Hmm, well, if you bought it on eBay, I suppose you can resell it on eBay, ja?

Apologies for contributing to your enthusiasm with my own. :^p The other people I know who have done this, have done it as part of what was presumably a multi-thousand-dollar remodel involving covering their entire roof with solar panels, and were in California, where the rules may be different, the power companies and/or State may offer subsidies, etc.

There's another big danger that I'm surprised the utility representative didn't warn you about. Household electricity is, of course AC - alternating current. The instantaneous voltage varies from a positive to negative peak voltage, usually in the form of a sine wave. However, there's no law of nature that will require all sine waves coming from different sources to be in sync. In fact, they will usually be out of phase. So if you have a solar panel, or a generator feeding an inverter, it will likely be out of phase with the current feeding your house.

The least of your problems then would have a negative voltage add to a positive voltage and cancel out, reducing your voltage, which is bad for anything trying to run off it. A bigger problem would be to have a positive voltage add to a positive voltage, increasing your voltage, which is worse for anything trying to run off it, and can cause fires.

Approved inverters will have circuitry that will detect the phase of the line current and create its current in phase with the line current.

It you want to know why certified inverters are pricy, have a look at page 11 of this presentation that shows the inductive and capacitive load banks used for anti-islanding testing.

The size of the copper conductors between the capacitators and the size of the inductive coils gives me the impression we're talking serious current here.

A search for that particular UL standard also turned up the XPX-A1000 inverter that is UL 1741 approved and costs $350. The only drawback I'm seeing is that it needs a solar panel of 100 W minimum. But that might be an excuse to get an extra solar panel, no?

It also comes with an ethernet port to enable you to monitor it, which sounds cool. It would be nice to be able to jack in your laptop and download the power production data on a regular basis.

Josh --- it's definitely not your fault. I think that I had already bought it when you got excited. We'll have to see whether Mark's inventive side says "gadget! I want to find a way to turn this into something more useful!" or whether we resell it, but you're right that it's probably not a big loss either way.

Edward --- Good points. I think the electric guy was less interested in what would happen on my end than with what would happen on the grid. But extra research elsewhere suggested the risk just wasn't worth it.

Roland --- We'll have to crunch some numbers and see whether that more expensive inverter is worth it. I really do think that tying into the grid makes a lot of sense, deleting all of those batteries from the system! The other thing we've been considering is making our own virtual battery using one of your other suggestions --- pumping water into tanks on the hill. I haven't looked into how much it would cost and how much height we'd need to then turn that potential energy into electricity using some kind of hydropower setup, but it certainly would be a cool batteryless arrangement (and give us more water to use on the farm.)

Considering your goal of having power in case of a powerline failure, you're probably going to be needing those batteries anyway.

As for the hydro scheme, on a small scale the efficiency is probably going to be small because of the size effect on pumps, turbines and generators that we've discussed earlier. But since your solar power is essentially free you might not care too much about that. But with 50 W of power you're not going to pump a lot of water very high.

The power needed to pump up water equals ṁ·g·Δh, where ṁ is the mass flow in kg/s, g is the strength of the gravity field (9.81 N/kg) and Δh is the height in meters. With 50 Watts you could e.g. transport 0.1 kg/s (or L/s) up 50 meters. And that is without motor, pump and friction losses, so in practice it will be less.

When using the water in the reservoir, suppose the pump+generator is 50% efficient (which is optimistic, IMO), and you want to sustain a load of 100 W for 8 hours, knowing that 0.1 kg/s of water dropping 50 m yields 50 W, you'll need 0.2/0.5 = 0.4 kg/s of water for 8·3600 seconds which is 11.52 m³ (406 ft³) of water! If you want to go with tanks that's 10 of those big (1200 L) IBC's you've got to haul up a 50 meter hill! Or a reservoir of 12 by 12 feet and three feet deep you'll have to dig. And it would take only 32 hours of sunshine to fill up the reservoir. So after a week your reservoir is full and then what are you going to do with the extra power?

