Turbine to Grid Equipment

[mcorner]

I am trying to figure out what I need to grid-tie a hydro system I am planning.  I want to avoid inverters and batteries as they just add $$ and inefficiency.  The grid-tie qualifies me for a $4/watt incentive for construction from the state (MA).  (Forget about the FERC for now, I have already been speaking with them and will bring that up in a separate message)

A little background: ~45 feet of head, about 300GPM, 900ft of 6" penstock.  I am looking to net somewhere near 1kW.  The system will be in Western Massachusetts.  The flow will seasonally vary, but I should get 300GPM most of the time (80%?).  The rest of the time I will have to cut to 150GPM or turn it off.

The best option seems to be a Trugo attached to a three phase induction motor (such as a Baldor).  After this, I am a bit lost.

I think I need a transfer or disconnect box for the utility regulations, and a dump load for when the power is out and I am not drawing enough from the house.  I plan on hiring an electrician (duh), but given the custom nature, I need to be able to spec it out myself and tell him or her what to do.

Does anyone have a working system with a similar configuration?   I need something past armchair speculation, I am looking for part numbers and diagrams  I would rather buy parts than build, as I want this to actually work.

Many thanks!

-Mark

[electronbaby]

First off, I dont know much about hydro. There are others here that do. I just wanted to point out that  installing an inverter would widen your generator voltage capability. This would mean that you could still have a working system even when the flow rate dropped to 150GPM from the normal 300GPM without you doing anything. It would not involve batteries, BUT you would have to generate DC with a PMG and have some rectifiers and possibly a cap filter bank to feed the inverter. This is not the only way to go and you certainly could do it with an inducton generator also. You would then have the problem of maintaining the generator speed when the flow rate dropped.

You will most likely need a cogen disconnect.

The inverter would disconnect normally when the grid failed. It then could run open circuit granted you didnt exceed the max VOC accepted by the specific inverter you used. (for instance 550vdc) This would allow the voltage to be kept high and give you less line loss than if you were to wire the whole system for 240vac single phase tie in.

Just my two cents.

[mcorner]

Interesting, I have no problem at all going to a DC-based system over an AC one.  I was just going down the three-phase induction path as that is what most of the information I have found centers on.

As I understand it the inverters are very efficient and would output nice clean AC power.  That may make it simpler and I could use an off-the shelf grid tie inverter.  But looking at something like the windboy, it cuts on at a rather high voltage.  I need something like that that does dump load control as well.

Does anyone have a design for the alternator, inverter, capacitor ban, and dump load?  It is tricky to match all of the voltage and flow constraints up.

-Mark

 

[electronbaby]

why do you need a dump load?... maybe Im missing something. Im sure it can be done without one.

[mcorner]

As I understand things, if you lose power to the house and the house isn't drawing enough power from the system, then the generator will burn out.  I believe this is true for both wind and hydro, but not PV.

The more I look at this, there may be a good possibility:

Connect a 48V alternator to a charge controller (such as the Morningstar TriStar TS-60) which can handle dump loads.  Then connect that to a grid-tie inverter (such as the Outback GTFX3048).

If the power goes out, the Outback will disconnect the charge controller, which will dump power into the dump load  (dehumidifier or heater perhaps).

All for about $2000.  Seems reasonable?  I would just need to select an alternator that output a reasonable 48V.   However, during low-flow conditions if would output lots less voltage (may be 24V) and then I think the inverter would cut off.  The Outback can only use 42.0 to 68.0 VDC.  

Any alternator ideas?

[electronbaby]

oh ok, so you want a battery based inverter. The outback inverters are battery based, and will not work without a battery. You can use a PV grid tie inverter to do what you want. It does not need batteries. It should work fine as long as the DC on the input is clean. There is no need to use batteries, unless you want them. When you go down to 48vdc from 400vdc, you lose efficiency. It can be done either way.

When deciding on an alternator, you can of course use a 48v based alternator, OR you can use a much higher voltage. IF you pick an alternator that can run open circuit, there is no danger of burning out, the only problem would be that the voltage would go much higher than it would under load. This is important when using a low voltage such as 48vdc. It is UNIMPORTANT when using a much higher voltage. You just have to make sure the VOC of your alternator is below the max allowable voltage for the inverter input. Like I said before, a PV inverter input voltage range might be from 195vdc to about 550vdc.

Either way, you can have a workable design. I just interpreted your question as if you wanted to stay away from batteries.

[electronbaby]

and, no, I dont have any ideas about the alternator you should use. If it was me, I would build one. You might not want to do that however.

Again, (im sorry) I dont know a lot about hydro equipment. I just have a pretty good understanding regarding the physics behind this stuff.

[mcorner]

May be something has gotten lost, but I don't want to use a battery at all.  It is just that most equipment is centered around battery-based systems.

