Friday, June 06, 2008

Amory Lovins and His Nuclear Illusion – Part Two (Big Plants vs. Small Plants)

Two days ago I began a series that critically looks into Amory Lovins’ and the Rocky Mountain Institute’s latest paper against nuclear energy. Today’s post discusses the claim that small plants (termed “micropower”) are turning in a “stunning performance” and are the way to go. There are two parts to this post: exposing the flaws in their “micropower” data and discussing the differences of big plants and small plants.

Does RMI’s data fit their definition?

From RMI’s condensed version:

Despite their small individual size, micropower generators and electrical savings are already adding up to huge totals.
After reading and researching RMI’s data, it is still unclear to me what size power plants RMI counts as “micropower.” Here’s RMI’s definition on page 11 (pdf):
1. onsite generation of electricity (at the customer, not at a remote utility plant)—usually cogeneration of electricity plus recovered waste heat (outside the U.S. this is usually called CHP—combined-heat-and-power): this is about half gas-fired, and saves at least half the carbon and much of the cost of the separate power plants and boilers it displaces;
2. distributed renewables—all renewable power sources except big hydro plants, which are defined here as dams larger than 10 megawatts (MW).
So I’m assuming that the size of “micropower” plants is 10 MW or less. The only problem with this is that the data and sources RMI uses do not tell you the size of the plants. According to the data from the 2005 WADE Survey (pdf) that RMI uses, there are about 300 GW of decentralized capacity in the world. The WADE Survey does not mention the average size of the plants included in their data. So basically we don’t know if the data includes all large plants, all small plants, or a mix. If RMI’s original source doesn’t tell us, how can RMI claim that the data is “micropower”?

According to data from Ventyx/Global Energy Decisions (NEI subscribes to their large energy database), the size of the average co-generating power plant in the U.S. is 54 MW. There are a total of 80 GW of co-generating capacity operating in the U.S. (same number reported in WADE’s 2005 Survey on page 27). Of the 80 GW, only 3 GW are less than 10 MW in capacity. Based on just the U.S. data, the majority of the co-generating plants don’t meet the size criteria of “micropower.”

Distributed (decentralized) renewables are the other half of the definition of “micropower.” The problem is that RMI’s data includes centralized renewables. RMI’s Excel spreadsheet shows that the world added 11,471 MW of wind capacity in 2005. According to page 35 of the 2006 WADE Survey (pdf), only 5 percent of this wind capacity is distributed:
On-site wind systems: according to the Global Wind Energy Council, 11,769 MW of wind capacity was installed around the world in 2005. WADE has assumed that about 5% of this is DE [decentralized energy] based, translating into 0.93 TWh based on an 18% load factor.
It seems RMI’s own data doesn’t meet its definition.

One more point. If “micropower” is supposedly turning in a “stunning performance,” then it is clearly not happening in the U.S. The chart below shows how much and what type of power plant capacities have been added in the U.S. since 1950. The chart also shows the average plant size built each year.
If “micropower” is recently turning in a “stunning performance,” then the average new plant size shouldn’t be as high as it is. The average plant size for the U.S. should at least be down in the 20-40 MW range, but it isn’t. The two times the U.S. has built a substantial amount of capacity during a short period of time also saw a scale up in the average plant size being built. RMI could argue that the rest of the world is flourishing with “micropower,” but their data so far hasn’t shown it.

The Virtue of Big Plants

From RMI’s condensed version:
Indeed, over decades, negawatts and micropower can shoulder the entire burden of powering the economy.
The keywords are “can shoulder” a big economy. It doesn’t mean the economy should be run by small plants. The fact is that big plants yield greater efficiencies and economies of scale than small plants. From page 59 in The Bottomless Well:
Bigger systems are easier to keep hot because they have less surface per unit of volume, and because they can be surrounded by materials like concrete and steel that can both contain and survive the heat. There is, of course, much more than that to engineering efficient power plants. But first and foremost, the rule is simple: bigger can be hotter, and hotter is more efficient. So, decade by decade through the first century of electricity, power plants grew bigger, and in so doing grew more efficient.
Amory Lovins and RMI proclaim the benefits of efficiency all the time. What is perplexing is why they would be against bigger plants considering bigger plants are more efficient than smaller plants.

