Well based on my old nameplate rated output 5.6 KW system in Grand Junction, using a fixed array at 35 degrees at due south yielded about an annual output of 11,500 to 12,0,000 KW. I had it going for 7 years and that was about the average. About 1500-2000 KW more than what they said it would actually produce which I guess is common in this climate. I thought I would get that and maybe a bit better up here since the air is clear and we don't have inversions in the winter like GJ does all the time which really knocked the output down. It is usually bright and sunny most of the year. I think 300 plus days of sunshine is what the Chamber likes to boast on and I would not disagree at all. My roof is a 9/12 pitch, so approaching almost ideal 39 degrees for our latitude. I am also dead on 180 south.

I will have to take back what I said about just opening the windows at night for cooling during the summer. You live in a "hot box" over there in Carbondale, with 1106 cooling degree days compared to 104 here in Salida. You should move to the mountains of Colorado where the summers are cool!

Changing topics a bit:
I ran some numbers in the latest version of PVWatts for some areas here in Colorado, with the following results for annual output of a 1-kW PV system oriented due south with a tilt equal to the latitude, with the following results:
Grand Junction 1572 kWh
Carbondale 1106 kWh
Salida 1559 kWh
I have measured 1830 kWh per kW DC rating for average annual output on two systems in Salida with an orientation just off optimal. or 17% above this PVWatts value.
beetle55 reported 2058 kWh in Grand Junction, or 31% above this PVWatts estimate.
PVWatts seems to think that Carbondale will have much lower (by 30%) PV outputs than a similar system in Grand Junction. The weather patterns vary locally around the mountains, so accurate estimates are difficult.

Going completely off topic:
We were just starting to cross-country ski up the road leading to Independence Pass from the east side, which leads on to Aspen and Carbondale on the other side, last winter at this time when a fellow who might have been from the Middle East pulled up to the road barrier at the end of where they plow. He said that his GPS indicated that Aspen was just up the road a bit, and he wanted to know how to get there. With about 2' of snow on the road ahead, and much more up toward the pass, we told him that he would need to head back to I-70 to get across the divide. He kept insisting that his GPS said that Aspen was just up the road, and he was not a happy camper!

Dana1-
Better get out the down comforter.

I just got off PV watts and got a bit of a different output Lee. In Grand Junction I got an estimated output from a 1kw rated system de-rated the default 77% and came up with a output of 1529 KW versus 1469 for Carbondale. That is a 4% decrease and not 30%. Was that a typo you did or am I missing something? But like I think you have found in Salida, the PV watts under estimates the power production of the array. Maybe the de-rate that they use as a default is to much? Also, don't forget that I am almost 600 feet higher than Carbondale as well for what little bit that may help. They actually call Carbondale the Banna Belt of the Roaring Fork Valley. Seems like it is sunnier here than Aspen or Glenwood Springs especially.

Yea that is a funny story of the fellow that tried to go over the pass in the winter. We get that a lot in Marble, where Scholfield pass leaves and then goes over to Crested Butte. We have actually had some Semi truck drivers try to go and then get stuck on the first bad hill right outside of Marble and then they blame it on the GPS!!! LOL.

Oh I made a typo on that last post. The name plated rating was 6.56 KW. Not 5.6. But the system still should have only done 10,033 there. But it produced a good 15% to 20% more at 11,500 to 12,000kw! I loved it.

Oh I made a typo on that last post. The name plated rating was 6.56 KW. Not 5.6. But the system still should have only done 10,033 there. But it produced a good 15% to 20% more at 11,500 to 12,000kw! I loved it.

Posted By beetle55 on 02 Jan 2014 08:04 PM
I just got off PV watts and got a bit of a different output Lee. In Grand Junction I got an estimated output from a 1kw rated system de-rated the default 77% and came up with a output of 1529 KW versus 1469 for Carbondale. That is a 4% decrease and not 30%. Was that a typo you did or am I missing something? But like I think you have found in Salida, the PV watts under estimates the power production of the array. Maybe the de-rate that they use as a default is to much?

