Posted by jeremy_ho on March 15, 2007, 10:40 pm
Well, lesson learned! Since we are still talking about a off-grid
system. Can you tell me how do I handle the ground on the inverter?
Does it need to be tied the earth ground or is that a no no? I
searched and there is not alot of information, where does the
inverter's AC ground come from? The DC negative??
Do you guys know anything about "load switching" a device that
automatically jumps to use the grid power, hopefully it does not cost
Lets assume my interest is still to convert this 1 circuitin which 90%
of it is my computer room. (yes I realize I need more panels.. alot
Posted by N9WOS on March 16, 2007, 12:15 am
For cheap portable inverters that you get at the supermarket. You want an AC
plug that has a pigtail ground that you can hook to a solid ground. The
ground pin of the plugs on the AC side isn't usual grounded to the DC
ground, or the inverter case. Don't ground the common on the outlet plugs.
Both output wires float above ground. You will do damage if you to try to
ground one of the two current carrying terminals.
For higher price inverters, designed for permanently installed house use you
will have a terminal on it's case that is designated for equipment
grounding. You will hook that to a ground rod.
There may be ready made equipment out there that would do that.
Other people will probably point you to some examples.
But one could be made with a heavy duty DPDT relay and a small bit of
circuitry that monitors battery voltage..
Normally though, for large installations, you would use a grid tie inverter
which would do that automatically.
What do you primarily do with your computer? Could you use a slightly less
powerful computer for most of your daily computer usage? A computer that
could be ran off of a 100 watts or so of PV panels. You can buy a pretty
good laptop for the price of the panels that it would take to run a computer
pulling 400W for 8 hours a day. Something like 800W of panels for a price of
over $000. I think I would be looking for a good laptop myself.
There is two sides to running stuff off of solar power. You don't just try
to get enough PV power to run what you already have. You have to work at
reducing the load that you have to run off of the PV panels. Because the
cost of the extra PV panels that it would take to run the existing equipment
will probably be more than the cost of a new unit that uses less power than
the old one.
And, maybe you should look for other things that you could run with a 100 to
150 watts of PV panels. If you have a moderate amount of CF lighting, or
other small appliances that you use on a regular schedule, you could power a
decent portion of the house. With 150W of PV panels, and 600Wh a day. You
would be talking about six 12W CF's run 8 hours a day. twelve 12W CF's ran 4
hours a day. Fifty CF's ran one hour a day.
Side benefit. If power goes out, you still got lights. :-)
Posted by jeremy_ho on March 16, 2007, 2:05 am
Yes, I am assuming it takes 400W, maybe not, maybe like 70W and then
25W for the LCD screen, I have a kill-a-watt on order so that should
solve some of the mystery. Without it I have to estimate. I do
think I can move the computer use to a laptop, solar or not, probably
save a lot of power over 8 hours a day. After all we don't need 400W
of power to post to newsgroup and surf the web :)
but I am saving 7 cents "worth" of electricity a day @ 600Wh.. it
takes 31 years to get even with the panel cost at $00. I can look
at it as a backup battery system to justify the cost.. but not have it
to gain edge over the PG&E bill.
I have made a new post at the bottom about this realization
Posted by N9WOS on March 16, 2007, 3:03 am
Yes, at current panel prices, there isn't much of an economic incentive to
use PV systems to offset grid usage. PV in that application is mainly more
of an environmentalist statement than anything else, right now.
But that doesn't mean that people can't have fun playing around with small
systems (getting their feet wet) until the price comes down.
The main area where PV stands out is where you don't have grid power, and it
would cost a lot of money to get it. A lot of times, the cost of running the
power line to the house is less than a PV system to run the house. In
situations like that, the PV system will pay for it's self on day one.
It will remain like that until panel prices drop to $ a watt, or $ a watt.
When you see $ a watt panels, then they there will be viable payback by
using them to offset grid usage.
When you can buy a 160W panel for $60 to $20 then you are getting into a
range where there would be payback in your application.
Posted by dold on March 14, 2007, 5:50 pm
That might be about right for a grid-tie system, no batteries, installed.
Self-installed gets a lower rebate rate.
At today's "e-1" rates, maybe, but the rates are going up, and you do want
the time-of-use meter to take advantage of net metering, where your energy
push during peak periods is worth more dollars than the energy you are
drawing from the grid at night. Based on old rates and no interest on the
loan, my solar system would pay off in 18 years.
http://cdold.home.mchsi.com/Solar-generation.htm $643 avoided in 2006.
Solar provided 59% of the energy I consumed, but because of the rate tiers
and TOU, that was 82% of dollars. That could make the payments on a 20
year loan for the system.
The rules have changed, and continue to change. There is an interim
solution right now in PG&E territory that you may still be able to get.
E-7 is good, E-6 is the future, E-1 is probably not suited for solar.
http://pge.com/suppliers_purchasing/new_generator/ if you are served by
PG&E. There are some out-of-date links, and some links that are not
obviously for larger systems than you are likely to install.
Completed Systems, 1998 to Present
This is an Excel sheet that you can sort by zip code or manufacturer, or
I am happy with my installer http://www.sunpowergeo.com/index.html
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5