Here are the numbers. According to data from Ventyx/Global Energy Decisions, of all U.S. cogeneration gas plants, those smaller than 100 MW have the lowest thermal efficiencies. Their average heat rate is about 11,600 Btus/kWh and their average thermal efficiency is 30.1 percent. Nearly one-quarter of the U.S.’ gas plants are 100 MW or less and their average thermal efficiency is 29.3 percent (includes cogen and non-cogen plants). Thermal efficiencies dramatically improve for gas plants greater than 200 MW.

Nuclear plants average a 10,400 Btu/kWh heat rate which calculates into a 32.7 percent thermal efficiency. Newer and bigger nuclear plants are expected to operate at greater thermal efficiencies nearly matching today’s combined cycle power plants. Mitsubishi’s 1,700 MW Advanced Pressurized Water Reactor is designed to achieve a thermal efficiency of 39 percent. Westinghouse’s AP1000 is designed for a 35.1 percent thermal efficiency. GE’s ESBWR is designed for a 34.7 percent thermal efficiency. And AREVA’s EPR is designed for a 36-37 percent thermal efficiency depending on site conditions.

From RMI:
Small, quickly built units are faster to deploy for a given total effect than a few big, slowly built units.
Well of course smaller plants can be built faster than larger plants. But how small are we talking about and is it practical?

As stated above, small supposedly means 10 MW or less. A new nuclear plant ranges from 1,100 MW to 1,700 MW. If we need 1,100 MW to meet demand, is it practical to build 110 small plants or just one big plant? If 1,110 MW was all that was needed, one could argue 110 small plants are practical. But 1,110 MW is not all that’s needed.

According to EIA’s Annual Energy Outlook 2008, the U.S. needs to build another 260,000 MW of capacity by 2030 to meet growing demand. It’s not practical to meet that demand by building 26,000 small plants when we can build 260 large plants - especially since larger plants yield greater efficiencies in the first place.

Now this isn’t to say small plants aren’t worthwhile to build. The size of the plants needed depends largely on the market demands. But when a country operates about one million megawatts of capacity like the U.S., a lot of small plants simply are impractical to build. Especially when one large plant like a nuclear plant is small compared to the overall market it serves.

If economies of scale and greater efficiencies do not exist with bigger machines, then the wind industry would still be building kilowatt wind turbines instead of megawatt wind turbines. Contrary to what RMI believes, there is no one-size fits all solution.


Anonymous said...

If large power plants apparently have a high efficiency, how come that large, inflexible nuclear power plants only have an efficiency of 33% (not including distribution losses) and flexible, combined heat and power plant an overall efficiency of over 80%?

Why use the electricity generated in a large power plant to power wasteful electric heaters, when one can use the waste heat of a smaller plant directly?

Anonymous said...

How come the small, flexible 0.05 MW combustion engine in the Toyota Prius has a higher efficiency than a inflexible 1600 MW nuclear reactor?

Kirk Sorensen said...

My guess would be higher heat of combustion. Basic Carnot principles.

Anonymous said...

A CHP (combined heating power) plant does not produce electricity at 80% thermal efficiency. It just uses the waste heat to do things such as heat water. You cannot compare the "efficiency" of a CHP to a NPP: that's just misleading.

The prius will get an optimum of 30-35% thermal efficiency, that's nothing special of an internal combustion engine, especially one of such small displacement.

I will say that NPP efficiency is nothing special. Super critical coal plants achieve 45%. Natural gas combined cycles achieve 50%+.

Luke said...


"Combined heat and power" is simply referring to re-using the waste heat from any thermal engine, and thus increasing the overall energy conversion efficiency of the process.

