Biosphere Pond: A Sustainable Approach to Water Maintenance

1
Biosphere Pond A Sustainable Approach to Water
Maintenance
Group 3 Demo Times Thursday, April 23,
2009 1030-1100 AM 130 200 PM 300 400
PM

• Abstract
• In recent years, increasingly more focus has been
  directed towards renewable energy production for
  the sake of the environment, as well as political
  and economic stability. Consequently, the goal
  with this project was to develop a sustainable
  and environmentally compatible solution to a
  pressing issue on Penns campus. A brief survey
  of Penns facilities led us to the pond in King's
  Court English House, also known as the Biosphere
  Pond, which is overcome with algae bloom. The
  project team sought to develop and implement a
  solar powered water maintenance system to keep
  the Biosphere Pond clean.
• The systems design is based on the ponds size
  as well as historical weather patterns, which
  were used to simulate power generation for the
  Biosphere Pond. A prototype has been developed
  which circulates water throughout the pond and
  also pumps water through a UV sterilizer, which
  kills off unsightly bacteria. In addition, the
  system contains a single-axis sun tracker to
  improve energy conversion as well as a
  temperature sensor to prevent operation during
  freezing temperatures and to maintain system
  integrity. All of the systems processes are
  managed by algorithms installed on a
  microcontroller.
• Results for the Biosphere Pond include a
  successful implementation of a prototype which is
  able to keep the pond clean on a continuous basis
  during the spring, summer, and fall seasons.
  Ultimately, the design process proved that the
  Biosphere Pond concept is viable and also
  revealed that the design has the potential for
  alternative applications including larger pools,
  fountains, and perhaps even drinking water.
• Authors
• John Gillette SSE 09
• Xiao Ling SSE 09
• Ravi Patna SSE 09
• Zachary Zwarenstein SSE 09           
• Advisor

System Overview
Subsystems
Solar Tracker
As depicted in Figure 1, the system is comprised
of two subsystems solar electric (gray) and pond
cleaning (tan). The two subsystems are united by
a microcontroller which directs system operation
based on ambient temperature and the position of
the sun.
Solar Electric

• A single axis, active solar tracker was designed
  and built to improve solar energy conversion.
• The stepper motor drive system shown in Figure 2
  takes inputs from the controller based on the
  position of the sun and rotates the solar panel
  to the appropriate position along the east-west
  axis.
• The drive system is comprised of a stepper motor
  and gearbox.
• The solar panel shown in Figure 3 is oriented at
  40 degrees from the horizontal in order to
  improve solar power uptake. The angle of
  inclination corresponds to Philadelphias
  latitude, This angle was chosen for the prototype
  design as an average case between the optimal
  winter and summer angles.

The solar electric subsystem generates and stores
power to drive the load bearing system
components. It is comprised of the
following Photovoltaic array A twelve volt,130
watt solar panel was chosen for the system. The
PV converts sunlight into electrical current.
Battery bank The battery bank is used to
store power generated by the solar panel. It is
comprised of two six volt, 190 amp hour sealed
solar batteries wired in series. Charge
controller The charge controller prevents the
solar array from overcharging the batteries,
prevents reverse current flow from the batteries
to the solar panel, and prevents battery bank
discharge when the batteries have been depleted
beyond a certain point.
Pond Cleaning
The pond cleaning subsystem circulates water
throughout the pond and kills bacteria to keep
the pond clean Bilge pump A bilge pump was
selected for our system as they are durable and
are also easily manipulated with a
microcontroller. UV sterilizer Uses high
intensity UV light to kill bacteria, algae, and
viruses without harming other pond life.
Figure 2 Solar tracker drive system
Figure 1 System block diagram
Figure 3 Solar panel
Model and Simulation
Controller

• Various system configurations were modeled in
  Microsoft Excel to determine the appropriate
  battery and solar panel size.
• Optimal system configuration and parts were
  chosen by constructing and solving a linear
  program seeking to maximize battery bank power
  over the course of a simulated year while
  minimizing component costs.
• System operation was simulated using fourteen
  years of historical light intensity data in
  Philadelphia which is shown in Figure 4. The
  mapping from UV intensity to solar panel power
  output was determined empirically.
• Figure 5 depicts simulated battery bank power
  over the course of one year for the system
  configuration chosen.

• Figure 6 shows the system control algorithm
  which was written in C for intended use with the
  Motorola 68HC11 shown in Figure 7.
• System initialization includes variable
  definitions, interrupt configuration, and
  register setting.
• Every 30 minutes the program checks to see if
  the pump and or tracking parameters are
  satisfied.
• The pump parameter is responsible for activating
  the pump as well as the UV sterilizer. This
  condition is satisfied between the hours of 8AM
  10AM and 3PM 5PM. In addition, the condition
  also requires that ambient temperature be above
  38 F to provide a slight buffer above freezing
  temperatures.
• The tracking condition is satisfied when the
  clock is between the hours of 9AM 3PM. During
  these hours, a scanning algorithm is executed
  every once every 30 minutes.
• Following a scan, the solar panel is then
  realigned to receive maximum solar intensity
  provided the new orientation yields a sufficient
  improvement relative to the panels current
  position.

Figure 5 Simulated battery bank power
Figure 7 68HC11 Microcontroller
Figure 4 Historical UV intensity in Philadelphia
Figure 6 Flowchart of Control Algorithm
University of Pennsylvania Department of
Electrical and Systems Engineering Senior
Design Biosphere Pond