Steam engine V Steam Turbine

[large_ghostman]

Tiny bit of background info, sooner or later most large energy production methods, literally boil down to steam (pun intended). As part of something else we are looking for a steam engine to borrow, a small model one.

While chatting about this the conversation drifted onto what would be better in a Bio Methane system for producing both power and heat. First reactions were we all voted modern turbine system (no real surprise), so for a bit of fun we looked at the plans for the new system.

The intention was simply to estimate how much better modern system would work over old steam engine types. To save alot of effort i will skip to near the end bit. Having looked at all the various processes involved with the new digestors, it may actually be more efficient to use a fixed bed steam engine (methane fired). And a methane/lpg type generator for when the steam engine heat side was needed.

The reasons are many, some are to do with pre processing abd some with post processes. Its mainly the mechanical side and the adaptations you could add, these are known to up efficiency in digestor system but are normally done different ways. On the lab scale its hard to prove this conclusively, mainly because even a model steam engine needs alot of energy to bring upto temperature.

But there is no reason you couldnt pre heat some of the water in the engine and take that into consideration when doing the figures. If i do get hold of a old steam engine then those with access to the methane reactor page, might well get to see how it would used. Failing that if we can do some more modeling in matlab, it might be worth getting a custom one built to try out (tiny scale).

The reason for pre heating is so we can keep down the amount of gas we need to keep in the lab inside the reactors. Currently for pre treatment we use other means to get the same effect, on a small scale like that its easier and safer but proves the concept anyway. Just as an aside, if it worked on the lab scale then upgrading to trial size would mean you could use a custom built engine to get the figures.

Same with turbines, we dont use real turbine to make electric from lab scale, we heat water and measure energy produced compared to gas produced and energy used etc. So its roughly the same thing. Just before doing the post it occurred to me, it might also provide a way to use some the waste oxygen from one the microbial cell processes. I will post the pics and info here if we go that route (well what info i can post).

Another side note, I get to visit a liquid salt boiler at a uni in a few weeks time. Brave people working with a molten salt at that temp!!

 

[tcmtech]

So is the end goal to turn your excess methane into electrical power via a Combustion to Mechanical to Electrical conversion process or is there more to this concept?

 

[large_ghostman]

So is the end goal to turn your excess methane into electrical power via a Combustion to Mechanical to Electrical conversion process or is there more to this concept?

Alot more to it than that. Most power stations take a fuel convert to steam then mechanical then electrical energy anyway. The differences are mainly the fuel and mechanical side wiht some exceptions obviously.

Gas powered could go both ways in theory, if small enough you could inject gas into a engine to drive generator directly, or you could use that gas to heat water, (thas a CHAPS type system,,, Combined Heat And Power) the steam drives a turbine and excess or residual heat from the water is diverted to use as heat. So that kind of thing is standard already and has been a long time.

Nuclear heats water, generates steam and drives turbines connected to generators, although newer systems are different. Coal is pretty much the same, big ass boilers boiling water..... Bio Digesters can have several setups based around the primary fuel source thats digested, some of the low grade sources do beer when pretreated, the methods used to pre treat are normally electrically driven in some form or other and require other equipment.

Same with some of the post treatment stuff, what I was pointing out was if you got clever with a steam engine, then some of the methods used to pre treat low grade high carbon sources, could use a slightly modified steam engine, so you would save on equipment for a start and to some degree on electric, you still take the same energy out the system but the process is eater and cheaper. A steam engine runs generators no problem, stick a few things on them or build them slightly differently and you could kill several birds with one stone.

When you didnt need to run pre treatments then you could simply inject the gas into engines connected to generators, which how some the smaller units work anyway. Alot of it comes down to scale and the primary source of fuel for the digester.

Its similar in principle to another common practice involving a venturi, the way its normally done is to use a pump to force material through a venturi, its fairly power hungry. Depending on set up we run venturis another way, we dont use pumps or any system energy. We use gravity, so alot of what i was saying is based on an idea to take advantage of how some types of steam engine work, or i guess you could simply say make more use of the energy they produce instead of just the heated water driving a generator.

