1903 six HP steam engine powers modern off grid power system

[buenijo]

Osan, I am aware of that work. I suspect the media took it and hyped it up a bit. Perhaps there will be something practical to come out of the work, but I bet it'll be a while before we see anything. If a cost effective and highly energy dense battery were to be produced, and with the ability to be fast charging, then I suspect this would be a boon primarily for photovoltaics in the off grid setting and EV's... at least, these are what I would use it for. One reason I consider seriously the prospect for a micro scale combined heat and power steam system is the possibility for such a system to be configured to operate for long periods at low output, and this would eliminate the need for a high capacity battery system. Come up with an inexpensive super battery that lasts as long as the PV panels, and I would focus on PV as a primary source of electricity in the off grid setting. However, it's also true that a properly configured micro scale combined heat and power system can use a fuel in a very highly efficient manner - and that's also a very attractive prospect. Consider that as good as these batteries get with respect to energy density, they're never going to approach the energy density of a fuel source - including biomass.

Also, speaking of long term energy storage, I believe I posted on using desiccants for thermal storage. One example is zeolite which has the ability to store heat indirectly with an energy density four times better than water (at atmospheric pressure) by mass, and twice as good by volume. Solar heated air has been shown to regenerate such desiccants effectively. The desiccant generates heat as it adsorbs water vapor into its internal porous structure, and this heat can be used for heating applications. It can also dry air for use in evaporate cooling. If/when solar insolation may be insufficient, then a micro heat engine might be used to simultaneously recharge the graphene capacitor and while regenerating the zeolite desiccant.

[buenijo]

Check out this very sophisticated micro steam engine project. While not useful due to the very low power, it has a lot of interesting features and it appears to be a high quality piece of work. Clearly Dan is very talented.



The most interesting feature to me is the way he devised an exhaust valve in the piston to eliminate compression. I have seen engines described that do this, but this is the first time I've seen one incorporated with a bash valve intake valve. The bash valve seals steam from entering the piston until an extension on the piston taps it open on the up stroke to let in a charge of high pressure steam. These are generally used only with uniflow piston steam engines where the steam is exhausted from the cylinder when the piston uncovers one or more ports in the cylinder wall. This engine in the link includes a valve in the piston itself to relieve compression. Otherwise, the residual steam in the cylinder would be recompressed in the cylinder head. This recompression is favorable thermodynamically since it helps to reheat the cylinder before admitting a fresh charge of steam. However, if one desires to maintain a high condenser pressure, then I believe this approach is a very good idea. Otherwise, the higher exhaust steam pressure will not allow for high compression as the pressure will rise so high that sufficient steam cannot be admitted through the intake valve. On the exhaust valve used in this system, the steam pressure in the cylinder keeps the valve shut during the power stroke. When the exhaust port in the cylinder is uncovered, then there is no more differential pressure across the piston. This allows a small spring to open the valve to relieve the recompression. An extension on top of the valve serves to tap open the bash valve, but the exhaust valve gets reseated before the intake valve opens.

On the electronic control of the admission valve, it seems he is holding the inlet valve open by a magnetic field after the the piston unseats the valve. I've seen mechanical systems that do this by providing an adjustable stop on the ball that limits its travel. If the stop is backed off, then the ball can get tapped open a bit more and let in steam for a longer period. If the stop is close to the ball, then the ball reseats more quickly. This mechanical approach has limits that would be overcome by the electronic approach. I think the electronic approach here is interesting and has potential for systems for use in a highly variable output engine (like a constant speed generator or automotive application). Myself, I am interested only in a constant speed system that maintains a low output - I would use DC or a small battery and inverter system for AC power as this is just so much simpler.

ADDENDUM: I came upon this excellent description of this engine: http://www.kimmelsteam.com/gelbart-uniflow.html

[buenijo]

Home made small steam tractor, wood fired:

[buenijo]

Very nice hobby steam engine set up:



Scale this up about 10 fold and fuel with wood, then it might be useful rather than just pretty! Seriously though, I am impressed. It's a good piece of work. Also, this is large by model steam standards. The engine is rated for 1/4 hp.

The guy has an awesome web site!: http://rcdon.com/index.html

Steam project details: http://rcdon.com/html/6ci_steam_engine_project.html

NOTE: I contacted this individual for some clarification on his system. He is using Teflon compression packing to seal the piston. This along with graphite based packing products is what I'll be trying for my future project. He says it seals very well. He reports that he has only 25 hours on the engine so far, but it still runs as new. He speculates that he will get well over 1000 hours on the seals. Note that Teflon packing generally has a temperature rating of about 500F. The temperature of 100 psi saturated steam is about 330F. However, also note that the piston seal is in contact with the cylinder wall that will be maintained at a temperature roughly equal to the mean between steam generator temp and condenser temps. So, this suggests that Teflon can be used with steam at much higher temperatures. Also, I believe he is using Teflon also to seal the piston valves. This would put a hard limit on the steam temps as the valve sees peak steam temperature. However, poppet valves and bash valves require no such seals.

ADDENDUM: The owner reports that this engine requires oil lubrication. However, he notes that there is some metal to metal contact in the piston valve. Also, without oil, the cylinder that is not a smooth bore would damage a soft packing material. He didn't specify on this particular cylinder. If one desired to experiment with sealing a steam cylinder without using oil lubrication, then it seems reasonable to start with a smooth bore cylinder (like a hydraulic cylinder). Finally, oil is also useful for protecting metal from corrosion, so if one desired to experiment with doing away with oil lubrication, then it would be necessary to keep a super tight system free of air (fully condensing with good seals).

