When Rube Goldberg is Your Systems Engineer: Wind-Solar-Batteries

Reprint from Alex Coram, Professor (Emeritus) at the University of Western Australia.

Reducing Emissions: Goldberg machines are not meant to be planning advice

Alex Coram is Professor (Emeritus) at the University of Western Australia and a visiting professor at Robert Gordon University and the University of Massachusetts.  He mostly works on problems in mathematical political-economy.

Rube Goldberg machines are devices for achieving some straightforward objective in a manner that requires great expenditure of effort and resources and is so fanciful and complicated that there is little chance of succeeding.  Their appeal results from the fact that they are the consequence of ignoring simpler ways of achieving the same result.  They also demonstrate the mathematical point that an unconstrained solution is better than a constrained solution.  They are about the last thing we should think about when faced with a serious problem.

Right now we are faced with such a problem.  The Intergovernmental Panel on Climate Change says that to reduce the possibility we will push the climate to a new trajectory anthropogenic emissions of greenhouse gases need to be cut by between 50 and 80 percent on current figures by about 2050.  They need to go to zero sometime after that. If this is not achieved temperature increases may vary from manageable to possibly over 4 degrees centigrade.  In the latter case the result would be large scale species extinction and possible economic collapse.  This is about as bad as it gets, short of maybe an asteroid strike or something similar.

No solution to these problems is simple, of course.  However, some are beginning to look a bit like Rube’s machines.  To see the point consider the following stripped down view of the options.

Plan A.  Follow Clausewitz’s dictum ‘in war moderation is madness’ and throw everything we have at it.  This means solar, wind, bio-fuels, nuclear the lot. Since hydro is difficult to expand I leave it to one side for this discussion.

Plan B.  Exclude nuclear and just use solar, wind and bio-fuels.

As soon as we try for plan B we complicate things by excluding the main potential source of low emissions expandable base load energy.

Suppose we try to get all the energy we need using solar voltaic. First we need land.  There are a lot of maps on the internet that give the total land required as reassuringly small dots that add up to about the size of Texas.  A better way to do it is to scale up solar installations like the Topaz plant in California.  From this we need about 200~km^2 for each average size 1 GWe power station we replace.  Imagine, for example, that the population of India uses about half current US energy per person.  In this case it would be necessary to cover between 10-20 percent of India’s land mass with panels.

To get an idea of the nature of the second problem just draw a horizontal line that represents a few days and draw average energy requirements as a line that goes up and down a bit.  Now draw some humps of about six hours wide once every twenty four hours.

What is apparent is that the gaps are bigger than the energy filled in bits.  And some of the energy is wasted because it is at the wrong time.  Depending what you want to assume about back up, there are periods where we may have to fill in by100 percent.

So let’s add wind to the diagram. Just draw a line that spikes up and down between the maximum and zero in a random fashion.

Is wind totally random?  As far as getting it to correlate with gaps in the sun, near enough. There is no reason why the wind should coincide with our sunshine humps.  Sometimes it adds to surplus when we don’t want it.  Sometimes it adds nothing when we do want it.

[Insert by BF Randall - direct comparison; actual data]

Another thing we might try is to fill in by burning  bio-mass like trees and bushes and grasses.  This also takes up a lot of land and there are issues with soil depletion and environmental loss.   A rough calculation on solar conversion for plants shows that if we use up about ten percent of US agricultural land we get about three to five percent of total energy requirements.  If we wanted to fill in for all solar and wind gaps we would need much more.

Why not spread solar out across a large land mass? In places like the North American continent this reduces the gap to maybe fourteen hours at a minimum.  We can do better across North Africa but we need to duplicate the solar plants and build the transmission grid.   Even so we still don’t come close to completely filling in the gaps.   And this still hasn’t done much for South East Asia.

We could try to use potential energy for storage by pumping water into high damns or even moving rail cars full or rocks uphill.   Water might work for small countries with high mountains.  In places like the US we would need to expand our storage about twenty-five times, and most of the best sites have already been used.

