February 2, 2015

Are renewables low density/diffuse?

No, they aren't - not if you compare apples to apples.

Wind and solar generate a very high "density" form of energy, electricity: electric wires can carry very high energy density thousands of km, to where its needed.  On the other hand, wind and solar require a "catchment" area which is no larger than the overall land requirements for producing oil and other fossil fuels.  For instance, the US government leases about 35 million acres of land for a minority of US oil production (http://www.ewg.org/oil_and_gas/execsumm.php), and since 1982, the federal government has leased or offered 229 million acres of public and private land in 12 western states for oil and gas drilling, an area greater than the combined size of Colorado, New Mexico and Arizona.  Another way to look at it: the US has about 500,000 producing oil wells*, each of which requires access and working areas, as well as water disposal wells, etc. - these require a minimu of 1 acre per well, and perhaps much more.  There are about 120,000 gas stations in the US, at perhaps 1 acre per (some cities require a minimum of 1 acre).  The wells and gas stations add up to a minimum of 720,000 acres.

Of course, we also need to include 185,000 miles of oil pipelines - at 75 feet of right-of-way, that's 1.7M acres. Then there's storage, refinery and port facilities. Not to mention dry/abandoned/capped wells, of which there are probably several million.   - 2.5 million acres total for the US industry appear to be a minimum.

If 2,500,000 acres are required for 9M bpd oil production, that works out to about 20 watts per sq meter, much less than solar power.

Looks like oil is pretty low density!

What about Coal?

Estimate: Solar thermal energy requires about 16.4% less land than coal, and wind power requires about 96.3% less land than coal, to produce a given amount of electricity over a 60-year period.

http://www.sourcewatch.org/index.php/The_footprint_of_coal

Liquid petroleum fuel is energy dense and portable. Doesn't that make it hard to replace?

No. The perfect is the enemy of the good. Diamonds are the hardest substance know to man: does that mean they're essential for daily tasks that require hardness?

Plug-in hybrids like the Chevy Volt can reduce light vehicle consumption by 90% with no sacrifice in convenience, and do so cheaply. Electric rail can do the same for freight. Batteries can do for water shipping some of what batteries do for surface plug-in cars. Only airplanes present any real difficulty: for them efficiency and rail substitution under 500 miles can probably reduce requirements by 60%.

For the residual 10-15% of fuel requirements, there are several solutions, including fuel cells; synthetic fuel (from atmospheric carbon, waste water and renewable electricity); and biofuels. They would be more expensive (maybe the equivalent of $5-$10 gasoline to do properly, especially biofuels), but the greatly reduced consumption would make that matter very little.

Batteries etcetera are good enough!

Some followup questions:

What's the source of the numbers that say consumption would be reduced by 90%?

This is from GM's observation of a reasonably large sample of real-world drivers, which found that 78% of miles driven would be within the Volt's 40 mile electric range. The remaining 22% would be on the backup ICE generator, which would give roughly 50 MPG, a 50% reduction in consumption compared to the average 22 MPG vehicle on the road today. That gives you an 89% reduction in fuel consumption.

Does this just include consumption of oil?

Yes. Fortunately, PHEV's have an elegant synergy with wind power (see my most recent post describing how PHEV's help buffer intermittency), so that PHEV's will promote and facilitate wind. This means that one doesn't need to be too worried about the CO2 emissions from existing grid power (which would be less than a Prius in any case).

Aren't little details like having to plug the car in every night important to consider?

Think of the inconvenience of stopping for gas at a service station. If people really find it annoying, undoubtedly someone will devise an automatic docking procedure, like that of many cell phones.

What about pure electric vehicles?

I think the Volt serial hybrid design is the practical solution. The infrastructure for gasoline will be far more extensive than that of electricity for quite some time.

OTOH, pure EVs will work for some quite nicely.

What about Vaclav Smil's discussion of energy intensity in Energy at the Crossroads?

