My First Solar Project .. Please confirm if my calculation is correct.

[emdep3000]

This is my first go green project. Please help check to see if my calculation is good. Thank you.


SOLAR PROJECT

i) Equipments:
4 x 12 Watt porch lights will be on from Dusk to Dawn (or 12 hours/day) = 48Watts
2 x 0.2A Fountain Water Pump from Dawn to Dust (or 12 hours/day) = 2 x (0.2A x 120V) = 48Watts

ii) Watt-Hours:
For Porch Lights: (12Watt/light)
12W x 12H = 144Watt-Hours. Total of 4 lights = 4 x 144Watt-Hours = 576 Watt-Hours
For Water Pumps: (0.2Amp/pump)
24W x 12H = 288Watt-Hours. Total of 2 pumps = 2 x 288Watt-Hours = 576 Watt-Hours
Total of daily Watt-Hours:
576 + 576 = 1152 Watt-Hours

iii) Inverter:
1152 x 1.5 = 1728 Watt

iv) Sun in hours:
Average 5 hours a day of full bright sun.

v) Size of Solar Array:
1728 Watt-Hours / 5 hours = 346 Watt

vi) Size of Battery:
(Battery capacity = Daily Watt Hours x 2 days)
1152 Watt-Hours x 2 days = 2304 Watt-Hours
(Amp Hours = Watt Hours / Voltage) and (12Volts battery will be used)
battery capacity in Amp Hours = 2304wh / 12 volts = 192 Amp-Hours

vii) Charge Controller Size in Amps:
(Charge Controller Output Amps = Panel Wattage / Battery Voltage)
Charge Controller Size = 346W / 12V = 28.8Amp

[inetdog]

This is my first go green project. Please help check to see if my calculation is good.
vi) Size of Battery:
(Battery capacity = Daily Watt Hours x 2 days)
1152 Watt-Hours x 2 days = 2304 Watt-Hours
(Amp Hours = Watt Hours / Voltage) and (12Volts battery will be used)
battery capacity in Amp Hours = 2304wh / 12 volts = 192 Amp-Hours

Well, for a first step, off-grid systems are seldom green, although they are sometimes unavoidable and may also be fun or educational or both.

Second, you want to avoid drawing the batteries below 80% SOC daily if you want long life, so you need 1152 watt hours times 5 to satisfy that limit. That will also give you two and one-half bad charging days before reaching 50% SOC, the other rule of thumb limit.

Have you tried the excellent off-grid battery and system calculator on this forum?

[daz]

iv) Sun in hours:
Average 5 hours a day of full bright sun.

Is this sunlight hours...or solar insolation hours?
There is a major difference between daylight hours and solar insolation hours.

[Wy_White_Wolf]

Inverter is way to large. Actual load is 48W +48W = 96W so a 150 to 200W inverter should work. Using a way oversized inverter lowers the efficiency level of the system.

Batteries are way undersized as inetdog pointed out.

You have to plan for worst case which means using the lowest months insolation instead of yearly average. Using yearly average will put you in the dark during the winter months.

WWW

[Sunking]

1152 Watt-Hours

iii) Inverter:
1152 x 1.5 = 1728 Watt

Incorrect Inverter = 2 x load wattage all you need is a 200 watt inverter.

iv) Sun in hours:
Average 5 hours a day of full bright sun.


v) Size of Solar Array:
1728 Watt-Hours / 5 hours = 346 Watt

Incorrect you have used average Sun Hours. You must use worse case of winter month with shortest Sun Hour Days otherwise you go dark all winter. I do not know your location to go look so can only guess is around 3 hours so more likely to be around 500 watts

(Battery capacity = Daily Watt Hours x 2 days)
1152 Watt-Hours x 2 days = 2304 Watt-Hours
(Amp Hours = Watt Hours / Voltage) and (12Volts battery will be used)
battery capacity in Amp Hours = 2304wh / 12 volts = 192 Amp-Hours

Asking for big trouble here discharging to 50% each day. 1 cloudy day and you go dark for 2 days. In addition hitting the batteries will with such a large amount of current is going to cause damage, It will also significantly shorten battery life Minimum recommended is 5 days. 12 volts @ 480 AH

vii) Charge Controller Size in Amps:

(Charge Controller Output Amps = Panel Wattage / Battery Voltage)
Charge Controller Size = 346W / 12V = 28.8Amp

Patially correct if using a MPPT controller which is what you have designed for. However you got th epanel wattage incorrect so this is going to change and end up being 40 amps.

