Will this work?

easytim

I want to power 60 watts worth of LED lighting each night for 10 hours.
It will only be 10 hours during the winter months. In the summer it will be 6 hours
at 60 watts per hour max. All the lights will be using 12vdc No invertor will be used http://webpages.charter.net/easytims/LED_project.htm


One Controller
Model # AEE20.1120 - Type: Morningstar ProStar 15 - Amps: 15 - Volts 12 or 24

Two 130 watt panels 12vdc solar panels
Max voltage 19.8 voltage
Max current 6.55 amps each

Two 6 volt batteries in series, the heavy usage high AH type. I'm not sure which ones to use. I think they are sold as a golf cart battery and they sell at Sams.

I will be using 60 watts for 10 hours max, for a total of 600watts usage everyday (All led lighting only)

I live in St.Louis, Missouri

Can I make this comination work in my area?

BB.

Re: Will this work?

Numbers, location, clear questions... Just what the engineer in my likes! :roll:

Using the PV Watts program, 1 kW of solar panels (smallest number the program will give), use 0.52 derating factor assuming 120 VAC inverter (solar panel to 120 VAC output end to end efficiency), St.Louis MO (fixed array pointing at latitude):

[FONT=Fixedsys]Results

Month
Solar Radiation (kWh/m2/day)
AC Energy (kWh)
Energy Value ($ [/FONT][FONT=Fixedsys][SIZE=3]at 7.0 ¢/kWh[/SIZE][/FONT][FONT=Fixedsys])

1      3.60          59        4.13   
2      4.22          61        4.27   
3      5.09          78        5.46   
4      5.40          77        5.39   
5      5.67          80        5.60   
6      5.83          78        5.46   
7      5.86          80        5.60   
8      5.50          75        5.25   
9      5.33          73        5.11   
10     4.83          72        5.04   
11     3.53          52        3.64   
12     3.02          48        3.36   
=====================================
Year   4.83         835      $58.45    [/FONT]

The above is for 1kW of panels. Mutilply by 0.260 kWatts of your panels (I load this into Excel sometimes):

Same thing--just *0.26 for last two columns (260 watt of panels)
[FONT=Fixedsys]Month
Solar Radiation (kWh/m2/day)
AC Energy (kWh)
Energy Value ($ [/FONT][FONT=Fixedsys][SIZE=3]at 7.0 ¢/kWh[/SIZE][/FONT][FONT=Fixedsys])

[/FONT][FONT=Fixedsys]1    3.6     15.3    1.1
2    4.22    15.9    1.1
3    5.09    20.3    1.4
4    5.4     20.0    1.4
5    5.67    20.8    1.5
6    5.83    20.3    1.4
7    5.86    20.8    1.5
8    5.5     19.5    1.4
9    5.33    19.0    1.3
10   4.83    18.7    1.3
11   3.53    13.5    0.9
12   3.02    12.5    0.9
================================
Year 4.83    217.1  $15.2[/FONT]

So, the third column is between 12.5 and 20 kWhrs per month (seasonal range).

Or, 417 to 667 Watt*Hours per day...

So, in the deep of winter, you will be down 200 Watt*Hours per day and need to, cut down on power usage, use a back up genset every few days, or add 50% more solar panels for winter production (weather plays a large part--some winters you may be OK, others, you may need the genset a lot).

Battery Sizing... Assuming 3 day rule * 50% maximum discharge equals 6x daily load (12 volt system):

600 Watts*Hours * 6 / 12 volt battery bank = 300 Amp*Hours of 12 volt battery

Or, two 6 volt 300 amp*hour batteries (or combination there of).

I noticed I did the calculation with derating = 0.52%... If you are not using an Inverter, then the derating =0.61 would be closer to your setup (18% more power than I first predicted)--gives you on 260 Watts of solar panel:

[FONT=Fixedsys]
1    3.6     18.0    1.3
2    4.22    18.7    1.3
3    5.09    23.9    1.7
4    5.4     23.6    1.6
5    5.67    24.5    1.7
6    5.83    23.9    1.7
7    5.86    24.5    1.7
8    5.5     22.9    1.6
9    5.33    22.3    1.6
10   4.83    22.0    1.5
11   3.53    15.9    1.1
12   3.02    14.7    1.0
===========================
Year 4.83    255.4 $17.9[/FONT]

14.7-23+ kWhrs per month /30 days per month = 490-767 Watt*Hours per day... A bit better.

-Bill

BB.

Re: Will this work?

Forgot to add battery sizing... 3 days no sun, 50% maximum discharge, or 6x daily load:

600 Watt*Hours * 6 / 12 volts = 300 Amp*Hours at 12 volts

For example, 4x 6 volt 150 Amp Hour batteries (two in series for 12 volts, two strings in parallel for 300 Amp*Hours total capacity).

You can certainly use 2 batteries -- but that would limit you to about 1-2 days of "no sun"... And having to make up with a genset, utility power, or using less power.

-Bill

niel

Re: Will this work?

i just went through the calculations and used his current x 12v to get the wattage and multiplied that by 3.1 hours for winter solstice mounted at the angle of latitude.
http://rredc.nrel.gov/solar/pubs/redbook/PDFs/MO.PDF
it showed it to be 113w short and does not account for charge losses, efficiencies, and cloudy days. bb and i concur you need more to fulfill 10hrs worth of those leds a day or conserve power by cutting back on either the time and/or number of leds.