Yes its slightly cryptic, but we havnt tried it out yet, it could prove useless or it could prove to up efficiency considerably, i m not going to post the entire idea on a open forum yet! But i was asked to post a little on some the things we are trying out. A bit like the new pellets for pellet boilers (again these are CHAP systems), we are making some new batches that something normally discarded, turning them into a fuel pellet uses up something normally discarded (so less waste in land fill etc) and is cheaper to get hold of so cheaper pellets.

We dont have one of those really fancy pellet machines, ours is a bit of a cobble but produces great pellets . But i confess to coveting one the new £150,000 pallet to pellet machines at a recent expo on waste equipment. Also first time i have sat in the cab of a brand new £400,000 'garbage truck' as you would call them over there.

 

[tcmtech]

if small enough you could inject gas into a engine to drive generator directly, or you could use that gas to heat water, (thas a CHAPS type system,,, Combined Heat And Power) the steam drives a turbine and excess or residual heat from the water is diverted to use as heat. So that kind of thing is standard already and has been a long time.

Yes, I am familiar with that concept. In fact I have been putting some serious thought into setting up a long term test rig to both generate my primary home power, plus maybe even sell back at profit, while also capturing as much of the excess engine and exhaust heat as reasonably possible for home heating using a old school Mercedes I4 industrial diesel with lowish hours I picked up last year cheap.

For a long time my local utility has had a 1:1 co-gen by back and or KWH banking program which would allow me to co gen power all winter off such a rig and then take those banked KWH's back the rest of the year for zero cost beyond my standard utility connection service fee, which if I co-generate enough that sell back money can be credited against those costs too.

I don't know if they still have the program in place but if they do then it would be a worthy experiment to play with. Its low priority right now but given my rate of used oil collection grossly out running my usage I need to start looking at a more practical, and possibly minimally profitable, way to burn it up and right now electrical co-gen , with optional home heating, looks to be the most realistic way for doing that.

As for your project I would recommend looking at the realistic production capacity plus efficiency numbers plus technical and bureaucratic cost limitations behind the various concepts you can come up with.

Also being a low density vapor fuel you're going to have to produce a lot of it just to run a small engine.

Odds are a small purpose built methane fueled IC industrial duty engine and co-gen setup (overspun induction motors make very good and simple co-gen units with minimal extra controls required) will likely work out to being the simplest most cost effective way to go even if its over all efficiency is marginal. Everything beyond that is going to be more complex and costly as the conversion efficiency goes up.

Fuel fired or steam driven turbines are simple but costly to own and as their size goes down their efficiency drops fairly fast too.

Then add in that any boiler plus other systems to make a steam turbine or reciprocating engine work is even more complex plus will have lots of other bureaucratic hurdles to overcome too, and we both know bureaucracy is costly no matter what side your playing for.

My guess is that on the micro scale level a simple IC engine based co-gen is going to work out best on cost and practicality even if its overall efficiency is substantially lower than anything else.

 

[Western]

I recall that when I was watching this sort of thing 20 years ago ... there was thermo electric generator capable of 5kW ... about 2 foot cubed in size ... about to be released for sale within months.

I kept watching for a while but nothing ever came of it. The information released at the time certainly looked solid ... very elaborate diagrams and views of it ... but either a hoax or simply didn't work like they said.

 

[Western]

If **broken link removed** were scaled up (and price scaled down) ... heat to electricity would be a lot simpler.

A Youtube video of the system.

Still nothing like 5kW though!!!

 

[large_ghostman]

Yes, I am familiar with that concept. In fact I have been putting some serious thought into setting up a long term test rig to both generate my primary home power, plus maybe even sell back at profit, while also capturing as much of the excess engine and exhaust heat as reasonably possible for home heating using a old school Mercedes I4 industrial diesel with lowish hours I picked up last year cheap.