Ok, I will try and look for a high voltage alternator that can supply the cutoff voltage for the high voltage inverters, and doesn't produce more VOC than the MAX voltage for the inverter.  That sounds like a good plan (I hadn't considered high voltage DC yet). I should probably have some kind of safety device for limiting the voltage of the alternator to make sure I don't fry the inverter when something goes wrong.

[DamonHD]

Consider an SCR-based crowbar: I have a tiny one for my tiny turbine set.

http://www.earth.org.uk/wind-power-pilot-autumn-2007-MotorWind.html look in the 'Overvoltage' section and then you'd need to scale up rather a lot.  You might also want a couple of stages, the earlier one with a dump load, to apply the brakes more gently.

All fairly simple and cheap to protect expensive stuff downstream, IMHO.

Rgds

Damon

[dbcollen]

A crowbar would be fine for a permanent mag alternator, crowbarring an induction alterator will cause it to run unloaded, and you may see a very large voltage spike when the crowbar is disconnected, as the alternator will be running at aprox twice the loaded rpm.

Dustin

[mcorner]

Yeah, I am really trying to avoid anything too "home brew" for this reason.  The penstock and housing obviously will be custom, but the rest should be fairly stock.

I thought about this again, it seems like my original plan for a low (24/48V) alternator is probably a good one.  The parts are readily available etc.

As for the alternator, it looks like automotive alternators have voltage regulation built into them, so now matter how fast the alternator is turning, I should get constant voltage, right?

[chainsaw]

If you are interested in using an induction motor as a generator, there is good book titled-- Motors as Generators for Micro-Hydro Power by Nigel Smith.

This book is available from the Centre for Alternative Technology in Great Britain.

There is a lot of good information to be obtained from this book.

[zeusmorg]

 The first step you need to do is see what equipment is acceptable in your area for grid tie. All grid tie systems MUST have the ability to disconnect in cast the grid goes down for safety reasons. Most utilities are familiar with good grid tie inverters, so that is probably the way you should go. It may also be a good idea if you experience power outages to have at least a small battery backup system to provide you some basics during outages.

 As fas as a dump load grid tie doesn't require that. Usually a 3 phase motor conversion is the most efficient on hydro if it is properly sized. Alternators are generally a cheaper solution, though they will work.

 It seems that a lot of reading up is in your future, either that or get an expert to design the system.

 The nice thing about hydro is that it is a fairly constant and reliable source of RE power.

[mcorner]

I believe the grid tie needs to be listed as UL 1741

So, lets assume I go with no batteries (the power hardly ever fails around here).

Who sells an automatic transfer box I can use?  I think I still need the dump loads.  I think there is also a motor protection box.  Is anyone on the board doing this in practice?  (I have read that motors as generators book, and it is all fascinating theory, but I am looking for parts and designs!)

-Mark

[DamonHD]

Have a look at:

http://solarjohn.blogspot.com/

He uses an automatic transfer switch in a slightly different way (to suck excess from his PV and batteries), but he may have a band/supplier in there...

Rgds

Damon

[mcorner]

His is just a relay and would never pass an electrical inspection

I looked at the outback inverters again and they seem to have a dump load control in them as well (I haven't quite figured out the wiring yet), so for a DC system you don't even need the separate Tristar controller, the outback seems to do it all.  I will probably go with a DC system given the complexities of the AC system.

[Lowhead]

Where in MA are you?  I am in the process of installing a low head turbine on my dam in Hopkinton MA.  I looked into the $4/Watt incentives but since the state requires a certified installer it wasn't worth it.  I am going to be using the LH1000 from Energy Systems and Design.  It can be set up to run in voltages from 12 to 240V and with remote rectification.  I have all of my approvals from the Conservation Commission and am just waiting for delivery of the unit (10-12 weeks).

[mcorner]

Williamsburg, MA, right near Northampton.  (I teach at UMass)  I have just started this process so ignore my ignorance.

I saw your pages before, it looks great!  I asked them about the certified installer and they said I could build it myself, but I had to have a licensed electrician to do the final hookup (no problem).  But the grid-tie is required for the incentive and the grid-tie invokes FERC.  I am going to start down that path until I get really frustrated  I have talked to our own concom people yet, but I have talked to DEP and they said they would be willing to help educate the local concom.  They also seemed to think it was likely to be approvable.

I am definitely leaning towards a DC system after wading through lots of material.  I probably have more variable flow than you, so I have to figure out what to do with the variable DC output that will create.  I am thinking a high voltage DC system going into a DC-DC regulator to step it down to 24V.  Then put that into an outback inverter (connected to a dump load) and tie that to the grid.  I think I need at least one battery as well to make the outback work.  Are you running it without a battery?

BTW, our stream is going crazy right now from all the rain!

[electronbaby]

mcorner, I am familiar with the area your in. You said you teach at UMASS, you know anyone at the RERL?  Im on Mt. Tom often.

