Active solar tracking

[RAD88]

Solar tracking

I'm thinking that a voltage sensor on a pivot motor might be able to read the highest output of the solar panel. Turn the panel to the highest output and stop. Then you would have to figure out how to stop the pivot motor when it reads the highest output of the panel. And how and when to re engage the pivot motor so the sensor can read the output and track the sun. I'm not an electrical engineer but it does seem workable. You would end up using power to turn the panel but gain back more when it is properly set to the sun. What would happen on a cloudy day would have to be worked out. Just an idea.

 

[RAD88]

Re: Solar tracking

A thermal collector is a great idea if you could run a water line to the deck, thru a solar collector and back down to an insulated holding tank. Add a solar triggered pump to send water to the collector only when its sunny and you might have a near constant supply of warm to hot water. Been thinking of this for a while. Any thoughts?

 

[RAD88]

Re: Solar tracking

Wow - just had a chance to read all the previous posts - you guys a way ahead of me on this.

 

[Stu Jackson]

Bill's right, KISS.

All solar is LOCAL.

 

[sea_casper]

Children of the digital age!!!!!!

Go analog and you have more sail time. And is that not the goal????

As a retired Electrical Engineer skilled in analog and digital techniques, my approach would be to buy a 200-240 watt panel ($0.88/watt) mount it horizontally and take the 30% inefficiency in positioning.

No tracking just a fixed mount, KISS.

 

[Bill Roosa]

Hey Rad88
If you had a simple thermistor on the panel and one on the storage tank and use an opamp to compare them you could use that information to turn on a small pump.
Since my solution to aiming the panels allows the whole unit to turn as many times as needed the hoses would get "wound up". they have couplings that allow one side to rotate and the other to be stationary but they are kinda pricy.
I was thinking of just taping into the existing hot water tank engine tubing and disconnecting the engine. If you leave it connected to the engine it gets pressurized and a big box with two big sides is going to start to bulge with those kinds of pressure on it. Disconnect the engine and you can control the max pressure with an expansion tank.

 

[Bob J.]

You guys are attacking the problem the hard way round. I really don't care where I am on the globe, I don't care which way the boat is headed either. All I really have to know is the following:
Is the panel aimed east or west of the sun
is the panel aimed above or below the sun.

Not trying to be negative here but I was serious when I asked wouldn't it get dizzy tracking the sun on a boat? I only ask because I've done a fair amount of solar since the 70's. A boat is not a stable platform, it's constantly in motion. I see a tracking device getting alot of wear & tear on it.

The thermal solar aspect sounds good on paper. I had a sample solar panel that would been a perfect for this application, then I thought about it.

How do you deal with stagnation? The storage tanks on boats are small & would charge rather quickly. If you had a closed system, you would need a dump zone.

If you had a drain down system, you'd be dumping the panel & the loop. Where would you dump it, the bilge? A drain down system could also put a dent into a boat's tank water capacity.

There's also the control system that would be neccesary for a themal solar application.
Seems rather like a rather complicated scenario to me for "free" hot water.

 

[Bill Roosa]

I'm hip sea-casper
Unfortunately I don't want to hear the boat motor run or do the extra maintenance from running it with almost no load....... AND the Admiral and I have this thing about keeping the food cold.
Also if I mounted the big panels on the bimini like other have done I can't look at the sails through the nice overhead window that I spent so much time installing.

It came up earlier in the post and I did some back of the envelope calculations and for a boat at 38 deg N Lat on the equinox you are loosing 51% of your daily output with a flat panel. My boat is not THAT big that I can afford to take a 50% hit and use bigger panels to make up the difference!

losses = 1-cos(latitude - panel inclination)*sin(solar azimuth)
I did not have my calculus book handy so I did a spreadsheet with 1 degree increments of solar azimuth and then summed the results.

 

[sea_casper]

I'm hip sea-casper
Unfortunately I don't want to hear the boat motor run or do the extra maintenance from running it with almost no load....... AND the Admiral and I have this thing about keeping the food cold.
Also if I mounted the big panels on the bimini like other have done I can't look at the sails through the nice overhead window that I spent so much time installing.

