One of the main issues with solar panels in residential situations is how the peak electricity generation varies. In other words, there is a couple of hours mismatch between a typical home`s peak power consumption and the peak electricity output from the solar panels.
Letting the home draw power from the utility grid when there is an extra demand solves this, but for off-grid solar systems, this is often not possible. The utility grid can be too far out of range to justify setting up transmission cables, which is when a battery system can be used. This way, homeowners have the possibility to store excess energy during times when their solar panels generate more electricity than what they need, and use it during the night and on overcast days.
Image Credit: SMUD
A grid-tied solar system that also has batteries is called a hybrid solar system. You might ask why someone would invest in expensive battery packs if they easily could store excess power onto the utility grid? There are two important reasons for this:
Electricity from the power company is more costly during peak hours, which usually ranges from around 2 to 6 pm and gradually drops off until the cycle starts over again the next day. If homeowners use cheaper solar electricity stored by their own solar panels earlier in the day they save money. The utility company and electrical grid benefits by easing the peak load.
Not a lot of places have incorporated hybrid solar systems yet. In SMUD`s SolarSmart program, which is backed by the Department of Energy, California Energy Commission and SunPower, lithium-ion batteries have been installed in 42 homes in Sacramento Municipal Utility District.
“The aim of the program is to learn whether or not batteries can ease load demand and provide more electricity when renewable energy sources such as solar and wind power aren’t sufficient […] how battery storage and solar mesh with time-of-use rates, where customers pay more for electricity during peak hours and less during low-demand times. The batteries provide power during peak demand, so customers could save money by not drawing all their power from the grid during those hours.” said Paul Lau, SMUD assistant general manager for power supply and grid operations.
“Energy storage is potentially a game changer in our industry,” Lau said. “After this study is complete, we hope to have a much better idea whether energy storage benefits the customer and the utility, and how best to operate the system.”
The SMUD battery program has a price tag of $5.9 million. Each individual battery storage system costs somewhere around $25,000, which is even more than what the solar panels costs.
Blog post by Mathias from Energy Informative.