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Solar steam piston? Answered

Right. Still hung up on this whole solar energy thing I've been looking into steam but it all seems: complicated, dangerous, expensive, and all kinds of freakin hassle. I think this is largely because people working in this field now are just trying to plug solar energy into where the fire would normally go, but in many ways light is a lot more versatile, and this might take a complete rethink. So, after twenty minutes of ill-informed and distracted thought, how about this: Two or more pistons, each with a little bit of water or other fluid. Base is thick glass, both attached to a shaft or gear to generate rotation. Concentrated light (like 6 kW worth, or whatever) is shone in through the base of one piston. The fluid vaporises and the piston expands. When it's fully extended the light beam flips over to the other piston. That one starts expanding while the first one starts contracting. you might have some sort of heat sink which is oly applied during the contraction bit. This would be fairly low speed, but should generate a fair bit of torque and would be really really simple. Someone just stole my patent, didn't they?



Build your own

Check out http://greensteamengine.com He has video of one of his steam engines running on solar heated water. simply design, low cost for plans. might be a place to start.

Yeah, saw that one. Seems pretty good, but possibly a little beyond the easily home makeable, and can't find anyway any actual numbers on efficiency other than "extremely efficient".
I hat it when they don't give the numbers...

You'd be better off using existing steam technology run off the 6Kw heat supply. To condense the steam you just generated you'd need to add cooling. Then there's sealing, the mechanics of 'flipping' the light etc... L

It is existing steam technology, it's just salvaging a pneumatic piston instead of making one, and building the boiler and reondensor into the unit as a closed system. Flipping the light would be the easiest part. I'm not explaining it well, let me do an animatic.

A transparent piston is not existing technology, neither is an in-piston boiler or condenser. Yeah, you could mechanically-flip fairly easily I suppose, but the whole concept is not as good as simply using solar power to produce a steady supply of steam. (I'll look at those links now) L

The fluid resevoir would be external and just plug into the cylinder's inlet. You could make this out of a bit of steel tube with a well fixed glass plug. The metal walls of the cylinder would act as a condensor, they'd probabaly need to be insulated or heatsunk to get the condesion timing right.

You're thinking of a "death ray" flash-boil, quick enough that gas pressure acts before too much cooling occurs? L

I happen to recall a cartoon of a Patent Attourney and his client standing at a window. The Attourney is holding an outlandish ray gun, and saying: "Death ray? Fiddlesticks! They don't even fall down."

That's interesting, I have another Death Ray thread going here, but that's actually literally about a Death Ray... But, yes, pretty much as you say.

solar pannel and somone answer my qeustion how to boost pictochat range send/ receive

What do you think about the rotary cam, as well? I just sort of came up with it while thinking about rotational motion. Not sure if it's already been done.

I like your cam design, assuming there aren't any horrible engineering challenges associated with it, but the engine appears to be a reinvention of a single-acting steam engine. I'm with lemonie, I think that working in the requirements of solar heating and a pressure operated piston engine you would be better with solar heating a boiler and using the steam from that.

Specifically, I don't think you can alternately heat and cool your cylinders enough to get the temperature differential required for good efficiency without wasting a huge amount of energy.. heating and cooling the cylinders. The engine appears to be lacking any kind of regenerator, and by the time you have changed your design to have a hot and cold "end" and a regen you are teetering on the Stirling anyway.

IANAengine driver so take this with a grain or two of NaCl but I suspect one of the existing engine technologies would give better overall performance.

Something else you may or may not be interested in is the Minto Wheel (apologies if I've already suggested it, even though I don't think it's very practical I love the design of this thing), a heat engine that uses low-boiling-point fluid like butane, using the same principle as the drinking bird (but on a larger scale). The aforementioned limit on efficiency using low temperature differentials means they will never be very practical using just ambient sun-warmed water, but with a higher dT and a suitable working fluid it could potentially work better.

