Energy storage is key to making renewable energy accessible night and day, when solar panels don’t produce, and during windless days when wind turbines don’t spin. There are various technologies that enable energy storage; some are more accessible than others.
Battery energy storage systems (ESSs) may be placed throughout various segments of the electric grid – from transmission and distribution networks, generators and even end user homes.
Battery Storage
Battery Energy Storage Systems (BESSs) can respond to sub-hourly variations in electricity demand within minutes, from minutes down to fractions of seconds, providing stability for grid voltage and frequency characteristics, thus helping maintain voltage and frequency ranges within expected parameters. Furthermore, operators of BESS can make money through arbitrage by storing and discharging power from BESS at different times – an act called arbitrage.
PACE systems typically deliver their full capacity over four hour durations, though emerging technologies are increasing this maximum discharge length. They enable renewables to be integrated into the grid more seamlessly by mitigating peak power demand, and may replace some fossil fuel-fired power plants – although likely this remains only a small share of total electricity production.
Battery storage offers organizations tremendous value across various value streams, though its specific benefits and costs depend on your energy consumption and location. If you’re curious to pursue a battery storage project, we advise conducting a feasibility study to understand how much you could save as well as any benefits it might bring at your site.
Solar Photovoltaic (PV) Storage
Solar PV panels turn sunlight into electricity using the photovoltaic effect. Photons that strike the PV cell can either reflect off its back surface, or be absorbed by semiconductor material and converted into DC electricity by an inverter for use in homes.
With a battery, you can store electricity until it’s needed most – helping avoid peak demand times while taking advantage of lower buyback rates from your utility provider during those periods.
Battery storage systems are typically coupled with solar installations and can be set up in various ways depending on your unique requirements. Lithium-ion batteries have historically been the go-to choice, though new technology offers cheaper and scalable alternatives that may better meet your needs.
Hydroelectric Storage
Pumped hydro energy storage (PHES) is enjoying a surge in popularity as industry recognizes its advantages for improving grid reliability, sustainability, and resilience. At utility scale PSH can offer long-duration services like system inertia regulation, voltage and frequency regulation, fast ramping capabilities of an ancillary grid service provider with fast ramp times as well as black start capabilities – as well as black start capability.
Pumped storage involves using large water reservoirs for bulk energy storage and reversible turbine-generator assemblies that act both as pumps and power plants to provide energy at peak efficiency to both thermal sources (coal, nuclear power or natural gas) as well as renewable resources like wind or solar energy sources. Pumped storage aims to balance load on the power grid, smooth out rapid changes in demand, and enable thermal power plants (coal nuclear or gas) or variable renewable resources to run more efficiently than usual.
Pumped storage power plants operate by harnessing low-cost surplus off-peak electricity to pump water uphill between reservoirs, then release this water through turbines at times of peak electrical demand to generate power. They are highly efficient with round trip efficiencies surpassing 80%.
Flywheel Storage
Flywheel energy storage utilizes a high-speed mechanical rotor to both store and generate electricity. Its inertia drives a system which converts its kinetic energy into electricity as needed.
As this technology matures, its application to UPSs and power conditioning equipment that enhances electricity quality for critical or protected loads has grown increasingly attractive. Momentary power fluctuations often interfere with hospital CT/MRI systems requiring constant electricity flow – potentially risking costly damage to equipment if there are momentary variations – thus necessitating instant backup power to meet their demands. Flywheels combined with UPSs offer instantaneous backup to meet such sensitive loads’ demands.
Flywheels differ from other forms of energy storage in that their mechanical energy is directly stored, rather than chemically stored, unlike batteries which use chemical processes to store energy. As such, flywheels have shorter discharge durations than batteries yet still deliver hundreds of kilowatts within minutes when used in a flywheel farm arrangement. Furthermore, composite materials may provide higher strength-to-density ratios and allow more than 400 Wh/kg energy storage capacities in large scale deployments.