[buenijo]

http://cozincmtusa.com/home

Interesting site maintained by a small group dedicated to developing a modern highly efficient steam automobile engine. They're focused on a compounded piston engine with reheat and heat regeneration. Solid information. NOTE: I may have listed this previously.

[buenijo]

Articles discussing the 1970's experimental SES automotive steam system:

http://modernsteampower.wordpress.co...-dodge-monaco/
http://www.steamcar.net/jakuba-1.html
http://kimmelsteam.com/dodge-monaco.html
http://kimmelsteam.com/ses.html

NOTE: I posted this for interest only. The system developed was doomed to fail mainly because it had no hope of achieving sufficiently high fuel economy or sufficiently high power/weight.

[buenijo]

Possibly the single best web site for steam engine education: http://www.kimmelsteam.com/

[buenijo]

A few interesting videos I came upon:

http://www.youtube.com/watch?v=GPUlnqlWt7U

http://www.youtube.com/watch?v=H4i2nYZUBzo

http://www.youtube.com/watch?v=VbMBZNsiGcA

http://www.youtube.com/watch?v=XsOWB_fzrdY

[buenijo]

www.slamvalvemotor.com

This design allows for converting an air compressor or small piston engine to a steam expander. The only problem I have is the efficiency claims made on the web site. It is claimed that this engine will achieve more than 20% thermal efficiency with saturated steam at 405F and exhausting to a condenser at 160F. Well, basically, this is nonsense. In fact, the figure is greater than Rankine cycle efficiency. Other than this BS claim, the system is very clever. The ability to retrofit existing cast iron air compressor units that are low cost is a very good idea. Furthermore, the retrofit requires nothing beyond installing a new compressor head and plumbing the steam supply and exhaust lines to the head. A cylinder head is provided containing an intake valve and an exhaust valve. This head can be bolted onto existing air compressor units. The valves are made of curved pieces of flat spring steel that seal ports. The intake valve spring tension acts to unseat the valve, but it's kept shut with boiler pressure. The exhaust valve spring tension also acts to unseat the valve, but it's kept shut with cylinder pressure.

The intake valve is popped open by a small extension on the piston, and this lets in a charge of steam. The exhaust valve shuts as cylinder pressure builds. The piston moves down. Now, cylinder volume increases at an accelerating rate from 0 to 90 degrees past top dead center, and at a certain point corresponding to about 30-45 degrees past top dead center (according to the site) the boiler pressure will force the intake valve shut. There is a control rod on top of the intake valve to control how far it will open, and just barely letting the valve open will make it shut sooner since cylinder pressure will decrease sooner as the piston moves past TDC under this condition (since the admission of steam to the cylinder is restricted by this process). Once the valve shuts then the steam expands to force the piston thereby providing a power stroke.

Near the end of stroke a port in the cylinder relieves cylinder pressure. Without cylinder pressure to seat the exhaust valve, then it springs open and stays open to relieve pressure during the exhaust stroke. It's possible to set the spring tension so that a port is not required since the cylinder pressure will fall as the steam expands. This approach has been called a "decompression" valve in other designs. In my opinion, a superior design would have an extension on the piston (perhaps even a small spring) seat the exhaust valve just before the inlet valve is opened.

http://www.youtube.com/watch?v=yaMryydpIhs

[buenijo]

www.biosteamengine.com

I don't know anything about their operation. It is clear that the design of the engines is primitive. However, the machine work looks good, and the design is simple, which I like. If anyone finds information on the product, then please post it here.

ADDENDUM: Site appears to be dead.

[buenijo]

http://kimmelsteam.com/docs/Vision%20essay.pdf

[buenijo]

Info on the Pritchard steam engines:

http://kimmelsteam.com/pritchard.html

Details on the steam car conversion (Ford Falcon): While not particularly fuel efficient at just under 20 mpg U.S. (on kerosene), the city mileage was likely on par with some modern conventional gas cars in some settings (NOTE: a later version showed 22.5 mpg U.S. at 50 mph). The basic design of the system is simple and would likely achieve long operating life. There was no transmission and no clutch. Emissions achieved was comparable to modern vehicles, yet with no pollution control hardware such as catalytic converters and computer controlled ignition systems. The wide fuel capacity of such a vehicle cannot be matched by internal combustion systems - and emissions were low on start up which is not the case with internal combustion cars before the catalytic converter warms up. While not listed in the following links, I understand the steam temperature was limited to 750F to support conventional oil lubrication. Pressure was 1200-1400 psi. Cutoff was 14%, which corresponds to a very low expansion ratio. In short, this engine system was not designed primarily for high efficiency. Overall net thermal efficiency was probably on the order of 15%. Note the use of a steam exhaust motor to drive the condenser fan and water feed pump (an elegant idea).

http://kimmelsteam.com/images/Pritch...s%20letter.jpg

http://kimmelsteam.com/images/Pritch...tisment106.jpg

http://www.linux-host.org/energy/spritch.htm

Description of the stationary unit currently in development:

http://uniflowpower.com/technology/u...generator.aspx

Interesting forum thread started by Ted Pritchard shortly before his death:

http://steamautomobile.com/ForuM/read.php?1,1528,page=1

[buenijo]

Popular Science article on the Carter steam car:

http://books.google.com/books?id=Rke...0WORKS&f=false

SACA article on the system (written by Jay Carter):

http://www.steamautomobile.com/archi...v17n3.CV01.pdf (295 lbs for the complete 90 hp automotive system! - not including required transmission, a conventional automotive unit).

