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Author Topic: Power inverters  (Read 25497 times)
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K1JJ
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« Reply #25 on: March 01, 2006, 06:12:34 PM »

How about this idea?

Get an old steam, coal fired boiler. A big MO FO. Use the steam to turn a turbine electric generator for power. Take the steam that comes outa the turbine and pipe it thru the house radiators for heat.[or whatever radiators will handle steam] Also use the hot steam to heat the hot water in the house.

In addition, place the boiler where it best can be used to provide radiant heat, like a standard stove to heat the house. Maybe even an air ducting blower system to circulate the heat around the house from the stove.

Downside: Get out the coal shovel and load that boiler, mate!  [They DO have auto coal loaders]

T
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Warren
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« Reply #26 on: March 01, 2006, 11:11:12 PM »

but Warren who will know if you are driving the meter in the reverse direction?

Frank,
     If you drive the meter backward then you will owe that much less at the end of the month! If you generate on average more than you use the utility will send you a check (minus the wiring costs etc that they collect because they own the transmission and distribution system). 

You could design a strategy where you had say a PV system sized such that it produced as many kilowatt hours a month as you normally consume from the utility. During the day you make a lot more electricity than you need so you sell it back to the utility. At night, you buy electricity from the utility rather than run off batteries. If you balance it right you don't need batteries, and only pay the utility for the use of their wires.

73 Warren K2ORS/WD2XGJ

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K1JJ
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« Reply #27 on: March 01, 2006, 11:23:25 PM »

Warren,

How does it work?   Does your voltage sensor increase your voltage to slightly higher than the utility, then pass current through their system?  Does your own system limit the current and voltage level at the same time?

It seems that the 60 cycle phase has to be exact too?  No wonder they don't want some hack with a makeshift generator pumping power back down the line...  Grin

T
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« Reply #28 on: March 02, 2006, 07:17:02 AM »

Tom,

Wonder how many btu's of heat you'd get if that doo of yours caught on fire? Cool
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« Reply #29 on: March 02, 2006, 08:37:05 AM »

I would prefer to use the grid as my battery than a bunch of crap in the basement..
the power co uses more juice during the day so they love it. Tom just look at the grid like a big AC battery. Same deal you can drive it or load it. Yes your power factor must track the grid or juice flows the wrong way.  Look at all the generating stations they all must be in sync to drive the big short circuit load called the grid.
The blackout a couple summers ago was due to phase shift.
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N9NEO
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« Reply #30 on: March 03, 2006, 10:48:56 PM »

TALKING OF POWER GRIDS

There is a real component and a reactive component of current when connected to a grid and trying to put power into it.  By varying the magnitude you can control the reactive portion and by varying the phase you can control the real part.  or vercy vicy.  Anyway, this is pretty much the same if you have a large synchronous generator or the equivalent static inverter.  The same rules apply.

Motor drive inverters get burned in usually by what is called a back to back motor system.  Drive runs a motor which is shaft coupled to another motor which is hard wired back to the power line and acts like an alternator.  These are induction motors so that there is slip and the drive is run slightly above 60Hz like 62 or 63 Hertz.  It is not a big deal if the drive is off by a fraction of a hertz or so.  If both motors about 90% efficient then then you got about an 80% efficient system and also a couple % losses in drive.

If you are a reasonably adept control guy you can design a system where you take  the output of the drive and stick it through three inductors and then back onto the power line.  This then is how you would burn in the inverter.  This system is much less forgiving than the two motors in that the frequency AND phase of the system has to be under strict control.  You can't get lost and slip a pole or the system will shut down.  It has to be locked in.  Fortunately with many very large synchronous generators on the grid there is a large amount of mechanical inertia on the grid. The grid will not rapidly change frequency so it is an easy job to lock on to it.   This is actually how a line interactive UPS system works.  The inverter is normally phased so that it is actually supplying the power to your loads.  In the event of a power outage there is not even a flicker of the lights.  If you got a piece of gear on the line that shorts out then the inverter will phase back and try to get the power grid to clear the fault for you.  If the grid goes down you have to pay attention to what is called islanding.  You can have little islands of charged portions of the grid that can present a danger to others who may not know what is hot and what isn't.  I'm not really clear on how only your loads are running off of your ups and your neighbors aren't.
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« Reply #31 on: March 04, 2006, 07:32:26 PM »

Oh about +-15yrs ago,
          I visited Frank GFZ in January. If you remember that day Frank, it was one
of the coldest {{brr}} mo-fo days.  I froze on the way down, couldn't get warm
in my old truck.

