Propulsion

Combo Parallel Hybrid / Electric Propulsion System for S/V Lynx

When it comes to the propulsion for S/V Lynx, we decided, long ago, that we wanted a hybrid system. However, not just any hybrid. There are big advantages to a combination Parallel Hybrid in one hull and and electric motor in the opposite hull.

Combi
E-Propulsion Systems and Nanni Diesel

Port Hull

In the Port hull, there will be a Nanni 80 hp diesel with a Combi 25 kw electric motor attached in parallel. Here is a list of the features:

Nanni N4.80 80 hp Diesel - This is a direct injection diesel engine, which means that it is more serviceable to us, with less need for complex diagnostic tools in case of any issue. The engine block is from Kobata, which is a very common engine in the world, and parts are plentiful to source. This engine can propel the boat even if the parallel electric motor is non-functional for any reason.
Combi 25kw water cooled, electric motor in parallel - With few moving parts, these motors have little maintenance required. Just a belt and a couple of bearings. It can propel the boat even if the diesel engine is non-functional for any reason.
Regeneration: While sailing, the Brunton's Eco*Star prop can turn the Combi 25kw motor, regenerating up to about 2 kw of power, per prop, back into the batteries when sailing at or above 10 knots. At 8 knots we expect about 1 kw per prop.
Lower RPM Diesel Motoring: Because of the load that the 25kw electric motor puts on the diesel, we can run it at a slightly lower RPM, where we gain more fuel efficiency. Without the load of the electric motor, the diesel requires a higher RPM.
Fuel Savings from duel prop propulsion from one engine: Because we are running just one diesel engine at a lower RPM by turning the electric motor, that motor can send around 6 to 10 kw of power to the electric motor in the port hull, which allows it to propel the boat without pulling energy from the batteries. This helps balance out the propulsion and makes it so that we do not have to use the rudders to offset the heading, which causes drag, so we will get more speed and better fuel efficiency.
Generator mode: By using the new electromagnetic clutch we purchased from Combi, we can disconnect the propeller shaft with the flip of a switch at the helm. This allows us to run the diesel at anchor as a generator. The diesel is put under load from the attached 25kw electric motor, so that keeps the diesel happy, and we generate up to 12 kw of power into the batteries.
Electric Mode: While we have battery power, we can propel the boat purely on electric motors, one in each hull. This is quiet, fumes free, and burns no fossil fuel. With our 33 kWh battery, we can motor at a cruising speed for around 3 hours, enough to get us out of port and through the morning, which are often still wind hours. During the day, we can recharge from solar and/or regeneration and then have power to electric motor when we reach our destination port.
Sailing Mode: By adding Brunton's Autolock Rotor and caliper, coupled with a set of cable levers at the helm, we can lock or unlock the prop shafts from the helm. Unlocked, we will regenerate power, but while locked, we gain 85% less drag, which can mean up to a knot increase in boat speed. Besides less drag, this also keeps the props and propeller shaft from spinning, and that keeps our cutlass bearing from wearing out prematurely.
Less Vibration: By adding Brunton's Sigma Drive to both prop shafts, we will cut down on vibration felt in the boat while motoring or regenerating. It also puts less strain on other elements of the system because it can handle up to 3 degrees of movement.

Starboard Hull

In the starboard hull, there will be just a Combi 25 kw electric motor. Here is a list of the features:

Combi 25kw water cooled, electric motor - With few moving parts, these motors have little maintenance required. Just a belt and a couple of bearings. It can propel the boat in combination with the other electric motor or diesel engine to keep the steering balanced while under engine/motor power.
Regeneration: While sailing, the Brunton's Eco*Star prop can turn the Combi 25kw motor, regenerating up to about 2 kw of power, per prop, back into the batteries when sailing at or above 10 knots. At 8 knots we expect about 1 kw per prop.
Control Box: The brains of the hybrid system are located in the starboard hull, along with the electric motor.
Sailing Mode: By adding Brunton's Autolock Rotor and caliper, coupled with a set of cable levers at the helm, we can lock or unlock the prop shafts from the helm. Unlocked, we will regenerate power, but while locked, we gain 85% less drag, which can mean up to a knot increase in boat speed. Besides less drag, this also keeps the props and propeller shaft from spinning, and that keeps our cutlass bearing from wearing out prematurely.
Less Vibration: By adding Brunton's Sigma Drive to the prop shafts, we will cut down on vibration felt in the boat while motoring or regenerating. It also puts less strain on other elements of the system because it can handle up to 3 degrees of movement.

Propulsion Conclusion

Best of the hybrid systems
We did a full comparison of our Combination Parallel hybrid diesel/electric system against a pure diesel system, a standard hybrid, and a duel parallel hybrid.

Here is why this Combination system is best:
1) It is lighter by hundreds of pounds.
2) It requires less maintenance.
3) It is more fuel efficient.
4) It is a safer system.
5) It saves you a huge number of hours of listening and smelling a diesel engine.
6) And, when it comes to cost, though it loses to the diesel system in initial installation cost, it makes up that amount over time in fuel and maintenance savings.

The conclusion we reached from that data: The Combination Parallel wins in every category except initial cost.

So, hands down, this is the best system we have found based on all the numbers.

NOTE: If you are interested in all the details of our comparison of all the systems, we offer our information and calculations for our patrons to view. They may access this data in the Crew Only section of the website