|
Why is hybrid power so efficient?
- Acceleration and deceleration of the vessel is done by high torque electric motors not by an internal combustion engine.
- When the generators run - they alway operate at a single optimum speed.
- The electric motor gives direct drive without a gearbox.
- All "house-loads" including lights, fridges, air-conditioning, intelligent systems etc are run off the batteries meaning no auxiliary generators.
You can add renewable energy to a hybrid boat but don't they do that with the hybrid car?
One of the advantages of a hybrid boat compared to a hybrid car is hybrid boats can be designed to harness available solar and wind energy. There are more design restrictions on motor vehicle to fit into a traffic lane and boats can carry the weight of batteries more easily and it can act as useful ballast.
What are the disadvantages?
1: Speed: The power to drive a displacement boat is a cubic function of speed i.e. the power required to drive a displacement boat at 20 knots is 8 times greater than the power to drive it at 10 knots and about 64 times greater than that to drive it at 5 knots. For example a 50 tonne 149 pax hybrid/electric ferry requires 660 kw to achieve speed of 20 knots for commuter services - so power has to come from stored fuel. However for tourism, the max solar power of 20hp will drive the vessel at 6 knots and the average solar power of 10hp will drive the boat at approx 4.5 knots.
Currently the weight of the electric motors and batteries limit series hybrid to applications where constant high speed is not required. If constant high speeds are required conventional diesels or parallel hybrid designs are the most cost effective. Advances in component technologies, particularly batteries and fuel cells replacing gensets will significantly address the speed issue for future ferries.
2: Higher capital cost: The initial capital cost of the new hybrid technology is more than that of the incumbent technology - mainly due to economies of scale. For example the capital cost of a conventional 149 pax cat ferry in the USA is approx US$1.8M compared to a similar hybrid electric vessel which costs approx US$3.4M. See graph in benefits for total life costs  .
What applications are most suitable?
Any 'duty cycle' where constant high speeds are not required.
Applications most suitable are demanding stop/start duty cycles such as urban ferries or applications where periods of intermittent high speeds are combined with intermittent or long periods of slow speed eg tourism, recreation, fishing or defence.
The technology works OK in Australia where there is lots of sun, but what about areas of the world where there is less sun, snow or fogs etc?
Solar panels need light not heat and feed additional power into the hybrid system. For the sake of worldwide comparisons, the calculations for fuel savings (graph above) have been done assuming zero solar and wind input.
Solar/wind energy is a bonus for the marine hybrid electric system.
How would 'solar sailors' go in 6-knot currents, 30-knot winds and rough seas?
The hulls of a vessel are designed for the area of operation. This does not alter hybrid power systems capability, except bigger hulls create greater wash and require more power to go the same speed -ie they lower the efficiency of the power /speed curve. The 149-pax vessel is based on hulls and weight of an ocean going dive catamaran designed by one of our naval architects.
The Hybrid system is designed for the anticipated "duty cycle". If there are areas of speed restrictions or low wash areas the vessels is optimised for such operations. †
The computer can also act as a back up for the skipper notifying him if he deviates off a pre-programmed "blue highway". In such a case, if the captain does not press a button on the screen within predetermined period of time - the vessel will automatically stop.
The wings are engineered to handle 40knots of wind with 300% margin of safety when upright which means about 56 knots. The computer lowers the sails at 33 knots. When lowered they offer zero windage and fit into receptacles in the roof. They can be additionally battened down at their tips. When the vessel is going with or across the wind it adds wind energy to save fossil fuel. When heading into the wind the computer feathers the wings, and the power from the batteries and/or sun and/or gensets drives the aerodynamic superstructure with speed and safety.
If heading against a current the captain drives the vessel as he would normally. If more speed is required the batteries take up the load and as necessary the computer automatically turns on one or two generators.
Can they be built in aluminium or steel?
Yes
Why not just fill up existing ferries with biodiesel?
Economically the boat would still use the same amount of fuel.
Environmentally the reductions in particulates and greenhouse gas emissions would be improved, but NOx (oxides of Nitrogen) emissions would be the same or more than diesel (5).
How does a Hybrid achieve fuel savings?
