The E motion system is true hybrid-electric drive. It can power the drive motors solely by electricity from the batteries - which can be charged from renewable energy sources - or from a DC diesel generator feeding through the battery pack.
E motion hybrids incorporate the latest in solid state electronics and permanent-magnet motor technology. One key to our system's efficiency is our motors' ability to turn larger, more efficient propellers than a comparable diesel engine can. A large prop turns more slowly and pushes more water in each revolution
Another is its ability to obtain energy for recharging the batteries from multiple inputs, especially renewable sources:
1- Regeneration from wind power - when the propeller turns in the wake under sail, the drive motor automatically becomes a generator and sends electricity back to the batteries
2- Solar cells and wind turbogenerators - If the boat has space available, twelve 12 volt solar panels can recharge the 144 VDC main battery pack, while a wind turbine tops up the house batteries. An "up-converter" is being developed to allow lower-voltage solar panel combinations, such as 48 V from four 12V panels, to charge the 144 VDC main battery pack
3- Dockside plugin - standard AC power is fed into the battery pack through a battery charger.
4- Backup diesel generator - produces direct current at 144 volts to charge the batteries directly.
Total power package
The E motion system provides power not just for propulsion, but for every system on the boat.The main battery pack is both the central storage bank for all electrical inputs and the source of electricity for all power consumers in the system.
The battery pack delivers 144 VDC to
1 - the digitally controlled propulsion motors
2 - a DC-DC converter that provides 12 VDC or other low voltages to the house power system
3 - a DC-AC inverter that provides 110/220 VAC to AC appliances.
This central source of power results in substantial reductions in diesel fuel, noise, fumes, routine maintenance and repairs. In a monohull, our single, silenced, easily accessible diesel genset replaces two internal combustion engines - the diesel propulsion engine and the diesel generator. In a catamaran, it replaces three -- the diesel generator and two propulsion diesels.
"Plug-in hybrid" is the latest buzzword in environmentally friendly automobiles. It's a hybrid-electric car with a gasoline engine and batteries that can be recharged by plugging into an electrical outlet.
Ford is talking about introducing its first plug-in hybrid in 2009. So is Toyota. GM plans to sell its first, the Chevy Volt, in 2010.
Dave Tether has been making plug-in hybrid boats since 1994.
"I don't know why it's taken car companies so long to come up with the idea," says Tether, the CEO of Electric Marine Propulsion (dba E motion hybrids.) "It's basically just a hybrid with an extension cord."
Battery-only vs hybrid
The cleanest, quietest power source available for a car - or a boat - is an electric motor running on batteries. But batteries don't last too long before they need to be recharged.
GM's first commercial electric car, the battery-only EV-1, had roughly a 70-mile range. It was recharged by plugging into special charging stations, but they were few and far between.
Hybrid cars, such as the Toyota Prius, have an electric motor, a small battery pack and a gasoline engine. They recharge the batteries from the engine alternator. There's no plug.
It was only recently that car companies put the two ideas together and began designing hybrid cars with batteries that could be recharged by plugging into an electrical outlet. "I guess that's why they pay GM's Chairman $10 million a year," Tether says. "They knew he'd figure it out sooner or later."
Cars two, boats four
Although plug-in hybrid cars have just two charging options, Tether's E motion hybrid boats have four. "We run our boats off the batteries whenever possible," he says, "and then recharge them with whatever power source is available - sun, wind, dockside AC, or when there's none of the above, the diesel generator.
"It's a pretty simple concept," he says. "The more ways you have to recharge your batteries, the more you can motor."