I thought I had posted this but guess I did not.
On Aug 26th 2009 we had self generated 4 Megawatts of total solar electric power using the 30 panels outside. I think our worst power bill this summer has been $320 which includes the pool pumps running about 8hrs during the day.
Xantrex solar pv widget
Above is my desktop widget showing real time power generation. The money saved is an estimate based on local rates. It however does not include buy back rates or REC credit pricing.
Well its July 29th and its been hot and sunny the past month. We got our power bill today so I sat down to condense my daily/weekly reports from the solar array putting things into perspective.
Mid June – Mid July we used 3728 Kw from the grid and the solar array generated 1080Kw. Our current grid power rate was billed at 10.0cents/kw so we saved about $113. You could say were generating about 33% of our needs. Avg daily temps were 100 so the Geo units were humming away plus running the pool pump about 8hrs/day can build up a load. System total of solar power generated is over 3.3Megawatts!!!
Ive been asked over the past months how long our solar inverter batteries will carry the home so I ran a night time test. At 8pm with no sun shining I cut the grid off with the 400amp switch and manually powered up the Xantrex inverter using the 4 marine batteries. I did shut down the pool and Geo Air conditioners to see how the system handles just the bare essentials like minimal lighting, a tv, refrigerators and all that phantom power likes clocks and dvrs. Things ran smoothly for 1.5hrs without any issues. No lights pulsing or the like were seen during the test.
I did run the pool pump and the basics without any problems. The Geo well pump also runs just fine pulling an estimated 1400watts…ouch. I did not power up any Geo units for this test but will on the next. We will add another battery bank of 4 marine deep cycle batts which will double the run time. I have to watch however just how many sets of 4 I add. If I add 1 set to many the sun will take to long recharging them if I use only the sun. The Xantrex does have a setting to allow grid recharging or not. Today its cloudy so I enabled grid recharge which took a little over an hour to bring the batteries back to full charge. Atleast I know the inverter is fully working.
An update on TXU and excess power buyback (what we sell back). We received a letter a couple weeks back offering 7.5cents/Kw sold back to the grid. They also wanted my REC or Renewable Energy Credits which I didnt like. After a couple calls to TXU and saying I want compensation or strike that part from the contract I guess this created a little fuss in the office and they were going back to see what could be done. Ive read on another website they are rewriting the contract to not include the RECs which is fine if they choose not to buy them from us. Some states are buying the RECs for 13cents up to 20cents/Kw and some others offer up to $90/Megawatt.
Not much else new on the solar subject.
In the last couple days, during weeks of cloudy days and spring rains, the sun broke between the clouds enough to push our solar pv system over 1 Megawatt of generated power!!! The Xantrex system is reporting the the lifetime statistics – Energy produced is 1.022MWh and some 623.6lbs of CO2 Avoided in under 3 months time. Altho nobody sees CO2 its more of the fact that we were that independant in generating our own power. Even on a fully cloudy day the system will produce 200-1000watts which is suprising. So dont let anyone tell you that you need full sun and anything less gets you nothing.
Our local power provider, TXU on the other hand is still dragging along with any sort of billing package allow for the excess power that HAS been pushed back into the grid. Each email and phone call for the last 2months comes back with, give us a couple more weeks. Last month I change our daylight power loads to be the heaviest with the pool running during daylight hours as to not push to much excess back to the grid for now.
The landscaping has already been growing with the warmer days pushing 90 and all the rain. The Geo-thermal A/C fills the underground reclamation tanks enough that we water half the lot in the mornings and by the evening the rest of the property. Depending how the home reacts to the hot summer the tanks might fill even quicker but with the foam insulation we can already tell the house doesnt loose much to the outside elements. By the end of next week I should also have a report back on the air-quality of the inside that our HVAC company is sampling with a small in home monitor. We arent expecting anything suprising but we want to make sure the home has enough fresh air.
Well its Earth Day Apr 22, 2009. I don’t know if its going to get a lot of press we are going to do our part and document it right here.
At 10am central I will disconnect our Oncor grid connection and run the home completely on solar pv. Weather is going to be sunny and 93′ here in Fort Worth Tx. so the test of the foam insulation, UV tinted windows and geothermal A/C will pay off.
I will post times and home status below during the day as my time permits. Solar production below is what the home is only requiring electrically from the solar arrays.
Time: Outside: Inside: Solar production: Oncor grid:
08:30 Sunny 65′ Kit72,Attic64 Shade – 118 watts Connected
09:45 Sunny 71′ Kit73,Attic73 50%sun- 815 watts Connected
10:03 Sunny 73′ Kit73,Attic76 90%sun-1015 watts Disconnected
12:05 Sunny 82′ Kit74,Attic88 100%sun-1751watts Disconnected
15:07 Sunny 90′ Kit74,Attic93 100%sun-1626watts Disconnected
17:03 Sunny 92′ Kit75,Attic98 100%sun-2015watts Disconnected
17:10 We went back on grid before the sun’s angle gets too far to the west.
All in all..things went pretty good today without the grid.
On another subject tho I’ve learned the TXU who is our local REP or Electric reseller of Oncor power hasn’t got there act together with the Net-Metering customers and its 40+ days past the original deadline of March 15th. This means that in our case all the excess power we pushed back to Oncor/Txu didn’t credit us for our current bill. Tho we reduced our usage overall approximately 83Kw is in limbo uncredited back to me. I’m told TXU management wants to make sure they do it right but they knew this was coming last year and already they blew the deadline.
From reading other forums it seems I’m not the only case in North Texas and probably not the last.
Green Mountain Energy tho does have it in writting and is crediting customers Penny for Penny.
Guess Im making a call to the PUC next week to see if I have any ground to file a complaint.
