small scale hydroelectric power

wasabi · May 25, 2002

Ok, I sent out a few requests and am beginning to get some feedback re: equipment. One company sent this proposal back, with a price tag over $8,000 not including wire or installation/w3tcompact/icons/shocked.gif.....about double what I was thinking it would be:

Based on the information you gave me, I've configured a hydro intertie system with battery back up for your future home in NC. This system consists of a 4-nozzle Harris hydro-turbine, a Trace C40 charge controller, a diversion heat load, A Trace SW4048/S power panel (with a DC disconnect, a Trace SW4048 inverter w/grid tie interface, an AC transfer switch), and (8) 6V/220Ah deep cycle batteries w/cables. Site-specific items such as wire, conduit, and small parts; are supplied by your installer. Installation is roughly 10-20% of equipment cost and typically completed by a local contractor.

Using the following specs for your hydro site (1000' of 3" pipe, 200' drop, and 120 gpm flow) you could expect this system to produce approximately 28 kWh per day. Assuming this minimum sized battery bank (required for the Harris/SW/intertie system) is 2500' from the hydro-turbine you would need #2AWG wire for a transmission loss of 33%.

I think the four nozzle Harris with magnetic and 48 volt option are the right items, considering the specs and distances we have to push the power, but based on what I'm reading and hearing from you guys, it seems we ought to be able to do without the batteries and instead use the grid. Maybe this vendor is just shooting for the works, but one of my goals is to skinny this to just essentials. Can I cut some of this out? Are there less expensive controllers? I'm in sticker shock!

ALso, I'm not yet clear on the best way to distribute power around the property. I get that pushing 48 volts as far as possible before storing/converting makes sense but what if, for example, I want to provide power to a barn in an upper meadow say, three quarters of a mile from main elec disrib point? Can I do that with underground wire carrying 110 or do I need an inverter at each location?

Any insights would be welcome.

knucklehead · May 25, 2002

Wassup, wasabi?

I scanned the thread, as I've been a closet home gen fan for years. Read Homepower, old Mother Earth mags, and Backwoods Home, along with library stuff. I have many of the same thoughts you do re: practicality vs greenness, etc.. One thing I quickly learned when sizing a gas generator (post Ice Storm up here in Maine), was that the single most important thing I can do to save money is reduce demand. We decided there was no need to cook a turkey, dry a load of clothes, and use the welder at the same time /w3tcompact/icons/smile.gif.

You've mentioned eliminating storage in your system as a cost savings. Have you considered downsizing system capacity, and using more storage? Batteries ain't cheap, and I don't know whether this is going in the wrong direction, but it may be interesting. Also, higher voltage will yield less loss over the same wire, because you are transmitting the same power with less current, and losses increase as the square of current flow. Transmitting at 110V would reduce losses over 48V, AC or DC, or at least allow smaller wire. I forgot a lot about the technical stuff, as we stopped thinking about storm prep and so forth once we got the big nasty stinky Generac. If we have a storm, I gotta go to work (indoors, though), so we decided it would be better to just plug in & pull a cord. I think you may want to investigate storage vs generating capacity, and higher voltage transmission.

I know I'm just skimming the surface here; can anyone else more intelligently address this?

BTW: it only takes 1/4 amp across the body (left to right hand, shoulder to legs, etc.) to put you into de-fib, or stop the old pump altogether. Don't let anyone tell you otherwise, or tell you any "Grandpa grabbed the wire tales." Food for thought.

Mark

Anonymous Poster · May 26, 2002

You Might consider a building a small dam at the top collection piont then run pipe down your 200' of head to get the peak pressure around 87 psi minus head loss in the pipe.

Just for a sanity check to see what is possible:
I calculate you have 200Ft X 200GPM/7.48gpf^3 X 62.4Lb/f^3 X 1/33000= 10.1 horse power before losses. I would assume a 30% eff system for now, head loss, turbine eff, generator eff etc. So you should get .3 X 10.1 X 745.7= 2262 watts. I think you will need a battery to store energy for peak demand.

Jeff

benewton · May 26, 2002

General comments:

This stuff costs, probably due to the limited number of systems manufactured.

The 48 VDC system is the way to go, since you'd be into 0000 cable if you went 24 VDC.
Be careful as you calculate your power requirements for the power panel, since you have to handle
the worst case load, not the average.

Be advised that inverters are really switching power supplies, and the current that they require from
the power source will be many times that required by the load. Power is equal to amps x volts, plus the
usual inefficiencies, so I doubt that you'll do very well without the battery pack. I note, too, that the Trace inverters will supplement the line voltage with battery power, for brownouts, but not the other way
around.

