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Oh, what a great idea! Quiet, pollution-free drive for your boat!
Allow me to start by dumping a few buckets of cold water on your enthusiasm... Any motorized vessel need an energy storage compartment to carry with, a gasoline or diesel tank usually. Energy for electric motor can be stored only in a battery bank of sufficient voltage and capacity. The usable energy per weight, however, is absurdly different when it comes to compare both mediums. Modern lithium battery weighting well above 100kg can store roughly the equivalent of energy provided by 1kg of combusted gasoline... As an example, recently developed Torqeedo Deep Blue 40HP electric motor will empty monstrous 12.8 KWh 150kg weighting battery in 30 minutes (!) when running at full throttle, while 40HP gasoline outboard will burn perhaps 1.5 gal of fuel. Yes, it is 4.25kg (not 1kg) of gasoline used to provide the same energy output, simply because internal combustion engines are far less efficient than modern, well designed electric. Still, 150kg (53 US gal.) gasoline tank will allow for 17-18 hours long trip at full throttle, not half an hour. To hammer another nail into e-prop coffin, while re-fueling at nearest marina may take several minutes, the battery re-charging is a several hours long process. Assuming the availability of the off-shore power...
Environmental and other tempting (for some) issues aside, the cost of conversion is horrific. Above mentioned Torqeedo Deep Blue 40HP system, consisting the motor, battery and all necessary peripherals will drain your bank account with $40.000,00 bill easily. And that is without the labour involved. Assuming the price of equivalent 4-stroke EFI 40HP Mercury at roughly $6.000,00, remaining $34.000,00 will cover life-time gasoline supply for next 5 generations of family boaters, perhaps.
Don't bother if you're a power-and-speed junkie. Electric motors may be considered as a desperate solution for avid boaters on waters where gasoline or diesel burning is strictly prohibited. But it will not reward you with a thrill of riding the boat powered by 350HP Merc Verado. Sure you can build an electric boat making 100 knots, but for 10 minutes perhaps. The famous Tesla electric car will do smokin' acceleration and doughnuts as well, yet the remaining "normal" driving range may not impress your female passenger that much.
Said that, the idea of electric propulsion may shine when some special projects are in focus. The power requirement rises eightfold with speed, therefore backing the throttle to - say - half will result in dramatic increase of distance to go on single battery charge. This is particularly true with replacement vessels. Unconventional designs may allow for installation of PV (photovoltaic) systems, supporting the current drawn from battery. In such scenario it is a matter of balancing the sun-harvesting area of solar panels before the vessel became clumsy, impractical, ugly or even vunerable. Difficult task, indeed, since solar system will compromise the look, functionality or safety of an vessel. Recent developments in lightweight, flexible solar panels (i.e. Solbian) may provide much more appealing solutions. The same comes with progress in high capacity lithium battery technology (). Some kinds of boats are just asking for electric propulsion. Narrowboats, houseboats, barges and other vessels popular on some inland waterways are particularly suited due to the low power requirement and available space for supporting solar system installation. Some types of antique wooden boats and replicas (i.e. launch) may also benefit from electric drive. Water taxi - usually a barge with seats and a huge roof above - can carry sufficient amount of solar panels.
When considering PV system to support your battery bank, any current supplied with charging voltage will help. As a starting point for more radical designs, however, consider 50% worth solar colaboration into total draw. The Torqeedo Cruise 2.0 outboard - for example - will need 1kW of power at half throttle, resulting in equivalent propulsion of 2.5HP gasoline motor. With average size pontoon boat it may render reasonable 6km/hr speed on calm water. Now - back to a PV array and battery colaboration in this example - be aware that targeted 500W solar "injection" is measured at charger terminals. That means the total value of array Pmax (specified maximum power at certain, theorethical, never achievable conditions) must be at least twice this much, assuming the involvement of efficient MPPT type charging controller. With 1000W of Pmax worthy solar system and fully charged 200Ah battery this boat may cruise as long as the sun is shining and still have enough energy left to come home after twilight.
All advantages and disadvantages of electric propulsion aside - be aware that it will not deliver when serious power is needed in emergency situation. For this reason one should consider electric motor as alternative propulsion, replacing main fossil-fueled engine when Mother Nature politely agree (known as "parallel hybrid"). That's the key for safe, enjoyable e-boating.
However, the performance of my particular system (mediocre by all means to any power boater) is determined by the state of battery technology in 2015. Some optimistic predictions assumes tenfold increase of energy storage density of lithium-based batteries by the end of next decade. Hi-power outlets may be available on every marina, making battery charging process similar to fueling. But this is another story, not related to sun-harvesting issues discussed here...
