That is correct (your calculations)
I assumed (guessed) that the efficiency would be closer to 15%,
especially for something built by an enthusiast with little technical
information on his website. However I do a lot of assuming.
--
MK

Peter P. wrote:
> Martin Klingensmith <martin-distlists <at> nnytech.net> writes:
>  
>   
>> The web page says that "you can hear the shop air compressor running..."
>> It also says "It makes about . 5 horsepower" so I'm not sure if that's a
>> misplaced "."
>> It seems unlikely that there is enough energy from the sun in that
>> pi*r^2 area to produce 5 HP.
>>     
>
> The dish seems to be 14 foot ~= 4 meter dia. so its area is about 12m^2 and it
> could in theory handle 12kW of power from the sun. But 5hp is about 3.5kWe and
> this implies about 30% efficiency which is a little on the high side imho,
> especially for something that boils water. The figure could be true if the power
> needed to pressurize the water tank was disregarded in the calculation. With
> what I assume to be a 2+hp compressor there remain only at most 1.5hp for output
> which is about 1.1kW or about 9% efficiency and is credible for something that
> boils water imho (if it is well designed).
>
> Peter
>
>
>   


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