Is now a good time to invest in solar?

[russ_watters]

I haven't looked too closely at a solar panel, but I'd think they'd be coated to reduce glare. After all - if they are reflecting light, it isn't being absorbed and converted to electricity!

 

[Artman]

I haven't looked too closely at a solar panel, but I'd think they'd be coated to reduce glare. After all - if they are reflecting light, it isn't being absorbed and converted to electricity!

The surface is low iron "solar" glass material over the bluish-black PV cells. Not much glare.

mheslep, mine are Schott Poly 220 panels.

http://www.schottsolar.com/us/products/photovoltaics/schott-poly/"

 

[Artman]

Just saw my monitor show me 8.811 kw output after the inverter. That's over 100% of the panel nominal capacity of 8.8 kw. Not too shabby.

I wonder if studies have been done on the effects of snow reflectance on solar panel output? The ground is covered with snow, the panels are in cool ambient air and under very clear sunny skies. I really think the snow must help.

 

[mheslep]

Clear day solar insolation on a perpendicular ground surface is http://edmall.gsfc.nasa.gov/inv99Project.Site/Pages/science-briefs/ed-stickler/ed-irradiance.html" .

For NJ at Noon in Feb,
cos(zenith) = sin(φ)*sin(δ)+cos(φ)cos(δ) = 0.61,
where δ=solar declination (Feb) ~ -10 deg, φ=latitude = ~40.3 deg.
Note for June 21 with δ=+23.5, cos(zenith) = 0.96 at Noon.

So received peak power in Feb for a panel facing South at latitude should be ~610W/m^2.

Given 40 panels at 1.67 M^2, total received power by the surface of the array is 41.1
kW. If measured power today was 8811 Watts, then the conversion efficiency of the panels, assuming 94% efficiency for the inverter, is
eff = 8811W / (1.67M^2 * 40 panels * 610W / M^2 * 0.94) = 20.3 %. That's extremely high for a polycrystalline panel.

In June output power after the inverter should hit 12.2kW

 

[mheslep]

From Monday's MIT TR:

http://www.technologyreview.com/energy/24498/?a=f

According to Harry Fleming, the CEO of Acro Energy Technologies in Oakdale, CA, these changes mean that the cost of a typical five-kilowatt rooftop solar system has dropped from $22,000 after state incentives are applied ($40,000 without them) to $16,000 in the last 18 months. Prices are expected to fall to $13,000 by the end of the year ($25,000 without incentives). "This is going to make solar a middle-class product," he says.

Scaling their 5kW typical system to Artman's 8.8kW system gives
with (without state incentives)
$39k ($70k without) - more than 18 months ago [in the ballpark with https://www.physicsforums.com/showpost.php?p=2565045&postcount=41"]
$29k ($51k without) - last 18 months,
$23k ($44k without) - end of 2010.

a 40% price drop, giving $2.6 per Watt-peak for a theoretical 2011 residential system.

 

[Artman]

Clear day solar insolation on a perpendicular ground surface is http://edmall.gsfc.nasa.gov/inv99Project.Site/Pages/science-briefs/ed-stickler/ed-irradiance.html" .

For NJ at Noon in Feb,
cos(zenith) = sin(φ)*sin(δ)+cos(φ)cos(δ) = 0.61,
where δ=solar declination (Feb) ~ -10 deg, φ=latitude = ~40.3 deg.
Note for June 21 with δ=+23.5, cos(zenith) = 0.96 at Noon.

So received peak power in Feb for a panel facing South at latitude should be ~610W/m^2.

Given 40 panels at 1.67 M^2, total received power by the surface of the array is 41.1
kW. If measured power today was 8811 Watts, then the conversion efficiency of the panels, assuming 94% efficiency for the inverter, is
eff = 8811W / (1.67M^2 * 40 panels * 610W / M^2 * 0.94) = 20.3 %. That's extremely high for a polycrystalline panel.

In June output power after the inverter should hit 12.2kW

Thanks for working that out for me (math is not my strong suit).

 

[Artman]

(Does this mean over the following ~34 year lifespan of the system, Artman will make $241,026? Hmmm... Even without the SREC's that's $71,026. Wow. Seems the answer to the original question is: not only yes, but ...)

