80w Panels

[underground renagade]

I intend to build an underground house in a remote area. Need to know what could be powered off of 1 80w solar panel.How many batteries can 1 panel charge? Is there a way to have computer access in a remote area?

[sh123469]

Assuming a 10 hour per day well sunlit panel, full output, you would only get 800 watt-hours per day.  Now to be more realistic, 6 hrs. of charge, 80% output, 64w X 6hrs is 384 watt-hours.  

Not much power there.  You could run two 12v 11 watt CF lights for 17 hrs per day.  This would consume the whole day's production and leave no room for charging batteries.

An inverter will also consume some power if you use one.  How much it consumes will depend on the inverter.

I think I remember that batteries lose about 20% of the power input for charging.

If you charge all day and use no power, that puts you at just over 300 watt-hours per day charge into the batteries.  That's 25 amp-hours at 12 volts. This doesn't take into account any wiring losses either.

Remote internet access is available by satellite.  I think it is about $60 to $70 per month.  It would require more power than you would get from this panel per day to operate it.  Check out Starband, Earthlink satellite, AOL is also available by satellite. The buy-in is sort of high.  Around $500, if I remember right, for the equipment.

Hope this helps.  If I said anything wrong, someone please jump in and let me know.

Steve

[ghurd]

I do the math a little different.

80. w PV output is about 4.7a peak. Maybe 4.5 hours (solar insolation) per day (varies greatly on where it is).
    
21. amp-hours per day, minus 10% losses = 19ah/day.  19X13V=247 watt hours.
    
    

A Watt-hour is watts used x hours used.  So 247w draw for 1 hour uses the average days charge. Or 1 watt for 247 hours. Or 123.5 watts for 2 hours. Or 61.75w for 4 hours.

That's still not much related to computers or TVs.

G-

[Ungrounded Lightning Rod]

Assuming a 10 hour per day well sunlit panel, full output, you would only get 800 watt-hours per day.

Don't assume that.  If you do, you're assuming that the sun goes straight from sunrise to noon position, hangs there for 10 hours, then falls down and disappears behind the horizon.

The real sun (appears to) swing across the sky, illuminating the panel through varying thicknesses of atmosphere and at varying angles (with a cosine-of-the-angle factor due to the oblique illumination.)

This is taken into account (along with other factors) in the "solar hours" value you can get from a number of government-produced survey maps.  The "solar hour" rating is the equivalent to the number of hours of noonday sun you get (on the average) on an unobstructed panel with a fix orientation, pointing due south and tilted at an angle from the horizontal that is equal to your latitude.

Solar hours numbers vary a bit depending on latitude, climate, nearby mountains, etc.  Typical values for temperate latitudes are 4.5 to 5.5 and also vary with season.

(Another poster has already posted calcluations based on this.)

[TomW]

ur;

Well. My experience shows that my 300 watt solar array only puts out 240 watts absolute maximum and more often about 18 amps into 12 volt batteries [around 216 vwatts].

Your 80 watt panels will likely only put out 64 watts or about 80% of sales droid blather.

I also can tell you from experience that a panel perpendicular to the sun will put out full power regardless of the season or time of day if the  skies are clear.

Just real world experience unhindered by theory.

Cheers.

TomW

[Opera House]

I have a total of 150W at my camp that I installed this year.  On two seperate two week vacations, I was barely able to get 2A charging most days.  Th slightest wisp of a cloud will drop your power to about nothing.  For what I wanted to do (run a very small RV fridge) it was a total waste of money.

[windstuffnow]

  Originally when I was looking into purchasing solar panels I found that they charge you for the watts the panel "could" make, not necessarily what they will make.  First off they rate the watts at 16.5 volts ( sometimes higher ) at the maximum amps.  This will never happen while charging a battery bank.  I don't know anyone that charges their batteries to 16.5 volts on a 12v system.  The best output you would see is 14.6 volts or 15.5 when your equalizing ( using lead acid batteries )and not very often should you do this.  

  When its all said and done, you'll calculate your needs and end up purchasing 2 times that in solar panels to meet the load and keep your batteries charged.

  Unfortunately, you still have to pay for the rip-off watts that the marketing media add in to make the panels sound impressive.

  Sorry about the small rant, I simply feel there should be truth when their selling a product...

Have fun

Windstuff Ed

   

[ghurd]

I believe my numbers will work out OK.