It came up earlier in the post and I did some back of the envelope calculations and for a boat at 38 deg N Lat on the equinox you are loosing 51% of your daily output with a flat panel. My boat is not THAT big that I can afford to take a 50% hit and use bigger panels to make up the difference!

You can mount the panel aft of your window, you can mount a wind generator to generate power while sailing, the new ones are quiet, I use a Honda 2000 to charge ,for a couple of hours each day, I have 300+ ah of battery capacity, I would suggest looking at a small genset for your boat as another more expensive option, but the 200 +w panels are the most bang for the buck.

I plan on adding one over my davits or over the aft bimini, aft of the window in mine.

 

[Bill Roosa]

Hey misfits
Something to consider. if you can get the panel to within 10 deg of directly pointed at the sun you are at 90 %. So instead of trying for that last 10% (and having the motors run almost constantly) you "de-tune" the control circuit so there is a bigger null when pointed at the sun. Heel angles are usually not changing by more than 10 degrees a lot so this would work while sailing is my thinking. Swinging on anchor probably needs a different setting but that is pretty easy to implement with just a switch to change the resistor values the opamp sees

On the thermal, I quite frankly have not spent a lot of time thinking through all the details and your insights are greatly appreciated. You could always have a heat dump circuit that just ran the coolant through a loop that heated the ocean water. once the hot water tank came up to temp. That could double as a electric panel cooler....... hummmmm. it does seem to be getting complicated

 

[Bill Roosa]

The window had to be kinda long fore aft wise as the wife is short and I'm tall. It is just not an option for us.
We absolutely hate disturbing the peace and solitude of sailing so a gas genset would be a last resort. I'd motor sail first.
I plan on installing a wind genset on top of the pole that holds the panels if we find we need it.

 

[Bob J.]

You could always have a heat dump circuit that just ran the coolant through a loop that heated the ocean water. once the hot water tank came up to temp.

That's a pretty good idea. You'd have to come up w/ a control system that would allow that to happen which is very easy. Problem comes down to another parisitic load on the boat to run the control system.

I hear what you're saying about being dialed into the 90% on the photovoltaics. Just not sure how practical it is on a boat.

This is how great things are created. If the Wright brothers listened to the nay sayers....

 

[Sumner]

The window had to be kinda long fore aft wise as the wife is short and I'm tall......

I'm 6-1 and Ruth is 5-2. Our window....

..... and the ...

....frame (for 480 watts) with the opening for the window in the area ahead of the backstay.

Have you got the frame figured out?

Sum

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[Bill Roosa]

2 axis solar tracker

Still working on the frame as some of the motor drive design is driving that and the recent introduction of a heat collecting panel underneath the solar.......
Nice frame for the bimini BTW. Our geometry is a little different as the boom comes about 1/2 way back and we only have the two bails

 

[Sumner]

.... Our geometry is a little different as .....

....the boom comes about 1/2 way back and we only have the two bails

You have a beautiful boat there and I like the dinghy. You made it?

One advantage we have is that our boat is 'under sailed' so the boom doesn't come back at far as on most boats the same size. I don't know if this would help you, maybe someone, but Solar Blvd has some made in Canada 260 watt 12 volt panels on their site now......

http://mx2.radiant.net/Session/18390-mMgXwGMlq5sCZ9HmtDoy/Message.wssp?Mailbox=INBOX&MSG=5225

We could of put 520 watts in less space than the 480 we have with six 80 watt panels. I kind of like the redundancy of more panels, but just mounting 2 would be an easier install and more efficient space wise. Good price on the panels, but they would probably have to go truck. Even with truck freight they might be a good deal since they would cut down on the supporting frame expense and labor there.

Still working on the frame as some of the motor drive design is driving that and the recent introduction of a heat collecting panel underneath the solar.......

I'm still trying to see how you are going to collect heat under the panel in the shade? I must be missing something simple and will go back and re-read the whole deal.