          I came in to your passive solar room, I think it was 80 and planted myself
in the chair looking out at a fairly low sun and felt warm for the first time in hours!
It made an impression, loved your system.

          Inverters, they make some pretty cheap 1-3kw inverters,, statpower,
others. but they are not made to push power back to the utiliy co. nor should
they be connected in anyway.

          You probably won't be able to produce enuff juice to sell it anyway. btw, here in tucson, they will only pay back .02/kwr!! to home generated juice. however heating energy is a breeze here in tucson. I think I pay $100-200 tops for the year and the house isn't energy efficient.

          If I had a windmill back east, winters, I'd just wire it to heaters direct
and let it just dump btu's into the house. probably the best energy ease place
to live, might be amarillo tx in the pan handle. no real cold, windy all the time.
And you can have the best darn steak in the world there, hmm still thinking of
the ribeye I had on the way out here!

deano
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« Reply #32 on: March 04, 2006, 07:46:19 PM »

Hi Dean,
Yup, you are one of my few friends who showed at the perfect day to check out the system. Snow on the ground helps reflect even more energy in the house.
Today it was 80 in here all day long. I was happy to hang out in the shack and cool off. It's about 70 now and we are all wearing sweaters.... but the heat has not been on since about 9:30 this morning.
New place will store heat under the basement floor.   
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Warren
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« Reply #33 on: March 05, 2006, 05:48:32 PM »

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.
 Shocked

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


Gary,
    I just looked at your numbers and you are not close to break even for a solar photovoltaic system. At todays prices and given your location a grid connected solar system with battery back up would run you approx. 83 cents per kwh. Check out the solarbuzz web site:
http://www.solarbuzz.com/SolarIndices.htm

   But if we did things only on a dollars and cents basis then we wouldn't bother with ham radio either! (What's the payback on a ham rig  of any description vs. unlimited long distance telephone service using Skype or Vonage?)

73 Warren K2ORS/WD2XGJ
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Warren
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« Reply #34 on: March 05, 2006, 06:24:28 PM »

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

Gary,
     If you use 76 kwh/day and in Syracuse you have an average of 4hrs per day sun year round then your PV system would need to be 76/4 = 19 kW! At $4/Watt (the low end of the price scale) the cost of the PV panels alone  would be $76,000. In winter Syracuse gets an average of 2.5hrs of sunshine so if you sized the system based on that you would need 76kwh/2.5h = 30.4 kW of solar panels at a cost of $121,600. again for just the panels. Keep in mind that each kW of panels will occupy approx 90 = 100 sq. ft of area so you will need 1900 -3000 sq ft - that's big!

Average sunshine maps:
http://www.members.cox.net/weller43/sunshine.htm

73 Warren K2ORS/WD2XGJ

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« Reply #35 on: March 05, 2006, 07:21:12 PM »

That is why I'm into super insulation. Solar pv just isn't worth the trouble and we won't live long enough to break even.
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Warren
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« Reply #36 on: March 05, 2006, 07:59:42 PM »

That is why I'm into super insulation. Solar pv just isn't worth the trouble and we won't live long enough to break even.
Frank,
        Solar PV pays when you live miles off the grid and the cost of running a power line is several $100K.
Conservation can be cost effective, look for sales and rebates on the compact flourescent bulbs to replace the very inefficient incandescent lights. L.E.D. lighting will someday become cost effective and is even more efficient than the compact flourescents.
        I have 2 solar PV panels, 10watts each, one I bought at a hamfest for $50, the other was an engineering sample given to me.  I use one of the 10W flexible panels and a charge controller to charge a 12V 26AH gel cell which powers my Icom706 in the mobile (the mobile is not tied to the car alternator or battery in any way). I did it to get isolation from the noise in the car's electrical system. Turns out most of the noise comes in from the antenna, not through the dc power from the car.
73 Warren K2ORS/WD2XGJ
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K1JJ
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« Reply #37 on: March 05, 2006, 08:54:43 PM »

[Frank,  Solar PV pays when you live miles off the grid and the cost of running a power line is several $100K.

