The Ergosphere
Tuesday, November 15, 2005

Peak what?

We've already seen peak US oil, and peak NA natural gas.  We may already have seen peak oil for the world, or it may hold off until turkey day.  But I keep seeing people who insist on using the term "peak energy" for this.

This term is misleading.  It's true that we don't have other resources ready to pick up where oil and natural gas are leaving off.  This is to be expected; oil and gas have been so cheap that it made little sense (greenhouse emissions and other pollution aside) to create a parallel infrastructure to substitute for them.

Right now we are getting toward the tipping point.  The production of crude oil either peaked last year, is about to peak (perhaps on Thanksgiving) or will peak by 2010; it depends whose crystal ball you consult.  Even US gasoline prices are getting high enough to move consumer demand from the large SUV segment (50% decline over 2004) to hybrids.  Does that mean this peak energy?

Oil only accounts for about 160 quads out of humanity's 400 quad/year energy consumption.  The remainder comes from natural gas, coal, biomass, hydropower, nuclear and the like.  At least two of those have substantial room for growth in world production in the relatively near future; extrapolating "peak oil" to "peak energy" is unwarranted.

On the other hand, transportation is still closely wedded to oil.  Does that mean we're about to see "peak miles" and a slow collapse of the economy as jobs and homes must be abandoned due to unaffordability?

Not on your life.  One of the biggest complaints about the US vehicle fleet is its inefficiency!  A replacement of the American vehicle fleet (~22 MPG average) with Prius-class vehicles (46 MPG highway, possibly greater city) would deliver the same miles from roughly half the amount of fuel.

We are already seeing some movement in this direction.  Over just a few months, many drivers have changed their vehicle of choice from a large SUV to a small SUV or even an economy car.  People drove slower.  For a given number of miles travelled, less fuel was needed.  These adaptations can only go so far, but they show that it is both possible to cut fuel consumption and that people will act to do it.

Suppose that a 50% improvement in fuel economy reduction in fuel consumption is the best we can do.  When we're all driving things as good as the Prius and oil falls to half its current production, THEN are we in trouble?

Not if we play our cards right.  The plug-in hybrid is coming; electric propulsion is already good enough to be offering 85% reductions in motor-fuel needs.  But that's not the end.  Radically improved batteries have been announced by several different companies, offering huge increases in power/weight (5 kW/kg), charge/discharge rate (100 C), and lifespan.  The inevitable outcome of these advances is an all-electric car which can go several hundred miles at highway speeds and recharges in 5 minutes.  Long before that, the same batteries will make hybrids more muscular than all but the most exotic sports cars.  The same advanced 5 kWH battery which could drive a Prius+ for 20 miles or so could also deliver enough power (500 kW!) to leave Corvettes in the dust.  If you're imagining a Miata with the power of a NASCAR racer, you've got the right idea.

The energy to run these cars will not be hard to come by.  The US auto fleet burned roughly 139 billion gallons of gasoline last year.  At an average efficiency of 17%, this amounts to 99.7 GW actually delivered to the wheels, or 873 billion kWh per year.  The wind in Texas alone could produce 386 billion kWh per year, or 44% of the total.  Efficiency of the electric vehicles will be higher, but losses will cut the available energy by perhaps 30%; regardless, the available energy is more than sufficient to meet our needs.

The available wind power world-wide has recently been calculated as 72 terawatts.  That's more than 5 times what humanity currently uses from all sources, and enough to give 8 kW to each of 9 billion people.

I haven't even touched on solar yet.  Humans use about 400 quadrillion BTU (quads) of energy per year from all sources; the Sun delivers this much energy to Earth in about 41 minutes.  Developments in the pipeline might increase the efficiency of PV cells from 15% to 60%, roughly 30 times as great as the most efficient higher plants.  Such cells would produce an explosion in energy availability and thus energy use, without pollution.

So:  Will we see "peak energy" in this decade, or even in this century?  We may well see a local maximum in the raw consumption curve and some slide in useful output, but as for absolutes in either.... not any time soon.

Good post with some important facts. Thanks.
Good catch, Nick.  Fixed in edit.
I haven't seen anything mentioned about how long it takes for the U.S. auto fleet to turn over. Even if every car sold in 2006 was a hybrid, how long before even half the cars on the road would be replaced?
Mark:  I've been seeing lifetimes in the 13-17 year range but I can't recall exactly where I saw them and I have no cites.

Stephen:  You need to use Google before asking questions like that.
I think you are getting a little overly optimistic here. For one, the thermodynamic limit for solar cells under one sun insolation is about 65 %. Research cells are unlikely to get there any time soon.

Similarly the intermittancy issues with massive wind deployment are quite horrendeous. If you think a capacity factor of 0.2 is bad now it would be far worse. The amount of storage you would need is massive. It far exceeds that of an electric car fleet. Even the grid Denmark is connected (Norway, Sweden, and Northern Germany) to only gets about 1.5 % of its electricity from wind. The Danes are literally building giant toasters to dump power when they have excessive production. The seasonal variations in power output are very significant as well. The difficulties involved with renewables are easy to understate.
@Robert: who worries about intermittency if we're charging large electric vehicles? The buffer capacity is in the tank, so to speak. [note: I should have read your comment more thoroughly) And if we're using ZAFCs or hydrogen, so much the better. If you've got "too much" electricity because there's a gale on, it's time to charge the car, cheap!