You can apply that idea to any thermal engine using any heat source - natural gas for example, or coal, or a nuclear reactor - it doesn't matter.

It's just as feasible to, say, capture the waste heat from a nuclear heated Brayton cycle gas turbine in an organic Rankine cycle, or something similar, as it is for a natural gas burning Brayton cycle plant.

What is the actual thermodynamic efficiency of the Prius's gasoline burning internal combustion engine?

Charles Barton said...

Two observations:

First you have demonstrated that Lovins relies on an incoherent data set. That is a data set which does not conform to stated data criteria. In other words Lovins fudges to arrive at his conclusions.

My second observation is that that several Generation 4 reactor concepts are capable of producing high thermal efficiency from small reactors. The trick is to use alternative coolants, helium or fluoride salts. rather than water. Heat can be transfered to closed cycle gas turbines. These small Generation 4 reactors have numerous advantages over large Generation 3+ reactors, and could be factory built at a much lower cost than current reactor construction costs. At present Westinghouse has invested in the South African project to develop the Pebble Bed Modular Reactor, and at least one other reactor manufacturer is considering an investment. I discuss the case for small reactors here:

I elaborate this discussion in a number of May 2008 posts:

Anonymous said...


If you are referring to Exelon's brief venture into PBMRs, that's been over. They pulled out of that business.

I would be surprised to see any commercial gen4 reactor completed in the united states before 2030. I'm all for nuclear, but I'm just being realistic.

Charles Barton said...

Anon, the South African PBMR is still very much alive. The project has a large staff, and has backing from Westinghouse.

Mitsubishi is mulling over whether or not to join the venture.

Bermuda is a candidate for PBMR technology once the reactor reaches the production stage.§ionId=60

Anonymous said...

The Prius is running now and has a peak efficiency of 37% at 0.05 MW.

How many nuclear power plants running now have a higher efficiency and the same flexibility?

How many nuclear power plants currently distribute their waste heat instead of wasting it in the cooling tower?

Why do you prefer to power wasteful electric heaters instead of using the waste heat from the combined heat and power plant?
Or don't you need hot water in your household?

David Bradish said...

The Prius is running now and has a peak efficiency of 37% at 0.05 MW.

Ah yes...I guess we should rely on cars powered by oil to meet the world's energy demands. What a great idea. What's the price of oil right now? How many Prius' would it take?

Anonymous said...

Reaching high electrical efficiencies below 200 MW is peanuts.
But better than a Prius engine is a biogas powered 0.5MW combined cycle thermal plant available now and installed in a few weeks in thousands of locations at the same time with an electrical efficiency of 40.4% and a thermal efficiency of 44%.

Still better than having to wait for new nuclear power plants reaching electrical efficiencies of over 40% with waste heat recycling included.

Keep in mind: People only need electricity and heat and biological waste is produced anyway. And Methane produced in biological waste is a potent GHG, which is better turned into 21 times less potent CO2 than released directly.

Btw, Toyota produces about 10 Million cars/engines a year. With an average power of 0.1 MW that's 1000 GW every single year. Just in case you want to tell us, that it is physically impossible to build and distribute thousands of biogas engines every year.

Kirk Sorensen said...

Who is this, Amory Lovins? "Biogas-powered"...and let me guess, the backup plan will be natural gas, right? Where are you going to get your biogas, hundreds of farting cows?

Joseph Somsel said...

I must say I'm a bit surprised at the claimed thermal efficiencies of the new reactor designs.

There are two hinge points in the design. First, the steam temperature and quality. These are pretty much fixed by the thermodynamic properties of water and we're seeing no change.

The second is the condenser cooling water temperature. New plants are using cooling towers and cooling ponds in the US. These run at higher temperatures than typical ocean cooling, now banned. Some site designs can achieve reasonable condenser cooling water temperatures (<100 deg F) but higher temps to 120 deg will be more typical.

There are two areas of possible improvement to improve efficiency. One is the low pressure turbine last stage blade size. These are transonic and difficult to design but improving. The second is increased investment in feedwater heater stages.

