home PV solar

[idleprocess]

I am in the process of finding a house to buy. One thing I would like to do is install a solar power system someday. I am looking at homes that have good southern exposure on the sides or back and no seasonal obstructions, but otherwise I'm not entirely sure how to proceed short of calling a system installer and asking for their opinions (this project is likely a few years off anyway).

What are some things to consider? I know that a battery bank makes for a much greater system, but you gain backup power and the ability to go off grid if you so desire. A grid-tie system is considerably cheaper, but that assumes you have a utility that buys power from you during the day at a premium.

Is it practical to start small and build out? Do a small "pilot" installation? Build it yourself?

I've always had this weird idea to install some parallel wiring for a dedicated low-voltage power system (lots of things out there that run on 12V, for example), but that doesn't strike me as being overly practical now that I've thought about it unless I can find two or three voltages that are common enough to run ~85% of the devices out there and hope that a common grounding system works out OK. DC-DC conversion seems like it would be more efficient than a DC source feeding an inverter that drives inefficient AC-DC adapters... But I'm not sure this avenue is really worth pursuing.

A small roof-mounted windmill or two would be a possibility at the houses I am considering, but I don't know if mounting a turbine to your house is such a winning idea from a noise/vibration standpoint and in case of catastrophic failure.

[Chengiz]

I am not close to an expert but I have read a lot on this subject. Key word is read. They all recommend that a professional install the system. Warranties and all that.

Depending on what you have on your roof determines if you can install a system there. One doesn't have to go "net zero" out of the chute. You can go half way and cut your bill in half. When you arrive home will the sight of your panels upset you or make you smile.

The wind turbines have radically changed. There are now Vertical (Helix) sytems that operate more efficiently, with very little noise, and are not that bad looking of a device. These systems can operate in winds as low as 4 MPH (Maybe its 8). Now you have to consult the local weather service to see what your average wind speeds are to see if it is worth the cost.

We are considering a "Net-Zero" system. My issue is finding a contractor for this modification as well as a remodel of the patio. Truly there are a lot of things to consider.

And with luck we will hear from some folks who have modified the energy systems of their homes .

[josey]

Hey Idle:

It's not that hard. If you have a few years, I'd start reading Home Power Magazine.

The best way to determine your solar window is to use a Solar Pathfinder. It's kind of like a crystal ball that reflects your horizon. You draw a map on a solar grid that shows you when that spot (or roof) gets sun at anytime of the year. For fixed mounted panels, the ideal is to point them to grid (true) south at an angle that matches your latitude. If you can't get close to that, you're better off with a pole mounted system.

You can mount panels on a pole anyplace in your yard. In the old days of 12V systems, the panels had to be fairly close to the batteries to avoid the need of huge and expensive cables. But these days, you can kick up the voltage to a high DC voltage and drop it down for batteries.

Grid systems are even easier. Most are now wired in series, so you end up with as much as 600VDC. You can run that kind of voltage a long way in small wires without losing power.

Batteries are a pain and are a science all to themselves. Grid tie is a lot cheaper and much, much more efficient. You cannot add to a battery bank after it has aged for a year or so. You need to get the size correct up front. Lead acid batteries are still the best value, but they require a lot of maintenance. You can have a hybrid battery/grid system with just a small bank of batteries to keep your TV and computer and whatnot going in an outage, without wasting too much energy just keeping them topped off. For big loads that you will have to run in longer outages, you're better off with a propane generator. Propane can be stored for a long time without going bad. You can set it up so it comes on automatically when the power fails.

There's a website the has all the incentives available from each state. http://www.dsireusa.org/

Your local utility may have additional incentives.

It's not hard to install these systems yourself. The panels are wired in series, parallel or some combination, which you know how to do. You need a fused disconnect at the panels. Then run the wires to an inverter, which may have a built in breaker or may need a separate one. Then wire the inverter to your breaker box. The utility may require a second meter or a lock box, but it's still very doable and you'll save about 30 percent or more by doing it yourself. If you buy a system, the dealer will sell you all the parts you need with the correct wire.