I was told as part of the sales pitch (so take it for what that's worth) that solar electric generation systems purchased with the current level of incentives will payback $3 for every $1 spent over about 25 years given escalation rates of electricity and expected rise and eventual fall of SREC values. Of course this is just speculation, much of it hinges on the weather. So far it has been the snowiest winter on record where I am. This means lots of cloudy days. Fortunately we have had a few sun on snow days to go with them and the output goes way up then.

 

[OmCheeto]

I was told as part of the sales pitch (so take it for what that's worth) that solar electric generation systems purchased with the current level of incentives will payback $3 for every $1 spent over about 25 years given escalation rates of electricity and expected rise and eventual fall of SREC values. Of course this is just speculation, much of it hinges on the weather. So far it has been the snowiest winter on record where I am. This means lots of cloudy days. Fortunately we have had a few sun on snow days to go with them and the output goes way up then.

I'm very interested in your system voltage vs. temperature. I learned yesterday that most solar panel manufacturer's under-rate their panels, knowing that they have a certain degradation over time. (I'm still trying to figure out how to gracefully retract my "100%" claim from the other day)

I have to admit that I've learned more about solar panels in the last two weeks than I have in the last 4 year. It's easy to ignore the scientific facts when these little buggers appear to be the ultimate "Energizer Bunnys".

But mheslep and I both posted graphs that indicate that ratings on the panels start at 25'C and voltage output degrades as temperatures go up. So my questions are: Do the graphs continue linearly in the opposite direction? Does a panel operating at 0'C give a 6 to 7 % increase in power output? Was it the solar reflection from the snow, or the temperature that are giving you increased power output? Or was it both?

 

[Artman]

I'm very interested in your system voltage vs. temperature. I learned yesterday that most solar panel manufacturer's under-rate their panels, knowing that they have a certain degradation over time. (I'm still trying to figure out how to gracefully retract my "100%" claim from the other day)

I have to admit that I've learned more about solar panels in the last two weeks than I have in the last 4 year. It's easy to ignore the scientific facts when these little buggers appear to be the ultimate "Energizer Bunnys".

But mheslep and I both posted graphs that indicate that ratings on the panels start at 25'C and voltage output degrades as temperatures go up. So my questions are: Do the graphs continue linearly in the opposite direction? Does a panel operating at 0'C give a 6 to 7 % increase in power output? Was it the solar reflection from the snow, or the temperature that are giving you increased power output? Or was it both?

I understand both low temperatures and reflectance can add to performance. I was told that my ground mount system will perform better than a roof mounted system (everything else being equal) because it will be better arranged for air movement to transfer heat away from the panels, since the backs are wide open on a metal rack angled 40 deg up to 12' in the air at the high end from 3' above the ground in the front. Where roof mounted panels lying flat on racks against the angle of the roof tend to gain heat from attic spaces and trap heat between the panels and the roof, driving down performance.

 

[russ_watters]

I'm very interested in your system voltage vs. temperature. I learned yesterday that most solar panel manufacturer's under-rate their panels, knowing that they have a certain degradation over time...

That's not quite right. Manufacturers rate their panels according to a set 3rd party standard. Like any other device, mechanical or electrical, performance will vary based on test conditions, so *someone* has to decide on a standard set of conditions unless the industry is to be a free-for-all. The rating point is then based on a set of conditions near the top of what is likely to be seen, but there is no such thing as perfect conditions, so there is no real set maximum.

Here's an article about the Standard Test Conditions for rating panels (on which, Artman's panel's 220W nominal rating is based).

1.Irradiance (sunlight intensity or power), in Watts per square meter falling on a flat surface. The measurement standard is 1 kW per sq. m. (1,000 Watts/m2)
2.Air Mass refers to “thickness” and clarity of the air through which the sunlight passes to reach the modules (sun angle affects this value). The standard is 1.5.
3.Cell temperature , which will differ from ambient air temperature. STC defines cell testing temperature as 25 degrees C.

http://www.altestore.com/howto/Electrical-Characteristics-of-Solar-Panels-PV-Modu/a87/

Because of #2, #1 seems to me that it should be the irradiance at the top of the atmosphere. The real value varies from 1.321-1.412 kW/sq m, so I would think if you mounted one of these on the top of Mt Everest, it would put out a good 285W. I'm not really sure of what #2 means in terms of real-world conditions, though.