On April 22, 2009 in observance of ‘Earth Day’ we were going to disconnect our electric grid and power our home completely by our new solar PV 6KW system but in testing the system 2 days early we can generate more than we consume so it makes sense to push clean power back into the grid than to simply not use it.
In a test today 10am, with full sun, 90% of the system was in full sun. Grid disconnected we use about 14-18amps with basic loads. Testing of the pool kicked it up to 28amps needed, Geothermal A/C without pool put us at about 45amps. The battery was being used a little but it never drained them.
By 1130am the panels had full sun and the batteries were charged 98%. I connected back to the grid and waited for the inverter to sync up ( 300 seconds delay ). While waiting I watched the outside meter which took about 20seconds for a full rotation. When the solar was back online the meter took about 10seconds to spin backwards proving we are making more than we need under normal load.
This shows us that if the grid fails we can support ourselfs with everything we need just fine. We will have to share the power with the heavy items like the AC, Pool or Oven on a one at a time basis but everything else, lighting, frigs, PCs, TVs, Washer/Dryer will be working just fine when the sun shines. If we feel that increasing our battery run time into the PM hours or cloudy days is a concern then we will have to invest in a larger battery bank as right now its only 650amps.
I took off Good Friday to work on array 2 as bad weather was heading our way for the Easter weekend.
Since I had the racks ready I ran out a guide string for the lower row to keep things lined up best as possible and started the bottom row. My dad came up to help install the last 15 panels which really only took us about an hour & half. The clips from Unirac do speed things up vs having to screw the panel frames to the racks. Since this rack is in running up and down vs side to side Ill have to come back next week and make a couple of minor adjustments to level a couple rows perfectly with the adjacent row.
Saturday I spent the day connecting up the wiring strings and tie wrapping everything to keep it clean. Last was the final connection to the E-panel inside the garage and triple checking my voltages from the arrays. Each array without a load on them is producing 91volts at the racks and 89volts dc at the inverters input. With the last check I powered up the system and waited for the countdown of the inverter to complete. I set the remote to Sell power and the invert started humming big time.
About a minute in tho the PV breakers tripped and shutdown so I had a problem. After looking things over and watching breakers tripping I placed a call to Mid-Nite solar and left Robin a voicemail with the issue. Not expecting a call since it was the weekend my phone rang back in 5min with Robin on the line. He went over my wiring and hardware list and said I needed to make a change to my PV wiring as the charge controllers were fighting for the full load and tripping. A quick trip to Home Depot and quick change to the wiring and things started once again. This time the power up worked and the Xantrex showed 4800 watts being produced !! Thank you Robin for calling me back else it would have been a long quiet weekend waiting for Monday.
I checked my TXU meter and now it was really going backwards, by the end of 3 hours it had already sold back 3Kw excess and my daily peak report showed 5.9Kw max output. Next week is to be sunny so Ill have some really good numbers. I also was stopped by a neighbor we know asking if that was solar. They want me to visit there home and see if they can also install solar for them as they think they have a south facing roof with space. Its good that poeple want to do this and it does give you a good feeling of independence.
I started work this last weekend on array #2 rack system. Due to space limits I had to do this rack differently using whats called a hi-profile tilt system. I also didnt use the Unirac tilt legs due to unexpected costs so I compromised with super-stut at home depot. It did take more time to setup and seasonal adjustments will take longer but it was also less than 1/2 the price. If I find it takes to much of my time or effort I can swap the legs for Hi-profile unirac legs at a later time.
15 panels will mount on the 5 sets of racks making what will be one very nice huge array.
Array #1 went online March 20th and for the 11 days my report said:
preceeding 2009/04/01 00:26
Monthly energy harvest is 142.6 kWh
Peak power for month is 5.549 kW at 2009/03/28
Well after a weeks working in the evenings our first 15 Kyocera 205watt panels were completed.
All the low-profile legs are bolted to the concrete beams with 8 inch J-bolts. The Unirac system goes together pretty easily I must say. It still takes some planning and some measuring to get things just right before the panels are installed. Wiring snaps together quickly but feed circuits took some time with the underground conduits. Cant forget the grounding also as each rail is tied using #8 ground wire back to the Midnight solar combiner box. My cousin helped me pull the 3 #6 copper feeder from the home to the combiner in the underground 2in pipe I installed before landscaping was installed making the pull quick and easy.
Since I planned around the rains which just moved in last night, my next step is to connect Array1 to the inverter and charge controllers first and power up 3Kwatts now before I start Array2 later next week.
Solar PV Array 1 @ 7617lot23.com Fort Worth Texas.
After 3 hot back breaking hours of pumping concrete and setting the j-bolts its time to let the concrete cure.
We needed an extra yard so our total was 10 yrs of concrete. Im not expecting anything to move anywhere for a long time. I’ll spend this weekend cleaning up the mess and leveling out the dirt between the footers making it easier later on to install some bushes on the sides and back of the solar panels.
Hopefully this will be the last day this home see’s a concrete truck for a long time. Last weekend I cleaned up the trenches for the solar rack concrete pads and yesterday I had a crew come in to setup the forms and rebar. Since some of the concrete beams are on a hill sloping down we bumped up the rebar to a #5 rod with #4 along side it to give extra tension strength in case of ground settling. Today the concrete will be ground pumped in from the street and 8″ j-bolts will be pushed in before it sets up. One problem we ran into was due to the slope falling downhill all the beams had to be stepped down to compensate for the grade. This means that the lower array will actually be stepped down with cut rails. Wasn’t what I was planning but short of scrapping all the work already done and no other options for another location, this will still work just fine and shading from the upper rack wont effect the power production.
Solar PV footers
