Power inverters

[W2INR]

I have decided to make this year my crossover year with the utilities. I am designing an alternative "Hybrid" system for my home.

The system I am looking towards will have solar, wind and a generator system combined to provide the charging power for storage batts. Eventually after testing and fine tuning the system I would liket o fully disconnect from the grid but for now I must get my feet wet if you will.

The power inverters are costly and I was wondering if anyone here has built any or would have designs and schematics for 3-5 kw units that cold be stacked with others? I am sure building them will reduce costs.

Any thoughts?

[WA1GFZ]

Gee my pdm generator for the 160 rig will do about 4 KW just add a transformer. I think the N9NEO converter would be perfect  Just feed either a 60 hz. sine wave.

BTW they just came out with a new cheaper solar panel about 2 months ago.
You might want to hold off until they hit the market.
I have a buddy in Palmdale Ca. with a wind mill...that will run you some bucks but his system in operation made about $100 an month. Pretty windy out there though.
I think his does 10 KW with 8 foot blades if I remember.

[W2INR]

Well consideraing the cost to heat and have electric in my home the cost of alternative sources has become competitive and the costs are just going to increase so this is a good time to start experimenting with this stuff.

I am actually going to approach this as a hobby at first. Lets see I have spent  many dollars on my radio hobby and if I was to spend the same amount on this I would be saving money . My heating and electirc some far this winter season has been averaging $700.00 a month. On an annual cost analysis I am already spending the monies to convert over so I have the money to invest.

I will check into the N9NEO converter. I was not aware of it. Is it on the net Frank?

[N2udf]

Gary,
Try this site for ideas.Lee...http://www.solarproductsource.com/storehome.aspx?CategoryID=24

[Tom WA3KLR]

Gary,

Look for a heavy white extension cord going to your neighbor's house.

[K6IC]

Hi Gary,

Sounds like you are embarking on an intertesting project.  Have recently built an off-grid system for a remote QTH -- out in the stix.  To me,  by far the least expensive energy you will find is on the grid ... by far.  Subsidies for grid-tied  systems will help.   Batteries are very expensive,  and need constant tending and awareness on the part of the users.  Being off-grid is kinna magical -- Solar silently charges batteries and provides power to loads.  Magic.  Batteries are large,  heavy and expensive,  AND have a limited useful life.  Generators  are expensive to run.  In my system,.  my monthly cost of on-grid electricity would not even pay the interest lost on the investment in the batteries alone.

Also,  most of the charge controllers (Solar and WInd) are switchers and generate RF noise.  Inverters, also, are heavily digital things and generate their share of noise.  All of hese noises are manageable,  tho.


As you know,  the simplest and most efficient system, where one has quite a lot of sun,  is the grid-tied Solar system,  without batteries.  Often there is a governmental subsidy for the grid-tied systems.

Our electirc utility is PG & E,  which I truly HATE,  but there is a lot to be said to flipping a switch,  and not needing to know the state of YOUR power system.

For you in the East and North,  am sure that heating in the winters is a big expense.

73  GL with the project  Gary,  and  Thank You very much for this great site.   Vic ex  KF6RIP -- now  K6IC   .  .

[Vinnie/N2TAI]

Interesting concept.
At work we had a solar wall (air heater to boost the make up air system) installed on one of out bigger buildings it cost about $80,000 and cuts heating costs about $1100 to $1500 per year. Good thing we got a government grant!. The big problem is that there isn't any significant sun in Nov or Dec and it doen't get full sun until after 1:00PM.
I would think the cheapest way to go is to set up a bunch of solar panels wirhed to some electric heaters, no inverters or batteries, whatever it makes you don't buy and the heaters dont care about being run od DC.

[WA1GFZ]

My solar cost me about $4K and the house is warm enough to walk around in shorts if the sun is out. I save 300 to 400 gal. of oil each year. I built it in '84. Also turned a car port into a room adding 400 square feet to the house.

[k3zrf]

Hey Frank,

How many panels (sq') did you construct. Air, water? And what do you use as storage?

[K6IC]

Yea,  Frank,

Is it safe to assume that your "Solar" system is passive Solar collector,  ie collecting radiant sun energy through glass (and possibly storing it in thermal mass) ?

Current prices on Solar panels have been at abt $4.50/MPPwatt or a bit more.  This is without any subsidy.

What is the story ?      Vic,         K6IC

[NE4AM]

If you can string 10 batteries in series to get 120 volts DC, you won't even need an inverter for much of your stuff.  A lot of stuff in your house will run from DC.  The only appliances that MUST have AC are things with induction motors, (magnetic ballasted) long-tube fluorescent lights, or transformers.  Stuff like blenders, light bulbs, power drills, etc. will run from DC.  Although I haven't confirmed it, the solid-state ballasted fluorescents, as well as most switching power supplies ought to run fine from 120V DC.  Then you can get a small inverter for those few things that must have AC. 

