Should I Progress through enough PV incentives to a PV system?

[semipro]

The angle is not such a big deal these days, . . .

Just curious about your statement. From what I've seen, nothing has changed much in the past 20 years when it comes to the technology. In fact, with the panels themselves, little of high consequence has changed in the past 50 years. The needs of solarization are the same.

About some other comments on this thread about adding systems to allow bypass to shaded panels? I'm not sure what the alledged problem is. A good installation with good panels will have bypass and blocking diodes. These stop current backflow, and allow current to pass through shaded panels in strings. It's a pretty simple solution that I assume has become pretty-much standard. Without the bypass diodes, shaded panels can overheat in darkened areas.

With my setup, I "killed two birds with one stone." I built a new barn to keep tractors and dozers in, and built a special angle south-facing roof just for the solar panels. It's about 500 feet from my house. Inverters are in the barn, so the run to the house is 220 AC, not DC. Panels are wired up for 48 VDC.

Wow, I don't see one thing in those photos that I'm not envious of. Great scenery, the barn, the equipment, the solar setup. Damn! I knew there was a reason I was avoiding this thread.

 

[benjamin]

The angle is not such a big deal these days, . . .

Just curious about your statement. From what I've seen, nothing has changed much in the past 20 years when it comes to the technology. In fact, with the panels themselves, little of high consequence has changed in the past 50 years. .

Hello? the consequential change has been a huge drop in $$$/watt. Standard practice these days is to put the panels flat on the roof whether it's facing south, east, west, or apparently even north from some of the installations I've seen? In the past the panels were just so expensive that it was ridiculous to not optimize the output. These days it's usually cheaper (and more reliable) to add more panels than put the array on a tracker.

I'll leave the shading issue to somebody who knows for sure what they're talking about, I thought there was an advantage to the newer technologies, but can't tell you exactly how they work.

 

[jdemaris]

Hello? the consequential change has been a huge drop in $$$/watt. Standard practice these days is to put the panels flat on the roof whether it's facing south, east, west, or apparently even north from some of the installations I've seen?

I doubt that's a standard practice for anybody using state-incentive money - which is usually the case with grid-tie intalls. Here in New York - a proposal and plan has to be submitted, showing the best use of the sun. They would not allow payment to someone who wanted stick panels up facing the wrong direction, or a a very bad angle, or even if small percentage of the panels got shaded part of the day.

Fixed mounts here in the northeast have always been the standard. There is little to be gain here with mounts that track. If the latitude is 15-25 degrees, the panels get mounted at the same angle. If 30-35 degrees, you add 10 degrees. If 35-40, you add 15 degrees. If the latitude is 40 degrees of higher, you add 20 degrees.

Now, if someone is sticking in non-grid-tie with no state incentive money - they can do whatever they want. Much of the equipment can cost 1/2 what the grid-tie certified sutff does. The downside is - you waste any extra power you make, No way to "save it for later."

The prices on panels have come down, but not by a huge amount for grid-tied systems that require certain certified panels. My Kyocera panels cost me $3.75 per watt 5 years ago. Now they are $3 per watt which isn't a huge difference. Some of the electronics involved have steadily gone up, not down. Same with standby battery banks. They've doubled in price in the past five years. Another factor is - if you live in a state that forces you to use a state-cerftified installer. If so, they often add their own markup to the equipment and don't let you shop around for the best prices.

With off-grid non-certified panels? I can sometimes get them for $1.50 per watt. Five years ago I could buy for $2.75 per watt.
I've got an off-grid setup in the NY Aridoncack woods. They are facing all over the place. There is no one spot that gets sun all day, so some point towards the morning sun, some to the noon sun, and some to the afternoon sun. If it was grid-tie, they would no have allowed it.

 

[DaveH9]

"These day" the lower cost of the equipment combined with incentives makes the tilt much less of an issue then 10 or 20 years ago. Still can get a good return, though better if the tilt is optimum. The blocking diodes will stop back flow and prevent cell overheating but will not let voltage through if all cell strings in a module have a cell shaded. That at least is my understanding. The same thing happens at the module string level, the whole string is effected.

