Photovoltaic solar panels

[Fat Jeff]

Good fortune has smiled on our family, and we are looking to be moving into a new house next spring. The house will be in the new Gentry Latitudes development. One option that is going to be offered is a "Photovoltaic solar panel" that will generate electricity for the household. I'm not familiar with these at home "power plants" other than knowing that they are meant to be supplemental power sources, not primary. One thing we have lots of in Ewa is sunshine, so I'm interested in finding out more.

Anyone here have any info/experiences they could share?

[Random]

Re: Photovoltaic solar panels

How much more wattage of power can you generate from those solar panels, compared to the ones made 10 years ago?

[zztype]

Re: Photovoltaic solar panels

How much do they want for the option and, yes, how much wattage do they produce? Really interesting! I was really interested in photovoltaics back in the 80s, but the price never dropped substantially in the following years.

To me, the technology got sort of shoved to the back-burner. Good to see it moving to the front again.

[Fat Jeff]

Re: Photovoltaic solar panels

How much do they want for the option and, yes, how much wattage do they produce? Really interesting! I was really interested in photovoltaics back in the 80s, but the price never dropped substantially in the following years.

To me, the technology got sort of shoved to the back-burner. Good to see it moving to the front again.

I won't have any details of the offer until we get the call to pick/accept a lot. The few details I have come from a Advertiser article...the claim is that the system will generate about 1/3-1/4 of the electric needs of a family of 4. Based on what, who knows? A family with multiple computers that run the central a/c 24/7 will use a lot more power than one that leaves the windows open and reads under a one bulb lamp at night. The price stated in the article is $15,000. No mention of storage or being on the grid or being able to "sell" back to Heco.

From some reading I did yesterday, Hawaii is one place where "grid parity" is achieved, the point where the cost of the system is equal to purchasing electricity from the utility company...again, based on what kind of economics...who knows? But seeing as all this will be going down in sunny Ewa Beach we should be able to get the most from whatever system.

As we get closer to the actual "buying" and optioning process I'll have more details. Til then I'm gonna keep reading up and asking questions.

[Pomai]

Re: Photovoltaic solar panels

From the Honolulu Advertiser: Gentry will build homes in 'Ewa with solar-power boosting option

I'm really impressed with the new homes out in Ewa. My coworker recently bought a new home out there, and the standard energy features are impressive. It included radiant barrier insulation in the roof, insulated walls, double pane windows, central A/C & solar water heater just to name a few. There's more. Features you'd spend an arm and leg if you were to retrofit to an older home.

[Fat Jeff]

Re: Photovoltaic solar panels

From the Honolulu Advertiser: Gentry will build homes in 'Ewa with solar-power boosting option

Pomai, that's the article I read that got me started on this inquiry. And yes, nice to see new homes that are built with some of the newer (modern foam insulation, radiant barriers, solar) and ancient (double pane windows, our house had those in the 60's) technology to save energy. Simple things that work and that Gentry skipped over in our 12 year old house. And yeah, the floor plan we are interested in is definitely a "step up" for us and our rapidly expanding family.

[Random]

Re: Photovoltaic solar panels

To me, the technology got sort of shoved to the back-burner. Good to see it moving to the front again.

Well, I figured some scientists or engineers somewhere is working under the radar to improve photovoltaic or solar-cell technology. But yeah, the cost is the one of the drawbacks among consumers (the other being the sun's exposure time ... won't work if you happen to build a colony on the dark side of the moon).

[joshuatree]

Re: Photovoltaic solar panels

Will this solar panel system work when the power grid is off line (black outs)? Some systems are designed to shut down for safety reasons, ie., power company crews won't get zapped by the solar panels when they are working to restore power.

[GnosticWarrior]

Re: Photovoltaic solar panels

What I look at is return on investment. How much? What is my expected rate of return? From what I see from a purely financial not environmental basis, should one invest $15,000 in a solar cell system or instead put it in an index fund earning 10% on avg., I'll go with the index fund.