#3 is significantly cooler than what you'll actually get in summer, so that one works against you.

...speaking of which, does anyone make a combo solar water heater and power panel? I'd think that you could collect nearly as much heat as with a regular solar water heater while also significantly improving the electrical output of the panel.

 

[Artman]

...speaking of which, does anyone make a combo solar water heater and power panel? I'd think that you could collect nearly as much heat as with a regular solar water heater while also significantly improving the electrical output of the panel.

Not sure about water, but a company called Solarwall makes a combination PV panel and air preheater duct. Air is ducted behind the panels to cool them while simultaneously preheating fresh air for roof mounted Air handling units.

http://solarwall.com/en/products/solarwall-pvt/solarduct-pvt.php"

 

[Artman]

At 11:45 yesterday, sunny, clear, with snow on the ground temps in the upper 30's deg F, the system monitor showed 9.34 kw output after the inverter. Around 106% of the panels' kw rating. The inverter is only rated for 10 kw. Anyone know what happens should the panels go over that? It's beginning to look like a possibility.

 

[mheslep]

At 11:45 yesterday, sunny, clear, with snow on the ground temps in the upper 30's deg F, the system monitor showed 9.34 kw output after the inverter. Around 106% of the panels' kw rating. The inverter is only rated for 10 kw. Anyone know what happens should the panels go over that? It's beginning to look like a possibility.

The panels will go well over that - to 12kW come a clear day in June/July. I doubt you'll have any problems with the panels themselves, but the inverter concerns me if it is indeed rated 10kW. It must have a breaker or fuse, e.g. UL safety, but it's likely have a shorter life if its run at full or over capacity all the time. Doesn't make sense that an experienced installation company would have given you an inverter underrated for the job.

 

[Artman]

The panels will go well over that - to 12kW come a clear day in June/July. I doubt you'll have any problems with the panels themselves, but the inverter concerns me if it is indeed rated 10kW. It must have a breaker or fuse, e.g. UL safety, but it's likely have a shorter life if its run at full or over capacity all the time. Doesn't make sense that an experienced installation company would have given you an inverter underrated for the job.

I looked up my inverter and checked the ratings. The maximum output is 9995 watts. The maximum input current is 46.7 amps nominal input amps is 27.6 amps. I think my system is wired for 480 volts DC. 12,000 watts/480v = 25. Should be fine. I'm breathing better again.

 

[mheslep]

Hold on, I didn't account for the temperature coefficient before. The SCHOTT data sheet gives a -0.47% / deg C coeff, 20deg C as the rating point. Assuming your Noon temperatures lately have been 5 deg C outside, the panels would run 15*0.47%=7% better than rated. In the Summer, assuming 30 deg C on the roof, the panels would run 10*0.47=4.7% worse, an 11% decline due to temperature from now. So the peak June solstice power for the Artman array declines to ~10.7kW at 30 degC, better when the odd clear cold front comes through.

 

[russ_watters]

I looked up my inverter and checked the ratings. The maximum output is 9995 watts. The maximum input current is 46.7 amps nominal input amps is 27.6 amps. I think my system is wired for 480 volts DC. 12,000 watts/480v = 25. Should be fine. I'm breathing better again.

All motors have a "service factor" of 1.15 that means the true rating is actually 15% higher than nameplate - I suspect your inverter has such a saftey-factor built into its design.

 

[Topher925]

All motors have a "service factor" of 1.15 that means the true rating is actually 15% higher than nameplate - I suspect your inverter has such a saftey-factor built into its design.

There's no doubt a factor of safety, but often operating a device outside of its specified range won't damage it but it may shorten its lifespan.

 

[Artman]

Latest update, the Electric Company estimated our last bill so even after the solar array saved us 750 kwh we got a bill for $160.00. To be fair, there was still a foot of snow on the ground around here, so I didn't expect them to read the meter. My wife called and told them the reading I took on meter reader day and they are going to amend the bill and send out a new one. The Electric Company has been very reasonable through this whole process.

I was anxious to see the difference in the bill after nearly a month of solar power generation. It was an odd month anyway because of snow, clouds, some time left from the old meter, and a few days on the new without solar assistance.

Currently the system has generated over 900 kwh, should earn us our first SREC soon. Then we get to see how that works.

