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Author Topic: Solar Examples  (Read 3786 times)


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Solar Examples
« on: November 09, 2010, 05:36:44 PM »
Solar Example Only

Appliances  Watt Hours/ Day  Hours/ Day  Watts/ Day
Refrigerator (with ice maker)  92  x 24  = 2208 
Bathroom Lights = 5 x 20w  100  x  3  =  300 
Bedroom Lights = 4 x 20w  80  x  4  =  320 
Computer System  200  x 4  =  800 
Ceiling Fans = 10 x 70w  700  x  12  =  8400 
Kitchen Lighting = 2 x 20w  40  x  6  =  240 
Living Room Lights = 5 x 20w  100  x  6  =  600 
Misc Kitchen Appliances  1200  x  0.25  =  300 
Radio/Stereo  30  x  1  =  30 
Refrigerator Ice Maker  50  x  1  =  50 
TV = 2 x 150w  300  x  4  =  1200 
Water Pressure Pump  100  x  1  =  100 
Total watt hours per day  =  14,578 
Multiply by 1.20 for Inverter Loss  =  17,494 

Calculations For Number of Solar Panels Needed 
Total Watts Used per Day  17,494 
Number of Sunlight Hours for Charging  5 
# of Watts a 165w Solar Panel Will Produce in 5 Hours  825 
Divide 825w into 14,844w This = # of Panels Needed  21.20 
Round Up to Even Number of Solar Panels  22 
Cost Estimate for 165w Solar Panel  $595.00 
Number of Solar Panels x $595.00  $13,090 

Calculations For Battery Sizing 
Watts / Volts = Total Amps Used per Day (14,578w / 12v)  1458 
184 Amp Battery  184 
Only Discharge Battery to Half Life  92 
Total Amps / Battery Amps Available (1237a / 92a)  15.85 
(Round up to Even Number) Number of Batteries Needed  16 
Cost Estimate of 184 Amp Batteries  $179.00 
Total Cost of Batteries  $2864.00 

Pricing Calculations 
22 Solar Panels 165w  $13,090.00 
14 - 184 Amp Batteries  $2864.00 
4048 Power Panel Inverter System  $4000.00 
Cables and Mounts  $1000.00 
California Tax 7.75%  $1624.00 
Total Cost Estimate of Solar System  $21,578.00 

a free-standing solar system is not solar powered but battery powered.

Power is transfered from 12 volt batteries to an inverter that transforms it into house current (120v).

As the power is taken from the batteries there must be a system in place to recharge the depleted batteries.

This is where the solar panels come in. There has to be enough energy provided to produce enough power to replace the power in the batteries the inverter took for the house current.

How to calculate number of solar panels needed:

1. How many watts of power you will use each day? This is done by listing each appliance, the watts it uses per hour, and the number of hours it will be on. Ours is 17,494 for the 5 casitas.

2. When you find this number, you now know how many watts the solar panels have to supply the batteries during sunlight hours. Baja is rated as an average of 5 hours solar power available each day. This could be higher during certain times of year.

3. Now you decide what size solar panel you want to purchase. We will need several panels so we choose a larger size. (165 watts).

4. In 5 hours these 165 watt solar panels will produce 825 watts.

5. To get the total number of solar panels need for Playa Frambes you divide Total Watts (17,494w) by the total amount of watts the solar panels will produce during daylight hours (825w). Playa Frambes needs 22 (165w) solar panels.

How to calculate number of batteries needed:

1. Batteries are rated in Amp/Hours. We choose 12 volt 184 Amp/Hour deep cell batteries available for $179.00 each because they are available in Baja later if we have a battery failure.

2. Since we know how many watts Playa Frambes will use per day, (17,494w) it is a simple conversion to convert watts to amps. (watts divided by Volts = Amps). Total Amps need per day will be 1458.

3. Batteries should only be discharged to half-power. This meand our 184 amp batteries are actually only 92 amp usable.

4. Divide total necessary amps (1458) by useable battery amps (92) to get number of batteries needed for one days storage. This number is 15.85 but there is no .85 battery so you ned to round up. (16 batteries needed


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