With an after tax rate of return of 7.5%, you should double your investment in 9.6 years. With solar, you might just start to break even with your investment. Right now, I don't think its cost effective yet, with our traditional power source. It could get there in the future and those who buy now are helping to pave the way.

Citizenre sounds promising though it won't start till sometime in 2008, I still haven't decided if its a good deal. If this turns out to be more of the peak of the average price of oil, you won't save much. It's hard for solar or wind to beat the return of an index fund or find some other investment to counter the rise in oil and electricity prices.

[Nords]

Re: Photovoltaic solar panels

Pomai, that's the article I read that got me started on this inquiry. And yes, nice to see new homes that are built with some of the newer (modern foam insulation, radiant barriers, solar) and ancient (double pane windows, our house had those in the 60's) technology to save energy. Simple things that work and that Gentry skipped over in our 12 year old house. And yeah, the floor plan we are interested in is definitely a "step up" for us and our rapidly expanding family.

Even if you don't do anything else, absolutely go with the foam insulation, the radiant barriers, and the solar water system. Ewa has the island's highest insolation rates and you'll see a huge payback on your electric bill-- at least $5-10/month per family member on the water heater alone. If your family is "rapidly expanding" then you'll want a 120-gallon heater to retain enough hot water to get you through those cold cloudy winter days without the electric backup kicking in. Our tank is only 80 gallons and we limped through 2006's 40-days-and-40-nights-of-rain.

I've seen solar water heater paybacks advertised as short as three years, which greatly depends on your water use. Even at 5-8 years you'll save money, a great deal considering that the median family moves every seven years. However gas water heaters are much more efficient and tankless water heaters are competitive with the up-front cost of solar water heaters. So if you have a gas line to your house, or go tankless, you'll have a much longer payback for a solar water heater.

Some people worry about 150-degree water in their faucets, and that concern can be reduced by installing a thermal mixing valve at the water heater or by putting temperature-limiting valves in the bathtubs.

The PV system... eh, not such a good deal. The Advertiser article reads like they copied it right out of the press release.

Most of the cost of a PV system is the labor & training, and the DC/AC inverter is another ~$2500. Compared to those two numbers, it's not that much more effort (and $$) to install a 3000-watt system than it is a 1000-watt system. Most inverters have a 3000-watt capacity (a few are even bigger) and Gentry's numbers are unrealistically rosy. For a good estimate on a bigger system, talk to Keith Cronin at Island Energy Solutions. You may be able to get 3000 watts for under $25K, even less after tax credits.

IMO the "one-third for a family of four" is way too optimistic. Our 3000-watt array produces 280-300 KWHr a month. Our family of three very conscientious people uses about 0-150 KWHr a month above that. We have solar hot water, compact fluorescent bulbs, Energy Star appliances (even an E.S. ceiling fan), no A/C, minimal phantom loads, and we only run the electric dryer for 4-5 loads a week. We also have great tradewinds and way less blazing sunshine than Ewa. So even without using your A/C you'll be lucky if that 1000-watt array knocks $20-$30/month off your bill.

Oh, by the way, the federal tax credits expire 31 December 2007 (less than 90 days). You'll have to move fast to be able to claim them.

What I look at is return on investment. How much? What is my expected rate of return? From what I see from a purely financial not environmental basis, should one invest $15,000 in a solar cell system or instead put it in an index fund earning 10% on avg., I'll go with the index fund.

There's a couple ways to estimate that. A sales expert will want you to focus on net cost (after you take all the tax credits) divided by monthly savings. But that's the simplest method for the fastest payback-- and it's still about 10 years.

Other sales staff will distract you with the dividend rate. The annual savings on a 3000-watt array can approach 5% of the system's net cost. That's not only better than most stocks (with less volatility) but it even approaches CD rates. As HECO rams through the rate increases, this annual dividend rate will increase to 6% or even higher. You'll hear "Who cares about the payback, look at those lifetime dividends!"

