Technical Sheet 1: Solar Energy and Water Treatment Unit
This technical paper is the first of a series to offer an in-depth focus on some of the technologies used at the Princess Elisabeth station. This first edition will set focus on the station's solar panels and water treatment unit.
The station's interior systems must first be tested and validated in Brussels before they are sent to Antarctica. In light of these results and of technological evolutions, you will be updated as to any changes occurring in the station's active systems.
The Princess Elisabeth Antarctic research station was designed to receive a combination of wind and solar power, two renewable and carbon-neutral technologies for producing electricity. While wind power will be used solely to supply the station with electricity, solar power will provide both electricity (photovoltaic solar panels) and hot water (thermal solar panels).
Solar energy also heats the inside of the station, although not via solar panels. The station will be heated by what is known as passive solar gain, a technique optimized by the building's layout and window arrangement. Passive solar gain has proved to be so efficient that no other heating system is needed to heat the station during the summer months.
Photovoltaic Solar Panels
The idea behind a photovoltaic solar panel is the presence of a semi-conductor (solar cell) that captures and recuperates the sunlight's quanta (photons). The multitude of photovoltaic solar cells that make up each panel convert the photons into a continuous electrical current, which is then transported by means of metal contacts.
The station's photovoltaic solar panels were provided by the technical partner Kyocera Fineceramics GmbH. The German subsidiary of the renowned Japanese ceramics company are providing 408 photovoltaic panels (KC130GHT-2 model). 120 (109.5 m2) will be attached to the walls and roof of the station. The remaining 288 panels (270 m2) will be positioned on top of the station's garages. While most of them are positioned towards the north for maximum sun exposure (Antarctica being located in the southern hemisphere), some panels will also face in other directions to follow the sun's position at different times of day.
Each solar panel can produce a maximum output of 130 Watts, has an efficiency of 16% and a nominal yield of 12 V (maximum around 17 V). These conventional solar panel models measure 150x155 mm and comprise a total of 36 silicon solar cells each.
The solar panels are interconnected in series and in parallel, providing a combined power of 52.72 kWp (up to 800 W/m2 of solar radiation). According to early simulations, they will yield 45.7 MWh/year. This accounts for about one third of the station's total annual electricity production. The station will also receive electricity from nine 6 kWp wind turbines. According to early simulations (based on calculations for 6 wind turbines), they will generate approximately 90 MWh/year, that is about two thirds of the station's total annual electricity production. According to this same study, the station's total annual production should amount to roughly 140 MWh/year.
By means of an intelligent energy management system, the electricity generated by the solar panels and wind turbines is distributed directly to appliances through the electrical grid. Any excess energy is stored in batteries located inside the central core of the station.
Thermal Solar Panels
Princess Elisabeth station will be equipped with 24 m2 of TUBO 12 Compound Parabolic Concentrator panels, developed by the German company CONSOLAR. These specific panels use vacuum tube collectors to absorb sunlight and collect heat. The vacuum within the tubes reduces conducted heat loss and allows the panels to reach much higher temperatures. Most adapted to colder regions, they were chosen for their reliability and high performance rate during the very cold temperatures of the austral winter (a vacuum insulator is a lot more efficient than glass wool, used in plate collectors). This specific model efficiently converts 70% of solar energy into usable thermal energy.
Unlike photovoltaic panels which are lined with a semi-conductor, thermal panels use an absorbing dark surface plate to recuperate the energy and generate heat. A heat-transfer fluid (TYFOCOR LS, an anti-freeze mix that can withstand -28°C) then circulates inside the plate to carry the heat to a boiler filled with cold water.
Particular to CONSOLAR, the closed-loop solar heated water transfers its heat to a static volume of water inside three 560 L tanks, by means of a heat exchanger. Given that these thermal buffer tanks are extremely well insulated, the static water mass can maintain a high temperature for a long time, even when the sun is producing less energy such as, for example, when there are clouds. Finally, another heat exchanger, floating in the upper layer of the tank, carries the heat over to the water going to the various appliances. Whereas the heated water is used in the bathroom, kitchen and washing machines, the actual heat generated by the solar panels is used to melt the snow and to raise the water treatment unit's bioreactors to a given temperature.
Similarly to the photovoltaic panels, the thermal panels are orientated towards the north to make optimal use of sunlight. A first series of solar panels (18 m2), located on the station's roof, will generate heat for the kitchen, bathroom and water treatment unit. The remaining 6 m2 of solar panels, located on top of the garages, will provide enough heat to melt the snow (source of drinking water). The thermal heat is also stored as hot water but, this time, inside a 490 L tank.
Water Treatment Unit
Scientists at the Princess Elisabeth station will be among the first to recycle their used water. Inspired by technology developed for future spaceships (two bioreactors and two filtration units), the station's water treatment unit will recycle 100% of its water and reuse 75% of it! After purification and neutralisation, the recycled water is allocated to a second use, notably showers, toilets and washing machines.
Designed and built by EPAS (Eco Process Assistance), the station's water treatment unit will recycle both grey waters (from showers, sink, dishwasher, etc.) and dark waters (namely from toilets and labs, if not chemically contaminated). Although a similar water treatment design is already used in certain industries, this specific model was developed in order to adapt to the particular constraints of the station: the unit had to be kept small (9 m2) and energy efficient (peak energy consumption < 7 kW).
Located in the center of the main building, the station's water treatment unit uses microorganism digestion to decompose organic matter and chemical treatments to remove non-decomposable components, such as heavy metals.
The entire recycling process can be divided into 6 successive steps:
- black water buffer tank: equipped with a particle grinder, it feeds the black water into the anaerobic bioreactor
- grey water buffer tank: feeds the grey water into the aerobic reactor
The reactor is heated at 55°C (using solar energy). The anaerobic microorganism digestion process breaks down the big molecules into small molecules. This is a necessary stage for the black waters.
Tangential filtration unit
Filters the water after anaerobic treatment and produces a filtrate solution.
The reactor is heated at 25-35°C (using solar energy). The aerobic decomposition removes the remaining solids and organic compounds, and either nitrifies or denitrifies the water. This module is fed both by the grey water buffer tank and by the tangential filtration unit.
Active carbon treatment
This module eliminates all residues of organic compounds and corrects the water's colour.
In-line pH correction
The water's pH-level is corrected by either adding an acid or base substance.
After these various steps of treatment, the water then rests inside a 2300 L tank. A final ultraviolet treatment is added into the tank in order to conserve the water's purity. Theoretically speaking, water can be recycled endlessly. At the Princess Elisabeth station, however, the water is recycled 5 times maximum, depending on the station's occupation rate. 25% of the water used at the station (outside of drinking water) comes from freshly melted snow and is added to the water volume which has been processed in the water treatment unit. This means that each time the water is recycled, 25% of the water's volume has to be disposed of. After treatment, it is evacuated through a crevasse underneath the building.
Picture: Water Treatment Unit of the Princess Elisabeth Station - © International Polar Foundation