We are adding a tracker that hopefully will work. It has a solar sensor that works by measuring the sunlight intensity or shade on 4 solar sensors mounted around an elevated area.
The array can be parked in the horizontal position with respect to the boat. A further advancement will be horizontal tracking, in which case the array will have less windage than one that is mounted horizontally with respect to the boat.
Slip rings and brushes are not necessary. We first considered inverting a wind generator base or yolk and using the brushes. But after careful consideration we determined that the power, sensor and elevator actuator wires could be run down the middle of the tube. A counter from center position might be a nice option to have to prevent the wire from winding up too much, but a careful operator could prevent this. A simple preventer could be made by attaching a bungy cord to the mast and to the boat that would make it obvious if you had made more than one 360 degree turn.
Yes it was a huge project. I first laid down the foundation for the array by glassing a piece of 3/4 ply to the base of the aft locker 4 years ago! Since then I mulled it over many times before coming to the current design. We were very happy that it worked with only one small modification from the initial design - a second brace with a bearing 16 inches up from the floor - to insure it was capable of high wind loading.
The array is designed to survive a complete knock down and to be capable of wind loading up to 100 miles per hour wind. At that wind speed, the array would become the least of my problems, so i don't worry about it. Its also capable of being wind loaded from below so the array cannot lift upwards.
It does work very well. Being able to make 3 knots under solar power alone is a huge advantage. Think about crossing the doldrums. Also, most times there is a slight wind and dead calms are very rare. Having the power of the array on the propeller while sailing on a broad reach or upwind enables a sailor to sail in ultra low wind speeds - the greatest advantage of an electric boat! Most times this translates into a 2 knot increase in boat speed while sailing. 3 knots becomes 5 knots under solar / wind hybrid.
We used a windlass gear motor to turn the mast, chain driven with reduction. We are still working on the controls for the motor to slow it down. We are currently employing a resistor. Our next model will feature a slower gear motor and perhaps even a controller which would allow for variable speeds of turn. The worm gear on the gear motor prevents the mast from turning under wind loads, much the same as your car's stearing box does not turn the steering wheel when you hit a pothole. The design of this array should be very low maintenance. About the only thing necessary is a little oil on the stainless steel chain once in a while.
All in all, it is a great improvement to the boat. I have been able to unplug the boat from the dock for the last month. That is such a great feeling to cut the cord and know that you are energy independent. This joins the toolboat
http://www.toolboat.com which has been completely energy independent for 5 years from solar power alone.
This array will not be expensive with respect to its total output capability. Its really important to me to make cost effective solutions for boats. It is the only way we will ever see wide spread adoption of electric power for sailboats.
I believe this array makes ocean cruising possible but only time will tell. In the meantime, we will be doing extensive testing cruising around Santa Barbara's Channel Islands, and will report back to you the results.
James
On Oct 5, 2011, at 6:54 AM, stmbtwle wrote:
There's no question in my mind that a tracking array will generate more power than a horizontal array, especially if the array can track in both azimuth and altitude. However on a BOAT this will present some problems. The array will have to track in azimuth indefinitely as the boat can turn in any direction relative to the sun, so slip rings and brushes are going to be required that can handle the full output of the array. The "sail" area of a large array in the near-vertical position may be detrimental to the boat's handling and performance. The wind load and G-forces encountered in rough weather may dictate a more-robust installation than would normally be the case. Then there's the maintenance of all the moving parts, sensors, and drives required to make it work in a hostile environment.
Not saying it can't be done but engineering a full-tracking array for marine use is no small project and it will NOT be cheap. After much research and experimentation I finally decided that it was simpler and probably cheaper to simply have a larger array, mounted horizontally. Solar panels are getting more affordable all the time.
Willie
--- In electricboats@yahoogroups.com, "matwete@comcast.net" <matwete@...> wrote:
>
> I get the point. Being the last hour before sunset, you also benefit from multiple suns off the water making a pure vertical orientation near optimal.
>
>
> T-Mobile. America's First Nationwide 4G Network
>
> ----- Reply message -----
> From: "James Lambden" <james@...>
> To: <electricboats@yahoogroups.com>
> Subject: [Electric Boats] Marine Solar Array makes 3 knots
> Date: Sun, Oct 2, 2011 10:42 pm
>
>
> Tracking array numbers work on averages. The 10 X number was an instant change from horizontal to directly towards the sun. Many times on a boat a horizontally mounted array will be aimed away from the sun, due to the boat's heel.
>
> By being focused directly on the sun, the difference is enormous. Considering being able to do this continuously, as you sail, and you can start seeing the potential benefits.
>
> James
>
>
>
>
>
>
> On Oct 2, 2011, at 10:32 PM, Femm wrote:
>
> > I've had people ask me about sizing a solar array for here in the northwest/Puget Sound area and I tell people to figure they are only going to get 50 to 60% of their rated output up here most of the time.
> >
> > I would like to see a real world test to prove that 10X number! I would be more inclined to think it's more like 10 to 12% real world.
> >
> > femm
> >
> > --- On Sun, 10/2/11, Myles Twete <matwete@...> wrote:
> >
> > James noted:
> >
> > "Tracker Expected to be released soon. By Focusing on the sun, power developed is as high as 10 times more than if panels are mounted horizontally"
> >
> >
> >
> > Really…10x?
> >
> >
> >
> > Would you believe 18%: http://www.civicsolar.com/resource/effect-array-tilt-angle-energy-output
> >
> >
> >
> > Array Tilt Angle
> > (degrees)
> >
> > Phoenix, AZ (33 North)
> >
> > Portland, OR (45 North)
> >
> > Annual Production
> > (kWh)
> >
> > Delta
> > (%)
> >
> > Annual Production
> > (kWh)
> >
>
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