You can build a chopper to convert 120V DC to 120 VAC pretty easily.  It takes 4 MOSFETS and 2 driver chips.

[WA1GFZ]

Dave that would produce a square wave signal very dirty. It is better to us a high frequency converter like the N9NEO converter and make sine waves at 90% efficiency. A chopper would also need a much bigger transformer.

[NE4AM]

OK, then you have a master switch to turn off your refrigerator & its induction motor while you are on HF.  If the fridge is well stocked with 12oz bottles, it will stay cold a LONG time.

[W2INR]

I am approaching this project very seriously. I have done a lot of research  on this stuff. The system would have to grow over time with any type of budget I could create for this.


I did some quick math averaging our cost to heat and light this place over the last three years.

Our annual average over the last 3 years has been $4340 a year. Keep in mind that our electric doubled over the last year. It went from $2.66 a KWH to $4.61 a KWH just over the last 12 months!  More increases are guaranteed!! .

Heating would be handled with solar and wood.

The sytsem I am looking at costs around $40,000 if purchased as a complete sysem. I know I can reduce those costs buy building some of the gear and shopping around for the rest.

The State of NY will give a close to 37% in rebates and tax incentives to convert and there are also Federal incentives to do the same so I think the realistic number would be closer to $15,000 and at the current cost of operation here at todays pricing the return would be realized in less than 5 years.

The type of system I am looking at is linked below. I would build the inverter system, I don't need the tower or tower wiring kit so I have already chopped off almost $12,000 from the system. Now if I was to tie into the grid and if I had excess I could charge the utility! Again more savings.

I would eventually add solar panels to also help in the charging of the batts during the summer months when the winds are not as intense up here .

It is becoming clearer to me with every rate increase that the alternative systems out there are becomng more competitive with every increase.

Here is the system I have been looking at

 http://www.utilityfree.com/wind/remotesys7.5.html

[k4kyv]

Our annual average over the last 3 years has been $4340 a year. Keep in mind that our electric doubled over the last year. It went from $2.66 a KWH to $4.61 a KWH just over the last 12 months!  More increases are guaranteed!! .

You pay $4.61 for a kilowatt-hour?  You could run your own diesel generator for about 1/10 that.

We pay about 7 cents.  I knew our cheap subsidised TVA power cost less, but I was thinking the national average was about 10 cents.

[K6IC]

Hi Gary,

Yea, the $$ / Kwh  seems off by a factor of 25 of 50.  Here in CA we average about $.17/Kwh in a 3-tier residential bundled rate  plan.

The interter listed in the package was on sale late last year @ $2200.00 plus shipping.  Now they are abt $2540.for the Xantrex  5548 SW Plus (Plus has FCC Class B cert.).

PLEASE avoid the multiple strings of batteries.  This causes multi headaches of all of the interconnections,  and a miriad of cells to keep watered.  Also, these inexpensive cells seem to leak at any penetration of the top cover, and they are short lived.

Since U did NOT ask,  I would suggest that U might look at the Rolls Surette batteries.  Batteries like these are fairly large and allow a single string to be used -- many fewer probs,  and rated at 3300 cycles ant 15 year nominal life.

My favorite vendor is Colorado Solar Electric       www.cosolar.com            At least for the Surette batteries, and other items including Solar panls.   I have no interest in the company,  just an honest small company with a knowledgeable owner who installs systems and has a lotta experience.

If you can avoid the batteries,  and make your system grid-tied only,  the grid is your battery and you avoid all of the heartache.  Realize that when the grid is down,  so are you (at least usually).

But who am I to advise you.  73  GL       Vic      K6IC

[W2VW]

Hi Gary,


   Since you have the good old electric utility already hooked to your house, why not make it work for you. Most utilities will deduct power that you supply to them. Configure your system so it will clock perfectly along with the 60 hurts (really hurts if it isn't in phase) from the power company. Run all your stuff in the home as before but use your solar power to supply the utility. Run that kiloWatt meter BACKWARDS just like the used car business. Use them like a big battery. No more worries on shady days or nights.
    A type A like yourself should have all this running properly by, say, the end of next week.

[W2INR]

Wow , I screwed the pooch on that last post . Those numbers were daily averages for the last two years ( 04, 05). It is costing about $11.00 a day this year.
 

