Download In-Pipe Water Generator

In-Pipe Water Generator
Brian Davis,1 Chris Dorchester,2 Ted Geldmacher, 3 Tim William,4 Salah Badjou, PhD.5
Abstract – With today’s high energy demands and concerns, the wave of the future is clean, renewable energy.
There is untapped, wasted energy flowing through our towns’ water mains. With an in-line turbine generator, this
continuous flow of water can be harnessed and converted to electrical energy. The proposal was to design and build
turbine generators to generate the optimum amount of electrical energy based on town pipe diameters and flow rates,
and geographical location. With these generators installed and connected to town grids, the demand on power plants
will be reduced, thus, cutting down on pollution and energy costs. This project was completed in a semester-long
junior-level Electromechanical Design course of the interdisciplinary electromechanical engineering program at
Wentworth Institute of Technology. All goals were met, a functioning prototype developed, and the final
calculations made for the installation of a turbine in Keene, New Hampshire with a power output estimation of 71
kW.
Keywords: Renewable energy, turbine, generator, electric grid
INTRODUCTION
With the growing concern of a cleaner living environment, renewable energy has generated a large interest and
market [9]. With a high potential energy stored in water towers through the pressure caused by gravity, there is
potential to capture that energy using an in-line turbine generator [11]. This project consists of taking an existing
water delivery system, in Keene, New Hampshire, and designing an optimal turbine-generator set-up specifically
tailored to their parameters. By focusing on towns with large water demands and high water towers we can optimize
the electrical output of our generators, and create a larger power output. With water coming in from a
geographically higher location, the potential energy, and flow rates increase, thus increasing the amount of
electricity made. We plan to capture some of this untapped energy by converting the potential energy of the water
into electrical energy that would take the strain off of power plants and other power sources [10]. The major
essential components required for this project are a proper turbine, and an economical generator. The generator will
be coupled to the turbine, used to convert the mechanical energy from the water into electrical energy. There are
several types of turbines, and each is designed for specific parameters, so picking the proper class of turbine will be
crucial to the functionality of the design. Once a turbine has been carefully chosen, and energy calculations have
been properly made, a generator can be chosen to maximize efficiency. Currently, this is an untouched, renewable
energy source, but with our generators installed and connected to town grids, the demand on power plants will be
reduced, thus, cutting down on pollution and energy costs, while generating revenues. The objective of this project
was to use the pre-existing mechanical energy of flowing water in town systems to create usable electrical power.
The second stage will be put forth in building a small working prototype that will demonstrate the design
concept and electronic aspect of the design. Our prototype will demonstrate the functionality of an in-pipe water
generator, along with all working electronics. The prototype will consist of a pump forcing water through our
fabricated turbine, which is coupled to a DC motor. A microcontroller will read voltage from the generator to
control an actuator valve that will control flow through the pipe [5], and an LCD will display real-time voltages.
DESIGN, ANALYSIS, HARDWARE DESCRIPTION, AND VALIDATION
The system block diagram is shown in Fig. 1 below. Water flows from a reservoir, through a flow
regulating actuator, a turbine, and then onto its original destination. The generator outputs a voltage into the
microcontroller that controls the actuator valve and prints the voltage value onto an LCD display.
Correspondence: Prof. Salah Badjou, Department of Electrical Engineering, Wentworth Institute of
Technology, Boston, MA 02115. Email: [email protected]
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
Fig. 1: Block diagram laying out the operations and flow pattern of the entire system
The block diagram of our prototype design is shown in Fig. 2. In general it is the same concept as the full
scale block diagram, with the addition and removal of a few elements. A submersible pump was added in Fig. 2 that
was used in the process of pushing water through the turbine to spin the DC motor. Fig. 2 does not include an
inverter and the interface to the power grid, partly because of lack of time but mostly because these are secondary to
the basic concepts under test. Another difference is that the water is recycled from the turbine back to the water
supply in Fig. 2, instead of carrying on to some destination as in the actual full scale design.
