Went solar

[orezok]

Just to throw one more curve ball. When we calculated our ROI, you have to calculate in Loss of Opportunity costs. That is $1.00 today is not $1.00 at 8 years or whatever is calculated as the break even. It might be 10, 12 or even 15 years in real dollars for break even.

 

[sodamo]

You are the one that blew off my legitimate question about how long will it take to pay for itself with a flippant remark about how long will I be paying the power company.

Poorly phased- probably
Flippant- no way

 

[clemsonfor]

The industry warranties for degradation tend to be 90% of rated value at 10 years, and 80% of rated value at 25 years. My panels (Sharp ND-216U1F) have a 25 year limited warranty. Their rating is 216 Watts with an initial tolerance of +10/-5%.

The data sheet for the panel also has temperature coefficients for the panels. The panels have their ratings at 25 degrees C. The panel I have has a derating of -0.485% per degree C. The data sheet does not state if this temperature is ambient or the surface of the cells. I'll go out tomorrow and measure my ambient vs. cell surface temperature so we can put a number on that.

So at 77 degrees F (25 C), the panel in "full light" makes 216 Watts of power. At other temperatures:
90F makes 208 Watts
100F makes 203 Watts
110F makes 197 Watts
120F makes 191 Watts
448F makes no power (and I suspect the plastic on the back is melting )

The temperature derating is linear, and I suspect it's only good for real planet tempuratures not the extrapolated zero power out point :laughing:.

Note also that as the temperature goes down, the output goes up. So:
50F makes 226 Watts
32F makes 242 Watts
0F makes 260 Watts

And again, there is probably a limit on this end too. Temperature has other effects on copper interconnections used. Temperature cycling is probably also a prime means of wear out, even though it takes decades. For here in North Carolina, I'll see an output range between 242 and 200 watts for my 216 watt rated panels. The "110 degree and they stop performing" doesn't make a lot of sense, and I suspect there is other criteria applied to the system performance that makes that temperature a cut off point (as orezok mentions).

ShenandoahJoe's post points out the difficulty of make decade long or more guestimates on payback periods, a point I danced around on a previous post.

BTW, in the last 24 hours I made 86% of the energy my house needed, and made money to boot! Lower temps means lower HVAC use, this is great time of year!

Pete

If you made 86% of daily use how did you make money you had to still purchase 14% right? or did you make 86% of your monthly requirement today alone?

 

[clemsonfor]

Yeah, as temp goes up you get more recombination of electron hole pairs at the junction. Noise and leakage current, both temperature dependent, impact the device in a function dependent way. I'm also guess that the junction voltage goes up as the temp goes down, just like any semiconductor junction. That's probably another factor in the thermal derating for the PV panels. The data sheet had thermal derating for power, voltage, and current (I just sited power). They did not have a voltage vs. temp curve, either because most consumers might not know what that's about or because at the end of the day it's just a big honking PN junction.

Cool story , didn't know photonic emissions were a leakage detection mechanism. I had a buddy who back in the days of EEPROMS (like the 2704) spent months working on methods of detecting how many electrons _per year_ leaked out of the floating gate. They tweaked the fab process and got it down into the single digits! I know a few more "you wouldn't believe what someone can measure" stories.

Be it electronics or mechanical stuff, it's amazing how thousands of people have spent decades just quietly understanding and improving stuff. I think a lot of people focus on the big break throughs and don't focus on the effect of lots of little 1 to 2 percent improvements.

Pete

You and Robert both just geeked out on me again!!

 

[eepete]

Clemsonfor: We pay 10 cents per KWH for what we use, we make 16 cents per KWH on what we produce. So there is a KWH break even and a dollar$ break even point. So if I make 65% or more of my energy, I'm ahead dollars wise for the day. In the last 7 weeks, I've averaged making 52% of my energy.

All good geeks can outgeeek other geeks in the own geeky area.

Temperature data I just took (all in F). It was a breezy day, full sun at time of measurment:

Ambient air temp: 67 F
Surface temp of panels (the front side) ranged from 86 to 94 degrees, depending on the amount of wind blowing (it was a breezy day).
Back side of the panels was 104 degrees F.
Measured at the solar zenith, output power of the array was 7300 watts.
Inverter case was at 84 degrees, exhaust air out was 102 degrees.

