solar panel for 305 gallon aquaponic hoop house

5thgradeotg

I am a 5th grade teacher and am teaching off the grid sustainability, what are the specific necessities (size of solar panel, voltage/watts, inverter, battery etc) to run the water pump 24 hours a day?

vtmaps

Sort of like asking "how much electricity does it take to run a light bulb?"  It depends on the lightbulb.

Welcome to the forum,

The answer to your question depends on the pump.   First thing to figure out is how many watts does the pump draw, and how many hours a day is it pumping?  Multiply those two numbers and you get watthours.  Once we have a daily watthour total, the system design is straight forward.

Generally, pumps that draw more watts are able to move more gallons per minute and/or provide the water at higher pressure.

--vtMaps

westbranch

Phew!  when I read the title alone I thought you wanted to use the PV to create the heat for the house...  Possible but not likely... How WILL you be generating the heat for that system?

BB.

As the folks above have said, it really is important to know your needs and get the most efficient pump(s) you can.

This website has a lot of detail information as he spent a few years installing/upgrading/fixing his system (relatively small system):

http://www.arttec.net/Solar/BarnHeat.html

And this one is a bit more low tech home made heating system. (but system is installed in snow belt)

And for details, there are some DC pumps out there. Some are "brushless" (electronic commutation) and others are "brushed":

http://www.thesolar.biz/dc_hot_water_circulating_pumps.htm

And, the question of how much pumping you need. The above pumps only will pump 10-20 inches of water, and need only 10-20 watts or so of power. If you are using solar panels to heat, then you may get away with a solar panel directly powering a water pump (no battery--Least maintenance, least costs).

However, if you need a 24x7 water pump. And say it is a 100 Watt pump (normal larger hydronic heating system), for example, this is how I would suggest you would do the calculations for a full AC / Battery Based / Off Grid system. Your needs will probably be different, but it gives you an idea about the math.

Example system:
24 hour per day, 2 days of backup power (no sun), 50% maximum battery discharge, flooded cell battery, Long Beach California, 100 Watt average AC power.

First size the battery bank:

• 100 Watts * 1/24 volt battery bank * 24 hours per day * 1/0.85 AC Inverter eff * 2 days no sun * 1/0.50 max battery discharge = 471 AH battery bank (about 4x 6 volt @ 220 AH golf cart batteries)

Next, size the solar array... Two calculations. First is based on the charging rate of the battery bank. Nominally 5% to 13% rate of charge (20 Hour battery discharge rate) is recommended. For full time off grid, generally 10% or more rate of charge:

• 471 AH * 29 volts charging * 1/0.77 solar panel+charge controller derating * 0.05 rate of charge = 887 Watt array minimum (weekend/seasonal system)
  
• 471 AH * 29 volts charging * 1/0.77 solar panel+charge controller derating * 0.10 rate of charge =1,774 Watt array nominal (full time off grid)
  
• 471 AH * 29 volts charging * 1/0.77 solar panel+charge controller derating * 0.13 rate of charge =2,306 Watt array "cost effective" maximum array
  

And then there is sizing the array based on the amount of sun you get. Say you are near Long Beach Ca, and want a fixed array, using a solar calculator:

http://solarelectricityhandbook.com/solar-irradiance.html

Santa Ana
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 56° angle from Vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.54	4.95	5.84	6.43	6.15	6.10
Jul	Aug	Sep	Oct	Nov	Dec
6.21	6.30	6.05	5.43	5.01	4.50

There is always the question of how much sun in the winter---Southern California is not too bad... Other places may be less than 2 hours of sun per day in the winter. For this setup, assume that you will use a backup genset during multi-day stormy weather. And in this case use 4.50 Hours of sun (long term December Average):

• 100 Watts * 24 hours per day * 1/0.52 off grid system efficiency * 1/4.50 hours of sun = 1,026 Watt array minimum

So, somewhere around 1,026 Watt to 1,774 Watt solar array minimum (in general, batteries are expensive, solar arrays are cheap, pick larger solar array to better charge the battery bank).

Your questions.

-Bill