I'm considering having a solar panel electrical system installed.

[Rob-D]

Always keep in mind that the sun delivers 1100W per square meter at the earth surface. Unless you can cant the panel to always stay at a rt angle/normal to the rays it will be difficult to harvest from this potential except during the 4hrs [~10-2] of peak sun. [Photoelectrics go from 10% efficiency upward at escalating cost -- greater demand will ultimately deescalate the cost.] During those 4 you can expect about 100W/M2 of finished electrical power. Following the sun would extend the time, esp on clear days. As tech evolves this will become more economical and capable. For now, staying away from hi tech servo, I would use a conservative yearly figure of 400WHrs/M2/day for finished power. Sizing a collector using that figure factored against your average demand should come close to zeroing your grid intertie meter.
... As you know, I plan to stay away from batteries because the grid is reliable and we have gen backup for any severe interruption. -- also an electric golf cart for micro storage.
larry

Larry,
Storage is the weak link in renewables. I thought long and hard about storage s have many other people. There is a lot of work being done in this area, Super capacitors look very good and we're starting to see them in applications like storing gusts in wind mills but they aren't near the capability of a battery yet. When I was in school they used to tell us that a 1 farad capacitor would be the size of a caboose, now they are half the size of your little finger.

Rob

 

[techman]

Always keep in mind that the sun delivers 1100W per square meter at the earth surface.
larry

Actually the accepted figure is 1000w/m^2 at sea level, perpendicular to the sun, at high sun.

paul

 

[SPYDERLK]

Amazing arent they? To put this in perspective for those who are not familiar -- a Farad is 1 Coulomb per volt. A Coulomb is an amt of charge conveyed by 1Amp flowing for 1 second. So ... a 100F 2 Volt rated capacitor would store 200Coulombs at full charge ... 200A for 1 second. Note the low V tho. The stored energy is only 100 W seconds. [Starting a car takes around 3000 W-Sec] -- Their beauty is that they can deliver and accept energy quickly and efficiently, and for a huge number of cycles. At this point in time they are most suited to parallel power functions where an item [motor or incandescent light] requires a momentary huge inrush current that would cause the powerline/gen/PC/batt-inverter to buckle.
...There is rumor that were due to see a tenfold increase in ultracap capability. That will bring more general and wider use.
larry

 

[SPYDERLK]

Actually the accepted figure is 1000w/m^2 at sea level, perpendicular to the sun, at high sun.

paul

Not sure why that is accepted, cuz it isnt correct. Perhaps its 1000/sqyard?

 

[Rob-D]

Amazing arent they? To put this in perspective for those who are not familiar -- a Farad is 1 Coulomb per volt. A Coulomb is an amt of charge conveyed by 1Amp flowing for 1 second. So ... a 100F 2 Volt rated capacitor would store 200Coulombs at full charge ... 200A for 1 second. Note the low V tho. The stored energy is only 100 W seconds. [Starting a car takes around 3000 W-Sec] -- Their beauty is that they can deliver and accept energy quickly and efficiently, and for a huge number of cycles. At this point in time they are most suited to parallel power functions where an item [motor or incandescent light] requires a momentary huge inrush current that would cause the powerline/gen/PC/batt-inverter to buckle.
...There is rumor that were due to see a tenfold increase in ultracap capability. That will bring more general and wider use.
larry

Tenfold would really make a difference. I have 50F caps as big as my thumb that I'm experimenting with, really neat!

I know that Maxell and Agilent (HP) are working togther with Super Caps.

Rob

 

[techman]

Not sure why that is accepted, cuz it isnt correct. Perhaps its 1000/sqyard?

