Our Solar Electric Panels: Done!

"If there were no utility or tax incentives, the solar power system payback would be ~33 years, which exceeds my personal planning horizon and consequently I would not make the investment now."

Unfortunately, the 33 year time horizon is an argument that is often made by solar naysayers. I do understand that it may not make much financial sense, even though it makes great social and environmental sense. It just illustrates how other energy sources are not paying their entire costs. (see also,,, oil spills!)

As a salve against worrying about 33 year pay backs, one must consider that at a bare minimum energy prices are going to go up over the course of the 33 years. An investment in PV at least insulates one from huge rate increases.

Thank god, (in spite of what the right wingers would argue) for the subsidies! One other thought for those that are considering Pv, (that we have mentioned on other threads). If you can't justify investing in PV/RE on your own house, consider a coop investment in PV/RE such as green power through your utility. A coop is a way to make ones PV/RE dollar go much farther, if the goal is to create the biggest out put for the buck.

Icarus

 

Here are some real numbers to go along with this
argument...

My April 2010 energy usage was 18% less than my
April 2009. This reduction was due to a number of
improvements I made to my home, plus April was a
mild month weather-wise in Missouri.

However...my April 2010 utility bill was not 18% less
than my April 2009; it was only 12% less. This was
because the kWh rate increased by 8%. The rate
increase erased a good portion of the cash value
I hoped to recoup by lowering my energy usage.
By the way, the rate increase the year before that
was 11.6%, for a breathtaking total of 22.6% rate
increase over the last two years!

P.S....Icarus, good pun, "insulates..." :-D

 

And it will only get worse. The problem is we are (collectively) like the frog in the stew pot. The price rises fast enough, bur not quite fast enough for us to act and change our behavior. When gas was ~$4/ couple of years ago, there was a waiting list for Prius's. Now that it has dropped a bit, we are back to buying big SUVs again!

I am currently in the UK, and I just bough petrol for 1.31 L/litre, the USD equivalent of ~$8! No one complains! They drive small cars, car pool, and have a robust public transport system. Even on the remote outter Hebrides Island, you can get a public bus nearly any time of the day to nearly everywhere. You can take trains to connect to ferries to connect to busses so you really don't ever NEED a car! When they do, they drive models not available in N. America. Small TDI Diesels that get ~50+ mpg, even the gas VW Golf I hired gets ~40 mpg, and it is a HUGE car by UK standards. Even the big BMWs are Diesel powered.

 

There are 6.57 average sun hours/day, according to:
Solar power insolation for U.S. major cities

The inverter is SMA 5000US Grid Tied, with online data monitoring.
SUNNY BOY 5000US / 6000US / 7000US / 8000US.

According to that datasheet the inverter efficiency is 95.5%. I'm also very interested to see what the actual power output will be.

Yes, you are right regarding the $3/watt rebate.

Congratulations on also taking the plunge regarding a home PV system.

To all of the contributors who have installed PV systems: let's see some photos!

 

Here's a picture of our 5.28 kW PV ground mounted array.

 

Thanks. Pls say more about that. Looks like you added 9 panels to the original installation of 16?

 

Had the first 2.88 kW array installed in May 2008 and then followed up with the 2.4 kW array in May 2009. Our last payment to the utility was $2.40 on 06/26/2009. We will be purchasing a BEV (Nissan Leaf) and the 2.4 kW array was based on this.

Cacti

 

I got my figure from this map:

Solar Insolation Map

But, the official NREL map here:

http://www.nrel.gov/gis/images/map_pv_us_annual10km_dec2008.jpg

does supports your higher figure. Good for you!

The Enphase inverters I am getting are also 96%
efficient. But, the entire process of capturing energy
with solar panels and inverters yields ~80% of the
theoretical maximum, according to my installer.
My installer has four customers whose PV power
generation statistics are publically viewable in realtime,
these four sites use different brands of inverters and
solar panels, and in all cases on perfect weather days
the best they get is about 80% of their nominal DC
wattage rating. And often, this peak of 80% is only
achieved for the couple of hours around noon.

StraightUp Solar Projects | Solar Electric Systems | StraightUp Solar FAQs

I'll ask my installer for additional detail where this
loss is actually occurring. I'd bet that at least part
of it is from the fact that fixed-mount PV arrays
obviously cannot track the sun for the optimal
power-generating light angle, in addition to the
loss coming from DC to AC conversion.

 

Hill, what direction is the photo showing? I was
surprised that you had arrays on both sides of
the roof! Normally, one side of the roof is far
superior to all the other sides.

 

Different facets=two inverters to keep efficiency up.

An 80% average would be considered great over the course of the day. Between temperature, haze partial shading, etc to get 80% average is pretty good. I think PVwatts uses a ~77% derate for most locations

 

Patrick and Icarus:

I mis-understood my installer's characterization of
what the 80% efficiency figure is comprised of. I thought
the 20% loss was attributable to the DC-to-AC conversion
by itself. Here is clarification he just sent me:

>When I referenced 80% that was in relation to total system
>efficiency - that accounts for each point in the system and
>their additive losses - for example panel output is typically
>10% less than their DC rating, inverters are 94 - 96% efficient,
>line losses are typically 1- 2%, panels are not always
>perpendicular to the sun's rays, dust on the panels etc... So,
>in good sun in the middle of the day, at one point in time,
>we often see approximately 80% output relative to the DC
>rating -- so a 3 kW (3,000) system may produce
>approximately 2400 watts at one time.

Also remember that centralized inverters sync to the lowest
performing PV panel, thereby creating another form of loss.
Hill's use of two inverters for two differently facing sets of
panels is a strategy to avoid this loss. The Enphase de-
centralized inverters takes that strategy to its exteme.

 

You have it about dialed. For those that are taken unawares, they can get horrible efficiency if they chose a system with different facets and yet only install one inverter. I saw one system that the panels were on 3 roof facets, through a single inverter, and when suggested in the design/build stage his performance was going to suffer big time he scoffed at a couple of world experts. 3 months later, upon completion his performance was ~1/2 of what it should have been. In addition to multiple facets, his array got shadowed by wires, by chimneys, and by plumbing stacks!

Before one invests in PV, make sure you at least hire an installer who knows the details, and/or educate yourself as to the simple what not to do things!

Icarus

 

Actually, that's 15 MWh.

 

More fuel for the fire...

The Missouri Public Service Commission just approved
another electricity rate increase for my utility. It is
10%, effective June 3rd.

That's ~10% rate increase for each of the last
three years, or an aggregate increase of 35% over
that time. At that rate of increase, which believe
me I hope does not continue, the base rate will
double every seven years.

When people use payback period to decide whether
to do PV, they compare the known cost of the installation
against the expected cost of future consumption. The
gotcha is that the latter cost is an impossible-to-predict
moving target.

 

How about a Youtube video - where we see - and you explain - the setup, and the Uber-Cool spinning backwards dial.

Then geocode your location (in the video).

 

Our solar panel installation completed a couple hours ago,
and I just experienced the same thing you did: seeing
my meter spin backwards!

Tomorrow, I get to see the production during the prime
hours. Can't wait!

 

Please show a picture of your solar panel array installation (or PH/EV refueling station?) if you don't mind.