 

[benjamin]

Apparently there is still some debate about mounting flat to the roof vs tilted up.

Dave, Home Power mag and I believe that the best practice it to lay them flat on the roof, for the structural problems and economic considerations Dave mentioned, and the public acceptance sought by Home Power.

 

[DaveH9]

Here is a link to solmetric isolation tool. Just plug in your zip, tilt and azimuth and it tells you what to expect from your conditions.

http://www.solmetric.com/annualinsolation-us.html

 

[jdemaris]

". The blocking diodes will stop back flow and prevent cell overheating but will not let voltage through if all cell strings in a module have a cell shaded. That at least is my understanding. The same thing happens at the module string level, the whole string is effected.

Every panel I own has soldered-in blocking diodes, and all my panel-strings have bypass diodes. I can't say everybody uses them ,but they certainly aren't rare.

 

[jdemaris]

Apparently there is still some debate about mounting flat to the roof vs tilted up.

I don't know why there is any general debate. It all depends on the specific intallation and many local factors have to be considered.
Latitude, highest anticipated wind, snow, install cost, type of roof material, etc.

Here's some info from my latest Kyocera panel install manual for anybody that's interested.

 

[pring7]

This has been very insightful. I am leaning against doing this problem for now because I don’t want my roof torn up or leaking. The guys I used for the evacuated tube system did a good job, but I can imagine that a larger PV system would involve more trips to the roof and more shingle stones coming off. I think that maybe one day when the roof needs reroofing I will look into the solar shingles.


I think that the idea of designing a barn/boat house with a good angle (30 degrees) would be the way to go. Would the consensus be that the panels are best suited for a metal roof? I had a metal roof on my house in Georgia and I think that is a good fit for my barn project.


Jdemaris: It looks like you have about 30 panels, and that’s a 6 kwh system? I would like to get an idea of what size my roof would need to be to handle a 2 kwh system vs a 10 kwh system. I know that some panels do better than others.

 

[benjamin]

"the solar modules should be tilted for optimum winter performance" seems to indicate that they are assuming an off grid installation, whereas a grid tie would usually be more concerned with maximum annual production, and not as concerned about a high tilt angle.

I don't know as much about this stuff, but maximum power point trackers (in the inverter, not a physical array "tracker") are the gizmos I thought offered a partial solution to shading.

Edit: yes, I'll say that a metal roof is the best solution short of using the panels themselves as the roofing material, which is not commonly done yet.

 

[mbcijim]

We seem to have attracted a technical expert or two!

Question:
On my 200KW project the inverters were 11-12% of the project cost, i.e., very, very low six figures. When I look at them they aren't much bigger than a standard 200 Amp panel. Why the hell did they cost so much??????

My installer swears they can be repaired and I'll never have to replace them. True?

 

[DaveH9]

This has been very insightful. I am leaning against doing this problem for now because I don’t want my roof torn up or leaking. The guys I used for the evacuated tube system did a good job, but I can imagine that a larger PV system would involve more trips to the roof and more shingle stones coming off. I think that maybe one day when the roof needs reroofing I will look into the solar shingles.


I think that the idea of designing a barn/boat house with a good angle (30 degrees) would be the way to go. Would the consensus be that the panels are best suited for a metal roof? I had a metal roof on my house in Georgia and I think that is a good fit for my barn project.


Jdemaris: It looks like you have about 30 panels, and that’s a 6 kwh system? I would like to get an idea of what size my roof would need to be to handle a 2 kwh system vs a 10 kwh system. I know that some panels do better than others.

Unless your roof is more than 10-15 years old putting pv on should not be a big factor, the solar will be there for 25-30 yrs, so roofs with more than 1/2 the life gone should be evaluated. Installation crews should not be damaging any roof. If the shingles are hot we put down a white cloth to keep them cool and protected from walking.