For a long time my local utility has had a 1:1 co-gen by back and or KWH banking program which would allow me to co gen power all winter off such a rig and then take those banked KWH's back the rest of the year for zero cost beyond my standard utility connection service fee, which if I co-generate enough that sell back money can be credited against those costs too.

I don't know if they still have the program in place but if they do then it would be a worthy experiment to play with. Its low priority right now but given my rate of used oil collection grossly out running my usage I need to start looking at a more practical, and possibly minimally profitable, way to burn it up and right now electrical co-gen , with optional home heating, looks to be the most realistic way for doing that.

As for your project I would recommend looking at the realistic production capacity plus efficiency numbers plus technical and bureaucratic cost limitations behind the various concepts you can come up with.

Also being a low density vapor fuel you're going to have to produce a lot of it just to run a small engine.

Odds are a small purpose built methane fueled IC industrial duty engine and co-gen setup (overspun induction motors make very good and simple co-gen units with minimal extra controls required) will likely work out to being the simplest most cost effective way to go even if its over all efficiency is marginal. Everything beyond that is going to be more complex and costly as the conversion efficiency goes up.

Fuel fired or steam driven turbines are simple but costly to own and as their size goes down their efficiency drops fairly fast too.

Then add in that any boiler plus other systems to make a steam turbine or reciprocating engine work is even more complex plus will have lots of other bureaucratic hurdles to overcome too, and we both know bureaucracy is costly no matter what side your playing for.

My guess is that on the micro scale level a simple IC engine based co-gen is going to work out best on cost and practicality even if its overall efficiency is substantially lower than anything else.

The system works, infact there is nothing revolutionary about it. The one and only difference is using some of the normal mechanical motion for a different purpose when needed, then switch over to normal generation.

As for the density, your wrong, it has more power than petrol and here they compress and use like normal LPG (seen alot in the UK on forklift trucks and some cars) or you simply compress to normal grid pressure. Last few years bio methane has been growing for national grid injection. The problem used to be generating enough gas,these problems are now being solved with newer systems. Natural Gas is only Methane and we have had that years, bringing bio methane upto the high spec for grid injection isnt difficult if you build the reactor right in the first place.

This is one reason batch systems are going out of favor, look at a bell curve for a normal batch system. There is no flat spot at the top, with a continuous flow system you can keep a very very long flat line. The big problem has always been convincing people that single module systems dont work well, multi module guys call those 'poorly working microbe cells'!

You might know what CHAPS is, but in another thread people had trouble understanding what the acronyms stood for, so i said i would explain any i used. You dont dribble raw bio gas into a engine anyway, first its got to cleaned. Not sure what our grid pressure is now, i should know but cant remember, i know my home system is roughly 11psi higher because i have a pressure drop in my system due to how i originally did it.

 

[cowboybob]

Don't know your power requirements, but for a test bed, would something like this be of interest?:

Admittedly small, but I have one and it produces a remarkable amount of torque (not quantified but not unusual for a steam engine of this type). It's self-starting and reversible. They also sell one with ball bearings for the drive shaft.

CNC produced and no need for gaskets: seals up tight as a drum when at operating temp. Only seals are o-rings on the pistons. It'll run (with no load) with as little as 5PSI. Combined speed/forward/reverse control can be controlled with a small RC servo. Boilers can be bought elsewhere.

 

[large_ghostman]

Don't know your power requirements, but for a test bed, would something like this be of interest?:
View attachment 112889
Admittedly small, but I have one and it produces a remarkable amount of torque (not quantified but not unusual for a steam engine of this type). It's self-starting and reversible. They also sell one with ball bearings for the drive shaft.

CNC produced and no need for gaskets. Only seals are o-rings on the pistons. It'll run (with no load) with as little as 5PSI. Combined speed/forward/reverse control can be controlled with a small RC servo. Boilers can be bought elsewhere.

ERM no idea lol, i was looking at mamood things, that looks more powerful, if you have one you want to lend me then great i would give it try. Does it have a water boiler? or do you use a separate boiler?

