|
|
re: a stupid question
4 feb 2004
george ghio wrote:
>> >what are the losses through a couple of inches of water and two layers
>> >of plastic?
>>
>> almost none for the water itself. the air-plastic interface would have
>> a fresnel loss of about 4%, with a lot less for polyethylene-water and
>> polyethylene-glass interfaces, with some sort of matching goo. you might
>> look up the refractive indices and work this out.
glass is 1.526. water is 1.33...
>> >how much energy is lost to pumping the water...
>>
>> ...70 watts max, as mentioned below.
>
>oh i am sorry i thought that the pumps ran for more than an hour.
watts vs watt-hours makes it clear the pumps can return
something like 50x more electrical power than they use.
>>the panels and mirrors don't move.
>
>explain this;
>
>at dawn, in full sun, the panels might see about
>0.9x0.9x0.9x800w/m^2x16'/6'
the polycarbonate cover transmission is 0.9, the mirror reflectance is
about 0.92, and i underestimated the duct transmission as 0.9. the 16/6
is the concentration ratio at dawn. how much sun bounces back out through
the cover or off the reflective endwalls?
>if neither the panels or mirrors move it would perhaps be better that
>the panels face south. faceing east to see sun rise?
horizontal panels seem easy to mount and cool, with a vertical reflector
facing south.
>> >what is the duty cycle of these pumps?
>>
>> perhaps 8 hours per day in july. less in winter, when more heat is needed.
>
>...what is the rated duty cycle of the named pump? 20%? 50%?
...100%, with a $33 price and a 3-year guarantee. they'll be in fairly clean
cool fresh water most of the time, altho they're tested in hot salty mud,
among other things.
>...what is the cost to set this up?
here's a partial materials list:
$3000(?) 6 sharp 165 w pv panels
2000 24 v grid-tie inverter
800 280' of unistrut
12 32' poly film ducts
66 2 24 v 21 gpm pumps
300 pump controls, hoses, etc.
400 288 ft^2 dynaglas
50 180 ft^2 epdm
88 256 ft^2 1" foil-faced foamboard
20 192 ft^2 metalized mylar film
-----
$6736 for 3 kw peak, with useful hot water, vs
$5800 for 800 w peak, with no hot water, for
a system with only the first three parts.
nick
|
|
