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Old 04-18-2015, 02:47 PM   #41
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I looked for other output/temperature graphs for comparison, and even worse than not including numbers on the axis, the graph in this article doesn't even go to zero - and no indication of it. They are zooming in on the relatively small deltas. Pretty misleading.
-ERD50
Did a quick google search, this guy did an experiment.

Effect of Temperature on Solar Panels - Solar

30 degrees celsius vs. 75 degrees is a drop off of 40% in efficiency. So it depends on how hot the roof gets I guess.

It's more of an altitude factor though (high & sunny = still cool), not how close to the equator one is.
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Old 04-18-2015, 03:01 PM   #42
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This is an interesting interactive map:

Mapping Solar Grid Parity in the US : Greentech Media

Without subsidies it shows some states as having reached grid parity today. With the federal tax credit it's basically ok everywhere.

Even more interesting is what happens with further sliding costs five years out (a prediction of course).

[Edit} The application is outdated though. You need to put in current electricity prices (have they gone down?) and current system costs.
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Old 04-18-2015, 04:36 PM   #43
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This is an interesting interactive map:

Mapping Solar Grid Parity in the US : Greentech Media

Without subsidies it shows some states as having reached grid parity today. With the federal tax credit it's basically ok everywhere.

Even more interesting is what happens with further sliding costs five years out (a prediction of course).

[Edit} The application is outdated though. You need to put in current electricity prices (have they gone down?) and current system costs.
Do they show the calcs? Too many of these sights just say it.

I highly doubt that $3.46 installed cost per watt has a reasonable payback in IL. Show me a calculation that would indicate that to be the case.

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Old 04-18-2015, 04:47 PM   #44
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Looking at the map and noting that the article dates from 2013 the numbers the chart shows for 2015 seem high. (for example a nearly doubling of the capacity per year in Tx). Running the numbers for my house in the hill country, it seems the payout is in the 20 year range. (Of course that very much depends on the price of natural gas, which controls the price of regular electricity in Tx , let it go back up to $13+ in 2006 to the mid two dollar range today). (Of course this is what is really killing coal fired power as well)
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Old 04-18-2015, 04:55 PM   #45
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Did a quick google search, this guy did an experiment.

Effect of Temperature on Solar Panels - Solar

30 degrees celsius vs. 75 degrees is a drop off of 40% in efficiency. So it depends on how hot the roof gets I guess.

It's more of an altitude factor though (high & sunny = still cool), not how close to the equator one is.
Sorry, very poorly controlled and amateurish 'experiment'. Doesn't tell us much of anything useful. How does this relate to a panel on a roof? What temperatures will that panel see in various environments (very different from just pushing it to a temperature and taking a reading).

At any rate, it's academic. If the efficiency is so much better at low temperatures, than we would see that reflected in the actual production numbers of solar PV installations in cold areas (or conversely, in very bad numbers in warm areas). But like I said, with shorter days and lower angles during a cold season, those efficiencies won't have much weighting on the annual numbers.

And don't forget that cold weather is often accompanied by snow. I've monitored a local large solar install, and the production dropped to near zero for a week at a time after a snowfall.

So let's see, plenty of sun, cold weather, long days, no snow... should be ideal. Where is that?

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Old 04-18-2015, 06:22 PM   #46
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Do they show the calcs? Too many of these sights just say it.

I highly doubt that $3.46 installed cost per watt has a reasonable payback in IL. Show me a calculation that would indicate that to be the case.

-ERD50
Is the installed cost per watt still over $3 in IL?
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Old 04-18-2015, 06:27 PM   #47
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Is the installed cost per watt still over $3 in IL?
A recent large installation was $3.57/watt.

All flat roof (two large school buildings at different locations in the same town), lots of economy of scale. Far more cost efficient than sighting a single home.


896 Total kW $3,200,000 Installed $

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Old 04-18-2015, 06:36 PM   #48
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A 13 year payback is a 7.6% return on investment, so why not?

If you move out presumably your house has a bigger sale value then as well, since the new owners get a lower electricity bill.
I am not sure they necessarily would add value. They might be like backyard swimming pools, some people might want them and some might not:

Solar systems may not add to resale value of home | Las Vegas Review-Journal

Actually I just updated the calculator again with the correct roof slope direction and the payback time increased a few more years. Plus I am not sure the calculator adds in any upkeep costs. We'd have to have the panels removed and put back on when we replace the roof at minimum, so maybe a new roof needs to be done first. We have some other higher ROI house project to do first, so maybe if we get our kw needs lower and the panel prices come down a bit more it will be a better investment for us a few years out. Our water bill will probably be more than our energy bill this year, so getting the lawns out is more of a priority.
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Old 04-18-2015, 07:19 PM   #49
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While this isn't practical yet I think it will be a game changer in ten years. Imagine large skyscrapers with clear solar windows.