Good luck on the project,

Sum

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Our Endeavour 37

Our MacGregor 26-S Pages

Our Trips to Utah, Idaho, Canada, Florida

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[Bill Roosa]

Yep, that there is an "8-ball" sailing pram. Made if from plans in about 3 weekends for about $200

The solar panels are like the front surface of a normal solar thermal collector so the fluid would be directly contacting what ever you mounted the panels on. alternately you can think of the thermal panel as just having solar cells mounted to the front
Being handy and cheap means I went out and bought 72 4 watt solar cells and the wiring, bypass diodes...... and am building it myself. so in theory you could "sew" them to the bimini in any arrangement you wanted. That has some serious shading and mechanical issues though.
here is the whole rub i have with store bought panels mounted horizontally. They are stinking expensive and then I'm just going to get 50% of the output!!!!! On a $/Watt produced that is kinda steep no mater what figures you use. The miser in my just can't do it. My budget for this extravaganza is $1000. that includes mast, tracking head and controls and panels. So that comes in at 1000/(72*4)=$3.47/watt installed
I honestly don't know how that compares to other setups but I know that 280 watts of panel figures close to that without the install and not discounting the loss of output.

 

[Bill Roosa]

another way of saying that is the price for twice the solar panels to offset mounting them horizontal is not nearly as much as the 2 axis tracker or pole mounting (for a DIYer)

 

[Bob J.]

Bill,

Please post some pictures of this when you get it complete. It would be neat to see the end result of some out of the box thinking. Pretty cool!

 

[Bill Roosa]

i was planing on taking pictures as I build it and the finished product.

 

[Sumner]

Yep, that there is an "8-ball" sailing pram. Made if from plans in about 3 weekends for about $200..

Nice, I'll have to check those out. I'd like to have something for the 3 little lakes withing 10 minutes of the house.

...The solar panels are like the front surface of a normal solar thermal collector so the fluid would be directly contacting what ever you mounted the panels on....

So the individual solar cells you bought would be mounted on something like an aluminum shallow tank that is insulated on the sides and bottom? Flexible insulated tubing (to account for the movement of the tracking panels) from the tank down to and into the boat to another insulated tank. And a pump to circulate water up to the tank under the individual cells? I'd assume that the tank under the cells would be very thin to reduce weight up there. There would also be sides above the water tank to support glass above the cells to look more or less like a conventional panel from above.?

It would be hard to do that to the bottom of a conventional panel since the wiring/junction box/diodes are there, but I guess if you made the whole works you would have some control over that. If it worked it could make the cells more efficient with lower temps, but then you would also have to be moving the water the whole time to keep the water temp down on the bottom of the cells and that might be counterproductive with also trying to raise the water temp and not having to pump it as much and using the elect. to do that. I'm trying to see how you could raise the water temp to where it would be useful an still then not degrade the efficiency of the cells.

I think I'd try and address the water heating separately, but if you can pull it off it would be a neat deal.

... So that comes in at 1000/(72*4)=$3.47/watt installed. I honestly don't know how that compares to other setups but I know that 280 watts of panel figures close to that without the install and not discounting the loss of output.

The 260 watt panels I linked to above and most other 12 volt panels are now about $1.25 to $1.45 a watt. Still you have the mounting hardware and the charge controller. What are your plans on a controller? Is that in the $1000 also?

We are a little over $2000 for the 480 watts on the Endeavour for panels, supporting framework, charge controller and good wiring. The panels themselves were bought 1 1/2 years ago when pricing was higher ($160 for 80 watt panel, so 6 were $960 --- now the price for those would be about $700). So we are about $4.20 a watt for that and about twice what you hope to come in at. If you get the tracking down and it provides about the same power as what we have you will do it for about 1/2 the cost which I'm sure will interest a number of people plus they wouldn't have as large an array on the boat to deal with.

The 200 watts on the Mac came in at a fair amount less as the frame structure didn't cost near as much as what we have into on the Endeavour.

Hope you are taking lots of pictures to share with us or is this going to maybe become a commercial endeavor?

Sum

[FONT=Arial, sans-serif]============================[/FONT]

Our Endeavour 37

Our MacGregor 26-S Pages

Our Trips to Utah, Idaho, Canada, Florida

Mac-Venture Links[FONT=Arial, sans-serif][/FONT]