Inverter information needed

[xtal_01]

I think what I need is an electronics genius.

So ... I just purchased a lot ( in fact going to get my building permit today) that has a river and dam on it.  It is a small historic town in VT and at one time had 7 dams powering mills in it.  The mill on my property was washed away 100 years ago but the dam remains.

I would love to put all this falling water to good use.

The turbine is not my real problem.  My problem is the electronics.

I have in the past used an inverter in my RV to get reliable 120 VAC and to run a 3 phase motor at home I used a surplus variable frequency drive ( fed 240 VAC single phase in, de-rated the unit and got 208 three phase out) but this is different.

First, it needs to generate 120 and 240 VAC ( the only way I see around this is to use a large and expensive transformer with a center tap to derive 120 from 240 in).

Second I need it to sync with the AC line when it is available and to keep running when not ( I found one small inverter that actually shut off when it lost the line sync).

And it needs to be economical.  We had UPS back-up units where I use to work but they ran in the 10's of thousands of dollars.

It would be great to get two say 1500 watt inverters ( or even 3000 watts), find a way of linking them together to get 120/240 (meaning the sync would need to come from one source) and then also allow it use the line sync when available.

I know I am asking a lot but surely it must be doable.

Trying to regulate the speed of an water turbine and then syncing it to line is just not a reasonable option.

I could just isolate myself from the grid but I may not always have enough power to supply the house and isolating individual circuits would be tough.

Any suggestions?

Here is a link to the house web site:  http://mikeandmariasnewhouse.shutterfly.com

Thanks .... Mike

[XeonPony]

normal pure sine wave inverter, let it be the synch source for the turbine!, Use an iron core regulated induction motor as the generator! It will synch its self to the Inverter.

Make sure it is a very well built inverter, and make sure you have an automated turbine disconect system and shut down system.

[dnix71]

Pure sine wave inverters are not reliable to sync to. I've owned a couple and they were close to 60 but not quite. If you want to backfeed the grid you must (legally) use whatever your utility or co-op says is okay.

All legal, safe grid-tie inverters shut down when they lose the grid. That's the law and the only safe practice.

The proper setup is to connect your mill to a grid-tie inverter that can handle the max load from the turbine and have a battery backup feeding the inverter when the grid goes down.

http://www.firemountainsolar.com/inverters/grid-tie-inverter/outback-gtfx-grid-tie-battery-back-up-power-inverter-sealed/

The GTFX series is not cheap, but it is exactly what you are asking for. It won't charge your batteries from the grid unless necessary and will auto-switch to back up power if the grid fails. It also allows you to sell back to the utility legally and safely.

[xtal_01]

You are right ... not cheap but exactly what I need.

I realized there must be some regulations or anyone could through power back into the grid ... and damage something.

Might be well worth the money if I can get a reliable turbine up and running.

I grew up near Niagara Falls.  I have toured countless power plants including the Rankine hydro plant that operated for 100 years!

I just keep looking at this falls and thinking it would be awesome to have my own hydro plant.

Thanks .... Mike

[bob g]

seems to me perhaps you have the cart before the horse

might be best to do a site analysis and determine what the average power that is available at the dam, then determine if that average power is more than what your average loads are likely to be.

if the site average load  is equal to or greater  than sites average power
production, perhaps it would not make sense to put out the added expense to sell back to the grid? 

one would also have to determine the buy back rates from the utility, and from that extrapolate the revenues likely over time,

it might be even if there is an excess of power generated that could be sold back, the payback might be excessively long.

me?  i would start with getting a turbine setup and get some actual power production numbers first!

well maybe second, probably first would be talking to the utility to find answers to things like what is acceptable to them, what they expect from you, what equipment is acceptable to them, what the buy back rates will be, how long a contract can you get at what rate per kw/hr. etc.

then develop the resource and see if it make sense financially to connect to the grid to sell back.

you may also need to check with state and federal authorities as it relates to recommissioning the dam for power production. there might well be significant financial hurdles to address with any number of such entities.

i would also check the 50 and 100 year flood charts for that river, to see how likely it is that you would have a total loss of a turbine if something like a cyclical flood comes through.  would be horrible to invest a bunch of time and money just in time for a 50 year flood to come through and take it all away.

might also want to check with your homeowners insurance agent as well, a mill can be seen as an "attractive nuisance" which leave you liable should some kids get caught up in it.

if you are far enough off the beaten path, and can accept a certain level of exposure, perhaps you don't concern yourself with these things?

only you can answer that

lots to think about

bob g

[xtal_01]

I appreciate all your advice.  Some of these things I have checked into.

