Efficiency of Energy Recovery from Trees

Hello Keith E Bowers:

you have explained a very complicated subject pretty well there!

If however you are thinking of 'rain-forest' which is mainly concentrated around the Equator. There is always some trees to absorb the sunlight.

Whether one chooses to test a leaf against a silicone cell for efficiency, I an not sure that would be beneficial?

I like your post though. It explained the hows and where-fors, and all the different angles this subject can be started from and, a lot of the possible pit-falls!

Take care and well done. I would have said what you did if my thinking was as clear! Which it isn't.

What I am actually wondering about is whether our current methodolgy for arrayng solar cells is more effective than that occurring naturally. Trees utilize a multiplicity of solar interceptors (leaves) somewhat randomly arranged (but often overlapping in view factor) to provide the surfaces for energy collection, while I am led to believe that solar panels for direct power production are typically single surfaces. Unless some means (such as parabolic reflectors) are used to provide greater efficiency of collection and focusing of the energy, it would seem to me that nature provides for more efficient collection of the sunlight.

Well that is a different question, in that it implies solar energy recovery per unit volume is your issue, while solar cells as embodied today are opaque and planar, so no light gets past them. Nature is "better" at capturing every last photon by its diversity of leaf shapes, arrangements, and heights per unit of volume of most biomes Habitats. however, that energy is captured for use by the"device " that captures it (the plant itself) in situ, as opposed to transmitting to a common conductor for collection,distribution, and remote use.

do not confuse these different problems. select the frame of reference for the problem, and then compare comparable frames.

some possible frames: % light energy incident on the leaf actually converted to chemical energy, vs same for a comparable pv cell;

amount of energy converted by leaf or solar cell per unit of receptor area; or per mass or per unit of consumeable (water/co2)

percent of incident energy captured per unit area; per unit of volume of array of leaves/pv cells;

etc etc etc.

Its important to not confuse arrangement of collector components for actual conversion process; capture does not necessarily equal conversion.

You obviously are thinking critically about this subjet guest, why not register and join CR4? I can see that you will add insight to our discussions here.

milo

Hi Milo,

This is a very interesting question, when I was a steam engine apprentice my tutor explained to me that by completely burning 1lb of anthracite in ideal conditions will produce between 14,000 and 15,000 B.Th. U's!

My physics teacher always told me that by burning coal we were extracting the sun power that went into producing the tree's/giant ferns ect to make them grow.

So I would expect that by burning wood/coal wood give you the answer to this qustion?

Spencer.

Hello Scapolie:

this is a very interesting subject.

I think the original poster was referring to NOW?

Checking the energy in coal is seeing how much energy was available 50/100 million years ago?

No insult intended OK?

What means, exactly...energy recovery?

Plants convert energy, expend energy and store energy. PV and other direct conversion solar technologies do not store energy.

What means, exactly ... "our current solar energy systems" (double entendre intended)?

Our "Solar energy systems" include PV, wind, hydraulic, hydrocarbon fuels, ...

What means, exactly ... greatest efficiency exhibiited by a variety...?

Given equal or optimum insolation, the primary limiting factor of any plant's (tree's) productivity is water.

So it seems you are going about it from the wrong angle. The notion of research of the kind you ask about is unfounded and unsupportable.

The truth is comparing solar panel (light to electricity) efficiency to a photosynthesis (light to chemical reaction) reaction efficiency isn't fair as the next needed step would require making the chemical reaction to electricity which will have more losses. Trees do "store" the solar energy, but the next step of making this into something such as electricity will have much more losses.

If you were truly to compare the two, it would be worth while including the efficiencies of fuel cells which can convert these chemical reactions to electricity and find if the combination of these efficiencies is better than solar panels. They're probably alot closer than you think.

You were interested in view factors though...Sounds interesting, but by comparing to trees may not be the correct approach. Just going by material values and trying to make a near blackbody according to this. Also, it might be interesting to change frequencies inside of this near blackbody from reflected radiation as solar panels operate for a range of given frequencies.

In your research for this subject you have probably encountered some interesting things with trees. Phyllotaxis is just one and may be worth fooling around with. I think I said earlier that this may not be the way to go, and thats because I was just thinking of stationary solar panels, but power stations panels follow the sun in the sky. This complicates matters to a new degree as the land mass covered by a single mirror changes with its orientation to the earth and I revoke my earlier statement.

However, this doesn't have to do with mirror view factors with other mirrors, just the mirrors optimal viewfactors with the sun, which is flat. If your goal is to improve the efficiencies of the solar panels themselves it isn't the way to go and better materials would be more worthwhile (as useable reflected radiation is pretty small and solar panel inefficiencies are do to the range of useable radiation), but if you're trying to minimize the land area of the power station (also a cost), cool idea dude. If you haven't heard of Phyllotaxis yet, comprehend it before you jump into this one. I would post a bunch of links, but this is something that requires a book and I don't know any single one good one on it.

To simplify all this, you are assuming that the geometry of the tree is so the leaves reflected radiation viewfactors can interact. This doesn't apply to solar panels, as the weakness is useable wavelength range, and in their usable range they are ridiculously efficient. The geometry also permits minimizing land area to follow the sun through the sky though, and for trees this is important for obvious reasons, some structural, some biological. Viewfactor reflection could be used if using different radiation range solar panels. So if there are two similarly highly efficient solar panels with greatly varying radiation absorbtion ranges then viewfactor reflection may make more sense with solar panels, but its better to just keep maximizing the range of absorbed radiation.