You are correct that the value that I gave for Carbondale was incorrect. I got the wrong Carbondale. The corrected value should be 1469 kWh/kW rating/year as you reported, which is actually computed for Eagle, or 1354 kWh/kW rating/year if using the interpolation scheme from Clean Power Research using pvwattsbeta.nrel.gov/.

Using your corrected rating of 6.56 kW DC, that would give a normalized output of 1791 kWh/kW rating/year, which is 22% above the PVWatts value of 1469, right in line with what I have seen here. SunPower, which makes the panels that I have, recommends a derating factor of 0.835 for their panels rather than the PVWatts default value of 0.77. Both of those values are for new panels, and do not include age derating. Even using the higher derate factor, my panels have been producing more than the PVWatts values (http://www.residentialenergylaboratory.com/rel_energy_use_pv.html). ‎

What model of Sun Power panels do you have? I had the Sunpower 205's. 32 of them on a ground mount. Seemed to put out the same amount of power on year 5 than the first year I got them and if they had lost some, I didn't notice it.

I am considering them again, but they come at a premium cost and these guys in town are telling me several thousand dollars more for those versus the cheaper ones. Not sure if it is worth the additional money, especially given that I am going to be beyond maxed out on the budget that is starting to scare me some.

Lee- down comforters are FOR REAL!

The 30-40mph winds shifted direction earlier than predicted last night, so the temps bottomed out at about -2F instead of the predicted -5F, but it looks like the high for the day is still looking like it'll be in single digits (it made it all the way up to +7F, before noon, but it's starting to fall back a bit.) But with the filtered sun and no wind it's feeling like heat wave compared to yesterday! Sub zero temp events are definitely qualitatively different in maritime climates than at altitude, where the peak low temps are due to radiational cooling rather than arctic air masses moving down from Hudson Bay, colliding with warmer air with major wind & precipitation. It's hard to say due to the drifting, but it looks like something in the neighborhood of a foot of fresh snow, but at least it was the 6-8% fluffy stuff rather than the typical 12-15% maritime sludge.

By the numbers it looks like you're in for a bit more PV output than I had anticipated in my WAG. A nighttime ventilation strategy still works in Carbondale (or 600' above), even if it's not as optimal as over the hill in Salida. The highest nightly low temp from last summer was about 61-62FF according to Weatherspark data sets, and even on those nights the outdoor temps were at 75F or below before 11PM. On days like last July 11th when it hit the mid-90s during the day, it was below 75F by 8PM. With no latent load to speak of, opening the windows when it falls to 75F is just fine from a comfort point of view. A lot of those peak cooling days with highs in the 90s have 35-40F diurnal temperature swings, with nightly lows in the 50s.


It looks like the 2013 average rooftop grid-tied installation in the US came in a hair under $5/watt, with 60% of it being the "soft costs". Georgia Tech & RMI recently co-published a breakdown of the soft costs focusing on the labor content, downloadable from the RMI site:

http://www.rmi.org/PDF_reducing_solar_pv_soft_costs

http://www.rmi.org/cms/Download.aspx?id=10858&file=2013-16_SimpleBoSRpt.pdf

Posted By beetle55 on 03 Jan 2014 12:26 AM
What model of Sun Power panels do you have? I had the Sunpower 205's. 32 of them on a ground mount. Seemed to put out the same amount of power on year 5 than the first year I got them and if they had lost some, I didn't notice it.

I am considering them again, but they come at a premium cost and these guys in town are telling me several thousand dollars more for those versus the cheaper ones. Not sure if it is worth the additional money, especially given that I am going to be beyond maxed out on the budget that is starting to scare me some.

The SunPower panels that I have are rated at 225 W each, with 14 panels for a total of 3.15 kW. That is barely sufficient to get me around net-zero source energy (including the natural gas for heating).