My cabin is off-grid, but I find I use mostly AC from pure sine wave inverters. I run small loads, like my LED reading lights, off a 400W sine wave inverter because it has a low idle and draw. I use my big house inverter for larger loads. It has a 35-watt draw, which is too big for the small stuff, unless the big stuff is already running.

I have a few DC circuits, but have gradually changed most of them to AC. I have redundancy in inverters, and I've never lost AC power in the 15 years I've run my system. People in town cannot say that about even one winter.

You can start small, with just a few panels, and then add panels later, but inverters have a sweet spot where they are most efficient. So plan for that.

Wind power is not very useful unless you have a really good site. I have a Whisper 600, even though I'm in a poor wind area. But in the winter here in the PNW rainforest, there is not much sun, so the occasional wind storm that comes through really helps fill up the batteries.

It's not a good idea to mount a wind turbine to your house, although I do with mine, and it's a 2-blade version, which is more efficient in low wind sites but less balanced. I use rubber and vibration traps at all mounting points and have no problem. Wind turbines are expensive and to work best they need to be mounted as high as possible. The rule is to get them 30 feet above anything within 300 feet to keep them in smooth wind flow, but higher is better. They tend to need a lot of repairs, and that ain't easy.

Solar is almost perfect. The panels last basically forever. Wind turbines are trouble, and there is more marketing hype about the different designs than in the political race.

[Darell]

I can't add much to what Josey said.

Yes, you can start small and add. But it will end up being more expensive. Like many things in life, it is most cost-effective to take the big bite up front, suffer for a short while, and come out ahead in the end. Put up as much solar as you can afford. You are fixing your price of energy for pretty much the rest of your life (assuming you stay put) - while everybody else's energy bill goes up.

I keep hearing that PV is too expensive. And yet everybody who says it will eventually pay quite a bit more for their energy than those who bought "expensive" PV. So I guess we just have a disagreement on the time period of when we count the expenses.

As for me, my system paid off the moment I turned it on. My loan payments were always less than the power bill that I removed. That my PV system also replaces gasoline in my case... well, I couldn't afford NOT to put up PV.

[Chooie]

I wonder what kind of cost considerations there are when incorporating grid-tie PV with battery backup or a CNG/propane generator when building a new home. I mean, are you better off investing in the most efficient/lowest consumption appliances, or a larger array? I know that appliances and insulation will pay off in the long run, but there's actually profit potential in a larger array than necessary. If I wanted to have the capability to run things like shop tools (welders, compressors, hydraulic lifts, etc.) is that really feasible on PV power alone? I would think that a welder, mill, or lathe definitely would have a higher draw than most of the household combined, including HVAC.

Any thoughts to add?

[Darell]

Originally Posted by Chooie

I mean, are you better off investing in the most efficient/lowest consumption appliances, or a larger array?

Conservation is just about ALWAYS going to be your best bet. Finding ways to use less energy is going to be easier, cheaper, cleaner, better than finding ways to make more energy.

If I wanted to have the capability to run things like shop tools (welders, compressors, hydraulic lifts, etc.) is that really feasible on PV power alone? I would think that a welder, mill, or lathe definitely would have a higher draw than most of the household combined, including HVAC.

Any thoughts to add?

You would NOT want to size for running huge loads off of the PV array directly. Especially if you want to run them at any other time besides noon on a perfect day. Grid-tie means that you can feed into the system when you are producing the most, and take back out at any time that's convenient... or less expensive.

[Atomic6]

Here is an example of a set-up:

A friend of mine in rural Central Nevada is completley off-grid. His system is sized for a 1,800 sq ft house and 4,000 Sq Ft garage/shop that he will be building. Right now he has a small RV and a container converted into a living space. He has a small shed for of all his batteries and inverters. He has his own well and septic already, plus Dish TV and dish PC.

For power he has 5 solar arrays on poles (don't know sizes), two wind generators on poles and a 500 gallon Propane tank that feeds a backup generator . I think his power system has set him back less than what the power company wanted to run power onto his property. Right now he can make more juice than he can consume. He can't sell any back though.

