How to install Solar Panal for 24 Fuel Pumps for 20hrs daily

Can you tell us more about the pump? For example, what is the average current?

We need Amps * Hours of use, how many days of use in bad weather (sizing of battery bank), and where the system will be installed (hours of sun per day), seasonal usage (lots of sun in summer, not so much in winter).

-Bill

The following is a "rules of thumb" (or "rules of thumbs") first pass at what, I think, you are asking about. Here is my work. Assuming 28,000 Watts peak load, and say (worst case) 750 Watts (Volts*Amp is >= Watts) * 24 pumps * 18 hours per day, 48 volt battery bank (unless you can get higher voltage inverters+chargers), and you want a minimum of 10% charging current to batteries (~13% maximum "typical cost effective" for solar charging). For Lead Acid Batteries, 2 days of storage (1-3 is typical) and 50% maximum discharge (for longer battery life). This will be for Enugu Nigeria.

First, the battery bank. Typical "off grid home" assumes charging during the day and discharging at night (and/or bad weather). For your installation, you will be using power both day/not daytime, and during bad weather. So, a typical 48 volt system would look like:

• 750 "Watts" * 24 pumps * 1/0.85 AC inverter eff * 18 hours per day = 324,000 Watt*Hours per day
• 324,000 WH per day * 1/0.85 inverter eff * 2 days * 1/0.50 max discharge * 1/48 volt battery bank = 31,764 AH @ 48 volt battery bank

Note: While I will continue the math/design--More than likely such a large system may do better (and safer) if divided up into multiple smaller systems--Worry about that in later posts once you have the "basic needs" designed.

Now, charging current. Nominally, the batteries need a 10%-13% charging current (lead acid deep cycle/industrial flooded cell). In your case, you also have loads on the system during the day--So, the solar array should supply both charging current and daytime loads. This may "over size" your solar array trying to give your batteries a "long life" (makes initial install more expensive vs longer battery life).

• 31,764 AH batter bank * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 243,386 array "nominal"
  
• 31,764 AH batter bank * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 316,402 array "cost effective maximum"
• 750 "Watt" load * 24 pumps * 1/0.77 panel+controller derating * 1/0.85 inverter eff = 27,502 Watt array added to above to support pumps running during daytime

Then there is sizing the array based on "hours of sun" per day. For a fixed array in Enugu:
http://solarelectricityhandbook.com/solar-irradiance.html

Enugu
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 84° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
6.30	6.00	5.45	5.04	4.89	4.55
Jul	Aug	Sep	Oct	Nov	Dec
4.10	3.78	4.00	4.61	5.51	6.14

Note, if you have different Winter vs Summer loading (say more loads in summer, then 99 degree from vertical, pointing north, may be a better fixed tilt).

• 324,000 Watt*Hours * 0.52 off grid system eff * 1/4.0 hours of sun per day (little backup genset support) = 155,769 Watt array minimum

If you use a full 2 axis tracking array:
http://pvwatts.nrel.gov/pvwatts.php

Month	Solar Radiation ( kWh / m2 / day )
January	6.32
February	6.48
March	6.66
April	6.28
May	5.92
June	5.55
July	5.36
August	5.46
September	5.69
October	5.96
November	6.21
December	6.02
Annual	5.99

Or if you go fixed array (80 degree from vertical, facing south):

Month	Solar Radiation ( kWh / m2 / day )
January	5.74
February	5.88
March	5.87
April	5.24
May	4.68
June	4.25
July	4.14
August	4.38
September	4.86
October	5.32
November	5.59
December	5.47
Annual	5.12

If you use July for this second calculator, the July increase is roughly 29% more power from 2 axis tracker vs fixed array--So that gives you a rough idea of how much sizing difference there would be--And you can look at the increased costs from mechanical tracking vs fixed array, and see is worth it.

For a fixed array, I would suggest that you look at minimum tilt of ~85 degrees from vertical so that panels are somewhat self cleaning (rain washes off dust).

So--That is where I would start. The above is probably over sized by, at least, 20-30% due to secondary issues. Typically and electric motor runs at a PV of ~70-80%, so that VA*0.7=Watts would reduce electrical loads. Also, during "typical" sunny days, you don't have the ~20% losses of cycling the batery bank (array is powering pumps while sun is ~9:00 to 15:00). But, we have not accounted for lighting, power for billing computer(s), possible fan/Air Conditioning, etc.

It would probably make sense to design+build a ~1,000 AH battery bank+10,000 Watt array and connect it to 2-4 pumps and see how the system works out--Then build it out once you have better information.

I would also look at alternative solutions (look for more efficient pump motors/controllers) and simply using solar to reduce genset fuel usage (i.e., solar to support 60-80% of loads). Or even a "hybrid" generator system. Genset to support "peak loading" and use inverter+battery bank to support off peak (possibly early morning/late evening loads)--Genset runs during peak time+recharges battery bank--And add solar panels as needed to reduce genset run time overall.

Your thoughts?

-Bill