If you build a big enough reservoir on a suitable location you might catch rainwater for extra power. But be very careful when designing a water reservoir on higher ground! I would consider that a job unsuitable for a layman. Consider that catastrophic failure is always an option! At least put it someplace where a potential flood can't ruin your house or garden. Remember the 1985 Stava tailings dam failure.

We don't mind being very minimal in the event of a power outage, and we sized our battery system for that minimal use. But we oversized the solar panels because, well, they were cheap and looked interesting.

I was thinking of the tanks being a one day energy storage setup to utilize the bit of extra juice the panels will put out that won't "fit" in the batteries during the day. Then, every night, we'd let the water drain down (perhaps into a lower tank, or to water the garden, or back to the source, or whatever) to power lights as we read. The load I'm talking about is much less than what you're talking about --- maybe 20 watts for two hours.

In that kind of setup, I don't think we'd be talking huge tanks --- our thousand gallon tank alone might be sufficient. The trick, in my opinion, is to figure out how high we have to place the tank(s) to work with the lowest end hydropower generator I can find.

I think the best use of your additional solar output would be to invest in additional battery packs and go ahead and store the power. Then think of installing 12 volt lighting in your trailer and use car chargers for your laptops. Think camper trailer. Almost everything is 12 volt but uses a battery charger when plugged to charge the batteries. Anyway this removes the loss you experience trying to convert power and reducing your bill is better for you than trying to add back to the grid.

Roland: Often times your comments cause me to go and research different aspects of your post. Thinks for sharing your knowledge and dusting out the cobwebs in those hard to reach corners of my brain.

We're definitely thinking of going the CD lighting and car charger for laptops route. Once we finally unpack our powerpacks, I'll be able to see if we can get DC out of them while having the solar panel plugged in, which is something that was a little vague about the online documentation.

...make that "DC" not "CD".

Anna -- Why shouldn't you be able to do that? If you hook up a DC load to the poles of the battery, it and the solar panel (via its controller) should be in parallel from the viewpoint of the load.

Erich -- You're welcome! It's nice to be appreciated.

We definitely could do that if it was just a battery. But the powerpacks are a battery enclosed in a casing with an inverter, etc. They have a car lighter type plug, but I'm not sure yet whether we'll have to use that to plug in the solar panel or whether we'll have it available to plug in a DC load.

A thousand gallon tank is 3785 liters or kg of water. If you need 20 W of electrical power, the question is how much water power you need. Let's assume a 25% efficiency of the pipes/turbine/generator/rectifier combo, which doesn't sound too wildly optimistic. So you'll need 80 W of water power.

If you have a 20 m high hill around, 0.4 kg/s of water flow would give you around 0.4·9.81·20 = 78.5 W of water power. With the assumed efficiency of 25% that's around 20 W of electrical power. A completely filled 1000 gallon tank would then last for 3785/.4/3600 = 2.63 hours, say 2.5 hours.

According to my literature, for small hydropower setups a so-called cross-flow turbine (a.k.a. Michel-, Ossberger- or Banki-turbine, see below) is best.

This is because it has a flat efficiency curve over a large flow range and it is easy and cheap to build. I've seen a TV show (planet mecanics) where a guy welded one up himself from two steel discs with slots cut into them and some metal strips with a curved cross-section!

I think that possibly the hydropower generator you're talking about is one that Mark has considered building. We even picked up a squirrel fan cheap at a yard sale this summer in preparation (although that might also be earmarked for our furnace...not sure.)

I've got a gut feeling that water at a couple of bars of pressure would make short work of your avarage squirrel cage fan! It's probably much too flimsy.

For starters, a squirrel cage fan is usually a centrifugal fan, which has a mounting point at one side only, since the other side is open. A cross-flow turbine will probably need bearings on two sides! The high-pressure water is converted by a nozzle into a high-velocity stream of water which then hits the blades. Second, for a cross-flow turbine to work, you'll need curved blades; The curved blades deflect the water stream twice (going into the cage and coming out) and the change in momentum (impulse) causes a force on the turbine blades. This can generate significant forces on the turbine blades.