I'll try to get a detailed description of his off-grid system-or better yet to have him join this forum!

[smelly]

I live in Spain and am in the process of building an off grid system myself. It consists of 32 panels, a battery bank, 4 inverters and a charge controller. It's a piece of cake to install.

So far I have a quarter of the system up and running and have used high power items such as an arc welder and air conditioning as well as the more mundane things. In the last month I have only had one day where I used more power than I used.

[TedTheLed]

Idle, how many watts a day do you figure you need to use??

I've been living off of a 600 watt array for 15 years, and it's enough for me here in Ventura California..of course twice as many watts would be very cushy, and then I probaly wouln't have to fire up the diesel generator as often (it gets foggy for days sometimes..) but unless you're thinking about a huge (well, relative to my measily system) array, a generator part time is the way to go for very high short duration loads..when I run my generator I do several chores at once : run the well pump, run the washing (laundry) machine, charge the batteries (they take 1700 watts--supplied by two charger/inverters) and heat the espresso machine..you get the idea.
Everything is done in less than an hour, and I don't need to run it very often..

[idleprocess]

The house I made an offer on is a ~1400sqft 2 floor house, probably with average-at-best insulation. Due to the zero-lot-line arrangement, there are no windows on the south side of the house save for a skylight in the guest bathroom. This is Dallas, so air conditioning takes that unpleasant edge off the terrible climate that's ever-present from March to mid-September.

Being located in the 'burbs, it's served by commercial utilities, so I don't have to do this if I want power.

As for the size of the system, I live what is probably a rather cushy lifestyle for someone accustomed to being off the grid. I have a computer, a laptop, a home theater system, kitchen appliances (refrigerator, freezer, microwave, cooktop, a small electric grill), a washer and dryer, and air conditioning. Air conditioning is obviously a huge load. The refrigerator is not exactly a trivial load. Electric dryer, but that's on once a week on average. Home theater system sees relatively little use. Computer is on several hours a day - sometimes continuously for days.

I expect that I will go grid-tie, but it would be nice to eventually have a small-ish battery bank so I can power some light DC loads (LED lighting) and select AC circuits (communications and computer, mostly).

I will be buying a new refrigerator when I move. Stove/oven is gas. I will probably undertake some projects to improve the house's insulation (interior takes aggressive advantage of the roof lines), install some LED lighting, and replace the incandecent bulbs with CFLs.

Computer is ~400 watts for 4 hrs/day. Home theater is ~600 watts maybe 1 hrs/day. Notebook is ~15 watts for maybe 1 hr/day. Lighting is hard to judge - I currently use 8x 9W+2x15W for ~12 hrs/day, 1x45W for ~8 hrs/day, 3x 15W ~4x/day and numerous other light fixtures intermittently. Air conditioning is unknown. Washer and dryer cycle once (sometimes twice) per week. The air conditioning in this apartment cycles constantly no matter what temperature I set it to - generally switch it off during the day.

[Darell]

One thing that glares at me...

Hang the laundry out to dry.

[idleprocess]

Originally Posted by Darell

One thing that glares at me...

Hang the laundry out to dry.

An option when I have a backyard to do it in. Not an option in an apartment with a tiny balcony - think it's specifically forbidden in the contract, in fact.

[BIGIRON]

Process - check for subdivision and owner association rules and covenents. Some may prohibit panels, clotheslines, etc. They can be really restrictive and crazy.

[Darell]

Originally Posted by idleprocess

An option when I have a backyard to do it in. Not an option in an apartment with a tiny balcony - think it's specifically forbidden in the contract, in fact.

Ah, bummer. Didn't realize it was an apartment. I'd be surprised if they let you put up PV??

[idleprocess]

No homeowner's association in the neighborhood where I'm looking to buy. 'Seems that HOAs are universally loathed in TX and generally never take off unless they're established by the builder in new subdivisions.

The apartment will be history next month.

