Steam powered microturbine

I found a very neat 'Pelton wheel' on ebay , all alloy .
Mounts right up to a 'Denso' alternator with 17mm shaft ,
I was wondering about creating a steam boiler to power it ,
Could charge lead acid batteries off the alternator ,like its designed to do or possibly through a three phase transformer to supply mains voltages to low powered devices .

If we could tap off a KW in steam from my stove/boiler what kind of effeciencies could we expect at the output of the alternator ? or  if we needed a transformer to combine the three output lines of the alternator into a 'mains' like voltage .

Apart from the attendant dangers of high presure steam , my basic understanding of energies and effeciencies tells me that the transformer/motor/generator  is about as good a conversion of energies as we've come up with ,high 90's % with good design .

> 'Pelton wheel' on ebay , all alloy . Mounts right up to a 'Denso' alternator

Link?

https://www.ebay.com/itm/Pelton-Water-Wheel-Turbine-Aluminum-Micro-Hydro-Generator-w-Adapter-free-ship-US/201853521661?hash=item2eff684efd:g:Nr4AAOSwYXVYyIZj

designed for water, so the nylon lock nuts would have to go if you were using steam , I was thinking a stainless washing machine drum as a housing along with the door glass . Probably sound like an air raid siren 

I really don't think that a mechanism optimized for water flow will work in any efficient degree on steam.

Tubetec said:

If we could tap off a KW in steam from my stove/boiler what kind of effeciencies could we expect at the output of the alternator ?

Click to expand...

Best steam turbines have 50% efficiency; that's for very thorough design and implementation. With said turbine, you may expect charging your cell phone...

I do see commercial steam turbine generators using the Pelton principle .
Lots of 'Live Steam' videos on youtube , mostly reciprocating steam engines , but some turbines also .
Even 50% efficiency isnt bad at all , one guy with a shoebox sized boiler and a vintage twin cylinder engine was able to make 12v at 3amps with 40psi with a modified alternator , quite a bit more than you'd need to charge a cell phone. Scale things up a bit and you wouldnt be far off powering many smaller electrical items  from  renewable resources.

I hear the Irish government trying to push for photovoltaic generation  now too , but have they really factored in production and  'end of life ' of these toxic panels , my guess is not ,just like the 'low energy' light bulbs which were supposed to save the planet but actually cause even more environmental harm if and when they are thrown in the trash . Now they want to build a large photo electric generation facillity up the hill from me , have they even considered the potential down sides if the ground water that supplies the town ends up contaminated with  noxious substances ? Looks to me like the vast majority of what were being sold as 'environmentally friendly'  has its own filthy dirty secrets concealed by fraudulent lobbyists .

A steam turbine is proportioned differently than a water turbine. Maybe not a lot different. But the nozzle (which is not in this item) will be very different.

A major difference: water is much denser than air. Steam is not much denser than air. You have steam on the front one cup and air in the back of all 12 cups. That's a lot of air drag. Efficient steam turbines invariably exhaust into (and work in) "vacuum". Vacuum gets the last dreg of energy out of the steam; but also reduces the air drag on the turbine. Exhaust pressures run about 5% of atmospheric.

So you need a housing, that won't collapse under nearly full vacuum; and you need a Condenser to make that vacuum, and an air pump to get it started and an ejector to suck the water out of the condenser and back to the boiler. (Pumping hot condensate to waste is a dead loss.)

I don't think efficiency is even in your planning. This rig will be far over $100 to build, and I think 100 Watts is optimistic (even fantasy). Do you have electricity at your house already? Then 100 Watts is worth about 2 cents an hour. Even if fuel were free (it never is), you have to run 5,000 hours (6 months) just to cover your underestimated capital cost.

Pelton/impulse turbines work with steam but don't make full use of the steam. Steam leaks-back around the blades. "Good" steam turbines take steam pressure down in multiple stages so the differential pressure on each stage is less, back-leakage is less.

The Pelton is an excellent WATER wheel if pressure is high and full utilization is not essential. If I dammed my ditch 10 foot high, I would have a month of good power at snow-melt, and a day after any heavy rain. "Good power" being much closer to 100W max than anything to power a cooker or dryer. As my ditch is 300 feet from the house, and my land-drop is near 2 feet not 10 feet over a 300 foot run, this makes no sense even for driveway lights.

Turbine efficiency, especially steam, goes up significantly with scale. Toy turbines (like this) may never reach 5% efficiency, less counting boiler losses (typically high). Build it BIG, the inside volume goes up faster than the surface area, losses are relatively less, the output will pay for a lot of brain-work and insulation and complex regeneration, efficiency from fuel can be OTOO 50%.

For house-size power, IC piston engines edge-out steam turbines. I have a propane engine "whole house" generator for power failures. The cost to run it is shockingly higher than the cost to buy power off the street. Like 10X. If I did it full-time I could get a better price on fuel and get down to 5X. For all its line-losses, utility power is vastly cheaper than small-scale DIY power.

There are hot-air engines to sit on a wood-stove. The best will power a small fan to spread heat around the room.

Many thanks once again for the in-depth explanation Paul , 
I was starting to realise the commercial turbines were an order of magnitude more complicated  than  a  simple wheel and nozzle , a closed system as you said .
Unfortunately I have no stream/creek/fall on the land I live , so a water wheel isnt an option either.

Aside from the penalties of scale , I still like the 'Live steam' idea as a hobby ,  I see now there is a Chinese model maker doing some very nice reciprocating engines and accessories  , similar in style to 'Stuart Turner' models ,all machined from solid brass .
Every possible gadget has been reproduced in miniature including flyball governors and steam whistles .
Ok,  its never going to produce meaningful power , but it would look nice on the mantle piece .

In the winter you might be able to feed the waste steam into radiators to heat your abode.  Seems like a lot of work to keep the fire going. Very old school.

JR

Yeah radiators could make a half decent condenser , but of course plain domestic copper and steel heating systems probably arent up to the job of containing a vaccum ,an  old fashioned cast iron pipe and radiator might stand a chance of working alright .

Thing about all this that I didnt say was , fuel I can get without having to hand over cash , still not 'free' cause someone, somewhere has to pay ,but  it is from  rewnewable/managed resources and theres a never ending supply very close by .