eSolar
The eSolar solution is the spies like us plan for power, and anything that invokes a pre Blues Brothers 2000 image of Dan Akroyd is good in my book.
They claim to scale in modules of 25 MW, so with a basic linear model for the amount of space one needs, assuming 100% energy transfer:
- The amount of energy incident on the earth at noon on a sunny day is ~100 mW/cm^2
- Based on a claim of 25 MW, this would require a raw area, (25^6/0.1)*(1/10000) = 25,000 square meters
- Based on the artist’s conception of these arrays, the packing efficiency is 75% (eyeballed), so the necessary area for 25 MW is 33,000 square meters. This is probably a generous packing efficiency, but it will suffice for now
- A typical medium to large city power plant is on the order of 400 MW, so this would be 16 * 33,000 = 528,000 square meters. This is roughly 0.2 square miles
Losses to factor in (not exhaustive):
- Radiative heat transfer
- Absorption losses in the reflectors
- Reflective losses in the concentration tower
- Heat exchanger losses from the concentrator to the steam turbine
So in areas that are sunny and where land is barren and cheap, this appears to be a feasible solution. Again, this is assuming perfect transfer and that their “revolutionary calibration algorithms†can keep everything pointed in the right direction all the time.
From what I understand, this 100 mW/cm^2 is a maximum: cloudy days cut this to ~10 to 20 mW/cm^2, and given angles and such, perhaps even on a sunny day 100 mW / cm^2 is only available for six hours.
The other big questions that stick in my head are:
Maintenance
- Sand + mirrors = scratching/wear
- Steam pipe arrays
- Cost of mirror finish vs. photovoltaic (no idea)
Backup and Storage
This is diurnal power, unless the concentrator is a “thermal battery”. Given the relatively high specific heat of water, though, it would take a significant mass of material X at temperature to continue to produce heat long after the sun has set. Another basic calculation for another break….