Or, on a bigger scale, fill the stationary ZAFCs. One can imagine that very windy places (the UK Atlantic continental shelf, Patagonia, Minnesota) would be exporters of zinc powder for recharges and importers of depleted zinc cells - trade would be the equalising mechanism.

I've been saying for years that we (in the UK) ought to put the fucked-up shipyard towns back to work and fix our energy problem by building offshore wind/marine power platforms. Hell, we're good at oil rigs, process control electronics and aircraft wings, and an offshore wind plant is essentially a wing (well, an aerofoil) spinning around on top of an oil rig, with some process control electronics.

Another thing I'd point out as a short-term fix is that if you have hydrogen, a lot of other things can be done with it besides burn it. We stick up a huge wind farm, electrolyse water, and use that hydrogen to make methanol (getting the carbon right from the atmosphere). That we can pour right into existing vehicles and aircraft with a tweak or two. It's less efficient, but it's not oil and it's carbon-neutral.
Robert:  The discovery of multiple-exciton generation in nanoparticles of semiconductors (the excess kinetic energy of a photoelectron knocks additional electrons loose) may bring efficiencies in the 50% range relatively soon.  IIRC, potential efficiency of 65% has already been measured in lab samples.

Aside from asserting a questionable ease of getting carbon from the atmosphere, Alex made many of the points I would have made (I love an informed readership!) but since he didn't do any numbers, I'll just have to be compulsive about it. ;-)

There are roughly 200 million cars and light trucks in the USA.  If they were all converted to electric and carried an average of 90 kWh of batteries (the Li-ion tzero carries 60 kWh, larger vehicles would need more) the total amount of storage would be 18 TWh.  Total electric generation capacity in the USA is a bit under 1 TW, so a full TW of power with no other outlet than a half-charged national fleet could be fully subscribed for 9 hours by just charging them to full.

You could do better than this by using weather forecasts to schedule your other generation; if the fleet averaged 1/4 you'd be able to absorb 13.5 hours of 100% output before having to put it elsewhere.

Also consider DHW.  80 million households times 80 gallons of hot-water tank is 1.6 billion gallons of hot water.  If each of these is allowed to drain to half-heated (with 50°F input water and 110°F output) at the time of the wind spurt and excess energy is allowed to overheat the tank to 140°F (cooled at the output with a tempering valve), the amount of energy involved is (40 gal * 30°F + 40 gal * 90°F) * 8.35 lb/gal = 40 kBTU = 11.7 kWh.  Times 80 million heaters, that's another 940 GWh, roughly another TWh.

Ice-storage air conditioning?  I've had no luck finding out how much electricity goes for A/C, but a system which can store enough ice for several days of demand could be a terrific dump load for excess wind power.

I'll bet you dollars to donuts that the European nations with grid-management issues due to wind aren't even using DHW as a dump load.
EP, I think I was thinking of methane as in comments on this one of yours. The Sabatier reaction to get methane. What's the position with regard to making methanol from methane?
That comment was actually by JimfromMich, not me.

The problem with alternate fuels which contain carbon is that you need to capture the carbon somehow, and that's a limiting step.  If you have a supply of relatively pure carbon dioxide from something else you don't have this problem, but pulling it out of the atmosphere where it's only about 370 ppm means handling a lot of mass and expending a fair amount of energy.

I understand that there are a host of catalysts to make different products from hydrogen and carbon dioxide.  That's the easy part; getting the carbon dioxide and hydrogen, THAT'S the problem.

If a given step (e.g. carbon capture) is expensive, the cheapest process is going to get the most out of it.  This is one reason why I'm so enthusiastic about the solar-zinc process; it not only leverages more energy out of the carbon than the carbon itself contains, the output is in forms which are particularly efficient (zinc-air fuel cells are about 62%, compared to the average gasoline engine's 17%).
That appears to be 1% capacity loss after 1000 cycles.  If you consider the battery to be useless after 50% of capacity is lost, that would be 50,000 cycles or 13 years and 8 months at 10 cycles per day.
Robert, you write "I think you are getting a little overly optimistic here. For one, the thermodynamic limit for solar cells under one sun insolation is about 65 %. Research cells are unlikely to get there any time soon."

Well, maybe it's not so optimistic. As E-P mentions, "The discovery of multiple-exciton generation in nanoparticles of semiconductors (the excess kinetic energy of a photoelectron knocks additional electrons loose) may bring efficiencies in the 50% range relatively soon. IIRC, potential efficiency of 65% has already been measured in lab samples." The applications of nanotechnology could be revolutionary for PVs.
Vehicle-to-grid isn't as useful with the first-generation PHEV's as it would be with full EV's; small batteries don't have the storage to level large load surges or sags.  It also requires infrastructure (SCADA systems, some grid hardware) changes beyond just DSM.

Agreed that V2G ought to be on the agenda and the upgrades should be scheduled for installation before there's a tzero- or Enigma-class car in every other garage.
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