So in a no wind situation, the panel temp might be around 35 degrees hotter than ambient air. So on a 95 degree day here my 216 watt panels might produce 185 watts. Of course there are errors here since I can only measure the front and back side. Also on those hot summer days the humidity is higher and there is more haze, so the panels put out less. I was still getting 6500 watts out on 95 degree days at the peak. Perhaps the most important number is that from noon to 6 PM, I provided more energy than I used even if all the air conditioners were running. A nice peak load win.

Here's a picture of the watts produced for yesterday and today so far. We have less clouds today than yesterday.

Pete

 

[Boeing]

Hi Guys,
I have the same issue that the fellow on the long road has. The Power com. wants BIG $$ to bring in power. My property is in the Virginia hills with limited sun and shadows. I would be very interested in SOLAR but as I am already 62 I don't want an 18 year "break even". VEPCO will not ALLOW you to go on the GRID with your power.....how's that for progressive? I am now investigating WIND...but I would need lots of batteries for low wind days. That's not cheap either. I see SAILBOATS have small wind generators.....?

 

[beppington]

Hi Guys,
I have the same issue that the fellow on the long road has. The Power com. wants BIG $$ to bring in power. My property is in the Virginia hills with limited sun and shadows. I would be very interested in SOLAR but as I am already 62 I don't want an 18 year "break even". VEPCO will not ALLOW you to go on the GRID with your power.....how's that for progressive? I am now investigating WIND...but I would need lots of batteries for low wind days. That's not cheap either. I see SAILBOATS have small wind generators.....?

Diesel or propane generator?

 

[RobertN]

My Uncle was off-grid when he lived near Mt Shasta. He started out samll as he built his house. 1st, everything was gas. He had a propane fridge, gas dryer, and a few gas lights. He had two large pressure tanks on the well. And, generators. When he ran the generator, you had water, and regular electricity. He would also charge a couple batteries for a small TV, and a couple battery powered lights.

Later, he did add some solar. But for the washer, the well, his welder, lathe ect, he still used a generator.

He was in the mountians, and had shade issues. So, even before he moved back to town because of health issues he used a combination of power and gas(propane and gasoline). He used mostly wood for heating.

there are a lot of regional considerations to solar/wind/water generated power.

Hi Guys,
I have the same issue that the fellow on the long road has. The Power com. wants BIG $$ to bring in power. My property is in the Virginia hills with limited sun and shadows. I would be very interested in SOLAR but as I am already 62 I don't want an 18 year "break even". VEPCO will not ALLOW you to go on the GRID with your power.....how's that for progressive? I am now investigating WIND...but I would need lots of batteries for low wind days. That's not cheap either. I see SAILBOATS have small wind generators.....?

 

[Cat_Driver]

When people figure ROI on solar they never ever calculate the loss of revenue on the money they invested.

Example: Lets say I buy a solar system for 30 K CASH, and it has a 15 year ROI. I could double or triple that 30K in 30 years by hundreds of opportunities.

1. I could buy 30K worth of goods and sell them double my money then take the 60K (30 K doubled), and do it again, and again and again.

2. I could reduce the equity in my house payments and save many, may thousands in interest.

3. I could play the stock market, risky but still I would make money.

4. 30K I could invest in real-estate, peopel are still making money on flipping properties, OR I could use the 30K on a rental property and make the rental income and then the entire price of the property by selling it after 15 years, while the renter make payments of it.

Solar id still way too expensive and the pay backs id too far out for it to be a viable "investment" compared to paying current utility rates and working the solar money.

Now if people think they are saving the planet and that's their goal, then sure solar is the way to go........BUT then you have a few people saving the planet and Billions of people destroying the planet, so it's a no win situation. Sorta of like spitting on a forest fire.

With Mexico, India, China, Russia, and may more Countries duping trillions of tons of carbon in the air, dumping hazardous materials in the oceans by the ship load, there is absolutely nothing the USA can do alone to save the planet, and the others NEVER WILL.

 

[RobertN]

I think it depends on your situation. For us, we pay higher electricity bills than other parts of the US. Locally, there has been good ROI when selling a home.

Given the rate our bills have been rising, I see a shorter term payoff. We added equity in our house.

I guess it's kinda like a diesel pickup. Most people do not get thier investment back from investing in the diesel when they only own the pickup for a few years and low mileage. Definitely not the average owner.

you get the investment back when you have the thing for 300k miles and use it a lot for towing or hauling.

When people figure ROI on solar they never ever calculate the loss of revenue on the money they invested.