Small-Scale Hydroelectric Plant Promises Profit

 

Posted 21 June 2011, by Joel Froese, Sustainable Plant (Putnam Media), sustainableplant.com

Micro hydroelectric power is making a comeback in electricity generation for homes, farms and small businesses. This trend is fueled by a number of factors including favorable regulation, rising energy prices and advances in automation—and do-it-yourselfers all over the world are diving in.

If there’s access to a stream, the only requirements to generate electricity are a 2 ft. drop in water level and two gallons of flow per minute. A hydroelectric system isn’t overly complicated, it isn’t difficult to operate and maintain, it has longevity and it’s often more cost-effective than any other form of renewable power.

This micro hydroelectric power plant generates 20kW of power, and is controlled by equipment from AutomationDirect.

Some experts say a successful micro hydroelectric plant will pay for itself in 15 years. At Red Bank Hydro in West Columbia, South Carolina, we implemented our own micro hydro system, Figure 1, and we expect to see a complete return on the investment after only eight years. After that, it will be money in the bank.

Although we’d never built such a system before, we were able to do so by using low- cost components and free technical support, both supplied by AutomationDirect (www.automationdirect.com).

Building a Hydroelectric Plant

In 1980 my father Arno Froese began investigating the potential for generating hydro-electricity on the property he had just purchased. The land is situated near the dam of a 64-acre communal lake, allowing access to the 10 ft height differential between the lake and the tail water on the other side of the dam.

My dad measured the amount of water flowing over the spillway and determined that an average of 40 cubic feet of water per second flowed through the pond, making it a marginally feasible hydroelectric project. However, this dream remained dormant until 2004 when my brother Simon discovered our dad’s research and decided to move forward.

On March 4, 2004, Simon began excavation for this project. For two years, the project was a challenging and sometimes disappointing excavation site, as it was necessary to dig 17 feet below lake level for the foundation while groundwater and mud continuously seeped into the hole. By the end of 2006, the underwater portions of the plant had been built, a four-foot aluminum pipe through the back of the dam was in place, the dam was restored, and the temporary cofferdam was removed.

On December 2, 2006, a refurbished 50 horsepower Francis turbine was purchased and installed. The turbine was tested and it was determined that the optimal speed would be 150 rpm. The next step was sizing the electrical generation equipment and designing the automation system.

This is the point where I became involved in the project. I have only a bit of experience in troubleshooting industrial electronics, mainly printing equipment, and I work as a computer programmer. I had never designed an industrial control system from scratch. Thankfully, I found an AutomationDirect catalog and recognized that they had the components I needed at a reasonable price, along with much needed free technical support.

Designing the Automation System

The hydroelectric system is powered by water draining from the lake that flows through a turbine which, in turn, drives three generators via a belt and pulley system (Figure 2). The generators are actually three Baldor Electric model L1177T 15hp single-phase induction motors.

When an induction motor is driven at greater than normal speed, it generates electricity. Output from the three motors was tied into the local electric grid via the same transformer that formerly only provided power to the property. The utility’s meter now turns backwards when the plant is supplying more power than consumed by the home and office.

Power is generated by water flowing through a turbine driving three electric motors that act as generators.

We realized that as a grid-tied induction-based generation system, the generator/motors would freewheel if the excitation current from the grid was lost. The grid acts somewhat like a battery that is being charged, providing a degree of needed resistance to the generators.

If the grid resistance were to disappear because of a power failure, the generator/motors could spin up to twice as fast as designed. We therefore needed to be able to automatically shut down our hydro plant in case of a grid power failure.

The turbine has an integral control gate that is used to adjust how much water flows through, from 0 to 100%. This control gate was designed to be opened and closed by a 12in. double-acting hydraulic cylinder, so the first piece of automation equipment installed was a Parker Oildyne 24 Vdc 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 12-volt batteries, which in turn are connected to two 12-volt battery charger/maintainers.

Control panel contains an AutomationDirect DirectLogic 05 Micro Brick PLC, a C-More HMI panel, I/O and associated components.

I decided that—although it was AutomationDirect’s smallest PLC at the time—a DirectLogic 05 Micro Brick PLC would be sufficient for this purpose (Figure 3). In October 2007, I placed our first order with AutomationDirect for the PLC, a proximity sensor to count shaft revolutions, a NEMA 1 enclosure, and various pushbuttons, terminals, DIN rail 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 (Figure 4). Although generating electricity with induction motors is not unusual, a system of three identical motors running from one turbine seems to be quite unique. Initial tests, (depicted in the Figure 5 video), in early February 2008 confirmed that this would work. All three motors properly synchronized when coupled by the belt drive. Later in the week, the first kilowatts of power were generated.

