What would you do?

krsmichael · October 2015

I've inherited 4 Soitec Plug and Sun tracker modules.

http://www.soitec.com/en/products-and-services/solar-cpv/plug-and-sun/

They were designed for remote power applications. As the company is French, and they designed for European standards, the modules produce ~900 volts open and about 790 volts max load. The amperage is about 3.8 amps. My guess is that the voltage and amperage selections were selected for smaller wire dimensions, lower current loss over the distances they were planning to use.

I want to use them in a ranching remote operation. These will not be grid tied. I'm having a problem coming up with a solution. The closest thing I can find is the Schneider Electric 600-80 charge controllers. They are limited to 600V due to US standards. I've looked into trying to acquire a buck converter that would handle that voltage. The output side of the buck converter should just be less than 550 volts. I am also looking into European solutions and running the system at 220V 50 hz on the load side. I would order European pumps and motors to build my project. I'm also investigating 3 phase 208 volt systems. Any thoughts on how I can put these systems to use?

The cost can't be too expensive because at a certain point, I'm not going to use only the trackers and put an Ironridge pipe system on it with off the shelf 300 watt panels. I should be able to put 9 to 12 panels per tracker. I would prefer the Soitek modules as they produce a lot of power in a small space. The Soitec modules I have are about 40% efficient as opposed to ~20% for traditional PV.

Regards,
Michael

Aguarancher · October 2015

Are you saying a single solar panel is 900 ocv or that is the string (series wired) voltage? If that is for a string of panels, you could just rewire the strings to a lower voltage.

krsmichael · October 2015

It's a sealed solar module. It puts out 900 ocv. It can't be sub-divided. It can't be opened and rewired.

inetdog · October 2015

Basically, unless you can get European components in the gray market and can skirt electrical code and inspections you are up the proverbial creek.
If it is a commercial rather than residential installation, then up to 1000V DC is allowed and there are large inverters that accept voltages in your range.

krsmichael · October 2015

I saw the commercial boxes. They look expensive as hell. The application is rural agriculture. And it's remote. No people around. The acreage is zoned commercial so I can probably install it as comercial.

krsmichael · October 2015

And, I do know people in Germany.

softdown · October 2015

In this case.....das is ser gut.

krsmichael said:

And, I do know people in Germany.

Photowhit · October 2015

krsmichael said:

It's a sealed solar module. It puts out 900 ocv. It can't be sub-divided. It can't be opened and rewired.

I guess I don't understand, is it made of "undrillium" or "unsawium" I would guess there's no warranty...

You ask "What would you do" I'd have at it, solar electric is pretty basic stuff even for concentrating solar panels. All the photos appear to have 10 panels on the Plug&Sun module, There have to be wire connecting them.

If you intend to invest in a charge controller and they are highly efficient (@30%) I'm not sure why you would intend to replace the panels, unless they have a very short life, I understand there often is with concentrating panels.

boB · October 2015

Where are you getting this 40% efficiency number ? Is there some kind of concentrator involved ?

I suppose you could use two isolated charge controllers (the Schneider may be isolated ?) or a couple of isolated PV inverters maybe in series, but I don't think you may have much luck getting anything around 550 VDC out unless you build your own or maybe find some esoteric unit of some sort. Even if you could use two converters in series, you may have trouble getting them to track properly unless they have custom input voltage settings.

If I had inherited these, I would try to sell them and buy something useful. I am very skeptical about this 40% efficiency though. If they ARE some kind of concentrating solar, I would definitely sell them and get more useful PV.

SO reading more here, it does appear they are concentrating PV. I think I have seen these before many years ago at a solar show. Yeah, I'd dump them as concentrating modules are more than likely very short lived because of how hot they get. Also, keeping the tracking system working properly may be a problem unless they are very good.

What were these originally used for to be 900 Voc ?

inetdog · October 2015

High DC voltages have been common in European equipment for awhile, given their higher standard line voltages. But 900V is high even for that. The modules I saw a brochure for on the website you linked offer a 48V DC output, so I assume that that is the battery bank voltage they design around.

One of the problems (complications, costs) of concentrating solar is that you MUST use at least a single axis tracker or a two axis tracker depending on the exact design. Without that the concentrated beam of sunlight would miss the PV chip.
More maintenance and more to go wrong.
The efficiency per area of active PV material may be higher because of the intensity of the light and the cell chemistry used, but the efficiency in terms of the power output per overall panel area is AFAIK not any better than flat cells.

PS: You cannot use a simple buck converter for this purpose. You would need a converter that maintained a fixed ratio between input and output voltage rather than a fixed output voltage, otherwise the MPPT algorithm in the charger would not be able to actually change the voltage and current conditions at the panels.

boB · October 2015

Yes, there is now 1000V and even 1,500V PV but not normally for home use. I know that It's hard to pass up something that is free. But if it's too hard to use and a PITA to track, why not just get something that is more useful ? Might even be able to trade it in to get more power of PV than this. If it's 3.8 amps at 900V, that's around 3kW.

krsmichael · October 2015

Phtowhit, they are sealed. The front side of the module has glass panels have fresnel lenses that concentrates the sun 500x (according to the manual) There is a SOI chip that sits on the hot spot and converts the photons to energy. If the frame is opened, moisture can get in and damage the SOI. If the assembly stays sealed, the life time of the module is supposed to be 30+ years. The modules come with two axis trackers. They are substantial and extremely well made. The Germans really do know how to build things. There is a wind speed monitor to pull the panels flat if the wind speed rises too high. There is a device on top that keeps the panels on the sun. It is essentially an array of photo resistors that maintain alignment. It contains a GPS modules so that it can self align. It has a clock and it knows where the sun is supposed to be so even in over cast conditions, it functions. The power curve is not a bell curve but instead a quick rise to max where it stays for hours until the sun goes down and then the power quickly drops off. By my calculations, after all the losses, these panels are provide the same power as a traditional panel using 30% less area.

