
MIT stacks solar panels like pancakes, increases their power output by up to 20x - evo_9
http://www.extremetech.com/extreme/123719-mit-stacks-solar-panels-like-pancakes-increases-their-power-output-by-up-to-20x
======
jacquesm
(1) You can't improve on solar panels by a factor of more than 5 because
'regular' photovoltaic cells are already ~20% efficient.

(2) any geometric arrangement of solar cells that includes the 'third
dimension' will shade an area behind it that is proportional to the height of
the stack, that dead zone should we taken into account when calculating
efficiency. In other words, the total surface area of the stack is what
counts, not just the footprint. And placing these panels at a 45 degree angle
actually _decreases_ their efficiency. The total output will go up but the
cost per Watt will go up as well (and it will go up more than the power
output).

Why is it that every announcement about solar panels is always accompanied by
either gross exaggeration or inaccuracies? This really gives a bad rap to the
whole renewables industry, if I had a 1% increase of efficiency on PV panels
for every 10x announcement I'd be at 300% efficiency by now...

MIT really hurts their reputation with announcements like these.

~~~
mrsebastian
As far as I can tell, (2) is already being taken into account. The original
press release does mention that they need to see how the stacks perform when
there's more than one though (because of shading).

Why does 45-degree panels reduce efficiency? I mean, it might reduce it when
the sun is overhead, but solar power is generally measured in the total
wattage it produces over a long period.

~~~
jacquesm
> does mention that they need to see how the stacks perform when there's more
> than one though

So how can they make this claim today? Besides that, that's pretty easy to
calculate, all you need is one of these:
<http://www.solarpathfinder.com/index>

It will show you quite precisely what the effect is of the object you place in
the path of the suns rays.

As for the 45 degree reducing effeciency: solar panels produce power that
varies with the angle of the incident light. So if you place one panel at
exactly 90 degrees to the incident light (for both 'tilt' and 'pan' or
elevation and azimuth if you want to be precise) then you have a panel that
performs at maximum efficiency (anywhere from 15 to 30% depending on how much
you were willing to pay for your cells). If you use two panels on a 45 degree
angle relative to each other the amount of output per panel drops but since
you have twice the active surface you can now combine the output of both
panels. Since one panel is 100% and the output varies as the co-sine of the
angle you now get 0.7 times the output per panel. This gives you 1.4 times the
output of a regular panel for a cost-per-watt of 2.0 times the regular panel.

------
backprojection
It's starting to get to the point where, if the title of the post begins with
'MIT', I put my expect-the-BS hat on.

Edit: to be clear, I think it's because MIT's PR departement is hyper-
inflatory, which you can hardly blame them for. But maybe due to it's
reputation, the regular press picks up on like it's golden.

------
DanBC
A much better version:

(<http://www.newsroomamerica.com/story/228653.html>)

([http://news.cnet.com/8301-11386_3-57404585-76/accordion-
shap...](http://news.cnet.com/8301-11386_3-57404585-76/accordion-shaped-solar-
tower-captures-more-light/))

([http://news.techeye.net/science/3d-solar-cells-could-
increas...](http://news.techeye.net/science/3d-solar-cells-could-increase-
energy-output-twenty-fold))

~~~
wtvanhest
_Amazingly, 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._

Lets say the current design takes up 1 cubic meter. (I can't tell from the
photo).

Lets say you have a 10,000 square meter roof, 100x100 meters.

Does this mean you can put 10,000 of them up there or a number far lower since
they need space in between them to let the light in?

The article isn't clear whether an arrangement of 20 of them is more efficient
then the space required, but it does hit at it when it says: _Then, to confirm
their model’s predictions, they built and tested three different arrangements
of solar cells on the roof of an MIT laboratory building for several weeks._

~~~
DanBC
More testing and simulation is needed.

> _So far, the team has modeled individual 3-D modules. A next step is to
> study a collection of such towers, accounting for the shadows that one tower
> would cast on others at different times of day. In general, 3-D shapes could
> have a big advantage in any location where space is limited, such as flat-
> rooftop installations or in urban environments, they say. Such shapes could
> also be used in larger-scale applications, such as solar farms, once shading
> effects between towers are carefully minimized._

~~~
wtvanhest
I have no idea how I missed that. But it is the most crucial part of the
article. The equivalent would be putting a solar panel upright and saying it
gets more energ per SM than one laying flat. Seems pretty obvious.

------
aaronhoffman
Reminds me of this: <https://www.google.com/search?q=solar+panel+tree>

Which it appears now has been debunked.

~~~
moonchrome
I think when you type in that sort of stuff in to Google they should offer
advertisements for magic beans.

------
sbierwagen
Is it me, or have we been seeing more garbage stories like these since PG
disabled flagging for people who flag a lot?
(<https://news.ycombinator.com/item?id=3689185>)

------
veguss
You'd be blocking the view of someone else.

------
kappaknight
We must eat really different pancakes cause I don't get it...

------
ctdonath
Fresnel lenses come to mind. Another head-slapping moment.

