Newbie question .. please answer if you can

Re: Newbie question .. please answer if you can

I guess you are in the Reno, Nevada area? And you want solar power...

First question is "how much power"... Simple way is in Watt*Hours or kWatt*Hours (same units as your home electric power meter).

For example:

2 hours * 800 watt heater = 1,600 watt*hours (1.6 kWhours)
8 hours * 60 watt laptop = 480 watt*hours
4 hours * 100 watt fan = 400 watt*hours
==========================================
2,480 watt*hours (2.48 kWhrs) guesstimate of load.

Now, you can either go grid tied or off-grid... Guessing that you want off grid battery power system...

The battery should be 2x the capacity that you want to run (a normal flooded cell storage battery should not be discharged by more than 50%).

So, for yours (assuming 24 VDC system)...

Batt Cap = 2,480wh/(0.50 cap * 24 vdc system) 207 amp hours @ 24 volts DC...

Roughly, that is about the size of 4 good sized car batteries. And it will run your loads as listed above... If you need more/less, adjust the formulas...

Now, you need to recharge the battery with solar panels... Your power needs have to be derated by solar panel / inverter/ battery inefficiencies... In this case, assume 80% / 85% / 80%):

Power = 2,480 WH / ( 0.8*0.85*0.8 )= 4,844 Watt*Hours

Looking up Reno in a solar isolation table (fixed collector tilted to noon summer or winter sun):

Best summer month = 7.7 Hours of Sun (July average)
worst winter month = 4.2 Hours of Sun (December average)

And assume that you want to do this every day (using average numbers)

4,844 W*H / 7.7 Hours = 630 watts of solar panels
4,844 W*H / 4.2 Hours = 1,153 watts of solar panels...

Pick a solar panel, battery, and inverter from here (sponsor of this site, good prices and good products)...

Solar panels are roughly $5/watt--$3,150 to $5,767 (summer/winter panels)

4x AGM deep cycle batteries $255 each--$1,020 (AGM are very good batteries, flooded cell may cost 1/2 that)...

Exeltech Pure Sine inverter 1,100 watt @ 24 VDC input = $612

MX-60 solar charge controller ~1,400 watt max @ 24 vdc = $498

~$5,000 to $8,000 to power your system as estimated for 1 night of battery use, and one day of solar charging...

If you want three days of no-sun, use 3x the number of batteries.

If the batteries are not around room temperature, but exposed to very cold weather, you will need to derate them and add more capacity.

If you only need to run on batteries for 1 day at a time, and can wait up to three days to recharge--then cut the number of panels by 1/3.

If you have to have power and need to ride through bad weather, you probably will need a generator and a battery charger or an inverter/charger unit.

If this is a full time use, solar is very nice--it generates power day in and day out all year long (weather permitting). If this is for a summer or 2 weeks out of the year type deal, a nice generator is hard to knock (price wise).

Generally, going solar would require you to do as much conservation as possible... For example, electric heat from solar PV panels is horrendously expensive. You can buy or build solar thermal panels at $0.50 per watt (vs $5 per watt for PV panels) and they would be 1/4 the area for similar wattage from solar PV panels.

The laptop--I just took a wild guess here--but I have seen numbers that range form 8 watt to 60+ watts depending on the "power" of the computer and what it is doing (back light on/off, heavy processing or just typing, used for 8 hours or on standby for 6 of the 8 hours, etc.).

I hope that this helps you narrow down your requirements... The chances that I have guessed even 1/2 way close to your needs are probably pretty remote.

Once you have firmer requirements, I am sure that everyone here can give you a much tighter system design recommendation.

-Bill

Re: Newbie question .. please answer if you can

Errr... ergo... 800 Watt*Hours = 2,730 BTU or...

800 Watts = 2,730 BTU/Hour...

Sorry... Just trying to keep the units correct.

-Bill