Nano-Storage, the Store-Gen Grid and Hurricane Ike

Hurricane Ike has given us a massive object lesson on the importance of implementing the late Rick Smalley’s vision of the Store-Gen Grid (SGG; graphic courtesy Wade Adams at Rice’s Smalley Institute) – a highly distributed network of granular electric production and storage.  One of the elements of the SGG concept is a household storage unit for about 100 kW-hrs of dispatch energy. 

 

Well, we ain’t there yet.  Of all the standard infrastructure services, only two seem to be reliable in a pinch: cell phones and natural gas.  The electric grid is plainly extremely fragile.  This is a major opportunity for nanotechnology.  With a major power outage in the energy capital of the world, this topic ought to get *lot* more traction, and fast.  So get your thinking caps on.  According to the Houston Chronicle, nearly 3 million people lost power due to the storm.  So I reckon there are about 3 million ready customers for the next big thing in distributed power.  I’m one of them!

 

Now, when considering storage technologies, energy density *really* matters!  Among practical materials, nothing is even comes close to gasoline or diesel fuel.  Just before the storm, my wife was wise enough to ignore my objections and bought a neat little Honda 2kW generator.  I got ten gallons of gas on Friday, and used about five gallons over a 36 hour period.  This was just enough to keep the refrigerator going, charge cell phones, and run a lamp, two fans and a small TV set.  This enabled us to essentially camp-out in our house.  Forget about air conditioning, running the washer/dryer or taking a hot shower (the darned water heater has an electric starter).

 

Here are some representative (volumetric) storage energy densities (from Wikipedia):

 

 

Let’s look at the Lead-Acid Battery (LAB) as an example, since it’s still the workhorse for storing electric energy.  My five gallons of gas would equate to 4,383 liters of lead-acid batteries (LABs) (3.8*5*34.6/0.15).  My total investment for generation and storage was $1020 ($1000 generator, $20 gas).  How much does 4.3 cubic meters of LABs cost again? – about $20-$50/liter?  And how much does it weigh?  I can (and did) carry (lug) the generator and the five gallons of gas myself at the same time. 

 

Overall, electrical storage energy density is worse than chemical storage a good factor of ten or more.  An order of magnitude (or two) is nothing to sneeze at!  It is plain that without sufficient oil/gasoline/diesel, we are in a world of hurt for the foreseeable future.

 

Each of the technologies listed above employs, or can be improved with, nanotechnology or nanostructured materials.  Let’s do a little math and get a handle on the nano-scale challenge involved here.  If gasoline has an energy density of, say, 35 MJ/l, it equivalently contains about 3.5 x 10^-17 Joules per cubic nanometer.  Modeling this as a parallel plate capacitor in vacuum with a 1 nm gap, you get the target energy density with a voltage difference of about 2.8 Volts.  If you use a decent dielectric like TiO₂ (k = 40ε₀) instead of vacuum, you only need 0.44 V.  About 1 V/nm is a pretty stiff electric field, but not larger than those considered routine for ultra-thin gates in the semiconductor industry.  This all seems pretty doable; making the nanowire connections to the outside world will be the tricky part; it’s probably a job for carbon nanotubes or maybe graphene.  Rick would have liked that. 

 

I hope somebody out there gets to work on this pronto!  Even at $100 / liter, it would be a useful technology.  When you get the cost down to about $10 / liter, you’ll be a bona fide hero, and a very wealthy one at that.