 

[TDE]

good thread, suscribing.

 

[Artman]

We had our first non-estimated bill this weekend. $47 and change for 281 kwh. $15 of that was distribution and connection fees. We are still ending up paying more than expected (the design was for an average bill of $11.00), but it has been unusually cloudy. The hope is that the summer months will help reduce the actual average bill to meet the design.

System has been functioning well with several sunny days just after the last meter reading. We are still waiting for the SREC number to come through. It is tied to the rebate which is tied to the home energy audit, which has to be submitted to the state still (waiting for a computer program code of some sort). The whole energy audit part of the process came as a surprise to me. I hadn't realized at first that a home energy audit was required to get the rebate and the SREC number, but it is.

More later as it happens.

 

[Artman]

The meter-reader came yesterday and found the reading over 300 kwh below the previous month (good sunny month). He said "System failure." I asked him what that meant, he said it kicks out any results too far below the expected average reading. It should be interesting to see the bill. I'll post the outcome.

 

[Artman]

The meter-reader came yesterday and found the reading over 300 kwh below the previous month (good sunny month). He said "System failure." I asked him what that meant, he said it kicks out any results too far below the expected average reading. It should be interesting to see the bill. I'll post the outcome.

On a month with a negative meter reading we got a bill for +- $2 (not sure of the exact amount, it's home, I'm not, my wife told me the total). There are a couple of charges that are based on days tied to the grid rather than kwh used. Those amounted to the +- $2 charge. I can stand that.

 

[mheslep]

On a month with a negative meter reading we got a bill for +- $2 (not sure of the exact amount, it's home, I'm not, my wife told me the total). There are a couple of charges that are based on days tied to the grid rather than kwh used. Those amounted to the +- $2 charge. I can stand that.

By this time of year the utility/panels should be paying you substantially for your excess kWh produced, I would think? No summer air conditioning running yet, and we are <60 days away from summer solstice. I would think May might be your biggest pay off month, unless you don't use air conditioning in the summer.

 

[Artman]

By this time of year the utility/panels should be paying you substantially for your excess kWh produced, I would think? No summer air conditioning running yet, and we are <60 days away from summer solstice. I would think May might be your biggest pay off month, unless you don't use air conditioning in the summer.

Because of the SREC program, I can only sell back a small portion of the excess at this time (about 5% I think). We had about 300 kWh under the last meter reading. We can carry it to the next month, but we won't get back any money for it.

 

[mheslep]

Because of the SREC program, I can only sell back a small portion of the excess at this time (about 5% I think). We had about 300 kWh under the last meter reading. We can carry it to the next month, but we won't get back any money for it.

So you are supplying free power to the grid?

 

[dr dodge]

So you are supplying free power to the grid?

thanks, we all appreciate that...lol

this (IMHO) is why a separate off grid system is all I would invest in. Somehow the power company still wins

Glad your system is working good, and your thread is a great source of info for all

dr

 

[Artman]

thanks, we all appreciate that...lol

this (IMHO) is why a separate off grid system is all I would invest in. Somehow the power company still wins

Glad your system is working good, and your thread is a great source of info for all

dr

Thanks dr. It's doing really good. The main problem right now is that the state still hasn't issued us our SREC code and instructions yet. It is in the works. However, I still think grid tied was the way to go. Our overproduction last month was around 300 kWh.

300 kWh is 30% of 1 SREC. They are selling for about $700 in NJ right now. So a third of an SREC = $210 in NJ.

Electricity is selling for approximately $.17 right now in NJ. so 300 times .17 = $51 in NJ.

Grid tied still looks the best to me. And we carry the credit for the 300 to this month should it be cloudy.

 

[Artman]

Another update. I received my SREC registration number from the NJ Board of Public Utilities. Now I can start selling SREC's. It took about 5 months for the registration to come through from the date of system activation at the end of January. From what I understand, all of the SREC's produced prior to the registration number being issued are still credited to my account and can be sold. It's produced almost 5 now, right about on schedule to make 11 by the anniversary date at the end of January.

 

[mheslep]

Artman - what kind of daily kWh are numbers are you producing now that we are into June?

 

[dlgoff]

From what I understand, all of the SREC's produced prior to the registration number being issued are still credited to my account and can be sold.

