I wrote:
Lake Meade, on the Colorado River, has a surface area of 620 km^2.
That's 620,000,000 square meters. It is arid, and solar energy
reaching the ground in North America arid places is about 500 W at
peak, or 1.5 kWh/m^2/day.
I believe natural algae photosynthesis efficiency is . . . what? 2%
overall? So that comes to:
18,600,000 kWh or 18.6 GWh. This is 86% of the output of a typical
U.S. nuclear reactor . . .
I could be wrong about that 2%. I am sure that algae grows better in
the heated, CO2 enriched ponds next to fossil fuel plants, that Jones
Beene discussed. In Chapter 16 of my book, I computed that plants
grown under ideal conditions in the Japanese food factories convert
as much as 15% of the light energy into food. This is light in a
narrow wavelength of PAR, and the atmosphere is enriched with extra
CO2. I doubt that a heated outdoor pond -- even one supercharged with
CO2 -- is as good as the food factory, so I suppose algae is
somewhere between 2 and 15%. It would be way better per square-meter
than using Lake Meade or some other unheated natural body of water.
However, if you want to tap solar energy, I think it would be more
efficient and cost-effective to make a 620 km^2 solar-electric
generator plant collection space. This is ~20% efficient, so it would
be equivalent to ~8 U.S. nuclear plants. You could put ~100 km^2 near
Las Vegas, and another ~200 km^2 near Los Angeles, and you would
eliminate their daytime demand for electricity, which is high because
of air conditioning.
Transportation consumes 26.52 quads, so if you could magically
convert nuclear electricity into transportation energy, it would
take 325 reactors.
I meant convert it into gasoline directly. You can use the nuclear
electricity in railroad commuter trains or plug-in hybrid cars, and
these are far more efficient than gasoline-powered internal
combustion engine-only cars. I suppose ~200 standard U.S. nukes that
produce 16 quads per year would be roughly enough for a fleet of
hybrid plug-in cars and trucks. You still need liquid fuel for long
distance transportation, so you use ~200 nukes for electricity plus
fuel from the algae grown at the ~250 existing fossil fuel plants
(nuke equivalent; actually we have more than 250).
You might use waste heat from the nuke plants, but there is no ready
source of enriched CO2 next to them. No fossil fuel, and they tend to
be far from cities, so no garbage or sewage either.
- Jed
