Solar panels at night? What utter nonsense!
11-04-2022 | By Robin Mitchell
Often there will be news sites that publish stories about revolutionary devices that claim they will change the world, but these are almost always snake oil. Now, the media is publishing news that says solar panels operating at night to produce night energy would solve the renewable energy problem. What is being told by the media, why is it complete utter nonsense, and what would actually solve the renewables energy problem?
New revolutionary solar panels generate energy at night
Researchers from Stanford University have recently created a new type of solar panel that works in the dark by taking advantage of radiative heating of the earth’s surface to generate renewable energy at night when the temperature drops. The idea behind the new device is that PN junctions found in solar panels also generate electricity when exposed to a temperature difference, and the radiative thermal losses from the panel on the top side combined with the heating from the earth’s surface can be used to generate electricity.
According to the researchers, they have managed to achieve energies of around 50mW per square meter, which, compared to standard solar panels, is approximately 0.00025% of the energy generated by a 20% efficient solar panel assuming a 1000W per square meter of solar radiation. While this is nowhere near enough to run anything serious, it is enough to trickle charge a small phone or run a few LEDs.
Now, the media has picked up on this news and has started to report that the revolutionary new green technology could be used to provide power to those in remote locations during the night and even reduce the size of storage technologies needed. In fact, a quote from the research paper itself even suggests that such a technology could eliminate the need for battery storage, thus solving the renewable problem once and for all.
Why is this complete nonsense?
Words cannot describe the feeling of grotesqueness and repulsion I have for such published papers and the media frenzy that follows. It is amazing how little scientific scrutiny there is in the media for claims made by scientists, and instead of crunching the numbers, they instead write their reports as fast as possible. The use of terms such as “revolutionary” and “next-generation” tries to grab the attention of those who do not have the technical abilities to challenge what has been reported.
Fortunately, not much knowledge is needed to tear down the research that has been reported by the media and show it for what it really is, snake oil. The paper states that its panels produce 50mW per square meter, and this works out to be 0.00025% of what a typical panel could produce. Now, 50mW is great for a remote IoT device or monitor that communicates with a remote server once in a while, but powering anything serious quickly becomes problematic.
Take, for example, a refrigerator which is one of the few devices that must constantly run. While these devices use very little power, they will typically use 200W to 400W of energy, so let’s be generous and use 200W. The number of panels needed to run such a device continuously would be 4000 square meters of panels or around 4000 panels.
The researchers claim that they will be able to get around 1W per panel. This would provide a better alternative than battery technologies which only have a few thousand charging cycles. Even at this power, a fridge would still require 200 panels, and this is assuming that the ground below the panel was heated up sufficiently during the day.
For perspective, a battery with a capacity of 1Whr could provide 50mW continuously for 20 hours, and a cheap 9V PP3 650mAh lithium rechargeable battery can provide 5.5Wh (or 200mW for 20 hours). This would only be from a single battery, whose price is a fraction of the cost of the panel and would require little to no maintenance. Also, keep in mind that the size of a PP3 battery is minimal and could very easily be integrated into the electronics of the solar panel.
When it comes down to it, there is no scenario where a solar panel utilising thermal energy would ever help anyone except power a small LED or trickle charge a mobile device (assuming it even could).
What would actually solve the renewable crises?
Trying to extract 50mW per square m2 of a solar panel at night with the idea of eliminating the need for batteries makes no sense whatsoever, and it is possible that a miniature pumped hydro or DC motor connected to a weight would store far more energy than what the panel would produce. While the idea behind the energy capture technology is to not need any additional hardware, its minuscule size makes it unusable for humans except for running a small microcontroller, sensor, or LED.
It would make far more sense for researchers to focus on creating energy storage solutions that are reliable, require minimal maintenance, and are built directly into the solar panels. For example, supercapacitors could be integrated into the junction box of the panel that can be used as a battery for the storage of small quantities of energy. Assuming that the panel is connected to other electrical equipment, it can already be assumed that some level of maintenance is required, even in the most remote locations.
Overall, there are a ton of solutions that would help remote locations with energy storage and trying to capture the heat from the earth is not going to help human activities. Furthermore, a great deal of shame should be felt by media sites that do not compute the figures of these research papers and recognise that their research will amount to nothing.