Or, You COULD do like the Tron. Back in the 70's he used a pole pig to tap directly off the high voltage lines running by his property in a field. FREE power while it lasted.   7KV to 240 AC output. It worked FB until one day the wind blew down his 2X4 frame holding the taps and started a fire. Just a minor brush fire with fire trucks - and a slap on the wrist from the power co...    Cool

T
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« Reply #38 on: March 06, 2006, 05:57:05 AM »

Something doesn't seem right here. Gary says he averages 76 kwh per day. Last month, Feb, the average daily temp was 32 deg F (in Denver probably 10-15 degrees colder at my QTH) and I used 463 kwh for the entire month. The cost was $45.23. In the winter it's around 450 kwh for the month and in the summer around 300 kwh per month.

I bought 166 CCF of natural gas for the furnace, stove, waterheater, and dryer. Brought my total bill to $191 for Feburary. Bills are in the $70-80 range in the summer.
This is for a 2400 sq ft house, R-25 walls R-45 ceiling, with no fires started last month in the wood stove.

Gary, if you're heating the house with electric that's the first thing to fix.

73, Marty WB2RJR




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« Reply #39 on: March 06, 2006, 08:39:20 AM »

Wow some great comments.

First and foremost , Tom I see you finally got your hair under control!.

Warren . Yes the figures you presented are correct. That is what drove me in the direction of passive solar hearting like Frank has been working with and wind power. My location up here on the hill has an averge annual winds  of 11 miles an hour. I don't know what direction I will eventually end up with but PV is certainly a last option and frankly would be used in a supporting role not a primary role.

In the winter we have little sun but a lot of wind. In the summer we have little wind but a lot of sun. So my thoughts were a hybrid sytem to supplement each other.

I see the system as I continue my research in the same light as much of the info offered here. To depend on any one sytem would be completelty out of line $/kw and the grid is the best bet.

My approach would be a experimental approach starting small and then adding on over time slowly reducing energy costs as I learn the applied side of this. If I think of the amount of money I have spent on this hobby over the last 18 years I can easily justify some cash for this cause Huh.

Marty - yes, that is my daily annual average consumption as listed above. I copied the info off of my bill from National Grid. We have three children, The dryer runs at least 4 times a day along with the washer. Two dishwasher loads a day. 5 Computers and monitor screens, 4 TV sets, not to mention the lights and support systems for the home. Take that and add the Ham gear into the equation and you have it. When I was more active a few years ago , in the winter months, which is when I operate the most, the electric bill would go up abot $80.00 per month until spring.  Big rigs use big power Wink.

Then of course I am spending almost as much to deliver the power to my home as the power I use.  What I find interesting is if I compare last years consumption to this years consumption I have reduced my combinde gas and electric useage by 20 % and my bill almost doubled!! The gas side is really looking good but I am losing on the electric.

This project should be fun. I apprecaite the input here and updates on the progress will be submitted as we move forward.   
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« Reply #40 on: March 06, 2006, 08:56:25 AM »

Gary your electric rates are dirt cheap compared to us poor slobs. power co. got 2 big increases the past two years. Tom Vu will have to go My ugly class E if they go much higher.
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Warren
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« Reply #41 on: March 06, 2006, 01:24:48 PM »

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



Gary,
      I strongly recommend that you collect wind speed data before investing in a wind power system. You need an average speed of 8mph. Buy one of the weather stations that has a computer interface so that you can store the data. You do need a substantial tower - remember that unlike an antenna, a wind turbine is designed to catch the maximum amount of wind - torques will be considerable. It needs to be >80' high depending on local topography and obstructions it may need to be substantially higher.
    As I pointed out with solar, you won't be eligible for any rebates unless you are grid tied and that means a commercial inverter that is approved by your utility and installed by pros that are certified or otherwise  recognized by the utility. The utility may ask you to carry insurance in addition.  The AWEA web site has a great how-to slide show on residential wind:
http://www.awea.org/pubs/documents/swslides/toc.htm

   A solar hot water or geothermal system would probably save you money - if you are using 76kwh in a day then you must be using electric heat. Solar hot water heat  is basically just plumbing so no high tech or utility approval is required. Just dumping the electric heat should bring your electric usage down from 76kwh/day to a couple of kwh/day. At that point it really would not make financial sense to generate your own electricity.