I have been monitoring the performance of three PV systems here in the Salida area, my SunPower monocrystaline Si, a Sharp mono-Si, and a REC poly-Si. Details are given at http://www.residentialenergylaboratory.com/comparison_of_pv_systems.html. The first two are at the same azimuthal angle and tilt, and the performance normalized by the DC rating is about identical. The normalized power values for the Sunpower system for the first three years were 1807, 1837, and 1788 kWh/kW rating. Comparable data for the Sharp system only covers the second two years, with readings of 1851 and 1795 kWh/kW rating.

The third system, the REC poly-Si, is at a flatter tilt and different azimuth angle, so I can only make comparisons using PVWatts to account for the orientation difference. Compared to PVWatts, the three systems were higher than PVWatts by 22.6%, 23.5%, and 18.9% during year 2, respectively, and by 19.3%, 19.8%, and 12.7% for year 3. Year 3 had more snow, and that could be the cause for the poorer performance for system 3 in year 3, especially when you note that the drop in performance was during November and December.

I do not have data over a sufficient time to comment on aging. The data that I do have, plus the general opinion on the Arizona Wind-Sun forum, is that if space is limited, then include panel efficiency in the decision, but if dollars are limited and space is not, then make the choice based on rated power per dollar. SunPower panels are high in efficiency, but that does not matter unless space is limited.

Yea I heard that $4 to $5 a was a national rate. WOW!!! I guess we are really lucky here in Colorado where about 10 or so years ago there was a vote on the ballot and changed the law to require the power companies to provide a certain amount of renewable power by a target date like maybe 2020 or something similar. Anyway that resulted in huge rebates for us. So here is how the rebates work for me here:

6 KW, basic economy panels, installed on roof top: $21,000 up front cost MINUS 9k from Holy Cross energy, MINUS 3k from local county rebate program called CORE, MINUS 3k in federal tax credit equals a net cost of $6000 to me!! And then if I subtract a couple thousand off for not having to burying a large propane tank in the ground, then its even cheaper then that! I call that a smoking deal. That is a quick payback time. I don't know why more people are not doing that. I called five different shops around here and got the same rough up front cost from all of them so I know that is correct info.

Oh guys, I tired that opening and closing windows, just wasn't quite cutting in for a while here when its consistently hot. During the warmer months it works great and that is my plan for warm months in the future in my new house. Last summer, when it was hot, it did work some, I mean yea I lived and didn't die of heat stroke)) but it was not comfortable for a solid month if I remember at least.

Maybe because the house is in the sun all flipping day and has poor insulation ?? as it doesn't have a massive amount f east and west facing windows. But it hit 80 in the house pretty easy, even with the windows down after the temps dropped low enough. It does however a lot of south facing windows, but none are in direct sun. I suspect ventilation was more of an issue though in the evening as I felt I could not move enough air thru to cool the inside of the house down enough. I wake up and its still around 67-70 degrees in the house when its high 50s or low 60s outside. Anyway, I only have one more summer to contend with that hopefully and then I am out!

Sounds like you are in for a whopper of a storm Dana!

Cheers

Just to be complete, I should mention that the comparisons to PVWatts include an aging degradation factor of 0.65% per year. That is my estimated value based on the 80% performance guarantee after 25 years. PVWatts normally does not include any aging degradation factor.

Yes that makes sense, I am getting a little jammed on space, but looks like I can fit the 6kw array on the roof just barely. That is using the cheaper panels. The rebates stop at 6kw by the way But if I am using the minis for heating and a little for cooling, the electric hot water, etc. then I expect I am going to need the 6kw. Yes I did notice a drop in the winter, and I think some was due to snow, however mine as you know where black and they did burn the snow of fairly good. When I would remember, I would go out there and brush all the snow off, but I know there were days I missed doing that. Also though I know part of that drop was those nasty inversions where it looked like a nuclear winter for weeks on end sometimes. That for sure had an impact.

Posted By Dana1 on 03 Jan 2014 12:06 PM
Lee- down comforters are FOR REAL!

I was living in Connecticut when a bad storm knocked out the electrical power and our heat for 8 days. On the first day of lost power, we happened to receive a thick down comforter sent out a week earlier by my mother-in-law. Down comforters are for real.

