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Old 12-11-2009, 10:13 AM   #21
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I understand the view behind what you say, but aren't utilities already a regulated industry? So I'm not sure that much of what you state above really applies, due to the regulation already being in place. I suspect one reason that the utilities are not putting in much solar is a combination of not getting the incentives that homeowners do, and that it just doesn't make economic sense for them.
I believe our state laws in my jurisdiction have regulated the power companies to require X% of their power to come from renewable sources (primarily wind/solar I think). It is up to them to figure out how to meet these regulations. One way I think they do it is through a green energy initiative that pays WAY above market rates for green electricity (20 cents a kWh vs the ~8 cents per kWh they sell it for). So private individuals can get 2/3 the cost of a solar/wind system paid for by the government (we the people really) and then get a 150% premium on any electricity generated. I don't think the power company can get anywhere near this good of a deal if they built their own solar/wind "plant".
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Old 01-12-2010, 05:28 PM   #22
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Well, this looks like the most current thread so I will jump in to blog my experience which is just beginning. I skimmed the threads Nord's referenced (and followed them back in the day) but they seem a little dated.
I'm getting here a little late, but part of that absentee time was spent analyzing a minor flaw in our PV array and then fixing it. Essentially our two strings of panels weren't balanced to provide the same amount of voltage to the inverter's inputs, and the inverter was only optimizing one of the string's power-conversion processes-- to the detriment of the other. Now the two strings are balanced and we'll know in a few months how we did.

I feel like I've written an overwhelming amount of geek-speak on a topic that used to be of pretty narrow interest, but I'm happy to jump back into it. When we were building our array I worked long & hard to find used panels for under $4/watt, but now it looks like $3/watt isn't too hard to find. Mounting racks are way better, and the roof penetrations are much less likely to leak. I think a lot of the installation is even closer to the capabilities of the average mechanically-inclined homeowner who can find a licensed electrician willing to work with them. The gutsiest part of the project is persuading your spouse that you're going to drill a bunch of holes in the roof without missing the trusses.

Interest is shooting up here. At least one local solar company holds an "open house" every weekend where people can walk a construction site to see how solar water and PV are being built into the home. Other open houses are retrofits where the happy homeowner holds court on his lanai with the contractor.

It's always easier to reduce consumption than to raise production, and in our case we're hoping for a dramatic consumption reduction when our teen flies from the nest in just 208 days. In the next 3-5 years, though, as more plug-in electric vehicles hit the streets, we're going to put up a pergola on our south sidewalk (to shade the house) and roof it with another couple kilowatts of panels. I think I'll be able to wire a second inverter into the same breaker panel that's being fed by the first inverter, and then we'll get rid of most of our gasoline bill.

Anyone have any new questions beyond the basics?
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Old 01-12-2010, 06:40 PM   #23
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How about:

No way I can do solar on my house due to huge trees. But how would I go about figuring out a system for an RV? Assume I would need a mega battery bank, heavy duty inverter/charge controller and maybe 200 kw of panels?
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Old 01-12-2010, 07:15 PM   #24
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...200 kw of panels?
Monster RV to hold 200 kw of panels!!!
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Old 01-12-2010, 07:29 PM   #25
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Brewer was of course joking. A panel sized for residential installation typically has a size of 40"X60" and produces 200W. One thousand panels?

About solar for RV, I have picked up and read a book on RV boondocking. If I can recall the title, I will post here. The author went to great lengths on the feed and care of the battery banks. Of course the key to the battery long life is not to discharge it too deeply. It really limits the amount of energy that one can store and use. I guess we will quickly learn a quite different lifestyle than one we lead now, once we start RV'ing, particularly boondocking.
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Old 01-12-2010, 07:43 PM   #26
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The trick for boondocking is to have a generator. And a large freshwater tank plus large waste tanks - unless you have a bathroom nearby.

