Voltage reduction to match micro grid-tie inverter limits

[gbreisch]

A panel put out over 30.7 volts, say 34 volts and I have a micro-inverter that require a voltage of 11-30 to work. Other than shading some of the panel, is there a way to half the voltage from the panel without as much loss from shading some of the cells to work the inverter?

 

[gbreisch]

I am currently planning to build a panel with that voltage range so I can use the micro-inverter. I might be able to use multiple batteries to the panel then take off of some of the batteries to do it but that is getting expensive and complicated and may require a charge controller as expensive too.

 

[PaulMel]

The panel will not be putting out a lot of current at the top of its voltage range. The most simple way is just attach a large power resistor on the panel to pull down the max voltage in full sun, but that's wasting power. A small switch mode voltage regulator would be best but expensive if the panel is capable of large current. Another clumsy way would be to add 6 or 7 power rectifier diodes in series with the panel to drop the voltage.
Let me know how it goes for you.

 

[gbreisch]

PaulMel, thanks, what you said sounds good and lines up with what I have found by searching online. I will need some numbers and data to locate and understand how to do what is needed to accomplish the task. I still have plans to build a custom panel to match the voltage input range of that grid-tie inverter but progress is slow for finding the glass that has been promised by two different sources. I have a friend that will help build the panel with his solar cells, flux, and conductor tape to be laid out on the glass to put out between 14 and 28 volts or so so the panel can be used to charge batteries directly using the DC or run the grid-tie inverter that has a limit of 11-30 volts. The amperage does not seem to be as limited. My website is www.gbreisch.com for contact information so please send diagrams, material sources, and/or instructions on how to build a box to lower the voltages from the 34 volts down to the 11-30 volt range so I can try it with existing panels. By the way, my PlugInPlay grid tie panels are working great and I have been using single phase grid tie inverters with a range of 22-60 volts and just plugging them into a simple outlet and using the Kill A Watt devices to monitor output from the inverter and panel. I got 10 panels rated at 225 watts each so maximum output would be 2250 watts but realistically, this time of year and angle of sun with efficiencies considered only get about 1800 watts from the 10 panels added up and tested to put out about that power now.

 

[PaulMel]

I have built many panels using cells from ebay. A panel with 36 cells will be around 20v open circuit. That work great with the inverter.
I used glass on the front and back. They MUST be water tight and sealed during a time when the air humidity is low or you will get some condensation inside. I used regular silicon caulking to seal them. Some of my old homemade panels are 10 years old and doing well. Don't use wood for the back. The water will get in there somehow. A couple of my panles have condensation in them but are still working ok.
My info is at www.builditsolar.com and search for pauls solar shed.

 

[gbreisch]

PaulMel - Thanks - I will visit your site soon. My buddy is using EVA to seal them and glue them on to the glass. He said "Jared Vrazel
If you use eva film, you don't glue the cells at all, the film will form a laminate over the cells and to the glass itself...if we go with slygard 184, we just solder all the cells face down on the glass attach the frame, then pour in the liquid epoxy, spread it around, and let it cure for a week or so until they have "ambered" the cells in place to the glass. ...In regards to the glass, 80" x 40" would be enough to do a full 225 watts or so...as far as specs, tempered with a decent snow load is best." He is on Facebook. I have several groups on Facebook concerning Solar - search for "SolarSchool" on Facebook and Google+ for posts and group activity world wide. My local Groups are on Facebook - search for "SandSpringsOK" there to see some of them.

 

[PaulMel]

I don't build panels anymore. The price has come down so much I just buy them. I can not build them for $1/w. Not after searching and buying glass, cells, frame, glue, solder and connections. I have seen them for sale at $0.85/watt. including shipping.

 

[gbreisch]

PaulMel, great website your http://www.builditsolar.com/ . I posted your web link on Facebook at my SolarSchool site https://www.facebook.com/groups/SolarSchool/

 

[gbreisch]

got my last 10 panels for $0.80/watt that included shipping from SimpleRay.com