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Solar Dreams - Need Dose of Reality

Posted by brooksideiris (My Page) on
Fri, Feb 2, 07 at 14:03

Hello. I live in Kansas City, where we get all the weather it's possible to have (right now it's 13 degrees out, with snow on the ground). For years I've dreamed of PV roofing, but I have no hope of net metering (my electric company says absolutely not and do I have any idea how much space it would take to generate ANY electricity AT ALL????). Well, I don't, but I'd love to learn. From my phone book, I glean that there is only 1 company, Power Tomorrow, that serves KC (as well as GA, NM and CO). Information on their website is general and basic, tho they claim my investment in solar would return 12 - 25% (and their example includes net metering, so clearly they're not talking about MY area).

The only south-facing roof I have is an unobstructed porch roof, perhaps 15 X 25 feet. I would love to generate enough power for hot water (perhaps using an electric tankless?) and radiant flooring for my sunporch and bathroom. Is that reasonable?

The Power Tomorrow website says they warrant their roofing for 5 years but expect it to perform for 20 years. Seems a bit of a gap, there. How reliable is solar roofing? How much do we have know about the longevity of pv roofs? A recent post here spoke of deteriorating south-facing pv cells used for outdoor lighting. Is this also a problem for the pv shingles? I keep reading here about advances in pv technology that are just around the corner but never read any specifics. How far around the corner? Are these new shingles worth waiting for or might these advances be vaporware? I've read about 2 or 3 different shingle systems. Is there a material difference between different companies' pv roofing systems?

I've probably had snow on my roof for about a week so far this winter, given our recent spate of ice and snow storms. I assume a pv system wouldn't generate any electricity without my shoveling off the roof (which I could do for snow but won't for ice)? How well do these shingles hold up to weather extremes? In fact, how successful are they as just plain ROOFING? Any problems with leaking?

And then the biggie: How much should I expect a 15 X 25 roof system to cost? Is it possible to DIY a porch roof? Given what I have to work with, obviously off-grid, is solar feasible for me?

I am confused and ignorant, but I appreciate any and all guidance you have to offer me. Thank you.


Follow-Up Postings:

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RE: Solar Dreams - Need Dose of Reality

I'm building a new house with a pv system and a hot water system for my pool.

The one piece of advice I have, especially if your utility won't do net metering, is that you probably shouldn't be looking at a pv system. First of all, they're much more expensive than hot water systems. Second, it's commonly accepted that it's very inefficient to first generate electricity and then use that to heat water.

I would think you should be looking at a hot water system, one part hooked up to your domestic water supply and the other for use in a hydronic radiant floor system.

Good luck!


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RE: Solar Dreams - Need Dose of Reality

Solargary, thank you for your response. I actually have no interest in return on investment; I was just quoting from Power Tomorrow's website because I found it to be uninformative, a bit ridiculous, clearly not apropos for my locality and yet apparently my ownly resource for solar technology in Kansas City.

My main interest is learning more about pv roofing systems. Since you are in Wichita, however, I have to assume that your response means that you agree with KCPL? That there truly is no point in attempting to generate roof-top electricity in our part of the country?

I have indeed spent time on your web site and have found it to be a source of much inspiration. In fact, if it were feasible, I would adopt a greenhouse project to provide hot water and radiant heat for my ground floor, would use my porch roof to heat water and provide radiant flooring on my second floor and would build a windmill to provide electricity for my third floor. The reason I'm focusing on my porch roof project at the moment is because that porch badly needs reroofing, so if a solar system is at all in my cards, it's kind of now or never. Which is why all the questions about the reliability, cost and lifespan of current technology.

What do you mean by "Computers -- saved 1624 KWH/yr cost $20 return 812%"? Do you mean just turning them off when not in use? We have 4 of them in this house, so if there is some other cost-saving trick, I would love to know about it. Beyond that, tho, my refrigerator is only 4 years old and this is a 100% fluorescent household (except that I'm adding some LED undercabinet lighting). I am in the market to replace my 15-year-old gas water tank with either an electric tank or a solar-powered electric tankless, yet another component of my porch-roof project.