I am not a fan of solar shingles, the amorphous ones are not efficient and the crystallized silicon ones are too expensive. Plus the wiring is a nightmare. Standing seam metal roofs are great for pv panels as they can be clamped to the seams without rails.

 

[DaveH9]

We seem to have attracted a technical expert or two!

Question:
On my 200KW project the inverters were 11-12% of the project cost, i.e., very, very low six figures. When I look at them they aren't much bigger than a standard 200 Amp panel. Why the hell did they cost so much??????

My installer swears they can be repaired and I'll never have to replace them. True?

True they can be repaired, though "never" need replacing is a stretch. Most come with a 10 yr warranty, PA systems should be close to or past break even by then. Their cost is dropping pretty steadily, as electronics tend to do, so replacement costs are expected to be reasonable. The inverters have a lot of high tech features, balancing the strings, checking for grid voltage, etc. I think they are a good deal overall. Down from over a dollar a watt, to near .50, amazing really.

 

[mbcijim]

We seem to have attracted a technical expert or two!

Question:
On my 200KW project the inverters were 11-12% of the project cost, i.e., very, very low six figures. When I look at them they aren't much bigger than a standard 200 Amp panel. Why the hell did they cost so much??????

My installer swears they can be repaired and I'll never have to replace them. True?

True they can be repaired, though "never" need replacing is a stretch. Most come with a 10 yr warranty, PA systems should be close to or past break even by then. Their cost is dropping pretty steadily, as electronics tend to do, so replacement costs are expected to be reasonable. The inverters have a lot of high tech features, balancing the strings, checking for grid voltage, etc. I think they are a good deal overall. Down from over a dollar a watt, to near .50, amazing really.

I do have a 10 year warranty and my payback is 4 years 3 months, but I am 25% behind production in 7 months, so my payback may have to get dragged out a bit but still very good (65% direct subsidy and a very good REC contract).

If you look at these inverters though I might have 2 pallets worth, for six figures???? What the hell is inside them, solid gold? I don't get it. Is it like Microsoft Office I am paying for the technology?

 

[peakbagger]

I wouldnt assume that inverters can be economically repaired so they last "forever". The manufacturers come out with new models every few years and after awhile I expect that parts and know how to fix them goes away. The "brains" of the units are cutom burned microprocessors so the chances that an indepdent repair person can diagnose and repair are low. Most long term solar folks say plan on replacement ever ten years and hope they last longer. I have a whole house surge protector on my main panel plus lightning arrestors on both sides of my inverters to try to protect them and am actively looking for a better lightning arrestor with lower clamping voltage than I currently have.

I had one warranty covered fault on my inverter within a year of install and my friend with the same brand has had warrantee replacements due to intermittent faults related that were fixed under warranty in 4 years.

 

[pring7]

Would this be an equivalent American company, or are these a different type? (broken link removed to http://www.greenstoneslate.com/solar.htm)

I like the look of the Brit company’s solar slate shingles. My impression is that they are not as effective at the standard panel, or am I mistaken?

It’s an exciting technology and if my roof were in need of replacing I would like to upgrade it.

I think from all of your feedback I am leaning towards designing the barn with solar panels in mind and putting the panels on a metal roof.

I doubt my wife would like the metal roof on the house, so maybe one day when the house needs reroofing I will be able to do a solar shingle/slate design.

 

[jdemaris]

Jdemaris: It looks like you have about 30 panels, and that’s a 6 kwh system? I would like to get an idea of what size my roof would need to be to handle a 2 kwh system vs a 10 kwh system. I know that some panels do better than others.

Here are some solar panel sizes. There isn't much difference between brands when it comes to watts per square foot - 11-14 watts per square foot. The bigger and higher voltage panels tend to be a little more compact. For 2KW of panels, you'd need around 145 square feet.

200 watt Kyocera - 39†X 56â€

175 watt Kyocera – 39†X 51â€

120 watt Kyocera – 26†X 56â€

120 watt Evergreen – 26†X 62â€

On any roof, the panels have to be spaced away from the roof material to allow air-flow, for cooling. For myself, I'd never consider going over anything but a steel roof.

