by Dan Casale
An Introduction To
Solar Electric For Your House
I’m so bright, I generate my own electricity ... I need
a T-shirt and a bumper sticker with that saying!
I was designing a base and space station power
generation system for a moon/Mars colony group
( www.1000planets.com), when a co-worker asked
me to help design a stand-alone solar power (PV)
system for an off-grid home she was planning to build.
As we worked through the design, I kept thinking, I
need one of these. The year was 2003, gas was at the ridiculously high price of $1.50/gallon, I had just purchased a
“you must be crazy to buy that thing” Prius and California
was doing a very innovative thing — energy deregulation.
Like any good project, the more research I did the more
options became apparent, and the more the project cost.
But here’s how I built my system.
While this might seem like the last thing to decide, it will
affect how the whole system is designed. Luckily for the home-owner, there are only two real options and one “fringe” option.
• Storage Option #1: Most homes are already connected
to the local utility grid, so the easiest storage method is
simply to spin the electric meter backwards. This option is
often referred to as “net-metering.” Not all utilities have a
net-metering provision, so this might be the first factor
limiting the size of your future system. I say this because if
you put on a large system and your power bill is negative,
you will quickly have the full undivided attention of the
utility company. Smaller “unauthorized” systems are often
referred to as “Gorilla Solar” systems.
• Storage Option #2: Batteries. If you have decided that
being attached to the local utility is not for you, or you want
a whole house UPS, then batteries are in your future.
• Storage Option #3: Hydrogen. Be the first person on your
block to invest in the hydrogen economy.
Solar panels require a large, south facing area that is
free from shadows. Figure about 100 square feet for each
1,000 watts of peak power production. Additionally, the
panels should be tilted at an angle equal to your latitude for
best year-round performance.
The roof is generally a winning location. However, most
roofs are not steep enough for optimum power production,
so some type of tilt-up racking may be necessary. The
available area is likely to be the second limiting factor on
the size of your future PV system.
There are two basic types of mounting systems: fixed
orientation or tracking. Each of these types has two options.
For the fixed orientation, the options are fixed or seasonally
adjustable. Seasonally adjustable racks are used to change
the panel angle to optimize winter and summer performance.
The two types of tracking systems are single axis and dual
axis. Single axis systems will track the sun across the sky while
dual axis systems track the sun across the seasons. Trackers follow the sun like flowers and can increase a system’s output by