We realized that, as a grid-tied induction-based generation system, the generator/motors would freewheel if the excitation current from the grid were lost. The grid acts somewhat like a battery being charged, providing a degree of needed resistance to the generators.
If grid resistance were to disappear because of a power failure, the generator/motors could spin up to twice as fast as designed. We needed the ability to shut down our hydroplant automatically in case of a grid power failure.
The control panel contains an AutomationDirect DirectLogic 05 Micro Brick PLC, a C-More HMI panel, I/O, and associated components.
The turbine has an integral control gate to adjust water flow from 0 percent to 100 percent. This control gate was designed to be opened and closed by a 12-inch double-acting hydraulic cylinder, so the first piece of automation equipment installed was a Parker Oildyne 24V DC hydraulic reversible pump to operate the gate.
The power for the pump and all the low-voltage control circuits is supplied by two deep-cycle 12V batteries which are connected to two 12V battery charger/maintainers.
When a shutdown signal from the control panel or a fault condition occurs, the shutdown procedure is simply to run the pump in the “close” direction for 60 seconds and open the contactor to the generators. The hydraulic pump has a built-in pressure relief valve that allows it to run safely a minute or two after maximum extension or retraction of the cylinder.
It was crucial that the system also monitor rpm and shut down based on either overspeed (caused by a disengaged generator or broken belt) or underspeed (insufficient power generation) conditions, so it was time to install a programmable logic controller.
I decided that, though it was AutomationDirect’s smallest PLC, a DirectLogic 05 Micro Brick PLC (pictured above) would be sufficient. In October 2007, I ordered our first PLC, a proximity sensor to count shaft revolutions, a NEMA 1 enclosure, and various pushbuttons, terminals, DIN rails, and wire ducting. After a couple of weeks of learning ladder logic and playing around with the PLC, I began to install the basic automation system.
A local bearing distributor determined what belts, sheaves, and shafts were needed to transfer rotation of the turbine to the three Baldor induction motors. Though generating electricity with induction motors is not unusual, a system of three identical motors running from one turbine seems to be unique. Initial tests in February 2008 confirmed that this would work. All three motors properly synchronized when coupled by the belt drive. Within a week, the first kilowatts of power were generated.
I think you're absolutely right, NYeng. This would not be an easy hurdle. I would guess that you're right about it being cost prohibitive. That's a shame, because this is a technically sound project.
I applaud this project from a technical and ingenuity standpoint.
However, I tend to agree with the pessimism on the regulatory stuff. Here in NY, the environmental hurdles as well as the federal & state energy commisions/authorities and utilities would make it nearly impossible. The thousands you would have to spend on attorneys, permits, fees, and political contributions to make it happen legally could buy you electric power from the utility for a hundred years or better. I think in this state the only thing attempting such a project would get you is legal trouble and the related fines and attorney fees.
The idea may or may not be impractical, but the comments are entusiastic. Those who comment on the Design News site are passionate about their views. I think that's very clear in this thread as well as the other comment threads.
Design News asked for people to moderate and presumably add comments to their web site. You had to make a certain number of posts to remain in the system and to receive a stipend or whatever it was called. I get the feeling that this thread is more about maintaining a posting record than making real comments about an idea that is impractical in almost every state.
You are absolutely correct. There's little more than .001 hp available from water @ 2 GPM dropping 2 feet. If this was able to produce 20 Kw we'd have ourselves a nice perpetual motion machine! I think that the heading of the article is misleading. The article itself is worthy.
This is a very good work! I wonder if this is affordable for developing countries like Mexico or Latin America where there is good potential for micro hydroelectric generation, how expensive is the system and where can I purchase one? Thanks
I have yet to connect our Micro Hydro to the grid. Except for a few hours of testing, when I discovered what 'absolute value' metering meant, we have been running autonomously since commissioning 2006. I used pumps as turbines and 3 phase motors as single phase generators to cut costs. I don't think I gave up any efficiency at all since I'm getting a bit more than my initial calculations indicated. NY just passed the net-metering law for under 25kW hydro, so we'll be hooking up soon.
Syncing induction generators of a few tens of KW to each other or the power-line is not a problem as long as they are within a few RPM or Hz of each other.
You're numbers look spot on. At that scale, standard induction motors might achieve 70%-80% efficiency, and the turbine/penstock losses are in that range as well.
Thank you, renuengineer for that explanation of how induction generation works; I couldn't have done it better!
Re: FERC, they don't involve themselves with individual installations this small. In South Carolina, our department of Health and Environmental Control does regulate dams & reservoirs, but our lake had already been in existence for over 100 years. The utility company was satisfied with some cursory drawings and assurance that we were entirely induction-based. The only official inspection was that of the county building department.
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