I've been on vacation for the last two weeks, visiting relatives and touring the
western US in my Prius. And (incidentally) providing a fine illustration of
Jevon's paradox. Increased efficiency of use can, indeed, lead to increased use
of a resource. I probably wouldn't have undertaken the trip and burned all that
gas had I not had such an efficient and comfortable car to do it in.

I tried replying to a couple of posts while I was away, but for some reason,
those replies never showed up here. Not sure why. I was using a webmail
interface, but in the "sent mail" folder, it looked like they went out OK with
the correct header information for my e-mail account. Does Yahoo use IP address
verification on newsgroup posts?

One of the posts I tried to reply to was Sheila's query regarding the size and
viability of the western US oil shale resource. The resource is, indeed, huge,
but the situation as to its viability is complex. At a recent conference, I
spoke to an engineer from Shell who is working on their pilot project for
in-situ retorting and recovery of shale oil. The bottom line: one kilowatt-hour
of electrical energy translates to the (eventual) recovery of shale oil having
three kilowatt-hours of thermal energy.

That result can be looked at in several ways. The viability of the operation
becomes extremely sensitive to the method used for power generation. On the one
hand, conventional power plants using coal or oil to fire steam boilers are only
about 33% efficient. So if recovered oil is used to generate power for the
operation in that type of plant, it's totally and absolutely non-viable. All of
the recovered shale oil would have to be burned to generate the power consumed
in continuing operation. It becomes just a very expensive system for producing
waste heat.

The situation isn't much better if power is generated by more advanced power
plants representing the current state of the commercial art. Those use high
temperature super-critical steam and Kalina cycle turbines to achieve thermal
efficiencies of 40%. That means 2.5 kwh of thermal energy to produce 1.0 kwh of
electrical energy, which in turn yields 3.0 kwh worth of shale oil. So for
every 6 units of recovered shale oil, one unit is plant output, and 5 units are
burned in the power plant. That's a huge CO2 burden and extremely high capital
costs for a meager output of fuel. So that's a non-starter as well.

Things begin to look more interesting (from an oil company viewpoint) if the
energy is supplied by a modern coal-fired power plant. Assuming the same 40%
thermal efficiency, it takes 5 energy units of coal to get 6 energy units of
shale oil. The point is not that the output energy exceeds the input; rather
it's the effective conversion of solid fuel (coal) to a liquid fuel (shale oil).
The small energy gain is almost incidental; the operation is really a form of
coal-to-liquids conversion plant. It produces roughly twice as much liquid fuel
output per ton of coal input compared to a "conventional" CTL plant. (Of the
type, say, as operated by Sasol in South Africa). The amount of CO2 released
per barrel of output is approximately the same. The capital cost of the
coal-fired power plant + in-situ retorting operation is possibly less than the
cost of a conventional CTL plant of the same output capacity. One of the
purposes of the pilot plant is to develop a reliable model for what those
numbers really are.

Where things really start to get interesting is when wind and solar energy are
used to power the operation. Then there's no added CO2 burden for the oil
output, and all of the shale oil recovered is output. Moreover, the amount of
fuel produced is about six times larger than if the same input energy were used
to synthesize fuel from captured CO2 and water. Admittedly, nobody (besides
mother nature) is currently synthesizing fuel from CO2 and water, but there's
talk of doing so in the future. The size of the oil shale resource means that
direct synthesis is unlikely to be competitive for at least a couple of hundred
years. Not without a really sizeable boost from carbon offset credits.

Also significant is that the intermittent nature of the wind and solar resources
are, for this application, totally irrelevant. It takes literally years of
power input to the down-hole heating units to bring a large volume of rock up to
temperature for oil recovery to begin. All that matters is the amount of energy
poured into the rock. Whether it comes in steadily or in intermittent flows
matters nada. There's no need for electrical energy storage, so the system can
use the cheapest power available.

Once oil recovery is complete from a given volume of rock, then it's possible to
recover a goodly portion of the energy that was poured into heating the rock.
The pre-drilled hot rock becomes a prime geothermal resource. It can be used to
supply process heat of varying grades as well as dispatchable power on demand.
The recovered geothermal energy will of course be less than the energy that was
poured in over the preceding years, but it's reliable and "free"--given that the
wind and solar energy poured into the rock has already been "paid off" in the
form of recovered shale oil.

If the power input is limited to what can be produced by local wind and solar
resources, then the oil production will never achieve very high volume. Not in
terms of present levels of global demand. OTOH, it does give western Colorado
and eastern Utah a seemingly secure energy future. Probably secure enough to
thoroughly ruin the region with an influx of population. In fact, I saw it
starting to happen. Sigh!

Roger Arnold
Sunnyvale, CA

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