The best internal combustion engine with multiple moving parts, heat, noise and vibration has a theoretical maximum efficiency of 40% - getting the energy out of the fuel. The optimum efficiency is obtained when the internal combustion engine is run constantly at its optimum revs (such as in the case of the internal combustion engine generators on a series hybrid solar sailor). The efficiency of an internal combustion engine drops significantly when accelerating and decelerating or operating outside its optimum speed such as with a conventional ferry emitting the unburnt fuel as pollution.
Hybrid/electric biodiesel vessels offer the best overall solution based on commercial technology available today. A hybrid/electric biodiesel ferry would use 50% less biodiesel than a conventional ferry running on biodiesel, thereby reducing fuel costs and emissions and offering zero emissions at the wharf, thereby countering the problem of the increased "noxs" from biodiesel.
Won't all this hybrid technology be superseded by the 'hydrogen economy' and fuel cells in a few years?
Hybrid is the bridge to the hydrogen economy. Eventually, the ideal solution for transport is fuel cell/electric cars and vessels - when they become commercially available. "Series" hybrids are immediate platforms for fuel cells. The generators and some of the batteries would be replaced by fuel cells.
Compared to a fuel cell/electric car, a fuel cell electric boat has the advantage of being able to make its own fuel from solar or shore power by 'splitting' water on which it is sitting to make hydrogen (electrolysis) - thereby negating the need for any hydrogen infrastructure. Recreational sailors could loiter or moor in one location while making hydrogen and then power at high speeds to another location using the solar energy (hydrogen) stored over several days.
Solar energy is stored as a proton in hydrogen as opposed to an electron in a battery. Series hybrid vessels are ready for the hydrogen economy and fuel cells when hydrogen storage and fuel cells are commercially available and are approved in the marine industry.
The vessel can sail? - Is it difficult to steer with the wind blowing the sails?
The computer controls the airfoil wings automatically or they can be operated manually. In automatic mode the computer generally gets 3-6 knots of boat speed in a 20-knot wind depending on the wind direction on tourist cruises. Experienced sailors adjusting the wings manually have achieved steady 8-10 knots of boat speed - so we know there is further potential there.
Regarding steering, when the high torque electric motors are running this is not a problem. When sailing only there a different feeling for most ferry skippers. The Sydney Solar Sailor is set up as a "weather helm" ie the boat points up into the wind in gusts which gives safety as it depowers the wings.
The wings are engineered for 40 knots of wind and 300% margin of safety, which equates to about 56knots. The computer automatically stows the wings away when the wind is over 35 knots.
In an emergency the vessel can come to a dead stop in one boat length.
How is the Sydney Solar Sailor vessel performing?
The Sydney Solar Sailor was designed and built 5 years ago as a commercial demonstration of the technology based on the experience gained racing the Marjorie K Hobie-cat prototype.
The Sydney Solar Sailor has been used as a test platform for component technologies and has attracted over $1.5M in grants and sponsorship, as well as winning a string of environment, design, innovation and product acceptability awards.
The Sydney Solar Sailor has been operating commercially for 3 years and profitably in a tough market. The company has recently signed a further 6-year lease with Captain Cook Cruises, Sydney's leading cruise operator. The operator likes the positive passenger feedback and increased patronage but in general wishes for a larger and faster vessel. Captain Cook's CEO, Anthony Howarth, describes it as "performing above expectations" and being a "robust and reliable vessel". Increasing top-end speed has been the focus of Solar Sailor Advanced Technology Watercraft engineers over the last 3 years.
As a result of engineering design changes and advances in components we are now able to offer the next version of the technology - a 149-passenger 20-knot version.
Can these vessels be built locally - what about the Jones Act in the United States?
Yes. We licence the designs and supply the technology to boat builders in the area of operation. The vessels are built to local safety and survey requirements. Local authorities are consulted initially and at all stages of the design and build process. There are no fundamental problems with hybrid diesel/solar electric vessels in obtaining survey.
There is no problem building in the USA.
5) US Environmental Protection Agency. A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions Draft Technical Report. October 2002. http://www.epa.gov/orcdizux/models/analysis/biodsl/p02001.pdf
Top | Back to Hybrid Marine Power
|
