CCAT Solar Charging Station: Difference between revisions

The Campus Center of Appropriate Technology is a demonstration house located on the Humboldt State University campus, Arcata, California that is a resource for students and faculty. CCAT has many different technologies on display such as: solar panels, rainwater catchment, organic gardens, a greywater marsh, and an experimental composting toilet, among other things. These projects are on display as educational tools to the community and information is provided through CCAT/Appropedia on how to recreate these technologies on your own. The Solar Charging Station at CCAT will align with the mission of CCAT to provide education and resources to the community, by clearly expressing how off-grid solar works, while being functional for cell phone/laptop charging.

Understanding the market

What we have:

• 10 functioning solar panels donated to CCAT
• A kiosk in the center of CCAT as a space to set up our system
• Scrap metal and wood
• High quality 2 x 4s
• CCAT tools/hardware
• Materials for making a guest book
• Some materials for charge controller housing

What we need:

• A sealed battery
• Charge controller
• Waytek USB plug for load
• USB split plug for multiple chargers
• Copper wire #8 bare, 20 feet
• Ground rod, 8 feet
• Acorn nut
• Panel wire, 8 feet
• MC 4 branch 10 gauge PV wire
• MC 4 wire 60 inches cut in half
• Conduit
• Battery box
• Lock for battery box
• 8 gauge wire from battery to charge controller
• Fuse block, 10 - 15 Amps near battery

Project goals

By the end of the project we want to have accomplished the following goals:

1. Have a functioning solar charging station at [CCAT][1]
2. Provide an effective demonstration of off-grid solar
3. Complete a step by step guide to construction here on Appropedia for those who want to build it themselves
4. Complete a project report with a cost, buyback time, and energy return on investment analysis
5. Create a prototype and precedent for future such stations on the HSU campus

Design

Energy calculations:

The project location will be the roof of the CCAT demonstration wall kiosk. We measured solar insolation at this location with a Solar Pathfinder and assessed other sites at CCAT as well. We chose the kiosk for having the most solar insolation on an already constructed, available rooftop, and because it is in a centralized location at CCAT.

Full sun hours at location: 2.05 hrs/day Panel power: 100 Watts Balance of system efficiency assumed at: 0.8 Number of panels: 2

Edaily = full sun hours * panel power * efficiency Edaily = 2.05 hrs/day * 100 Watts * 0.8 = 164 Wh/day / 1000 = .164 kWh/day * 2 panels = .328 kWh/day

.328 kWh/day * 365 days/year = 119.72 kWh/year

Construction

The panels will be positioned vertically and staggered on the kiosk rooftop, facing south, at a 30 degree angle for maximum sun exposure.

Phase 1: Stabilizing the Kiosk Roof, Building the Panel Racks, and Mounting the Panels

Stabilizing the Kiosk Roof:

First, we noticed the kiosk roof has a wobble to it due the the rooftop having a centralized beam and no side support. In an attempt to stabilize the roof, we added additional screws from the main support beam to the support beams from the main wall.

Building the Panel Racks:

Second, we began constructing our own panel racks. We chose building our own over buying racks to attempt to keep within budget and recycle materials at CCAT. We built our racks out of scrap metal and wood. The panels are attached to the rack with brackets found in the CCAT tool shed and the tools used were also available at CCAT. Our priorities for the racking were that they be:

1. Stable, attached firmly to the panels
2. Supporting the panels at a close to 30 degree angle
3. Reusing materials at CCAT

We addressed rack stability by experimenting with different heights of the rack while still maintaining a close to 30 degree angle. The back legs of the panel ended up being around 2.5 feet long. We preferred the back legs being shorter versus longer to prevent the panels from picking up wind during storm events. We also included a crossbeam between the back two legs to prevent the panel from swaying. The front of the panel will rest upon two wooden planks that will attach to two angled shims on the roof. The panel front will be as low to the roof as possible to prevent swaying in the wind.

To find the appropriate lengths of the racking to maintain a 30 degree angle we used simple geometry:

Mounting the Panels:

Costs

We have a $400 budget from CCAT for this project.

Buyback:

The system will save the campus around $20 each year in electricity costs and will therefore buy itself back in about 21 years. ($400/$19.12/year = 20.88 years).

Discussion

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Next steps

The next steps.

Conclusions

Your conclusions.

References

Contact details

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