Are the SREC's value seasonal dependent? i.e. Can you sell them back on peak times. I would guess not.

 

[Artman]

Artman - what kind of daily kWh are numbers are you producing now that we are into June?

Well, the hot air does do quite a hit on efficiency, our better days are around 49 or 50 kwh (down from 55 or 56 in the early Spring), but we seem to be able to eek a decent output from a longer cloudy day, getting up around 25 or 30 kwh.

Are the SREC's value seasonal dependent? i.e. Can you sell them back on peak times. I would guess not.
Y 04:13 PM

They can be held to be monetized (sold) for the current year plus two years for a total of three years in NJ, so you can wait a while for the price you are trying to get.

I've just began an arrangement to allow an online company SRECTrade.com handle the sales. They charge 3% of the selling price, deal with the buyer and send me a check. I set a low limit (in my case $500.00 per SREC) and they try and get me as high a price above that limit as they can find. If I want, I can handle the sales myself and they only charge the buyer a percentage, but I think 3% to watch the market and find a good buyer is a reasonable charge.

 

[OmCheeto]

Artman, you do realize that it has taken all of my willpower not to flood this thread with little smileys every time you make a post, don't you?

... .. .

No! Don't do it Om! This is the engineering section! They'll give you an infraction!

So, please. Given the SRE's, the cut in your electric bill, and the original cost, what is your current payback time for your investment?

And give us the answer. Was this the right time to invest in solar?

snicker, snicker.

 

[Artman]

So, please. Given the SRE's, the cut in your electric bill, and the original cost, what is your current payback time for your investment?

And give us the answer. Was this the right time to invest in solar?

I'll run the numbers again and let you know. I think with a decent SREC rate, it should be around 5-7 years, worst case about 10 years.

My original question wasn't really so much about the payback as it was the technology. I wanted to know if anyone here knew of any breakthrough technology that would make the old panels obsolete and very much more expensive. If the world was on the cusp of a breakthrough that would drive solar array prices way down or solar efficiency so good that fewer panels could do the same job. If the cost comes too far down, the market will become flooded and SREC prices will drop. Then payback would become an issue. Payback from electricity savings +rebate and tax credit, but with no SRECs is about 20 years.

Was this the right time to invest in solar?

My honest answer is "no." I wish I had done it sooner (when rebates were higher).

I attended an energy symposium where I had to answer questions about residential solar. there were several others there who had solar arrays as well and, from what they have said, all of them are very pleased with their investments. I'll post more about this later, some issues to be aware of came up out of that day.

 

[OmCheeto]

I'll run the numbers again and let you know. I think with a decent SREC rate, it should be around 5-7 years, worst case about 10 years.

My original question wasn't really so much about the payback as it was the technology. I wanted to know if anyone here knew of any breakthrough technology that would make the old panels obsolete and very much more expensive. If the world was on the cusp of a breakthrough that would drive solar array prices way down or solar efficiency so good that fewer panels could do the same job. If the cost comes too far down, the market will become flooded and SREC prices will drop. Then payback would become an issue. Payback from electricity savings +rebate and tax credit, but with no SRECs is about 20 years.

My honest answer is "no." I wish I had done it sooner (when rebates were higher).

I attended an energy symposium where I had to answer questions about residential solar. there were several others there who had solar arrays as well and, from what they have said, all of them are very pleased with their investments. I'll post more about this later, some issues to be aware of came up out of that day.

Not to politicize the engineering forum, , but with the gulf spill going on, I'd say your timing was impeccable.

 

[Artman]

One of the questions asked of the residential panel made up of home owners with solar arrays was: "Knowing what you know now, what would you do differently?"

A man with a huge 28 kw ground mounted array said he would have had it set slightly higher. His is only 6" above the ground at the low end (mine is about 30"). He said snow bunched up around the bottom and he had to clear it.

A man with a 9.5 kw array mounted on the roof of a pole barn said he would ride past mine (he lives close by me) during those days following the heavy snows and see my solar array was clear of snow while his went for weeks with snow on it because the angle was too small (30 deg over horizontal, mine is 40 deg) and the roof was too high for him to clear them. He said If he had it to do over, he would put it on the ground at a steeper angle, similar to mine.

I said I would have done it sooner.

I can understand their answers, my best days were days with snow on the ground and a clear solar array.