Solar Energy Facts and Information

For a more detailed study: http://www.nrel.gov/rredc/pdfs/761.pdf

paul

 

[SPYDERLK]

Amazing arent they? To put this in perspective for those who are not familiar -- a Farad is 1 Coulomb per volt. A Coulomb is an amt of charge conveyed by 1Amp flowing for 1 second. So ... a 100F 2 Volt rated capacitor would store 200Coulombs at full charge ... 200A for 1 second. Note the low V tho. [[[The stored energy is only 100 W seconds.]]] [Starting a car takes around 3000 W-Sec] -- Their beauty is that they can deliver and accept energy quickly and efficiently, and for a huge number of cycles. At this point in time they are most suited to parallel power functions where an item [motor or incandescent light] requires a momentary huge inrush current that would cause the powerline/gen/PC/batt-inverter to buckle.
...There is rumor that were due to see a tenfold increase in ultracap capability. That will bring more general and wider use.
larry

Im noting an error I made above in simplifying for the cap voltage dropping during delivery of its energy. I used 1V as the discharge V because 1/2 the charge is delivered above and below that. I lost track and got too many 1/2's mixed in. In actuality, Capacitor Energy = 1/2C x V^2 = 1/2x100F x 4 = 200Joules = 200W-sec ... So that cap has stored twice as much energy as I initially stated.
larry

 

[edlegault]

Actually, the accepted figure is 1000w/m^2 at sea level, perpendicular to the sun, at high sun, AT THE EQUATOR.

 

[buckeyefarmer]

I'm actually waiting for a line item on my Electric bill that goes something like "We couldn't think of a new story, so we are just going to stick you with this extra charge because we can !".

Rgds, D.

:thumbsup: :thumbsup:

The enphase inverters look like a very simple install. They have cables with premade connectors (expensive though) that just snap together at each inverter. It's almost a plug and play system. I think it was something like 18 or 20 inverters (1 inverter per panel) on a 240V 30A circuit. The hardest part of the install is getting the permits.

 

[KTurner]

I've been keeping an eye on solar, and don't have a system yet. I just skimmed the thread real quick, but I don't think anyone mentioned this.

Do NOT start by sizing a system according to your current needs. The first step should always be to downsize your current needs. Learn to live with less electricity. Then, size a system accordingly. And when you're looking at payback times, be sure to factor in that your electricity rates will be going up *all* the time.

I've been tracking our usage and bills for about three years. In Nov2010, our bill was $97 for 977kwh, but by Nov2011 our cost had increased so that our bill was $104 for only 900kwh - 7% higher bill for 8% less electricity used. The local power company is going to shutdown three coal powered plants in the next 6-8 years, per the EPA, and construct a big transmission line to replace the lost generating capacity with electricity brought in from another area. That's an unexpected (big) cost for them, which I'm sure will result in a jump in my bill that wouldn't be there if they were able to keep burning coal.

It's easier than you think to live with less. I measured our usage to find out what % of electricity went to what for most things (hard wired stuff is harder to measure). For example, our refrigerator is ~12% of our electricity bill (during winter). We have a desktop computer being used as a server for our home network that is about 7% (90 watts, continuous) and I've purchased a network connected external hard drive to replace it with that uses probably 10% of that. I was going to need to replace the server soon, and the new efficient external drive cost less than a new desktop "server" would. We use wood to heat with during the winter. We're probably going to start using a clothes line instead of the electric dryer. In July2011, our usage was 37% less than July2010. The change? I replaced our 26 year old heat pump (~6 seer?) with a new 18 or 19 seer unit.

I've estimated (through elimination) that our water heater is probably 30-40% of our bill. I've also heard that solar water heating is much more efficient than solar electricity generation. If we go solar, it'll probably be solar water heating first, because of this. Our electric water heater would stay in place to provide hot water on cloudy days. I'd like to find out what our actual costs and benefits would be, so I bought a surplus electric meter off ebay to install right beside the water heater. This will eliminate one guess from my payback equation.

I mentioned before the electric costs going up. Also, the solar costs are going down . So your calculations need to include multiple changing variables over time. How far can I lower my electric usage and still live comfortably? What is the average annual perKWH increase in my electricity bill? How quickly does the cost of the solar equipment go down? If not now, when will these three (or more) variables align to give you your desired payback time frame?

Keith

 

[LD1]

It ALL boils down to COP. (cost of payback)

And that (I think this thread illustrated VERY well) is different for everyone.

