Tuesday, October 27, 2009

Our New PV System

I've been trying to get the new PV system in the last week or so, and as a result I'm falling behind on getting new entries up on the website.  Thought I would just give a short progress report on the PV system. 

I do plan to do a new section with a lot of detail on the whole PV system process with lots of detail on design, site survey, mount construction, wiring, installation, ...   probably a lot detail more than you ever wanted to see :)

After much looking at a lot of options, I chose the type of system that uses one Enphase micro inverter for each PV panel.   In this kind of system, each PV panel gets its own grid-tie inverter, which is mounted right at the PV panel.  Each inverter takes one PV panel's DC output and converts it to 240 VAC that is grid compatible.  Each inverter plugs into the next inverter in the array, and you end up with all the power from up to 15 PV panels being available as 240VAC at the last panel/inverter in the string of panels.  My system has 10 PV panels at 215 watts each for a nominal total of 2150 watts. 

I bought the system as a "kit" from Wholesale Solar -- this one...

The more common approach on grid-tie systems is to wire several PV panels in series so that the they produce a high DC voltage.  This string of PV panels are then wired to an single inverter which takes the several hundred volts from the string of PV panels and converts to grid compatible 240 VAC. 

There are pros and cons to each approach, but (I think) both are pretty simple systems that can be DIY projects as long as you are VERY careful to mind the safety precautions. 

In my system, the PV panels are mounted on the ground and are located about 100 ft from the house out in the weeds.  The wires are run underground from the PV panels to the area where power comes into the house, and the grid-tie is made there.

I rented a power trencher to dig the trench for the wires.  In our hard soil, this saved a lot of time and effort.

After some debate with myself, I settled on a rather robust mounting system made from 4X4 treated lumber.  I wanted something that would withstand the high winds we get occasionally, and that would last 30 years.  Treated lumber may not be the best choice for long life in some areas, but around here, if properly installed it lasts a very long time.

This shows the framework that the PV panels will be mounted on. 
Anchored in about in 3200 lbs of concrete!

Running the wire (in conduit) from the house to PV array.

I clamped the PV support rails and a PV panel in place just to get the spacings
right and to plan where the inverters would go (they mount to the same rails as the PV panels)

This is where I am -- just waiting for a day or two of descent weather to finish it up.



  1. Hey Gary,
    See you're working hard again. Nice job on the PV system so far. I think you will see a better ROI from your PV system than I've gotten on my wind turbine! Keep the updates coming!
    I started installing my large solar collector array in the back yard today. 10' 8" panels don't look so big until you install them 2 feet off the ground and have to secure the tops. Looks like weather will keep both of us moving pretty quickly on our projects.

  2. Very nice Gary. I look forward to the full write up!

  3. Hi Gary,
    I knew something was keeping you busy! Looks nice. I think that is the way I would go as well, with individual converters on each panel. Will this system size provide a majority of your power demands?
    I looked into putting a system on my house several months ago, but for now it is too cost prohibitive for us.... We use too much power with the kids leaving lights on, tv on, etc.... I am slowly educating them though through the use of the Kill-a-watt meter I got a while back. My 11yo now sees the light. My 5 yo still doesn't quite understand it though. The only other person I need to educate is my wife!
    PS... I still haven't forgot to do a write-up on the one-wire sensor for you. I am actually going to install Windows on my spare computer so I can do a complete Windows write-up so the masses will understand it, rather than trying to show them Linux right off the cuff.... :)

  4. Hi,
    We now have 3 inches of snow in the backyard, but the forecast is for 50F tomorrow, so maybe some good working weather.
    I figure from PVWatts that that the new system will produce about 250 KWH a month on average. That's half of our current bill of about 500 KWH.
    We were at about 1000 KWH 2 years ago, and with some better lights, a new fridge, power strips, ... we got that down to 500 KWH a month -- total cost of maybe $1000.
    The new PV system (10 panels at 215 watt each) is going to come in around $10,000, and the federal and state tax breaks might take that down to $6,500.
    So, $1,000 to save the first 500 KWH/month with efficiency and conservation, and $6,500 to save the next 250 KWH/month with PV -- hmmm, maybe there is a message here :)
    Doug -- glad to hear the one-wire project is still active. I think there will be a lot of interest in it.

  5. Nice setup, Gary! I wish I could afford to do the same. Maybe in 2011 when my daughter is finished university! ;-)
    Doug - Stick with the Linux version...Ubuntu rules!

  6. Rowland,
    I agree 100% Ubuntu is all I use these days. I am going to write up 2 separate "How-to-do-it" articles, the first being for Windows, then for Linux. I know the masses still use an inferior product, but to each their own! LOL. Some day, they will see the light and forget about buying all the virus protection, reloading their OS on a regular basis, etc.... Hate to admit I still have to deal with Windows though at work...
    Cheers, Doug

  7. Looking good Gary!
    Just one comment - here in Maine we try to keep the bottom edge of the panels at least 4 feet off the ground to allow for snow shedding. If you get a lot of snow out there - you'll be doing a lot of shoveling! :)
    When I go out to clear my collectors after a snowstorm I wear full body slickers and a plastic snow shovel, the snow comes shooting off the 8 foot collectors right into my hips. Kinda fun actually.

