Technical Sheet 2: Passive Building

The volumetry and geometry of the station's windows (made up of two double-glazed glass windows separated by an air-vacuum of 40 cm) allow the station to benefit from both solar passive and active gain.

Insulation

The station's thermal insulation allows minimal heat loss through the station's walls. Each of the 160 C-shaped side panels composing the walls of the station are made up of 8 consecutive layers, totalling 60 cm in thickness. Their weight varies between 600 and 800 kg. The insulation layer itself, lightweight expanded polystyrene, is 40 cm thick.

The wall and roof of the envelope, from inside to outside are comprised of:

• a wall covering in woollen felt;
• a layer of heavy-duty Kraft paper with a thick continuous aluminium vapour barrier;
• 74mm-thick multiplex wooden panelling;
• 400mm lightweight expanded polystyrene blocks;
• 42mm-thick multiplex wooden panelling (linked to the lower board by means of 6cm diameter cylindrical beech wood posts, fitting precisely in cylindrical holes in the polystyrene);
• a 2mm EPDM (Ethylene Propylene Diene Monomer) waterproofing membrane;
• a 4mm closed-cell polystyrene foam mat between the stainless steel bands located under the joints of the final cover consisting of bolted 1.5mm-thick stainless steel plates;
• a 1.5mm layer of stainless steel.

The floor, from inside outwards, is composed nearly in the same manner as the roof and walls. The sequence of the floor layers is the same as that of the walls' inner envelope layers.

Inside the station's insulation layers outlined here above is a waterproof material, EPDM, which is a synthetic rubber lining membrane preventing any air leaks. This lining is very important because it will shield the inside wood from the outside environment. Any intruding snowdrift could lead to unwanted humidity, which could damage the structure.

Ventilation

By creating an air-tight building, stale air would normally not be able to escape. A sophisticated ventilation system is therefore needed to maintain adequate inside air quality levels.

The Princess Elisabeth station will be equipped with 3 "Resolair" model ventilation units, provided by Menerga: 2 will service the inside living

The ventilation system works on two fronts:

• it transports both stale and fresh air using ducts, outlets and fire dampers;
• it ventilates the rooms using the energy recovery system, ventilators and a regulation device.

When retrieving and restoring the extracted air's energy, the station's ventilation system recovers both temperature and humidity. Maintaining the right humidity level provides comfort to the people living in the station. In a dry climate like that of Antarctica, this is absolutely essential. Most of the station's electronic units (within the station control unit) are unable to survive the winter season with relative humidity levels under 15%. Moreover, humidity recovery is important to provide enough water for the humidifiers throughout the winter.

Developed to allow for both humidity and temperature regeneration, Menerga's Resolair ventilation system can be broken down into several sub-units:

• Two accumulators: they are alternatively filled and evacuated with the outgoing and incoming air flows, each at a different temperature and humidity (outgoing stale air is warm and relatively humid; incoming fresh air is cold and dry); within 40 seconds, the accumulators are completely filled / evacuated. This allows the heat from the outgoing warm air flow to be very rapidly removed and equally as rapidly injected into a cold fresh air stream.
• Inner damper system: 2 dampers are situated between the accumulators and the fans; they are controlled by fast-paced electric motors. Within a second and at intervals of approximately one minute, the airflow direction through the accumulators is changed, thus also altering the fill / evacuate phase of the accumulators.
• Servo-motors: electric motors that can react very quickly (start and stop). Whereas servo-motors used for dampers normally present an open-to-close time of roughly 80 seconds, these do the job within a single second. This means that the controlling device must also be quick enough to react within 10 milliseconds.
• Outer damper system: 2 dampers are situated on the fresh / exhaust air side of the accumulators; they operate dynamically and have no motor drive because they respond to the airflow direction change.
• VAVs (Variable Air Volume) boxes: foreseen on the supply ductwork and located within the ducts which transit to and from the different zones in the polar station, they control the fresh airflow rate according to CO₂ and temperature conditions in these zones (prevent overheating caused by occupancy and internal loads).
• Fans: controlled to produce a constant (in and outflow) duct pressure.
• Regulation device: a redundant Programmable Logic Controller (PLC) from Schneider Electric, controls the complete electric equipment of the polar station. Composed of +/- 1500 signals for the entire station (+/- 250 for the ventilation system), each input and output (to which sensors and activators are connected) on the PLC is doubled in case any becomes defective.
• SCADA system (Supervisory, Control And Data Acquisition): allows all parameters, measurements and status to be visualised on a user friendly Human Machine Interface (HMI), an electronic screen displaying text, graphs and values.
• Humidifiers: water from the Melted Water Unit is vaporised by the humidifiers and injected into the supply air; the quantity of vapour is regulated by the PLC, in order to have correct humidity levels in each zone.

The precisely designed accumulators and damper motors and the precise timing of the redundant PLC allow the system to reach high efficiency rates: over 90% temperature efficiency and 70% of humidity recovery.

Everything in the Resolair ventilation system was designed and controlled to keep energy consumption as low as possible in order to meet the station's low energy requirements. For example, the units were designed to be oversized in order to keep the pressure gradient at its lowest. Furthermore, in order to reduce the fans' energy use, the engineers have decided to omit any air filters in the system, as Antarctica's air is naturally very clean. Unlike other energy recovery systems, the Resolair system also presents the advantage of not needing to be defrosted. Defrosting requires lots of energy and adds a heavy load onto the local electricity grid of the station.