Making 1180 Watt Solar Power System

Re: Making 1180 Watt Solar Power System

Need to know, approximately in what part of the world you are located (near major city)...

Adding up your power (I am guessing that some of the numbers are wrong--2x120=240 watts for the TV looks fine, but 5x300=1,500 watt for lights look high):

2x120x4=960 watthours per day
5x350x4=7,000 wh/d
5x300x4=6,000 wh/d
3x500x11=16,500 wh/d
2x1500 (per day?)=3,000 wh/d
=======================
33,460 wh/d or 33.5 kWhrs per day... 1,000 kWhrs per month...

My (near SF CA) grid tied system, not optimally aligned to the sun (little bit of morning evening shading--call it 5-6 hours of good sun per day) 3,500 watts Peak generates about 15 kWhrs per day from April through September (including cloudy weather, etc.).

You panels add up to:

45*18 + 10*37 = 1.18 kW peak...

Even if you were able to double my systems ability to gather sun (very possible)--you probably are only 1/3 of the way to powering "everything"...

Plus, once you add inverters and batteries--you are now down to:

~80% (lead acid battery charge efficiency) * 80% Inverter eff = ~64% efficiency overall...

Meaning that you need to increase you solar panels by 1/64% by 1.56x more to make up for your losses.

If you live in an area that allows grid tied solar (with reasonable terms), going Grid Tie costs less and is, overall, more efficient that going through the battery route.

If you need batteries (no grid tie or want back up power), then you have to live with the losses.

In the end, conservation of energy is always cheaper and recommended before trying to throw solar at the problem (change lites to CPFL and/or florescent, energy efficient appliances, using laptop computers instead of desktop computers, turn off everything using power strips to save standby power--cell phone chargers, microwave ovens, TVs, satellite boxes, etc...

It is always difficult to give suggestions to somebody unknown living in an unknown state/country, with unknown weather and energy requirements. But I found it nice to have a goal for energy savings. It does not have to ever be achieved--but it helps to keep one focused on a goal.

For example, I used 100 kWhrs per month as my goal. That is a 24 hour per day load of 139 watts. All of a sudden, the 8 watts that my washer and drier spend on standby ended up almost doubling their total energy use over a one year period.

That laptop computer that takes about 20-30 watts all of a sudden looks much better compared with that desktop system at 120-500 watts running completely blew my entire power budget.

I was (a family of four) was never able to hit 100 kWhrs per month--but I did get down to a few months of 175-185 kWhr a month during the summer (this is in a US house hold with central heat, washer, drier, 2 computers, network, UPS, several TVs, digital receiver, large fridge, two laser printers, kids who don't turn off lights, etc.).

You did not give the actual "ampacity" of your batteries--but a good start is to size the system to store 3 days of energy down to a depth of charge of 50%... So:

33,500 Whrs * 3 Days * 1/50% battery discharge / 12 vdc battery bank = 16,750 amp*hours (at 12 volts)

If you have a 24 volt battery system (higher voltage is recommended--48 vdc charger/inverter would work well too), that would be 16,750 / 24 = 8,375 A*H at 24 vdc

Those are not small battery banks... In general, it is not that difficult to build a system that will power, for example, a 1 kW microwave for 10 minutes per day--but building something that will supply (33.5kWhr/day / 24hours=)1.4 kW 24 hours per day for 3 days is something else.

Did any of this help?

-Bill

Re: Making 1180 Watt Solar Power System

Forgot to add... The Kill-A-Watt meter is probably the single cheapest and best meter for measuring power usage on your appliances (only works on 120VAC at 60 Hz--US style 3-prong plug).

http://store.solar-electric.com/kiacpomome.html

Looking at appliance name plates is not the best for estimating true day to day power usage.

-Bill