Finally, you only want to send power to remote sites as 120 AC! You want the DC lines as short as you
can get them, generator or battery. High voltage AC features much less in line losses than does an equal
DC voltage. Put the converters and batteries in the hydro power house, ship electricity where needed in
the AC format, and use normal appliances.

wasabi · May 27, 2002

benewton wrote: Put the converters and batteries in the hydro power house, ship electricity where needed in the AC format, and use normal appliances. 

Man did I ever need and want to hear this piece of info! Now that you have removed the mental cobwebs with one quick wave, I understand! I feel stupid for not having grasped this. Thanks!, this is going to make things a lot easier!

I assume the grid tie interface occurs after the conversion from 48 DC to 110 AC. If I want, can I put the grid tie interface remote from the hydro house? Anyone know if it should be put in line before other loads or splits, or does it matter?

benewton · May 27, 2002

I'm running Trace inverters, so I can only describe the interface to
those units, though I suspect most others will connect in the same
fashion.

The AC main goes into the inverter, after the breaker box, of course.
The AC side of the unit also supports a second AC source, which will
be automatically selected, if it is available, when the main fails. The
second AC source would normally be a generator, and the SW trace
units provide for auto starting, and exercise, of those units. Both
AC sources are 120 VAC, and they are tested for both voltage and
frequency. If both AC inputs fail, the unit selects the DC power and
continues operation in a seamless manner. I've lost no data on my
computer during power outages, and, if I don't have the AM radio on,
which is normal since the arrival of DSL around here, I won't even
know that there's been an outage.

There is a single DC input to the unit, in your case, 48 VDC. This is
a power bus, and would be supporting both the hydro and the battery,
the former through a charge controller, I'm sure. Since I've not yet
gotten around to solar or wind generation, I've not yet figured the
whole mess out, but I suspect that you need the battery charging
voltage out of the hydro/controller pair, since you'll be charging the
battery in addition to supplying your AC requirements.

I will note that the SW Trace units have built in battery chargers, but
they operate from the AC to the DC side...

Trace also provides for the selling of excess power back to the utility,
but upon investigation, the local utility here will not allow you to make
any profits, and, in addition, requires you to pay the basic connection
charge. To connect to the grid in that mode will require their permission,
which allows them to define what you MUST have in the way of
hardware, which is likely to be VERY expensive, since they are not
really interested in supporting the program, and forces you to allow them
to "inspect" the installation...

And, once they officially know, just think of how much more valuable your
property will be! No doubt your local government will be very interested
in that increase in value, and very unconcerned about your ability to pay...

I run my system in the on line, battery backup mode, and purchased most
of it over the net, doing the install myself.

Finally, if you go over to Trace Engineering's site (www.traceengineering.com),
you can download the operations manual for the unit of your choice. That'll
give you some hard information to consider.

Oh, one more thing.
Since I have to use electronics test equipment, I never considered anything
other than the SW units. Even if I didn't have the sensitive electronics, I don't
think I'd consider any modified sine wave unit (Trace DR series, for instance),
since anything other than an almost pure sine, as opposed to squared sine, wave
is looking for trouble.
Too, IMHO, these things are a one time/lifetime install, and, over 20 years
$400 - $500 in the initial investment is unimportant.

Slamfire · May 27, 2002

Generators are poor things for constant power. The brushes carry full load current and wear quickly. Alternators on the other hand only use brushes for exciter current. The use of one also frees you from the inefficient inverter that changes the DC to AC. The only problem you'd have to solve would be some speed governor to keep the frequency the same as the system you'd hook up to. As a side benefit, using a transformer will filter out a large amount of the harmonincs that occur in the generation of AC.

mbsil · May 29, 2002

Batteries good. Grid bad.

If the grid goes down, your "grid as a battery" scenario obviously goes down with it. You would then be able to use only as much as you can generate (produce via whatever means - solar, wind, hydro).

Given that some devices have startup surges that can be 50%+ of their operating current, you may not be able to power the fridge, etc. because you lack the startup current needed.

The battery bank gives you power sans grid and provides the extra current needed to "start" the motor on the fridge in the absence of line power.

The HomePower.com site has many EXCELLENT diagrams included in their articles. I have all the issues on CD-ROM and have been re-reading some of them in anticipation of installing a wind generator. That's a generator powered by the wind...not a generator OF wind. /w3tcompact/icons/smile.gif

wasabi · May 29, 2002

That's a generator powered by the wind...not a generator OF wind.

I resemble part of that remark! /w3tcompact/icons/grin.gif/w3tcompact/icons/smile.gif/w3tcompact/icons/hmm.gif/w3tcompact/icons/blush.gif

wasabi · May 29, 2002

Too, IMHO, these things are a one time/lifetime install, and, over 20 years $400 - $500 in the initial investment is unimportant. 

I certainly agree with that philosophy Bruce. It comports with one of my alltime favorite sayings, blatantly lifted from TQM studies:

Build it Right the First Time!!