Our motorhome draws too much power even on the chassis batteries for solar to keep up. We have a 100W solar panel, but I don't think it would even keep the house batteries topped off.

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Old 01-12-2010, 07:53 PM   #27
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There are folks who use the RV built-in generator so infrequently that they remove it, and only carry a little 1KW portable Honda generator for cloudy days. They do nearly cover the roof with panels though. It still takes extreme frugality in energy usage.
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Old 01-12-2010, 07:59 PM   #28
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There are folks who use the RV built-in generator so infrequently that they remove it, and only carry a little 1KW portable Honda generator for cloudy days. They do nearly cover the roof with panels though. It still takes extreme frugality in energy usage.
Yep. Guys like Tioga George and Andy Baird seem to manage this just fine. The wrinkle is that AC usage is pretty much impossible. I would not go that far. At the moment we have a small (16') travel trailer that we mostly use for weekends to a week (and as a guest bedroom in the driveway, and an adult playhouse), but eventually we will end up graduating to something bigger (likely a class C or larger trailer) and at that point I will want to be able to live without shore power or running the genset all the time. A PV system appears to be just the ticket, hence my curiosity. But I am coming from a position of near total ignorance.
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Old 01-12-2010, 08:07 PM   #29
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No RV owner here yet, but I have looked and spent time inside a few. I don't know about big class As, but in a fairly large classs C (30ft), the generator drone would drive me nuts if I have to run it constantly for the AC. I would rather drive somewhere that is cooler. Genset running for a short time (1 or 2 hrs?) to top off the battery or to microwave would be OK.
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Old 01-12-2010, 08:11 PM   #30
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I do not disagree, NW, but if you are parked somewhere that is 100F for a while and do not have the option of turning on the AC, you will be sorry. Learned that my very first time out in a rental in NM in the summer.
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Old 01-12-2010, 08:24 PM   #31
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Eh? Why do you have to convince me, a guy who likes to run around in Bermuda shorts in 50-60F?

Full-timer boondockers plan ahead and head for the high hills, and don't let themselves get caught in the heat. If that failed, I would just head for the nearest 30A plug.
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Old 01-13-2010, 01:36 AM   #32
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Sailboats use a combo of solar and windmills to generate power BUT they don't consume a lot. Pay a visit to your local boat yard or check out a boat show with yachts, not a power boat retailer.

We had solar hot water on our roof in Portland, in a shaded area. That puppy melted dip sticks and blew off steam regularly. This was a while back and I see the current home owner has removed the set-up. Based on my experience, it doesn't take much of a system to get water boiling. Doubtless there are better control systems today.

Daughter did a major remodel of a home in the area that qualified for the solar program in San Jose County. Ever the number pusher she said there wasn't sufficient return on investment because the previous owner had very low usage and the program was based on the home's history of electric consumption. She passed. Now that the house is full of kids her IRR may be different.
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Old 01-13-2010, 06:27 AM   #33
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I think the move by Lowes to offer DIY solar panels will help reduce the cost of panes even more. Residential Solar will take off in the South as 1) utilities in the South transition away from Coal. For the most part, Duke and the Southern Company Utilities depend heavily on Coal which is one of the reasons why generally electric rates are lower than FL and other parts of US. 2) more contractors offering solar installation 3) States offering more financial incentives
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Old 01-13-2010, 08:07 AM   #34
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But how would I go about figuring out a system for an RV? Assume I would need a mega battery bank, heavy duty inverter/charge controller and maybe 200w of panels?
I guess the first question you have to answer is "why". We enjoyed designing/installing our project and it's going to save us money in a home where we're living long past the payback. I don't know how well those motives transfer to an RV.

Audrey and REW have said a number of times that they don't do their scale of RV to save money, although I guess some full-time RVers manage to reduce their housing costs. In an RV I'd think that the PV system wouldn't get much use unless you went full time, and gas is cheap by comparison.

