When it comes to solar panels and their energy output, it’s not just sunshine and rainbows. Despite the sun’s generosity in beaming down an astronomical amount of power, those on the quest to harness this energy face an old chestnut – nature’s inescapable limits.
As it happens, solar photovoltaics, or solar PVs or simply solar panels, are intermittent, i.e., they can only generate power when the sun is shining, unlike technologies that generate energy by burning fuel (like gas, coal, and nuclear power) and which you can turn off and on as needed.
Solar PV can’t generate electricity on demand
Indeed, this intermittency presents a fundamental challenge, especially as the amount of light a solar PV panel receives will vary depending on the time of day, time of year, and where on our planet the panel is located, according to the results of a recent deep-dive analysis published by Construction Physics on March 20.
Then the researchers observed the issue of electricity demand, both over the course of a single day and seasonally, which isn’t terribly convenient for solar. Specifically, peak electricity demand occurs in the early evening, well outside peak solar hours – when there’s no sunlight at all and solar production is basically nothing.
On the other hand, peak power generation of a solar panel is in the middle of the day, when the sun is highest in the sky. This doesn’t align all that well with electricity consumption and demand patterns (which, as a reminder – are the highest in the early evening, when people typically are home after work).
This misalignment between electricity demand and solar PV supply is demonstrated in the form of a ‘duck curve,’ which shows power required from non-solar sources when there’s a substantial amount of solar capacity on the grid.
Other problems for solar panels
And because of the tilt of the earth’s axis shifting in relation to the sun during the year, the same solar panel in the same location will produce markedly different amounts of power at different times of the year, even before considering things like cloud obstruction.
As for clouds, not only will they sporadically reduce the power generated by panels, but cloud cover tends to be higher in winter, additionally reducing what researchers have described as the “already-anemic wintertime PV output.”
All things considered, day-night cycles, varying solar irradiance based on time of year and geographic location, as well as cloud obstruction all mean that solar PV panels are often producing a lot less power than they theoretically could.
So… what can we do?
One of the possible solutions to sunshine’s fickle behavior, which presents a major challenge to a wider proliferation and general usability of solars, is to try using these other sources when the sun isn’t shining and can be turned on and off on demand (like gas turbines), or other intermittent sources with peak production offset from solar (such as wind).
However, if we really insist on using solars exclusively, then we could try increasing the amount of their power output by building more of them, using solar cells with a higher conversion efficiency, tilting the panels to a more favorable angle, using mirrors or lenses to concentrate more light onto them, or putting them into space, where they would receive sunlight nearly 24/7.
Another way, according to the researchers, would be adding some form of energy storage, be it using electricity from our PV panels to spin a flywheel, pump water uphill, synthesize methane to later burn, or – more feasibly – by placing it in large lithium-ion batteries.
Ideally, the solution would include both – increasing the power produced by the panels, as well as adding more storage.
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