Electricity?
07-20-2011, 02:40 PM
#5
Platinum Member
Platinum Member
Seriously, we are so far away from practical electric boating we may as well think of its progress as being in the stone age. Aside from a handful of electric tour boats that you may see around some parts of the country that putz around at 5mph for less than an hour, it'll never be mainstream - especially in performance applications - for a very long time.
The practical limitations:
I'll use my boat as an example because I know the numbers off the top of my head.
2x500hp = 1000hp
180 gallons fuel capacity.
1 gal of gasoline has a potential energy capacity of 125,000 BTU's, which = about 36,600 watt-hours.
So, I can carry 6,048,000 watt-hours of energy.
It weighs about 1080 lbs.
So this is about 5600 watt-hours/LB energy density.
The average stock modern reciprocating 4-stroke internal combustion engine has an efficiency of approximately 20%.
1HP = 745.7 watts
Therefore, at WOT making 1,000HP at 20% efficiency, I'm consuming about 3,725,000 watts per hour and with 180 gallons aboard I can keep it up for about 1.62 hours.
Let's compare that to electro-mechanical physics.
The best Lithium-Ion batteries have an energy density of about 120 watt-hours per LB. Compare that to gasoline's 5600 watt-hours per pound.
I would need 50,400 pounds of batteries to do what I do now. Unfortunately my boat would have sunk and my bravos would have blown up carrying that much weight.
Lead-Acid batteries are far worse. They have an average energy density of 40 watt-hours per pound.
To make the same 1,000 HP for 1.6hours, I would need 151,000 pounds of lead acid batteries.
This is the same reason why Locomotives and cruise ships that are propelled by electric motors carry with them a diesel engine, not batteries.
The advantage is that electric motors are 90% efficient and they can make 100% torque virtually throughout their entire rpm range, thus it makes more sense to use them for the actual locomotion. The diesel engine does nothing other than turn a generator which can be tuned so that the diesel is running at it's peak torque and efficiency at all times versus varying its rpms which yields a more efficient use of its fuel.
Applying the same to a boat in our size range would still be far too heavy for the vast majority of boats and you can forget about performance.
A fully dressed 502 BBC weights what? 1,000#. So 1HP per Pound.
A 500HP electric motor would weight 3,500Lbs. I need two of them. In addition I'd need a 1,250 HP diesel engine (power in * efficiency = power out) and an equivalent generator. We're looking at a 20,000 LB powertrane plus fuel.
The practical limitations:
I'll use my boat as an example because I know the numbers off the top of my head.
2x500hp = 1000hp
180 gallons fuel capacity.
1 gal of gasoline has a potential energy capacity of 125,000 BTU's, which = about 36,600 watt-hours.
So, I can carry 6,048,000 watt-hours of energy.
It weighs about 1080 lbs.
So this is about 5600 watt-hours/LB energy density.
The average stock modern reciprocating 4-stroke internal combustion engine has an efficiency of approximately 20%.
1HP = 745.7 watts
Therefore, at WOT making 1,000HP at 20% efficiency, I'm consuming about 3,725,000 watts per hour and with 180 gallons aboard I can keep it up for about 1.62 hours.
Let's compare that to electro-mechanical physics.
The best Lithium-Ion batteries have an energy density of about 120 watt-hours per LB. Compare that to gasoline's 5600 watt-hours per pound.
I would need 50,400 pounds of batteries to do what I do now. Unfortunately my boat would have sunk and my bravos would have blown up carrying that much weight.
Lead-Acid batteries are far worse. They have an average energy density of 40 watt-hours per pound.
To make the same 1,000 HP for 1.6hours, I would need 151,000 pounds of lead acid batteries.
This is the same reason why Locomotives and cruise ships that are propelled by electric motors carry with them a diesel engine, not batteries.
The advantage is that electric motors are 90% efficient and they can make 100% torque virtually throughout their entire rpm range, thus it makes more sense to use them for the actual locomotion. The diesel engine does nothing other than turn a generator which can be tuned so that the diesel is running at it's peak torque and efficiency at all times versus varying its rpms which yields a more efficient use of its fuel.
Applying the same to a boat in our size range would still be far too heavy for the vast majority of boats and you can forget about performance.
A fully dressed 502 BBC weights what? 1,000#. So 1HP per Pound.
A 500HP electric motor would weight 3,500Lbs. I need two of them. In addition I'd need a 1,250 HP diesel engine (power in * efficiency = power out) and an equivalent generator. We're looking at a 20,000 LB powertrane plus fuel.
Last edited by CigDaze; 07-20-2011 at 03:10 PM.
07-20-2011, 08:18 PM
#6
Seriously, we are so far away from practical electric boating we may as well think of its progress as being in the stone age. Aside from a handful of electric tour boats that you may see around some parts of the country that putz around at 5mph for less than an hour, it'll never be mainstream - especially in performance applications - for a very long time.
