Grades 6–8 · Systems
How can solar energy and a battery meet a changing need?
Sunlit panels can produce electricity while a building needs little of it; its lights may be needed later, after sunlight has faded. Storage connects those different times. Solar generation can serve demand directly, and a battery can store a surplus for later use. It can deliver only energy already stored and cannot hold more than its capacity.
In the diagramIdeal energy account · one hourSolar 8 kWhDemand 4 kWhStart 2 / 6 kWhDirect useSurplusShortfallEnd 6 · unused 0 · unmet 0 kWh
This explanation accounts for one hour using kilowatt-hours, or kWh, a unit of energy. One kilowatt supplied for one hour transfers one kilowatt-hour. Solar serves demand first. If generation exceeds demand, the remaining energy charges the battery up to its 6-kWh capacity. Any surplus beyond that capacity is recorded as unused generation.
When generation is below demand instead, the battery can discharge some of its starting stored energy to cover the shortfall. If that is insufficient, part of demand remains unmet. Charging and discharging are not both applied to the same surplus-or-deficit interval in these stated rules.
Here solar supplies 8 kWh during the hour and demand uses 4 kWh directly. The remaining 4 kWh adds to the battery's starting 2 kWh, filling it to 6 kWh. The stored energy can meet a later need, but the full battery has no further space in this account. Storage changes when energy can be used; it does not make an unlimited reserve from one sunny hour.
About this explanation
The ideal one-hour account omits grid supply, conversion losses and charging-power limits. Its rule uses solar directly first and applies charging or discharging according to that interval's net surplus or deficit.
Starting knowledge: Use addition and subtraction with energy quantities and capacity limits.
Sources
- US Department of Energy — Solar Integration: Solar Energy and Storage Basics
- US Department of Energy — Solar Systems Integration Basics