NOTE: The Carter system deviates from previous steam engine design in many ways. One way that is particularly interesting is the control of the steam generator. The steam generator is particularly small with the complete unit (tubing, casing, insulation, fuel delivery, blower fan, and controls) all well under 100 lbs - and compact. The car is not accelerated by forcing a steam throttle valve or controlling a cam system to vary steam cutoff. Rather, when the accelerator pedal is depressed, then the air/fuel is admitted to the burner at a higher rate. This increases steam pressure, and the response is acceptable because there is a relatively low mass of steam generator tubing, a low mass of water/steam contained within the tubes, and a high surface area/volume in the tubing. Adding heat increases the pressure and this increases engine torque. Steam temperature is moderated by controlling the water pumping rate. This is similar in many respects to previous systems, but the absence of a throttle valve makes it quite different. Carter's engine uses bump valves and a manual transmission with clutch. So, the engine idles when at a stop. In many ways the Carter configuration is simpler than all others - and it achieved the best results to date (mid 1970's), and possibly ever.

http://ntrs.nasa.gov/archive/nasa/ca...9810021983.pdf (starting on page 11 is a description of Jay Carter's third generation steam engine used in an experimental solar thermal power generation set up). This discussion sheds some light on how the pistons were lubricated in this system with the comment "Toward the end of each stroke oil is injected directly onto the piston rings to minimize wear and leakage around the rings." Jay Carter notes in a discussion elsewhere that oil is pumped at a high rate to lubricate the engine - on the order of one quart of oil every ten minutes as I recall. Of course, oil must be wholly free of detergents to prevent emulsification with water. Also, I understand a synthetic oil was used for the system. (see these as well: http://ntrs.nasa.gov/archive/nasa/ca...9800011332.pdf, http://pdf.usaid.gov/pdf_docs/PNAAX001.pdf).

The Carter engine is relatively simple and compact (especially compared to high efficiency Stirling engines and sophisticated micro turbines). Yet, in actual tests it was able to generate electricity delivered to the grid at an efficiency of 20% (everything accounted for except the efficiency of the concentrator - that is, 20% of the the heat delivered to the working fluid water/steam was converted to grid quality electricity, and the electricity required to run the auxiliary systems were deducted from the output to provide a net figure) - and the exhaust steam was atmospheric (212F).

http://latimesblogs.latimes.com/.a/6...b186970b-500wi

This is a good basic description of how a centrifugal oil/water separator works.

[buenijo]

The graph shows the efficiency of typical automotive gas and diesel engines as they vary over their power range, and at 50% max rpm which is typical of actual driving conditions. Note that the "Bourque engine" is a sophisticated modern piston steam engine design proposed by mechanical engineer Dr. Robert Bourque (http://www.newsteamengine.com/). The purpose of presenting this is not to introduce his engine, but to illustrate how the efficiency of conventional automotive engines vary significantly over their power range (especially gas engines). Diesel is roughly 7.08 lbm/gal (U.S.) with about 128,500 btu/gal, and gasoline is roughly 6.15 lbm/gal (U.S.) with about 116,000 btu/gal. There are about 2.2 pounds in a Kg.

The efficiency of the 1.6 liter gas engine over the Normal Operating Range shown varies from 15.2% to 25.5% with a mean value in the low 20's%. The peak efficiency of this engine shown by the graph corresponds to 29.5%. Note that the efficiency drops dramatically at outputs below the Normal Operating Range.

The net thermal efficiency of historical steam cars were as follows: Stanley Steamer (6-8%), White (10-12%), Doble (10-12%), Pritchard (12-15%) - (although, note that the White and Doble systems were capable of 14% overall efficiency at peak output - *). The Stanley saw about 8-10 mpg on kerosene (*). The Doble saw about 10-14 mpg on kerosene and was a very heavy automobile at 6000 pounds (one first hand account claims 13 mpg on highway on gasoline fuel for a restored Doble E series in good running condition). The peak steam temperature to the expander in all cases here were under 800F. Furthermore, these engine systems saw high thermal losses due to poor insulation, poor heat exchange, and distributing steam a distance from a steam generator to the expander (except the Pritchard unit that put the expander right next to the steam generator and did a good job of insulation). Kerosene shows about 124,000 btu per U.S. gallon (lower heating value). My research shows that the Pritchard steam car (converted '63 Ford Falcon) achieved 22.5 mpg on kerosene at 50 mph. According to the graph, 50 mph corresponds to roughly 20.8% efficiency for the gas engine. This is about 40% higher than the efficiency of the Pritchard engine. Therefore, if the '63 Falcon were powered by a typical gas engine of today, then it would consume about 71% of the fuel energy of the Pritchard car at 50 mph. This corresponds to about 29.5 mpg on gasoline. Note that the Ford Falcon was known to achieve fuel economy in the low 30's (mpg) during actual road tests designed to demonstrate optimal fuel economy (it was a competition with other car models during the 1960's, and the Ford Falcon won with its stock engine). In other words, my analysis here took figures from disparate sources and shows that they agree fairly well. NOTE: Yeah, the stock Falcon did better than 29.5, but it was quite a compact car for its time, and it weighed 2300 lbs vs. the 3200 lb modern car considered in the graph.

