It's usually a stretch to link stationary power generation with the outskirts of the galaxy. But at the bottom of the world, that link is being forged as part of an interesting development called Project IceCube.
Project IceCube is an international neutrino telescope being built at the South Pole through funding from the National Science Foundation, with the University of Wisconsin-Madison managing the project.
According to the project managers, IceCube will search the depths of the Antarctic ice for neutrinos from violent astrophysical sources such as exploding stars, gamma ray bursts and cataclysmic phenomena involving black holes and neutron stars, which "opens a new window on the universe," according to one project spokesman.
Neutrinos are high-energy particles with no charge that have so little mass it is best described as "non-zero" mass, making them practically invisible. But they leave a trace that can be seen, called a muon. A muon is a charged particle left after a neutrino crashes with an atom that can be used to trace the neutrino's trajectory. However, these crashes are so rare, according to the IceCube project managers, that even though millions of neutrinos pass through our bodies every hour, they may never leave a muon trace within us during our lifetime.
For a muon to be visible, it needs to be within a medium transparent enough to allow light to travel through, dark enough to avoid the interference of natural light and deep enough below the earth's surface to avoid further interference from cosmic rays. The Antarctic ice in the "dark sector" of the South Pole meets these criteria. Finally, since neutrino crashes (and resulting muons, which show up as blue light) are so rare, the medium must be very large.
Thus, IceCube will be a section of ice approximately six-tenths of a mile square, instrumented with a widely spaced array of optical sensors.
"To do this, we drill 23.6 in. diameter holes approximately 8200 ft. into the ice," said Jeff Cherwinka, system engineer for the Enhanced Hot Water Drill (EHWD) team on Project IceCube at the University of Wisconsin-Madison. "For each hole we need to melt about 200,000 gallons of ice."
Once each bore hole is completed, a long electrical cable with 60 optical modules connected to a signal processing facility on the surface is quickly lowered in before the hole freezes shut. To complete IceCube, 70 to 80 bore holes are planned to be drilled.
The enhanced hot water drills produce 4.5 MW of thermal power, pumping 200 gpm of 190[degrees]F water at 999 psi. The water is delivered to the bottom of the hole with a 2.5 in. diameter hose to a drill head specially designed by the University of Wisconsin.
To power the drill, three generators have been placed onsite (two for prime power and one for backup). But the dark sector of the South Pole poses a few unique problems, notably the temperature and altitude. Temperatures at the drilling site in the South Pole typically fluctuate between -40[degrees] and 5[degrees]F during the summer "drilling" season and have been known to drop to as low as -112[degrees]F during the winter. The altitude at the drill site is equivalent to 12,000 ft. above sea level.
To procure the generator sets, the IceCube team utilized the primary logistical contractor to the National Science Foundation's United States Antarctica Program, Raytheon Polar Services Co. (RPSC). RPSC provides science, operation and maintenance support to sustain year-round research programs at three U.S. locations in Antarctica and research vessels in the region.
"Everyone needed to run a small town is hired," said Floyd Dial, electrical engineer--Facilities Engineering, Maintenance and Construction (FEMC) for RPSC. "The goal is to enable scientists to be free of the hassles of how to get to Antarctica, and how to get into the field to do their research, where to sleep, what to eat--we take care of all that. We also help construct instruments such as the IceCube telescope to facilitate their research."
RPSC was responsible for designing, procuring, shipping and installing the generator sets on-site, and is now responsible "for their operation and maintenance.
The three Caterpillar sets were provided by Syracuse Supply Co., Syracuse, N.Y. and Milton Cat, Milford, Mass. The sets feature Cat's turbocharged, six-cylinder 3306BTA diesel engines that were specially configured for the application. Each 10.45 L engine is rated 300 hp at 1800 rpm at sea level, has a bore and stroke of 120.65 mm x 152.40 mm and is fitted with a Woodward governor. The engines are coupled to Cat's 480/277 V, three-phase, 60 Hz, four-wire SR4B generators.
At the site, the engines are fueled with AN-8 jet fuel, the same fuel that the aircraft use that fly from the coast of Antarctica to the drilling site. "The characteristics of the jet fuel are actually close enough to No. 2 diesel that we can run the Cat engines on it without significant derating," said Dial.
