build, buy a kit, or wait

[RonT]

Over the last couple of years I've been checking out the options for a low power electrical power source and have found little in the range of 50W to 500W. I'd like to have something that could power my amateur radio equipment (which is currently solar powered, which doesn't work well in winter), maybe even put in my vehicle for emergency battery charging. Being new on the list I don't know how well this ground has been covered before here. I tried to use the basic search engines but my searches were declined because the words I searched for were too common.

I would like some help in becoming current on projects to generate electricity in this power range. Are there designs for home construction, or kits available, or should I wait to see what comes along?

Before closing here is a little of my background. Our family lives in Yellowknife, NT, Canada, (62 degrees N). My line of work is avionics maintenance (over 30 years experience). Amateur radio is how I spend a lot of my time, with a bent towards emergency preparedness and emergency communications. Recently I purchased a Sherline lathe and hope to re-learn some of the skills taught me back in high school in 1970.

Ron T. (VE8RT)

[Geoff V]

Hello Ron

Not sure how much research you've managed to do so far, but to the best of my knowledge there are no kits and very few good designs for engines in the power range 50w-500w, for various reasons. Building an engine to produce 5w is fairly easy, but scaling them up to produce more power becomes increasingly difficult because the surface to volume ratio (hydraulic radius) quickly starts to work against you. Some of us are working in the power band that interests you and we are starting to get a 'good handle' on what is required for home built engines to produce these power outputs. The teachings in the recognised text books on the subject are of little value to the home constructor, although theoretically correct, the proportions only translate into practice with very sophisticated heat exchangers and when highly pressurised with Helium or Hydrogen. The home constructor is likely to be restricted to fairly simple heat exchangers and low pressurisation on Air, but we are finding ways to do it.

Just a couple of sources I would offer for starters are Andy Ross's book (free to download), lots of experience, but he did tend follow the 'learned teachings'.

http://stirlingbuilder.com/

Some good work on the required displacement ratio for our needs and a rather simplistic simulator that does however reflect the 'real world' quite well, at.

http://www.solarheatengines.com/

I must warn you that these engines are highly addictive and to date there is no known cure, so welcome aboard.

GeoffV

[RonT]

Thanks Geoff. I haven't done a lot of research and almost all of it has been through internet search engines. The online resources you mentioned will help me understand why there is this barrier to higher power home built engines. My thinking had been that over time improvements in materials, etc., would bring about affordable and doable solutions.
Something else that I was wondering about, why use Hydrogen and Helium, and not some other Noble gas in a Stirling engine?
While doing some internet research I did come across some higher powered, and expensive, commercial Stirling engines under development, are affordable commercial ones somewhere on the horizon?
Thanks for the addiction warning, financing the addiction will limit the degree to which I'm hooked :-)
Finally, any suggestions as where to look for a 5W model, or larger (multi-cylinder) to see how they built it?
Ron

[Geoff V]

Ron

The main problem for the Stirling cycle is the Infernal Combustion engine which will always be cheaper and more powerful per unit mass, all well and good until there are interuptions in the fuel supplies. Material development has over the years made a difference to SE's but has also benefited the ICE so commercially available SE's probably won't be on the shelves until the supply of liquid hydrocarbons becomes too expensive or unavailable.

Why Helium or Hydrogen, simply they both have far better thermal conductivity than Air (78% N2) and much lower viscosity hence lower pumping losses which are the main internal losses.

I can't suggest any commercially available 5w engines, not of any interest to me, but I'm sure other members will point you in the right direction.

GeoffV

[DIYStirlingGuy]

Ron,

This page has some good numbers on Thermal Conductivity and Specific Heat Capacity.

http://koolance.com/cooling101-heat-transfer

Justin

[RonT]

Thanks, I visited your homepage too, easy to understand and helpful. Lunch break is over, back to work!
Ron

[DIYStirlingGuy]

Glad to help. I'm still learning too.

Justin

[johnmaster]

I must warn you that these engines are highly addictive and to date there is no known cure, so welcome aboard.

GeoffV

I am finding the same thing! Almost as bad as turbochargers...