Now, consider an engine (any engine) that can power an automobile and show optimal thermal efficiency in the Normal Operating Range. If an automotive engine can be had to show similar dynamics of peak efficiency in the Normal Operating Range and with little variation in efficiency over a very wide output, yet achieve efficiency in the mid-20's or higher, then it would show superior fuel economy to existing conventional gas cars. An even match requires the efficiency to increase over the Pritchard engine by about 40%. That is, the efficiency has to get the low 20's%. Now, the Doble steam car is known to achieve fuel economy during city driving roughly the same as modern gas SUV's of similar weight (6000 pounds). This was due to the fact that the Doble does not use steam when stopped or while coasting (along with large automotive gas engines showing poor efficiency under lights loads and low engine speeds). This same dynamic would also be favorable for a modernized steam car. That is, fuel economy during city driving could be much higher in a highly efficient modern steam car as compared to conventional gasoline fueled automobiles, and this would take the combined cycle fuel economy higher.



I lifted the following image from the following link: http://www.autospeed.com/cms/article.html?&A=112611 . There is an excellent discussion there of how the efficiency of a conventional gas engine varies over its operating range. A conventional gas engine can show very impressive efficiency. Unfortunately, it has to operate under a limited set of conditions to show this high efficiency. Note the sharp decrease in specific fuel consumption at near 3000 rpm and 25% throttle. This speed is where most passenger cars are geared for highway travel, and 25% load is roughly the output required to maintain highway speeds on level ground. However, the efficiency here is nowhere near peak. This dynamic is the primary reason that hybrid cars show higher fuel economy. A little thought leads to the conclusion that such an engine with a highly variable efficiency profile will never show an average efficiency approaching the peak efficiency value in a real world application where output must be highly variable. This is an important reason why a modern steam engine with a flat efficiency profile is well suited for such applications. Incidentally, it is a major reason why diesel engines see superior fuel economy since the efficiency of a diesel engine is not only high, but it also doesn't vary nearly so much as a conventional gas engine. Also note again that this graph considers traditional (i.e. conventional) gas engines. Modern automotive gas engine systems have been able to improve the efficiency profile significantly with variable cam profiles (like VTEC). One of the most promising systems soon to be used in commercial vehicles is the precise operation of valves using electronically controlled pneumatic actuators. The have been shown to be reliable and to improve fuel economy on the order of 15-20%. The fuel economy of modern and sophisticated automotive gas engine systems are improving significantly. In my opinion, a modern steam car would not be superior with respect to fuel economy to any automobile that uses a fully equipped modern internal combustion engine system that pulls out all the stops. However, I do believe it can be competitive in this respect while being simpler, showing superior performance with high torque and ideal torque profile for the application, and using a much wider range of fuel sources that the IC engine cannot use and with a great deal fewer processing requirements. There will be a time when petroleum reserves are depleted to the point that alternative fuels become economically viable. If the cost of these fuels can be lessened significantly by eliminating the final processing steps (and costs involved in transporting the fuel - in other words, encouraging production of fuels on a regional and local basis) required to make them suitable for modern IC engines, then this will favor a modern steam engine. I believe this dynamic would be necessary to bring a modern steam car into wide use.



See this discussion: http://www.heat2power.net/en__wasteheat_in_ices.php

(*) Both the White and Doble steam power plants have been tested at 14%+ overall thermal efficiency - in particular, a 40 hp White system was tested around 1906 under controlled conditions on a dynamometer at a sustained output of 41 hp and showed just over 14% overall efficiency. The overall efficiency of the Stanley was more typically 6% - a large loss in that system was the boiler, and this was shown by replacing the boiler with a steam generator in one car that improved the fuel range considerably.

NOTE: Here is another account that illustrates well the low efficiency of automotive gas engines under certain conditions. A controlled test was performed at Auburn University to test a truck fueled by a wood gasifier. The truck was a fairly late model vehicle in good running condition, and was capable of normal operation on gasoline. The truck was driven on gasoline at a speed of 50-55 mph on level ground and its fuel consumption was measured (it showed 21 mpg during the test). The truck was then driven under the same conditions, but fueled by the wood gasifier. The energy density of the wood gas was measured, and the fuel energy required to power the vehicle was determined. It turned out that fueling the truck on gasoline required 37% more energy to travel the same distance as compared to wood gas. Note that the energy in the wood gas itself was measured, and not the energy in the wood. There are thermal losses in the gasifier that amount to roughly 25%. However, it turns out these losses are less than the gains on wood gas. So, under the test conditions at least, the truck was significantly more efficient when fueled by wood vs. gasoline. The results are very telling indeed because I know that a gas engine of that design when fueled by wood (wood, not wood gas) shows a net thermal efficiency of about 17-18%. This implies the efficiency of the truck engine fueled by gasoline under these conditions is somewhat less than 17% (just about where the lower end of the "normal operating range" indicates on the graph above - the graph shows 10% of engine rated power at that point - this would be about 20hp for a 200 hp rated engine, and this is roughly correct here: a truck like this has an engine rated at around 200 hp, but requires only about 20 hp to maintain 50-55 mph on level ground). I consider this fascinating because I have had conversations with engineers who not only claim that an automotive gas engine is a lot more efficient under those conditions, and who would predict an efficiency on wood gas roughly half of the measured value, but even denied outright the test results. SUMMARY: The truck, and by implication many conventional gasoline fueled vehicles on the road today, show surprisingly low efficiency during real world driving. The only time the efficiency gets impressive for most vehicles is during highway driving when the engine is operating at a fairly high output relative to its rated power. Even in these cases the average thermal efficiency of the engine is in the low to mid 20's% (diesel engines are much better under just about all conditions by the way).

