A recent report in the New York Times examined how California is using huge rechargeable batteries to store excess solar energy in the middle of the day when it’s not needed. The batteries can then be drained when local power needs are at their maximum in the late afternoon and early evening.
These batteries are basically time shifters. Within limits, they can be an excellent idea.
The batteries already installed in California can store enough electricity for a few hours after sunset, reducing the need to burn natural gas to produce electricity.
But the limited usefulness of batteries becomes clear when we consider longer time spans. As the New York Times report notes, “there is much more solar energy available in the summer than in the winter, and no battery can store electricity for months to make up for these seasonal differences.”
This statement is not an exaggeration. The photovoltaic panels on my roof produce only a fifth as much electricity per month in the middle of winter as in summer.
A better alternative to time-shifting excess energy may be location shift: move it via a grid to another location where it is currently needed.
I remember shortwave radio broadcasts from the Netherlands – heard everywhere – greeting listeners with ‘good morning, good afternoon or good evening’. The point was that when it is morning in some locations, in other parts of the world it is afternoon or evening.
In other locations it is the middle of the night. And of course, solar panels do not produce electricity in the middle of the night. But electricity will still be needed.
One way to produce nighttime electricity is by burning natural gas. But we will avoid that by building a global network that allows nighttime power to come in from areas where the sun is currently shining. Instead of shifting the time when solar energy is used, it will… place where it is used.
The question naturally arises: what is the better approach: time shifting or location shifting? Both strategies are probably better than the current widespread practice of wasting the output of solar panels when they could produce more electricity than is needed locally.
But location shifting (grid) has one big advantage over time shifting (batteries, etc.). Batteries may be able to store enough energy to get an area through the night or a day or two in bad weather. But to echo the New York Times report, they can’t get us through the winter slump in locally produced solar energy.
Location shifting avoids the winter problem because winter does not occur everywhere on our planet at the same time. Winter in the Northern Hemisphere happens to be summer south of the equator.
The global electrical grid will allow seasonal exchange of solar energy from south to north during our winter, and from north to south during our summers.
Of course, a small amount of electricity is lost in long-distance transmission, even when using HVDC (high-voltage direct current), which is much more efficient than AC (alternating current). But the charging and discharging of batteries also suffers from efficiency losses.
This also applies to other possible methods of time shifting, such as creating ‘clean hydrogen’ using locally unnecessary solar energy and then burning the hydrogen or running it through fuel cells later.
In fact, a global power grid – already under construction – could virtually eliminate the need for batteries that can handle nighttime and bad weather. A system that can handle the large fluctuations in solar energy from season to season will automatically be able to handle the smaller daily fluctuations for which we currently need batteries.
By shifting locations, solar energy can supply electricity anywhere 24/7/365. The current intermittent problem will become a thing of the past, as that past will be remembered by future generations living in the age of solar energy.
— Paul F. deLespinasse is professor emeritus of political science and computer science at Adrian College. He can be reached at pdeles@proaxis.com.
This article originally appeared in The Daily Telegram: Paul deLespinasse: Solar Time Shift vs. Location Shift