> you would be better with solar heating a boiler and using the steam from > that. No doubt, and given the option I'll probabaly just buy for myself some reasonably powerful steam or Stirling engine off the net. The main point if this thing here tho, and I should have said this from the start, is that I'm trying to develop power options for the developing world where they have no cash and very little option when it comes to generating electricty and motion. So i'm trying to think of things like this as some way of turning salvageable parts into basically anything which you can get motion out of. I know this will be inefficient, but all it has to do is generate 12-48v and be practically free. And the easier it is to put together the better. > I don't think you can alternately heat and cool your cylinders enough to get > the temperature differential required The cylinder wall will only ever act as a condensor for the steam. The heat will go direfctly into the liquid when it's in the resevoir. I'm thinking the cylinder will proabably be best insulated, so the steam only starts to seriously recondense when it's nearing the end of the expansion. Alternately, it might be necessary to somehow spray unevaporated liquid into the cylinder to condense the steam. But this would obviously be more complicated. Regenerator? To reuse lost heat? Hmm, will have to give that some thought. Don't know if it would be an option tho, if the heat's going in as light... Yeah the Minto wheel is a nice design. I'll wait til someone does a 1kW model for cheap.

I was also thinking... the contracting cylinder, especially if it's rapidly recondensed by a spray of liquid, wll be putting a fair amount of suction on the expanding cylinder, greatly reducing that cylinder's internal pressure. This will make the liquid there a lot easier to boil. You might even get some kind of 'flash steam' situation.

Have you seen the workings of the Newcomen engine? Sounds a lot like what you are describing- a single-acting cylinder that is driven outwards by boiling water and then "sucked" back in by steam condensation driven by water injection.

I'm not saying "I told you so", just illustrating that the design of the traditional steam engine was driven by exactly these engineering challenges. (Also because in my own way I have a terrible habit of reinventing wheels so now make myself research prior art before embarking on invention).

Ah. All that 'complete rethink' talk has you thinking I'm trying to create something new. I'm not. In fact nothing would make me happier than discovering someone else has already done exactly this, as it would save me all the hard work and they've no doubt done it better.

Yup. As much a fan of Stirling as I am, in principle, they're just not a viable option for backyard energy production. Yet. Companies have designed and made really nice, efficient, powerful enigines which they're just waiting for the market to develop before they'll actually let us uy one. And then it remains to be seen how much they'll cost. So, for the time being, less powerful, less efficient, but really basic and improviseable seems to be the winner on the day.

What are these really nice, efficient, powerful engines which you speak of? L

You can buy Stirling engines. Have you made enquiries to these people about sales? (Not that I think you'd be buying one but out of general interest) L

My first idea was just to buy something, but so far I have't found anything at all, let alone cost effective. If you find anything please let me know.

I think the key problem with those is "cost effective". Leaving aside size etc. those probably produce output of the order of milliwatts, so at a cost of possibly tens of thousands of (CURRENCY_UNIT) per watt they aren't a practical power supply. For some reason toy/model engines with no practical use are sold all over the place, and people buy them for comparitively extortionate prices, but as soon as someone wants a large commercial engine that they would pay thousands of CURRENCY_UNITs for you can't find them anywhere. I suppose one (excessively complicated, like all the best ideas) way would be to buy one of the commercial gas-fired ones sugarandfat mentioned and remove the gas system. If the engine requires a stream of hot air (ie gas flame) to run, you could replace the collector of your concentrated solar collector with black porous rock or ceramic in a glass enclosure, and pump air through/over it. Might be crazy talk or it might be a workable principle, just brainstorming laterally outside the box.

Hmm. for stream of hot air replace with steam? L

Did you check out the homebuilt wood pellet fired stirling engine on Youtube? It's worth a look, it strikes me as being like a steam engine (better efficiency than a LTD Stirling, reasonable power to bulkiness, no fancy sealed-hydrogen stuff required).

I think the problem with your design as it stands is that the piston will never be a complete seal so you will gradually lose the working fluid to leakage, at which point you have to introduce valves into the cylinder and you are reinventing the steam engine. If the piston is a complete seal, you will lose a lot of energy to friction and it will wear quickly.

Steam engines are a decades-established and ubiquitous technology- why not see if a commercial steam engine or a Stirling like the YouTube example can be adapted to your requirements? I'm sure your concept could work but I doubt you would get better sun-to-shaft efficiency than sun-firing an existing engine type that has been refined since the Industrial Revolution.

I had a look at that one and others. Seems promising, let's see if someone can get a kiloWatt. I'm not really hoping for huge efficiency on this design, just that it be as easy to make and maintain as possible. This would also be very scaleable.