[osan]

Not exactly steam...

[buenijo]

Hi Osan. That's a very elegant design. Funny, I was reading a description recently about a compounded gasoline internal combustion engine that was manufactured for a short time during the early 20th century. I like how this design shares a low pressure cylinder with two primary cylinders.

From what I've seen, I expect the peak overall efficiency of automotive internal combustion engines to see the high 30s% in the next 10 years. There are Diesel engines, direct injection gasoline engines, the Scuderi system, and this configuration will also do it. There remains the problem of the relatively low efficiency at low part loads and idling losses, but Diesel and DI lessen this. There is also hybrid systems - but then there is the complexity issue. Actually, if MPG is what's wanted, then the low hanging fruit can be had with smaller cars and aerodynamic designs (like the Elio). I hope the Elio makes it to market. I would buy one.

Personally, I don't see a practical way for steam power to ever make a serious comeback in the automotive arena - at least not any time soon. However, I think there is a place for small stationary cogen systems fueled by biomass or waste products, and compact solar thermal engines.

[osan]

Very nice hobby steam engine set up: http://www.youtube.com/watch?v=8FXeYKvQQ6o

Scale this up about 10 fold and fuel with wood, then it might be useful rather than just pretty! Seriously though, I am impressed. It's a good piece of work. Also, this is large by model steam standards. The engine is rated for 1/4 hp.

The guy has an awesome web site!: http://rcdon.com/index.html

Steam project details: http://rcdon.com/html/6ci_steam_engine_project.html

NOTE: I contacted this individual for some clarification on his system. He is using Teflon compression packing to seal the piston. This along with graphite based packing products is what I'll be trying for my future project. He says it seals very well. He reports that he has only 25 hours on the engine so far, but it still runs as new. He speculates that he will get well over 1000 hours on the seals. Note that Teflon packing generally has a temperature rating of about 500F. The temperature of 100 psi saturated steam is about 330F. However, also note that the piston seal is in contact with the cylinder wall that will be maintained at a temperature roughly equal to the mean between steam generator temp and condenser temps. So, this suggests that Teflon can be used with steam at much higher temperatures. Also, I believe he is using Teflon also to seal the piston valves. This would put a hard limit on the steam temps as the valve sees peak steam temperature. However, poppet valves and bash valves require no such seals.

ADDENDUM: The owner reports that this engine requires oil lubrication. However, he notes that there is some metal to metal contact in the piston valve. Also, without oil, the cylinder that is not a smooth bore would damage a soft packing material. He didn't specify on this particular cylinder. If one desired to experiment with sealing a steam cylinder without using oil lubrication, then it seems reasonable to start with a smooth bore cylinder (like a hydraulic cylinder). Finally, oil is also useful for protecting metal from corrosion, so if one desired to experiment with doing away with oil lubrication, then it would be necessary to keep a super tight system free of air (fully condensing with good seals).

Beware that teflon cold flows. It is not good as a seal or bearing for some applications.

[Dr.3D]

Beware that teflon cold flows. It is not good as a seal or bearing for some applications.

I remember a fellow who used it to seal the screw drive shaft on his boat. It worked for awhile and then ate into the shaft to the point where the shaft broke off.

[buenijo]

I came across the following description of a small scale steam engine used to power a small boat: www.steamboat.com.au/SL%20ALBA.doc . Of particular interest is the use of a surprisingly small and simple monotube steam generator. The control system for the steam generator is also interesting, and virtually identical in principle to some of the configurations I have considered. I'll provide a summary of the system here.

The engine/expander is a simple single cylinder, double acting, slide valve unit with 1.5" bore and 2" stroke. The steam chest pressure is described at 150-200 psi with engine speeds of 350-400 rpm. This corresponds to a conservative 1/2-2/3 hp at the shaft. The system was clearly not built with efficiency in mind. I expect the overall efficiency of the steam generator alone to be on the order of 50%. Net thermal efficiency is probably 3% at best. The builder noted elsewhere that he gave no priority to efficiency or cosmetics. Note the steam generator. It is made of a length of stainless steel tubing 5-6" mm (1/4") diameter and 40 feet in length. This generates superheated steam at 550-600F. It is a single continuous length of tubing with one end connected to the water feed pump discharge, and the other end is connected directly to the engine steam chest. The water feed pump is driven by a small 12 volt electric motor, and this was selected to provide some control. The motor uses a pulse width modulated (PWM) controller with the potentiometer actuated using a bimetallic strip taken from a small electric frying pan. The strip forces the controller potentiometer as the steam temperature approaches 600F, and this increases motor speed to max. Pumping water into the coil at the max rate serves to cool the coil. It would likely increase engine power as well in this particular set up that uses a more or less uncontrolled wood fire. Engine output is controlled by lowering steam chest pressure by venting steam using an manually adjustable steam relief valve. Again, this is not an efficient system (lots of heat wasted!). However, this is really necessary to do a monotube steam generator relatively simply under these conditions.