[emdep3000]

THANK YOU ... THANK YOU everyone for your help and effort to correct my calculation.

According to your point out, I've made changes and correction.

Below is my Version 2. Please help to check it again. Thank you.


SOLAR PROJECT VERSION 2

i) Equipments:
4 x 12 Watt porch lights will be on from Dusk to Dawn (or 12 hours/day) = 48Watts
2 x 0.2A Fountain Water Pump from Dawn to Dust (or 12 hours/day) = 2 x (0.2A x 120V) = 48Watts

ii) Watt-Hours:
For Porch Lights: (12Watt/light)
12W x 12H = 144Watt-Hours. Total of 4 lights = 4 x 144Watt-Hours = 576 Watt-Hours
For Water Pumps: (0.2Amp/pump)
24W x 12H = 288Watt-Hours. Total of 2 pumps = 2 x 288Watt-Hours = 576 Watt-Hours
Total of daily Watt-Hours: 576 + 576 = 1152 Watt-Hours

iii) Throw in a FUDGE factor: (losses in wiring, charge controller, battery charge efficiency, and inverter)
1128 Watt-Hours x 1.5 = 1728 Watt-Hours

iv) Inverter: (Total of Wattage x 2 )
( 48 + 48 ) x 2 = 200 Watt

v) Sun in hours: (I'm San Jose, California)
I will take 4hr/day for the shortest winter day.

vi) Size of Solar Array:
1728 Watt-Hours / 4 hours = 432 Watt --> round up to = 500 Watt

vii) Size of Battery: (Battery capacity = Daily Watt Hours x 5 days)
1728 Watt-Hours x 5 days = 8640 Watt-Hours
(Amp Hours = Watt Hours / Voltage) and (12Volts battery will be used)
battery capacity in Amp Hours = 5760 wh / 12 volts = 720 Amp-Hours

viii) Charge Controller Size in Amps:
(Charge Controller Output Amps = Panel Wattage / Battery Voltage)
Charge Controller Size = 500W / 12V = 40 Amp

[Naptown]

All to produce about $.17 a day of electricity.
The charge controller alone will be over $400

[Sunking]

Total of daily Watt-Hours: 576 + 576 = 1152 Watt-Hours

vii) Size of Battery: (Battery capacity = Daily Watt Hours x 5 days)
1728 Watt-Hours x 5 days = 8640 Watt-Hours
(Amp Hours = Watt Hours / Voltage) and (12Volts battery will be used)
battery capacity in Amp Hours = 5760 wh / 12 volts = 720 Amp-Hours

OK error here but in your favor. For battery you use actual Daily Watt Hours, not adjusted. [5 x 1152] / 12 volts = 480 AH @ 12 volts.

As Rich has pointed out you do understand the cost issue correct? This little system of yours that generates 11 to 17 cents per day of electricity will cost you around $3,000 once completed just for the major equipment purchases. equipment. The battery cost alone is going to cost around $1300 and need replaced in about 3 to 5 years. Assuming you can make it last 5 years means you are paying in battery cost alone $1300 / 2100 Kwh = $0.62/Kwh or roughly 4 to 5 times more than your electric company charges you. You do know that right?

[emdep3000]

Thank you SUNKING for helping to check the calculation again and also for reminding me about the cost of going "green" . Well, I do realize that it's a bit expensive to start a green project but I want to learn this "greeny" stuff. In order to learn, you need to get your hand dirty right

So, I guess I'm looking at total around $2000 USD for a complete setup for my project (Sine Wave Inverter 300W = $24 + 500W solar array = $760 + 480AH Battery = $1000 + 40A controller = $200).

I do have one more question and hope you guys have answer for me:

How far can I run the cables from Solar Panel to Charge Controller/Battery Bank? I want to put solar panels in the backyard and the charge controller/ battery bank in the garage but not sure what is the maximum of the cable length that I can run.

[Naptown]

That will depend on the voltage, amps, distance and wire size.
You want to keep voltage drop less than 2%

[Sunking]

How far can I run the cables from Solar Panel to Charge Controller/Battery Bank? I want to put solar panels in the backyard and the charge controller/ battery bank in the garage but not sure what is the maximum of the cable length that I can run.

If money is no objest as far as you want. The challenge of low voltage is power loss on the wiring. Once you get more than 20 feet 1-way it gets real expensive real fast. I cannot answer your questions because you have not specified the panels, charge controller, and distance.