Instead of potential energy use kinetic energy from inertia by constructing giant flywheels?  This might help a bit but it is expensive and complicated.

Batteries might help some more, but we don’t have any of the capacity required.  Wait for them to be invented?  Clausewitz again.  Like Napoleon’s armies, nature won’t wait.

Off peak storage in electric vehicles?  Again it would help, but we don’t have the vehicles and won’t get them in the near future.

Changing consumer demand to fit the humps? Again, complicated.  Maybe people want to cook and watch television after dark.

At this point we might ask, why exclude nuclear anyway?   It isn’t more expensive and I don’t think cost is the central issue.

A sensible answer would have to be that the risks of including nuclear energy in the supply chain are greater than the risks of failing to make the required emissions cuts.  Let’s consider the risks of nuclear

One is accident.  Nuclear energy has dangers, in the same way as air travel or medical procedures or food supply, and it needs to be handled thoughtfully.   It is easy to exaggerate the risk here.  Although I wouldn’t take this as a good indication,  so far ­­deaths from about 15, 000 years (that is reactors times years) of commercial reactor operation are about zero.  If we want to include non-commercial reactors without safety features Chernoybl gives about 50 deaths with a projected addition of maybe 4, 000. For perspective well over a million people die every year on the road and about the same number from burning coal.

What is important, however, is not that the figures are small, but that the risks are controllable.

There is some risk associated with waste.   This also has to be handled carefully, but a lot of the concern misunderstands the quantities involved and thee technology.    The quantities are small and are usually stored on the site.  More importantly,  most current commercial reactors burn out about one percent of the energy contained in the fuel and then dump it.  With already available technology most of the remainder can be reused.  Put differently you could run a fast neutron reactor for about 100 years from what is currently called waste. This still leaves about a milk crate in volume of radioactive material per reactor per year.  This has a life of about 300 years.

What about proliferation?   From the viewpoint of spreading the technology the marginal increase in the risk of proliferation is small. Thirty one countries currently have nuclear reactors and most  major emitters are also nuclear powers.

A second proliferation issue is waste as weapons.  It has to be secured, of course,  but it helps matters that current commercial waste is the wrong sort of material.  Without going nuclear wonk you need a high concentration of PU239 for a feasible weapon and it isn’t practical to separate this out from the rest of the waste.

But there is always terrorism.  That is usually enough to win the argument, unless we stop to think what our terrorists are meant to do.

Flying a plane into a nuclear power station is a common fear. Let’s do a little arithmetic. Most new build reactors are similar to a Westinghouse AP 1000.  This shield building has a radius of about twenty-one meters so to get a direct hit you have a target of less than twenty meters wide maximum. This building is a reinforced concrete and steel structure with walls about 100 cm to protect it from missiles and aircraft and the core is protected by a one piece steel containment vessel about five cm thick. Chances of penetrating the containment vessel from a direct hit are estimated at zero.

In fact, if a terrorist were organized enough to steal something like a 747 completely laden with fuel and wanted to kill someone, there are many events that regularly draw crowds of over 100,000.  These are relatively easy to hit.  Even a Chernobyl style disaster wouldn’t come close.

It is sometimes thought that terrorists could steal spent fuel. And do what?  It can’t be used for a bomb.  Maybe it could be spread around as in a dirty bomb?    A problem here is that it is extremely difficult to steal the spent fuel and to include it in a bomb. Even then most studies show that the radioactive material would cause less damage than the blast itself.

What if a nuclear installation were attacked with rocket propelled military weapons?  Nuclear plants are shielded against this sort of attack.  Even under extreme assumptions it is a very low risk that any damage to the population would result.

To pretend that we have hard figures on any of this is, of course, just silly.  But it is difficult to find a good argument to justify the risks of using Rube’s machines as plans for emissions reduction.