Quiet boondocking would be the best use I could think of, but again it might cost $6-$8/watt to install a PV system that could power lights and a fridge. The PV would have a terrible time trying to keep up with A/C. I don't know if the reduction in gasoline/generator use would ever recover your costs, and if RV solar is like home solar then no one will ever pay you for the feature on resale.

Sailboats make some use out of PV, but that's the ultimate boondocking and there's a reason that they install windmills. (And I'd hate to drop a piece of rigging on top of a panel.) However the sailing industry has the deep-cycle marine batteries that you'd want for an RV, and maybe "marine" is just a traditional word for a typical RV battery. Anyway you'd want batteries that you could beat all the way down close to cell reversal between sunset and sunrise. And I think most sailboats run 12v or 24v systems throughout.

Unless you had a class "A" you'd probably struggle to get more than 200-300 watts on top. What's an RV electrical system run on-- 12v, 24v, or AC? There are a number of companies selling "microinverters" that mount under each PV panel and produce 120v 60Hz AC. But an RV system would run more efficiently if all the lights & appliances were 12v DC with maybe another small plug-in inverter for non-RV portable AC appliances. The advantage of the microinverters is that each panel has its own inverter and can do its own thing instead of forcing a bigger inverter to deal with a bunch of panels getting different solar exposure. (Of course they drive the cost up a bit.) Add a charge controller for the battery bank, do a lot of wiring work, waterproof the heck out of each roof penetration, and you'd be off the grid.

I don't know how much objective info you'd get from RV manufacturers or aftermarket companies. "Home Power" magazine sometimes comes across more as an industry cheerleader than a guide to affordable PV, but they seem to have several articles on RV solar. (RV Comfort: Anywhere the Sun Shines) They charge a few bucks to read their archive articles but it's well worth it.

I was in our local solar supply store the other day and saw 1000-1750 watt inverters designed to run off 12v batteries. They've been around for years but now they're getting cheap. However instead of using one with a PV system I'd use them for power outages. And instead of attaching it to PV panels I'd attach it to the battery terminals of our Prius and run the refrigerator off the Prius' gas tank. But power outages around here aren't very frequent and if the hurricane smacked Oahu then we'd just revert to 19th-century life for a few weeks.
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Old 01-13-2010, 08:48 AM   #35
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There are folks who use the RV built-in generator so infrequently that they remove it, and only carry a little 1KW portable Honda generator for cloudy days. They do nearly cover the roof with panels though. It still takes extreme frugality in energy usage.
Yeah, if you're in a tiny trailer with few appliances/systems and willing to change the generator oil every 16 engine-hours. And getting the fuel into those things is a pain.

We use the built-in generator quite often. If it's really hot out, we run it while driving to help with the cooling. We run it if we need AC while stopped at a rest area.

Yes, the gen is noisy, but if the AC is running, you barely hear it! LOL!

If we are boondocking and not needing AC, we run it about twice a day for about an hour each time.

Personally, I can't imagine not having the built-in gen.

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Old 01-13-2010, 09:05 AM   #36
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I was in our local solar supply store the other day and saw 1000-1750 watt inverters designed to run off 12v batteries. They've been around for years but now they're getting cheap. However instead of using one with a PV system I'd use them for power outages. And instead of attaching it to PV panels I'd attach it to the battery terminals of our Prius and run the refrigerator off the Prius' gas tank. But power outages around here aren't very frequent and if the hurricane smacked Oahu then we'd just revert to 19th-century life for a few weeks.
FYI - most motorhomes come with inverters. We have a 2000W inverter that can power everything but the A/Cs. So when stopping at a rest area, etc., we can run microwave and everything and don't run the gen unless it's pretty hot.

We have house battery bank 8 golf-cart batteries that powers the inverter. Yes, RV house batteries are deep cycle (aka "marine") batteries. Still, you don't want them to drop below half-charged or else you end up ruining them.

