CCAT Yurt: L.E.D.'s Light the Future
by Idyath Yassemi

Project Idea

Lights were needed in the yurt to make the space available for nighttime activities. To accomplish that, I installed a 12-Volt DC LED lighting system powered with a PV panel and battery. As a permanent part of CCAT, it will also demonstrate low wattage, easy to transport systems to people traveling abroad with the Peace Corps and for others with similar needs.

What made me do it

I chose the LED project after learning of CCAT’s desire for one, to learn about Photovoltaic systems first hand. Luckily, my husband is a builder and was able to help me properly put together and install the CCAT LED lighting. I am also grateful for the help of Real Goods and Six Rivers Solar for reviewing my calculations so I could feel confident about the purchase choices I made for the project.

LED Information

LED (Light Emitting Diode) is a semi-conductor diode that emits a single color (monochromatic) light when operated in a forward-based direction. Many have life spans of 100,000 hours or over 11 years of continuous use. LED’s are extremely durable because there is no glass to shatter and no filament to break. They are not damaged by vibration, heat, cold or moisture and last for generations. They do not waste energy or require large amounts of batteries.

Methods and solutions

I started by creating a proposal that outlined my plan of action while researching LED’s on the Internet and at local electrical stores. I purchased an individual LED from Radio Shack just to experiment with it in the dark at home with a 9-volt battery. Initially, I was going to create my own bulbs with several LED’s wired together in an old hose to make a flexible Light that could hang around the Yurt ceiling. However, after much deliberation, I decided to purchase the pre-made bulbs. I wanted to be sure that they would last. I met with Emelia, CCAT co-director, to discuss any specifics about what they wanted for the project, and spent time at the Yurt deciding what would look best for the site.

Fortunately, I was authorized to purchase a new stand alone PV system. I did a preliminary solar site assessment of the apothecary roof, where the PV panel is housed. Using the Real Goods Source Book system-sizing workshop on page 188, I did a variety of calculations to help decide how big a system to buy. By this time, I had already decided on the lamps and knew that they used around 10 watts a day if every light in the system was on for 5 hours. The winning system was comprised of a 10-watt panel with a 20-year warranty and a 12-volt, 32 Amp hour battery. Additional items that I felt were important to complete the balance of system were a charge controller to regulate the battery, safety disconnect switch, grounding connection, battery box, circuit breaker box, mounting rack and volt meter.

I wrote a design proposal, which I turned into Emelia for her approval prior to purchasing any materials. Included in the proposal were itemized purchases needed for the system and a drawing of the yurt’s interior showing light positioning. When I was ready to buy the materials, I tried to stay as local as possible. Michael Eckhard of Six Rivers Solar in Eureka, double-checked my calculations before ordering the PV panel and battery for the system. He suggested that we could just make the mounting rack ourselves at considerable savings. My husband Mike, handmade it to fit the panel from a 6-ft piece of ¾ inch aluminum angle iron, and it’s even adjustable. I was next prepared to buy at Real Goods, when instead I chose Solutions in Arcata to order the 4 LED bulbs, LED reading lamp, charge controller and voltmeter for the project. This decision altered the lamp choice, as they did not offer exactly the same products. I am happier with the LED Edison based bulbs that replaced another type of LED lamp and their versatility.

Since Mike has worked in construction for a long time, he acquired various building materials that we were able to make use of in this project, instead of purchasing them. I bought old track lights and an outdoor porch light for the project at the Arcata Recycling Center Depot. At Pierson’s and Hensel’s Ace Hardware in Eureka I bought the low voltage cable, electrical boxes, connectors, heat shrink, screws etc.

Analysis of technology

LED bulbs are a good choice for low wattage applications and they last approximately 100,000 hours or about 11 years of continuous use so they don’t need much maintenance. The Edison based bulbs give off 11 lumens of light, which is comparable to 11 burning candles, while using less than a watt of electricity. Though the ones installed in the Yurt are not very bright, there are lights available that can be, just by adding additional LED’s. Even with multiple LED’s in one bulb, if one LED goes out, the rest still work. LED’s are an extremely energy efficient lighting available today. There are LED Christmas lights that use approximately 14.4 watts. They can be used in flexible boards, in stoplights, in flashlights, in spotlights, in glow pens that write in the dark, etc. I didn’t come across any environmental problems with this project.

Light Calculations

.7 watts x 5 (hours a day)=3.5 watts (day)
Porch light & 3 track lights, 4 bulbs x 3.5 watts= 14 watt hours

.36 watts x 5 (hours a day)=1.8 watts (day)
Reading light

The Yurt’s LED Lighting system, if every light were used 5 hours a day, would consume 15.8 watts of electricity per day.

