4 ms·
"Basically the tree of cells are arranged in different angles so that as the sun moves some of them will always be receiving optimal sunlight when their normal
by uvdiv 15y ago
"Basically the tree of cells are arranged in different angles so that as the sun moves some of them will always be receiving optimal sunlight when their normal is parallel with that of the incident light."
Except it's trivially impossible to generate more energy like this (as he claims)! If a set of solar panels is independent and non-interacting (e.g., they don't shade or heat each other), then their total power output is simply the sum of their individual power outputs. And so their total energy outputs (integrated power) is the sum of their individual energy outputs. (Necessary distinction because their power peaks may occur at different times).
P_tot = Σ P_i
∫ P_tot dt = ∫ (Σ P_i) dt = Σ (∫ P_i dt)
E_tot = Σ E_i
If there is an unqiue optimal orientation for a single static panel (which under realistic assumptions there is) -- optimal in terms of maximizing energy output, E -- then the optimal orientation of a array of independent solar panels is just the same orientation, iterated. Combine inferior panel orientations, and their total remains inferior.
E_i < E_opt (for i <- 1..N)
Σ E_i < N * E_opt
And all those panel angles in his "tree", facing non-South, up, down, towards a wall... they are individually inferior to the single 45° south-facing panel in his static array. So combined together they are still inferior.
Where did his experiment go wrong? I'd start with the shade issue. The whole setup is in intermittent shade (note the tree shadows); and one experiment is sitting near the ground, the other is mounted on a pole. Looks like different shade environments. His output graphs show that the entire flat array is sometimes in total shade, at a time when the pole-mounted "tree" is not:
http://www.amnh.org/nationalcenter/youngnaturalistawards/2011/aidan.html http://www.amnh.org/nationalcenter/youngnaturalistawards/201...
Another fatal flaw (I had to look this up to check) is that he is measuring voltage, not power, and they are not linearly related in photovoltaics. Actually, the open-circuit voltage (what you get if you stick a voltmeter over a solar cell, when it's not hooked up to a load) is practically independent of irradiance:
http://i.imgur.com/SWGjV.png http://i.imgur.com/SWGjV.png
This from the solar module datasheet here:
http://www.bpsolar.us/products/3-series-solar-panels-polycrystalline http://www.bpsolar.us/products/3-series-solar-panels-polycry...
Open-circuit voltage going from 200 W/m^2 to 1,000 W/m^2 only increases from 34 V to 38 V. Power output, with a real load, would go up by about 5 times.
So, he never really measured energy production, or anything that remotely approximates it.
- toppy 15y agoThis guy is 13 ;)
- lloeki 15y agoAgreed with the experiment flaws, plus the article is way too shady to make anything even remotely reliable out of it. It reads awfully like "Child pwns scientists, saves world and his dog" Still, what if you consider a fixed volume as the constraint in establishing the comparison? For a flat panel assembly, a given volume would constrain the surface quite obviously. If you consider a tree structure one might be able to pack some more panels in the same volume, and Fibonacci might give us some solution about how to maximize panel density in the volume while minimizing shading interference from other panels and supporting infrastructure.
- sebbi 15y agoAnd how should that work? The sun is point light source, so the light comes from one direction only and you need to face your solar cells in exactly that direction. If you want to maximize the given volume a tree doesn't seem like the optimum ... covering the whole surface of the volume should be the optimum (to receive every reflected light). Also the tree has a lot more solar cells than this kids flat panel and he is still only measuring voltage.
- JoeAltmaier 15y agoCool analysis. Doesn't it make sense that an empirical test would not reach a theoretical max? For instance you've discounted shade effects as where he went wrong. Maybe its exactly the shade issue that makes his findings significant. Every urbanite will have to deal with it, and his array may do a better job in intermittent shade. If mass-distributed, most folks would not be optimizing anything - install-and-forget - so its a real solution to create something that works in most environments.