The intermittency of solar power is driving interest in grid-scale energy storage systems (ESS).
Harvesting electricity from the sun is becoming ever more efficient and price competitive, but one of the biggest drawbacks of grid-scale solar power remains intermittency, and the technology’s reliance on other power sources to step in on cloudy days, or once the sun sets.
Solar power generation on a rainy morning is very different from production capacity on a bright and cold morning, although electricity demand may be the same. Where high capacity solar photovoltaic (PV) generation is installed, local utilities need to have suitable alternatives in place when demand and PV generation are unbalanced, such as early morning or evening, when demand is high.
One obvious solution to intermittency is to create systems that can store the surplus power from renewable generation and make it available for use on demand. This need is driving significant interest in community and grid-scale energy storage systems (ESS).
In September 2015, the consulting firm Frost & Sullivan released a new report that forecasts the market for ESS will grow 20 times in the decade between 2014 and 2024.
An old concept
The idea of energy storage is not new. Pumped storage hydropower projects stockpile and generate energy by moving water between two reservoirs at different elevations. When demand is low, excess energy is used to pump water into the upper reservoir. When demand is high, the stored water is released through turbines to the lower reservoir, generating electricity.
Renewables like solar and wind generation tend to rely on battery storage systems, which stockpile electrical energy by transforming it into electrochemical energy. These systems come in many sizes and configurations, from 3-6 kilowatt (kW) for residential use to utility-scale solutions topping 4 megawatts (MW) or more.
Like large solar PV systems, large ESS installations operate in a range of direct current (DC) voltages, from about 600 volts (V) to 1,000 or even 1,500 V DC. Nominal DC current is comparable to PV systems, and plant layout can connect basic battery modules in series, like PV strings.
But ESS is also different from PV systems in important respects. To overcome the high risk of short-circuit currents in battery storage systems, ABB provides bidirectional circuit breakers that help protect them from overloads and short circuits.
The presence of peak current during battery discharge can also lead to damaged circuit breakers that may appear closed and in good condition, but are actually unable to operate properly. On the alternating current (AC) side, high harmonics can create unwanted trips in normal currents, so components that are immune to harmonic malfunctions are essential.
Energy storage systems must be carefully designed and integrated into solar infrastructure, using components that ensure safe, reliable operation. Components that integrate and protect energy storage systems in PV installations must be chosen with great care.
ABB has tremendous expertise and many valuable products in this area. Our project managers can help design and select the best possible devices for energy storage systems, under all conditions.
For large energy storage systems these include ABB low-voltage products like Tmax and Emax 2 LV main AC circuit-breakers, the most compact breakers available that are also immune to high harmonics. Or LV converter components such as the CP-E power supply, featuring low power and heat dissipation with up to 94 percent efficiency, and the CM-IWN insulation monitor for high-rated DC voltage, with capacity up to 1,000 volts DC in coupling unit CM-IVN.
The ABB LV product lineup for energy storage systems also covers battery protection units for high-rated voltage, including the S800, Tmax PV and Emax DC circuit breaker product ranges, or the OS fusible switch product range. The most compact units on the market range from 880 to 1,500 volts DC capacity.
ABB’s main DC breaker or switch-disconnector for high-rated voltage include the Tmax and Emax DC ranges, with capacity up to 1,000 volts DC as automatic circuit-breakers, and up to 1,500 volts DC as switch-disconnectors.
ABB LV components in battery management systems (BMS) deliver high accuracy even in high temperatures, such as the ES series current sensor, which maintains one percent accuracy at temperatures of up to 70°C.