Kimberly McGrath, director of business development at Maxwell Technologies discusses how the combination of supercaps and storage offers an economic way forward for grid development.
Hybridizing energy and power for the grid
September 27, 2016: Gaston County, North Carolina. It’s not the most famous spot in the US. Or not yet. But in terms of grid energy storage, it’s one of the hottest sites in what could be the cutting edge of how renewable energy will be integrated into the grid.
Guodian China and Duke Energy, the US utility, recently commissioned hybrid battery-ultracapacitor energy storage systems to stack multiple grid services into a single solution. The hybrid system capitalizes on the strong points of each technology: batteries for long-term energy storage and ultracapacitors for high power.
This mitigates the need to oversize batteries to meet system lifetime requirements.
When cloud cover or other weather events cause solar power fluctuations on the grid, this hybrid system leverages ultracapacitors’ high power and fast response capabilities. Ultracapacitors support battery performance by removing high peak power demand, which in turn, over time, mitigates battery capacity degradation.
This way, the batteries have an optimized performance for energy shifting of solar on the distribution circuit. This hybrid approach maximizes utility system value by simultaneously delivering these grid services at an overall lower system cost.
What does this in-field example of a hybrid battery-ultracapacitor energy storage system mean for the future grid?
More renewable energy is being added to the grid each year, and utility and grid owners are under pressure to implement solutions that help to deliver clean, reliable power to end users — and at the same time, they must find a way to minimize operating costs and increase returns.
The answer to this challenge is to integrate fast-responding energy storage, such as ultracapacitors, which can enhance renewable energy production by reducing — and in many cases, eliminating — the problems of intermittency.
Take the examples of frequency response and wind power smoothing.
In the case of frequency response, balance must be maintained on a second-to-second basis between electricity demand and generation to maintain grid stability. The tight frequency envelope has to be managed in second to sub-second time-frames to prevent system collapse.
Wind generators in particular should consider this factor — energy storage assets can be leveraged with ultracapacitors to provide frequency response.
Ultracapacitors are also an advantage for wind power smoothing. More intermittent renewable generation is penetrating the grid, and variations in wind power output can create faults on local transmission lines and result in poor quality power to the end customer.
Ultracapacitors can respond to these variations within milliseconds and prevent problems associated with power output fluctuations. Implementing ultracapacitors to rapidly deliver quality power ameliorates revenue loss associated with curtailment and can also help avoid expenditures for transmission line upgrades.
In addition, the growing demand for power quality has led suppliers to seek out new options for turbine wind pitch technologies.
Ultracapacitors have emerged as a practical solution for wind pitch control, due to ultracapacitors’ ability to produce high-quality, reliable power, provide faster charge and discharge cycles, a longer lifetime, and reliable performance in colder temperatures. Ultracapacitors offer these benefits and more — without dramatic increases in operating costs.
Energy storage systems that implement ultracapacitors significantly improve generation quality and reliability while at the same time offer operators a new frontier of financial savings.
The Duke Energy battery-ultracapacitor hybrid system acts as an illustration to utility and grid audiences worldwide on what the future of energy storage could look like. The energy density of batteries paired with the high power, fast response ability of ultracapacitors continues to demonstrate success in the field and may very well be setting the new standard for grid energy storage.