[BIGIRON]

Yep, that's the way most HOA's are born. They can be a PITA but the up-side is they can prohibit activities that seriously annoy residents or degrade property values. You want a clothesline or panel but you don't want a chop shop operating out of the garage next door. Just depends on which side of the incident you're on.

Satellite dishes have been a big issue for years, finally getting a court ruling that HOA's couldn't prohibit them in most instances.

edit - BTW - congratulation on fleeing the apartment.

[bgiddins]

Given that this is the "green" forum... I'm very much in favour of distributed grid-tie generation over "off the grid" installations. On a grand scale - imagine if tens or hundreds of thousands of homes all installed battery banks - that's a lot of resources being consumed.

Off the grid makes perfect sense for remote properties, but I think for the "average" person wanting to make a difference, grid-tie is the most affordable, practical and sustainable option for PV solar.

Ideally, enough PV would get deployed on a home-by-home basis that remaining fossil-fuelled baseload generation can be wound back during the day when PV production is high - and sometime in the utopian future, be replaced altogether with clean baseload generation.

I've very ashamed to say I live in Australia, arguably one of the sunniest spots on the planet, and Germany in "cloudy" Europe has more PV solar generation.

[Chengiz]

Originally Posted by bgiddins

I've very ashamed to say I live in Australia, arguably one of the sunniest spots on the planet, and Germany in "cloudy" Europe has more PV solar generation.

Its OK, we live in Arizona and can claim to be behind Germany. I don't know if it is because the lack of incentives or concerns for appearance or what. We are discussing the upgrade of the house. It will have to be in stages.

The one stage will bring the house to net zero. Because we have tile roofing and a multi faceted roof the system will be ground mounted. The panels will be elevated to allow the dogs to keep their "yard".

[Darell]

Originally Posted by Chengiz

Its OK, we live in Arizona and can claim to be behind Germany.

The city with the most installed PV in the US is... drum roll please... San Francisco. A city famous for its fog. The reality of it is, from the "best" to "worst" place in the US for PV is only a difference of 2:1. In other words, the worst place is capable of producing half the energy of the best place. Most folks assume that it is something far more drastic like 10:1. But it isn't the case!

Because we have tile roofing and a multi faceted roof the system will be ground mounted. The panels will be elevated to allow the dogs to keep their "yard".

I can't speak to the multi-facets, as that can be a big problem with roof-mounting. But the tile roofing makes no difference. Most of the roofs we install on are concrete tile. Comp is the easiest, but we don't even charge more for tile. It just is what it is. Puting the panels on poles is a great solution. Not only do the dogs keep their yard, but you can make it better for them by shading larger portions of the yard with the panel pods. You get a 2-fer that way!

[Chengiz]

We had laid on a contractor but he never called. I did as much ground work as I could with no back ground. I only had 8 months of utility bills so the monthly may be slightly skewed. 1850 kWh. a month. Dont know how many panels that is,

The other issue is the power company does not allow for batteries in the system (during an outage the house would be putting power power where they weren't expecting it). So I wonder if there is some kind of auto switching or manual switching to allow for a home to have electric during a lengthy outage.

[idleprocess]

Originally Posted by Chengiz

The other issue is the power company does not allow for batteries in the system (during an outage the house would be putting power power where they weren't expecting it). So I wonder if there is some kind of auto switching or manual switching to allow for a home to have electric during a lengthy outage.

Most utility systems require some sort of automatic disconnect or manual switchover on backup power systems in order to prevent your solar array / generator / battery bank+inverter from trying to power the local grid and potentially electrocuting line workers during an outage or maintenance. Some require the system to go down when the grid goes down (anti-islanding), which doesn't make a much sense given the good auto-detecting systems out there but it should guarantee that you don't put voltage on the line during an outage.

If I'm going to invest a good deal of money in a solar system, it had better be able to power some parts of my home in the event of a utility outage.

[Darell]

Originally Posted by Chengiz

We had laid on a contractor but he never called. I did as much ground work as I could with no back ground. I only had 8 months of utility bills so the monthly may be slightly skewed. 1850 kWh. a month. Dont know how many panels that is,

Certainly it would be good to have 12 contiguous months to take a good stab at this.

