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Study: Steam Hybrids Using Waste Heat Recovery Could Reduce Fuel Consumption Up To 31.7%

Steam1
Results of the study indicate that a steam hybrid using exhaust waste heat could reduce fuel consumption by up to 31.7%, depending upon drive cycle and vehicle.

A study by researchers at Loughborough University and the University of Sussex, both in the UK, has concluded that using waste heat from light-duty vehicle engines in a steam power cycle could deliver fuel economy advantages of between 6.3% and 31.7%, depending upon drive cycle, and that high efficiencies can be achieved at practical operating pressures.

The basic concept of the “steam hybrid” system is that energy is recovered from the exhaust in the form of a steam/water mixture. Shaft work is produced as steam is expanded, and is used in one of three ways:

  • To add torque to the internal combustion engine (ICE) output, thereby reducing fuel consumption and emissions; or

  • To drive an auxiliary power unit (APU) if the energy is not required by the vehicle (e.g., during braking or idling). Excess energy can be used to generate electricity and charge an electric storage system; or

  • To provide all the required torque to the drive shaft resulting in zero-emissions driving in inner-city areas.

The study, which is part of a larger investigation of the controllability of energy recovery, modeled a steam hybrid vehicle using two toolboxes: the Quasi-Static Simulation Toolbox (QSS-TB), developed at ETH Zürich, and the Powertrain System Analysis Toolbox (PSAT), developed by Argonne National Laboratory.

For a base vehicle in QSS-TB, the researchers used a VW Golf with a 1.6 liter engine; for PSAT, they used a Honda Civic with a 1.8 liter engine. Both vehicle models were run against the New European Drive Cycle (NEDC); the US FTP-75 Urban Drive Cycle; and the US06 Highway Drive Cycle

Results showed an improvement for both vehicle across all three drive cycles, with the greatest gain in the FTP-75 cycle, and the least with the aggressive US06 cycle.

Subsequent work for the research will include optimized controls for different style of driving, and further work on optimizing the heat exchanger. The design of the heat exchanger will be evaluated in an experimental set-up in which the exhaust gas is generated by a 7.2-liter Caterpillar engine.

In further developing the control architecture, the researchers are using four objectives:

  1. Power/torque. The power or torque demanded from the vehicle driver needs to be met by the ICE, the steam expander, or a combination of the two.

  2. Fuel consumption. Fuel consumption needs to be kept at a minimum.

  3. Steam supply/reserve. The supply of water to the heat exchanger needs to be kept constant to ensure there is a constant steam supply, or at least a reserve of steam for the expander.

  4. Steam quality. The steam supplied to the expander is required to be superheated so that it contains no water droplets which could be potentially damaging to the expander. This will be achieved by raising the temperature of the cold side fluid beyond saturation and ensuring it is superheated at entry to the expander.

The work is supported by the UK Engineering and Physical Sciences Research Council.

BMW and Honda are both investigating the use of waste-heat powered steam systems to enhance fuel economy. BMW’s onboard water/steam-based cogeneration cycle is used to power the vehicle’s accessories, rather than a traction battery pack (earlier post).

Honda is actively exploring the use of a Rankine cycle co-generation unit to improve the overall efficiency of a hybrid vehicle by recapturing waste exhaust heat from the internal combustion engine and converting it to electricity to recharge the battery pack. (Earlier post.)

Canada-based Clean Power Technologies Inc. (CPTI) is developing a waste-heat powered steam hybrid system—CESAR, Clean Energy Storage and Recovery)—that it claims has shown an up to 40% reduction in vehicle fuel consumption in initial test results. The system is under development by a wholly-owned CPTI subsidiary, Clean Power Technologies Ltd. (CPTL), which is located in East Sussex, UK. The Clean Power Technologies system was developed by Fred Bayley, Professor Emeritus of the University of Sussex.

CESAR uses a heat exchanger to capture waste energy, which is then stored in the form of steam in an accumulator, for on-demand use either in the same primary engine, or in a secondary vapor engine. Power can be produced solely by the secondary vapor engine even after the primary combustion engine has shut down.

The test program using the system included a generic model of an accumulator, supplied by Clean Power’s collaborative partner Doosan Babcock (previously Mitsui Babcock). The CESAR system has been running in parallel with a Caterpillar C18 diesel engine within Clean Power’s test facility in Newhaven, East Sussex since mid-October 2007. Clean Power is now re-designing the second generation of the steam accumulator which will be lighter and more efficient.

In March, CPTI contracted with steam technology specialist Dampflokomotiv-und Maschinenfabrik DLM AG (DLM) to act as a consultant for the further development of the CESAR technology. DLM, a specialist in the development of modern steam traction systems, will provide consultancy, design engineering and stress test related services.

CPTI has entered into a first stage collaboration agreement with Safeway Corporation for the purpose of data collection and to undertake preliminary design work for the steam refrigeration units for the grocery trucks. CPTI has also entered into a collaboration agreement with Voith Turbo Gmbh & Co. KG of Germany to jointly develop a reefer engine.

