PV Gap

Chris Said:

Would a 80 watt solar panel be able to charge a 12 Volt Battery?

We Answered:

Look at it this way,

A 12 volt car battery that has 600 amp-hours of current storage has supposedly 7200 watts of power available (12v x 600 amp=7200 watts)

But in reality you would be lucky to get a third of that.

Anyway, if you run a 40 watt light bulb for say 10 hours you used 400 watts of power from that battery. Your solar panel in the middle of a sunny day might put out that 80 watts and when it does, it will take 5 hours to charge back that 400 watts of usage for that 40 watt light bulb.

So your 80 watt panel will place 80 watts of power back into your battery every hour. Of course if it is cloudy or early/late sun you might get as low as 5 watts an hour.

So it's just a balance equation, you have to calculate the total amount of watts your appliances and lights use per hour and calculate on average your panel is going to put around 50 watts per hour for about 12 hours a day ( about 600 watt-hr)

Claire Said:

...80 watt solar panel...?

We Answered:

Just to run some ball park numbers... if you are using $15,000 of electricity per year, then I'd guess you are using ~150,000 watt hours of electricity per year.

Now, take a look at the right most column in the linked file.
http://www.americanpv.com/pdf/res_on/pri…

The right most column will give you just over 20,500 watt hours of electricity per year. Therefore, you need about 7 of those systems each of which costs over $80,000 or you need to spend about $560,000 to offset your electric bill and actually, it would be closer to 10 systems and over $800,000 in order to generate enough power to offset the electricity you are still going to use at night.

This is why anyone looking at alternative energy first has to look at conservation.

Marsha Said:

how many 80 watt solar panels are needed to power a ranch style home?

We Answered:

Well, I have a 200 amp load center in my house. 110 volts x 200 amps = 22,000 watts (22 KW).

22,000 / 80 = 275

However, I can get by with the 7KW generator in my motorhome. So, let's say about 88.

That would still leave you enough extra most of the time to charge batteries. You would probably need a backup though in case of several days in a row in the winter of cloudy skies.

Jessie Said:

how will the inverter effect this project with 80 watt solar panel and 115Ah battery?

We Answered:

The 80w panel only generates 80w under the best conditions... full sun, no polution, shining directly (perpendicularly) on a clean collector. When the angle is less than 90 degrees you will get substantially less energy. Your day will be shorter in the winter and the angle worse. So, let's start with your 56.4w. (You should chart that throughout your day to see what you can really get.)

If your product requires 120w, then your 100w inverter is too small. It will shut down, blow fuses, or destroy itself.

Watts are simply Volts * Amps. (We'll ignore power factor and impedances for this discussion.)

So, if your device uses 120watts, that would be (120w/120v=) 1Amp in most people's house. But with your inverter, that would be (120w/12v) 10amps from a batter. And the inverter has some internal in-efficiencies.. maybe 80-90% efficient. So add another amp or 2, so that's 12Amps whenever the device is operated. (Make sure you turn off the inverter when not used.. it always draws power when on.)

And your battery isn't like a piggy bank. You don't get out everything you put into it. Batteries are not very efficient. Their efficiency changes depending on how long they have to hold the charge, how fast they are discharged, temperature, and where you are in the charge and discharge curves. It is very complex.

Toni Said:

80 watt solar panel ? what dose that mean?

We Answered:

Quick lesson. A watt measures power. You don't want technical, so let's just say that this is an instantaneous type of thing. A kilowatt is just a fancy way of saying 1000 watts. A kilowatt-hour is a measure of energy. This is simply power multiplied by the amount of time the power is "applied". So, if you had 1000 watts, and you "applied" it for 1 hour of time, you would have 1 kilowatt-hour of energy. (man, this is kinda hard to do without getting too technical!)

Back to your panel. 80 watts means that, as long as your panel is facing directly into the sun, it will produce 80 watts of power at any given instant in time. This is enough to run a 60 watt light bulb plus a little left over. But don't try to run a 60 watt light bulb on your solar panel because 60 watt bulbs are designed to run on 120 volt AC current, and your solar panel is likely a 12 volt DC panel. (Do you want me to explain volts, AC and DC? I didn't think so.)

Your solar panel will not work at night, and will not be able to do much laundry for you. But if you connect it to a charge controller, and a few more miscellaneous things, it would make one heck of a good battery charger.

If you want me to explain volts, AC, and DC to you, or you want help finding a good use for your 80-watt solar panel, contact me at wholesunsolar@yahoo.com.