If you had time of use metering (where your power during the peak times - when you are generating more than you are using - is worth more than the off-peak times (when you should be using more than you are generating) then you could likely cover your 1850 consumption with a 7kW array.

But the first thing I'd recommend is conservation. By a long shot. Let me put this in perspective a bit....

I have a 2.5 kW system. That sytem covers both our house and our car. The car consumes half of our total usage, so the house and the car are equal parterns in crime (I bring this up since without the car, the size of my PV system could have been quite a bit smaller). 2.5 kW for both the house and the car. And yes, we have a 240V oven. We have forced-air (with gas) heat. We have a Home Theater with a big screen TV, and several computers. We have two AC units. We have two freezers. And of course... an EV. My average monthly consumption is under 650 kWh. Of course we don't have a pool!

The other issue is the power company does not allow for batteries in the system (during an outage the house would be putting power power where they weren't expecting it). So I wonder if there is some kind of auto switching or manual switching to allow for a home to have electric during a lengthy outage.

This doesn't make any logical sense. All the (grid-tied) inverters on the market cut power to the grid in a power failure (by law!) to avoid back-feeding. If you have a battery system, it should be safely usable. Adding batteries to the system approximately doubles the price of the system, and adds complexity and hassle. For most people with reasonably stable grid power it is usually not worth the hassle or expense of adding batteries.

[TedTheLed]

there's about at least a million people in Texas right now that wish they had batteries, and a pv system to go with them. ya know?
I'm surprised Darrel, no batteries at all?

[bgiddins]

Not being a PV owner, I'm not sure on what happens during an outtage... would have thought there would have been a way to scavenge some power from it during the day while the grid was down.

It would be interesting to compare the overall footprint of manufacturing and maintaining a battery bank versus short term generator use in an outtage (given that this is the GREEN forum) - what's the amount of time before the battery bank footprint becomes smaller than that of a generator? How long do you have to run a generator before buying a battery bank would have had less of an environmental impact? I'm sure the initial $$$ outlay for a battery bank is far higher too.

It's a common design in northern Australia to have an "inlet" plug for powering the house by generator to deal with cyclones - there's switching to disconnect the house from the grid while the generator is in use. Had a cousin in far north Queensland who was an electrician (now living in CA) who showed me his system once. I would think that you could run a generator for a couple of weeks or even months before it's manufacturing footprint & usage emissions outweighed the footprint of manufacturing enough SLA/AGM/whatever batteries would be required to keep a house going on PV alone. Battery banks need to be able to cover worst case scenarios, otherwise you're still going to have to resort to a generator backup to charge them to cover any shortfall in PV generation anyway.

So in a nutshell, I would think "PV + backup generator" makes more sense than "PV + batteries + charging generator" where grid-tie is available.

[Brock]

I have to get Bill (bb) over here from our other usual haunt Wind & Sun, he is now a moderator over there.

Anyway, there are three basic systems. Grid Tied / Batteryless, Grid Tied with battery and stand alone (can't be tied to grid).

The most common inverters out there you can get at any big box store are just plain old inverters, 95% are modified sine wave, not a true sine wave and the freq can vary from good to bad depending on make. Most sold have automotive cigarette lighter plugs and just plug in and run small loads typically under 300w, but can get quite large, up to 5000w continuous. You can get them in sine wave but they are not very common and about triple in price for the same wattage.

Then you have the typically larger and more expensive grid tied versions either with or without batteries. Any grid tied inverter has to be UL rated to disconnect from the grid in the event of a grid outage and won't reconnect to the grid until the grid has been back on and stable for a minimum of 2 minutes. There are ways to trick a non battery grid tied inverter to come on, but we won't go in to that here.

I have a Xantrex XW6048, it outputs 6000w continuous at 240vac (120/120 standard US house wiring) and connects to a 48v battery bank. It is a grid tied with battery inverter. It can back feed excess power to the grid, but the advantage is in an outage it disconnects from the grid but still supply's power to the load side.