Revised costs


We use approx 76 kwh per day here. ( these are an annual average provided by National Grid)

National Grid delivery charges per kwh

Delivery cost            3.0649 cents
delivery adjustment   2.924 cents
sbc charge p           .172900 cents
trans rev adj            .21000 cents
tariff surcharge   2%

delivery total            6.499236 cents per kwh.

Electric supply charges   per kwh  = 8.4430

Total charge per KWH    14.942236 cents per kwh

Apprx annual cost at 76kwh per day  =$4161 for the electirc per year ( we buy gas too!)
All of the above figures are from my last electric bill and the figures were provided by National Grid.

Think about this, I did not fire up the big rig last month either!!!



Vic, Thanks for the input.

I have looked at the Rolls Batteries and from the reading I have done I guess you get what you pay for in the battery world.   I will check out Colorado Electric,.

 Any pics of the remote setup you have.?

I have been researching for about a year now but I have no applied experience in these matters . That is why I posted here hoping to find a few that have some actual experience with these matters. I know Frank has been playing around with the solar heating for years.

I may just go with the grid tied system to start and slowly wean myself off the lines in time as products become less costly and more efficient.

 I really want that feeling of freedom by calling the utility and saying" Pull the meter", Yes that felt good just thinking about it.

[N9NEO]

Hi Gary,

I have taken the first step to getting off the grid myself.  I have 2m rig and some SWL rigs running off a few car batteries.  I figure if power goes out at least I got something.

I think the Wind is a really slick idea.  I spoke with some people up at Northern Power, a big windmill outfit up in VT,  last year and the consensus was the grid was still the cheepest way to go for the homesteader.  I think the crossover point is way closer than we thought though.  Obviously when electricity doubles in price alternatives do begin to look more attractive.

I design inverters in the range you are looking at on up to 50kw and even higher.  I can tell you that a 2-3kw inverter can be built for a lot less than you would pay.  A 10Khz pwm carrier rate would be reasonably easy to filter and would be about 95%-97% efficient, including the filter losses.  If you have to do a conversion from some other bus voltage than say 150v - 170v you will lose another 3%-5%.   Sorry I cannot give you schematics because we don't hand them out where I work.  I can answer your questions though.

Another way to go for homebrewer might be a square wave design.  The pwm design which produces a nice sine wave would need a small filter where a square wave design would need a bigger filter.  The problem with square waves is that there are some low order harmonics not far removed from 60Hz that will require one of those fancy class E type multipole pwm filters, and still probably wont work so good and output will look very trashy.  BUT you won't have any of the high order filters that produce hash type noise.   The pwm design would need a microprocessor and some code, while the square wave design would need a small digital ring counter or a basic stamp sort of microcontroller.  I expect the square wave design to be about as efficient as the pwm inverter.  Your losses are just moved from the silicon to the filter when you go to a square wave design.  A third way would be a low frequency carrier somewhere in the middle.  Every pulse you add will offer you the opportunity to remove one harmonic.  The type of inverter you choose should be based on what you minimally need for a output distortion number and also what is available for control. If the loads will take square waves then there ya go.  If you can program a micro or somebody hands you a control board then there ya go too.

73
Bob

 

[Warren]

I have decided to make this year my crossover year with the utilities. I am designing an alternative "Hybrid" system for my home.

The system I am looking towards will have solar, wind and a generator system combined to provide the charging power for storage batts. Eventually after testing and fine tuning the system I would liket o fully disconnect from the grid but for now I must get my feet wet if you will.

The power inverters are costly and I was wondering if anyone here has built any or would have designs and schematics for 3-5 kw units that cold be stacked with others? I am sure building them will reduce costs.

Any thoughts?

Gary,
  Will your inverter system be standalone parallel to the grid? If parallel with the grid you'll need safety (U.L.) approvals as well as approval by your local utility. Aside from the legal issues, you could be in big trouble with the Insurance Mafia should you have a fire (even if your homebrew inverter is not the cause!) You will also need a utility disonnect  in case the grid goes down (you don't want to be feeding power back into the grid while the utility repair guys are working on the wires!) For these reasons a homebrew inverter is pretty much ruled out unless you are going to have a separate standalone system.

  Residential wind power requires a 80-120' tower on average so we're not talking small stuff here.  The American Wind Energy Association is a great resource:
http://www.awea.org/faq/tutorial/wwt_smallwind.html

  Solar still costs (for the photovoltaic panels alone) $4-$5/ peak watt. Newer technologies and processes have brought down the manufacturing costs for photovoltaics somewhat but the manufacturers are not selling the end product any cheaper - they are pocketing the difference. The demand for PV panels is so high that there is no incentive to reduce selling costs. 80% of PV panels made in the U.S. are exported to Asia. The worldwide PV capacity has grown at about 25% per year for a number of years and shows no signs of slowing. Despite (or maybe because of) this prices are not dropping.

