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bobosun

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Posts: 3
Reply with quote  #1 
I wish to use the electricity generated by 4 /300 watt panels.  I do not wish to store any electric but use it as it is produced for heat in winter and air conditioning in summer.  I wish this to be off grid.  Simple is better.  Safe is good also.  Any useful info will be appreciated.  Be as specific as possible as I already have a concept of the process.  Thanks bobosun  

stmbtwle

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Reply with quote  #2 
Off grid, I think you're asking for the impossible.  While 1200w (rated) of solar panels in theory would run a small heater or air conditioner, in reality I'm not so sure.  

Strip (resistance) heat would be easy, though not terribly efficient, just put together enough strips to use all the energy.   Air conditioning or a heat pump is another story.  It requires AC current, which means an inverter.  The inverter would probably drop out whenever a cloud went over, and your air conditioner with it.  I'm not going to guess how long this (expensive) equipment will last under those conditions. You're going to need SOME kind of storage to stabilize the power, and that means batteries.  Batteries mean a charge controller.  So much for "simple". Depending on conditions you could probably run a small (5000btu) window unit.



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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
bobosun

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Reply with quote  #3 
Thank you for taking some of your valuable time to reply.  I was a bit lean on some of my knowledge about what I have done so far.  I have a 7140 ground mount pv array grid tied with microinverters.  It is maxed out electrically for the load produced.   Because of the way the mounts were installed I was able to move the panels to one side and add an additional column of panels. (4/300 watt panels).   After looking at a number of youtube videos I realized I would need to convert my DC to AC in order for it to be useful. I then looked at the solar for beginners schematic's.  1. a way to combine the 4 panels to one positive and one negative terminal (combiner box). 2. a charge controller. 
3. battery.  4. inverter.  I realize the pv I get from these panels will not produce much heat or AC but where it will be used will make a difference.  What I need to understand is exactly what I need to accomplish this at minimum standards safely.  I don't expect free.  I have viewed companies that are willing to sell me a $4000 system which of course makes this nonsensical.
I am big on theory not so much on specifics.  If you take the time to read this I am grateful.   
bobosun
stmbtwle

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Reply with quote  #4 
What exactly are you trying to accomplish? Be specific.

And fill out your profile! Where you are located makes a difference.

Vague questions will get vague answers.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
bobosun

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Reply with quote  #5 
  Thank you for your time.  I live in southeastern NY.  According to a PVWatts calculator 1 kw of collector will produce about 1340 kwhr/year.   Simply put, I wish to use the electricity produced when the sun is shining to produce heat in a resistant electric heater.  I do not want to store energy for use when the sun does not shine.  I know that this is a poor use of solar energy.   The collectors are about 60 feet from the point of use.  The panels are Solar world sunmodule plus sw300:  open circuit voltage  40.1v
                                   mpp voltage             31.6
                                  short circuit current   10.23a
                                  mpp amps               9.57 
I wish to combine these panels in parallel  raising the amps to approximately 41 short circuit amps.  Connect to a charge controller of sufficient size to handle the load.  connect to a battery of sufficient capacity to handle the load  then to an inverter of sufficient size to be used 60 -70 feet away.  Because the electric produced will be use for resistance heat a sine wave inverter is unnecessary.
The panels are grounded to the racking which are grounded to two bars six feet into the ground with #6 bare copper wire. 
  For 40 years I have supplemented my home heating with a wood stove.  I have access to enough wood but I am choosing to use less wood because age.  Think of the PV project as a hobby rather than an efficient way to heat my house.  
bobosun

































 
stmbtwle

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Reply with quote  #6 
For resistance heat as you describe you shouldn't need an inverter, charge controller or batteries (your water heater IS your energy storage).  Your three panels in SERIES will give you roughly 100-120 volts; you can get 1500watt, 120 volt heating elements for water heaters for a few dollars at Big Box.  The "match" may not be perfect but it should work and it's a good place to start.  That and the existing thermostat should be all you need.  An on/off switch would be a good option.

If you have a larger, two-element water heater, you might leave the top element on 240v line voltage and convert only the bottom element to 120vdc.  Each element will need it's own thermostat. Label the two systems accordingly.  

DO NOT ATTEMPT to connect the 240vac system and the 120vdc system together.  The results will NOT be nice.

If you still want to run an AC it gets considerably more complicated, as already discussed. You would need the charge controller, probably several batteries, and inverter. I'n not sure it's worth it.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
colinmcc

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Posts: 176
Reply with quote  #7 
As stmbtwle says, your best bang for your buck is to wire the 3 panels in series and just connect them to any resistance heater element. A water heater as suggested is the obvious all year round use of the generated power, but the thermostat will cut the power to the water heating element when the heater set point is reached and your panels output will be no longer used. A shame!

If you get a thermostat that is normally used for the 'top' element of a dual heater tank, then when it reaches it's set heat the second set of terminals will go 'live' and you could, at least in the winter, hook those terminals to a 1500w baseboard heater, and get hot air once your water is satisfied.  my local second hand/ charity store often has old baseboard heaters for just a few bucks, you wouldn't need to spend much for a proof of concept.
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