BTW, you can see the home-made steel cross-flow tubine on this video. It's quite a bit sturdier than a squirrel cage rotor. I'd say the steel blades are about 1/4" think. And you can see a 10 bar jet of water.

Hello,

I'm new to solar except for using a small panel for trickle maintaining car batteries. How do I sell power back to the grid with solar panels?

I bought a few panels a few months ago and a regulator. However, I am under utilizing them and what to charge the grid! I now understand i need an on-grid inverter but they are too expensive. Last week i finally found one at reasonable prices from SolarTorrent.com. I tried looking for reviews via google but found none. Can someone tell me whether their on-grid inverter's specs is a reasonable good inverter to buy? Thank you in advance.

Kelvin

My understanding is that each utility company has their own list of approved inverters. It's not enough to simply have a UL approved inverter. So, I'd recommend contacting your local electric company asking them for more information.

You guys are so far off it's unreal. If you would have read the specs and looked into the plug in grid tie inverter you would have seen that the inverter actually only applies power when it senses that it's plugged into the power grid through your plug in your house. It's called island protection and the inverter you got from ebay has it. If the power on the grid goes out so does the inverter power. On the note from the electronics guy about the sine wave not matching if you would have read about the inverter you would see that the inverter matches the sine wave before the power goes out. I am an electronics technician with over 20 years expierence and get mad when I see people talking before they do some research. These new grid tie plug in inverters are being use legally all over the US. The reason that your power company employee said what he said is because you did not gove him all of the information.

I agree that the inverter has island protection. However, it's definitely not legal. Each power company makes their own rules about which inverters are allowed, and ours has a simple list of permitted brands. Since our inverter isn't on the list, if we plugged it in, we would be breaking the law.

breaking the law and not doing what the power company says are two COMPLETELY different things.... you realize that right?

That's an interesting distinction. I certainly don't know much about law, but I do know I had to sign a contract to get hooked up with the power company, and even though I didn't read the whole thing, I'm pretty sure part of it was agreeing to abide by their rules. If you sign a contract saying you'll do one thing and then do something else, presumably that's breaking the law. You can definitely sue someone for doing that.

I did a little research on the use of these plug and play grid tie inverters. While it appears they meet all the requirements of UL I have not seen one yet that was UL listed, nor CE either which is what the rest of the world seems to go by. In Florida, UL approved is required by code, therefore, it is illegle to use these plug and play grid tie inverters in Florida. Other states may have similar codes. Still, you can buy UL approved grid tie inverters for just a little more than what these cheap units sell for. The Emphass 215 sells for around $150-$200 supports up to 260w solar panels. Other models are also available. These units are made to mount on the back of a solar panel, and are made for outside use. For an array of solar panels you use one on each panel (or two smaller panels). If you want grid tie for a small PV system these are what you want.

Dennis --- Sounds like you did some real research! I'm not sure the Emphass 215 was around at that price when I did this research a year and a half ago, or I probably would have gotten it. Drat!

Enphase is not cheap, It looks like $160 for 215W, Plus shipping, It will cost near $200, you need special connector, It cost another $50, Plus special 220V wiring/socket, and separate switch, It costs near $700+ upfront for one 215W unit VS $129 ebay 600W plug-in inverter. price will be reasonable for 10+ unit together, it is a good idea.

I am doing $129 plug-in inverter with $200/200W solar panel for testing, If everything go well, I will switch to enphase with 2KW solar panel $7000 project with legal.

Well, I have an odd way of looking at cheap vs. expensive. Having spend nearly $100 on an inverter that isn't legal, I figure spending twice that much on one that is legal would be a bargain.

Of course, if it costs $700 once you wire it in, that's not cheap... Not sure if you're counting the solar panels and parts that come with the panels in that price?

Enphase Inverter is really a good choice, Although it is UL1470, I am in Canada, It is still not legal in my area, Power company do not approved them yet. In some area, They need a special version which cost $200/Each, USA version is Appro $150/each.