 

[benjamin]

This has been very insightful. I am leaning against doing this problem for now because I don’t want my roof torn up or leaking. The guys I used for the evacuated tube system did a good job, but I can imagine that a larger PV system would involve more trips to the roof and more shingle stones coming off. I think that maybe one day when the roof needs reroofing I will look into the solar shingles.


I think that the idea of designing a barn/boat house with a good angle (30 degrees) would be the way to go. Would the consensus be that the panels are best suited for a metal roof? I had a metal roof on my house in Georgia and I think that is a good fit for my barn project.


Jdemaris: It looks like you have about 30 panels, and that’s a 6 kwh system? I would like to get an idea of what size my roof would need to be to handle a 2 kwh system vs a 10 kwh system. I know that some panels do better than others.

I am not a fan of solar shingles, the amorphous ones are not efficient and the crystallized silicon ones are too expensive. Plus the wiring is a nightmare. Standing seam metal roofs are great for pv panels as they can be clamped to the seams without rails.

Oops, I didn't mean to recommend solar shingles or the "stick on" collectors on steel. Overlapping the tempered glass to form the watertight roof is what I was suggesting, like this:
http://www.solexenergy.co.uk/

Or using the steel itself for the absorber plate in an unglazed warm water seasonal storage collector.

I thought I had seen a website of a firm that did PV roofs the same way but I couldn't find it.

And since I'm so far out in left field already, my completely inexpert take on inverters is to compare them to inverter welders, some of which have proven to be reliable and repairable, and some are disposable. I have a well used Lincoln that I fully expect to last longer than I do, but I sure wouldn't waste $500 on an inverter welder from the fine folks at Harbor Freight.

 

[jdemaris]

I'm so far out in left field already, my completely inexpert take on inverters is to compare them to inverter welders, some of which have proven to be reliable and repairable, and some are disposable. I have a well used Lincoln that I fully expect to last longer than I do, but I sure wouldn't waste $500 on an inverter welder from the fine folks at Harbor Freight.

The "inverter welders" are totally different devices than inverters used to turn DC current into 120 or 220 VAC.

An "inverter welder" uses AC house current, runs it though rectifiers to "convert" AC to DC, and then uses a device to step down and control that DC current for welding. I think the title of "inverter welder" has caused some confustion.

The device much more commonly known as an "inverter" makes DC current into AC and does so with either a true 60 cycle sine-wave - or a simulated sine-wave. This is what's used in solar. An off-grid setup can use a much cheaper, and usually more efficient simutated wave inverter. If grid-tie -the power made must almost perfectly replicate grid-power with a true Hertz Cycle. Subsequently, inverters used with grid-tie tend to be very expensive, and complicated.

You can buy a simulated-wave 2000 watt inverter (3500 watt surge) for $150. A true sine-wave 2000 watt inverter certified for grid-tie can cost $1500-$2500. A non-grid-certified true sine-wave inverter rated at 2000 watts can be found for $400-$600.

Ironically, the cheap simulated-wave inverters tend to be very reliable and more efficienct then the true sine-wave units.

 

[benjamin]

Would this be an equivalent American company, or are these a different type? (broken link removed to http://www.greenstoneslate.com/solar.htm)

I like the look of the Brit company’s solar slate shingles. My impression is that they are not as effective at the standard panel, or am I mistaken?

It’s an exciting technology and if my roof were in need of replacing I would like to upgrade it.

I think from all of your feedback I am leaning towards designing the barn with solar panels in mind and putting the panels on a metal roof.

I doubt my wife would like the metal roof on the house, so maybe one day when the house needs reroofing I will be able to do a solar shingle/slate design.

I'll assume this is my question. That looks similar to the link I posted. Hot water panels commonly come in 4'x10' sizes that could easily be redesigned and built to interlock and form the roof surface. I couldn't find the site I thought I remembered (German) that had installations with standard size or larger PV that interlocked (or overlapped) to form the whole roof surface.

