Perpetuity
St. Philip Neri School
Hydrothermal-Circulation System
Located in the southwestern Australian
Outback, Perpetuity replaces the abandoned Super Pit
Gold Mine, once the most productive mine on the
continent. Civil engineers viewed the 600-meter-deep
and 6-square-kilometer open pit as an energy “gold
mine“. The potential to generate clean, renewable
energy was not far below the citizens’ feet.
Named Hydrothermal-Circulation System (HCS), this hybrid uses
geothermal technology and silicon-based thermoelectric materials to capture
and convert the Earth’s heat, and subsequently the city’s waste heat, into
electricity. The innovative power plant generates electricity without using
steam or fossil fuels. The long-term infrastructure requires a power
generation plant (Figure 1) and support facilities including transmission lines,
water supply, water flow monitoring systems, and maintenance shops.
(Figure 1)
Perpetuity
St. Philip Neri School
Because 99.9% of the Earth’s crust is hotter than 100oC, mechanical
engineers took advantage of this heat to design and install a geothermal
closed-loop pipe system deep into the earth. The metallic piping system
contains saline ground water that has been processed by a series of filters
and a reverse osmosis system. Circulating in a continuous cycle, the potable
water captures the Earth’s heat and transfers it to the power plant. There,
the water passes through silicon membranes which absorb the heat, excite
the atoms, and cause electrons to be released. The electrons are collected
for processing by electronic circuitry and/or nanowire batteries, producing
usable alternating current (AC) electricity. The now cool water goes back
through a pump/filter, and the cycle starts again.
Electricity is transmitted and distributed from the power plant to the
city in three ways. The main power distribution process (Figure 2) uses heavy
gauge copper cables that run to power junction boxes and circuit breaker
panels located on each of the floors of the superstructure and likewise to
surrounding buildings.
Main Power Distribution (Figure 2)
Perpetuity
St. Philip Neri School
In addition, Perpetuity’s electrical engineers determined that 55-60% of
all energy generated dissipates as waste heat. Material engineers proposed
silicon nanowire membranes as a semiconductor to harvest and convert the
secondary heat generated by the city’s industry. The heat then passes over
the membranes, and in a process similar to the main power generating
facility, AC electricity is created via mini-power plants.
Lastly, chemical and materials engineers incorporated silicon into the
structure of rechargeable lithium-ion batteries, creating portable power. By
replacing the carbon material in batteries with silicon nanowires, ten times
more lithium can be stored, creating a longer battery life.
Land usage, water pollution, and supplies for thermo-electric devices have
little impact on natural resources. Since Perpetuity is located within an openpit mine, directional drilling techniques reduced the amount of land used.
Most geothermal schemes affect both surface and ground waters; HCS’s
closed-loop piping system with continuously circulating water eliminates
water pollution possibilities. Plentiful resources are available for silicon
membrane production as silica makes up 27.7% of the Earth's crust and is
the second most abundant element. Additionally, reverse osmosis removes
90-98% silica from the ground water, replenishing the resources.
The primary environmental impacts of geothermal energy production are
disposal of waste rock and filtered minerals. To reach the target
temperature, the metallic piping system was established 2,200 meters into
the earth. Civil engineers had the removed rock crushed into aggregate; it
was used for concrete and road pavement. Minerals filtered from the water
serve multiple purposes. Perpetuity’s industries use filtered sulfur for
fertilizers, cement, and adhesives. Zinc is used in the nano-composite
coating that lines the HCS’s pipes. In addition to thermoelectric devices,
silica is used to make glass.
Geothermal energy production has unsurpassed benefits. HCS uses a
renewable resource, heat, instead of nonrenewable, polluting fossil fuels
and/or nuclear power for energy. When compared to other energy sources,
this sustainable system has fewer mechanical failures and requires less land
usage for the facilities. HCS is not affected by weather or sunlight
Perpetuity
St. Philip Neri School
availability; it works day and night. No hazardous wastes exist, and minimal
waste products are generated.
Geothermal heat extraction’s main risk involves pipeline failure.
Perpetuity’s computer engineers developed a fully automated, centralized
system that monitors the closed-loop network’s overall function. If water
flow levels are outside the preset allowable range, the system automatically
signals the actuator to shut off the water’s flow in the affected loop,
simultaneously activating redundant systems. Pipes can then be repaired by
maintenance personnel.
An initial issue was Perpetuity’s location on land governed by the
Aboriginal Lands Trust. Approval was necessary before any development
could begin. To obtain approval, the following actions were completed: site
plan and land use proposals were filed, discussions with relevant Indigenous
stakeholders were held, and assurances were made that Aboriginal heritage
sites would not be impacted.
Another obstacle was the selection of the pipes for the closed-loop
system. Civil engineers considered these factors: water carrying capacity,
durability, cost, jointing process, maintenance, and the ability to transfer
heat into the circulating water. After reviewing all options, material and
mechanical engineers determined extruded steel pipes the most suitable.
Chemical engineers developed a zinc nano-composite coating to line the pipe’s
core thus reducing corrosion.
After analyzing tradeoffs (cost, appearance, efficiency), Perpetuity’s
Board of Engineers determined that Hydrothermal-Circulation is the most
sustainable and abundant energy resource. It has an initially high capital
investment, but operation and maintenance costs are low due to no fossil fuel
expenditures. Electricity generated by the HCS costs $.02 a KW hour
compared to $.10 a KW hour from typical power plants. Once the piping
system is buried in the earth, no one can see or hear the system. The power
plant appears as just another beautiful building within the city.
American Dream: Geothermal states, “Every geothermal energy facility
that has been built in the last 100 years is still in production.”
Hydrothermal-Circulation System is the best energy solution for Perpetuity.
Perpetuity
St. Philip Neri School
Figure 1- 30 words
Figure 2- 16 words
Body of essay- 951 words
Total- 997 words
Perpetuity
St. Philip Neri School
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