Right now, I am using a cheap grid tie inverter(GTI) power jack 600W version 3.3 for $129 include shipping, I got my UL 205W Solar panel from USA for $205 plus $100 shipping, Also $14 for cheap Ebay power LCD meter, With about $30 for MC4 connectors, cheap DIY Angle iron mounting, wiring, Total cost near $500, Rightnow, GTI Efficiency is about 89%, Daily production is 1KW/H and it will produce 1.5KW/H summer, it is not big enough to reverse the meter just supply my own power, It saves between $15 cents to $40 cents daily depend on your electricity rate.

This cheap GTI system is not good for high power design, They don't handle parallel solar panels well due to MPPT tracking unless you can get 100% same panel with same Volt/Amp curve, Overall power effeciency will easily decrease to 60% to 70%.

Enphase inverter is much better design/idea and it is UL listed for USA incentive, overall power efficiency will always be 95%+, each solar panel need 1 inverter, you need to wire dedicated 230V outlet and 230V power rail, it is good for small and medium system and better overall efficiency than old traditional String inverter which listed 95% but Overall real world Eff. is 80% to 90% due to mis-match Volt/Amp curve in solar panel, it is much easier to expanding your solar farm to increase your power production, However, you need to start $6000 and easily up to $20,000 which is same cost as traditional String inverter system.

Anyway, I know that there are people using Power jack cheap GTI in China, Also Europe as well as Austria, I am wondering that when they will be UL1470 listed? Even Teenage can install it themselves.

Thanks for the price breakdown! We already have a couple of small panels that we got when we thought the other inverter was going to work, and they came with most of the connectors I think we'll need. I guess we probably should do a bit more research and get an inverter that will work. It's a shame to have solar panels sitting around not being used!

For best value for money, every panel should have its own MPP tracker. Preferably built-in and callibrated by the supplier.

Otherwise you'd need ones that you can adjust yourself. They're not that hard to build. A simple one consists of a sawtooth voltage generator, a potentiometer, a comparator and a mosfet. You can find schematics only.

Tom, you are right that there is additional cost to install an Enphase grid tie inverter for a branch connection, but they sell on ebay for $24.99 each plus shipping. All the other stuff you will need regardless of which kind of grid tie inverter you use. Even the AC Circuit has to be brought in from somewhere. As for certification, I'm surprised Cannada does not accept the Enphase M215 inverter. Looking back at what others have said about grid tie inverters, it is apparant most of us know little about how they work - First they do not generate voltage that is entered onto the grid, just current. To do that they must get voltage from the grid, sync with the grid before allowing any current to flow onto the grid. Where some of these cheap plug and play units may not meet certification requirements by power company's is a requirement (in US) of a five (5) minute delay after a grid failure before turning inself back on. This is very important and also helps to protect all the electronics in your home. Cheap today could cost much more tomorrow.

I'm sorry, somebody has probably already pointed this out to you but I just don't have the time to read this entire page (I'm at work stealing some moments).

The gridtie inverters are indeed a good investment. Firstly, not to worry about that lineman due to the fact that the gridtie inverters are mppt technology and utilize pure sine wave (at least our is). They don't even run unless there's a current to match (so if the power is out guess what? Yup, there's not even electricity for you even with your gridtie inverter).

As for cost, man those chinese people are spitting these out a mile a minute (we purchased one of theirs, a 1200w but we've since put in on the shelf as offgrid is more appealing to me since we invested so much in all these batteries around here ";-). At one time we had the solar tracker connected to it....oh and before I forget, people you DO WANT a solar tracker!

Sorry gotta run

Regarding everyones comments on solar grid tie inverters.

I was wondering if everyone could help me.

I noticed that part of the blog and comments recognized the legal nature of the issue. I want everyone to know that before I ask my question that I am in no way concerned of legalities, all I'm concerned with is paying as little into my PUD Electricity bill as possible. If I have to break the law then so be it.

Can anyone help point me into the direction of from whom or where I could purchase the easiest and cheapest solar panel and grid tie converter kit? I would be grateful for any advice and send a finders fee to return the favor of your generosity.