I'm assuming the "slate" panels are similar efficiency, but at a significant price premium over standard panels, even including the savings in mounting and roofing. Plus the hassle of additional wiring as previously mentioned.

 

[benjamin]

I'm so far out in left field already, my completely inexpert take on inverters is to compare them to inverter welders, some of which have proven to be reliable and repairable, and some are disposable. I have a well used Lincoln that I fully expect to last longer than I do, but I sure wouldn't waste $500 on an inverter welder from the fine folks at Harbor Freight.

The "inverter welders" are totally different devices than inverters used to turn DC current into 120 or 220 VAC.

An "inverter welder" uses AC house current, runs it though rectifiers to "convert" AC to DC, and then uses a device to step down and control that DC current for welding. I think the title of "inverter welder" has caused some confustion.

The device much more commonly known as an "inverter" makes DC current into AC and does so with either a true 60 cycle sine-wave - or a simulated sine-wave.

Some inverter welders produce DC, but as I understand it, some take AC, convert it to DC, and "invert" it back to AC, but I don't build the things, I just read the propaganda.

 

[jdemaris]

[Some inverter welders produce DC, but as I understand it, some take AC, convert it to DC, and "invert" it back to AC, but I don't build the things, I just read the propaganda.

I wouldn't want one, but for me - the weight and size of the welder is a non-issue and I suspect the inverter-welder's only claim to fame is being lighter.

I'll take a good old fashioned Century, Miller or Lincoln AC/DC welder any day - with nice big wire-wound transformers and big rectifiers. AC 60 cycle current in and my choice of low voltage AC or DC out. I've got two that I bought used in the 1970s and never had a problem with either. I also have one from the 1940s that still works fine but it's huge.

Now when it comes to portable fuel-driven electric generators, the inverter generators have a huge advantage over the cheaper AC uniits. Since they start out making DC, and run it through a sine-wave inverter - they can make 60 cycle 120 or 220 VAC current at any RPM. AC units must run at one pre-set high speed to make proper cycles and often make imperfect AC power that will not work with all applicances.

Back to solar, many grid-tie inverters are extremly complicated and go way beyond what a simple non-grid inverter does. That isn't necessarily a good thing. A lot of extra complication without a lot of gain to show for it. You'll also notice that they tend to get smaller over time. That's because of the higher DC voltages being used at the imput. The higher the DC power is going into the inverter - the less windings it needs to step up the voltage. If you feed an inverter with 12 volts and want 220 VAC coming out of it, a lot of wire-windings are needed. Feed 600 volts DC into an inverter and have 220 VAC coming out - and the inverter can be much smaller. Not as generally useful though.

 

[mbcijim]

The device much more commonly known as an "inverter" makes DC current into AC and does so with either a true 60 cycle sine-wave - or a simulated sine-wave. This is what's used in solar. An off-grid setup can use a much cheaper, and usually more efficient simutated wave inverter. If grid-tie -the power made must almost perfectly replicate grid-power with a true Hertz Cycle. Subsequently, inverters used with grid-tie tend to be very expensive, and complicated.

You can buy a simulated-wave 2000 watt inverter (3500 watt surge) for $150. A true sine-wave 2000 watt inverter certified for grid-tie can cost $1500-$2500. A non-grid-certified true sine-wave inverter rated at 2000 watts can be found for $400-$600.

I love this place. Great, great, great info thank you.

Can you use a non-grid certified inverter on a system that backfeeds onto the grid?

 

[peakbagger]

The device much more commonly known as an "inverter" makes DC current into AC and does so with either a true 60 cycle sine-wave - or a simulated sine-wave. This is what's used in solar. An off-grid setup can use a much cheaper, and usually more efficient simutated wave inverter. If grid-tie -the power made must almost perfectly replicate grid-power with a true Hertz Cycle. Subsequently, inverters used with grid-tie tend to be very expensive, and complicated.

