CASE STUDY HALLEY VI
90% of the energy of conventional diesel. The generators provide all the station’s electrical power and most of its heat. Heat from the generator’s cooling system is used to warm the accommodation’s fresh air supply, providing space heating through a radiator-based wet system and to heat the central domestic hot tank. The station also has AVTUR fuelled back-up boilers to provide additional heat in the extremes of winter or when the electrical demand is low. The decision to use a series of smaller
CHP units allows the electrical supply to be matched to demand. All units use common replacement parts, while the choice of smaller engines make it easier to manhandle the units should they ever need replacing. ‘Repetition and adaptability is the key to the design’s success in this remote location,’ says Alan Fox, director of building engineering at Aecom and lead mechanical engineer on the project. Piped and cabled services from the life support modules pass from one pod to the next through a warm service zone, located beneath the floors of the pods. Each pod has a small plant room containing a standardised heat recovery ventilation unit, in addition to connections to heat and electricity from the CHP plant and hot and cold water. The ventilation units have been designed to cope with an average outside air temperature of -20°C. The units have three-stages of heating: first, a frost heater pre-warms the air before it passes through a plate heat exchanger; after that a second heater battery is used to regulate the supply air temperature. When the outside air temperature drops below -30°C, the units switch to full recirculation, supplemented with occasional, minimal bursts of fresh air to keep conditions habitable. ‘Below -30°C we effectively don’t take in
fresh air to the pods because the loads are too high,’ explains Fox. The warmed air to the sleeping modules is also humidified using an electric humidifier to prevent it from becoming too dry. When demand for heat falls, heat
from the CHP is diverted to melt snow to produce water for the station. A purpose- designed melt-tank is located beneath the walkway, connected to the two life support modules; the tank will be filled with snow by hand or by bulldozer, depending on the weather. Melt water from the tank is stored in tanks in the life support modules; there is sufficient water for four days’ use in summer and 14 days in winter.
The station’s energy footprint This adds significantly to the station’s energy footprint. Accordingly, Halley VI features aerating taps and reduced-flow showers, a water-efficient laundry and a
The £26m station is based on eight linked, highly insulated modules, each mounted on four sturdy, hydraulically-extendable legs to enable the modules to climb out of the snow
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April 2013 CIBSE Journal 29
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