First, V Smil greatly underestimates wind resources and power density. He uses average wind speed over the entire land mass, a bit like estimating the average oil content of the earths crust or the energy in hydro electricity on rainfall/m^2.   Solar, wind, hydro, geothermal, tidal energy are all concentrated in specific regions so using average power density is meaningless.

2nd, he's not making a proper comparison of the whole system land requirement, as discussed above.

*The total number of producing oil wells in the U.S. increased at a steady pace in 2011, reflecting stepped-up drilling programs spurred by $100/bbl prices. World Oil’s estimate of producing wells, based on surveys of state agencies and company sources, indicates a rise of over 16,000 wells to 535,951. This is up 3.2% over 2010. http://www.worldoil.com/magazine/2012/february-2012/special-focus/2012-forecast-us-oil-well-counts-rise-in-all-regions

3 comments:

Michael said...

Hi,

This is the "mphtower" guy from Grist. I thought I'd respond to your comments here since the ones you posted on Grist seem to have killed the discussion. (Which, ironically, is a good thing--you posted a solid argument and that apparently brings the discussion to an end.)

I only want to disagree with your comment "plug-in cars can reduce light vehicle consumption by 90% with no sacrifice in convenience."

Can you tell me where you've found the numbers that say consumption would be reduced by 90%? Is this "well-to-wheel" consumption? Or is this just consumption of oil qua oil?

The problem I have with this argument lies in the clause "with no sacrifice in convenience." The first thing to consider is that EVs are more inconvenient than a conventional vehicle.

Little details like having to plug the car in every night are important to consider. It might seem petty, but think of how frequently cars are used and think of the varying dynamics of when someone wants to/has to use them. When you factor in considerations like a large load of groceries, dogs that are trying to scramble out of the car, elderly folks who need help, and any of the other myriad small situations that can hamper the short amount of time it takes to plug the car in, that convenience factor becomes much more important.

The other convenience factor to consider is driving range. Most people have a commute that's less than 50 miles per day, but usually more than 20 (if I recall correctly). This means that the average commuter will need to plug in every day. It also means that extended excursions will be out of the picture for most folks.

To make a plug-in car work there are two approaches that can be effective, as I see it. One is the Volt approach where there's a system which allows the owner to drive without plugging in. The other, and it's a long way off, is an electric car with at least a 250 mile range and the ability to recharge in less than 10 minutes.

That last point is critical. If you are on the way out the door to go to work and find out that you forgot to plug in last night and now have to find some other route to work because it takes 6 hours to charge your car, your ownership experience will not be too cheery.

Anyway, I'm enjoying what I've seen on your blog so far. Keep up the good work and the rational thinking.

- Mike

Nick G said...

"Can you tell me where you've found the numbers that say consumption would be reduced by 90%"

This is from GM's observation of a reasonably large sample of real-world drivers, which found that 78% of miles driven would be within the Volt's 40 mile electric range. The remaining 22% would be on the backup ICE generator, which would give roughly 50 MPG, a 50% reduction in consumption compared to the average 22 MPG vehicle on the road today. That gives you an 89% reduction in fuel consumption.

" is this just consumption of oil qua oil?"

Yes. Fortunately, PHEV's have an elegant synergy with wind power (see my most recent post describing how PHEV's help buffer intermittency), so that PHEV's will promote and facilitate wind. This means that one doesn't need to be too worried about the CO2 emissions from existing grid power (which would be less than a Prius in any case).

"EVs are more inconvenient than a conventional vehicle"

I was talking only about plug-in hybrids.

"Little details like having to plug the car in every night are important to consider."

True, but think of the inconvenience of stopping for gas at a service station. Further, if this is a serious problem, undoubtedly someone will devise an automatic docking procedure, like that of many PDA's.

"The other convenience factor to consider is driving range."

I think the Volt serial hybrid design is the practical solution. The infrastructure for gasoline will be far more extensive than that of electricity for quite some time.

I've added these to the Original Post.

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