The quoted 48 volts is from the battery pack. boB, it is not a PITA to track. These units have been sitting at the manufacture and running for 3 years without interruption. The problem is, they were not set up for power generation but were the test trackers that the newly manufactured modules were put on to be quality tested. So the battery side of the equipment does not exist. I found a supplier in Australia that sold them. I'm trying to find out if they have the battery system side of the equipment. Again, this is not for a residential setup. It will not be grid tied.

BTW, I have very large battery backup traditional solar system at my home. I'm not looking to hook these things up to my home. I'm trying to think outside the box to put some impressive engineering to work. These systems were donated to third world villages to bring power to them. As an engineer, I want to know what I can do with these things.

Worst case, I store these items until NEC 2014 is implemented by manufactures.

krsmichael · October 2015

inetdog said:

PS: You cannot use a simple buck converter for this purpose. You would need a converter that maintained a fixed ratio between input and output voltage rather than a fixed output voltage, otherwise the MPPT algorithm in the charger would not be able to actually change the voltage and current conditions at the panels.

inetdog, What your wrote here confirms what I thought. Thanks for commenting.

krsmichael · October 2015

We use the PTO on tractors to drive generators. Could I use a high voltage DC motor to do the same?

Photowhit · October 2015

Yes...

...but there are 10 of those sealed modules or I'm looking at the photos funny. They must be connected.

I would seriously doubt that they can, or would want to try to, seal the 8 x 12 foot complete assembly.

Might call the company and ask what they recommend for an off grid installation, likely they will have a ready answer. For your application you wouldn't need to worry about code...

krsmichael · October 2015

Photowhit said:

Yes...
...but there are 10 of those sealed modules or I'm looking at the photos funny. They must be connected.
I would seriously doubt that they can, or would want to try to, seal the 8 x 12 foot complete assembly.
Might call the company and ask what they recommend for an off grid installation, likely they will have a ready answer. For your application you wouldn't need to worry about code...

The module design is a bit different than what you are seeing in the photo. The entire frame, 8 x 12 is sealed as a unit. The divisions you see are the aluminum frame which provides the structure for the glass panels. The entire panel is shipped as unit. There is not warrantee on these panels. When they deliver the module, I am going to examine it. I may pull one of the glass panels, rewire it internally and drop the voltage to 450. I would just have to do it on a very low humidity day. I would then reseal the panel, pull a vacuum on the frame and throw a few oxygen absorbers in the frame for good measure. So I have not ruled out rewiring them.

The company gave us 32 of the frames. We plan to build two green houses out of them. I'll go out and take pictures of what I have.

krsmichael · October 2015

These are the frames. They were rejected for QC purposes. We'll use them for the green house frames. Upon close examination, I think they can't be sealed. The MC4 connectors have a rubber seal but it's wouldn't hold a vacuum.

krsmichael · October 2015

This one of the trackers. The motors and sensors are all 24 volts. The box on the ground is the brain. These were meant to be run in doubles and triplets. The back of the control box, if complete, put out 220. Those electronics are missing from my control boxes. I think.

Photowhit · October 2015

So if you were an engineer planning on producing these concentrating solar arrays, that you knew must be sealed and likely gas infused, would you build one size module that you could insure was sealed, like perhaps these;

After building these units you could assemble them into as large an array as you like. (Wires would be connected from unit to unit within the array, in the frame work you have pictured)

Then combined them into the size array you wanted like those you have posted.

I suspect each module is less that the 900 volts and run in one string. If you had more than 2 strings, much as with multiple strings in a standard system, you would want to have a fuse or breaker.

So you appear to have seen these, if the wires from each module don't go into a breaker box and rather get connected from one unit to another, then the base voltage of each unit is less. When solar panels are connected in strings, the voltage adds and the amperage remains constant (provided each has the same amperage to begin with)

Photowhit · October 2015

Another picture of a module I found. I do suspect that they are not only sealed, but filled with an inert gas, much as double and triple paneled windows.

Dave Angelini · October 2015

Looks like R & D with the wheels on the tracker. If things went better for them the tracker would be in cement or a steel pipe driven into the ground.

krsmichael · October 2015

The alignment of the modules have to be spot on. When I actually get one, I'll examine it carefully. The frame I got imply that they are not sealed, but I am getting the newest gen they produced and they may look like what you posted. Each one would not produce the 900 volts. I am sure they are wired in series. We'll see.

Dave, the trackers were meant to be mobile. At the base of the tracker, you could put it on a pier. In high winds, the panels move to a flat position so as to not generate lift.

krsmichael · October 2015

Photowhit said:

Another picture of a module I found. I do suspect that they are not only sealed, but filled with an inert gas, much as double and triple paneled windows.

I confirmed with my wife that the modules are sealed at this level. Which tells me the frame cells are not sealed. There is a good chance I am going to be able to rewire them. :-)

Dave Angelini · October 2015

Most trackers go flat for hurricanes and vertical for snow. My point was that since you would want these to be "bonded" with the earth,
the wheel just seem to me as temporary.

krsmichael · October 2015

Dave Angelini said:

Most trackers go flat for hurricanes and vertical for snow. My point was that since you would want these to be "bonded" with the earth,
the wheel just seem to me as temporary.

That's actually a good point.

What would you do?

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