Photovoltaic array

[Kenton H. Shepard, CMI]

I came across this house doing draw inspections. The PV system's been up and running since about January, I think. His meter's been running backward since the system came online.
That's 2 tons of greenhouse gases which weren't put into the air, one house, 5 or 6 months.

[brian winkle]

Kenton, do you know how many watts that is? If I had to guess, from the size of the array, I'd say 1500.

[Kenton H. Shepard, CMI]

Originally Posted by brian winkle

Kenton, do you know how many watts that is? If I had to guess, from the size of the array, I'd say 1500.

Here you go Brian...

[phinsperger]

Looks like he's planning on a few more.

[brian winkle]

cool

[Greg Fretwell]

The jury is still out on these PV systems. There are plenty of folks who say more energy goes into producing the array than well ever be collected from the sun. (plus the chemical pollution) I can assure you his meter does go "forward" all night.
Germany pegs the cost per KWH of their big municipal sized solar systems at 50 Euro cents. (4 times what FPL charges me). When that gets down to 15 cents I may play.

[Ian Gills]

I hope the roofs and attic spaces are provided with extra support when these things are installed. I thought that, technically, roofs are designed to have nothing on them (except roofing), and attics designed to remain empty (and just to carry the weight of the roof).

Assume electricity costs 15 cents/KWH and that this things kicks out 3KW for 12 hours every day of the year (extremely over-optimistic). And let's say it costs $20,000 to install (again optimistic but I think they cost that much in the UK). It would pay for itself in 10 years.

Not for me.

The CO2 savings is impressive though. That's the equivalent of not driving two cars for a whole year.

[Greg Fretwell]

Don't forget maintenance costs. These things do break and if you have windstorms they might not last a summer. Everyone I know who had a solar system abandoned it when they bought a new roof. That is where I got my swimming pool collectors
Pool heaters are probably the most economically prudent solar application. Even with that I would not put the collectors on the roof of my house. I have mine on an aluminum pan roof over an expendible "Florida room".

[Kenton H. Shepard, CMI]

The PV panels are light and this set is going to have to withstand winds over 100 MPH. Home belongs to an experienced local builder so he knows what he's up against.
I think those mounts are for future collectors for heating water, I think there were plumbing stub-outs.

He's got Icynene averaging about 30" thick sprayed onto the underside of the roof. Non-vented attic.

In looking for pictures of installed PV shingles I spoke with a homeowner who's had them installed long enough for the company who installed them to go out of business. The shingles still work fine but the battery back-up system bit the dust and the owner can't get anyone to call her back, so dealing with that must be a can of worms.

[Greg Fretwell]

That is the attraction of net metering schemes. You don't have to do any storage. This does point out the problem with net metering. As long as this is just a hobby thing with a few people playing it is fine but if a significant portion of your power generation was on the roofs of people who don't have a clue how it works, plan on brownouts and outages. I am not even sure how it saves the utility money. They still need capability for 100%+ of total demand for that cloudy day.

[Kenton H. Shepard, CMI]

Originally Posted by Greg Fretwell

That is the attraction of net metering schemes. You don't have to do any storage. This does point out the problem with net metering. As long as this is just a hobby thing with a few people playing it is fine but if a significant portion of your power generation was on the roofs of people who don't have a clue how it works, plan on brownouts and outages. I am not even sure how it saves the utility money. They still need capability for 100%+ of total demand for that cloudy day.

Greg, I'm assuming it's PR for utility companies, how would they make money on people producing their own electricity?

I'm a little confused by your post, though. My understanding is, net metering means you're hooked up to the grid and if over the course of the year your system produces more than it uses, your meter runs backwards and you get reimbursed for the difference. That's how it is here anyway, because the owner of this system was complaining that he couldn't roll it over, the utility insisted on payed cash for the difference at the end of whatever the period was.

So if a home is on net metering, which I thought meant that although they produce their own electricity, they're still hooked up to the grid, how could a failure of one or more home systems produce a brownout or general outage?

Seems to me that if a lot of people did this, even though it sounds good, power comapanies must have to estimate how much power they need to provide for their customers. If many homes were producing their own electricity but had unreliable systems, wouldn't this make it more difficult for power companies to plan efficiently as to how much power they would have to be prepared to supply annually? This must mean that power companies would have to use the worst-case scenario and so the present situation would change very slowly.

One more question about green building. It seems widely agreed that there's a lot of harm being done to the global environment, and that the amount of harm is tied to and will accelerate with the growth of global population. Trying to pick out what systems can be truly effective over the long term and which are dumb ideas... and everything in between... seems to me that PV systems, even if their payback is 10 year and they have growing pains, are a step in the right direction.

I was pretty amazed by the 2-tons of greenhouse gasses saved in 6 months. I had no idea.

[Greg Fretwell]

If a significant part of the power generated is coming from an unregulated and perhaps unreliable conglomeration of scattered rooftop collectors balancing the grid will be very hard to do. Brownouts and outages are the result of that when they have to instantly come up with the power they lose from the homeowners. The reason it works now is the homeowner componant is negligable.

[Michael Larson]

Originally Posted by Greg Fretwell

They still need capability for 100%+ of total demand for that cloudy day.

Greg, that is a good point not clearly understood by many people.

The utilities have to design and build for 'PEAK' demand. Windmills and Photo Voltaic just can't be turned on and off at will. Not only that they have to anticipate the need for in differant areas of the country and do it well in to the future.

To the consumer it's ubiquitous, to the the engineers and planners it approaches rocket science.

In North America we have some of the most reliable power in the world and have had for a long time.

[Marc D. Shunk]

Originally Posted by mlarson

The utilities have to design and build for 'PEAK' demand. Windmills and Photo Voltaic just can't be turned on and off at will. Not only that they have to anticipate the need for in differant areas of the country and do it well in to the future..

There is an electric Co-Op in my area that has installed equipment on dozens and dozens of the larger business and farm back-up generators so that they may be remotely started by the utility. They do this for what's called "peak shaving", during high demand times. They pay the customer an agreed upon rate for whatever amount of electricity their gensets provided during that time. Many or most large utilities have built their own large peak saving plants that only run during peak demand times. What this co-op has done is to use the existing generating capacity that already exists on their customer's sites, and utilized it for "distributed peak shaving".

I see distributed energy to be the future of my trade. There have been at least two monthly magazines dedicated to distributed energy crop up in the past year alone. Devices called "CHP" (combined heat and power) micro-turbines are quickly gaining favor in tall buildings and large campuses of buildings.

[Michael Larson]

Originally Posted by kshepard

I was pretty amazed by the 2-tons of greenhouse gasses saved in 6 months. I had no idea.

Is that a lot?

Carbon footprint for 1 round trip for LA to NYC is about 2 tons/person on the flight.

I guess that means the owners(2) can fly 5,000 miles/year guilt free.

Or they could just by a carbon offset for the same guilt free feeling for $7 per flight.
BUY OFFSETS



I suspect we will all be seeing much more "green" building in our industry. We have a lot to learn again.