I appreciate your insight. I feel like I'm floundering in the dark, here. I'm reading a lot, understanding some of it, yet still coming away with more questions than comprehension. You know, if I were considering buying a car or a steam oven or even a sofa, it's fairly easy to gather information about available brands, compare features, repair record, useful life, cost and make an informed decision. But with solar roofing, I don't even know where to begin. I can't even call 3 dealers for quotes because there doesn't seem to be more than one. --Kathryn


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Solar Water vs. Solar Electric

Chazas, you are probably right, tho I was planning to use electric mat heating under ceramic tile in my bathroom (from what I understand I would probably need hydronic for my sunporch since it has no other heat source). I'm planning to use hydronic radiant in my kitchen but am uncomfortable introducing the weight of water onto my second floor (tho probably it's no heavier than a filled bathtub).

Yours seems to be the prevailing opinion; still a part of me was hoping to have an alternate source of electricity for power outages. I've lived thru three of them now and fear they could become more frequent in future, given our changing climate pattern. I know, however, that there are more practical backup systems to be had--for all I know my 400 sq ft patch of unobstructeed south-facing roof might not be enough to generate any electric power at all! Thank you for your advice.


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RE: Solar Dreams - Need Dose of Reality

Brook, I'm not a PV expert, but I must tell you that electric tankless water heaters are huge power gluttons. Note that I say power, not energy. They may be more efficient overall than a standby system (and I'm not 100% convinced of that). They may run only when you need hot water - but when they ask for electricity, they suck it through a sewer pipe. No PV system that a normal human can afford can supply that much peak power. Absolutely forget that idea.

In general ANY electric heating with PV is not practical. Put that right out of your mind.

Again, I'm no expert, but I'd look first at solar water heating with a propane or natural gas backup. Then look at simple solar space heating. Build yourself a nice sunspace on the south side of the house.

PV is great for independence, IMO, but step 1 is to pare your electricity usage, then pare it some more. Very few people can afford to use electricity like the average American does - we really guzzle it - and still generate it with PV.

Let's have a little reality check here. Say you want to cover your 15' x 25' roof with PV. Let's think panels instead of shingles for now. Here's a 175 watt panel that's about 65" x 32". (I'm not endorsing that dealer, it's just a name that I happened to remember.) By the time we get it mounted let's say maybe 6' x 3' (someone correct me if I err here). You could put an array 5 high by 4 wide if nothing else were in the way - 20 panels! That's a fair number.

The "175 watt" figure is best case. I'd guess (and again I'm not an expert so this is amenable to correction by the many here who are) that most of the time you'll be lucky to get half that. So you can produce at most perhaps 1800 watts for a few hours on a good sunny day. That will just about run a portable bathroom space heater (1500 watts) with enough left over to keep a few lights on.

Those 20 PV panels will cost you $17,700. Plus mounts. Plus installation. Plus wiring. Plus an inverter to make AC from the DC. Plus batteries to store the power for when the sun isn't shining. Plus some things I've probably forgotten.

That's the reality check (one that might bounce ;-). But - don't let this discourage you! IMO, the way to get into PV is to start small. Buy a panel or two. Use them to run your computer or light a couple of rooms. Add panels as you can afford to do so. Upgrade your inverter when you can. Gradually switch more of the house off the grid and onto your PV. Eventually you will find yourself off the grid.

This is our eventual goal. I pick up bits as I get the chance. Regrettably I'm still waiting to find a few affordable PV panels; these days that's something of a challenge. Some big breakthrough in dollars per watt is always just around the corner, but you could wait forever for it. I suppose that when your (our) bank account and the price cross, you (we) start buying panels.