  73 Warren K2ORS/WD2XGJ
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WA1GFZ
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« Reply #42 on: March 06, 2006, 02:02:15 PM »

Warren,
You are not kidding on the tower. My buddy in Ca has a free standing 50 footer that has 4 legs. It would easily handle an 80 meter beam. The concrete block at the bottom was about 6 feet on a side.
 The generator that set up top was about 3 feet long and almost 2 feet in diameter. It took a crane to drop it.
I figure 300 lbs easy without th eblades. The blades are 8 feet long 3 if I remember.
Serious force.
Not something that can go on your roof.
Water or passive the cheapest but then you need sun.
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Vinnie/N2TAI
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« Reply #43 on: March 06, 2006, 07:05:05 PM »

Gary
One of the neighbors up at our camp on Mexico Point, Lake Ontario, has a wind turbine. Yes the tower is a real substantial three legged tapering tower. The three bladed prop is real loud when it is running kinda a whump/whump sound. Don't know the owner so I don't kiow hat it is hooked to. There is a marine radio antenna on the tower so maybe it runs that Hi Hi.
Vinnie
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WA1GFZ
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« Reply #44 on: March 07, 2006, 09:47:39 AM »

the biggest one I ever saw was on top of Mt Tom in Ma.
You could hear it a 1/4 mile away if the wind was right.
Blades are quite long. I don't think it is running any more.
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N9NEO
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« Reply #45 on: March 07, 2006, 09:33:21 PM »

I had a discussion with guy from Fairchild last week and he told me he thought that windmill prop tips could end up going supersonic if thing spins fast enough.  I don't know if that is bad or not.  I don't know if blades have a lifetime or not or any other ongoing maintainence that has to be done.

I recently had some conversations with some people who do very large windmill system designs and installs.  An interesting point was brought up that the actual speed of the windmill can vary all over the place.  The inverter  between the generator and the power line does the actual frequency conversion.  So if generator is putting out 20Hz so that inverter has to spin at 40Hz to get the power to mate up to the 60Hz line power.
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K1JJ
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« Reply #46 on: March 07, 2006, 10:08:12 PM »

Remember the sound of that big wheel spinning in the movie, "Contact"?  Wheeeeeeew - Wheeeeeew - wheeeeeeew - then it became unglued and went to pieces.

Now THAT was a big MO FO.

I have to agree. After doing my own research into large bladed windmills, maintainence and potential crap outs, it makes a pair of stacked full sized 75M rotary Yagis look like a cakewalk.

T
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« Reply #47 on: March 07, 2006, 10:30:17 PM »

Bob,
My Buddy in Ca. had SCRs doing  the frequency conversion. I don't remember any big caps as if it was starting with LF AC to DC. There was nothing mechanical on the ground and there was nothing but mechinacal on the tower.  It locked up on him and the last time I saw it was on his garage floor. A  bearing seized up and hacked the drive shaft a bit so it needed to be welded up and turned true.
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« Reply #48 on: March 09, 2006, 11:27:24 PM »

Instead of completely disconnecting from the grid can;t you work out some sort of arragnement where you sell power back to them and it appears as discounted from the bill ? This way you're connected to the grid and it's there if you need it but you're usility bills stay verylow since you're making most of the power yourself.
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« Reply #49 on: March 10, 2006, 08:15:12 AM »

You could build a gas producer system and run a standard internal combustion powered generator.  You feed the gas producer any flamable solid. (wood chips, ground leaves,  brush, or wood pellets, coal, dry trash), usng an automated auger system. The gas producer makes a lot of heat as a by-product, which could be used for heating you house or making hot water.   If you are faily handy the system wouldn't be to expensive. Basically you'd need to weld up some stainless steel and do some plumbing.  The issue is fuel storage since it's bulk, I think you would need a shed or barn for enough storage. The plus is that you can "harvest" your fuel at a very low monetary cost. The down side is that most of the free fuels will need to be ground/chopped/chipped for ease of use. 
Every fall I think about this as I rake up a huge amount of leaves and brush and such.... 
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