I must confess that I am of two different minds on the topic of efficiency. On one hand I am critical of the notion that efficiency can replace post carbon energy generation, yet I also have devoted a considerable effort to increasing the efficiency of the process of building nuclear power plants. In addition, I am conducting a personal case study of how to make my personal energy use more efficient. The contradiction involves the the fact that I some times consider adopting personal efficiency approaches that I reject when consider the proposals of the efficiency crowd. Lets consider the case of the 300 kg car. Julian Allwood and his Cambridge University associates have proposed radical steps such as the use of 650 Pound cars.
My inclination is to reject this notion out of hand, and I would were it not for the fact that I have considered doing just that for some time, and am presently considering an even lighter vehicle.
The whole idea strikes me as mega cool. So cool that we could name the electrical three wheeler the Apple! Needless to say there are some draw backs. The first is that the electrical three wheeler might not be safe, or at least safe enough, Can you imagine Ralph Nader writing an expose of the 650 pound car titled "Unsafe at any Voltage."
My concern rests on an analysis of a shopping trip in my spiffy three wheeler.
Now I drive to the nearest shopping center on Clinton Highway via Pleasant Ridge Road. a winding 40 MPH two lane artery, with less than great visibility.
Pleasant Ridge Road does not look safe for such a tiny, flimsy electric vehicle, does it? Not with cars that are more than five times more massive, not to mention the pick up trucks. So I face this quandary, I can get an electric three wheeler for under $2000. It is sort of cool, and will get me to the shopping center, where I usually shop. But I cannot convince myself that it is safe.In addition I have other concerns. My wife and I travel in our area. Our latest trip was to Norris Dam. Making such trips are quality of life issues for my wife and myself. Norris Dam is not far from our home, but we would probably need a vehicle with a 50 miles range to be comfortable driving there. A hundred mile range might be needed if we wanted to spend the day in the Smokies. Greater range means more batteries and greater weight. Only the first vehicle on this page might be remotely practical for such trips. It is a hybrid, and has a cost of perhaps $18,000 to $23,000. You can buy a lot more car for that sort of money, although a lot a lot better gas millage will come with the three wheeler. Bigger all-electric cares are possible, but they will require bigger batteries, and bigger batteries cost money and add to auto weight.
Thus the argument for the 650 pound car breaks down once safety and transportation range requirements are considered. A 650 pound or even lighter car might be possible for in town shopping trips, but will consumers be comfortable with their safety characteristics?
The energy efficiency question can be looked at from another perspective, applying efficiency to the production of energy.
My argument has always been that efficiency is the solution posed by most nuclear related problems. One reason for adopting Molten Salt nuclear technology, is its potential for efficient manufacture and efficient use. The Molten Salt Reactor is the reactor equivalent of the 650 pound car, but with out the safety hazards posed by Pleasant Ridge Road, and without the 650 pound car's trip distance limitations. In fact the Molten Salt Reactor can manufacture its own fuel, so potentially you can keep it running for periods of time up to 30 years.I have pointed out several times on Nuclear Green that the factory manufacture process makes more efficient use of labor, and that the limitation of factory manufactured large reactor is that they have to be manufactured as kits, with final assembly taking place on site. By shifting to smaller reactors, the number of pieces in the kit can be limited, so on site assembly does not require a lot of labor or time.
The cores of Molten Salt Reactors can be very simple and easy to manufacture, Molten Salt Reactor parts need not be built form exotic and expensive materials. It may be possible to build Molten Salt Reactors from composite materials similar to the composite materials that go into aircraft. Even when comity type materials such as steel are used in MSR parts, MSRs can be designed to operate at higher temperatures than conventional reactors, and thus will produce electricity with greater thermal efficiency.
One of my Nuclear Green readers "Engineering" recently commented on an old Nuclear Green Post,
Writing in the wake of the Fukushima events, I find it striking that the report speaks of “safety” without distinguishing between radiation exposure hazards inside the plant and massive release of radioactive materials into the environment. Avoiding massive external release is (a) more important, (b) the greatest MSR safety advantage, and (c) an unmentionable advantage in the already-risk-free Milton Shaw world."Engineering" is arguing that in MSRs greater nuclear safety is consistent with more efficient, low cost nuclear technology. Now that is quite a trick, but it is part of the beauty of the Molten Salt Reactor concept.
In conclusion, it would appear that efficient 650 pound cars face a rocky road, with safety and range problems, but more efficient nuclear technology via the Molten Salt Reactor concept is possible, and is consistent with improved nuclear safety.
