Exhaust Heat Recovery - Steam Power

[Wonderboy]

A quick look returned this page. May be a good starting point because it looks like ebay is useless for what we're looking for.

I haven't seen a Stirling engine do any work aside from rotating its own shaft.

Probably because you've only seen toys. watch that video or look into commercial solar power generation via stirling engines and parabolic mirrors. Stirling engines can get pretty serious.

[Daox]

Alright fellas, back on topic here. If you want to talk about turbos and peltiers or other ideas please start your own thread (or post in one of the many already started).

Okay, so steam power from exhaust heat. If we can recapture even 5% of that heat energy, we would harvest 450W which is enough to charge the battery without any drag on the engine. Anything more than that is simply icing on the cake to do whatever we want with it. I can't imagine it will be incredibly hard to capture 5%.

Does anyone have any ideas on any turbines we could use to spin the alternator? I've thought of some things, but they all require machined parts which isn't real DIY friendly. Something welded up might work, but balancing becomes an issue. I suppose that could also be done by hand though.

[Daox]

Here is a quick idea of what I'm thinking. Most of this can all be done pretty easily with a bit of welding and some steel pipe and fittings. The turbine is the only problem as of right now.

So, the beauty of it is the incredible simplicity and thus low cost. I realize efficiency will likely be lacking, but we don't need high efficiency to produce great results.

[Wonderboy]

Alright fellas, back on topic here.

Wait, what? How is the stirling engine not on topic. The video I posted clearly shows a stirling engine receiving roughly the same amount of heat seen in exhaust systems cranking away with enough steady momentum to drive an alternator. No steam or water required, just heat and some occasional lubrication. The upfront cost of a steam tubrine right-sized and shaped appropriately will probably cost similar to an appropriate stirling engine. Did I miss out on some previous discussion here about this that debunked the stirling idea?

[Daox]

Turbos, TEC/peltiers, and others can be discussed elsewhere. Stirling is relevant as the steam could be used to heat the engine. I'd like to keep the discussion on how we could use the steam energy in this thread. We haven't really talked about this before AFAIK.

[Daox]

Actually, I think I might have a cheap way of making a turbine. Start with a piece of bar stock, and drill a bunch of holes in it radially. You might have to start with larger holes and then use smaller ones to drill deep enough. But, you could do this all with a drill press.

[MetroMPG]

Ah - so the jet of steam would be aimed at the holes to spin the bar. Gotcha.

[MetroMPG]

Have you done any rough calcs about how much power you can expect to capture from a certain PSI / nozzle size?

Before you start machining parts, might be worth looking into.

I wouldn't really know where to start.

[320touring]

the alternators fitted to the e30 have a sort of fanblade/waterwheel setup on the pulley driven by the belt-could that be modded to produce something similar to the hole solution you've suggested?

Essentially then you just need to get the steam to drive the alt.

Also what consideration haave you given to rusting to the exhaust?

Its a great idea, but what effect will the additional sleeve on drag under the car if it hangs lower than the rest of the exhaust, or do you envisage using the setup on the downpipe or manifold?

[Wonderboy]

I'll be right with you on the steam brainstorm as soon as I'm convinced that the stirling solution is either not viable or cost prohibitive. It seems to me that anything that can get the job done while avoiding carrying a reservoir of water around (even a small one) may be the better choice. I'm not trying to start an argument here. Believe me, I don't want to waste time just for the sake of argument. I think trying to harness this extreme heat is an excellent idea. With a bit more google research, it looks like it was discussed here on EM at one point (with little result). I also found this study that appears to be legit, and claims to have recovered 3% of the heat capacity of exhaust gas. They said it could be improved upon, which I'm sure is the case. At least that's something to start with and shoot for with a steam turbine. I won't poke at this stirling idea until I've done a little more digging, because I have yet to put it to bed in my own mind in terms of physical limitation or monetary limitation. It still feels like it would work more efficiently than steam. Like I said, then I'll be with you in the steam turbine brainstorm.