 

[large_ghostman]

This is the kind of thing we are looking at
**broken link removed**

Hopefully cheaper but thats a collectors brand and the most common. We want to modify it by adding some things on, not sure how yours works, do you have a you tube link?

Or ven this because itdosnt have to move

**broken link removed**

 

[large_ghostman]

Sorry seen the boiler thing at the end. HMM, that isnt something i seen before, we have funny boiler rules. But i would love to take one of things i linked to and modify the boiler to route to the beast you posted. You have given me an idea, if you got one you could lend us, then great i would appreciate it, i can try and get one with a boiler and connect the boiler to it.

 

[cowboybob]

ERM no idea lol, i was looking at mamood things, that looks more powerful, if you have one you want to lend me then great i would give it try. ...

No problem.

... Does it have a water boiler? or do you use a separate boiler?

It will need one. The one I made isn't so good...I hunt around and see what I can find.

 

[large_ghostman]

No problem.

It will need one. The one I made isn't so good...I hunt around and see what I can find.

**broken link removed**

To get around the rules, i could use a boiler like this, dosnt have to be great, do you have links to that engine? very interesting design

I will try and get the mods drawn up in a format i can email you, actually the last boiler i linked to and ones of that type have part of the mod on them..... so i might be able to botch the boiler one and use the piston bit.

 

[large_ghostman]

Look like the mamood boilers have a modified safety valve available (approved ones), that can take the pressure upto 25psi, but they do ones from 25 psi to 60psi, i would stick with 15-25 psi with a older boiler. Its got to run a BLDC and another type of piston (think vacuum). So as long as we can do this with a small engine and take the readings, we should get an idea if its more efficient than the current way.

Actually Ian (from GER) mentioned the possibility of adding some other mods. I need to find out more on steam engines, looks like its been forgotten about in favor of newer tech. But with bio gas your sort of going back in time anyway, so steam might live once again .

 

[large_ghostman]

**broken link removed**
its battered but dosnt wheels on anyway!! Plus those boilers are set at 11 psi, but rated and tested to take a modified release valve upto 60psi !!

 

[large_ghostman]

Have tracked down a boiler!! man they expensive here!! but it should power your engine and is a type that should be easy to modify. i hope the pipes are the same size lol, the engines i linked to, does anyone know if you can get T pieces etc in brass rod of that size?

 

[tcmtech]

As for the density, your wrong, it has more power than petrol and here they compress and use like normal LPG (seen alot in the UK on forklift trucks and some cars) or you simply compress to normal grid pressure. Last few years bio methane has been growing for national grid injection. The problem used to be generating enough gas,these problems are now being solved with newer systems. Natural Gas is only Methane and we have had that years, bringing bio methane upto the high spec for grid injection isnt difficult if you build the reactor right in the first place.

Yes, by mass its energy content is a bit higher than the other common fuels However when dealing with the stuff on the commercial scale its sold by the liquid gallon or the cubic unit of vapor which renders its Mass Energy Value status mute and even worse is that energy per unit of mass does not translate proportionally to mechanical energy output with equal efficiency either based on their use in a stock engine built for burning Gasoline or near gasoline type fuels.

In a a common stock non emissions compliant spark ignition type small engine it would break down something like this at best and far worse with a emission compliant one as I have come to find over the years.

Gasoline 25 - 35%
LPG 20 - 30%
LNG 15 - 25%
Hydrogen 10 - 20%

With the NG and Hydrogen having dismal efficiency and energy output numbers by engine displacement due to the engine not having the necessary high compression and proper camshaft profiles to make it convert said fuel energy most effectively into mechanical power.

Believe me I have ran dual fuel powered equipment and vehicles for longer than you have been alive, and even custom built my own dual fuel conversions plus engines to utilize fuels like LPG and NG, and there is zero fuel efficiency and power gains in NG (its horrifically lower on power and fuel efficiency) compared to LPG or Gasoline unless the engine is heavily modified to run it. Which is why if you look at any smaller honest rated LPG/NG fueled generators you will see it has a derated output on NG compared to LPG or gasoline.