You can buy a simulated-wave 2000 watt inverter (3500 watt surge) for $150. A true sine-wave 2000 watt inverter certified for grid-tie can cost $1500-$2500. A non-grid-certified true sine-wave inverter rated at 2000 watts can be found for $400-$600.

I love this place. Great, great, great info thank you.

Can you use a non-grid certified inverter on a system that backfeeds onto the grid?

The fast answer is NO. Your utility ahs the right to dsiconnect you, and your insurance will be null and void if the unti harms anyone while it is in operation.


Now for my Soapbox comment

I dont particularly agree with the description of the difference and uses between and on grid inverter and an off grid inverter. Most off grid system use true sine wave inverters. The term" simulated sine wave' isnt generally used in PV parlance. There are Modified Sine Wave (MSW)inverters that produce a square wave, some with rounded corners but nowhere close to a true sine wave. When used on many electronics and electric motors, a modified sine wave inverter may work, but can cause damage over the long run to the equipment. Home Power magazine, the gurus of off gridding used to maintain a list of equipment that would not work off grid on MSW inverters. Additionally the warranty on equipment may not apply to equipment supplied from modified sine wave inverters. Sure MSW inverters are cheap as they dont need much for internal electronics. True sine wave inverters are more expensive as they require more sophisticated electronics and are usually built for long term use. They create a sine wave that is essentually identical to utility power.

A grid tie inverter is always going to be a true sine wave inverter, but since its synched to the grid it can in theory be less complicated than an off grid unit as it can use the utilities wave form to create its output. The actual grid tie electronics can be programmed into a IC chip that is probably being used for other purposes inside the unit. There is additional cost in that a grid tie inverter has to have an internal GFI interlocked with the unit to shut it down if there a DC current leakage to ground (potentally highly dangerous). An off grid unit doesnt legally need one yet, but if someone gets zapped with a high voltage DC leakage from the panels, I guess they saved a lot of money that can be applied to the medical bills or funeral expenses.

So why is a grid tie inverter more expensive that an equivalent output MSW inverter?. I expect its mostly due to the quality of construction. There are no regulated quality control standards for off grid inverters. Any third world country can hack off an existing design, build it with substandard components and design it for limited life. If the unit breaks down, the consumer might return it, and the store or distributor will probably eat the cost as the manufacturer is probably long gone. If equipment gets damaged, the consumer is SOL. If someone gets hurt or their house burns down good luck fiding someone to pay the bills.

A legal grid tie inverter has to be built and tested to UL or some other testing authority. There is a much more likely chance that if it is made poorly, the testing organization will catch the problem and not give it a rating. If there is an issue it it more likely the company will be in business to fix it.

 

[benjamin]

The device much more commonly known as an "inverter" makes DC current into AC and does so with either a true 60 cycle sine-wave - or a simulated sine-wave. This is what's used in solar. An off-grid setup can use a much cheaper, and usually more efficient simutated wave inverter. If grid-tie -the power made must almost perfectly replicate grid-power with a true Hertz Cycle. Subsequently, inverters used with grid-tie tend to be very expensive, and complicated.

You can buy a simulated-wave 2000 watt inverter (3500 watt surge) for $150. A true sine-wave 2000 watt inverter certified for grid-tie can cost $1500-$2500. A non-grid-certified true sine-wave inverter rated at 2000 watts can be found for $400-$600.

I love this place. Great, great, great info thank you.

Can you use a non-grid certified inverter on a system that backfeeds onto the grid?

I think they call that "guerrilla solar" because there's little chance that you'll get caught with an un-permitted, small, grid tied PV system because there's just so little change in the power usage. I think that as the PV industry has become more mainstream (lucrative) there has been less talk of the wild and wooly days.

That's good to know the difference between grid tied and off grid inverters, I would have guessed the opposite, that the more expensive, "certified" grid tied would be more robust. The other use of inverters is wind and hydro, which produce "wild" AC which is fed to the inverter to be converted to 60hz power.

EDIT: oops, what he said