The most complicated method (yet the most realistic and conservative method) is opportunity cost. Assume you invest the $15K in a low-cost index mutual fund (stocks or balanced, whatever you'd normally choose) and compare its growth to the monthly growth of your PV array's energy savings. The $15K grows relatively slowly because it's not getting additional monthly investments, but that $15K head start is a long one. The PV savings grows a bit every month (and compounds on top of that) but it takes a long time to build up the momentum. It's not unusual for this payback to stretch 15-20 years. If you throw in the inflationary cost of HECO's rising utility fees then it may be closer to 15 than 20.

With an after tax rate of return of 7.5%, you should double your investment in 9.6 years. With solar, you might just start to break even with your investment. Right now, I don't think its cost effective yet, with our traditional power source. It could get there in the future and those who buy now are helping to pave the way.

It's a long-term investment, and difficult for families who don't expect to stay put for a couple decades. Home buyers will not compensate your sale price for the value of a PV array. (They're just not educated enough on the math to care.) Maybe that'd change if the cost of electricity jumped 30% in the next five years, but I doubt it.

Citizenre sounds promising though it won't start till sometime in 2008, I still haven't decided if its a good deal. If this turns out to be more of the peak of the average price of oil, you won't save much. It's hard for solar or wind to beat the return of an index fund or find some other investment to counter the rise in oil and electricity prices.

Exactly. There's a reason that those guys want a 25-year contract, and you can be sure that they've been extremely conservative on their spreadsheets to even have a hope of attracting capital funding. PV systems from the 1970s are still going strong, and today's technology is even better. There's every reason to expect that your system will give you at least 25 years, and they're renting the equipment back to you at essentially zero cost.

By the way this grid-tied PV system will not operate if HECO goes down. The grid-tied inverter only turns on if it senses HECO's AC bus voltage. The only way to have electricity during a HECO outage is to have a stand-alone system, which involves storage batteries (or a backup generator) and is much more expensive than grid-tied.

Same issue for solar water heaters. Most of them use an AC water pump that plugs into a 120V AC receptacle, and it won't pump if HECO is down. However the water will stay hot in the tank for 2-3 days, and hopefully HECO will be back up by them.

I could go on for pages. PM me if you want more details, links, or other answers...

[GeckoGeek]

Re: Photovoltaic solar panels

By the way this grid-tied PV system will not operate if HECO goes down. ... Same issue for solar water heaters. Most of them use an AC water pump that plugs into a 120V AC receptacle, and it won't pump if HECO is down.

Some system have a small PV panel to run the pump. It actually simplifies the design. No sun, the pump doesn't run - and so the water isn't circulated into a cool panel where it could loose heat.

[Glen Miyashiro]

Re: Photovoltaic solar panels

The U.S. Army has been installing photovoltaics on the roofs of all the new base housing at Schofield Barracks.

http://starbulletin.com/2006/05/26/news/story04.html

[Nords]

Re: Photovoltaic solar panels

Some system have a small PV panel to run the pump. It actually simplifies the design. No sun, the pump doesn't run - and so the water isn't circulated into a cool panel where it could loose heat.

I like the idea, and it saves a watt or two. Our system has a bit of reverse circulation (hot water rises past the backflow loop and the checkvalve to eventually heat up the panel) so heat can be lost either way. The AC pump turns on at night once or twice an hour for a few seconds to pump down the panels again and minimize the heat loss to about 20 degrees. I wonder how much more it'd be if we had a DC pump... guess I'll have to unplug the AC pump some night to check.

When I checked into DC pumps five years ago there was concern that the DC brushes were wearing out faster than an AC pump. Do you know if that's been fixed, or is it still an issue?

[oceanpacific]

Re: DC punps .......

That's a good question. That was the problem of solar water heating systems with DC pumps vs. AC pumps. The AC pump would add $2-3/month to the electric bill, but a replacement DC pump could cost $150 every two years. That's only $72 ($3 x 24 months) saved vs. $150 expended: $78 net loss plus "down time."

[GeckoGeek]

Re: Photovoltaic solar panels

When I checked into DC pumps five years ago there was concern that the DC brushes were wearing out faster than an AC pump. Do you know if that's been fixed, or is it still an issue?

No idea. I wonder if the pump is too big for brushless motors (DC motor has an electronic "brush")