From: ham789@netzero.net   
      
   On 5/17/2015 9:55 AM, New Guy wrote:   
   > On Sat, 16 May 2015 13:32:01 -0700, mike wrote:   
   >   
   >> On 5/16/2015 9:21 AM, New Guy wrote:   
   >>>     I have a HF 45 W solar setup charging 3 35AH batteries and a   
   >>>     2000/4000   
   >>> W inverter. I was hoping to power an air compressor which is rated for   
   >>> 14 amps. As it is now it won't. How can I beef up my setup to do so.? I   
   >>> am new to PV and have trouble understanding electric talk. What do I   
   >>> need to add ? And can someone point me to a link which might help me to   
   >>> understand a little about electricals associated with PV.   
   >>>   
   >>>    Newbie   
   >>>   
   >> I missed the part where you disclosed where you live and how long per   
   >> day you need to run the air compressor.   
   >   
   >    Yes.. I failed to express a lot. My location is Raleigh NC area ( or   
   >   close enough ). And I don't use the compressor much at all. Mainly   
   >   inflating tires, blowing off grass and debris from lawn mower. I will   
   >   on occaision use it for drilling, circular and reciprocating sawing   
   >   but nothing extensive. And of course I run the two dc lights that came   
   >   with it.   
   >   
   >    When I do run the compressor now I have two extension chords running   
   >   150' to the barn. I admit that I somehow was under the impression that   
   >   mystical PV was magic as well. You certainly have opened my eyes to   
   >   quite a bit of reality. And to think I also have been tinkering with   
   >   the idea of building a windmill to help suppliment when sun has nothing   
   >   to offer.   
      
   That's another bucket of worms.   
   I've helped people build radio repeaters on mountain tops.   
   Solar is pretty straightforward.  Just program up a Maximum Power Point   
   Charge controller and you're done.   
   Built a solar tracker system, using the same software techniques, but   
   the mechanics were deemed too unreliable for use on a mountain top that's   
   inaccessible most of the year.   
      
   Wind has a lot more issues.  They replace a wind generator about every   
   other year.  Doesn't take much ice to unbalance it to the point that it   
   shakes itself to death.  There's some evidence that it's an attractive   
   device for target practice.   
      
   With solar, when the batteries are fully charged, you just disconnect   
   the solar cells.  Can't do that with wind.  It will spin up until it   
   flies apart.  The generator has a speed limiter, but it's not very   
   accurate and fights with the charge controller.  Ended up disabling it   
   and using a 300W resistor to dump the excess wind power.   
      
   Wind generators like constant wind from a constant direction.   
   If you have buildings or trees nearby, you can get swirling air   
   currents that are very hard on the bearings.   
      
   While the concept is simple, there are lots of little things that   
   can ruin your day.   
      
   Alternative energy is a great hobby.  Just do the math before   
   you spend the money.  You want to identify the roadblocks   
   before you spend 200% of the budget.   
      
   Might also be interesting to do the cost analysis on running an   
   air hose 300'.  If you have an accumulator tank at the destination   
   to handle the peak flow, you may not need a very large diameter hose.   
   Or maybe run a larger pipe for air with the electrical wire for   
   lighting run inside the hose.   
   >>   
   >> Go here:   
   >> file:///D:/netcd/netdvd64/current/hobby/solar/PVWATTS%20v.%201.htm and   
   >> put in your location.   
   >>   
   >> This program is obsolete and you can't change anything.  Just click thru   
   >> to the results and scale the numbers by 45/4000 to get numbers for your   
   >> 45W panel at your location.   
   >>   
   >> Yes, there's an upgraded site, but you'd have to figger out how to work   
   >> it and gain nothing.   
   >>   
   >> Notice the pitiful amount of energy you'll get, especially in winter.   
   >> Your batteries have to supply enough energy per day to run your air   
   >> compressor.  And you can't run 'em flat, so double it.   
   >>   
   >> Your panels have to produce enough energy to recharge the batteries   
   >> every day in winter months.  That gives you zero allowance for cloudy   
   >> days, so multiply the number by whatever makes you comfortable.   
   >>   
   >> Get the resultant numbers.   
   >> When you recover from the shock of the magnitude of the problem in size   
   >> and $$$,   
   >> Go buy a gas generator.  Or a long extension cord.   
   >>   
   >> The same calculations work for lighting.  If you really don't need the   
   >> air compressor much, you may be able to do a small amount of lighting   
   >> with your current setup.  Run the generator only for the compressor.   
   >> Or put a gas engine on the compressor.   
   >>   
   >> Solar makes a lot of sense when you have low requirements and absolutely   
   >> no way to get power any other way.   
   >>   
   >> Stated another way, solar is rarely cost effective.   
   >   
   >    Thank you for your valuable input ( ... output ? ). And thanks to the   
   >   other responses as well.   
   >   
      
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