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MIT Solar Towers Beat Solar Panels By Up To 20x
An anonymous reader writes "A team of MIT researchers has come up with a very different approach to solar collectors: building cubes and towers that extend solar cells upward in three-dimensional configurations. The results from the structures they've tested show power output ranging from double to more than 20 times that of fixed flat panels with the same base area (abstract, full pre-print). The biggest boosts in power were seen in the situations where improvements are most needed: in locations far from the equator, in winter months and on cloudier days."
Picture available here. It's a solar pancake!
So, MIT has basically recreated what a 7th grader has previously done.
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Big surprise that structures in volumetric configurations ended up being more efficient at gathering energy... considering plants have known this since they left the seas hundreds of millions of years ago.
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As seems depressingly common in science journalism, they vaguely mentioned the existence of a paper, but don't actually give the title or (dare we hope) a hyperlink to the paper. At least they did mention the name of the journal it was published in.
In any case, the paper is "Solar energy generation in three dimensions." If you're at a university with a subscription the official version (not open-access) is here. There is also an open-access preprint version at the arXiv.
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Most people use solar panels because they can be comfortably put on rooftops. If someone has enough room for these 3D structures they could just install a Sun tracking system that's even more efficient.
The cost/watt is higher, this is DOA I dare say.
They're simultaneously saying that it's most beneficial for northern/southern areas where daylight is diminished and that it's a more compact arrangement of cells.
Those two don't go together well... Most northern and southern areas have very large open areas due to having low overall population density.
Cost/Watt is all that matters in most areas for solar panels, Watt/weight in the rest. I can't see this being of use except in powering small devices
20x output (compared to a flat panel with the same footprint).
Not really news. This is like excitedly proclaiming that a 20 story building has nearly 20 times the floorspace of a single story building with the same footprint. Uh, no shit? (Or that a 20 story building receives more insolation than a 1-story building; hmm, you think maybe it has a lot more surface area?) I also like that they hand-wave away the fact that it costs significantly more per unit output by saying that cells are getting cheaper. Great.
Not that there aren't uses - it absolutely makes sense to go this route where you have limited footprint space - but it just doesn't seem at all revolutionary. I guess if you tack the letters M-I-T onto a press release it instantly becomes newsworthy.
I agree about shadow effects. More comes into play though since more angles will be approximately normal to the panels more angles of light will still be in an effective region of the panel for collecting. In winter in the non-tropical regions the sun's maximum height can be pretty low in the sky giving you a very oblique angle to fixed panels against a roof (assuming a shallow slope on the roof). Making these suckers stick up means that the crossection exposed to the sun is larger even if the sun is lower in the sky.
That said two problems I see:
1) Roof top intallation will be weight. I have panels on my roof and they are about 100lb per sq yard. Stack twenty together and you'd be looking at 2000lb per sq yard. Not a good thing for the roof.
2) Ground based panels: you can put the panels on stands that can be adjusted, heck they can be motorized so they can track the sun through the day AND through the seasons. So why exactly would you by ~20X more panels (at about 200 a pop) when a $50 motor per panel (guessing), or an adjustable stand that someone goes out and tilts every month or so can have the same affect?
Quick, someone alert all of the major energy companies so they can buy up the patents and sit on them for eternity!
That is not correct. Re-read the article.
"Re-" read?
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Ooh, now there's a configuration for you. Solar panels strapped onto the blades of a wind turbine.
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The summary accurately says the "same base area", i.e. footprint. This is not the panel area. The GP is underwhelmed with this announcement for good reason. This is not a breakthrough in efficiency in anything except the area required to erect the structure. It doesn't make better use of available light. It just captures more by reaching higher, making adjacent areas less valuable or even useless for further solar installations.
They suggest these towers and other configurations as useful for locations where available footprint is limited, such as urban areas. I dread the day when I start seeing such structures, erected by neighbours, looming over my fence and blocking out the sunlight to my patio, garden or my own solar collectors.
Bad form to reply to oneself, but I found the discussion of the methods I believe the article was referencing in this comment on the Watts Up With That article.
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No, they are using *significantly* more cells. Read the article. They're going by the ground footprint.
That is, the area of the earth that is being used by their solar cell array.
Let's say you have a tower ten feet high, covered in solar cells. Which is essentially what they have here. That tower is *obviously* going to have more surface area than just the amount of earth covered up by the base of the tower, since you're coating the sides as well as the top.
Actually, we get 1,000 watts from sunlight per square metre, so it would take a very minor portion of the earth's landmass to power our civilisation.
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You don't even need a motor, you can construct the tracker movement like a huge swiss clock. Some cogs, pins, belts, and a ~50 kg weight that you pull up every morning. Virtually bullet-proof, perfect in third world countries where motors are likely to be cannibalized or break down and not get repaired. (Disclaimer: not my idea, I saw someone testing such a device last summer.)
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Solar shingles have been around for quite some time.
http://www.google.com/search?&q=solar+shingles
If our conversation is going to follow the pattern of a typical slashdot discussion thread, you will now need to retroactively define the terms "major", "mass produced", and "smaller" in such a way that you can insist that I am not only wrong, but also a smelly hippy that likes Hitler.
Exactly. It's like claiming skyscrapers are more efficient than single-story buildings. So why aren't all new buildings skyscrapers? Simple: because they cost far more, per square foot of usable floor space, than conventional buildings. Hence, skyscrapers are only used in two places: 1) places where the land cost is enormous due to demand, and 2) places where politicians/leaders want to show off and rig things so that it's economical for someone to build them (e.g. with giant tax breaks or subsidies), which is why you see them in places like Kuala Lumpur and Dubai.
It's a stupid concept. If I had been asked to review their paper I would have recommended not publishing it. Here's a link to their abstract:
http://pubs.rsc.org/en/content/articlelanding/2012/ee/c2ee21170j
"We demonstrate that absorbers and reflectors can be combined in the absence of sun tracking to build three-dimensional photovoltaic (3DPV) structures that can generate measured energy densities (energy per base area, kWh/m2) higher by a factor of 2–20 than stationary flat PV panels for the structures considered here, compared to an increase by a factor of 1.3–1.8 for a flat panel with dual-axis sun tracking."
Yet they admit the following: "The increased energy density is countered by a larger solar cell area per generated energy for 3DPV compared to flat panels (by a factor of 1.5–4 in our conditions)...." IOW, they need a larger cell area by a factor of 1.5 to 4 to generate a given amount of energy than would be needed by a flat panel! So they admit their concept is a factor of 1.5 to 4 less efficient than a flat panel. But how can that be true, if their design generates significantly higher energy densities?! Probably they're merely generating higher peak energy densities at certain times and in certain localized regions of their solar panels, while their average energy density (averaged over their entire solar-panel area and over the entire operation time) is lower by a factor of 1.5 to 4.
All they're really claiming is that they can reduce the variability of the power generated by stationary solar PV panels:
"3DPV structures can mitigate some of the variability inherent to solar PV as they provide a more even source of solar energy generation at all latitudes: they can double the number of peak power generation hours and dramatically reduce the seasonal, latitude and weather variations of solar energy generation compared to a flat panel design."
But is a reduction of variability worth sacrificing total energy production by a factor of 1.5 to 4? Not likely.