PV Panel & Battery calculations
Solar Living Source Book page 188 System Sizing Worksheet

For Panel
5) 15.8 watt hours a day
6) 12 Volt
7) 15.8/12=1.31
8) 1.31 x 1.2= 1.57
9) 1.57
10) 3.5 hours of sun a day
11) 1.57/3.5=.44
 
 
 
 
 
 For Battery
20) 1.57
21) 8 day capacity
22) .5
23) 1.57 x 8=12.56/.5=25.12
24) 32
25) 25.12/32=.785
26) 12
27) 12
28) 12/12=1
29) .785
30) 1 x .785=.785
=1 battery

A listing of the items purchased for this project

$29
Photovoltaic Panel from Six Rivers Solar$129
    APC PV Module, 10watt, 12volt, laminated, unframed, Manufactured for APC by a company in China. The inventory # is 11-114-010, 20 year warranty from 6 rivers
12 V/32 Amp hour battery$ 69
    True deep cycle gel battery, Recommended by the National Renewable Energy Labs. They are maintenance free, no equalization charging is required. May be airline transferred (24.2 lbs.)
LED Edison Based Steca Bulbs (4) $ 29 each$116
    .7 watts, 3 in swiveling track lights, 1 for front porch
LED Reading lamp "Cabin light"
    .36 watts, On/off switch, 3 LED’s, also for lighting
Indoor chalk board, swivels
Morningstar Sunguard Charge controller$30
DigitalVoltmeter$42
    minimal expense for informative and safety purposes, easy to read
Wire (16 gauge)$22
Used track Light Fixtures (3) $2 each$6
Electrical Boxes/covers$8
Nuts and Bolts$5.70
Heat Shrink$1.59
Tax$12
Total$470

(The total estimated cost for the Yurt’s LED system was between $400-$600, leaning towards the cheaper side which I did.)

a listing of items that were donated to this project
Wire (14 Gauge) 30 feet From Battery to Junction box
Used Battery Box & Shut off box Handle
Wood scraps for Battery Box, Porch Light fixture & Shut off switch box
Junction Box
Light Switches
Screws
Additional Heat Shrink
Used PVC underground conduit pipe
6 ft Aluminum ¾ inch angle iron
Solder
Staples
Outdoor on/off switch/box for porch

Project summary

At home, my husband and I built a wooden battery box that also houses the charge controller and voltmeter with a lift off top.

With scrap wood, we built a wooden box to go around the old porch light that I painted with non-toxic paint. And for the emergency shut off switch for the PV system, scraps of cedar and plywood made the box in the apothecary that houses it. I cleaned up the old track lights and my husband rewired them to work with the new system. We soldered the bolt connectors between the battery and the junction box and used color-coded heat shrink to seal them well. Mike also built an adjustable mounting rack for the panel.

On Saturday April 21rst, Mike and I installed the Yurt’s LED system from around noon until after 6 p.m. We started by screwing the mounted panel to the apothecary roof, and the battery box to the interior floor. We hooked the positive and negative leads from the panel to the charge controller, then connected them to the battery. I carefully dug a channel large enough for the PVC pipe to go under the walkway between the apothecary and through the yurt’s border garden to the edge of the building. The junction box was screwed to the bottom of the yurt and electrical wiring boxes to go below each of the lights were screwed in place. We threaded the 14-gauge wire from the battery through a small hole in the apothecary through the underground pipe to the junction box. I used the larger gauge wire (14) to the junction box because it held the entire load and I wanted to reduce voltage drop. From the junction box, to each of the lights (and switches) in and out of the yurt, we converted to 16-gauge low-voltage wire using wire nuts and stapled the wire closely to the building. We used 16 gauge because it carried smaller loads for each individual lighting application; it was easier to work with and was less expensive.

The 14-gauge wire was threaded around each of the interior ceiling boards. Each of the lamps were connected with wire nuts and installed on top of the boxes. The interior and exterior light switch boxes and plates were put in convenient places. Finally, we connected a copper grounding wire from the negative terminal of the battery to the grounding rod already located next to the battery box. We were thrilled when the installation was complete and we turned the switch on and it worked perfectly!

The above drawing is looking up at the Yurt ceiling. It is drawn with 3 LED bulbs housed in separated track lights. The small cylindrical shaped swivel lamp can be used to shine on the black board, or for a more direct reading light source.

The drawing below of an LED lamp to the left of the outside door is a welcome night light with a weatherproof switch.

References and Resources

www.ledlights.com
A web site that contains information about LED’s and sells them

www.jademountain.com
Sells LED’s. Especially interesting, a 12V LED system.

www.realgoods.com
Not many LED’s though the moonlight path markers look good.

www.roman.com
Uniquely designed LED lights (in Christmas strands)

www.theledlight.com
Sells LED’s. Flexible LED boards.

Real Goods Solar living sourcebook
Tenth Edition, Edited by doug Pratt, pp. 188
Chelsea Green Publishing Co. 1999

Personal evaluation

I had my hand in every aspect of this project and was lucky enough to have the help of my husband, Mike to fill the gaps of my knowledge with wiring and lighting system information. I learned how easy it is to set up a workable solar system. The wiring is not as complicated as I once thought and neither is soldering. I helped design and sand the wooden boxes that were built. The project unfolded well and I felt that I had time to do most everything.

I was initially interested in creating something interpretive-wise as well, so that others could easily learn about the system. However, due to time constraints, I will not be able to at this time. I still plan to engrave the words “Emergency PV Shut Off Switch” on the wood box in the apothecary, as well as to neaten some of the wiring up with small staples. Finally, I would like to wrap the interior lighting cord with something decorative, like ribbon or hemp rope for aesthetic purposes before the semester ends.

I am very proud of the LED Lighting project for CCAT’s yurt. We worked on this with enthusiasm and hope to install PV panels on our home over the summer, possibly with an LED light or two. I believe that lighting the Yurt is a helpful project that will be useful for many years to come with little to no maintenance. It will allow people to hold meetings/hang out in the Yurt in the evening when it is dark without the danger candles can bring. It is a good demonstration of a low wattage system that is easily portable and sturdy for the visitors of CCAT.