Model 510
Off Grid Solar Lighting
This page describes the installation of an off-grid lighting application on a barn. The installation was done to provide outside lighting and interior lighting. The outside lights come on automatically every night and the interior lights are switched on as needed.
Battery
When configuring a system like this, the first thing to be considered is sizing the battery and PV panel. LED lighting was used to minimize power.
The lighting power consumption was determined as follows:
- Outside Lights
- 4 lights at 130 mA per light - .52 Amp
- Interior Lights
- Rope Light (12 feet) - 1 Amp
- 5 spotlights at 140 mA per light - .56 Amp
It is always better to oversize the battery. Therefore we sized the battery based on all lights being on for 8 hours of darkness. AH = 2.08 Amps X 8 hours = 16.64 Amp hours.
We looked rechargable lead acid batteries available from www.batteriesandbutter.com and we had a choice of:
- SLA10-12, a 12 Volt, 10 AH battery for $45
- SLA18-12, a 12 Volt, 18 AH battery for $55
- SLA24-12, a 12 Volt, 24 AH battery for $75
The obvious selection was the 18 AH battery. When this battery is fully charged, it will be capable of handling the entire lighting load all night. Since the interior lights will not always be on, there is plenty of capacity to provide light during nights following cloudy days.
PV Panel
After selecting the battery, a photo voltaic panel must be selected that will provide enough current to reliably charge the battery. In this application, the battery works all night, and gets recharged during the day. As a rule of thumb, a battery can be safely charged at about 10% of the Amp-hour rate or 1.8 Amps in this application. The Model 510 Controller will manage higher currents and preserve battery life by slowing the charging rate as the battery approaches full charge.
The list below shows the maximum power current for several photovoltaic panels.
- 80 Watt - 4.5A
- 65 Watt - 3.75A
- 50 Watt - 3.11A
- 43 Watt - 2.48A
- 40 Watt - 2.4A
- 30 Watt - 1.7A
Any of the panels listed will work in this application. The choice comes down to price and possibly physical size. We used the 43 Watt Kyocera KC40T in this application because the price was very competitive when we bought it.
The KC40T is 20.7 x 25.7 inches (526 x 652 mm) and can be mounted on a light wood frame. The photo below shows the frame being prepared.
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Solar Panel Angle
During summer, the sun sits a lot higher in the sky that during winter. Some installations change the angle for the four different seasons to get the maximum output. However, this is difficult to achieve if the panels are sitting on a roof, so a happy medium is usually found. Since the winter has the fewest hours of sunlight, many fixed mount panels are mounted at an angle that maximizes output during the winter. Another theory is that the angle should be set for spring and fall, and the ouput will be somewhat lower in winter and summer.
In general, solar panels should face South in the Northern Hemisphere and North in the Southern Hemisphere. A solar panel's angle should be set to the equivalent of your your latitude plus 15 degrees during winter, or minus 15 degrees in summer, and latitude minus 2.5 degrees in spring and fall. For example, the latitude of this installation is 42 degrees. As you can see in the photos, the angle is set to slightly favor winter.
Wiring
To simplify wiring, we recommend using one or more distribution boxes. Distribtion boxes are available from ECC or they can be built from parts available at any good hardware or electrical supply store.
With 12 Volt DC lighting, it is not necessary to meet electrical code. However, if local code officials will be checking and approving your installation, you may be required to wire to NFPA 70 (or local codes).
Safety
All wiring should be done with the battery or PV disconnected. We recommend disconnecting the plus lead from both the battery and photo voltaic panel.
The wiring can be done following our Lighting Schematic (Adobe PDF) and a schematic of the Lighting Distribution Box (Adobe PDF).
For interior lights we used a mix of Rope Light and LED Flood Lights. We purchased custom cut rope light from Novelty Lights.
http://www.noveltylights.com
The flood lights are available from
http://www.oznium.com/high-intensity-led-floodlight.
We mounted three on
an 8 foot strip of wood. The photo below shows the terminal strip that we used. Mounting the lights on a strip of wood
makes the installation easier because you can do all the mounting and wiring on a bench, and then simply screw the wood strip
to the ceiling or wall at the installation site.
Please contact ECC for pricing and ordering information.