The practical limitations:
I'll use my boat as an example because I know the numbers off the top of my head.
2x500hp = 1000hp
180 gallons fuel capacity.
1 gal of gasoline has a potential energy capacity of 125,000 BTU's, which = about 36,600 watt-hours.
So, I can carry 6,048,000 watt-hours of energy.
It weighs about 1080 lbs.
So this is about 5600 watt-hours/LB energy density.
The average stock modern reciprocating 4-stroke internal combustion engine has an efficiency of approximately 20%.
1HP = 745.7 watts
Therefore, at WOT making 1,000HP at 20% efficiency, I'm consuming about 3,725,000 watts per hour and with 180 gallons aboard I can keep it up for about 1.62 hours.
Let's compare that to electro-mechanical physics.
The best Lithium-Ion batteries have an energy density of about 120 watt-hours per LB. Compare that to gasoline's 5600 watt-hours per pound.
I would need 50,400 pounds of batteries to do what I do now. Unfortunately my boat would have sunk and my bravos would have blown up carrying that much weight.
Lead-Acid batteries are far worse. They have an average energy density of 40 watt-hours per pound.
To make the same 1,000 HP for 1.6hours, I would need 151,000 pounds of lead acid batteries.
This is the same reason why Locomotives and cruise ships that are propelled by electric motors carry with them a diesel engine, not batteries.
The advantage is that electric motors are 90% efficient and they can make 100% torque virtually throughout their entire rpm range, thus it makes more sense to use them for the actual locomotion. The diesel engine does nothing other than turn a generator which can be tuned so that the diesel is running at it's peak torque and efficiency at all times versus varying its rpms which yields a more efficient use of its fuel.
Applying the same to a boat in our size range would still be far too heavy for the vast majority of boats and you can forget about performance.
A fully dressed 502 BBC weights what? 1,000#. So 1HP per Pound.
A 500HP electric motor would weight 3,500Lbs. I need two of them. In addition I'd need a 1,250 HP diesel engine (power in * efficiency = power out) and an equivalent generator. We're looking at a 20,000 LB powertrane plus fuel.
The practical limitations:
I'll use my boat as an example because I know the numbers off the top of my head.
2x500hp = 1000hp
180 gallons fuel capacity.
1 gal of gasoline has a potential energy capacity of 125,000 BTU's, which = about 36,600 watt-hours.
So, I can carry 6,048,000 watt-hours of energy.
It weighs about 1080 lbs.
So this is about 5600 watt-hours/LB energy density.
The average stock modern reciprocating 4-stroke internal combustion engine has an efficiency of approximately 20%.
1HP = 745.7 watts
Therefore, at WOT making 1,000HP at 20% efficiency, I'm consuming about 3,725,000 watts per hour and with 180 gallons aboard I can keep it up for about 1.62 hours.
Let's compare that to electro-mechanical physics.
The best Lithium-Ion batteries have an energy density of about 120 watt-hours per LB. Compare that to gasoline's 5600 watt-hours per pound.
I would need 50,400 pounds of batteries to do what I do now. Unfortunately my boat would have sunk and my bravos would have blown up carrying that much weight.
Lead-Acid batteries are far worse. They have an average energy density of 40 watt-hours per pound.
To make the same 1,000 HP for 1.6hours, I would need 151,000 pounds of lead acid batteries.
This is the same reason why Locomotives and cruise ships that are propelled by electric motors carry with them a diesel engine, not batteries.
The advantage is that electric motors are 90% efficient and they can make 100% torque virtually throughout their entire rpm range, thus it makes more sense to use them for the actual locomotion. The diesel engine does nothing other than turn a generator which can be tuned so that the diesel is running at it's peak torque and efficiency at all times versus varying its rpms which yields a more efficient use of its fuel.
Applying the same to a boat in our size range would still be far too heavy for the vast majority of boats and you can forget about performance.
A fully dressed 502 BBC weights what? 1,000#. So 1HP per Pound.
A 500HP electric motor would weight 3,500Lbs. I need two of them. In addition I'd need a 1,250 HP diesel engine (power in * efficiency = power out) and an equivalent generator. We're looking at a 20,000 LB powertrane plus fuel.
Dumb bastage.............get an education
07-20-2011, 08:25 PM
#7
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Location: Sarasota, Fl
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Big electric sport boats are probably far down the road. Most people probably don't spend a huge part of their income on fuel for their boat, electric cars are going to be all the rage in a few years, but thats just my prediction. YMMV
07-21-2011, 12:18 PM
#10
Platinum Member
Platinum Member
And if someone does develop in my lifetime some unobtainium-ion battery that's up to the task and a 1,000 HP electric motor that weighs less than 2,000 LB, It would still be a resounding no.
