Center for Environment, Commerce & Energy: Renewable Electric Catamarans

Hybrid-electric drive

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.

When the sails go up in open water, you throttle the motor back so it's just ticking over. The motor turns the prop slowly while you sail. It corkscrews through the water and cancels most of the drag. When boat speed increases - from sliding down a wave or the wind picking up - the prop is forced to turn faster as the water rushes by. The motor then 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.

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.

One 144 v battery packs connected in parallel.

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.

Diesel reductions

This central source of power results in substantial reductions in diesel fuel, noise, fumes, routine maintenance and repairs.

In a monohull, the 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.

Lagoon 47

The testtbed for the E motion hybrid system is a Lagoon 47, one of the company's most popular early models.

The original 10 ton cat came with twin 27 hp diesel engines. These were replaced with two nine kw electric motors, which turn bigger props than the original diesels.

The boat is equipped with 12 rooftop 12 volt solar panels, which directly recharge the main 144 VDC battery pack.

Specs

LOA	16.9 m	46'3"
LWL	15.32 m	42'8"
Beam	9.20 m	24'11"
Draft	1.2 m	3'11"
Disp	14 T	19,842 lb
Mainsail area	105 m2	710 ft2
Solent jib	40 m2	291 ft2
Spinnaker	180 m2	1292 ft2
Genset	15 kw
Motor	9 kw (2)
Prop	18x14 3 blade (2)
144V battery pack	AGM 4D
12V house batteries	AGM 4D
Inverter	Airpax 3500D

The main components of the E motion system are the motors, batteries, DC-DC converter (or cross-charger), generator and inverter. The generator and other electrical sources - regeneration, plug-in dockside power or144 V solar panels - feed into the battery pack. The battery pack then provides 144 VDC power to the motors and inverter. (See Technology for additional system description.)