Making your numbers behave for Battery Bank Sizing

From HeatSpring PV Boot Camp and NABCEP Entry Level Exam Course

Q:

I am paying attention to the important stuff, but also like your great tip-bits, like “pointing to the Sun = location latitude + 23°” .

Sorry your battery sizing math depiction got away from me for a moment, (slide 104 minutes into assignment 2/7 PV system sizing) Your explanations were good to divide the CL after Wh x DOA / DOD, but the depiction show it in multiplication?

Agreed kWh or Wh is a better way to view the process than Ah.

Like your idea of using flywheel battery technology at the poles, too bad it’s outside of distributed generation. ;>)

A:

When I do a lot of calculations, I just pay attention to what my numbers should do and I make them behave.

When doing battery sizing, you are almost always taking the load energy and making that number larger by using factors for depth of discharge, days of autonomy, conversion losses and cold temperature correction factors.

I just take the number that corresponds to the energy load of a day and multiply that by numbers larger than one and divide by numbers less than one to make my load larger.

One thing to look out for though, is when you have a loss, like for conversion losses, turn that loss into a derating factor. Let's say that you lose 30% due to conversion, then you keep 70% and your derating factor is 0.7 and you would divide by 0.7 to make your number larger.

We can have distributed generation on the poles, soon it will be warm there due to climate change, which is not caused by humans, it is caused by polar bear karma for killing all those seals.

Thanks,

Sean White

PS: The reference to distributed generation on the poles refers to fly wheels losing energy due to Coriolis forces from the spinning of the earth, which would not happen at the poles, since the fly wheels would spin in the same plane as the earth.

From HeatSpring PV Boot Camp and NABCEP Entry Level Exam Course