Re: [Phys-l] Toying with Domestic Waste Heat Recovery

[Bernard Cleyet <bernardcleyet@redshift.com>]

Already Costco sells two attic fans -- I think both solar powered.   
Obviously for cooling on sunny days.  A friend discussed w/ me  
several years ago his plan to close drapes activated by either  
temperature or solar light.  I don't know if he succeeded, he's very  
busy w/ "all sorts" of similar projects.


bc  has temperature controlled window fans, and thinks > 22 C is too  
warm.


On 2009, Oct 05, , at 19:34, Brian Whatcott wrote:

> In the period since the idea of domestic energy conservation was
> discussed  here, I have put some thought into the topic.
> I was surprised at a scratch calculation concerning the cost of
>  mass flow of heated and cooled air into living quarters.
>
> It appears that a rather small temperature differential ( <2degC)
> easily covers the electrical cost of motivating that flow with a fan.
>
> The TMP36 is a precision temperature sensor that costs under $2.
> A microcontroller can simply convert its 10 mV/degC output.
> Solid state relays driven by 5 volt logic, each capable of
> controlling up to 25 amps of line power, cost around $7.
>  (Though this is very much more than the power required to motivate
> the desired flows)


much cut