, selecting a utility-scale commercial backup system is a complex decision. Choosing the right battery for the application is the first step. Technology considerations include:
· How long must it run? Short (power) or long (energy) discharge period? Or do you need both?
· How long must it last? (Cycle life, Depth of Discharge, Ambient conditions [temperature])
· How much space is there? (power vs. energy density?)
· How is the project being funded?
Batteries have evolved to meet the changing needs of the utility industry. Backup systems are available in a wide array of chemistries, including nickel zinc, nickel cadmium, lithium ion, Valve Regulated Lead Acid (VRLA), flooded lead acid and advanced lead acid, such as Thin Plate Pure Lead (TPPL). These vary in terms of performance capabilities, maintenance requirements and durability/life expectancy.
Beyond the battery, other components of an energy storage backup system include:
· Power conditioning system: Putting together an efficient, flexible and highly modular system helps to optimize the transfer of energy between a DC energy storage system and the grid.
· Battery management and monitoring system: Collecting data and analyzing trends help to ensure the safety of the entire system. A monitoring system also may include devices to detect fire, gas and spills.
· Shelter: In choosing a battery, the climate and environment must be taken into consideration, especially since solar and wind farms often are located in remote locations, such as deserts where the daytime temperature soars well above 100 degrees Fahrenheit, but may be much cooler at night. Temperature extremes can damage to batteries, so it is important to monitor their internal core temperatures.
· Financing: Will the battery system be a capital investment or part of your operating expenses? Will you require funding for all or part of the system? Financing a project of this scope can be challenging.
Finally, when selecting an energy storage supplier, look for a vendor that is knowledgeable about the various battery technologies and is able to discuss how to treat the battery, how to measure the battery charge and how to proactively manage the battery system.
Rutland, Vermont: Power storage in action
One way that utilities are optimizing renewable energy while increasing reliability and efficiency is by supporting community energy storage programs. Rutland, Vermont, is at the forefront of this new movement.
Rutland is home to the Stafford Hill Solar Farm -- the first project to establish a micro-grid that is powered only by solar and battery backup, according to the U.S. Department of Energy.
The Green Mountain Power pilot project features 7,700 solar panels situated on 15 acres at the closed Rutland city landfill, making it the first known U.S. solar storage project to repurpose brownfield land. Stafford Hill can generate 2 MW of electricity. That’s enough to power about 2,000 homes during full sun -- or 365 homes year-road.
Perhaps more important, there’s 4 MW of battery storage for solar generation. In fact, the entire circuit can be disconnected from the grid in emergencies, providing power for an emergency shelter at adjacent Rutland High School.
Those batteries -- housed in four outdoor shelters -- are of a sealed lead acid construction, although there also are some lithium ion batteries for use in shorter duration outages. Each shelter houses 480 batteries.
Stafford Hill may just be a fledgling project, but rest assured it’s the first of many as energy storage moves into the 21st century -- and beyond.
EnerSys, the global leader in stored energy solutions for industrial applications, manufactures and distributes reserve power and motive power batteries, battery chargers, power equipment, battery accessories and outdoor equipment enclosure solutions to customers worldwide. Motive power batteries and chargers are used in electric forklift trucks and other commercial electric powered vehicles. Reserve power batteries are used in the telecommunication and utility industries, uninterruptible power supplies, and numerous applications requiring stored energy solutions including medical, aerospace and defense systems. Outdoor equipment enclosure products are used in the telecommunication, cable, utility, transportation industries and by government and defense customers. The company also provides aftermarket and customer support services to its customers from more than 100 countries through its sales and manufacturing locations around the world.