Now, if the system were designed for a constant output, then things could be a lot simpler and more efficient. A small gasification wood furnace can be tightly controlled with respect to output by using a blower fan to control the rate of air supplied. One thing this project shows well is how small a steam generator can be for a useful steam engine. In fact, this 40 foot length of 1/4" steel tubing is large enough to support well over one hp with a more efficient expander, and thermal losses from the steam generator could be low as well with a better coil shape and good insulation. Steam temperature could be controlled by using a bimetallic strip to control the output of a small blower fan, and this would allow for controlling engine output without compromising engine efficiency (i.e. venting steam). It it also possible to use an RTD temperature probe or thermocouple with arduino to control the fan. I suggest placing a water relief valve at the feed pump discharge set high enough to ensure the steam pressure to the engine is just high enough to support the highest desired pressure. The steam pressure to the engine steam chest could then be controlled using a simple steam throttle. Alternatively, the pressure (and resulting engine power) might be adjusted with an adjustable water relief on the feed pump discharge. This would be acceptable if the system is designed to operate for long periods at a constant rate (which I consider ideal for a micro scale CHP system fueled by biomass).

I disagree on his insisting that the steam generator tubing must be welded or flared fittings. I think a good compression fitting will work fine. I am aware of Swagelok fittings being using with very high pressure superheated steam.

[buenijo]

https://www.youtube.com/watch?v=QJAY6mkxTIg
https://www.youtube.com/watch?v=h_wKu8klZDA

Very clever steamboat. A condenser would make for a dead quiet ride with such a low speed steam engine.

[buenijo]

Jay Leno's new Doble steam car (formerly owned by Howard Hughes):

http://www.youtube.com/watch?v=rUg_ukBwsyo

[Natural Citizen]

I am wondering why we're not hearing more about this and someone, somewhere, in the process of designing practical graphene batteries for manufacture.

Here is an interesting application...

Fuel from thin air? Graphene breakthrough may lead to green car revolution...

Scientists believe they can use the same material found in pencil lead to revolutionize the green car industry. They discovered that graphene may serve as a fuel cell membrane and even allow the harvesting of hydrogen from air.

“We are very excited about this result because it opens a whole new area of promising applications for graphene in clean energy harvesting and hydrogen-based technologies,” said Marcelo Lozada-Hidalgo, co-researcher on the study.

One-atom-thick graphene is the world’s thinnest, but also strongest, material – 200 times tougher than steel. It is also the world’s best conductor of electricity. Knowing that graphene is impermeable to even the smallest of atoms, hydrogen, Geim's team decided to test whether protons, or hydrogen atoms stripped of their electrons, were also repelled.

“There have been three or four scientific papers before about the theoretical predictions for how easy or how hard it would be for a proton to go through graphene and these calculations give numbers that take billions and billions of years for a proton to go through this same membrane,” Professor Geim said, who won the Nobel Prize for Physics in 2010 for discovering graphene along with his colleague Konstantin Novoselov in 2004.

The team found that if the temperature was raised and if the graphene films were covered with a catalyst such as platinum, then the protons would have little problem in passing through.“It’s just so dense an electronic field it just doesn’t let anything through. But it’s a question of numbers, no more than that. This makes a difference between billions of years and a reasonable time for permeation. There is no magic,” he added.

Fuel from thin air? Graphene breakthrough may lead to green car revolution

[Anti Federalist]

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[buenijo]

Just dropping in to link an interesting paper. Note that I don't do research into this topic any longer despite my continued interest. Basically, I've done more than enough research to have a chance at building something useful. Unfortunately, the problem is I do not currently have the resources to make a decent go at it. I simply cannot justify it financially. Maybe some day. Until then I'll share what I may come across and answer questions if anyone cares to inquire.

http://steamautomobile.com/ForuM/fil...N4200_2010.pdf

Fairly recent engineering thesis covering the steam engine designed and operated at the White Cliffs solar thermal plant in eastern Australia. For those who desire to see the original report on this system, see the following link: http://www.rossen.ch/solar/sustain_r...ect_report.pdf

The thesis spends a lot of time on the steam inlet valve design. Unfortunately, there was a lot of data not recovered from the original work done during the early 1980's. Apparently, despite the work having been done by a university, there was a corporate entity created to oversee the project and much data was subsequently deemed proprietary (and finally lost it seems - I'm guessing someone figured they couldn't make any money off of it, and then just sat on it - what an ass). It's clear from the discussion here (and elsewhere) that the lift pins on the bash valve design see the most abuse and subsequent wear. It seems to be the main problem with the concept. However, according to the initial report the valve lasted well beyond 1000 hours of actual operation - and at an engine speed of 1500 rpm (see page 132 of report). Note that, in my opinion, the bash valve concept is not the best for larger engines as casually mentioned in the report. The recent work of Terrajoule shows that superior results are had from a more traditional steam engine design. However, I remain convinced that this is the best approach to be pursued for those who desire to devise a simple (but useful - as opposed to the toys seen on YouTube and elsewhere) micro scale CHP steam engine system fueled by biomass. The thesis emphasized something that I've held since I considered the problem of a simple micro scale steam engine system. If a bash valve is used, then emphasis should be placed on selecting a durable lift pin that is also both inexpensive and easily replaced. Basically, it should be sacrificial item. Most descriptions I've seen on bash valves report few problems with the actual valve element and seat. The one point of emphasis is to ensure the valve element (often a ball bearing) is harder than the seat otherwise the ball will be worn by the seat and sealing will be compromised. I still like the use of a ball for its simplicity even though other bash valve designs are objectively superior. A hard ceramic ball bearing is the best candidate I've considered (readily available from McMaster). Personally, I tend to believe a small engine operated at relatively low speeds will do well with this basic design.