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15 comments:
Charles Barton wrote:
I must confess that I am of two different minds on the topic of efficiency. On one hand I am critical of the notion that efficiency can replace post carbon energy generation, yet I also have devoted a considerable effort to increasing the efficiency of the process of building nuclear power plants.
There is no contradiction here. Good engineering has always been about doing for $1 what any damned fool can do for $3.
There was a time when it made sense (for example) to have automobiles that were not as efficient as those of today. At the time, fuel was cheap and the sophisticated controls to make cars significantly more efficient were expensive, heavy, or most often simply not available! Now fuel is expensive and controls are abundant and cheap, giving us cars that are much more efficient as well as safer, better handling, cleaner, etc.
The potential with the LFTR is expecially interesting -- the reactor should be cheaper to build AND more efficient thermally due to its higher operating temperature. The most exciting part is the fuel efficiency, where essentially 100% of the thorium coming in can be converted to thermal energy.
There will still be a trade-off of thermal to electric conversion efficiency and cost. It is always possible to get more efficiency, but it doesn't always make economic sense to do so. With the LFTR, the cost of fuel is virtually zero. This does NOT mean that thermal conversion efficiency will be low. Low conversion efficiency demands a larger reactor, larger turbine, larger heat rejection stage, etc. Thus good economic efficiency will demand good thermal efficiency, even though fuel cost is not an issue.
Charles - thanks, as always, for this post. Concerning "efficiency" - this is something I've been thinking about as well, since it's something of a magic word now. I have a couple of observations:
First, business and industry have always had reasons to improve their efficiency. Using less inputs for a product or process costs less. Robert Bryce in his book "Power Hungry" documents some of the very large improvements that have been made in engines, motors and generators since they first came into use. The early units were consistently very inefficient; some have improved by about an order of magnitude. Edison's original electric generators were terrible, for example.
Efficiency improvements have been gradual but very real. My overall impression is that now there isn't even a factor of 3 of improvement available in many areas, much less an order of magnitude, without major redesigns of systems, changing people's attitudes, or compromising safety and/or utility.
And the Jevons effect (commonly called the Jevons paradox; I don't find it paradoxical at all) has increased the number of things we do with our energy. To my personal benefit; in a lower energy society (I'm in Canada) I would not survive long because of my health. Our societal energy wealth keeps me alive.
A poster going by the name of Jerry said it perfectly on Rod Adams's post Are major “environmental” groups paid to help oil and gas interests make more money? at May 26, 2011 | 5:42 PM (Rod's blog doesn't provide a direct link to the comment):
Replacing an energy supply with “conservation” is like replacing food with fasting."
I can't add anything to that. But I do have a question. I keep seeing efficiency figures for turbines in power plants, with various numbers for exotic cycles like "super ultracritical steam" and other exotic processes. Do these numbers represent the thermodynamic efficiency of the generators, or are they the efficiency of the generator relative to the available thermodynamic efficiency? In other words: 600 Kelvin hot side and 300 Kelvin cold side gives a maximum thermodynamic efficiency of 50%. Does a 50% efficiency turbine give me 100% of that 50%, or do I only get 50% of that 50%? I've been assuming it's the former case, that the quoted efficiency is the overall conversion of the generation system. How confused am I?
On the issue of the safety of such lightweight cars I suspect they'd still be safer than bicycles, motorcycles and scooters (it wasn't uncommon to be able to drive some of them on motorcycle licences) so if they were cheaper to buy and run than a car they actually could improve safety if they replaced those things.
Of course that would require them to be cheap which you could do if you use internal combustion (e.g. a small two or three cylinder four stroke petrol engine) but not if you're using the most advanced battery technology to try to get long range.
It's also worth noting that there are different types of efficiency and different tradeoffs you can make, for example: you can use a lot of labour to avoid needing a power plant or you could use a lot of energy so as to reduce water usage, which specific tradeoff makes sense depends on the conditions and on what it is that is scarce and what abundant.
I should just note that on efficiency at using fuel a breeder reactor is at least a 50 times improvement over conventional nuclear, not many industries have that much improvement still possible nor are they likely to be able to get it as quickly as nuclear could.
Anon, if you are 68 and in poor health perceptions of safety differ from thos of younger and more spry persons.