I agree with your opinion that the winter weather can be more obnoxious in New England than out here in the mountain valleys. It gets cold at night here, but the next day the sun is usually out, and it seems like the local kids are out running around in shirt sleeves. Not many trees in the dry valleys, and lots of sunshine with high diurnal temperature changes makes the days more bearable unless the wind is blowing. Windy evenings are another matter. The wet sloppy snow combined with ice makes roads there nasty relative to what we usually get here.

Your data makes me think that trapping the cool night air in Carbondale might work pretty well as a cooling strategy. It is necessary to have a well insulated house for that to work well, and to be willing to use shades to block the direct solar radiation. It does not require much effort (in a well insulated house) to make it work in Salida.

beetle55-

I noticed earlier in the thread that you were going to rely on passive solar to meet some of your heating needs. At the risk of telling you what you already know, I will make my usual pitch to make sure that you are getting high solar gain, low-e windows. In this part of Colorado, they stock only low solar gain, low-e windows, so you might need some extra time to special order the high gain windows. The costs are essentially the same for either type, but delivery time can be an issue. My windows have a SHGC of 0.49 (NFRC whole window ratings), and they are working great today.

Thanks Lee, I am 6 months out from putting windows in at the earliest, but thanks for the heads up on ordering them. I thought that might have been an issue, but thanks for letting me know that it is.

A less well insulated leaky house with a high-gain roof and west-facing windows can be pretty miserable compared to an R50+ attic, high-R walls, overhangs on the south windows to limit summertime gain, and little to no west facing glass. A pretty good mini-split or two can keep most of the latter type house reasonably comfortable even if it's sized primarily for the heat load.

I keep hoping somebody will release the vacuum insulated glass (VIG) in a residential product this year, which wouldn't have any of the altitude related issues that gas-filled double panes have, and would outperform all but the very best triple-panes on U-factor. With two hard-coat low-E surfaces the VIG double panes hit about U0.08 at center-glass (better than R10), half the U-factor of run of the mill triple panes. There's lots of industry buzz out there, but I've yet to see it in a real off-the-shelf product. With half the U-factor you can go pretty big on the windows oriented for the desirable winter gain without running into excessive peak heat load issues. It feels like a revolutionary product in the wings, but I'm not holding my breath in anticipation.

This week's nor'easter wasn't anything too special for a winter storm except for the unusually cool temperatures. Most years we'll get a least a couple of similar storms with a foot or better of snowfall- often the sticky heavier maritime cement-mixer stuff. Every couple of years or so we'll get over 20" out of a single storm, and IIRC we've had in excess of 25 out of at least one of those events in the past 5 years. But temps are typically 15-25F during those events , not the -2F to +8F cooth of the past 24 hours. Tonight it'll be somewhat clearer air, so we'll get some radiational cooling- the forecasters have backed off a bit from their -10F, but we'll see. It's supposed to hit around +20F tomorrow afternoon before dropping back, then break freezing by a few degrees on Sunday. Today looks and feels a bit like MN or WI midwinter weather, Sunday will probably feel like "springtime in Winnipeg".

I do not have data over a sufficient time to comment on aging. The data that I do have, plus the general opinion on the Arizona Wind-Sun forum, is that if space is limited, then include panel efficiency in the decision, but if dollars are limited and space is not, then make the choice based on rated power per dollar. SunPower panels are high in efficiency, but that does not matter unless space is limited.

As a relatively seasoned solar designer/estimator I'd just like to confirm your statement Lee. Solarworlds come at a premium $$$. They are one of the tools to use when trying to maximize solar production at a given site. But 1kW of solar world modules will produce essentially the same as 1kW of any other high quality solar module. But it can fit in a smaller space. We get a lot of clients that are hung up on getting the "most efficient" solar PV systems. I try to make sure our clients understand the difference between the most "efficient" system, and the most "cost efficient" system. At least this is the way I approach the subject. Not trying to derail this thread, which has been quite a good read.