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Newbie here - wants to do diy solar - needs help please!

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Posted by Synth on November 28, 2008, 11:24 pm
Hey all,

I'm a software developer and I'm trying to branch out and get into
solar power projects.  I really have no experience and don't even know
where to begin.  All I have is the 2 semesters of physics(long ago)
that I took in undergrad.

I was thinking about starting with the $00 diy solar project found
here: http://www.off-grid.net/2005/10/10/600-gets-your-house-on-solar-power/
but its a bit steep for my budget.  I was thinking of initially going
with a lower wattage(cheaper) PV module, but then if I want to expand,
the article says I won't be able to string them together if they
aren't the same wattage.  I don't even understand why...

Any readings that you all might recommend, especially primers on
electricity concepts.  I've googled around and have read many websites
about electricity basics(watts/amps/volts, etc) but I still feel under
prepared to get into this field.

Ultimately, I do have a project in mind: a solar powered hot dog
cart.  So, eventually I'll need a setup that can keep several gallons
of water warm all day long - as well as be semi-portable.  Also,
seeing as how I'm on a computer all day long, I'll like to get my
computer(~400W) off the grid, if possible.


Posted by Mauried on November 29, 2008, 3:58 am
On Fri, 28 Nov 2008 15:24:49 -0800 (PST), Synth

Unfortunately, getting into Solar in a meaningful way is going to be
expensive simply because Solar Panels are expensive.
You need to decide what you ultimately want to achieve then wait till
you have enough money to buy all the necessary components.
trying to go there on the cheap will find you ending up with a lot of
components you will have to junk or replace when you want to make the
whole system bigger.  
As a simple example, if you wanted to run your computer off the grid
for say 8 hours a day , since your computer needs 400 watts , thats a
total of 3200 watt hours or 3.2 KWH per day.
To generate this amount of power you would need a solar panel of
approx 600 watts and a battery of sufficient capacity to run the
computer at night if thats when you needed it .
If the computer needs to run for 4 hours at night, thats 1.6 KWH so a
battery of about double this would be needed to avoid completely
discharging the battery.
A 12 volt 300 AH battey would be ok, but this is a big battery.
You also need a 400 Watt Inverter.
The total cost of all this would be around $500 to $000.
Its an expensive business.
This is an approximate estimate and you may do things a bit cheaper
but if $00 is beyond your budget then Id wait ill you have some more
spare cash.

Posted by Synth on November 29, 2008, 5:28 am
 On Nov 28, 10:58pm, maur...@tpg.com.au (Mauried) wrote:

Thanks for your quick reply :)

Ok, so solar pv may not be the most efficient choice for a sustainable
power supply :-)  Do you have recommendations on alternative ideas?
The key considerations being that it generates enough power for around
8-12hrs of work(whether it be direct or through batteries) at a clip.
I definitely don't think wind would cut it and bio-desiel doesn't seem
truly sustainable(or am I wrong here).   Bear in mind, I'm not really
doing this to create a viable business idea.  I'd be completely happy
investing in a moderately pricey setup($k-$0k) and only operate on
the sunny weekends of the summer in order to spread sustainable
ideas.  However, I'd rather get my hands dirty on a smaller scale
project first and extrapolate out before really investing.

Someone who replied straight to my email, mentioned the use of a
heliostat to cook the hot dogs because of the fact that solar energy
is lost greatly when converting the suns energy from light, to
electricity, to heat.  In truth, I imagined running a hot dog cart
where they keep the hot dogs in hot water, and that's how they cook.
It seems doubtful that a heliostat could heat several gallons of water
constantly through a day.  Anyone want to run the math ;-)

Posted by Mauried on November 29, 2008, 11:13 am
 On Fri, 28 Nov 2008 21:28:22 -0800 (PST), Synth

Using Solar Power to electricially heat things up is insanely
Solar cells are around 14% efficient and cost around $ a watt or
Essentially Solar only makes sense when there is no other options
Whats wrong with just using gas, it will be much cheaper.

Posted by Eeyore on November 29, 2008, 11:28 am

Synth wrote:

It's a positively INSANE one.

Yes. REDUCE YOUR ENERGY *USE* ! Use CFL lighting, LCD TVs and PC screens.
your property. This can all be done for relatively little money and will 'save
environment' about 100 times more effectively.


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