[truegrit]

I went to the EDS site and it showed no longer have this LH1000 product, did you receive yours?

[hydrosun]

There was a great article in Home Power magazine a few years ago decribing a system doing exactly what you are describing. They used a dc hydro from Esd and fed the output through a solar batteryless grid tie inverter. When the grid went down they had a trace C-40 to turn on a dump load. They had to add more capacitors to smooth out the voltage spikes to make the voltage steady enough not to falsely trigger the C-40. The inverter they used was a 1000 watt unit by a company that doesn't make them anymore. You'll have to find another inverter that will do the same thing. Do a search at Homepower.com for all the details.

 The other alternative is an induction motor as generator. Hook it up with a motor starting relay that you have to manually hold on as you start the water flowing. I've seen that setup in operation. It used a weighted water deflector held up by an electromagnet. The deflector was manually held up to start the turbine and then held in place by the electricity from the grid. If the grid went down the electromagnet released the deflector and the water was deflected from the pelton wheel and the turbine shut down. Someone had to manually restart it. So that system is simpler but the parts aren't as easy to just go out and buy. And I not sure about UL listing and further utility requirements. For that reason the dc route might be the easiest.

Chris

[Lowhead]

I just checked out the ES&D site and I still see the LH1000 there.  I haven't recieved mine yet.

[Lowhead]

I am interested in who you talked to regarding the certified installer thing.  I have talked to FERC and they were actually pretty nice.  He basically said "I can't tell you that most people with small hydro put up a token Solar or wind setup and then hook up the Hydro after getting the net metering hookup"  I have talked to our utility and if you don't use a UL1741 inverter you need to spend about 10K on all sorts of safety gear to protect the line workers etc.. so if you want to be grid tied, definitely go DC.  I will have a minimal battery bank.  It's not like solar or wind where you need bigger storage for when the wind isn't blowing or it's dark out.  Definitely you should read the Scott Davis book called Microhydro.  You can get it from Amazon or the www.altenergystore.com (right in Hudson MA).  There is a microhydro discussion group on yahoo that has some great info.  Lucky for me Homepower magazine just did a hydro article featuring the LH1000.  

[ghurd]

"I have talked to FERC and they were actually pretty nice", etc, is why I always say "play nice" with them.

G-

[mcorner]

The FERC guy did not say that to me, but the incentive from MassTech is much more valuable to me than the grid-tie selling of power.  As I said, you need the grid-tie to get the incentive...

I am pretty settled on the DC system now, and I am working on getting the design details worked out.  I am currently working on the generator selection to match it to the battery bank and getting quotes on 1000 feet of 6" HDPE...  

Below you can find my conversation with Tyler Leeds (leeds@masstech.org).  I believe I called both of those installers and both basically said, we don't do hydro, or "hydro is hard".

On Mar 7, 2008, at 4:52 PM, Tyler Leeds wrote:

Mark

Great questions. In response:

(1)     You can pursue the project yourself, as long as you meet our insurance requirements, outlined in the solicitation on the SRI website, and have a licensed electrician on the team.

(2)     I only know of a couple of small hydro installers here in MA, Pioneer Valley Photovoltaics (http://www.pvsquared.coop/) and Precision Designs, LLC. (Chris Vreeland, PE, 413-269-4965, vreeland67@msn.com)

(3)     It sounds like you're on the right track. You may want to talk with a consultant to get a better sense of the requirements, as I'm not sure exactly all of the people you'll have to talk with about the project.

I hope that helps, but certainly if you have additional questions, please let me know. Thanks.

Tyler Leeds

-

I am interested in possibly applying for an SRI grant, but I have a

few questions.  I have a  site suitable for a microhydro installation

in the neighborhood of 2kW.  I have read through the pages, but they

are generally oriented towards solar and wind (this is totally

understandable).  I have already done a good bit of homework on how to

build the system itself, but I have a few questions that relate to the

SRI.  Unfortunately, the permitting and installation process is a

great deal more complicated in the case of hydro.

1) Are you required to use an installer to get an SRI, or can you

install the system yourself?

2. Do you know of any microhydro installers in the state?
   
3. What is a good place to begin with permitting? I know that hydro
   
   

requires federal permission from the FERC, and I assume the Mass DEP

has to be involved, but do you know where the best place to start is,

or anyone that has gone through this process that might give me some

advice?

Many thanks,

Mark Corner

[Lowhead]

Mass tech also referred me to PVsquared and it was a bust.  They have done one install out in western MA somewhere and weren't really interested in me.  I want to do this myself for both cost and satisfaction reasons.  I'd like to chat if you want to email me.  The DEP just asked for a couple of clarifications and didn't even come to the ConCom hearing.  As soon as they saw the article from HomePower they said "thats it?" and that was the end of it.  Grid tie in MA is not going to bring in any cash yet but I am confident that future administrations will address net metering like NJ, California and even better Germany.

Andy