NOTE: In sections 2.6 and 2.6.1 (and 3.4) of the thesis paper there are interesting observations that suggest a rather ridiculous possibility. (1) It seems the engine had been operated rarely over the previous many years. Yet, there was significant deformation of the lift pins observed. (2) There was difficulty finding specs on the original length of the lift pins. Yet, a set of pins were discovered. Upon measuring, it was found these pins were too long. So long in fact that they prevented the engine from turning over as they forced the balls up against the top of the valve guide plate. (3) Upon measurement of the installed lift pins (that were significantly deformed at their ends) it was found they they would cause similar intereference as described in (2) if they were any longer. This suggests that at one point pins of excessive length may have been installed in the engine and forcefully turned over (likely by starter motor) which crushed their ends. If so, then the existing deformation pattern was not caused by normal operation. It seems an interesting possibility that was considered on page 35 with the parting comment "However, if this scenario was the case then there is the chance that the material used to construct the pins is appropriate and can with stand the stresses; in which case this investigation may all have been in vain and someone has a lot of explaining to do." Hilarious! Well, at least get got his degree.

http://www.steamautomobile.com/archivepdf/SAv27n2.pdf (see page 32) One of original advisors on the White Cliffs steam engine design chimes in on the documented reliability of the engine system. At the time his writing this comment (1986) the engine valve system had documented 3000 hours of operation at 1500 rpm. I'd say this proved the concept as viable. The writer also notes that a lower speed engine will last much longer, all else equal, due to the lower forces on the valve system. In other words, I think there is good evidence to show that the basic bump valve approach is not flawed, and can therefore be used to devise a reliable engine system that also shows high efficiency. Since the basic approach is the simplest possible way to design a steam expander, then it seems the obvious choice to simplify the overall project.

[buenijo]

http://www.kimmelsteam.com/docs/Econ...n-Woodruff.pdf

An excellent discussion on the efficiency of steam engines - one I should have posted earlier. Good read for anyone genuinely interested in the topic.

[buenijo]

Great resource on steam engine system education:

https://steamautomobile.com/wsa/tutorial/index_2.htm

[buenijo]

https://www.youtube.com/watch?v=-85qglTdsE4

This is one of the better micro steam engine projects I've seen on YouTube (most of them are worse than useless). While this engine is little more than a toy since it's not configured to do anything useful, it does show promise as it's based on proven principles. Note a separate steam cylinder is mounted on the lower stock gas engine piston via a straight piston rod sealed at the base of the steam cylinder (been done many times before). The gas engine piston is used as a crosshead here. I expect the compression rings on the lower piston were removed to lessen friction. In my opinion, this approach is the best for many reasons and is how I would personally pursue a serious project. Unfortunately, there is no load on the engine, but it seems responsive for such a small cylinder and modest steam pressure (200 psi - while this may seem high, this engine a lot of compression that reduces steam admission). This is a "bump" valve uniflow using a check valve taken out of a cat water pump to admit steam. While this particular approach to fashioning a steam valve is clever, it would not likely stand up to abuse - but it's a good video to provide a glimpse into the approach. Note the absence of any steam chest. Rather, steam goes straight to the valve through a 1/4" line via a small ball valve. Other bump valve conversions I have seen take a 1/4" line directly to a fitting that contains the bump valve with practically no steam volume maintained above the inlet valve. With sufficiently high pressure steam this can be done (of course, a steam chest would be beneficial for higher engine speeds if desired). This basic configuration can show high efficiency and high power with the right design. Right at 15% overall efficiency is not unreasonable with sufficiently high steam pressure and temperature, and sufficiently high expansion and condenser vacuum on exhaust (actually, 20% could be achieved, but that would push the limits). That's another point - this engine exhausts to atmosphere, but it would be a lot more powerful with a vacuum condenser. With much higher steam pressures it would be a beast. Note that the peak cylinder pressure in a small gas engine is well over 500 psi. So, a smaller steam cylinder could use steam at even higher pressures without unduly stressing the crank in such a system. Impressive power is possible if one desires it. Of course, a furnace and steam generator is required - along with condenser and feed pump.