  8. Hi Guy,
    Thanks -- good thought.
    I did put some thought into height of the bottom of the PV panels off the ground, and ended up going with 1 vertical foot. My 2 sets of solar thermal panels are about a foot of the ground and, while I occasionally have to shovel or tromp down some snow, its not really been a problem.
    We get regular snows through the winter, but don't seem to ever accumulate a whole lot of depth -- maybe a foot at mid winter would be typical.
    I guess my thinking is the the panels will look better and the support structure can be more compact and easier to make wind resistant.
    If we do get a lot of snow this year, I guess shoveling is good healthy activity for old retired farts :)

  9. Doug and Rowland. Good to see linux fans here. Ubuntu in the last few years has really made leaps and bounds.
    Anyway for supposed inexpensive solar products
    I do not believe they deal with micro inverters though.
    I would imagine the micro inverters will allow you to maintain fairly good performance even though you are a bit far from the house.
    One thing to watch out for with sunelec they sell some panels that do not qualify for government rebate. They still supposedly perform well just without rebates.
    specifically the SUN panels. They are really generic evergreen panels. but no government rebate. Depending on your rebates etc you may want to buy the "cheapies"

  10. Hi Animatt,
    This is another interesting site that lists places with low prices for PV:
    I've heard some mixed comments about sunelec, but they do have low prices.
    I'm sure there are a lot of good outfits, but one thing that I liked about Wholesale Solar is that they have been very straightforward to deal with on the phone, and have met all their commitments with no funny business. They also have this rather neat Enphase demo system in which each of the 7 PV panels in the array are a different brand and size -- a good demo of the ability of the micro inverters to handle a mixed panel system.
    With the help of my neighbor, got all 10 panels hung today, and we (finally) have a couple days of nice weather coming, so I should be able to be ready for inspection within a couple days.

  11. Hey Gary,
    Been a Linux fan for about 10 years now. I think it is ready for the masses. Now if we could only get more developers writing code for it.
    http://sunelec.com/ has some good prices. Wish prices were just a little better. Not really cost effective to move over to PV yet, but it is getting close. My next big project will be solar heating panels for the house.

  12. Arggh! You guys are killing me with those prices! Best price I can find, locally, for the equivalent wattage panel (no enphase inverter) is $1250CAN NovaSunPower....and I can't find anything for government rebates on PV panels here in Nova Scotia...there is a 15% rebate on air and water panels. I wish our government would get into the 21st century!
    Doug - Linux was not a huge leap for me. I'm an Oracle DBA and worked with Solaris for the past 17 years. Lately I have more and more database servers with Linux (SUSE and Red Hat).
    I play around with Gambas2 for developing little applications for myself.
    Gary - Hope to join you in the retired O.F. club in 4 years 9 months and 26 days.....but who's counting! ;-)

  13. Hi,
    Got the final signoff from the electrical inspector yesterday on the PV system -- that's a relief :) No pickups, so that was nice.
    Now have to get the net meter installed by NorthWestern energy -- sounds like that could take as long as 4 weeks.
    The system was producing 1850 watts for most of yesterday.

  14. Great! So, prior to the net meter being installed, are you still able to use the energy you harvest? Or do you just not get paid for energy produced over what you use? How does that work? I really need to look into getting a system in place.

  15. Hi Doug,
    I have phone call in on whether I can leave the system on before the net meter is put in or not -- right now its on. One person I talked to said the normal time to get the net meter installed was more like 2 weeks, but they allow themselves 4 weeks to be safe.
    I am guessing that the way it is working now is that it basically does not register when the meter is going backwards, but that I still am getting credit if the PV is just slowing down the meter in its regular direction. Kind of like a ratchet that does not allow the meter dials to move backwards.
    Right now I'm looking out on 6 inches of new fallen snow, and its still coming down -- the PV monitor is reading 0 watts production :)

  16. That's a nice feeling, am sure to watch the meter slow to a crawl/stop. Looks like we are getting snow starting tomorrow, then all next week.

  17. Gary,
    My sister watched her old meter go backwards after her Skystream 3.7 was put up. When they installed the 'net meter', she didn't get anywhere near her expected output from the turbine....according to the first few power bills. The meter was changed, again, and her bottom line has improved but I still don't think it's near the full potential. Not that I think the power company would scam you, but keep your own production records.

  18. Hi,
    The retired O. F. club is a good place to be :)

  19. I set up a 1-wire system for my father's commercially made solar DHW service. I used a JrSX ultralow power PC running debian (see http://njhurst.com/electronics/installing-linux-on-jrsx.html) and the usb 1-wire transceiver. I thought the plot was on his environment logging page (see http://www.ajhurst.org/~ajh/personal/environment.xml), but apparently he hasn't worked out how to get the data into the right form yet (there was some issue about synchronising the data from different sources into a single plot).
    The norhtec JrSXs (the more recent DXs) are great value for these sorts of projects - they boot from compact flash, they have a bunch of ports, including a 24 pin digital I/O socket on the front, they run debian quite well, and they use less than 1W power running at full speed (dropping to perhaps a few 10s of mW idle).
    We just taped the DS1820 directly to the panel hot tank connection and insulated the whole lot with some foam. The temperature measured does track the outlet temp quite well, and the sensor is 10m from the computer.

  20. Hey Nathan,
    I could see a lot of uses for the system you describe -- just don't think I could wade through all the Linux stuff.
    The idea of being able to log a few sensors at 1 watt power consumption and also be able to access the data easily would be great.
    There would be a very good market for a device that would make this easy to do for an electronic duffer like me to use such a device.


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