Again I want to emphasize that I'm really unqualified in this field, I've just done a bit more reading than you have. Speaking of which, if you don't yet subscribe to Home Power Magazine, you should.

One thing more - your LED undercabinet lights will almost certainly be less efficient than fluorescent - possibly less efficient than incandescent. LED is great for extremely dim lights, colored lights, and indicators. White LEDs aren't yet ready for prime time when it comes to area lighting. Give 'em a few more years.


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RE: Solar Dreams - Need Dose of Reality

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I'll ditto that return on investment is much better for solar hot water heating than PV systems. It's the wrong reason to do PV. Independence / philanthropy / environmental reasons are the ones for PV.

My two cents: forget about solar roofing. Nice idea; however most roofs are FAR from ideal angle at ANY time of the year. Then toss snow into the picture. Warranty . . . standard PV panels ( not roofing types ) are warranted for 20 - 25 years. Period. Now consider that you've also gotta do holes in the roof somewhere for all wires at some point. Net metering with the utility ( at least here ) is determined by Public Service Commission => state wide and not utility by utility . . . some states have great regs; some have terrible / none. Don't know your state off hand in terms of policies.

I'll also ditto reducing usage => a figure commonly tossed around is: For every dollar you spend reducing your usage; you save 20 dollars in alternative energy cost.

Snoop around your place . . you'll be amazed what you can find in terms of "phantom" loads. Most computers aren't really OFF when they shut down. Idle; "low" power; but still sucking juice 24 / 7. So too with appliances with remotes. They're really sleeping; not off. That's the only way they can "see" your remote when you hit it . . . parts of them are still "live". How many wall warts around the place . . . phones, chargers, clocks on every appliance, look and you can likely find lots of ways to save on some "small" stuff => it adds up. Biggest culprits are likely to be electric appliances with any kind of heaters => water heater, hair dryers, electric clothes dryers, toasters, etc. Instant water heaters supposedly save ( some ) energy; but in the case of electric ones I think the savings is small over conventional ones with good insulation. As stated above; when the do run; they use HUGE amounts of power => often requiring a bigger electric line or larger gas line.

Good for the CFL's. They're about as efficient a light as there is now; but for sodium vapor types and such; which you don't want in your house anyway. Some of the pretty good, readily available LED's are on par with CFL's as far as lumens / watt => the cost for the same amount of lumens is about 10 times. I'm not knocking them at all; and am a big fan of them and have been for many years. The simple fact is that they are not yet cost effective for lighting of any sized area. They are best suited for smaller task / dedicated lighting . . . and when properly designed ( electrically and thermally ) they can reliably give 100,000 hours of life. Hewlett Packard recently announced an LED that equals high pressure sodium in terms of light output per watt. Probably not going to show up in the commercial or consumer market for some time; but the technology gets better every day. Eventually cost comes down as well . . .

I'm in an 1800 sq ft place in central New York state => we've got some great PV incentives here and net metering is required of ALL utilities here. I've installed a grid-intertie PV system. It's 2800w nominal capacity; on two poles; each pole has a 10' x 10' array on it. Roof mount was not an option due to woods. I now generate about 80 - 85% of my electricity over the period of a year. I used ~ 2500 kWh / year before I went PV. The grid is my "storage bank" . . . I put out to it when I can; take from it when I need to. I also chose to do battery back-up; which does consume some energy year-round . . . but also allows for about 3 ( judicious ) days of juice if grid is down AND there's no sun.

Your local alternative energy place should certainly know what incentives are in place in your state => will help them make a sale . . . find out what they know. They can also help you figure what alternative energy stuff will make most sense for you in your particular climate / location . .

Bob


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RE: Solar Dreams - Need Dose of Reality

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Solargary . . . .

I'm with you about 'puters being phantom loads . . but the numbers you gave seem out of line.

