Re: PV solar design example

"John Larkin" <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:cqtd44h9qgjo7n2e9aipiu0fchvv3m1ot2@xxxxxxxxxx
How will a solar system do when it's cloudy for a week or two? Or when
the panels are covered with snow?

Well, if you're grid-tied, and the LLP (loss of load probability -- this is
the term the solar guys use) for solar is independent of that of the power
grid (approximately true), then the total LLP is just the product of the LLP
of each one, i.e., pretty small.

Note that for snow you're supposed to go out and brush'em off. :-) Maybe add
windshield wipers? :-)

For non-grid-tied systems, it's a question of whether you just want batteries
as a backup or a generator as well. In general a diesel generator is the
cheaper option, for very low LLPS... I recall reading some report on
Austrialian telco repeaters in the Outback where initially they used all solar
+ lots of batteries, but in a 2nd generation system went to solar + a few
batteries + a diesel generator. Since the repeater sites still required some
human maintenance, it was easy (cheap) to also have the maintenance guys bring
out enough fuel to top off the generators.

I've used PV design software that lets you play with all these variables.
It's somewhat more sophisticated than you might guess: They have a database of
weather data for a number of years (many decades in the largest cities) and --
knowing the time of year and your position on the planet -- can calculate a
pretty good statistical model of how much energy a PV system of a given size
will produce on average and what the standard deviations are. From there,
it's straightforward to size battery systems to get the LLP down to whatever
point you're willing to pay for, based on when you want to cry "uncle" and
just add a generator to the system.

With gas prices the way they are today, you're spending a lot for a gasoline
or diesel generator to make you a kWh, though -- somewhere around $0.70!
Still, easily worth it if you have to run it for a day or two compared to
losing a hundred bucks or more of frozen foods.

---Joel


.

Relevant Pages

  • Re: Solar charging: Real World
    ... The cost of a decent solar system seems the same as a small gen set. ... The cost to get half the watts of a 1000 watt Honda generator in solar is ... The 2 golf cart batts are fully charged using the tow vehicle ... I've got 2 solar panels, automatic charging, ...
    (rec.outdoors.rv-travel)
  • Re: Newbie question
    ... deadening the sound of the generator like that though. ... It will require a rather large..many thousand dollars and up for a solar ... collection and the electric hot water heater tank. ... Check the net for the basics of water tank installation..its easilly ...
    (misc.survivalism)
  • Re: Solar powered submarine planned
    ... UK - Plans have been unveiled for a solar ... generator would provide the submarine... ... few hours so they can use an electric motor and batteries. ... Ships will need fuel but there may be naval boats ...
    (sci.military.naval)
  • Re: PV solar design example
    ... grid, then the total LLP is just the product of the LLP ... The LLP of any PV solar system will always be above about 0.75. ... since a bit of clouds can shut off most of the solar power, ...
    (sci.electronics.design)
  • Re: 13W Solar Briefcase £49 any reviews !!!
    ... Portable solar generator built into a protective briefcase making it ... Includes 4A charge regulator ... The generator comes complete with an adjustable angle support that allows ... you to position the solar panels in prime sunlight. ...
    (uk.rec.caravanning)
Loading