måndag 5 augusti 2013

Real life statistics

I’m back to work again after a wonderful vacation. The boat and drivetrain has delivered beyond my expectations. None of the problems I had with prototype one has occurred on prototype two and it has been 99% hassle-free boating.
I have been running the numbers on electric vs. diesel consumption during my four weeks of vacation. Most trips have been around 30-60 minutes. The longest one was three and a half hour one way, about 16 nautical miles.

In order to compare apples with apples we first need to determine the efficiency of the diesel engine and electric motor. My diesel is a simple two-valve engine and I would say that the efficiency is 30%. The electric motor and motor controller has a combined efficiency of about 80%.

Some facts about diesel and my diesel engine:
Energy density: 9,7kwh/l
Diesel engine efficiency: 30%
I used 20 liters of diesel during my vacation. 20 liters of diesel contains 194kwh and with a 30% efficiency, 58,2kwh is used to propel the boat.

My battery monitor collects and stores the total amount of energy, ah, flowing to and from the traction pack. After four weeks I have used 967ah@55 volt (53kwh). After removing 20% we end up using 42,5kwh of electric power to propel the boat.

42,5kwh of electricity equals about 15 liters of diesel (remember the low efficiency of the diesel engine)
If I had only used a diesel engine I would have consumed 35 liters of diesel during my vacation. Thanks to the hybrid drivetrain that figure is now 20 liters. Bottom line, the hybrid lowers my fuel consumption with 42,1%