I was recently presented with a supposed "scientific paper" that was
meant to prove that algae based biofuels were unscientific hokum and
snake oil. I was, to say the least, rather upset when I read this paper.
I am not a scientist and all the stuff about PAR's and joules and the
like was really confusing. But I think I managed to deal with all of
that and still find the false framing.

http://www.nanostring.net/Algae/CaseStudy.pdf

In the "study" we find the following pronouncement:

E is the Energy in the biomass
PAR is the energy from the sun
Q is the efficiencey of the conversion of sun energy to biomass energy

W = PAR * Q

All of this is well and good and reasonable. And then we have:

Photosynthetic organisms use 8 photons to capture one molecule of CO2
carbohydrate (CH2O). Given that one mole of CH2O has a heating value of
486kJ (486 kilo jules) and that the mean energy of a mole of PAR photons
is 217.4kJ then the maximum theoretical conversion efficiency of PAR
energy into CH2O is:

468kJ/(8 * 217.4kJ) = 27%%

For reasons known only to God and photobiologists, plants don't use
most of the light in sunlight. That's why plants are green. Plants
only want red and some blue light.

I've even suggested separating light for dual use solar, solar thermal
+ algae.

The green goes to heating the engine and the red goes to the algae.

This would also reduce the cost of cooling the algae in the summer
sun.

Bret Cahill

On Jun 28, 1:59 pm, Bret Cahill aol.com> wrote:

Nah.. you miss Trucker's point.

In the case given no mention is made of specific spectral absorption..
just white (sun)light in and white light out.
In this case the scientific debunker claimed 73%% wastage.

It's factored in for the final low efficiency.

Sounds better than Jerusalem artichokes.

Kind of the algae equivalent to Boeing Spectra?

Bret Cahill

"The Trucker" verizon.net> wrote in message
news:pan.2008.06.28.20.39.03.808648@verizon.net...

$4/watt Boeing Spectra concentrated-tracker PV is 40%%, $2/watt dish
Stirling is 31%% and NanoSolar is 15%%.

In other words, McCain needs to give the Stanford guy the $300 million
to develop that nanowire battery ASAP.

At $10 gallon that's better than strawberries.

Someone like Al Gore could care less if the unwashed masses starve.

Bret Cahill

On Sat, 28 Jun 2008 15:27:03 -0700, Bob Eld wrote:

On Sat, 28 Jun 2008 14:29:39 -0700, lorad474 wrote:

The Trucker wrote:

Basically it's not that easy.

When a molecule, any molecule, chlorophyll in this
case absorbs a photon of light it can extract only
the energy that it is "tuned" to. The excess energy
that may be in the photon is released as heat.