Resources

  • Sandra Hounsham, Richard Stobart, Adam Cooke and Peter Childs (2008) Energy Recovery Systems for Engines (SAE 2008-01-0309)

  • M. Kadota and K. Yamamoto (2008) Advanced Transient Simulation on Hybrid Vehicle Using Rankine Cycle System (SAE 2008-01-0310)

Comments

tom deplume

This is something new? At the Henry Ford Museum is a hybrid gas/steam electric power plant that was used at the River Rouge factory. Since the efficiency of a gasoline engine in the early 20th century was so low this system doubled the amount of kwh per gallon of fuel.
There was also a prototype steam car in the early 1920s that used a two stroke engine as the burner and to power the electrical system. Not only was waste heat from the 2-stroke used but the exhaust gases were burned in the boiler.

SJC

I do not think it is new. What is new is the application viability in view of increasing fuel prices. Just like tar sands, it was not worth doing before. You have to wonder how much energy has been wasted because "it was just not worth doing".

ai_vin

People are looking at this as a way to put lost energy to work but as it stands it's not the best way. The best way is not to waste it in the first place.

I could see this as a good idea if it was an 'after-market-add-on,' something you could fit to all the IC engines that are already out there, but this looks like something you need to "add-on" at the car's design stage. As such it's just another way for the 'Powers-That-Be' to prolong the status quo.

If you're going to go for efficient use of energy at the design stage you should design an EV not an ICE with even more high tech junk on it.

ai_vin

PS I mean just look at the numbers - a steam hybrid improves your car's efficiency by 40%. That sounds like a lot but an EV is already 300% more efficient.

SJC

There is a phrase that goes something like "do not let the perfect be the enemy of the good". The idea is that there are 140 million ICE vehicles out there. HEVs are less than 3% of sales. Even IF that increases to 10% of sales, 9 out of 10 of the new vehicles sold will still be ICE vehicles.

I hear people say that we SHOULD do this and we should do that. Should is a philosophic word that lives in a hypothetical perfect world. There is nothing wrong with keeping the perfect in mind as a goal, but realism plays a part as well and it is not "giving in" to less than what we should achieve. If you wait for the perfect world, then a lot of good does not happen and that is decidedly NOT perfect.

ken

Nobobody has mentioned the Stirling engine. Can't one of these very simple engines be bolted onto an exhaust manifold. Watever happened to the TIGER system mentioned on this site a few years back?
If this system is at all viable it should be retrofited on diesel locomotives (preferably biodiesel or NG powered) where it would yield the "biggest bang for the and then buck" first before trucks and buses and then autos.

SJC

The TIGER system is advancing, there was an announcement just the other day on it here. Stirling engines can be good, but to be efficient they need a large delta T between the hot and cold sides. The manufacturing tolerances are pretty tight because the working gas in high performance models is sometimes helium, but CO2 might work in this case.

I think it is a matter of cost and efficiency. Stirling engines can be used in reverse for cooling as well. Just oscillate them and one side gets cool and the other side hot. They are working on those to replace ACs. Again, they cost more than AC compressors and the AC compressor business makes millions of units.

As the AC compressor comes off the belt and is motor driven, we may see a push to make them Stirling engines. If you think how inefficient an AC compressor is you see why. It runs on the belt most of the time clutched out and you use it a few hours now and then. Just being on the belt free wheeling causes energy loses.

GreenPlease

@SJC

I thought the problem with stirling engines is their low specific power? Also, in order to achieve a large deltaT, a large heat exchanger would have to be used which would have an aerodynamic impact. Same problem with organic rankine cycle I guess.... the only solution I've seen is the centrifugal condenser used by Cyclone Power Tech.

How about this:

Say you have a decent size I4, 1.8L, that is transversely mounted (quite a few of those). The engine block would be made of aluminum and it would be made such that three additional cylinders could be positioned on the firewall side. These would be heat recovery cylinders. An overview would look like this-

0
0
0
0
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The exhaust manifold would pass over and then through the engine block again on the backside of the three heat recovery pistons so that the overview would look like this-

0 0
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0 0
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0 0
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This would allow a great deal of contact between the heat recovery cylinders and the exhaust gases. The heat recovery cylinders would be filled with water and would act as a self contained fully condensing steam engine.

TE might only be on the order of 10%, but it would be cheap and provide more than enough power for accessories and possibly trickle charge the battery of an HEV.

SJC

There are concentrated solar thermal stirlings the size of a break box that turn out 25 kw, but they cost a fortune and take 1000f to operate. They have used them in space probes because the cold side can be space. The condenser for rankine cycle is not much of a problem. It is a matter of how much rejected heat and air flow.

Interesting idea there, I am assuming that the 3 cylinders are stirling cycle?

One interesting aspect of the stirling cycle is that it took them more than 100 years to begin to figure out how it actually works. The whole regenerator apparatus between the sides was a mystery. They understand more and have modeled it, but it remains an example of what works, works.

John

@sjc

There are of course losses attributable to A/C compressors, however, the refrigerant loop typically provides for more than unity efficiency.

