Bring on the sun!

[begreen]

Finally got the new array up and connected. It adds 2700w of capacity. In April it will be rotated to face the SW to capture more afternoon light. The ground array is facing due south and will get mostly morning through mid-day peak sun. The new array is up on a big stick to minimize shadowing in the afternoon. It's 8in. diameter sch 40 pipe set in 7ft. of concrete. We are now at 5.6KW installed, with an average usable output probably more like 4.5KW.

 

[Jags]

Outstanding. What line are the panels? Using micro inverters?

 

[begreen]

They are Idek 270w panels, made in WA state. They feed into a dual-channel Aurora Inverter on the back of the ground array. We've only been using one channel up until now. Here's the Aurora being rewired. We pay a premium up front for installing made in WA components, but that translates into much quicker payback and jobs in our state.

 

[Jags]

Too cool.

 

[semipro]

Sigh of exasperation...dripping with envy.
I've been considering lately a home equity load to finance my dream "grid".
I keep waiting for incentives in VA but I'll probably die first...and I'm not that old.
I'll just keep hacking away at cheaper efficiency upgrades on my house in the meantime. Not nearly as fun as PV though.

 

[begreen]

I waited a lot of years to get this setup. It's good to see it finally happen.

 

[DBoon]

Hi begreen, I'm curious what the single-pole ground-mount that you installed cost (separate from everything else, but installed).

 

[begreen]

I didn't install anything, it was contracted out. The system before rebates kick in is about $13K, but I don't know how that breaks down exactly. $2500 is for the pole mount array. I would estimate $1500 for the 20' pole and setting it in concrete, but that is just a guess. It was done professionally with an excavator. Estimate $6-7K? for the panels (wild guess, WA made panels are expensive) and the rest for labor.

 

[Where2]

Mmm, I like that monopole. Any idea what brand mount is on top of that pipe? It looks like Washington State uses something around 20psf for snow load calculations, I'm looking for something that will withstand 100psf, plus dead load.

 

[begreen]

This is a DPW pole mount. It was designed for 25psf, 90 mph wind.
(broken link removed to http://dpwsolar.com/index.php/applications/commercial/9-commercial/18-top-of-pole-mounts-tpm)

 

[BIGDADDY]

When you say 4.5 KW output is that per day or hour?
Are you shutting down the stove and heating with electric yet?
The HVAC guy that services my geothermal heat pump told my he got an estimate of $100,000 for a solar setup that would produce all his electric and then some.
Your investment seems much more realistic in terms of seeing a return on your money.
I had thought of buying a generator for power outages and was looking at $8,000 whole home generators. If you just used it for power outages you got a great deal with that setup and you don't need propane.
I bet your solar panels will come in extremely handy with any power outages.

I don't know anything about solar panels but am curious. How are they wired into your home? Are they straight into the panel for every circuit or are they for just certain breakers in the panel.

 

[Where2]

When you say 4.5 KW output is that per day or hour?
I don't know anything about solar panels but am curious. How are they wired into your home? Are they straight into the panel for every circuit or are they for just certain breakers in the panel.

The measurement of 4.5kW Begreen used is the instantaneous DC output of an array (group) of panels at Standard Test Conditions (STC). The way PV panels work, the more intense the sunlight is, the more DC energy (measured in Watts) they put out. In order to compare apples to apples between various panels, each PV panel is tested with a common intensity of light per square meter (1000W/m2). The power output of a PV panel also varies according to the temperature of the silicon cells in the panel, so STC uses 25°C for that test value. On a cold day in the spring with snow on the ground working as a reflector, some PV arrays can generate more than their STC rated power.

Begreen can comment about his wiring, but my PV array is split into two circuits of ten 220W panels each (with individual inverters for every panel behind every panel on the roof converting DC to AC). Those two AC circuits (2.2kW DC of panels each) land in a new 100A AC panel (solar combiner panel) I installed adjacent to my service entrance panel. At that point, the two AC circuits combine into one AC circuit that is back fed into a single 30A breaker in my service entrance panel where the presence or absence of significant loads in my house determines whether I use all the energy the panels are making, or whether some of it goes out into the grid to my neighbors homes for their needs. My meter accumulates two numbers: Delivered and Net. Delivered is all the energy that has come IN from the power grid to meet my needs (just like a house with no PV array). Net is all the excess power I've sent OUT to the grid. To bill me, the utility uses the formula: ((Delivered-Net) + % tax + fixed meter charge - credits) = $$ monthly bill.

The 4.4kW array on my roof, generates ~66% of the energy my all electric home needs (and we use a 3.5 ton central A/C 10 months out of the year). My total city water/sewer bills for last year were $200 more than my total electric bills for the year. The sun comes up = it works. Once the system is installed, it's literally that simple, unless you get snow accumulations on the panels. Clouds, shadows, and snow accumulations on the panels lower the DC output of the PV panels.

 

[begreen]

That's right. This is the instantaneous reading. If we get 4.2KW for an hour then we have generated 4.2/KWh. The second array is primarily to take advantage of our long daylight hours in late spring thru early fall. It will face southwest during that period.

