We operate a range of renewable energy PA systems, mainly
pedal powered, and all running on only 12 Volts. The low voltage operation
makes for high efficiency and portability as well as making them very safe
to use, even in damp ground conditions.
Low energy systems are ideal for amplifying "unplugged"
setups or reinforcing acoustic performances. The absence of Mains power
virtually eliminates the possibility for hum or interference but can be
a problem for more "electric" lineups where musicians need their own backline
amps. To get around this problem, the larger systems can incorporate 12
Volt Bass and Guitar/Keyboard amps with their own pedal generators. The
magic phrase to use when talking to Health and Safety Officers is "Extra
Low Voltage Temporary Installation", which means anything operating
on less than 50 Volts and not fixed down. All our PA systems fall into
this category, as do things like Walkmans and torches.
PA systems are a good way to demonstrate small scale renewable energy and particularly pedal power as they make very effective use of it. The amount of energy produced by a person pedalling can be disappointingly small - about 100W of mechanical which translates to only about 60W of electrical energy by the time it's been through whatever generator you're using. However, using a battery as a reserve, you can run about 150W of amplification from this input as the average power taken by an amplifier is only about a third of the full power, even for the 'loudest' dance or grunge music. Although you can get a very impressive effect from the output of a couple of pedal generators and/or solar panels, it's best to stay in the sub-kilowatt range otherwise the number of generators becomes cumbersome.