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re: need advice for building an energy system
22 jun 2001
fbmcgalliard wrote:
>there are a lot of folk working with sterling and steam engines. were i to
>get specific it would literally take over the list...
go ahead fred :-) let's see some brand names and numbers...
>if you need more details, i suggest spending a bit of time with
>any of the hundred web sites for those interested.
any particular hundred? :-)
>...the penultimate question is not if it is an idea of any possible merit,
>or a waste of time, but if it can be made to work practically.
you might say that determines its merit.
>...that a heat pump will provide a gain in effectiveness is proved
>by those who use em to improve their bottom line electric bill.
>modifying one to do this job is as simple as choosing one that works
>with the house you are in and using an alternator to drive it's ac motor.
as simple as that. you've glossed over the heat-to-motion part again.
>...the stirling/steam engine chosen needs a bit of work.
agreed. (have you chosen one, then?)
>i have a pretty good grip on the thermodynamics of the beast, but
>actually picking one off the line that can operate efficiently with
>a 50-70 c temperature difference is not so easy. the stirling can
>probably do it.
do what? :-)
>the low temperature otec turbines designed to use the 30c temperature
>difference between the deep ocean and surface water show that it can
>be done, but not how best to do it for a household.
show what can be done? how much power do these turbines make,
at what efficiency? how big are they, and what do they cost?
they seem to have minimal relevance, if they don't show how
"it" can be done for a household.
>...practical engines in the power level and temperature range we want
>do not seem to be readily available. i would say we have some modest
>design development to do.
i'd say there's lots to do, mainly in raising development money :-)
some describe this as chickens and eggs. good stirling engines do not
exist, so there's no market for them, and nobody wants to develop one,
since nobody wants to buy any. some people say thermoacoustic engines
are cheaper, with piezoelectric elements and almost the same (low)
efficiency. they want to build them into oil furnaces to power the
blowers (with a much higher temp heat source.)
>the carnot efficiency is set by the temperature difference...
so you'd start with 60/(273+60), ie 18%, and go downhill from there,
with a real engine. say 5% overall heat-to-motion?
>i am not sure what you mean by "energy flow"...
as i understand your description, you suggest using a solar hot water
heat source, with the house as a cold sink, for some mythical stirling
engine which turns an alternator shaft which provides electricity for
a heat pump which helps heat the house... would this also provide all
the electricity the house needs in the winter? or would that come from
some mysterious but inexpensive photovoltaic house paint?
>...power levels are on the order of those we are burning to provide
>heat for the house as it stands, if the heat is electric. for a
>typical house this ought to be on the order of 10kw of total heat
>input i think, so the motor needs to be about 5-10 hp. (i am
>assuming gain from the heat pump here.)
care to explain this with some more details and numbers?
nick
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