A fully transparent solar cell that could make every window and screen a power source | ExtremeTech


Unfortunately my home state of Nevada has a 3% cap for solar power. It seems like this is a protection for NVEnergy (Berkshire Hathaway). Most utilities have a monopoly because they are so heavily regulated.


Sandoval, NV Energy mum on net metering after meetings with solar officials - Las Vegas Sun News
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Old 04-18-2015, 08:18 PM   #50
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At the time we built out house, we installed a solar hot water system. 4 years later we put in a PV system that reduced our electric bill from $80 - $120 down to $16 - $50, depending on the season.

The federal & state tax credits made the payback period 3 - 4 years, otherwise it would have taken over 25 years.
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Old 04-18-2015, 09:36 PM   #51
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At the time we built out house, we installed a solar hot water system. 4 years later we put in a PV system that reduced our electric bill from $80 - $120 down to $16 - $50, depending on the season.



The federal & state tax credits made the payback period 3 - 4 years, otherwise it would have taken over 25 years.

And would you have made the investment with a 25 year payback?
Why should my taxes subsidize your savings?
Not being personal, just have general, philosophical problem with tax subsidies of this kind.


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Old 04-18-2015, 10:16 PM   #52
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...
The federal & state tax credits made the payback period 3 - 4 years, otherwise it would have taken over 25 years.
Agreeing with CardsFan, but I'll put it a little differently:

The payback is still 25 years. The tax credits didn't change the payback, it's just a shell game of moving the expense from one budget line to the other.


It's like those 'zero pollution' vehicles - heck no, the pollution is moved to another place.

-ERD50
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Old 04-18-2015, 10:34 PM   #53
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I just put four 270 watt solar panels on our homebuilt RV roof here in Seattle. I paid $800 for the panels. I paid $600 for a Midnite Classic 150 MPPT controller and $600 for two Lifeline AGM batteries (125AH each).

$2000 in the 1080 watt max system. Today in the sunshine I measured 755 watts peak, which was quite surprising, seeing as how my panels are flat mounted and the sun is not directly overhead at this time of year at this location.

On a overcast day I was still measuring 200 to 250 watts. In pouring rain I was getting 60 watts.

If I average just 2000 watt-hr per day, that is equivalent to running my Honda EU2000 generator for an hour and burning up 1/4 gallon of gasoline ($0.75) Payback for the system would be around 6 years (at which point the Lifeline batteries would need replacing but the solar and charge controller should still be fine). I am getting no subsidy.
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Old 04-19-2015, 07:28 AM   #54
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[QUOTE=ERD50;1583431


It's like those 'zero pollution' vehicles - heck no, the pollution is moved to another place.

-ERD50[/QUOTE]

+1!!
It is amazing how many people fail to grasp this simple concept.
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Old 04-19-2015, 07:53 AM   #55
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There was a related article in the paper here today.

Earlier this year, Ohio put in a 2 year freeze on "renewable energy standards" and surprise surprise, there was "a steep drop in projects in Ohio".

It's all related into a scheme to force more use of solar, even though it's of questionable economic value given current technology. "The market value of one Ohio solar renewable-energy credits went from a peak of about $400 in 2011 to a current price of $48"

Evidently without government forcing folks to install these systems, there is little demand for them.

Solar energy gets cloudy in Ohio | The Columbus Dispatch

More on the bill:

Senate Bill 310, puts two-year freeze on Ohio's renewable and energy-efficiency standards - Columbus Business First
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Old 04-19-2015, 09:07 AM   #56
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In considering the business case of renewable energy I found these two articles from The New York Times to be enlightening. The first, from 11/23/14 Solar and Wind Energy Start to Win on Price vs. Conventional Fuels provides an overview of the declining price of solar and wind energy over the last half decade. The second, published just yesterday on 4/18/15 Solar Power Battle Puts Hawaii at Forefront of Worldwide Changes relates to the struggles of utilities to adapt to the emerging model of larger numbers of self-producers in Hawaii. I find that interesting, as it is perhaps a micro example of what to expect in future years in the continental US should renewable costs continue to decline.