Andrew Jaremko asked:
But I do have a question. I keep seeing efficiency figures for turbines in power plants, with various numbers for exotic cycles like "super ultracritical steam" and other exotic processes. Do these numbers represent the thermodynamic efficiency of the generators, or are they the efficiency of the generator relative to the available thermodynamic efficiency? In other words: 600 Kelvin hot side and 300 Kelvin cold side gives a maximum thermodynamic efficiency of 50%. Does a 50% efficiency turbine give me 100% of that 50%, or do I only get 50% of that 50%? I've been assuming it's the former case, that the quoted efficiency is the overall conversion of the generation system.
The efficiencies quoted are the thermodynamic efficiencies. I think an example would make it clear. Take the case of a large, state-of-the-art combined cycle gas turbine power plant with an efficiency of 60%. When it burns natural gas to produce 100 BTU of heat, 60 BTU of that heat goes to production of electricity, and 40 BTU of heat is lost in the exhaust, steam condenser, and other losses.
Note that for gas turbine power plants, the quoted efficiencies are for the lower heat value of natural gas, that is, the amount of heat available without condensing the water vapor formed during combustion. If the water vapor is condensed (as in high efficiency home furnaces), there is a "bonus" of about 10% extra heat available. The heat available with condensation is called the higher heat value.
Charles Barton
Anon, if you are 68 and in poor health perceptions of safety differ from thos of younger and more spry persons.
I don't quite see the point there, everyone has different perceptions of safety, the reality is that such ultra-lightweight cars would likely still be safer than two-wheeled transport (which is a common option for those who want to feel good about themselves as well as among those who can't afford a car).
Anon ones driving skills decline with age, and skill offers safety margins for ultra light weight vehicles. I suspect that this would be a matter of concern for safety authorities as well. Think of the uproar Ralph Nader created about the much heavier Corvair in the 1960's.
Skill offers safety margins for all types of vehicles (and are older drivers (or indeed any drivers) really any less likely to crash heavier vehicles?).
As for the Corvair, I thought that was mostly due to people over-inflating the front tyres.
Anon lighter vehicles rely on drives skills for protection, heavier vehicles rely on mass as well as drivers skills. The problem with the Corvair was the swing axil rear suspension.
I can't help but to promote slightly heavier EV's. The same determination to get LFTR's or MSR's built should be addressed for the LiFePO4 battery (lithium iron phosphate). It uses less lithium than li-ion, is inherently more stable (sound familiar?) and thus can be charged in an hour.
It has like 5 to 10 times the complete charge/discharge cycles to boot! It's only disadvantage is the requirement of individual cell balancing circuits.
I simply can not understand why it would have to always be more expensive that the lead acid (which is about three times the weight per Ah).
They need to be mass produced in robotic factories and charged with juice from the MSR's!
The lightweight electric vehicle seems ok for certain driving environments like dense urban areas that already have slow moving traffic. In San Francisco, small cars are popular because they are easier to park. The SmartCar can park in spots that would otherwise be too small for other cars.
Jason, the SmartCar weighs almost 1000 pounds more than the target 650 pound car.
donb - Thanks for answering my 'efficiency' question. It's good to know that the turbines and generators are extracting pretty much all of the energy that can be gotten out of a particular set of temperature differences.
The problem for the Corvair was naieve American drivers.
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As far as a 650lb vehicle is concerned, they already exist and can be readily purchased for very little cash. You can have a new one with a maufacturer's warranty. Most models are capable of startling performance, out accelerating nearly any supercar. They are easy to park, economical to operate, simple to repair should you want to do it yourself and have modest fuel consumption (low indeed when compared to the mobile chicanes that are pick-ups and SUVs). Visit the local Japanese motorcycle dealership while your regulation obsessive Federal govt still allows you Americans to. You'll be spoiled for choice.
Sione
Oh yes, should have added, I can get over 40 mpg even when riding somewhat agressively. Enjoyable and really very good fun.
I recently saw the new Jaguar luxo barge is getting over 50 mpg average. Now that car is a lardy tank of a thing with lots of un-necessary mass and plenty of "features" (many of which are completely un-necessary and of dubious value).
Imagine what is possible in terms of fuel economy if a seriously optimised effort to achieve it in a realistic vehicle is made. I'd expect to see over 100mpg. Oooops. Looks like VW are already there. That car hits the European market shortly. Likely it won't be available in North America though.
Point is tht efficiency is worth pursuing if one can be bothered. Kinda like curtailing un-necessary spending and saving instead of going deep into debt, then applying for yet another credit card.
Sione
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