Take a computer ( forget monitors etc for the moment ) and say it draws 200w. ( Remember that the CAPACITY of the power supply is the MAX they can draw . . not what they necessarily draw at any point. ) Anyway; say an active load of 200watts, 24 hrs / day, all year long. That works out to 1742 kWh / year. No sleep, no hibernation, just full on and active. You claim to save 1624 kWh / year. Those numbers just don't add up . . the reduction you claim is ~ 93%.

Your statement about hibernate not drawing any power is not correct => if a computer is plugged in; it's drawing power. Unless you actually unplug it, or turn off the power to it via an outlet strip; it's drawing some power.

I'll also suggest that you need to take numbers from any "power meter" with a grain of salt; unless it's the "old" mechanical type. Many electrical devices draw power non-resistively and can give misleading numbers. Computers especially with switching supplies can give VERY erroneous readings. It takes a VERY sophisticated electronic device to correctly read real, actual power as a utiltiy company electric meter would read it.

I like your efforts / concerns / ideas . . but think you may have managed to mislead yourself in the magnitude of your savings, and how you are reading power . . . . .

Bob


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RE: Solar Dreams - Need Dose of Reality

Hi again Bob,
Oops! I measured the power consumption on my computer in hibernate, and it does draw 2 watts.

This does not actually change the outcome though, in that the 2 watts is included in the 54 watts that all the stuff (including the computer) plugged into the power strip draws when the PC in in hibernate. So, the 1624KWH saving per year is unaffected.

Gary


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RE: Solar Dreams - Need Dose of Reality

If you go the solar hot water route, don't forget to tell your accountant to apply for the 30% federal tax credit. See IRS form 5595 (I believe) for the federal energy tax credits. They were set to expire 12/31/2007, but I think they have been extended to 12/31/2008.

I have solar hot water on my house since August 2006 and it works well. Sunny days with outside temps at 19 provided 80 gallons of 110 degree water in February in NJ. Highest solar tank temps reached were 165 degrees first week of April full sun all day. Even cloudy days, my system adds 10-30 degrees to the city water temperature. (depending on how heavy the clouds are)

Do your research and get referrals when you pick a contractor. When money is thrown at new programs, you get many dispicable contractors trying to make a buck and leave you with a system that doesn't work.


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RE: Solar Dreams - Need Dose of Reality

Hi I live in ST Louis so know what the weather is like. A hot water system will be the least expensive and fastest pay back. Start out small like using it for your domestic hot water. If you make your initial installation scalable you can add on later. If you are able to wait till September than I recommend going to Ozark Renewable Energy and Sustainable Living Expo September 22-23, 2007 It will be in Columbia Mo. http://www.ozarkre.org/ Their will be many contacts and installers and mini seminars there.


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RE: Solar Dreams - Need Dose of Reality

Hi, Brookside Kathryn!
Anyone still on this thread??
We moved from Brookside to Omaha in Jan. I miss it terribly. Your email about the desire to install solar could have been written by me. We are building a "green" house here and I desperately want to generate some electricity from solar film installed on a metal roof. However, we have trees that partially shade the south facing roof making our potential less. Our power co. is public so rates are low and so economically it makes even less sense, and then there is the winter - even worse than KC!
My question, and perhaps something that Brooksideiris might want to consider: should we install all the infrastructure (wiring to the house and what else?) while we are doing the new construction with the thought that maybe technology will improve,( and in our case, we might lose that tree in the future,) so that if we ever decide to install panels or film, we will be set up for it? Would that make any sense?
rcmjr ~~ can I ask you how much your 10 x 10 array cost?
It is hard to rationalize spending $10,000 for enough electricity to run one light bulb, but since the other energy&resource-saving features (geothermal heat pump which also provides most of our hot water - so they tell me, soy-based foam insulation, rainwater-collection for irrigation, dual-flush toilets, low e windows, CFLs,) are all more costly upfront than conventional building, it seems like we should be making an effort at generating electricity in a better way. We are in a neighborhood so wind is probably not an option.
These websites are so interesting and informative. I would greatly appreciate any advice.


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