Solar energy is intermittent because solar panels only generate electricity when the sun is shining. On cloudy or rainy days, or at night, solar panels will not produce any electricity. Battery storage solves this problem by storing excess solar energy produced during the day for use later on, even when the sun isn’t available. Large-scale battery systems connected to solar farms can collect and save the solar energy that is generated during peak production hours. This stored energy can then be discharged from the batteries during non-peak hours, evenings, and when cloudy weather inhibits solar generation. In this way, battery storage smooths out the variable nature of solar power supply and makes solar energy available around the clock.
These large battery systems provide grid stability by helping to balance electricity demand and supply even as solar availability fluctuates throughout the day. When solar generation exceeds immediate demand, batteries can charge up with this excess renewable energy. Then when clouds roll in or electricity use increases in the late afternoon or evening, the batteries discharge the stored solar power back to the grid to help meet demand. This means utility operators do not have to ramp up inefficient “peaker plants” as quickly when solar drops off, improving grid reliability. The batteries act as a virtual power plant, regulating voltage and frequency on the grid.
By storing solar power when generation is high and releasing it when generation drops, battery storage increases the capacity factor and utilization rate of solar installations. Without batteries, solar farms and rooftop arrays may only generate electricity 20-30% of the time on an annual basis. But pairing solar with storage boosts this up to 50-80% utilization by allowing the solar energy to be used long after dusk even though the panels are not producing at that time. This means the economics of solar improve significantly with batteries. More hours of generation per day and per year means the solar investment generates electricity returns for a larger fraction of hours in the year.
Batteries also provide a more consistent power output from variable solar, helping satisfy the stringent power quality and ramp rate requirements (how quickly supply needs to change) that utilities impose on renewable energy generators connecting to the main power grid. Solar power naturally fluctuates a lot from minute to minute depending on passing clouds. Grid-scale batteries can even out these fluctuations by absorbing excess energy during short spikes and then releasing it slowly and consistently to offset periods when solar generation falls. This ensures steady, reliable, predictable power delivery to the grid.
From the utility perspective, battery storage provides essential services like frequency regulation, voltage support, and contingency reserves that are necessary to maintain a stable grid. During abnormal events like generation or transmission outages, fast responding battery systems can instantly discharge energy to help fill supply gaps and prevent cascading blackouts due to frequency or voltage deviations out of safe ranges. They act as an uninterruptible power supply (UPS) providing backup power at lightning speed when needed most. This versatility and reliability make batteries an important component enabling higher penetrations of renewable energy across multiple grids.
As battery storage technology continues advancing rapidly in terms of performance, efficiency, lifespan and declining costs, it is poised to take on an even bigger role stabilizing the variability of renewable resources like solar and wind power worldwide. Larger grid-scale installations of 100MW or more that can discharge for several hours use high-capacity battery chemistries like lithium-ion, zinc-bromine, and lead-acid to tackle intermittency challenges at the terawatt-hour scale. Pairing renewable energy generation with colocated battery facilities is becoming increasingly common both for utility-scale projects and distributed, behind-the-meter residential and commercial solar+storage deployments as well. The synergies between solar, batteries and intelligent inverter and software control systems ensure more dispatchable and firm solar power supplies for customers and the grid alike. In the future, mass deployment of battery storage will help facilitate high penetration levels of solar and renewable energies globally to power sustainable economies with clean, affordable zero-carbon electricity around the clock.