I did check and from some quick calculations I think I can generate about 8 - 10 KW.  This is a fairly large dam.  It has a head of about 8 ft.  A 24" pipe still runs under the neighbors house that use to be an old mill.

I "suggested" to the town and utility that I would like to generate my own power.  They both said taht if the dam did not exist there would be no way but since it is already there they saw no reason why I couldn't.  Vermont is one of the most energy conscious states there is.  We love being "green".

It is most   definitely in a flood plane, I could not get flood insurance on it if I tried.  I earnest though, since I plan on making most of the parts (I have a lathe, mill, mig/tig welder,....), and it will be anchored in rock ( this entire property is on rock ledge with no more than 24" of dirt on it), I think it would be rough to have a "total loss".  To keep things looking "clean" and not attract too much attention, I am thinking of a sealed unit at ground level.  both the penstock and spillway will be for the most part under ground.  Even with a complete flood, the only real loss might be the bearings and actual generator (If I can't keep it either sealed or under some type of positive pressure).

I am really not planning to make any money selling power back .... I don't care if I ever do.  I am more concerned on how I can supplement my power.  I just can't see trying to isolate a few circuits and them switching them on and off the grid if I have or don't have my turbine running.  It would be nice if this was all automatic.  If I have power then I will supplement or even totally supply my own power.  I the utility goes out, I have my turbine up ( and maybe some storage batteries).  If my turbine is down then I am on the grid.

I do tend to over build all my projects.  I do agree, the inverter will be the last part of the project ... I just like to plan everything out before I start.

Just FYI .... here is a project I did a couple of years ago.  My wife is paralyzed (broke her neck in a diving accident when she was 12, she is 33 now) and needs medical care ever 4 hours, thus she had never traveled.  I was living in SC and built this RV project just before moving down (got it done and drove it down the week of the wedding).  I have never even been in a motor home never mind cutting a hole in one, designing and building a lift that folds under it, gutting the interior, installing hospital beds and then designing and building a second lift inside.

Here is the link:  http://mcsele.shutterfly.com/2299

We have a saying in our family ... the improbable we do right away, the impossible just takes us a little longer

I do truly appreciate all your advice!  I am always afraid there is something I have missed.  I usually think projects through several times from start to finish before starting on them.

Thanks again so very much !!!!!!!!!

Mike

[bob g]

Mike
it is folks like you that make groups like this such a great place!

now that i have a better understanding of your needs, and capabilities
here is some more unsolicited advice to use as you like, or disregard if you like.

i would go with the turbine build, and drive an alternator to do dc charging of a battery bank, the bank need not be large, just needs to be a buffer.

i would go with a 48volt system, and i would use the 110-555jho leece neville/prestolite alternator with a standard regulator with a sense wire.
(if you want to know more about this scheme contact me by pm)

actually if you have enough capacity, i would drive two of the aforementioned alternators,  which would get you very close to your 10kw goal.

figure on driving them at ~6500rpm and gear accordingly.

then it is a simple matter of an inverter system large enough to do the job. i would strongly suggest looking for a surplus exeltech mx series system.  the mx is not grid tie, nor would i want it to be.  these inverter systems come up with some regularity on ebay and are usually one hell of a buy in my opinion.  exeltech will repair any of their products for a flat fee of 100 bucks provided it is repairable and not a molten puddle after a lightening strike or fire.

the exeltech can take a very wide range  of input dc voltage, much wider than most other consumer grade inverters. they are the cleanest sinewave inverters made too, which might be of concern to you with your wifes health issues.

if you can get that far, then you will have a very robust system, capable of up to 10kw output (if you can get that much from the water source and your turbine of course) and also have approx a 22 kw surge capability for starting heavy loads.

then you get to where you have to switch loads, or divide loads between your resource and that of the utility.  that in my opinion is a much easier proposition. if you put the batteries, inverters, and all switchgear, and control systems within a separate building (powershed) that is not habitated by man or beast you have no concerns with the NEC, just build all into a metal container and lock it up. feed the utility to the power shed and also feed the hydro to the power shed, and then take the resulting power from the shed to the house.

