The U.S. power grid is comprised of several energy sources from fossil fuels to nuclear energy to renewable energy sources. Battery Energy Storage Systems (BESS) balance the various power sources to keep energy flowing seamlessly to customers. We’ll explore battery energy storage systems, how they are used within a commercial environment and risk factors to consider.
What is Battery Energy Storage?
A battery is a device that can store energy in a chemical form and convert it into electrical energy when needed.
There are two fundamental types of chemical storage batteries:
(1) The rechargeable, or secondary cell
(2) The nonrechargeable, or primary cell.
They both discharge energy in a similar fashion, but only one of them permits multiple charging and discharging.
Battery energy storage systems are typically configured in one of two ways, depending on their intended application:
(1) A power configuration
(2) An energy configuration
In a power configuration, the batteries are used to inject a large amount of power into the grid in a relatively short period of time, which requires a high inverter-to-battery ratio. A typical application would be to simulate a gas turbine ramp-up for frequency regulation, spinning reserve, or black-start capacity.
In an energy configuration, the batteries are used to inject a steady amount of power into the grid for an extended amount of time. This application has a low inverter-to-battery ratio and would typically be used for addressing such issues as the California “Duck Curve,” in which power demand changes occur over a period of up to several hours; or shifting curtailed PV production to later in the day. BESS projects are increasing in popularity due to the fluctuating power supply from renewable energy power sources.
BESS mainly performs one or more of these specific tasks:
- Provide voltage support for the transmission grid (e.g., when the actual grid voltage differs from the stated voltage).
- Provide stability in response to grid power oscillations (e.g., system faults).
- Help control the turbine ‘ramp rate’ (e.g., response to sudden change in wind speed or electrical demand).
Rechargeable Batteries and BESS
A rechargeable battery comprises one or more electrochemical cells. It is known as a ‘secondary cell’ because its electrochemical reactions are electrically reversible. Rechargeable batteries come in many different shapes and sizes, ranging from button cells to megawatt grid systems.
The batteries alternately store and discharge direct current (DC) electrical energy. The convertors change it to AC power, the Converter Transformer ‘steps up’ the alternating current (AC) voltage to match the desired output, the Control System coordinates the numerous processes taking place and the cooling system removes the intense heat generated by the DC/AC conversion.
One of the distinctive characteristics of the electric power sector is that the amount of electricity that can be generated is relatively fixed over short periods of time, although demand for electricity fluctuates throughout the day. Developing technology to store electrical energy so it can be available to meet demand whenever needed would represent a major breakthrough in electricity distribution. Helping to meet this goal, electricity storage devices can manage the amount of power required to supply customers at times when need is greatest, which is during peak load (demand). These devices can also help make renewable energy, whose power output cannot be controlled by grid operators, smoother and more easily dispatched.
BESS projects can also balance microgrids to achieve a match between generation and load. Storage devices can provide frequency regulation to maintain the balance between the network’s load and power generated, and they can achieve a more reliable power supply for high-tech industrial facilities.