https://www.youtube.com/watch?v=cU4gM0jUDbk This is why you use a separate steam cylinder. Steam gets into the crankcase and mixes with the oil. Best not to deal with it. However, oil free of detergents (to prevent emulsification) can and has been used where the oil/water in the crankcase and the water/oil in the condensate move to a centrifugal separator. In that case the two are separated and the oil and water are reused. Sort of a pain for a micro system, and the reason I think experimenting with oil free systems is the best way to go. However, the process is proven to work well with steam temperatures up to 1050F in a single acting uniflow engine. The main difference there compared to traditional steam engines is the oil was not injected into the steam line. This was done in older steam engine designs to lubricate the inlet valve (generally slide or piston valves). Poppet valves and bash/bump valves do not require lubrication. Therefore, oil can be injected into the cylinder where average temperatures are much lower than peak temperatures. For example, in the Carter engine that used steam up to 1050F, the oil was injected directly onto the piston rings when the piston reached the end of stroke, and the rings were accessed from the uniflow exhaust ports in the cylinder wall. The rings were "bathed in oil" by the Carters' description using about one quart of oil every ten minutes of operation. All oil was recovered in the separator and reused. Oil lubrication has been shown to work in this kind of system where the average cylinder temperature is less than 650F. The Carter system had an average temperature of about 625F (the mean between the peak steam temperature of 1050F and the condenser temperature which was about 200F).

[buenijo]

Recreation of 1920's steam powered machine shop (actually in operation and generating revenue). Series of 10 videos on channel so far. Excellent information:

https://www.youtube.com/channel/UCBd...nGoJUag/videos

[buenijo]

I mentioned the start up company Terrajoule in post #175. I came across some recent information on their work. See the following video: https://www.youtube.com/watch?v=bHlAohwtLcs . The audio quality of the video leaves a lot to be desired, but the discussion is very interesting. As a recap, know that Terrajoule is using reciprocating piston steam engines in a solar thermal stationary power generation system with very inexpensive energy storage that permits 24/7 operation up to full rated power. The prototype plant they have in operation is using an insulated steel pressure vessel (a large propane storage tank) filled with water as their energy storage vessel. However, the next system is to make use of steel piping with SOIL taken from the site used as the primary thermal mass. The purpose is two fold: (1) to achieve somewhat higher temperatures in their storage (since piping has higher pressure ratings than a large tank), and (2) to store additional energy using soil (an even more cost effective means for energy storage). As before, the piping will be filled with saturated water under pressure. BTW, the use of piping permits somewhat higher pressures and temperatures, and also increases the surface area/volume ratio to allow for effective heat exchange with the surrounding soil (note that the thermal mass is contained ABOVE GROUND - it is NOT buried - rather, soil is taken from the site as a very cost effective thermal mass and used to store most of the heat). The general trend of the discussion is that the physics and economics of solar thermal power generation with thermal storage makes it cost effective at relatively small scale. It turns out there are many dis-economies of scale for these systems. This conclusion implies a return to steam engine technology that is far more efficient at the smaller scales. Also, the argument is for decentralized solar thermal since steam engines are excellent for meeting highly variable power demands and without suffering a loss in efficiency, and there are also opportunities for cogeneration in these settings. In short, solar thermal + steam engine at small to medium scale solves the problems better than alternatives. Note the smallest size of Terrajoule's modular system is 50 KW peak output with 20 KW average (continuous) output. 3S Power is currently looking to power rural towns and farms in regions that see a combination of high solar insolation and high electricity prices with the two best candidate regions being Australia and Chile.

* There is a particularly interesting discussion of the efficiency of steam engines vs. steam turbines as a function of scale, or power output starting at 10:40.

Also mentioned during the video is a start up company based in Seattle that is working on converting existing diesel engines to steam engines. The company web site is here: www.practicalsteam.com. Unfortunately for applications considered in this thread, they are targeting medium scale systems with power levels similar to those targeted by Terrajoule (i.e. no micro scale systems suitable for a household). Still, I like the trend - it seems the benefits of steam engine systems are starting to become recognized.

[buenijo]

www.lightsail.com

Interesting start up company. They are looking to store energy using compressed air. They have a system that increases significantly the efficiency in compressing air - and subsequently expanding the air to retrieve the energy. Interestingly, this idea is NOT new. In fact, I considered it independently as a means to capture heat of compression that is normally lost. It's very simple. When air is compressed, then the mechanical energy used to compress the air is transferred to the air molecules. This results in a rise in temperature. Well, the increase in temperature also increases the pressure (all else equal). So, one ends up having to use more work to compress the air when this heat of compression is not efficiently removed. The solution here is to use a fine water spray to moderate this rise in temperature. The water is heated in the process, and the hot water is separated and stored. When the air is expanded, then the hot water is again sprayed into the air stream. Well, expanding the air cools it, and the water spray heats it up. So, it works to increase the volume of air by increasing it's temperature - meaning, more work can be derived from the expanding air through this process. Basically, it significantly increases the efficiency of the process. Overall efficiency demonstrated is about 70% of the electricity used to power the motors that drive the compressors is recovered from the generators driven by the expanders. Much of the loss is in the motor and generator, so it can't get much better. Alternatively, the system could use the heat of compression for useful applications (like water heating in buildings or space heating), and when the heat is used in such applications, then the expanding air might be used in other ways such as air conditioning - configurations I have discussed elsewhere. The system as I understand it uses piston compressors that operate also as expanders. In many ways, the system is similar to the Terrajoule system. However, compressed air requires much higher pressures to achieve useful energy storage capacity. They are talking about carbon fiber tanks for very high pressure. Well, that's a problem for me. Personally, I am more impressed with the Terrajoule system. Still, this is interesting. What I like about Terrajoule is the elegant simplicity. By contrast, this system seems more complicated and costly.