Still, 37% efficiency is difficult to credit for a LWR. Great if someone can do it but I'll have to hear more before I can believe it.

KLA said...


Waste-heat or efficiency are simply strawmen when it comes to nuclear power. It makes about as much sense as to argue wind power vs. solar flux and THAT efficiency (probably too low to measure).
Waste heat does not contribute to global warming. Compared to the overall solar flux it is just too insignificant.
Efficiency numbers ONLY make sense in regards to greenhouse gas production. The Prius engine produces CO2, so does every natural gas plant. Nuclear simply does not. Biogas should be used, agreed, but the amount is too low to make a dent. So you are forced to fall back on natural gas (methane). With leakage rates during production and distribution, and methane being 20-50 times as potent a greenhouse gas as CO2, relying on natural gas means equaling the greenhouse gas forcing potential of coal. See:

Kirk Sorensen said...

Why was ocean cooling banned? (it's about the best thermal sink on Earth!)

Stephen said...

33% effeciency is not so bad for complete cycle effeciency of a single cycle steam turbine system. You really can't do too much better without going to a combined cycle system, which is certainly possible with nuclear energy. Today's reactor temperatures really don't lend themselves to an air turbine - steam turbine system. The new Gen IV reactors, however can do better than that.

As far as "flexible" combined heat and power... The really high effeciency you get with that comes from the fact that a large portion of the energy is used directly as heat, so you sidestep the whole thermal engine thing which is always lossy by its very nature.

AS for the "Small, flexible" engine of the Toyota Prius... well, the combustion engine of the Prius is a standard small block gasoline engine. The thermodynamic effeciency of an internal combustion engine tops out at about 33% also. It's rare for an engine to really get that in practice though. A stock consumer engine will not generally do more than 20% thermodynamic effeciency under the best conditions and a lot less under less than optimal. (and not to mention all the refining that goes into that gasoline)

So sorry.. you loose there.

Actually as far as being "inflexible" nuclear plants can be used for district heating, just like any other kind of heat source can.

If you want to do the "distributed" thing you could do that with small nuclear reactors too. You could do it with the pebble bed reactor or the SSTAR or other designs.

Why would you want to though? It's less economical. It's the same for just about every other power source too.

"Distributed" energy solves no problem. It's just as dirty for one big power plant to burn coal then a thousand small ones. It's just as clean for one big reactor as one thousand small ones. The difference is that it's more of a pain to deploy.

Joseph Somsel said...

The use of natural bodies of water as heat sinks for power plants was banned by the EPA in 1972. Plant applications since then have to specify cooling towers, water-to-air heat exhangers, or artificial bodies of water.

The latter are increasingly popular since with enough land they can provide lower condenser water temperatures which provide higher efficiency. Owners will use artifical lakes or cooling canals as at North Anna, South Texas Project, or Turkey Point.

Kirk Sorensen said...

That's interesting Mr. Somsel--could you point me to more specific language concerning this? (thank you so much)

I assume that existing plants were "grandfathered" in this regulation...

Anonymous said...

In fact the peak efficiency of the Prius is 37%.

But better than a Prius engine is a biogas powered 0.5MW combined cycle thermal plant available now and installed in a few weeks in thousands of locations at the same time with an electrical efficiency of 40.4% and a thermal efficiency of 44%.

This biogas powered combined heat and power plant is - as opposed to the Gen IV reactor - commercially available now and far cheaper per kW than even a current reactor.

Where can one purchase a small, affordable nuclear reactor? And can it be shipped to Iran as well?

David Bradish said...

Anon June 10, 2008 4:36 PM, can you provide the link again, it was broken off? Just split it up when you repost or turn it into a link. Thanks.

Anonymous said...

David Bradish said...

Anon June 10, 2008 5:04 PM,

Are you kidding me? How can you seriously link to a one-pager that's in German? Does it look like we speak German here? Please provide something other then this to back up your claim.

KLA said...