Fig. 2: Block diagram for the prototype model that we have designed and assembled slightly different than the full
scale model block diagram.
Generator:
In the standard brushed generator, the brushes ride along the commutator to direct current from the coils to
the system the generator is powering. With this type of generator there is an unnecessary amount of heat and
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
friction created by the brushes. These carbon brushes are constantly riding along the commutator, making the
generator not only less efficient while in use, but also subjected to regular maintenance [5]. To overcome the
efficiency and maintenance problems inherent to brushed generators, most modern hydro-electric power plants now
use brushless generators. With a brushless generator, the coils remain stationary while the magnets are rotating.
Therefore, the rotating part of the generator requires no electricity and thus, no brushes. This design is much more
efficient in terms of friction, heat, maintenance, and overall efficiency. The brushless generator is clearly a far
superior design; however it is far more expensive and more difficult to create a controller for [5]. Nevertheless, the
advantages of a brushless design far outweigh the disadvantages and therefore it will be used on the full-scale
system.
In the prototype however, a small brushed DC motor was used solely because of cost, simplicity, and
availability. This motor was extracted from a small centrifugal oil pump and was used as the generator, linked to the
turbine. The shaft of the turbine and the shaft of the motor had different diameters making it necessary to fabricate
an aluminum coupling to fit the motor shaft on one side and the turbine shaft on the other end. Two holes were
drilled and tapped into the coupling to serve as set-screw locations to ensure that both shafts would fit securely
without any movement.
Turbine:
Given the water system specifications for the town of Keene, New Hampshire, the proper turbine type for
this project was found to be a Francis. The Francis turbine is a very efficient turbine used in most hydro-electric
applications [10]. In order to take full advantage of the efficiency of this type of turbine, the system must first meet
some requirements. For example, since the town of Keene has a head of 70 meters, a water main diameter of 0.5
meters and an average flow rate of 0.11 cubic meters per second [6], it successfully meets the majority of the
requirements for a Francis turbine. The only other turbine choice that could potentially work for this system is a
Pelton, however this is not nearly as efficient [7]. The Francis was the ideal choice for this full scale system, but it
was not an option for the design of a prototype.
When constructing the turbine for the prototype of the project, because of the large required head, a
miniature Francis turbine could not be used and thus, a water pump was used in place of an elevated reservoir.
Generally, a water pump will pump water through a system using an electric motor to turn an impeller. However, in
our case we used this device in reverse, therefore the impeller became our turbine and the motor became our
generator. Since the device used for the project was initially intended to be a pump, modification was required to
create a functioning turbine.
To create suction for use as a pump, the impeller was pressed into the pump housing, bending the fins of
the impeller and causing massive amounts of friction. Therefore the pump housing was bored out until the impeller
could rotate without the fins touching the side of the housing. However, large amounts of friction still existed so
further modifications were required. The hole in the housing for the output shaft to exit was far too small and the
shaft was unable to spin freely inside. To solve this issue, the hole was drilled out and a sealed ball bearing was
pressed into it. A new shaft was then fabricated to be pressed into the center of the newly installed bearing. With a
bored out housing and the shaft of the impeller pressed into a ball bearing, friction was dramatically decreased. The
impeller was then able to spin more freely with much less water flow required. With these turbine modifications the
prototype became a much more efficient device and was able to function with a much smaller head.
Although the prototype turbine spun freely with the reduction in friction, the system could not function
without an unreasonably large head. This is due to the fact that a scaled-down version of the Keene turbine system
cannot be feasibly constructed. As explained by the concept of similitude, a scale version of a fluid system cannot
function identical to the full-scale system unless the fluid properties also change [12]. Therefore to simply scale
down the head and pipe diameters of the full-size system, the fluid would be required to have an unrealistic
Reynolds number and thus, could not be created for demonstration purposes [12]. The Reynolds number of the
scaled down model required the head still too large, at 100 m, to be able to practically use it as a prototype [8]. This
would defeat the purpose of scaling down the project and thus, a different approach was taken involving a pump.
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
Code:
The flow chart of Fig. 3 describes the function of the system and the algorithm for the operation of the
microcontroller. The generator voltage is digitized and read by the microcontroller. The generator input voltage is
then used to drive an actuator valve which controls the flow through the turbine in order to maintain the generator
voltage at a constant value. If the voltage reading is low, the valve will open and allow more water to flow through
the turbine. The increased water flow will spin the turbine faster and produce a higher voltage. Likewise, if the
voltage is too high, the valve will slightly close to reduce the water flow, reducing the rotational speed of the
turbine.
In order to read the voltage level produced by the generator, we had to connect the terminals of the
generator to the microcontroller. In our project, we used the Arduino Uno as the microcontroller. The negative
terminal is connected to ground and the positive terminal to an analog input pin.
The microcontroller code controls the actuator valve on the basis of the input generator voltage. Depending
on whether this calculated voltage is low or high, the valve will close or open accordingly. For the actuator, we used
a stepper motor, for which we wrote the main portion of the code.
Fig. 3: Flow chart for the microcontroller program
Since the output of the generator is to be displayed on an LCD, we also needed to write the corresponding code for
the Arduino to communicate with the display.
Actuator Valve:
In order to control the flow through the system, a valve was constructed that would operate based on the
generators output. The actuator valve consisted of a stepper motor, coupling, and a water valve. The stepper motor
was mounted onto stilts to prevent the whole motor from spinning, rather than just the shaft. The stilts were then
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
fastened to a plywood board. A coupling was then used to pair the stepper motor with the water valve. The coupling
was drilled to the diameter of the stepper motor shaft and the water valve shaft. Also, the coupling had small set
screws in the side to secure the fixture and to allow the stepper motor’s momentum force to translate to the water
valve. To prevent the valve assembly from rotating as the stepper motor rotated, pipe hangers were used to secure
the valve to the plywood board. The valve is crucial to insure that the output of the generator remains constant. If the
output is low, the valve will open and allow more water to flow and increase the output voltage. If the output is too
high, the valve will slightly close restricting the water flow and lowering the output voltage. This maintains the
generator value within an acceptable range.
Circuit:
The integrated electric module of the system is shown in Fig. 4. The circuit needed for the design was a
driver circuit to control the stepper motor. The stepper motor has four magnets within it that pulse in a sequence to
spin the motor. To control the magnets, four transistors work as switches to pulse in the needed sequential order.
The digital pin goes high and allows current to flow through the transistor, delivering power to that magnet. In order
to give the stepper motor the required voltage, an external 12V power supply was added to the circuit.
The circuit also includes the generator used in the prototype design. The negative terminal on the generator
is connected to the ground pin on the Arduino while the positive is connected to the analog pin 0. By connecting the
positive to an analog pin and with the proper code, we were able to read the value that was output from the
generator.
The final component of the circuit is the LCD display. The LCD allowed for the project to run without the
need of a laptop. Once the code is uploaded to the chip, the Arduino can then run that program from a 9V DC wall
adapter. The LCD was used to display the voltage reading of the generator as well as a prompt to tell the operator if
the voltage is too high or too low. The LCD is connected to the Arduino using the 5V, ground and the TX pin on the
Arduino. The TX pin is the serial pin that lets the Arduino communicate with the LCD. The Picture below, Fig. 4,
shows how all of the electrical components are integrated together.
Fig. 4: Integrated electrical components.
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
Water system:
Rather than raising the water source to achieve a larger head on the prototype, a submersible pump was
used. By using a water pump, it was possible to simulate a much larger head without increasing the size of the
prototype. Instead of using a bucket full of water above the turbine to create gravity-fed flow, the bucket now
contains a submersible pump. Though this differs from the gravity-powered full-scale system, it creates a much
more realistic and accurate scaled model.
The structure of the prototype water system consists mainly of a wooden structure that has the subassemblies mounted to it. The wooden frame is approximately four feet tall and supports the water tank on the top.
As seen in Figure 2 above, the main uprights of the structure are made of pine studs with dimensions of two inches
by four inches. The top and bottom of the structure are also made from the same studs and connect the upright
supports together. The top platform that supports the tank is made from plywood and fastened to the top of the
upright supports. The wooden structure was fastened together using wood screws.
On the top of the structure a bucket filled with water simulates the water reservoir of Keene and the
submersible pump inside it simulates the proper head. The components of the water turbine system are installed on
the front of the wooden structure. First in line coming from the water tank is the actuator valve, which controls the
flow of the water into the turbine. Next is the turbine which captures the energy from the flowing water. The main
electronics control box is mounted on the side of the turbine,. The control box houses the microcontroller and the
driver circuit board for the actuator valve. The control box also has the LCD display mounted on it, providing
information to the user about the output voltage from the turbine. The final assembly of the prototype is shown in
Fig. 5.
Figure 5 – Final prototype assembly.
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
Materials for small scale assembly:
•
•
•
•
•
•
•
•
•
•
•
5 gallon bucket
Wooden structure, to support bucket
Standard 3/4" water spigot
10 feet 3/4” rubber tubing
1 Chuckmast drill pump
Arduino UNO microcontroller
LCD display screen
Stepper motor
Cylindrical aluminum stock
Submersible pump
9V power supply
Calculations:
The projected power figures obtainable at the proposed Keene, New Hampshire site were calculated as
follows:
Q = 2400000 gal/day = 0.11 m3/s
D = 0.5m
L = 70m
Z1 = 70m
Vavg. = 0.6 m/s
Reynolds Number = Re = 41.8
g = 9.81 m/s2
(1) = ℎ = ∗ ∗ ! = 4#
Using the energy equations, we derive equation (2) which now with the head loss calculated, can be used to
calculate to head loss taken from away by the turbine.
$2&'(('
)* = ℎ+ = $,- & − /
0 2 − ℎ = 66#
21
Now with the total head loss due to the turbine calculated, a power output can be estimated through equation (3).
$3&56
7
#('
)* = 5 = $8761ℎ(76(
& ∗ $9& ∗ $ℎ+ & = 71<=
Using the above equations and fluid properties of water, a value of 71 KW was estimated to be generated from the
Keene reservoir.
Discussion:
From the given parameters listed and used in the above calculations, an average power output for the Keene
system has been calculated and found to be roughly 71 kW. This has been calculated using flow rates, and specified
pipe diameters given to us by an official from the Keene facility. Calculations were made, taking into account head
loss due to friction in the pipe lines, using the energy equation derived from Bernoulli’s equation. The 71 kW
harvested power, obtained by assuming 100% efficiency, is a fairly substantial amount of energy, considering it is
100% free and natural since it runs from a natural reservoir located atop a hill. Operating at an estimated 65%
efficiency, the power output, 46 kW, is still a substantial and usable amount that can either be fed back into the
treatment facility to compensate for some of their energy requirements, or even sold back to the grid.
Moving from the full-scale model to the prototype, the flow chart of Fig. 3 changes slightly, as mentioned
before. The main differences are the absence of the inverter and the power grid, and the fact that a submersible
pump is used to push water through the turbine. Another difference is that in the prototype, the water is recycled
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
back into the water supply forming a closed-loop system instead of carrying on to a final destination as an open-loop
system. Despite the minor differences, the concept for the design remains the same.
The reason that a submersible pump was used in the prototype design was that we were not able to obtain a
small Francis turbine, forcing us to use a rubber water wheel. With this new set-up in place the turbine was very
difficult to spin and despite many methods and different techniques used, gravity alone was not enough to spin the
turbine fast enough to create a readable voltage. As a last resort, the team decided to replace gravity with a pump
that would pressurize the system and give it enough force to keep the turbine spinning at a constant rate. Once the
pump was in place, the system began operating as intended, freely spinning the turbine-motor system. With the
pump running, a ball valve positioned upstream of the turbine was used to control flow. The voltage from the DC
motor was displayed on the LCD in real time as we controlled the flow. We observed a range from .15V for the
smallest flow rate to .43V for the largest flow rates.
Using the experimental voltages obtained (0.15V - 0.43V), we set thresholds in the code for the actuating
valve, and picked a nominal value of 0.25V as an ideal condition voltage that the valve is responsible for
maintaining. When the code was updated and downloaded onto the Arduino, the team ran secondary tests on the
prototype to test the actuating valve. Again, using the ball valve up-stream of the turbine to control flow, the team
ran the system at varying flow rates to ensure that the actuating valve was opening upon minimal flows and closing
upon larger flows, working to maintain the nominal 0.25V. After testing, it was determined that that valve was
opening and closing at the response of alternating flow rates.
Following the previous test, the team concluded that the entire system was working satisfactorily and
responding as we designed it to. There were a few small issues that we would have liked to address, however we
simply did not have enough time. These issues were not vital to the ultimate performance of the prototype, therefore
could go unaddressed until a future time. First and foremost, the very first change that would be made would be to
replace the home fabricated turbine with a precision machined and designed inline Francis turbine. Requiring far
less energy to spin and creating larger velocities with the jet this would make a drastic difference in output voltage,
ultimately providing more power. Using this turbine would also allow us to use gravity as the driving force of the
turbine rather than the submersible pump. The second change that the team discussed was the motor mount. The
mount used in the experiment was built using two supports, which worked to keep the motor stable, but there were
still some vibrations that could be eliminated by adding two adjacent supports that would surround the motor
completely offering more stability and reducing vibrations. Putting some type of padding around the motor was also
discussed as a solution to reduce vibrations. These are minor issues with respect to the system as a whole, with more
time the team would have worked out a solution to fix the problems and increased the mechanical efficiency of the
prototype.
Conclusion:
The purpose of the water turbine project was to capture unused energy in the drinking water systems of
cities and towns and to turn that energy into useful electricity. Hydroelectric power is not a new technology;
however our plan was to use the same principle but on a smaller scale. The water turbine project is using smaller
turbines that will connect to water mains headed into the cities and towns rather than the larger ones in dams.
Through strategic placement of these turbines, at the base of hills or large water towers, unused excess energy can be
captured.
In the completion of our project, we built a small prototype that represents the main ideas behind the
project, as well as based our calculations for a turbine selection on the parameters of the water supply in Keene, NH.
Our prototype takes the energy of the flowing water coming out of the submersible pump and from its travel through
our turbine is converts that kinetic energy into electrical energy. Our prototype is not a scaled representation;
however it displays the functionality and feasibility of using a turbine to create electrical energy. Our prototype did
an excellent job of demonstrating this and proving that the energy flowing through water mains can be captured.
Throughout all of the phases of design in this project the student members of the team have continued to
learn and solve problems. One of our largest struggles was dealing with the complications of trying to produce a
scaled representation of the system. After weeks of calculations and research the team determined that a scaled
representation was not feasible. This was a large learning experience, in how it could not be scaled and also in
learning how to go back and find a solution to the problem. The team base knowledge was also expanded upon
greatly throughout the project with the research we conducted on turbines, town and city water systems, DC and AC
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012
motors, valves, stepper and servo motors. Important skills both in interdisciplinary research and design were
developed. The research was extensive and included acquiring the relevant fluid mechanics knowledge as the team
had not previously taken a course in fluid mechanics.
In our full scale design, basing our information on the parameters of the City of Keene, New Hampshire’s
water usage, we calculated the power output to be seventy-one kilowatts. In the calculation process for Keene we
were able to meet with the town water authorities and collect the statistical data of the city’s water usage and base all
of our decisions for the turbine selection and power output on this real data. The use of the real data and the results
obtained are an excellent representation of how the system would work if implemented into a real water supply.
The successful completion of this water turbine project shows that there is energy in our everyday lives that
can be captured and used to our advantages. With the forecast of energy becoming hard to find in the coming years,
it is important that we do what we can to be resourceful. This water turbine project is a perfect example. We are
capturing surplus energy that would otherwise be wasted and turning it into usable electrical energy. The project is
an excellent example of an interdisciplinary project involving electromechanical engineering and renewable energy.
REFERENCES
1.
"Arduino Playground - LCDVoltmeter." Arduino - HomePage. Web. 30 Mar. 2011.
<http://www.arduino.cc/playground/Main/LCDVoltmeter>.
2.
"Arduino - StepperUnipolar." Arduino - HomePage. Web. 30 Mar. 2011.
<http://www.arduino.cc/en/Tutorial/StepperUnipolar>.
3.
"Controlling a Stepper Motor with an Arduino | Azega." Azega.com. Web. 29 Mar. 2011.
<http://www.azega.com/controlling-a-stepper-motor-with-an-arduino/>.
4.
"Controlling a Stepper Motor with an Arduino Part 2 | Azega." Azega.com. Web. 29 Mar. 2011.
<http://www.azega.com/controlling-a-stepper-motor-with-an-arduino-part-2/>.
5.
"Electrical Generator." Wikipedia, the Free Encyclopedia. Web. 17 Mar. 2011.
<http://en.wikipedia.org/wiki/Electrical_generator>.
6.
Hanscom, Donna. "Keene Water Information." Personal interview. 1 Apr. 2011.
7.
"Hydro Turbine, Water Turbine, Francis Turbine, Kaplan Turbine, Bulb Turbine, Pelton Turbine, SCADA
System." Chinese Hydropower Equipment. Web. 28 Feb. 2011.
<http://www.hydropower.com.cn/productsservice.asp>.
8.
Munson, Bruce R. Fundamentals of Fluid Mechanics. Hoboken, N.J: Wiley, 2010. Print.
9.
"The Growing Popularity Of Green/Renewable Energy In America For Cost Savings And Reduction Of
Pullition The Way To Green Energy." The Way To Green Energy. Web. 26 Feb. 2011.
<http://www.thewaytogreenenergy.com/the-growing-popularity-of-greenrenewable-energy-in-america-for-costsavings-and-reduction-of-pullition/>.
10.
"Turbine." Wikipedia, the Free Encyclopedia. Web. 20 Mar. 2011. <http://en.wikipedia.org/wiki/Turbine>.
11.
"Water Tower." Wikipedia, the Free Encyclopedia. Web. 05 Apr. 2011.
<http://en.wikipedia.org/wiki/Water_tower>.
12.
“Similitude (model)” http://en.wikipedia.org/wiki/Similitude_(model)
Biographical Information:
1-4: Brian Davis, Chris Dorchester, Ted Geldmacher, and Tim Williams are currently senior students
enrolled in the five-year EAC-of-ABET accredited interdisciplinary program of electromechanical
engineering at Wentworth Institute of Technology, Boston, Massachusetts. They completed the
present project in their Junior year.
Contact: Brian Davis: [email protected], Chris Dorchester: [email protected], Ted
Geldmacher: [email protected], Tim Williams: [email protected].
5- Salah Badjou is professor of electromechanical and biomedical engineering at Wentworth Institute
of Technology, Boston, Massachusetts. Contact: [email protected]
2012 ASEE Northeast Section Conference
Reviewed Paper
University of Massachusetts Lowell
April 27-28, 2012