The turbine drives three electric motors via pulleys and belt drives.

Using only the demo version of the DirectSOFT 5 programming software, which limited me to 100 instructions, I programmed the DL05 for the following operations:

• an always-running “monitoring” stage that counts revolutions and calculates rpm
• a startup stage that activates upon pushing the startup button, opens the turbine, and engages the motors at the prescribed RPM
• a shutdown stage which fully closes the turbine and disengages the motors.

The shutdown stage was triggered by any one of three conditions: the shutdown button being pushed, an auxiliary contact on the motor contactors opening (meaning ac control power was interrupted), or RPM out of normal operating range.

Making, Measuring and Monitoring Power

In May 2008, we signed an interconnection agreement with Mid-Carolina Electric Cooperative (MCEC) and its supplier, Central Electric Power (CEP). In June 2008 we began feeding power into the grid.

Throughout the summer, we started and shut down the plant manually at our discretion, taking into account the lake level and the utility time-of-use tariffs. The utility paid us nearly twice as much money for power generated during the peak demand summer hours from noon until 10pm, a financial incentive that remains to this day.

Later that summer, we bought and installed a submersible water level sensor to monitor the lake level. This 4-20mA device was wired into an AutomationDirect 4-channel analog current input module which we added to the DL-05 PLC. We also bought the full version of DirectSOFT 5 software to add needed capacity and programming capabilities.

I was now able to program the system to automatically shut down when the lake level fell below a certain point. I also added an auto-start function that started generation whenever the level rose above the spillway in the dam. Again, this arrangement worked well, but we weren’t finished as we also needed to know how much power we were producing.

Although it’s possible to use transformers and signal conditioners to get voltage and current information into a PLC, it’s quite complicated in terms of both hardware and ladder logic. Instead, we purchased an AccuEnergy Acuvim II panel-mounted power meter. By installing the meter and an AutomationDirect RS-232/RS-485 converter, I was now able to poll the power meter over MODBUS to determine not only volts and amps but also instantaneous kW, cumulative kWh produced, the power factor, frequency and other relevant power parameters.

However, all this time I was only able to see these operating parameters by remotely logging into the computer and looking at the “data view” window of the DirectSOFT 5 programming software. Using that functionality, I was also able to do some rudimentary remote control such as starting or shutting down the plant, but it certainly wasn’t user friendly.

At about this time, AutomationDirect announced that their C-more touch panels now had IP-based remote operation capability and a built-in web server. I purchased a C-more panel and installed it, and began learning how to program it with the C-more programming software. By April 2010, I had four screens of valuable information and graphs that could be accessed not only in the power plant, but also via any computer via a web browser.

Connecting the control system to PCs on the property required only a wireless adapter, mounted in the window of the powerhouse.

To avoid running an Ethernet circuit the 100 feet between the power plant and house, I installed an inexpensive Asus WL-220gE portable wireless adapter in the window of the hydro plant building (Figure 6). This ensured reliable communication with the existing wireless access point in the house. The wireless adapter is powered from a USB port on the C-more panel, meaning the entire turbine control system is powered by low-voltage dc.

AutomationDirect proved to be a valuable asset to this project in many ways. Their easy to use website has free, comprehensive, and well-written documentation for each item in their catalog, which helped me design the automation system and select the components.

Their customer support forums at http://forum.automationdirect.com/ have extensive participation from veteran industrial control engineers who are happy to volunteer their expertise answering basic questions from beginners such as me. For situations where the forums weren’t sufficient, I could always pick up the phone and receive unlimited free technical support from highly qualified AutomationDirect technical support personnel.

Most importantly, AutomationDirect’s incredibly low prices allowed us to use robust industrial components, and also gave us the liberty to add advanced features that our low budget may not have otherwise allowed.

Return on Investment

Depending on rain and how much electricity is used by our home and office, we make between $30 and $300 per month in direct revenue from the power company. This does not include the savings on the power bill, which has gone down from almost $1,000 to around $300 each month.

With this $700 savings and the average $200 check from the power company, the micro hydroelectric plant makes about $900/month in income. Roughly, this means that we’ve already recovered about $30,000 of our $70,000 investment, and only another five years are needed to completely pay back the investment.

Over and above the financial benefits, we now have the satisfaction of owning and operating our own hydroelectric power plant. This has given us tremendous pride of ownership, along with the knowledge that we’re contributing to a sustainable environment.

 

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