David, I read it. It's simply a regular internal combustion engine running on gas, coupled to a generator. Attached is an exhaust heat exchanger for some thermal heat recovery. Basically identical to any natural-gas powered emergency or off-grid generator. Nothing I found in the link (or the company web-site) points to some new breakthrough in the production of that biogas. The product literature seems to be geared to small to medium sized dairy- or feedlot cattle operations to supplement their energy use. The only thing new is hyping a gas powered generator as breakthrough green technology.
The VW heating/power concept they had a few years ago was much better in that respect. They used a small diesel engine, driven by heating oil (or biodiesel), to directly drive a heat pump, a generator and use the exhaust heat and cooling system also for home heating with higher efficiency than regular oil burners.

robert merkel said...

In any case, thermal efficiency is, while not irrelevant, very much a second-order issue.

The key question is how much the power coming from your plant costs, and how much environmental damage is created in the process.

Geothermal plants, as I understand it, tend to have very low thermal efficiencies because the steam they use isn't nearly as hot as coal-fired or nuclear steam turbines. Does this matter? Not really. When your steam source is free, who cares?

And so it is with nuclear. When your fuel is so cheap (even with today's uranium prices), if the construction costs of a slightly less efficient plant are lower, it might make more sense to burn a bit more uranium.

In any case, anonymous, would you like to do a comparative life cycle emissions analysis of a) using that biogas, or b) running a nuke to generate energy, and simply burying and covering the biomass to sequester the carbon? Option a) is carbon-neutral (modulo the escaped methane), option b) is carbon-negative.

udo stenzel said...

To the anonymous coward: Cogenerating nuclear power plants exist everywhere in the world, but not in the US. Since you are apparently German, you should know, as one such plant was at Lubmin and provided heat to the city of Greifswald. It was shut down for ideological reasons (it was Soviet technology, but not an RBMK) and its heat output was replaced by... no, not biogas or hot air produced by wanna-be energy experts, but a filthy coal boiler.

A cogenerating NPP can claim to achieve a total efficiency of 80%, too, but the calculation is stupid, as it counts heat as if it was mechanical work. If low grade heat is all you need, you could drive a heat pump with electricity from a cogenerating NPP and achieve 200% efficiency, which is even more than the aforementioned coal boiler at ~100% efficiency. Try to beat that with micropower. But how do you compare an NPP to a Prius anyway if one burns uranium and the other gasoline?

Anonymous said...

David, Excellent website and discussion...and thanks for the detailed analysis of Lovins' rather shoddy research.

However, I believe an assumption you made in Part Two is not correct - i.e., "So I’m assuming that the size of “micropower” plants is 10 MW or less." It seems clear that Lovins is treating all non-hydro renewables which generate electricity or heat/steam (e.g., from wind, solar, geothermal, biomass, etc.) as sources of "micropower". Lovins also qualifies small hydropower projects as "micropower" if they have a generating capacity of 10 MW or less.

Jim-Bob said...

A few things about Nuclear Power.

I wonder why so many people concerned about climate change (although this is changing) are against nuclear power? It really is the best solution. One silly argument I have heard (but only versus nuclear) is that only 27 percent (or whatever figure people think it is) of our total energy is electricity, so going nuclear won't help. This would invalidate solar and especially wind almost as much as nuclear. You can't have a windmill on top of your car!! But, if people go more to electrical cars (or hybrids) then the percent of energy used as electricity will go up!

A second point is that we have huge amounts of waste from nuclear WEAPONS that we have to dispose of already. Doubling the number of nuclear plants and running them for 50 years will still produce much less waste than we already need to dispose of.

People ignore the fact that all forms of energy generation have risks (dams bursting, falls from solar panels while cleaning, fires, explosions) and that if we don't use more nuclear we will use "clean" coal (my ass) and oil/gas which put CO2, chemical pollutants and carcinogens, soot, AND radioactive particles in the air in huge quantities daily.

The last item is: How cool is this?

May be available commercially in a few years. So if you want small dispersed plants, use these: