Petroleum fired utility plants have the advantage of working at any time of day or night. No uncertainty. Dependability. When you know you’re going to need power, fire them up. It takes an electrical grid to distribute the power, but you can generate the power in the region you need it.
Wind and solar have their limits. They only work when the elements drive them, not just when we need them, so they all have to have petroleum utility backups. Wind and solar have their limits, unless we had batteries that would hold their output. If we had giant batteries that could hold enough energy for cities, we could produce excess power during the days when it’s sunny and/or when it’s windy, then use that energy during the night and when it’s not windy. Energy storage is the third leg of the stool to make wind and solar a practical solution. (California is working hard on grid-scale batteries, but we’re a long way from a national backup.)
We don’t have batteries like that yet. But in a way we do. We have a (mostly) national energy grid. If we can produce more energy than we need during peak production in one area and share it with another area of the country, that other area of the country could share it back during their peak production. Setting energy aside when we’ve got more than we need, then using it back when we need it. That’s a lot like a battery! Transferring energy back and forth across the country wouldn’t be exactly a battery, but it could produce the same results. A band of solar peak production works its way across the Continental U.S. from east to west every day. That’s four time zones in the Continental U.S. That just bought us four hours of “storage”! That’s four hours of energy we don’t need to put into batteries. Conceptually, if we had 24 time zones, that would be our full-time global battery! (Of course, there are transmission losses every time we move energy from one place to another, but let’s disregard that for this exercise.)