With a sample scroll-type compressor that is electric motor driven, one can input, for instance, 4kW of electric energy and transfer 6~8kW+ of heat out of the vehicle cabin. (This doesn't break any thermodynamic laws, entropy is always increasing...)

I am ignorant of the efficiency of the Stirling engine as a heat transfer mechanism. Is it above unity?

Henry Gibson

The combination internal combustion engine and steam engine was called a Still engine and was used in stationary engines and ships. Modern large containerships sometimes use exhaust heat from piston engines to run steam-turbo-generators for electricity. The Kitson-Still, a diesel-steam, locomotive was tested in England for several years and saved much fuel per work done. England had no oil, but if Southern Pacific Railways in the US had made them at the same time they would still be used. The Kitson-Still died in the economic collapse of the 1930s. Steam started both the train and the diesel engine until the diesel put out enough power. A modern version would outperform all diesel electric locomotives in economy and operating costs. No clutch, gear shifting, or starting motors are needed...HG....

ai_vin

Ah yes, the Still engine -
http://www.dself.dsl.pipex.com/MUSEUM/POWER/still/still.htm

SJC

I do not think so, but I have not looked that closely. I just noticed that they said that stirling cryos could be used for cooling, but that is mainly for making gases into liquids. It could have just been Powerpoint hype. There is a lot of that out there. BLDC motors driving compressors is fine with me. Just get the stuff off the figgin' belt and save fuel.

SJC

Here is some info on Stirling heat pumps:

"Heat-pumps are by far the most energy-efficient types of heating systems. Stirling heat-pumps also often have a higher coefficient of performance than conventional heat-pumps."

http://en.wikipedia.org/wiki/Stirling_engine#Disadvantages_of_Stirling_engines

This does not address their COP as an AC, but thought I would post it anyway.

Harvey D

SJC:

About trying to reach perfection, isn't that what ICE people have been doing, for the last few years, to extend the useful life span of a dying technology or to delay the arrival of the replacement technology, i.e. electrified vehicles.

It is fair game to defend dying species. We still have a few horses, but they are no longer used to lug us around. ICE vehicles will soon be museum pieces. Fortunately, we can recycle most of the 800 to 1000 million units to be retired.

Let's face it, vehicle electrification is the way to go for increased efficency (up to 3x), reduced fossil or agro liquid fuel consumption, reduced noise, reduced maintenance, reduced complexity, less GHG and eventually, reduced cost.

I don't know what we will do with existing IC Engines and automatic transmission factories. Would they qualify to be recycled into highly automated battery and electric motor factories?

SJC

I look at one therm of natural gas. You can use it to make electricity at 30%-60% efficiency, depending on gas turbine to combined cycle plants, so let's as 40%.

Now you take the 40% and transmit it at 4-10% losses so let's say you are now at 35%. Now you put it through a charger and into batteries at another 10% loss, which brings you down to 32%. Now you put it through batteries that have 10% loss round trip, that puts you at 30%. Now you put it through a controller at another 10% loss and a motor at 10% loss, that puts you at 24% pipe to wheels.

Now take that same therm and put it in an NG hybrid. You can get about the same efficiency. I am not sure that electric cars are going to be all that much more efficient. You can put pollution controls on the central plant, but lots of lobbying can take care of that.

Brian P

The theoretical possibility exists that the grid electricity could come from renewable sources, or at least from non-fossil-fuel sources. *THAT* is what we need to be working on, before contemplating mass-market all-electric vehicles, or even plug-in hybrid vehicles!

I can only speak for my own province, but I do know that in summer, our electrical grid and generating stations are already stretched to the max and sometimes beyond, and that's *without* any significant number of all-electric vehicles on the road.

SJC

The basic belief is that the cars will be charged at night when demand is low. Somehow, some people have convinced themselves that this is the next best thing to free power. As if the turbines are spinning and not putting out anything anyway, so might as well use it. There are spinning reserves, but we need to get real. The power companies in California have said that they can handle millions of PHEVs during off peak hours. They would love the revenue, but so far have said nothing about any free power.

Andy Eppink

This is an example of a combined cycle which is commonly used in electric power generation with phenomenal efficiencies (e.g. GE's natural gas fired H series heavy frame steam injected gas turbine exhausting into a triple pressure regenerative feedwater heating steam cycle (with gas and steam turbine lube oil heat recovery into the condensate, I think) will deliver 60% busbar efficiency. Compare that to the typical 27-28% delivered by the typical automotive gas engine.
Steam alone won't do it Anne. Typical Rankine (steam) temperatures are far too low. The most efficient steam engines are powerplant supercritical cycles which still have a throttle inlet temperature of only about 1100 deg. F or so and thus can deliver only abt. 48%, even with all kinds of regenerative feedwater heating and heat recovery.

hassan saad

very interesting and encouraging

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BODHPS

To All,
I'm glad I finally found you. I have been working for years on this. And I have made great progress, but I need a sanity check. Please review my work and provide any honest feedback you feel valid.
Visit http://www.Youtube.com/user/jedareed and http://www.realworldio.com for a complete picture of my invention.

I believe this invention could be developed into products that could do exactly as this thread is discussing.

best regards,
BODHPS

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