NTREG Member Projects - Solar Trailer (Dan Lepinski, owner and designer)

In April 2001, the City of Dallas, Texas held Earth Day at White Rock Lake Park. The City prohibited open flame of any type in the park at the time, so food vendors brought electric cooking equipment .. and everyone plugged in. The overload that resulted tripped the main circuit breaker for that area of the park. Food quit cooking, presentations stopped, and the soundstage went silent. Thus was born an idea .. to provide future soundstages with totally independent, solar-derived power. What better way to celebrated Earth Day than to use the sun's energy for such a key aspect of the event?

Solar panels were assembled, batteries purchased, and inverters were donated by Exeltech. In 2002, the Dallas' Earth Day soundstage was powered by 100% solar electricity. This was the first time in the State of Texas a public soundstage had been totally powered by the sun.

In September, 2005, Hurricane Katrina devastated the Gulf Coast. Volunteer first responders, in desperate need of portable, fuel-free power, asked to use the solar equipment for their property- and life-saving efforts. Four systems were requested, but only two existed. Two more were hastily built, and all four systems were taken to the affected areas in a horse trailer. They were returned six weeks later, some the worse for wear, but basically intact.

Over the next several years, the equipment was used for a variety of purposes .. from Earth Day soundstages, to powering emergency communication equipment. The "erector-set" nature of the systems made set-up and take-down time consuming and difficult, especially for one person.

The solar trailer is the next generation, and a major upgrade from the old system. With 50% more solar panel wattage, double the battery capacity, and 12,000 watts in sine-wave inverters on board, the trailer will serve a multitude of needs. Its primary purpose will be educational, to showcase a full-size portable photovoltaic system. When not powering environmental events, the trailer is available to provide fuel-free, maintenance-free electricity for emergency communications to Search and Rescue Teams (Texas Task Force One), public events such as the Regional Boy Scout Jamboree held annually in Irving, Texas, powering support services for community events such as the Cowtown Marathon in Fort Worth, Texas, and many other functions.


For anyone interested in the technical details:
 
The trailer is a Wells Cargo 6' by 12' V-nose "Road Force" fully enclosed model, equipped with optional electric brakes. Wells Cargo was selected for the construction quality, and for the special "Tor-flex" axle that provides an exceptionally cushioned ride for the solar panels and electronic equipment.
 
Ten Sanyo HIT215N, 215 watt solar panels are mounted on the outside. Five are located on top, five more on the "driver's side" of the trailer. Output wattage of all PV decreases in hot weather, sometimes significantly. Sanyo PV are much less affected by heat than any other PV. They are also more efficient at converting sunlight into electricity than other PV on the market, no matter what time of day. When area is very limited, such as on the trailer, every watt counts. The Sanyo PV came out ahead of all others in that regard. I've seen more than 2400 watts being generated by the Sanyo PV, which are rated for 2150 watts. They are truly premium photovoltaic modules!
 
Eight, six-volt, 420 amp-hour Rolls-Surrette batteries provide more than 20 kilowatt-hours of storage. Rolls-Surette batteries are the best quality available. Rolls offers a seven year warranty, attesting to their faith in these batteries. The batteries, connected in two independent 24-volt configurations can be used separately .. or at the flip of a switch can be connected as one large system, doubling the battery capacity for one inverter.
 
Battery charging and maximum power point tracking are accomplished with dual Blue Sky Energy SB-50 Maximum Power Point Trackers. These units maximimize the harvest of energy from the Sanyo PV by up to 35% compared to directly connecting the PV to the batteries. I've seen more than a kilowatt being transferred from the solar modules to the batteries. The SB50 barely get warm. They are remarkably effective and well-built devices (made in the USA!).
 
Two Exeltech 5,000 watt inverters provide 120 volt pure sine-wave electricity for the most sensitive and demanding loads. The inverters can used individually, or simultaneously. Two separate 1,100 watt Exeltech sine-wave inverters provide additional power and serve as back-up to the large inverters. The smaller inverters can also be used independently for small loads. Total output of all inverters is 12,000 watts continuous .. and up to 25,000 watts peak. Made in America, Exeltech has been manufacturing inverters for 20 years. Their units, which provide pure sine-wave power, are among the most reliable in the world. They are rated for their full rated output 24/7. Audio engineers at events consistently rave about the clean and stable power from the Exeltech inverters .. often stating it's better than any power they've ever used from ANY source - inverter OR utility!

If by now you've noticed two totally separate solar electric systems designed into the trailer, you're correct. Dual systems provide total redundancy for enhanced reliability when the solar trailer is used to provide power during emergency situations.


I wish to publicly thank all sponsors involved with this project:

• Exeltech
  Two 5,000 watt sine wave inverters and two 1,100 watt sine wave inverters.
  
  
• Texas Instruments
  Sponsorship of the photovoltaic modules used on the trailer.
  
  
• Blue Sky Energy
  Two SB50 Maximum Power Point Trackers/Charge Controllers with Remote Digital Display and Battery Temperature Compensation.
  
  
• LI-COR Biosciences
  LI-200 Pyranometer (measures intensity of sunlight).
  
  
• APW/MayVille
  Rack mounts for the Exeltech inverters, Blue Sky Energy MPPT/Charge Controllers, and other hardware.
  
  
• W & W Silkscreening
  Vinyl wrap and exterior graphics for the trailer.