Spinning solar cells generate 20 times more electricity ...  - Page 1
Forum section: electronics / general

author: Bassman59
author_rank: Super Contributor
timestamp: June 21, 2015, 07:21:13 am
content: A bunch of my non-techie friends have postedthis linkon Facebook yesterday ... my response has been, "oh, my, more surface area of course means more generation in that footprint."NB it's one of those idiot "futurist design" websites, with zero technical competency.

author: German_EE
author_rank: Super Contributor
timestamp: June 21, 2015, 09:34:14 am
content: This idea is not as crazy as it looks. They are using an array of solar cells with lenses in front of each device, then rotating them so that the sun does not stay on one cell too long. Think of it as solar multiplexing.Does anybody have figures concerning the lifetime of solar panels when they overheat?

author: Psi
author_rank: Super Contributor
timestamp: June 21, 2015, 09:54:37 am
content: Reminds me of the TV show "Earth 2" they had spinning solar cells powering vehicles

author: wraper
author_rank: Unknown
timestamp: June 21, 2015, 09:57:24 am
content: Quote from: German_EE on June 21, 2015, 09:34:14 amWhy just not put a lens in the front of non spinning solar cells of the same area? How do they intend to transfer the power from this thing - rotary transformer? Also something tells me that solar cells will act like LEDs with such PWMed power (drop efficiency). If you put 10x power with 1/10 duty cycle, it won't be nearly as effective as with much lower but constant power.

author: Psi
author_rank: Super Contributor
timestamp: June 21, 2015, 10:06:34 am
content: Quote from: wraper on June 21, 2015, 09:57:24 amSurely you can trick the laws of physics in the same way you can trick the human eye

author: EEVblog
author_rank: Unknown
timestamp: June 21, 2015, 10:10:43 am
content: Quote from: German_EE on June 21, 2015, 09:34:14 amI was of the understanding that the high temp multi-junction cells that are designed to work with these lens are designed to work at the high temps.

author: SeanB
author_rank: Super Contributor
timestamp: June 21, 2015, 10:37:57 am
content: Solar cells lose efficiency as they get hotter ( voltage generated drops) so the best way is to put the cells under the lens on a nice thick aluminiumj heat spreader and then cool the back either with a passive radiator and convection cooling, or use a little power ( or a separate smaller panel) to run active cooling with either a fan or a water cooling loop.You probably could get the power up per square meter of silicon to the kilowatt level with good enough cooling, though there it probably would have to be using a heat pipe and radiator to get the other 10kW of heat out, though that would be good to run a building heating loop in winter, and dump it to ambient in summer.Going to be fun making a steerable 3m lens that will withstand hurricane level winds though.......

author: B.B.Bubby
author_rank: Regular Contributor
timestamp: June 21, 2015, 11:28:42 am
content: Looking at it, seems the biggest advantage is that the cells are always angled correctly.2nd advantage is that the magnifying lens boosts low light to overcome the low light dropout issue (or whatever proper engineering term) of the silicon. Maybe a 5 - 10% increase over a full day.Calling bullshit on the energy density calcs though. (apart from the 2nd point above)

author: Tandy
author_rank: Frequent Contributor
timestamp: June 21, 2015, 11:47:37 am
content: If heat is a problem pump water behind the panel to absorb the heat and use that heat as a hot water supply.

author: ivan747
author_rank: Super Contributor
timestamp: June 21, 2015, 12:12:21 pm
content: Quote from: German_EE on June 21, 2015, 09:34:14 amYes but it's gonna cost so much that it's not going to be cost effective, sadly. It is a good idea though, it could be useful in 15 or 20 years when solar panels become cheap and people start to look for more output per roof area.But, I can't help but think, they could have made the spinning design much more simple. Heck, they could have just cooled the panels in a different way.

author: ivan747
author_rank: Super Contributor
timestamp: June 21, 2015, 12:31:01 pm
content: Quote from: SeanB on June 21, 2015, 10:37:57 amNot that the normal panels will stand a hurricane anyway. Branches and crap like that fly in the air...