Any help is much appreciated, and needed.

Sincerely,

Just another cheapskate and proud of it.

Cheapest way so far has been through ebay, 2 solar psnels I bought 1 at a time 210 watts cost 420.00 delivered, a plug and play as they're calling grid tie inverters, 300 watt cost 90.00 counting delivery, so 510.00 to get started, I have cut my energy usage already now am adding these so I'll try to post savinds soon, hope you get started soon [ comment to medicalbillings question]

can someone please point us to one news report of a fire being caused in the last couple years by these inverters?

The reason you will probably never see a UL listing for these is the application of the power generated can't be controlled. Imagine someone with a typical 15 amp household circuit plust a 1200 watt inverter or multiple 300 watt inverters into this line. Now a load is also place on the same line lets say a space heater 1000 watts and a hair dryer 1200 watts, that is 22 amps at 120 volts. You now have a situation where you can run both of these devices because there is 2 power sources on the 14 Guage wire. This is an over load condition and will over heat the wire but will not trip the main panel breaker, it only sees the power being drawn thru the breaker.

Add it up, power sources main 15 amp breaker plus 10 amps from the 1200 watt inverter. that is 25 amp potential in the 14 Guage wire, normally those kinds of amps require a 10 Guage wire to be legal and prevent wiring over heat conditions.

There is no control over how these plug and play inverters are applied to a home wiring run, there is a reason why permits and interconnect agreement exist. Dedicated solar back feed breaker and wiring is designed to prevent problems. It is to protect you against dangerous conditions.

It is a good practice to install a separated circuit for your grid tie inverter with a proper fuse. So you don´t run into dangerous situation with overpowering the lines. And I guess you will not produce as much solar power that you overload your main fuse in your house.

Excellent point by Solar Dave. A fire could easily be started by undermining the circuit protection on a circuit in your house, in fact,is quite likely if the cable is overloaded excessively. You need to be very careful what circuit you are plugging into to avoid too much current being drawn by other devices on that same ciruit without the ability to trip an over current device (MCBs in Ireland anyway). Best way is to make a dedicated (appropriately sized and protected) spur from your panel and plug in there ONLY. Consider very 100W of power available from the inverter will add about an amp(in US/Canada and half that in Europe)to the cable before the MCB will trip, so a major safety concern.

First of all the Grid Tie Inverter is design to supply AC power in sync with the grid and with a slightly higher power than the grid. So THERE IS NO shine wave with positive power to the negative grid power . Do not mix the Grid Tie Inverter with a regular inverter that is plugged to 12V of your car. Second if, again, you have a Grid Tie Inverter plugged in a wall socket, when is unplugged it shuts down. That is a feature of a Grid Tie Inverter. The power co. needs mainly to be sure your Grid Tie Inverter is certified to do that.

Its sound far to danuous t for DIY but what I want to know how do they send juice down the same cable as juice coming up ?

An unplugged inverter would not have energized male prongs. If its unplugged, the inverter sees that as a power outage and shuts down.

Voltages would never add together as was stated earlier - they would simply be in parallel - thus supply additional current as is desired. The comment above is however correct about them fighting against each other should they be out of phase. That would surely happen with an automotive style inverter; but any grid-tie inverter has circuitry to maintain synchronization.

Dave's comments about the breaker panel supplying current as well as the inverter making an unsafe current level available is a valid issue; though the actual results would depend on where in the wiring the load was.

Ga power has instructed me to remove my GTI from the grid ,which I have; because my inverter dosenot have a UL1741 listing. My utility bill will go back up about 50%. That will be $1000.00 to GA power increas per year. I not sure this is legal; but it dosent matter; Ga. power controls the power switch and other things. MY GTI SPEC SHOWS ANTI-ISLANDING!

From previous post. FOLLOW THE MONEY!!