New York State has a incentive program that will provide a cash incentive of $4/watt, BUT only for systems that are connected to the grid and its payable only to an eligible installer (Not only can't you make the inverter, you can't install it!). See the NYSERDA web site for more details:
http://www.powernaturally.org/Programs/Solar/incentives.asp

Despite how bad your utility is treating you and how much you hate them etc., and despite recent sharp rises in electric rates the grid is still much much cheaper than generating your own power.
People put in there own power systems for one of two reasons:
1) They live too far off the grid
2) Personal satisfaction and independance.
They don't do it to save money!

All the same, I'd say give a standalone homebrew solar system a go, its an interesting hobby in its own right. I have a few very small panels (10W) that I charge batteries with and on the small panels the $/watt is really ridiculous ($120-$150 for a 10W panel!)

73 & GL Warren K2ORS/WD2XGJ

[K6IC]

Hi Gary,

I will send a few pix in a week or so ...nothing too impressive, pair of 5548 inverters stacked,  some panels, Outback charge controller and some Rolls batts.   The grid is abt 5 miles away,  by choice.

73  Have Fun,   Vic  K6IC

[K1JJ]

Interesting comments, Warren.

I know that you were in the very high-tech back up power business in the past, so you know the score.

About ten years ago I checked out putting up a windmill in great detail. I decided that the maintainance / breakdown cost, the batteries, the life of the parts, the initial investment etc,  did not make it cost effective.

I'm cornvinced that the best method would be to tap a strong brook or stream running by the house. If yu're lucky enuff to have one.  Hydro seems like a great method. Channel some of the water through pipes to increase its flow rate and you might have something. But then it may need batteries too, or use the grid as your backup as someone suggested here.

Oh, it would be nice if we all could use a palm sized nuclear reactor to generate steam, huh?

Good luck, G. It's a noble undertaking.

T

[Warren]

Interesting comments, Warren.

I know that you were in the very high-tech back up power business in the past, so you know the score.

About ten years ago I checked out putting up a windmill in great detail. I decided that the maintainance / breakdown cost, the batteries, the life of the parts, the initial investment etc,  did not make it cost effective.

I'm cornvinced that the best method would be to tap a strong brook or stream running by the house. If yu're lucky enuff to have one.  Hydro seems like a great method. Channel some of the water through pipes to increase its flow rate and you might have something. But then it may need batteries too, or use the grid as your backup as someone suggested here.

Tom,
    I still do some consulting work for the Dept. of Energy so I keep a hand in it. You hit the nail on the head, batteries are a big expense/maintainece headache and need to be periodically replaced. You have to control the charging and worry about the batteries venting explosive gasses.
 Also right on target about small hydro (called low-head hydro in the business) it could be cost competitive if you have access to a stream and there are no environmental/wetlands problems with puttting in a turbine.
  I should have mentioned net metering. Under the PURPA act (Public Utility Regulatory Policies Act of 1978) Utilities are required to buy back any excess power you generate at the market rate (this assumes grid-connected). So if you generate more than you use you can make a few cents/kHW - keep in mind they only pay you the 'generation' charges, not all the other things they bill you for such as the wires (transmission & distribution charges), taxes etc. You have to go through the hurdles of using a commercially built and installed system that is approved by the utility before you are eligible for net metering under PURPA though. As an investment it sucks but you get the satisfaction of selling electricity back to the utility.

73 & GL
Warren K2ORS/WD2XGJ

[WA1GFZ]

but Warren who will know if you are driving the meter in the reverse direction?
I checked into solar and figured 15 to 20 years if nothing broke. Ct. will pay instillation costs if you go for it but the prices are way past stupid. One place I called wanted $75 to come by and give me a quote.
I buried PVC under the basement floor in the new qth so I can put panels out to heat the slab.
My buddy in Palmdale has a 50 foot free standing tower serious strappage to hold up his unit. He blew a bearing and everything stopped. he needed to rent a crane to drop the unit. I've always wanted to put a water wheel in the stream behind the house. I found the law says you can't mess with water flow so good luck doing that.
I think the biggest bang for the buck is insulation and window performance.
Second is passive solar.
both require no repairs and just keep paying for themselves if you do it right.

[N9NEO]

Yes, I prefer low tek myself.  Sweaters and blankets are good.  I wonder what would happen if you put a big ass water tank like 50k gallons underground.  Heat it up in summer with heat pump and use it to then heat house in winter.

Line interactive UPS are big pain in ass.

73
Bob