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%  

fredag 19 juli 2013

Regenerative breaking at sea

The term regenerative breaking, regen, is widely used in the car industry and the idea is to turn kinetic energy into electricity. A car that speeds downhill can use its electric motor as a generator and convert the cars movement to electric energy that is stored in the battery.

Sadly we don’t get any down slopes at sea. The only way to do regen at sea is to have a sail that powers the boat quick enough to make the propeller spin. If you don’t have a sail and you lack the ability to charge from the grid you can, as a mentioned in my last post, use the energy from wind, sun or petrol to charge off-grid.
Another, and less complex, alternative to charging the battery is to use the electric motor in the boat as a generator when the boat is being propelled by the combustion engine. This way I can, by the flick of a switch, charge my batteries with the same amount of power as when connected to the grid.  

If, for example, I am out fishing and I noticed that my batteries are running low I can charge while driving back home using the combustion engine. This regen functionality guaranties in an easy way that I won't run out of energy in my battery.

lördag 13 juli 2013

Off-grid charging

Finally we are here! We arrived late last night after a 1 hour and 45 minutes drive from Söderöra. Everything went smooth as a whistle. The boat was packed with supplies but there was only a small increase in energy used during the trip.


Since the trip is one hour longer than what my total battery capacity would count for I had to use the diesel. Another thing to keep in mind is that there is no electric grid here. So how do we charge?

I gave the charging issue some thought this winter and I came up with the following solutions:

A petrol/gasol generator would probably be the quickest way to charge. The downside is noise, local pollution and complexity. I don’t like the idea of burning fuel in order to create electricity.


By using solar panels electricity can be harvest from the sunlight. No moving parts and no noice. The downside is the efficiency of the panels and the dependency of cloud free weather. To get a usable charge current I would have to use about 3-4 square meters of cells, given that there is no clouds.

Using the wind to harvest electricity is common in these areas. Modern wind generators are efficient with a moderate wind force demand. What you need is a generator, small tower and an extension cord.
And the winner is…. The wind generator! Given that we normally have a couple of days with winds around 8-10ms I should be able to get some energy into my batteries. Since I run a 48 volt system I need a 48 volt wind generator. Fortunately Southwest Windpower makes a small, 120cm diameter, generator with an integrated controller. The controller makes sure that the batteries receive the correct voltage while charging.

How long will it take to charge the pack? Well that depends on how strong the wind is. The generator can deliver max 8 Amps. Let's use half of that rating in the equation. My battery pack has a capacity of 60 Amp hours and I used half of that capacity to get to the island. That means that I will have to generate 30 Amp hours in order to have a full pack again. 30 divided by 4 equals 7,5. In 7,5 hours the battery would be fully charged if the generator delivers 4 Amps continuously for 7,5 hours. In real life the numbers will differ but as long as there is wind the generator will run 24 hours a day. 
Right now the battery pack is a 50,6% charge and we have a 5-6m/s wind that should be picking up during the day. I will get back with the charging result tonight, stay tuned!

The wind generator has been working since 06:00 this morning. The wind reached its peak, 14 m/s, around 14:00. As you all know we started at 50,6% charge and during the course of the day the state of charge has increased to 84,0% (22:30).

During peak hours the generator generated as much as 395 watts (7,4 Amps * 53,5 volts). 

During the day the generator has been adding almost 1,5 Kwh to the battery pack. A battery pack full of wind power, does that mean that I'm sailing?
Have a nice vacation, I know I will.
See you soon.

tisdag 4 juni 2013

Welcome to Hy-life!
Discussions about hybrid cars and how we use them has been frequently debated in Swedish media the last year. There are numerous blogs and articles were users as well as producer’s debate fuel consumption, mileage and environmental impact. The hybrid car is no longer only for early adopters, it is now a part of everyday life.

I have created this blog in order to share some light on another market that is extremely big in Sweden, leisure boating. Sweden has more than 900 000 leisure boats and an archipelago that consists of over 30 000 islands.

Innovation in the marine market has in no way followed the pace of the car industry. In order to speed up innovation I started a journey which goal was to create a marine hybrid drivetrain for my boat Linnea.
Linnea is based on a classic Swedish fishing boat design used in our archipelago for ages. The hull is a displacement hull, and the rule of thumb is that the speed of the boat is equivalent to its length in the water, this is normally called hull speed. Linnea is about 5 meters measured at the waterline so five knots is her hull speed.
The hybrid drivetrain consists of two motors, one electric motor and one traditional combustion engine. The electric motor is the heart of my drivetrain and it is also responsible for the basic functionality that we need at sea. Why use a combustion engine, why not go all electric? The reason that I choose a hybrid is the price and energy density of today’s batteries. The combustion engine acts as a range-extender that allows us to fully enjoy our time at sea.

The size of the battery pack determines how long we can run the boat using electricity. When we want to go further than the battery pack allows we use the combustion engine.

The electric motor has many benefits compared to the combustion engine, one is the ability to act as a generator. This enables us, by the push of a button, to charge the battery pack while running the combustion engine. This secures that there is always energy available for docking the boat when we reach our destination.

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