Where2, I'm not understanding the high snow load requirement. Is this for another location besides FL?

 

[jebatty]

Congrats to you, begreen. I haven't known a PV user yet that did not have fun with the system. After install, do nothing, get electric energy, and make money from the sun. My 6.89kw system produced 9MW its first year, now 1+ months into year 2.

 

[begreen]

Thanks. Right now I am trying to figure a safe way to get up to the pole top collar twice a year to loosen the bolts and rotate the array.

 

[Where2]

Where2, I'm not understanding the high snow load requirement. Is this for another location besides FL?

Yes, my next install is going to be in a different climate (for me) at 45.8°N in Northeastern Maine. I haven't seen snow flakes at 26.8°N since the winter of 1977 when I was catching them on my tongue as a child in the front yard. We didn't have enough accumulation to make a snow ball that winter or any winter since, let alone have 100psf snow loads.

As for getting to the top collar, your numbers (20' pole, 7' embedded) indicate the collar is ~13' above the adjacent ground. I think I understand the concern of leaning a simple extension ladder against such a small round object, rather than a flat surface. A large articulating ladder like your installer had would seem to be the perfect solution, although not inexpensive. I stopped worrying about the price of ladders after I began to justify any ladders expense by comparing the cost of the ladder to the expense of a trip to the ER. I've had a friend from church who died after falling from a ladder, and had a neighbor who had a very close call falling off a ladder with a chainsaw. A more budget conscious solution might be to weld climbing pegs on to the pole, if you have any friends with welders.

 

[begreen]

At that latitude you could change your array angle to near vertical during the snow season. That should stop it from getting any heavy accumulations.

PS: I'm starting to think we have an 18' pole. Have to get a tape on it today to check. Thanks for the suggestion about welding steps and the articulated ladder. I am going to get one. They are about $120 at Costco and made locally. I am also thinking about a 12ft orchard ladder. They are good on slopes.

EDIT: Checked the measurement. We have a 20ft pole. 7.5ft in the ground, 12.5 above.

 

[Highbeam]

The measurement of 4.5kW Begreen used is the instantaneous DC output of an array (group) of panels at Standard Test Conditions (STC). The way PV panels work, the more intense the sunlight is, the more DC energy (measured in Watts) they put out. In order to compare apples to apples between various panels, each PV panel is tested with a common intensity of light per square meter (1000W/m2). The power output of a PV panel also varies according to the temperature of the silicon cells in the panel, so STC uses 25°C for that test value. On a cold day in the spring with snow on the ground working as a reflector, some PV arrays can generate more than their STC rated power.

Begreen can comment about his wiring, but my PV array is split into two circuits of ten 220W panels each (with individual inverters for every panel behind every panel on the roof converting DC to AC). Those two AC circuits (2.2kW DC of panels each) land in a new 100A AC panel (solar combiner panel) I installed adjacent to my service entrance panel. At that point, the two AC circuits combine into one AC circuit that is back fed into a single 30A breaker in my service entrance panel where the presence or absence of significant loads in my house determines whether I use all the energy the panels are making, or whether some of it goes out into the grid to my neighbors homes for their needs. My meter accumulates two numbers: Delivered and Net. Delivered is all the energy that has come IN from the power grid to meet my needs (just like a house with no PV array). Net is all the excess power I've sent OUT to the grid. To bill me, the utility uses the formula: ((Delivered-Net) + % tax + fixed meter charge - credits) = $$ monthly bill.

The 4.4kW array on my roof, generates ~66% of the energy my all electric home needs (and we use a 3.5 ton central A/C 10 months out of the year). My total city water/sewer bills for last year were $200 more than my total electric bills for the year. The sun comes up = it works. Once the system is installed, it's literally that simple, unless you get snow accumulations on the panels. Clouds, shadows, and snow accumulations on the panels lower the DC output of the PV panels.

So you simply backfeed the main panel with AC from the panels and the meter does the rest? I thought you had to worry about synchronizing the AC waves, thought you had to worry about backfeeding the grid when the powerworker thinks the lines are dead (like a genset people get pretty excited about backfeeds).

 

[begreen]

Grid synchronizing and monitoring is done by the inverter. It shuts down when it detects an anomaly in the grid. It also has a delayed startup that waits for about 5 minutes of continuous grid power before feeding the grid. We have two meters, one production and one consumption. The production meter is a smart meter that shows the amount of energy you are feeding the grid vs how much you are pulling from it.

 

[Jags]

Hmmm...too bad the pole couldn't have been engineered on a swivel. Turn the thing at ground level...a locking band for securing the position....

 

[begreen]

I'm sure it could have been, at a higher cost, especially if I still wanted the 90mph wind rating.
Most of these systems are installed in a fixed position. If I don't see worthwhile gains I may just leave in in a SW orientation.

 

[Where2]

So you simply backfeed the main panel with AC from the panels and the meter does the rest? I thought you had to worry about synchronizing the AC waves, thought you had to worry about backfeeding the grid when the powerworker thinks the lines are dead (like a genset people get pretty excited about backfeeds).