sounds like a really fun project

btw, there will be those that will suggest an aircore pm alternator, i would recommend against such because of issues relating to the ease of regulation and control of the power coming off the the pm generator.
the use of the 555alternator at 48volts nominal will return a respectable efficiency of around 80% with a field draw of less than 1% of generated capacity (approx 7amps total field excitation at 10volts for both alternators, ~3.5amps each)

the 555 alternator is pound for pound, amp for amp, the best bang for the buck on the market today, this allows one to keep a spare on the shelf should something happen and you need it, without breaking the bank.

with careful shopping and not including the hydro turbine, i think one could source all the parts to do this system for less money than one gridtie inverter in the 10kw class.

fwiw
bob g

[xtal_01]

It is funny, at one time I felt somewhat isolated.  When I tell people my thoughts, they just shake their heads.  I am a true DIY guy.  The saying goes"If Mike throws it out then you know it is garbage".

I am so glad I found this forum!  I knew I could not be the only one who wanted their own hydro station.

I completely agree with your assessment.  I have a workshop which is closer to the road than the house.  I am bringing 400 amps into there first and then taking 200 to the house.

Because of my wife's condition, we truly need reliable power.  Where the lot is, I was told you can loose power for up to 5 days during a winter storm.

In the short term, I am putting a small generator ( I will run in on natural gas ... I have a line on site), leaving it in the workshop along with a transfer switch (I may "cheat" and back feed a breaker ... just need to remember to shut off the main breaker first), a few deep cycle batteries and an inverter.  They will be clear of the house and yet "safe" in the workshop.

The RV had no inverter in it when I got it.  I wired in a 1500W unit and we love it!  Running the generator all night is a pain (not to mention making hard to sleep as the beds are right over it).  Two very large batteries running a few small 120 vac items and the 12 volt furnace get us though the night.

Not having to start the generator every time we stop and need 120 vac is great.

That alternator looks great 160 amps at 12 volts.  I don't know what they usually cost but ebay has them for $165

Thanks again so very much !!!!!!!!!!

Mike

[XeonPony]

I missed the grid feed back thing.  I tend to keep every thing isolated and easily discernable b y having only one link being the transfer switch.

As for using the sine wave inverter it is just some thing for the induction motore to synch to once going it will force a pretty good sine wave onto the line.

Given his resource a Kaplan or Francise would be ideal, using a large pump head in revers works quite well with a PLC to maintain frequency.

Remember a good big fly wheel is importent for stability if generating pure AC, if you go that route any ways!

[bob g]

another option for the generation side of things
would be the use of an ST generator head
perhaps an ST12 or ST15
they need to turn 1800rpm for 60hz and rated power, however
a guy could take either apart, and separate the 4 stator pole coils
and bring each and rectify them.
each coil produces 60vac which is more than adequate after rectification for a 48vdc battery bank/inverter system.

the upside is the slower rpm needed to get the required power, 1800 rpm is much easier to gear up a hydro to than 6500rpm i would think.

because you would be rectifying there would be no need for precise speed control either, all you would need is a purpose built regulator to control the field current. also because there is no need for a large battery bank and need to recharge the bank from deep discharges and simple single step regulator would be sufficient, just set it for float voltage and you would be good to go.

one of the ST heads with first world brg's would likely run for a very long time, requiring only brush replacement from time to time. 

Tom Osborne from Georgia Generator has the ST heads, replacement brushes and replacement slip ring sets for his products. if  you go this route be sure to order replacement brushes and sliprings.

now because the st head is single phase the ripple content is going to be significant, so  you either will have to filter the crap out of it , or
order an STC head which is 3 phase and as such will have a much lower ripple.

just another option for what it is worth.

down the road if you figure a way to closely regulate the speed of your hydro, you could then reconnect the stator poles and get 120/240 single phase or 120/208 three phase AC at 60hz from the same generator. 

something to consider

bob g

[keithturtle]

I did check and from some quick calculations I think I can generate about 8 - 10 KW.  This is a fairly large dam.  It has a head of about 8 ft.  A 24" pipe still runs under the neighbors house that use to be an old mill.

With that much capacity and the old mill using a 24" penstock, sounds like a Kaplan wheel would give you all you need, and an average American reaction wheel would give you plenty of excess.  Too bad that penstock ain't on your side of the stream, would save a lot of work

Reaction wheel left, Kaplan on right in pic

Turtle