In fact to make NG work as a efficient IC engine fuel it needs near diesel like compression ratios (slightly lower) that most stock gasoline fueled engines can not stand up to.

It may pack slightly more energy per unit of mass but unless it used in a purpose built engine its a very weak and inefficient fuel.
-----------------------------------------------------------------------

For those wondering how different fuels compare by common units of measure.

By mass (Pounds) per unit volume (US gallon).

Used oil ~7.2
Diesel ~7.1
Gasoline ~6.3
LPG ~4.25
Hydrogen 3.7
LNG ~ 3.49

Energy (BTU) per unit volume (US Gallon).

Hydrogen 250,000
Used oil 140,000 - 160,000
Diesel 135,000 - 145,000
Gasoline 110,000 - 120,000
LPG 83,000 - 91,000
LNG 75,000 - 83,000

Energy (BTU) per unit of mass (Pound)

Hydrogen 92,500
LNG ~21,500 - 23,800
Used oil ~19,400 - 22,200
LPG ~19,500 - 21,400
Diesel ~19,000 - 20,400
Gasoline ~17,450 - 19,000

https://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf
https://www.prometheusenergy.com/_pdf/LNGQuickFacts.pdf
**broken link removed**
https://www.nap.edu/read/12924/chapter/4#23
https://www.lth.se/fileadmin/kcfp/SICEC/f3SICEC_Delrapport2_Combustion_final.pdf
https://en.wikipedia.org/wiki/Stoichiometry

Possible environmental negative impact starting to show up with mass usage of NG too thanks to it's GWP value of ~28 - 36 and now very high volume and rapidly growing usage world wide.

https://www.usatoday.com/story/news...s-leaks-methane-beyond-epa-estimates/5452829/
https://www.epa.gov/ghgemissions/understanding-global-warming-potentials

 

[large_ghostman]

Talking of emissions i made it clear we are discussing BIO methane, take a look at this

Dont compare Bio Methane with natural gas produced from fossil fuels or LPG gas. Also we dont use 'crops' as a feedstock, i think i have tried to make it clear all our systems are designed to use waste products as the fuel, so the first three on that list apply to us, some of the other feed stocks we use are not listed but are all waste products and again all fall within the first 3 columns.

Yes, by mass its energy content is a bit higher than the other common fuels However when dealing with the stuff on the commercial scale its sold by the liquid gallon or the cubic unit of vapor which renders its Mass Energy Value status mute and even worse is that energy per unit of mass does not translate proportionally to mechanical energy output with equal efficiency either based on their use in a stock engine built for burning Gasoline or near gasoline type fuels.

Correct (ish) but those engines are gone in 2040, plus generator engines designed for Bio Methane plants use engines designed for the gas, so if you swap the gas for petrol in them you get the reverse of your figures.

Also modern dual fuel engines do much much better, hence the new Scania truck used by waitrose supermarket. Admittedly old engines dont do so well, but as time goes by they will be in museums and your yard, not on the road being used.

 

[large_ghostman]

For those wondering how different fuels compare by common units of measure.

By mass (Pounds) per unit volume (US gallon).

PLEASE NOTE

no where on that list is the fuel we are discussing! where in that list is BIO methane? Compressed natural gas is not BIO methane!! its a waste product from oil production

 

[cowboybob]

... Sorry seen the boiler thing at the end. HMM, that isnt something i seen before, we have funny boiler rules. But i would love to take one of things i linked to and modify the boiler to route to the beast you posted. You have given me an idea, if you got one you could lend us, then great i would appreciate it, i can try and get one with a boiler and connect the boiler to it. ...

Well, I do have the boiler I made for it. Might as well send it also since I'll have no use for it. I was going to use Butane as the fuel. It has a pressure gauge (no idea how accurate) but no pressure regulator. I have no idea of its bursting pressure, so use at your own risk !!

This engine also has a shaft with NO ball bearings (look at the pic above of the TRV1A, above), so it has to be oiled regularly. There is, however, a ball bearing mod available:

I will say that the darn thing was a lot of fun to build and play with !