I have a 100w solar panel and am borrowing for curiosity sake 3 more 100w panels that feed my battery. After the charge controller goes into dump mode (usually 10:00 AM with 100w panel and a 175 Ah battery) the Power Jack Plug N Play inverter goes to work. Usually on a sunny day we produce .8-1.2 kWh of energy that goes through the inverter. I have had the same inverter for almost 6 years and I haven't had a single issue. I have monitoring equipment attached to the inverter for information and records, it matches the frequency, wave form, and voltage of the grid power exactly. The worries about frying linemen in a outage are 99.9% wrong. The inverter requires the grid power to turn on and match the power produced with the grid requirements. Without this grid 'template', the inverter doesn't even allow electricity from the panel to even enter the device past the LED fault indicator. I wouldn't put 300 watts of solar into the 400w rated device because I would worry about over heating. A simple form of 'insurance' should the fan fail or cannot handle the amount of heat generated, is to attach the inverter to a 'control board'that is then attached to a wall or stud, with the fan/solar contact side placed so the heat is able to escape quicker and easier, usually facing upwards. This allows the heat to vent out the top easier and faster due to the fan and vent being on the upward side as heat rises. This offers a buffer zone should the forced ventilation of the unit fail. My inverter has been running consistently at 350w being since 7:00 this morning, it is now 1:30 in the afternoon and the inverter, while warm, is not even close to overheat. We currently have 400w of solar and not a cloud in the sky.

The OP started with misinformation, then others just piled on.

As at least one other poster mentioned, these cheap-o inverters do NOT continue to send power down the grid to shock the unsuspecting power company workers.

That means, that the male plug isn't going to shock you either, duh!

C'mon. Irresponsible post by the OP and then the flood of misinformation is disturbing.

I was wondering if the easiest way might be a solar array and grid tie inverter. And for power outages a gas powered generator.

OK---so lets say this low cost inverter is questionable at best. I want t do a self install and build it as I can afford it. So--lets say I start with the inverter----do I need to contact the power company at all? Once I have the inverter installed I wan to start with a few panels of the ones you plug into one another. Please advise----oh--and I am in NORCAL

I believe the Federal Government policy is "Don't ask, don"t tell"

some utility companies have installed electronic "smart meters"on residences so they can eliminate having human meter readers. These also tell the power company that you are pushing power back into the grid.I have had a grid tie system for about 6 years without telling my power company, then they installed The smart meter,2 weeks later I received a letter telling me to shut it down and get it permitted and fill out the agreement with them.Luckily I have friends who are electrical contractors and this process was not that hard for me.This is not the case for most people,but if you have an old mechanical meter and you never produce more than you consume they will probably never know.Also there are devices sold on ebay called grid tie limiters which do not allow power to go back to the grid but let you run things using with solar panels and grid tie inverter. They prioritise the power from the solar panels when its available.these smart meters would not be able to detect the system as the grid will receive no power from you. I personally have not used one of these devices so i have no idea how well they work, but it sounds like it might be worth looking into for some people.

I see a lot of comments about (plug n play micro grid tie inverters not being safe and not able to work well)

I will make a few comments here.

How does a grid tie inverter work? First of all when you plug it in, it gets it's native sinewave from the power company, and matches it's own from the power company. When the power goes out (wall voltage dies) it stops producing electricity automatically because there is not sinewave source from which to match. This is called anti-islanding. Even the most basic "GRID TIE" inverters do this. The key word here is Grid Tie. Normal inverters should never be plugged in, as they will cause the problems indicated in other comments. I can see that a lot of people here are making comments with lack of knowledge in this area.

One comment noted that it's not safe because if you unplug it, it has a male plug, and that someone touching this might be injured. The reality is, as soon as you unplug it, it stops producing electricity since there is no sinewave source.

Causing a fire? Well yes it's true that there is a potential for this, but so is there a potential for anything you plug into wall current, to cause a fire. You can think of these micro inverters as an electrical appliance. (Something that does not work unless plugged in). If your grid tie inverter has a circuit breaker, fuse, etc, it will most likely trip it's own breaker or fuse before anything bad can happen. The same goes for the wall outlet, it's protected by a circuit breaker in your home.

Sure there might be regulations in place to prevent legal use, so sure you should check with your local area for what the regulations are. And what certification is needed.