This is important because "one of the major cost concerns is getting the fuel on-site," said Cherwinka. "To use diesel would be very costly, so using the same fuel as the aircraft allows us to fly in the fuel utilizing the fuel tanks that the planes already have."
Taking in account the difference in fuel and the altitude, the Cat 3306BTA engines were derated to 221 hp for the drill site. The coupled generator sets were also designed to operate in parallel, within the extreme temperatures defined by RPSC and at the high altitude. As an earth ground does not exist at the drilling site at the South Pole, the generator frames are bonded to an equipotential grounding plane.
The two generators that are run to power the drills are rated to produce 250 kW prime power. According to Cherwinka, during the 2005-2006 drill season, the peak power use at the site was 270 kW.
The three generator sets are enclosed in standard cargo 20 ft. x 8 ft. x 8 ft., ISO shipping containers, which were engineered, designed and constructed by Floyd Manufacturing, Norfolk, Va.
"We said we would take a crack at it because no one had ever done it before," said Joe Floyd III, director of sales at Floyd Manufacturing. "It was really uncharted territory for this type of container, especially when one takes in consideration the special requirements that had to be addressed to make the project an overall success."
Floyd said the enclosures ensure that interior temperatures of the unheated spaces within them enclosure would operate to -60[degrees] and to 50[degrees]F in the heated areas. "The containers were suitably modified with appropriate in/out ventilation equipment and rugged snow hoods to ensure that temperatures could be maintained as close as specified," said Floyd. "All interior walls, floor and ceiling areas were insulated with foamed in place, non-flammable, Isocuranate foam insulation, which produces an R-24 when applied at a 4 in. thickness. The floor was covered with 0.1875 in. steel diamond plate.
"In addition, each modified container contained a 100 Amp 'housekeeping' electrical panel system which would operate various lights, terminals, fans and heaters as required."
Each enclosure was also equipped with a [CO.sub.2], self-contained fire suppression system from BFPE. The exterior of the containers were painted with extreme temperature urethane paint.
According to Cherwinka, the majority of the electrical power from the generators goes to run the four 50 hp high-pressure pumps supplying water to the hole through the heater and to the 50 hp return water pump at the top of the hole. These pumps circulate 200 gpm of hot water to the hole and melted ice back from the hole.
The generator sets have been also modified with a waste heat recovery system from both the engine coolant and the exhaust to preheat the return water before going to the water heaters.
"When we are running the drill, 29 to 33% of the energy content of the fuel is delivered as electric power," said Cherwinka. "Calculations show we recover up to 40% of the energy in the fuel as heat that is used to raise the temperature of the return water tank, and operations suggest we might be getting a little more.
"This is important because the delivery of fuel to the South Pole is so expensive. We are also working hard to minimize the environmental impact, which means minimizing the fuel burned."
The waste heat recovery system includes a Baird Industries exhaust manifold that discharges the exhaust to the exterior, which is fitted with a Cain Industries exhaust silencer gas to glycol heat exchanger. The heat is then transferred to the return water with Bell and Gossett's GPX plate and frame heat exchanger. The exhaust ultimately exiting the silencer is cooled to about 350[degrees]F. Waste heat is also recovered from the engine jacket water, using Colmac Coil Manufacturing's fluid transfer products in the remote radiators. The pre-heated water is then pumped by the high-pressure pumps to AN8 jet-fueled burners before returning to the hot water drill in the hole.
According to Dial, the engine exhaust emissions comply with the requirements of the Antarctic Conservation Act, the Antarctic Treaty and the United States Antarctic Program Master Plan.
Cherwinka said the Cat generators also provide power for all the electronics, ventilation, electrical backup building heat, lights, water heater fans and pumps, etc. If there should be a loss of water flow, the generators can use the conventional radiators to dissipate the waste heat to the air.
The National Science Foundation funded $15 million to the University of Wisconsin--Madison in 2001 to begin construction of Project IceCube, which is scheduled to be completed in 2008. The total projected cost is $250 million.