[Shop-talk] 9,500 kWh of production in first year

[old dirtbeard]

----- Original Message ----- 
From: "Patton Dickson" <57healey at gmail.com>
To: "Wayne" <wmc_st at xxiii.com>
Cc: "Shop Talk List" <shop-talk at autox.team.net>
Sent: Wednesday, March 12, 2008 11:25 AM
Subject: Re: [Shop-talk] 9,500 kWh of production in first year


> We don't get the major tax credits in Texas that you get in CA, but I
> would be interested if it gets down to a 5 to 10 year ROI.  The
> geothermal heat pumps would really be a boost, but system cost is too
> high here at this time.
>
> I can't complain too much, based on lots of state and federal backing,
> Texas is now the #1 producer of wind power, and the growth is
> accelerating.
>
> With our outrageous summers, the trend here is radiant heat barriers.
> I may try the ceramic paint this spring.
>
> Patton

Patton,

One nice thing about the PV arrays on your roof is that they sit 4-6 inches 
above the roof so that air flow underneath them will cool them (they 
generally are efficiency rated at 68F degrees, and their efficiency drops as 
the temperature rises).

As a result, they functionally as tremendously effective "sun shades" for 
your roof, totally blocking the sun from your roof where they are mounted 
and they circulate cool air between them and your roof. Even on a "Texas 
summer day," the roof under your panels will be cool to the touch.

This can decrease attic temperatures greatly and also reduce the amount of 
electricity you need to use for AC (here you might be able to size your 
array smaller based upon the AC energy savings). This would be even more 
important if you have vaulted ceilings on a south facing exposure.

I know someone who lives in Woodland Hills, CA, where it can get to 118F 
degrees, his house has vaulted ceilings and faces north-south. You need 
about 80-90 sq.ft. per kW of array, so for every kW you generate, you also 
shade up to 90 sq. ft. of your roof from the blazing sun. It is a win-win.

best,

doug