Are Fully Electric Boats The Way of The Future?
With more and more cars on the road comprising of Electric Vehicles (EVs) I was curious how electrification was going for the boating industry. There are quite a few manufactures getting their toes wet (pun intended) in the Electric Boat (EB) market. How realistic is it to assume that boats will follow the same path as cars when it comes to electrification? Generally speaking, the energy required to operate a boat is far greater than to operate a car. This is because boats, among other factors, operate on the water where they generate much more drag against their hulls compared to the rolling resistance that tires generate on the road. I am excluding large ships from this discussion, which are actually quite fuel efficient, and focusing on the recreational boat market. So, let’s take a look at some Pros and Cons to EBs.
· Environmentally friendly
· No fuel cost or engine maintenance & no emissions generated
· Reduced vibrations & elimination of engine noise
· Low power electric motor weigh less than equivalent internal combustion engine (ICE)
· Energy density of batteries is much less than gasoline or diesel
· Reduced range for same weight in fuel (gas vs batteries)
· Lower speeds required for energy conservation
· Cost of EBs are higher than their fossil fuel counter parts
One of the biggest draw backs for EBs is the fact gasoline is 50 times more energy dense than lithium-ion batteries. This means the energy contained in 1 Kilogram (kg) of gasoline is equivalent to the energy contained in 50 kgs of lithium batteries! Of course, electric motors are much more efficient than ICEs so ratio isn’t quite that large. In order to keep weight and prices down for EBs manufactures are expecting consumers to change their boating habits. “We think there will be a shift in attitude from owners of small sportsboats from travelling at 30-40 knots to cruising at 15-25 knots,” a boat manufacture said in a Motorboat & Yachting article. I don’t know if this a realistic assumption, but the article also discusses using hydrofoils to reduce drag forces buy lifting the hull of the boat out of the water. Just for fun I wanted to do a quick calculation to see how much weight in batteries it would take for a 200 horsepower (hp) electric motorboat to cruise at wide open throttle for 4 hours.
With a 200 hp = 150 kW motor and boating for 4 hours = 600 kWh of storage capacity required. Assuming that lithium-ion batteries weigh about 6 kg per kWh, then the battery packs would weigh 3600 kg = 7936 lbs. That’s a lot of weight to haul around for a small motorboat and may even weigh more than the boat itself! You could expect to burn about 80 gallons of gasoline when running a motorboat with an ICE under the same conditions.
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