The power switching in our motorhome is so sophisticated and seamless that you don't realize shore power outage unless the A/Cs cut off. As an EE who has designed power supplies for electronics systems I am still amazed how totally "glitchless" our power system is. The motorhome is like one giant uninterruptible power supply!

The fridge - most RVs have fridges that use the older gas refrigeration technology and run on propane when no shore power. So powering the fridge is not an issue when boondocking.

A lot of the lights are 12V and some of the devices (detectors, water pump, etc), but not any of the appliances or audio-visual components (except for the in-dash audio system).

Audrey
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Old 01-13-2010, 09:28 AM   #37
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Using PV to make electricity to power a motor that turns a mechanical compressor which produces a liquid from a gas that can then be expanded back into a gas to produce cooling--that's a lot of steps and losses at every one. I would think adsorprive cooling (of the type used by propane-powered refrigerators) run directly by the sun would be a lot more efficient. Or, I've seen some diagrams of setups that use heat to drive the water out of a solid dessicant (e.g. silica gel), which then dries the incoming air, water is sprayed through the dry air to cool it, and the cool air goes into the living area (like a "swamp cooler" but it works in any climate). The dessicant is "recharged" (by solar energy) and reused continuously. While all of these schemes would work only when the sun was shining (or when you could burn propane as a temporary replacement), they would seem to be more efficient and probably less costly than a PV system. And a lot of fun for basement experimenters!
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Old 01-13-2010, 10:06 AM   #38
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I was in our local solar supply store the other day and saw 1000-1750 watt inverters designed to run off 12v batteries. They've been around for years but now they're getting cheap. However instead of using one with a PV system I'd use them for power outages. And instead of attaching it to PV panels I'd attach it to the battery terminals of our Prius and run the refrigerator off the Prius' gas tank. But power outages around here aren't very frequent and if the hurricane smacked Oahu then we'd just revert to 19th-century life for a few weeks.
So this would work? Get a 1000 W inverter and hook it up to any old car's battery terminals? Then run the car as normal and let the car act as a generator? I had thought about getting a set up like this for the occasional extended power outage. But wasn't sure if the 12v DC from the car's battery terminals (or "cigarette lighter" adapter) could provide enough juice long term to power a 1000 W inverter. Or is that Prius-specific due to batteries?
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Old 01-13-2010, 11:13 AM   #39
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So this would work? Get a 1000 W inverter and hook it up to any old car's battery terminals? Then run the car as normal and let the car act as a generator? I had thought about getting a set up like this for the occasional extended power outage. But wasn't sure if the 12v DC from the car's battery terminals (or "cigarette lighter" adapter) could provide enough juice long term to power a 1000 W inverter. Or is that Prius-specific due to batteries?
You can run a 1000 watt inverter from a regular car's battery, but you need to make sure the alternator puts out enough amperage at idle to keep up. The beauty of using this setup with a hybrid is that you can tap the juice in the drive battery via the DC-DC inverter and the car will actually start and stop its engine as needed to keep the battery charged, thus minimizing fuel usage. A few months ago Costco had 1000 watt Xantrex inverters for about $40.

This is a good link on the subject:

Inverter FAQ - DonRowe.com - Frequently Asked Questions about Power Inverters
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Old 01-13-2010, 11:31 AM   #40
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You can run a 1000 watt inverter from a regular car's battery, but you need to make sure the alternator puts out enough amperage at idle to keep up.
Right. As an example, the typical alternator in a family sedan (e.g. Toyota Camry) puts out 80 amps max. At 12VDC, that would equal 960 watts. And, it is not designed to do that for very long--it will get hot and not last very long. And it probably won't produce that much juice at idle, so you'd have to sit in the car with your foot on the gas. Reving a 100HP+ engine continuously in order to produce less than 1000 watts is not an efficient use of fuel.

I also thing you'd want a direct connection to the battery or main bus, that cigarette lighter accessory plug in most cars probably isn't built for this much juice.

A smaller inverter might work okay for emergency use in a typical car.
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