If you think of an inverter like a computer UPS a grid tied not battery version only plugs in to the wall and has no outlets on it, it just pushes power back out the plug side to the house/grid. The grid tied with battery is more like a standard UPS. It can also push power back out through its "plug" but also has outlets on it that stay on even when "unplugged" from the grid or in a grid failure. My system started out as a large UPS and has just grown from there.

Battery based inverters however have their down side. Obviously you have to buy batteries, typically enough to supply power for three days with charging, mine cost about $2600 and will likely last about 10 years (hopefully longer) depending on use. Batteries also consume power all the time, used or not so just sitting they eat up some of that solar power. Typically in a lead acid they are about 90% efficient, meaning if you pull 100 watts out of them you need to put 110 watts back in to get to a full state again. There are some better batteries like AGM that are 96-98%, which is what I have.

So say you have a 1000w solar array. A grid tied batteryless inverter might put out about 900w back to the grid (inverters and associated wiring are typically about 90% efficient). If you had a battery based system you would likely get about 800w back to the grid (same 90% for inverters and another 10% for charger and battery losses), thus lengthening your payoff time, but with the added benefit of have power when the grid is down. I look at my system like looking at a 6kw automatic standby home generator, with the added benefit it may someday pay for itself instead of sitting looking pretty until the power goes out.

I almost always recommend a batteryless system to people who ask, less maintence, less mess, quicker payoff.

[idleprocess]

Originally Posted by Brock

I almost always recommend a batteryless system to people who ask, less maintence, less mess, quicker payoff.

Almost sounds like someone in my shoes should just look at UPSs for important circuits instead of a small battery bank on dedicated circuits?

[Brock]

Yes, or heck even an inverter that can be run from an idling car if possible. You can easily run a fridge & freezer from just about any idling car and a $100 inverter.

But yes UPS's on certain equipment and grid tied battery less solar panels.

[Darell]

Originally Posted by idleprocess

Almost sounds like someone in my shoes should just look at UPSs for important circuits instead of a small battery bank on dedicated circuits?

I agree with Brock... and you. You can make your own small UPS that is solar-charged. In other words, WAY more cost effective to just back up important circuits, instead of the entire sheebang.

[Darell]

Originally Posted by TedTheLed

there's about at least a million people in Texas right now that wish they had batteries, and a pv system to go with them. ya know?
I'm surprised Darrel, no batteries at all?

Well... I do have some batteries that are solar charged. But they are not charged from my main system that provides AC to the house. I have some panels that provide nominal 12V, and I charge some batteries in the office with those panels exclusively. Those batteries then run my whole-house low-V night lighting (single 5mm LEDs that poke through the cieling sheet rock in important locations), and they charge all of our portable devices (bicycle GPS, cell phones, Ipods, etc) and they run the laptop. With a small inverter I can run several other larger devices if I wish.

You have to balance the cost (both financial and environmental - I need a word that covers both of those costs, because when I just say cost, most just think of financial!) and hassle of adding batteries with the likelyhood and the inconvenience of possibly needing them. I have lived in my current home for almost eleven years now. In those eleven years, we have been without power for a grand total of under ten minutes. The whole time combined. Our lines are all burried, and they have proven to be quite reliable. I have no burning desire to buy several thousands of dollars of batteries to hedge against a long blackout. If one DID happen, I'd be OK... and would be able to power everything during daylight hours. Trust me.

And on top of that, I really DO have battery storage. Right there in my EV. Modern EVs will have the ability to put in and take out power. Wouldn't that be awesome to have your totally clean "generator" parked right there in the garage waiting to help in an emergency?

[idleprocess]

Originally Posted by Darell

I have lived in my current home for almost eleven years now. In those eleven years, we have been without power for a grand total of under ten minutes. The whole time combined.

Everywhere in the DFW area that I've lived has had its share of regular power interruptions - seems to have something to do with the regular thunderstorms that blow through the area. 12-24 hours a year of downtime would be a good year - and I live about a mile from a "load-following" power station.

But that doesn't seem to be worth a few thousand dollars worth of batteries in addition to the much-spendier inverter.