Check out our article in Going Green Magazine: Bermuda Media — Going Green
Every system in life should be balanced, from your bank account balance to an island’s energy balance. Energy storage is one method to balance our energy system, which is why Bermuda Electric Light Company Limited (BELCO) installed the Nolan Smith Battery Energy Storage System (BESS). The BESS provides another cost-effective method to balance the energy demand of the people of Bermuda.
With a fluctuating renewable energy supply, energy storage is critical to secure the energy system. Imagine a day with cumulus cloud cover[1], passing over the island causing solar fluctuations. BELCO is responsible for producing energy when the sun is not shinning on the solar panels.
It is the equivalent of a tandem bicycle with two riders trying to maintain speed (+/- 1%) whilst riding over the hills and flats. Now imagine the back rider messing around, pedaling hard, pedaling soft, then not at all and everything in-between with no rhythm, this is what solar energy appears like to the grid. The front rider must react now, to not only the hills and the flats of the road, but also the variability of the back rider, whilst also meeting strict speed regulations. One solution to the front rider is to use an electric tandem bike with battery storage that smooths out the variations from the back rider and matches the demand of the road letting the front rider carry on pedaling as efficiently as possible.
As we move towards more and more renewables the rider at the back becomes more powerful, and hopefully one day is the main driver of the bicycle. Then the key to successful renewable energy adoption will be adequate storage for quick and easily dispatchable energy to deal with large fluctuations. Imagine the tandem cycle where the back rider is so powerful, they can push the bicycle and charge the battery sometimes and let the battery power the bike the rest of the time. Eventually to a point that the front rider is doing nothing but controlling the battery and not burning any fossil fuels. It is not likely that a single rider in the back is powerful enough to do this, which means we need a special tandem bike with many more riders in the rear with different renewable energy sources to drive the bike and charge up the energy store if the front rider is never to burn fossil fuels.
Energy storage for utility scale energy systems is not limited to batteries, but includes technology such as pumped hydropower storage, spinning flywheels, large capacitors, flow batteries, thermal storage and compressed air energy systems to name a few.
Energy storage can be broken down into 4 main energy groups, gravitational and mechanical, electrical and electrochemical, thermal and chemical. Gravitational and mechanical includes systems that store potential energy such as pumped hydro and gravity-based storage systems. Mechanical systems also include flywheels, compressed air and liquid air storage. Electrical and electrochemical systems include rechargeable batteries, supercapacitors and flow batteries. Short term solar variability such as cumulus clouds can be met by spinning flywheels and capacitors that have high power outputs for short durations, however large cloud cover can last days and requires high power storage for long durations. Thermal energy technologies typically take advantage of the phase change of materials, for example cold energy is stored as ice, whilst hot energy is stored in molten salt energy. Finally, chemical energy storage includes natural gas, oil, coal and hydrogen. It is important that the lifetime cost and operability of the storage system meets the needs of the renewable energy fluctuations and demand profiles but is cost effective, safe and long lasting.
Batteries are a common form of energy storage, and the technology has developed a lot over the past century. There are a range of different battery chemistries, including but not limited to lead-acid, lithium-ion and sodium-sulphur. All batteries are a form of dense energy storage and require proper handling and operational safety measures. The BESS has a 10MW capacity with 5MWh of energy storage and can output 10MW for 30min, or 5MW for 1 hour. To provide power for one business day in Bermuda (9am to 5pm), the system would require over 130 BESS batteries fully charged at 9am just to get to 5pm, if we assume an average load of 82MW. Abu Dhabi have an NGK 108MW/648MWh NAS battery which can deliver the peak demand of Bermuda for 6 hours. Based on the NGK brochure, this would take approximately 6 acres of land.[2]
In summary, energy storage Is essential to the success of Renewable Energy, but takes up space, and that is one of our most precious resources on the island.
—
[1] Types of Clouds | NOAA SciJinks – All About Weather
[2] https://www.ngk-insulators.com/en/product/nas-configurations.html
