[Stoves] New type of electricity generator suiteable for stoves - early development stage.

[Kevin Chisholm]

Dear Crispin

OK! If they have such temperatures, then it would certainly be alot more 
worthwhile. If 50% efficiency was attained, then with the same battery, 
the computer could be used twice as long. Additionally, the power 
generation device could be used as a part of the computer cooling 
system. Might be a good thing after all.

Best wishes,

Kevin

Crispin Pemberton-Pigott wrote:
> Dear Kevin
>
> Hang on....
>
> The temperature inside a laptop CPU is not the miserable 150 F that comes
> out of the fan.  Modern CPU's run red hot under the skin. The fan is so
> sized to limit the outlet temperature for human safety reasons. It has
> little to do with the temperature of the heat source.
>
> If a 4.0 gigahertz CPU runs at 400 C (750 F) then your calculation will
> yield an efficiency of 51%, right?
>
> At 600 C the result would be 59%. Not too bad compared with a diesel engine,
> or wind, or ethanol stove....
>
> Regards
> Crispin
>
> -----Original Message-----
> From: Kevin Chisholm [mailto:kchisholm at ca.inter.net] 
> Sent: March 30, 2008 5:13 PM
> To: crispin at newdawn.sz; Discussion of biomass cooking stoves
> Subject: Re: [Stoves] New type of electricity generator suiteable for stoves
> - early development stage.
>
> Dear Crispin
>
> They are targeting to reach 85% of Carnot Efficiency. Carnot Efficiency 
> is (T2-T1)/T2.
>
> If the effective tempeature attainable from the computer was 150 F, 
> (460+150 =610 Rankine), and the Office Temperature was 60 F, (520R), 
> then 100% Carnot efficiency would be (610-520)/610 = 90/610 = 14.75% , 
> 85% of which equals 12.5%
>
> 85% efficiency might be attainable with high temperature applications, 
> but it would be virtually impossible in low temperature applications. 
> The difference in "cold end temperature" and the ambient temperature 
> would probably be in teh range of 20 F, to keep heat exchanger size 
> reasonably small. That one factor alone would reduce the maximum Carnot 
> Efficiency to 70/610 = 11.5%.... that alone limits maximum efficiency to 
> 11.5/14.75 = 77.9% of Carnot.
>
> It looks like the Writer who put together the story traded off a bit of 
> perspective and fact for enthusiasm.
>
> Kevin
>
>
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