Peltier cells on the backs of solar panels: Insane or just impractical? - Page 1
Forum section: electronics / projects

author: RyuHimora
author_rank: Newbie
timestamp: May 09, 2016, 04:31:57 pm
content: I've been thinking about ways to improve the efficiency of solar panels, and so far the only one that hasn't seemed like it would be impossible is to use peltier cells to recycle the heat generated from the inefficiency into (maybe?)usable electricity. However, I am aware that a peltier cell needs quite a substantial temperature gradient between the two sides to generate much power at all, and that they are only 10-15% efficient anyway. So is this something worth my time to go out and test, or am I just completely up the wrong tree?

author: dralthi
author_rank: Contributor
timestamp: May 09, 2016, 04:50:09 pm
content: I've used Peliter cells a little bit...the problem you will have is how to keep the other side cool. For good efficiency, they need max DeltaT from one side of the peliter to the other.So, I don't see a way that you can cheaply maintain that temp gradient because the heat from one site will thermally conduct to the other side, rendering the device essentially useless after some time.https://en.wikipedia.org/wiki/Thermoelectric_generator

author: Siwastaja
author_rank: Super Contributor
timestamp: May 09, 2016, 04:50:19 pm
content: I haven't run the numbers, but I'll have a very strong educated guess that you are orders of magnitude better off by just cooling the backside of the panel directly, hence increasing the panel efficiency, instead of cooling the peltier backside and requiring the panel to run hot (and lower efficiency) to generate any power at the peltier.Quite frankly, almost any time anyone suggest a Peltier element for almost any purpose, the answer is "no". Peltiers are far more suboptimal than people seem to think, for both power generation and cooling applications.If it made economical sense to generate solar power using Peltiers, we would be already doing it instead of using photoelectric panels. Area is not often the limiting factor, cost is, so why not just install more solar panels.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 09, 2016, 06:51:02 pm
content: Quote from: RyuHimora on May 09, 2016, 04:31:57 pmPeltier cells are even worse. They are more like 10-15% of the carnot efficiency. So for something like a 30 C temperature difference this would be more like 10% of 10% or 1 % efficiency for the peltier.Keeping the solar cells cold is possibly more effective, though it depends on the type of cells.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: May 09, 2016, 10:30:54 pm
content: Engineering rathole.http://www.tinaja.com/glib/hack68.pdf

author: Someone
author_rank: Super Contributor
timestamp: May 09, 2016, 11:24:19 pm
content: There has been a lot of work on this concept from when the silicon cells were expensive:https://en.wikipedia.org/wiki/Photovoltaic_thermal_hybrid_solar_collectorNow the cells are so cheap its harder to justify the added expense when just adding more PV cells would have a better return on investment.

author: Zeranin
author_rank: Regular Contributor
timestamp: May 10, 2016, 11:07:58 am
content: Quote from: RyuHimora on May 09, 2016, 04:31:57 pmI can't add much to what many wise people here have said. The idea is completely impractical, and won't work at all unless you can cool the back-side of the Peltiers. Why would you want to improve the efficiency anyway, as it's much more cost effective just to add more panels. If area is in short supply, which is the only situation where efficiency actually matters, then you are much better off to spend extra for premium, higher-efficiency panels. As a technical exercise that makes no economic sense, you would be better off just to cool your existing panels. Also as a technical exercise, you could install trackers, but in practical terms you get more watt/dollar just by adding more panels. In summary, when viewed from any angle, your Peltier idea is a waste of time and money. I added another few kW to my system last weekend, now up to 10kW, way to go ....