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: June 21, 2015, 12:34:24 pm
content: QuoteSomeone's comment on youtube.

author: SeanB
author_rank: Super Contributor
timestamp: June 21, 2015, 12:38:23 pm
content: Panels on a concrete roof typically survive, only those on wooden houses and mud huts blow away with the roof. You can make a roof easily withstand 100kph winds, and a concrete flat rooftop with panels on it can do more.

author: nctnico
author_rank: Super Contributor
timestamp: June 21, 2015, 12:52:46 pm
content: Quote from: SeanB on June 21, 2015, 10:37:57 amThat is not necessary. The maximum amount of energy the sun dumps on the earth's surface is 1000W per square meter in the most optimal location under the most optimal circumstances. IIRC the global average over 24 hours is about 166W per square meter.

author: ivan747
author_rank: Super Contributor
timestamp: June 26, 2015, 07:43:06 pm
content: Quote from: SeanB on June 21, 2015, 12:38:23 pmI do know that a concrete roof survives hurricanes (this house has survived several), and I believe you when you say bolted down panels will not fly in the air, but you know the wind often blows large things in the air and these panels are basically glass.But, just like you, I bet these spinning things won't survive anything. I can imagine the things breaking apart when the wind makes them rotate so fast that even a small unbalanced blade will break havoc.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: June 26, 2015, 08:11:04 pm
content: I don't get it.Solar irradiance peaks at about 1kW/m^2. Now you can either put a 1m^2 panel and collect ~20% of that 1kW, or you can put a 1m^2 lens to focus that light onto a much smaller panel and collect the same ~20% of that 1kW, with some spinning system or active cooling to keep it from overheating. Either way you STILL have a 1m^2 footprint, and you STILL only collect ~200W. The only difference is instead of having a 1m^2 panel, you have a much smaller panel with a 1m^2 lens and a cooling system. It doesn't make the system smaller, it doesn't make the system more efficient, you're just replacing your 1m^2 panel with a 1m^2 lens.Note that all of their marketing language is that the spinning system generates 20x more electricity than a static flat panelwith the same area of photovoltaic cells, NOT a static flat panel with the same area as their cone.

author: ivan747
author_rank: Super Contributor
timestamp: June 26, 2015, 08:25:20 pm
content: Quote from: suicidaleggroll on June 26, 2015, 08:11:04 pmThey do have an advantage, if this is not bullshit: smaller solar panel means less cost.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: June 26, 2015, 09:33:50 pm
content: Quote from: ivan747 on June 26, 2015, 08:25:20 pmSure, for the solar cells themselves. But tack on the cost of a massive cone-shaped lens, cone-shaped mounting system for the cells, motor to spin the assembly, high reliability sweeper system to transfer the power out of this spinning assembly (or however they plan to do it), high speed MANY channel MPPT to keep each cell at its peak power point despite spinning from sun to shade and back at ~20 RPM...I highly doubt it's going to be cheaper than a regular panel of equivalent power mated to an off the shelf MPPT, and there's no way it's going to approach the reliability of one.

author: PlainName
author_rank: Super Contributor
timestamp: June 26, 2015, 09:49:32 pm
content: QuoteWith the spinning cone, some number of cells will always be at the optimum angle to get max power, whilst the rest will vary between that and zilch. With a static panel, only for a bried period does the entire panel face the sun optimumly, so either side of that the panel efficiency will be low.To put it another way, the static panel output over time will show a classic bell curve. The rotating cone, OTOH, should show a much wider and flatter curve albeit with depressed top. Instantaneous output at midday is not the same as average output over the full day.I haven't done any sums and I doubt the 20x claim, but I think some are dissing this out of hand without twigging that it might not be as simple as first appears.

author: VK3DRB
author_rank: Super Contributor
timestamp: June 27, 2015, 12:49:20 am
content: "...their current prototype was recently third-party verified as capable of generating "over 20 times more electricity than a static flat panel with the same area of photovoltaic cells."Complete and utter.

author: LabSpokane
author_rank: Super Contributor
timestamp: June 27, 2015, 05:59:12 am
content: Quote from: suicidaleggroll on June 26, 2015, 09:33:50 pmThis stuff has been available for years in vastly mor practical forms, such as:In short, nobody buys them because conventional PV panels are cheaper and more reliable. This spinning thing is ridiculous in so many ways. It's really a twist on Solyndra, which failed spectacularly. Then they have sprinkled in some Solar Freaking Roadways stupidity with the thick, plastic lenses which will attnuate the light transmission.Then we get back to the simple fact that no lens will cause the light striking the earth to exceed 1kW/m2 on average.

author: PTR_1275
author_rank: Frequent Contributor
timestamp: June 27, 2015, 01:00:09 pm
content: I do remember reading an article several years back about solar concentrator systems and they do achieve higher conversion rates at the higher solar concentration, albeit not a huge gain. The problem is then getting the heat away as many people have already said.More concentrated light is still the same amount of w/m2 hitting the earth, but less silicon needed which can be an advantage. Couple that with complex spinning things, lens assemblies and cooling systems and the benefit disappears.In summer, I do quite often see the pyranometer at work hit 1200-1300w/m2, the highest I have seen was 1440w/m2 so the irradiance definitely doesn't max out at 1000w/m2 as some people have said.