Most Popular Content

**Naptown** · 09-24-2012, 05:10 PM

Use this spreadsheet
You may want to tweak the depth of discharge On this one it is limited to 20% for most cycles from the battery and designed for 2 days autonomy. going to a 40% DOD maximum for 2 days autonomy
This means you will end up doubling battery capacity, solar capacity etc if you go for a 40% DOD or 4 days autonomy.Off grid calculator excel 97 version (2).zip
Easiest way to tweak this is double your loads.
Check with PVWatts or Gaisma to determine actual insolation during the worst months. Other than tropical areas it is rare to see 5 sun hours a day during the winter.

**classradiance** · 09-26-2012, 03:07 PM

Originally posted by Naptown

Use this spreadsheet
You may want to tweak the depth of discharge On this one it is limited to 20% for most cycles from the battery and designed for 2 days autonomy. going to a 40% DOD maximum for 2 days autonomy
This means you will end up doubling battery capacity, solar capacity etc if you go for a 40% DOD or 4 days autonomy.[ATTACH]2295[/ATTACH]
Easiest way to tweak this is double your loads.
Check with PVWatts or Gaisma to determine actual insolation during the worst months. Other than tropical areas it is rare to see 5 sun hours a day during the winter.

Great stuff . . Thanks
Would it be safe to say that Deepest Winter = Diesel Generator or am I going down the wrong road? And I am only interested in Lighting by the way.
Heating seems a distance possibly in a year.
I have more or less determined just 5 panels and 2 batteries for the entire house for the year ... so much for 16 panels and all that ( I am questioning the consideration of such kit)!!

**Nishit Shah** · 06-20-2014, 11:18 PM

Very good

Very good.

Originally posted by classradiance

calculations for Home / Boat / Caravan / Shed

[ATTACH=CONFIG]2294[/ATTACH]

1.Add up the hours that each light will be on for to get the Total of Energy Consumed.
2.From that you can Calculate everything you need IE: Solar Panel / Battery / Charge Controller
------------------------------------------

My Calculations
3 Zones
1 X LED SPOT @ 10W + 2 x LED FLOOD @ 15W
on for (SEE CHART) hours per night
...................

-Watt/Hour Chart- - Only ever use 12 volt LED lights -

3 Room scenario

kitchen/Diner 15W on when required daily average use -- 3 hours = 45wh
Bedroom 10W on when required daily average use - 2 hours = 20wh
front Room 15W on when required daily average use - 8 hours = 120wh

Total usage per night in Winter = 185wh/d
-----------------------------------------------------------------------------------------

-Load and Battery -

House Lights Consumption = 185Wh
185 watt-hours divided by 12 volts = 15.42 amphours taken from system in 1 night

Because we can only use half the energy in a lead acid battery without harming the battery,
the minimum battery size is 15.42 amps x 2 = 30.84 amp hours.

I want my system to be reliable if we have four consecutive days of cloudy weather,
4 days of autonomy x 30.84 = 123.36 amp hours for the battery. = 124 + amp hour battery
(Required Battery Bank = 1 x 130 Ah True Deep Cycle

-------------------------------------------------------------------------------------------

-Charging Battery from Panel-
This installation is in a location that gets 5 hours of full sun per day.
Check the charts for this depending on the month in the Season.
To recharge the battery for one day of use we need 30.84 amps in 5 hours = 30.84 / 5 = 6.17 amps from a 12 volt solar panel array.
------------------------------------------------------------------------------------------------------------------------

-Solar Panel -
Most load calculations include a discount factor for the inefficiency of recharging the battery.
20% is typical. 6.17 / 0.8 = 7.71 amps.

A single 140W solar array that has an Impp (amps maximum power point) of 7.7A would be suitable

------------------------------------------------------------------------------------------

-Charge Controller Rating in AMPS-
The 140W solar array has a short circuit amp rating (Isc) of 8.2A 8.2A x 1.25 = 10.25A
use a 10.3A or larger charge controller with this array to charge the battery.

Cheap example - 20A Unit
For best efficiency to charge use an MPPT Type.
------------------------------------------------------------------------------------------

- estimated Cost of mentioned Materials - 20 years / $450. = $500./240 months = £2.08 month = .52 per week ....wow

Have seen 140w poly panel on Net for $170 inc delivery
Have seen 130Ah Varta Leisure Battery 12V 130Ah for around $150 inc delivery
20A Charge controller $20 - $60 - mppt prefered of course
3 QUALITY External (For in or out & VERY BRIGHT) LED Lights 2 x 15w/1 x 10w = $60
100m of .75mm twin and earth from wholesalers = $30
Mounting Bracket for Panel = $20

Estimated Total = $500ish

Also required - Fuse box / switches / bits ..

-----------------------------------------------------------------------------------------
-Solar Panel specification-
STK-140P6-A ...... manufactured by 3E
Related power
140W
Open circuit voltage Voc(V)
23V
Short-circuit current Isc(A)
8.2A
Optimum operation voltage Vmp(V)
18.3V
Optimum operation current Imp(A)
7.7A
.......................

Thanks to everyone who places information out there on the WWW
Hope the above can inspire you.
Not mentioned above are Switches, Inverters, Distribution, Heating, Health & Safety,
etc ... Caution -12V Batteries can Cause Fire if not Fused or Stored Correctly-

you may find the 30% discharge rule more convenient !!

Mod note - email removed

Most Popular Content

3 room calculations for solar lighting

3 room calculations for solar lighting

Comment

Comment

Comment