And there are only 3 things that influence COP:

1. Your electric rates. Mine are 11 cents/kwh But other areas of this country are north of 30, so that right there "could" drop the COP by 3x's

2. Does your utility company offer net-metering. Mine does NOT. So when myself and the wife are at work, and the house is consuming VERY little juice, and its a nice july day that 20-30k system is giving electric away all day to the utility company for FREE. And then at night, when we get home and I take a shower and lay in bed and watch TV and the water heater kicks on, I have to BUY my electric even though I just gave them a TON of kwh's for free earlier that day Crock of S**T if ya know what I mean.

3. The last thing that effects COP is how much the system costs. Grants, credits, tax incentives, local programs, etc all lower the cost. As others have mentioned ~$3/watt if you install yourself is pretty accurate at the moment.

For me, based on my current 11 cent rate and no net metering and $3/watt set-up, my COP is north of 20 years. I am kinda the worst case scenerio.

For others with 30cent+ rates AND net metering, the COP could easially be UNDER 5 years.

Reducing electric use, and/or upgrading to higher efficency stuff does NOT reduce the COP. Because you would benefit from those changes regardless wether you have solar or not. For example, you install a $20k system and anticipate a 10 year payback. And after the first year, you have a major lifestyle change or whatever and are only using 1/2 the electricity and selling the rest back, THAT does NOT cut the COP in half. Because you would have to re-figure how much it would have costed you without solar. And the pre-solar cost would also be cut in half.

You guys get the idea.

 

[KTurner]

Reducing electric use, and/or upgrading to higher efficency stuff does NOT reduce the COP

Decreasing your usage could allow you to purchase smaller (less expensive) equipment, such as the inverter. This may or may not matter, depending on your electric company and the net metering agreement. In a situation where they do not pay you for your surplus, it doesn't make sense to have a system any bigger than what your house uses during the day as that is unused capacity which just increases your system cost and makes it take longer to pay for the system.

Some companies change the rate when you hit a certain number of KWH in a billing period. My electricity company changes the rates at 800KWH. During June-September, KWH #801 costs about 20% more than KWH #799. I could buy just enough of a solar system to keep my bill below 800kwh and the per-kwh payoff would be quicker than if I did a system large enough to supply my entire usage. I'd be targeting the more expensive KWH's. Of course, my electric costs (per KWH) change throughout the year, so that makes the equation a bit more complicated.

You could always just chalk it up to a hobby instead of an investment. Get some new toys and play. There's much less research/homework involved in a hobby versus an investment.

Keith

 

[RobertN]

I figured out how to get back online for our solar. Here is graph of past year, and July 2011. At the bottom of both graphs is an overall lifetime; ours goes back to September 2010. Scale is not good, but can see trend.

One thing I did not see mentioned here....

We reroofed just before the panel went on... We were due anyway. But, as much as we like our results, I would hate to reroof and have to pull these panels up...

 

[RobertN]

Today, so far. Overcast with sprinkles here and there.

I figured out how to get back online for our solar. Here is graph of past year, and July 2011.

 

[LD1]

Some companies change the rate when you hit a certain number of KWH in a billing period. My electricity company changes the rates at 800KWH. During June-September, KWH #801 costs about 20% more than KWH #799. Keith

Mine is actually just the opposite.

The more you use, the less the overall bill is per kwh.

As I mentioned before, I track mine with a spreadsheet. I use about 800kwh LESS in the summer. Due to having a heatpump for primary heat, winter months it runs more than in the summer.

And my winter bills curently are averaging ~10.5cents/kwh for ~2400-2600kwh and they are ~11.5 cents in the summer for 1500-1700 kwh bills

 

[SPYDERLK]

Actually, the accepted figure is 1000w/m^2 at sea level, perpendicular to the sun, at high sun, AT THE EQUATOR.

Actually, the accepted figure is 1120W/M^2; a total of all direct and scattered light on a surface normal to the sun rays on parts of the earth presenting them at a low zenith angle. You will get a great deal of incomplete info unless you include the key "word" 1120 in a search.
larry