Yes, you simply back feed one of the AC panels. In my case, I chose to back feed a double pole breaker in my NEMA 3R combined service entrance/disconnect panel on the back of my house which can accommodate up to 20 single pole, or 10 double pole breakers. The all the circuits for my house are running off a secondary sub-panel downstream of the CSED panel (one concrete block width away on the inside of the house). In my case, one meter tracks energy flow in two directions. Because Florida has no SREC trading system, there is no point in having two meters. In states with SREC trading programs, one of the two utility grade meters typically attached to the PV system tracks total PV generated energy.

You buy a real UL 1741 listed grid tie inverter, it does the sync & safety stuff for you. You basically plug it in, wait ~5 minutes and magic happens. The more of them you plug in, the slower your electric meter spins, until it stops spinning, reverses direction, or the sun goes down.

Gensets are not grid tie inverters. Grid operators and their employees are very cautious of gensets, and they should be. Most gensets were never designed to follow the existing 60hz grid sine wave, and plugging two different phased AC sources onto the same wire is a recipe for disaster. Gensets are intended to have an automatic or manual transfer switch that clearly disconnects the grid wiring from the home to turn the home into an island while the genset is running.

A UL 1741 listed inverter is designed to listen to and follow the output of the existing grid. If the 60hz frequency of the grid isn't there at all, or the grid is operating outside the parameter limits programmed for voltage and frequency specifications, a UL 1741 inverter will either stop generating power (assuming it was generating), or continue to watch and wait until at least ~5 solid minutes of stable power within the grid parameters has been seen before grid synchronized power generation begins.

 

[Highbeam]

Yes, you simply back feed one of the AC panels. In my case, I chose to back feed a double pole breaker in my NEMA 3R combined service entrance/disconnect panel on the back of my house which can accommodate up to 20 single pole, or 10 double pole breakers. The all the circuits for my house are running off a secondary sub-panel downstream of the CSED panel (one concrete block width away on the inside of the house). In my case, one meter tracks energy flow in two directions. Because Florida has no SREC trading system, there is no point in having two meters. In states with SREC trading programs, one of the two utility grade meters typically attached to the PV system tracks total PV generated energy.

You buy a real UL 1741 listed grid tie inverter, it does the sync & safety stuff for you. You basically plug it in, wait ~5 minutes and magic happens. The more of them you plug in, the slower your electric meter spins, until it stops spinning, reverses direction, or the sun goes down.

Gensets are not grid tie inverters. Grid operators and their employees are very cautious of gensets, and they should be. Most gensets were never designed to follow the existing 60hz grid sine wave, and plugging two different phased AC sources onto the same wire is a recipe for disaster. Gensets are intended to have an automatic or manual transfer switch that clearly disconnects the grid wiring from the home to turn the home into an island while the genset is running.

A UL 1741 listed inverter is designed to listen to and follow the output of the existing grid. If the 60hz frequency of the grid isn't there at all, or the grid is operating outside the parameter limits programmed for voltage and frequency specifications, a UL 1741 inverter will either stop generating power (assuming it was generating), or continue to watch and wait until at least ~5 solid minutes of stable power within the grid parameters has been seen before grid synchronized power generation begins.

Thank you Where2. I have treeless, flat 1 acre lot with full south exposure and an outbuilding with a subpanel. It seems so easy with the inverter information you gave.

 

[begreen]

Word, if you field mount the array, like our first installation. Raise it up to at least 5-6' on the lower edge. That will serve two purposes. It will protect the array from random debris hitting it from weedeaters or mowers and it becomes a convenient shelter for equipment You could even stack wood under it.
Our field mount array lost a panel after just 2 weeks due to a stone hitting it from a weedeater. Ouch!

 

[Where2]

It seems so easy with the inverter information you gave.

The functional part literally is easy, the challenging part is the permits and paperwork to make it legal with the utility and your local building department. I'm designing my second system right now for an 80+ acre parcel, but your 1 acre property will work fine. My house in FL is on 1/4 acre and it generates just fine. I get a little shading from a palm tree to the east and an oak tree to the west in the neighbors yards, but it's not unbearable. I'm glad that I went with microinverters rather than a string inverter. Microinverters tolerate my minor shading issues without skipping a beat. I only generate ~66% of the energy my home needs because my array size was limited by the size of my second floor roof. I may still add a small ground mount array in the backyard to cover the remaining energy needs. At the moment, in cautiously watching and waiting to see what happens with net metering in FL. I continue to automate systems in my home to make use of as much of my PV generation as possible during the hours it is generating, to minimize my back feeding to the grid and my "Net" reading every month.

My second system design will be slightly larger than my first system (~4600W). The home the second system is attached to is smaller, but the climate is much more harsh. I hope to wean the second home off the oil furnace in the basement for everything but extreme cold spells (if I add an ASHP and HPWH), and that should be where the savings come in.

Begreen, thanks for the advice on raising the mount. Being adjacent to a tilled field known to contain a few stones, your advice is quite appropriate to my next design.