• 80w / 17v = 4.7 amps (X 13V = 61.1 watts)
  
• 300 / 17 = 17.6 amps (X 13V = 228 watts) A little less than TomW figured.
  
  

Solar Insolation is the average 'Quantity of Noon Sun' that falls on an area.

The standardised watt rating is needed to compare PVs.  The UL listing requires it.

The rip-off watts are needed. Otherwise, if the humidity was extremely high, if the sun is at 45', if it at all overcast, etc. there would be no charging at all.

All companies now rate PVs the same.

Don't buy something not UL or CE Approved (there is a price to pay in my experience).

This is where the solar insolation comes in.

Wind Genny thinking would be like saying there is this 1000 watt machine.

Now.  Right now.  Is it making 764 watts? (same as 80w claimed/ 61w produced)

Will a 1000 watt wind genny make 8.76 mega-watt hours per year?  They would have to send me a check every month.

Same idea.

So.  Take the rated watts. Divide by 17.  Multiply by solar insolation hours (it changes with the seasons and assumes no blockages like trees or buildings).

That is what you can expect in amp-hours (at 12v if you have 12v PVs).

ie: 12v, 17w PV = 1 amp.  Solar Insolation = 5 hours, where it is. 1a x 5h = 5ah.  5ah x 13v = 65 watt-hours.

Most of the 'sun' hours happens between 10:30 and 2:00.  Don't put it where the sun is ever blocked at these times.

[ghurd]

Something is not right.  Sounds very wrong even.

Mounting angle. Connections. Something.

You should be getting about 9 amps peak.

I always get over 2.5 amps from a single 50w PV.  150w should peak at almost 9 amps.

G-

[TomW]

ghurd;

I neglected to mention and it may not be widely known I track my panels and they also adjust for elevation seasonally so I get good output compared to fixed panels. My daily tracking is run from a computer and based on time via crond under linux from a 486 laptop computer I do my data logging from. The computer runs anyway but even if this was all it did I feel it would easily add more than the power it uses from the increase in power it provides [about 24 ah a day].

Cheers.

TomW

[ghurd]

Hi Tom,

Tracking is great.  If the end user knows how to use it.

I do 99% Amish solar.  Everything has to be bolted down, self-regulating, and reverse polarity protected.  I ball-park it, then ad 20%.  So far, so good.

Not directed at U.R., but I hope he enjoys it.

"as soon as I make something idiot-proof, they invent a better idiot"

-almost a quote, but can't remember who...

Glen

[RC in FL]

One earth solar flux at ground level runs about 1000 watts per sq. meter.  This assume directionality flat facing at the sun.  Unless you live in L.A. or some place where is lot of smog or fog, it will be same for any season or latitude on earth.  At poles you have a little more loss because of refraction of atmoshere and extra atmosphere to go through.

To the 1000 watts/sq meter you have to factor in the solar cell efficency.  This ranges for 10% to 18% for most panels.  Multi-crystine(looks like particle board grain) are less efficient, single crystaline (same a semiconductor processing, pure consistance solid black appearence) wafer based solar cells are more efficient. I think the galium arsinic panels they replaced on Humble space teliscope come in at 24% efficiency but don't think many can afford that type of solar cell.

You can figure tracking loss due to sun movement across the sky by doing the trig math to figure effective area directly facing toward the sun.  For example, a panel of one square meter turned 45 degrees to sun will be equivalent to 0.707 square meter panel directly face pointed at sun.  You can decide if tracking mount is worth while.

To all this you add diode loss, wire loss, etc.  A blocking diode will drop up to 1 vdc so it hurts more if you are operating a 12 vdc panel system verses a 24 vdc or 48 vdc panel system.  Also the higher the array voltage the lower the output current for same power which reduces the IR losses of the wire and such.

Also, panels degrade output the hotter they run.  Mounting them on a black or dark roof with no air clearance between back of panel and roof can degrade your power gen'g capability by 10-15% due to panels running hotter then if they had 6-8 inches of air clearance between roof and panel.

[Opera House]

Nothing wrong but reality.  This system is in upstate NY.  On both trips I experienced a lot of cloudy weather.  According to the charts I should only expect 2-3 hours X max panel amps a day.  I can get a good 8A when the sun shines. I do have line losses that will be corrected when I build a max power point switcher and operate the panels in 24V > 12V.