Allow me to start by dumping a few buckets of cold water on your enthusiasm... Any motorized vessel need an energy storage compartment to carry with, a gasoline or diesel tank usually. Energy for electric motor can be stored only in a battery bank of sufficient voltage and capacity. The usable energy per weight, however, is absurdly different when it comes to compare both mediums. Modern lithium battery weighting well above 100kg can store roughly the equivalent of energy provided by 1kg of combusted gasoline... As an example, recently developed Torqeedo Deep Blue 40HP electric motor will empty monstrous 12.8 KWh 150kg weighting battery in 30 minutes (!) when running at full throttle, while 40HP gasoline outboard will burn perhaps 1.5 gal of fuel. Yes, it is 4.25kg (not 1kg) of gasoline used to provide the same energy output, simply because internal combustion engines are far less efficient than modern, well designed electric. Still, 150kg (53 US gal.) gasoline tank will allow for 17-18 hours long trip at full throttle, not half an hour. To hammer another nail into e-prop coffin, while re-fueling at nearest marina may take several minutes, the battery re-charging is a several hours long process. Assuming the availability of the off-shore power...
Environmental and other tempting (for some) issues aside, the cost of conversion is horrific. Above mentioned Torqeedo Deep Blue 40HP system, consisting the motor, battery and all necessary peripherals will drain your bank account with $40.000,00 bill easily. And that is without the labour involved. Assuming the price of equivalent 4-stroke EFI 40HP Mercury at roughly $6.000,00, remaining $34.000,00 will cover life-time gasoline supply for next 5 generations of family boaters, perhaps.
Don't bother if you're a power-and-speed junkie. Electric motors may be considered as a desperate solution for avid boaters on waters where gasoline or diesel burning is strictly prohibited. But it will not reward you with a thrill of riding the boat powered by 350HP Merc Verado. Sure you can build an electric boat making 100 knots, but for 10 minutes perhaps. The famous Tesla electric car will do smokin' acceleration and doughnuts as well, yet the remaining "normal" driving range may not impress your female passenger that much.
Said that, the idea of electric propulsion may shine when some special projects are in focus. The power requirement rises eightfold with speed, therefore backing the throttle to - say - half will result in dramatic increase of distance to go on single battery charge. This is particularly true with replacement vessels. Unconventional designs may allow for installation of PV (photovoltaic) systems, supporting the current drawn from battery. In such scenario it is a matter of balancing the sun-harvesting area of solar panels before the vessel became clumsy, impractical, ugly or even vunerable. Difficult task, indeed, since solar system will compromise the look, functionality or safety of an vessel. Recent developments in lightweight, flexible solar panels (i.e. Solbian) may provide much more appealing solutions. The same comes with progress in high capacity lithium battery technology (). Some kinds of boats are just asking for electric propulsion. Narrowboats, houseboats, barges and other vessels popular on some inland waterways are particularly suited due to the low power requirement and available space for supporting solar system installation. Some types of antique wooden boats and replicas (i.e. launch) may also benefit from electric drive. Water taxi - usually a barge with seats and a huge roof above - can carry sufficient amount of solar panels.
When considering PV system to support your battery bank, any current supplied with charging voltage will help. As a starting point for more radical designs, however, consider 50% worth solar colaboration into total draw. The Torqeedo Cruise 2.0 outboard - for example - will need 1kW of power at half throttle, resulting in equivalent propulsion of 2.5HP gasoline motor. With average size pontoon boat it may render reasonable 6km/hr speed on calm water. Now - back to a PV array and battery colaboration in this example - be aware that targeted 500W solar "injection" is measured at charger terminals. That means the total value of array Pmax (specified maximum power at certain, theorethical, never achievable conditions) must be at least twice this much, assuming the involvement of efficient MPPT type charging controller. With 1000W of Pmax worthy solar system and fully charged 200Ah battery this boat may cruise as long as the sun is shining and still have enough energy left to come home after twilight.
All advantages and disadvantages of electric propulsion aside - be aware that it will not deliver when serious power is needed in emergency situation. For this reason one should consider electric motor as alternative propulsion, replacing main fossil-fueled engine when Mother Nature politely agree (known as "parallel hybrid"). That's the key for safe, enjoyable e-boating.
However, the performance of my particular system (mediocre by all means to any power boater) is determined by the state of battery technology in 2015. Some optimistic predictions assumes tenfold increase of energy storage density of lithium-based batteries by the end of next decade. Hi-power outlets may be available on every marina, making battery charging process similar to fueling. But this is another story, not related to sun-harvesting issues discussed here...
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