In my opinion I see governmental incentives as providing encouragement for early adopters of the technology. That is something that has historically been applied to lead to technological advances that have the potential of making improvements for the common good. I did myself have a site survey completed on our property five years ago, with an eye on installing grid-tie solar with a goal of having a net-zero ongoing electrical utility bill. When I had that initial site survey completed, it indicated an approximate 17 year payback, and I deiced not go ahead with it at that time for that reason, the high initial cost of investment, and the concern cited in previous posts regarding the value potential buyers may or may not place on an installed system. A quick review does indicate that waiting has likely reduced the initial cost of installation significantly. Im still not jumping on the bandwagon though, as much as Id like to become more self-sufficient and less economically bound to increasing utility rates. Im geeky enough to like the idea, but still pragmatic enough to need a better business case to proceed and if the articles above are any indication of things to come, that day may be approaching faster than many of us expect.
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Old 04-19-2015, 09:15 AM   #57
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One could make an argument that government incentives slow the development process, since the subsidies allow the developer to make a profit and increase sales without improvements.
Recall how fast plasma and LCD TV's were improved and how fast the prices dropped. Supply and demand drove the research and development, not government incentives.

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Old 04-19-2015, 09:42 AM   #58
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While this isn't practical yet I think it will be a game changer in ten years. Imagine large skyscrapers with clear solar windows.

A fully transparent solar cell that could make every window and screen a power source | ExtremeTech
That's actually kind of interesting. I wasn't going to even look, as there have been so very many of these "Transparent Solar Cell BREAKTHROUGH!!!!" headlines in the greenie web sites, I get kind of desensitized. For geeky fun, search the word "breakthrough" on one of those sites Man, we should all be energy independent now for pennies a day with all these 'breakthroughs'!

But this report is a little different. It is the plastic window that acts as a kind of light-pipe and concentrator to direct light to the edges of the window, and solar cells are only placed at those edges. Efficiency is very low now, but it could have some promise? Windows aren't at the best angle for collecting solar, but if this material itself (w/o the solar cells) isn't much more expensive than normal glazing, it doesn't make much difference. You'd only add as many solar cells as needed to collect that amount of light.


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There was a related article in the paper here today.

Earlier this year, Ohio put in a 2 year freeze on "renewable energy standards" and surprise surprise, there was "a steep drop in projects in Ohio".

It's all related into a scheme to force more use of solar, even though it's of questionable economic value given current technology. "The market value of one Ohio solar renewable-energy credits went from a peak of about $400 in 2011 to a current price of $48"

Evidently without government forcing folks to install these systems, there is little demand for them.
...
Right, if solar was as cost effective as some people are telling us, all us financially literate posters would be jumping on it, but few are, and no one that I know of that didn't get the subsidy (other than for off-grid applications - RVs and vacation homes, etc).

Another thing about these 'par costs'. If solar is to get to high % of grid, then the intermittent nature means you need to add an equivalent amount of peaker plants, or storage. Add that cost to solar, and it rises substantially. And if solar isn't a high %, does it really matter?

-ERD50
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Old 04-19-2015, 09:49 AM   #59
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One could make an argument that government incentives slow the development process, since the subsidies allow the developer to make a profit and increase sales without improvements.
Recall how fast plasma and LCD TV's were improved and how fast the prices dropped. Supply and demand drove the research and development, not government incentives.
Yes, Yes, Yes!!!!

I've been making that argument for years. I worked on emerging technologies, and this is obvious to me. It is the improving technology that makes it affordable, and that increases sales, not the other way around.

For the most part, technology can only move so fast. Engineers need to learn along the way. We could not have made the leap from an 8080 to a quad-core i7 just because someone threw money at it. Each step, the tech gets better, making it valuable to a larger base. And that keeps going, step by step.

Yes, incentives slow the process, they don't speed it up. If a company has a market for the current tech, due to artificial demand based on subsidies, the company has less incentive to improve the tech - they can sell it as is!

Good to see someone else understands this simple fact!

-ERD50
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Old 04-19-2015, 10:00 AM   #60
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I admit to jumping to the end of this thread but how many of the payback calculations figure in the lost opportunity for those funds? Normal engineering economics usually include a calculation where you compare the gain of the investment compared to buying something like a government bond covering the same period. So, if you are looking at a 25 year payback, you have to recover more than the money you put in, you have to recover what you put in plus what you would earn on a "safe" investment. I haven't seen any of these payback calculations include this.
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