Renewable energy sources like solar or wind are far from steady. Electricity production on a rainy morning or on a windless day could be very far from what you get in a sunny, bright and windy afternoon. But demand for electricity on the local grid could be the same or even face sudden peaks.
That’s why, depending on renewables, up from a local utility down to a residential system, one must take suitable precautions when demand and renewables energy generation are out of balance, which is often the case in early mornings and evenings, when demand is usually high and cannot rely on weather conditions.
The most obvious solution to this unpredictability is energy storage. Modern Energy Storage Systems (ESS) tend to rely on battery systems, a common way of storing electrical energy transforming it into electrochemical energy.