Credit: Linda Seid Frembes
Energy prices are a major concern these days for concert producers, who are responsible for transporting a village of people and AV equipment from city to city. So, they're turning their focus to conservation and the use of alternative energy sources. Two years ago, the Vans Warped Tour set out to demonstrate that “green” and audio are not mutually exclusive. What it has accomplished could provide valuable lessons across myriad AV applications.
The Vans Warped Tour, founded by concert producer Kevin Lyman, is part festival, part music showcase, and part marketplace. This year it ran from June to August with 46 stops across the country. The audience, mostly teens, offered the perfect demographic for demonstrating the potential of alternative energy in AV.
The Warped Eco Initiative debuted in 2006. Among its goals: use biodiesel for the tractor trailers to reduce carbon emissions and implement a program to reward volunteers for their recycling efforts. But perhaps most notably, tour producers wanted to create a mobile stage that was powered entirely by solar panels.
“Early on, there were challenges with being ecological on the tour, like a lack of biodiesel in all parts of the country,” says Tim Allyn of Sustainability Is Designed/Allyn Consulting, an environmental consultant for the tour. “But, thankfully, things have improved very rapidly in the past few years.”
Solar technology has also advanced rapidly. This year the solar stage was redesigned to maximize the energy potential of its solar array, which was built onto the tour's trailer, by using more of the available surface space and using both multicrystal and thin-film photovoltaic panels. Allyn worked with Stage Tech in Santa Fe Springs, Calif., on the stage's design.
Dubbed the “Kevin Says” stage, it runs on solar power all day while simultaneously charging the battery backups that take over at night or on cloudy days. The system includes significant battery redundancy and an attached 60-amp propane generator in order to switch over seamlessly from the solar infrastructure in case of a problem. Both the generator and the batteries are built into the steel center structure under the stage.
From a power consumption standpoint, the solar system was designed for 40 amps of constant max power, even though the total system has an 80-amp limit. “We were conservative on our specification because it is difficult to get real-world information on how much power stage equipment will draw, day-to-day, show-to-show. Amplifiers and dimmers are running between zero and 100 percent, a lot of variability and little constant. We're able to guide the client on what is appropriate for the system, and have built in some wiggle room on the upside,” says Allyn. “With new efficient products and LED lighting, we can get a lot of show out of a lot less power, without tripping the breakers.”
To find the most efficient audio system, Lyman turned to Dave Rat, owner of Rat Sound Systems in Oxnard, Calif. Rat suggested Allyn meter some rigs around town. The result was a specification given to loudspeaker manufacturer Eastern Acoustic Works: Assemble a full-bandwidth audio system with a 75- to 100-foot throw that can reach 100-105 dBA at front of house. Maximum power draw: 30 amps.
FINDING EFFICIENCY
The 30-amp limit applied to anything audio-related, including the main PA, front-of-house mix position, backline, and stage monitors. For a stage of the tour's size, it's not uncommon to specify 100 amps or more. The team used a pair of Lab.Gruppen fP10000Q 4-channel amplifiers, which continuously draw 10-12 amps with a real music signal. Because the amplifiers employ one less power supply and one less chassis to get four channels, there was less overall weight and power draw. Using two amplifiers, the team was able to power a main PA of eight EAW KF730 loudspeakers and four BH760 horn-loaded subwoofers.
Six EAW NT56 self-powered speakers, drawing 1.5 amps each, served as stage monitors, coupled with two EAW NTS22 subwoofers. In all, the monitor rig consumed 12 amps. For further efficiency, the FOH mix position also ran the monitor mix on a Mackie TT24 digital console that drew about 2 amps, meaning five monitor mixes and the FOH mix were handled by one mixing console rather than two.
For Tom McNabb, FOH engineer for the stage, introducing solar power didn't affect his job. “I was skeptical when I was first asked to work on a solar-powered stage,” he says. “But it is a very transparent system; the stage is totally mobile and self-sufficient.”
Up to 60 days of performance information was stored in the charger. Once a week, McNabb sent the information to Allyn, who kept tabs on the stage's real-world operation. “The propane generator has not been turned on once this tour,” adds Chris Anderson, the solar stage's stage tech. “At its lowest point, we had 82 percent of power left after two days of rain.”
Allyn says no special training was required to operate the stage. IT was pulled by a semi, like a standard mobile stage, with the only difference being the overall weight. “It is a bit heavier due to the solar rig. The solar batteries are bigger than car battery (70-plus pounds each) so Department of Transportation weight limits may affect the number of batteries you can carry,” he explains.
Is the stage a sign of things to come? As the audio industry moves toward lightweight products that consume less power, it could. Says EAW's Rich Frembes, who worked with Allyn on the project, “Similar to how advances in DSP technology are shaping our industry, advances in solar power and energy efficiency will too.”