We recently visited a solar-powered site that had a supplementary wind-generation system. Seemed to work well for them to have wind power when the weather is bad, solar when it is good. Pretty windy place as well.
Chuck McCown - 3 wrote: > Here is a note I posted several days ago on the Motorola list about solar > powering. > > From: Chuck McCown [mailto:[EMAIL PROTECTED] > Sent: Friday, November 14, 2008 9:17 AM > To: Dave Crim > Subject: Re: solar > > > > Continuing on a bit, lets say you have 5 lousy days and one good sunny day > followed by 5 more lousy days. That one sunny day needs to store enough to > charge the batts totally. 75 watts * 5 days * 24hours * 1.25 (batter > efficiency loss) + (75watts * 24 hours) current day = 13050 watt hours. > > To make 13050 watt hours in one 10 hour day you go: > > 13050/.707*10=1845 watts. You need 1845 watts of panel to do this. That is > 24 times the load. > > So, my rule of thumb of 20 times the load is still a little shy of being > conservative. > > > > The thing that saves you in a situation like this is a massive battery. A > one month battery with 20 X panels will never fail due to a lack of sun > energy. > > A 2 week battery and 10X panels will fail now and then every single winter. > Sometimes for several days at a time. > > ----- Original Message ----- > > From: Chuck McCown > > To: [EMAIL PROTECTED] > > Sent: Friday, November 14, 2008 9:09 AM > > Subject: solar > > > > Several thing you may not be including. > > Assuming this panel is somewhere in this neck of the woods, December 21 > has 10 hours of time between runrise and sunset. > > But if you don't have tracking mounts (most don't) the amount of energy > you get out of a panel follows the first half of a sine wave. > > To estimate that energy, you integrate the area under the curve. That > will equal .707 of what you thought you were going to get. > > > > So, let's say you put up a 500 watt panel, your daily sunny output will be > an average of 353 watts. The sun shines for 10 hours solid and you store > 3530 watt hours in your battery. Now your load is on during the daytime, so > if you have a 75 watt load, you are now able to make 278 watts. You are > down to 2780 watt hours. You put in 2780 watt hours into a battery and you > get maybe 80% back out. So you have 2224 watt hour available (if you drain > the batts which is not good for them). > > > > You have 14 hours of darkness and actually more like 16 hours before the > panel starts making any useful amount of energy. 16*75=1200 watt hours. > > But that next day is not sunny, there is frost and a light coating of > snow. The whole works dies 16 hours later. About 9 pm. > > > > One other note, you only want to draw your batteries down no more than 10% > each night or they won't last long. That means a minimum of 12000 watt > hours. If that is a 12 volt system, 1000 amp hours. If it is a 24 volt > system, 500 amp hours. And that is a minimum because here we get a week > with snow and ice and no sun easy, sometimes two weeks. > > > > You really need a generator, less load, or a whole bunch more batts and > panels. > > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: [email protected] > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ > -- Randy Cosby Vice President InfoWest, Inc office: 435-773-6071 -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
