15KW bat system I have an idea criticism? comments?

[powerplay]

Avg. Usage:
2440 kWh/month or 29,280 KWH/year
System Size:
15.09 kW DC/ 11.04KW AC
pv area:
Up to 1900 sq ft

ok, i plan to put together a battery bank for a stand alone system with the above usage data.
I plan on a dedicated battery station with 4 slide out racks containing 12 2V800AH batteries. these are connected to an inverter panel for a house .
supporting these are 20 200W solar panels divided between two stand alone tracker assemblies. These are connected through solar combiners and charge controllers. Complimenting this is a propane/lp gas converted gen set connected to the charge controller and inverter.

I have done some of the math and i think it would work for 3 days without sun.
What do you think?

[Mike90250]

I'll assume you are configuring a 48V battery system for something this large.

You need to caculate your expected monthly harvest for your area:
http://rredc.nrel.gov/solar/calculat...ATTS/version2/ Has a listing of the cities, you insert your array size, and angle. and it tells your your apx harvest. You can also figure if you are collecting enough in the winter months, or if you have to run your generator. You may have to have adjustable racks for winter/sumer alignment.

Batteries - do you need batteries ? Between inverter and charger and battery losses, you only recover about 55% of your original harvest. Unless you are off-grid, or your area experiences yearly outages over 4 days long, a small, variable throttle inverter generator and 10gl of fuel is your best bet. Off grid solar is pretty expensive, with battery replacements every 7-10 yesars. A grid tie system will let you trim your electric bills.

[powerplay]

thanks for the info

I had figured that into my calculations, the area is along the equator with no winter and average daily sun (maximized with trackers) of 7-8 hours. Batteries are to be sourced from the manufacturers in china but what are the differences between a 24V system and a 48V system in laymens terms
Thanks! EAW

[Mike90250]

what are the differences between a 24V system and a 48V system in laymens terms

A 48V system is twice the voltage, and half the current (amps)

Say you have a 3,000w load on your inverter.
At 24V that's 125 Amps but
at 48V that's 62.5 Amps You can use thinner wire, which is easier to work with.

Instead of 2 parallel banks of batteries (problems sharing loads properly). you can use a single string of batteries, with no load sharing problems.

Less current density at each battery terminal, means less loss at each contact.