Technical Sheet 3: The Princess Elisabeth Station’s Electrical System

Initial energy consumption analyses and design specifications were conducted by 3E, an international expert company in all domains of renewable energy and energy efficiency. Laborelec, a subsidiary of GDF Suez, designed an innovative energy management concept for the station based on technologies easily available in the marketplace, and gave advice on the electromagnetic compatibility (EMC) design of the station. Schneider Electric and SMA are providing the electrical equipment that will be used in the station. In particular Schneider Electric is providing a Programmable Logic Circuit (PLC), which will act as the "brain" of the station's electrical system, and a Supervisory, Control and Data Acquisition (SCADA) System, which will allow for human interface with the station's electrical system.

As a first-of-its-kind prototype, it is the design of the station's electrical system which makes it unique. The main control room for the electrical systems will be located in the core of the building, and all systems in the station will have a reliable energy supply designed to be affected as little as possible by any disruptions, whether internal or external.

Advanced Power Management System (APMS)

Energy management of the station will consist of maintaining the equilibrium of the entire network between the energy produced and the energy used in the station. Efficient use of the energy produced by the solar photovoltaic panels and the wind turbines is monitored and controlled using a smart grid system run on Laborelec's Demand Power Management System (DPMS).

The Demand Power Management System's logic circuits are located inside the Modicon Quantum NOE programmable logic controller (PLC), provided by Schneider Electric. The PLC will act as the central brain of the station, monitoring both the production and consumption of energy, while simultaneously regulating the processes of every system in the building.

The Power Management System is envisioned to consist of 200 circuits with a number of different operational modes and different levels of priority for each mode. Approximately 30,000 variables with 150 parameters per circuit are calculated using the energy management algorithm programmed into the PLC, which uses Unity software. Based on the priorities in energy usage determined by this algorithm, the PLC will know how to regulate and prioritise electricity distribution within the station.

While the exact orders of priority of systems within the station will be determined on-site by the specific needs of the moment, first priority will always go to systems linked to human safety, water production and ventilation. In general, other systems such as those that regulate temperature and humidity or control the opening and closing of doors will get secondary priority, and devices that maintain scientific samples and guarantee that scientific data does not get lost and kitchen and bathroom appliances will get tertiary priority. Lowest priority will go to non-essential devices such as laptops or DVD players.

The PLC will be programmed to know at which times peak energy use will be required in certain areas, so that, for example, it will give higher priority to the kitchen around meal times than at other times of the day. There will also be specific pre-programmed energy use modes, including a night mode, an emergency mode, a low energy mode, a general emergency mode, a fire mode, and others that will be determined based on the needs of the station's occupants.

The system is designed so that if a user wishes to use electricity at a given outlet, the user will need to push a button to ask to have electrical power routed to the outlet. The PLC will then perform calculations to see if there is enough energy available. If there is enough, it will give power to the outlet; if there is not, it will indicate that other systems have priority at the moment.

A secondary back-up PLC will be installed to guarantee continuity in case something should happen to the primary PLC.

Eventually, the plan is to have a satellite link system hooked up to the PLC so that the station's systems can be monitored online and adjusted remotely.

Human interface

Human interface with the station's systems will take place via a SCADA system (Supervisory, Control and Data Acquisition). This is the same kind of system used for human interface with mechanised industrial processes in factories - only this one is being used to run all the systems in a living space, not a factory.

The SCADA system uses a Vijeo Citect software package, which allows parameters, energy measurements and the status of the electrical system to be visualised in the form of text, graphs, or other means on a user-friendly Human Machine Interface (HMI) with an electronic display screen. The system will be linked to and in constant communication with the PLC via a server. This server is combined with an industrial PC that will be placed in the technical core, directly into the PLC board.

The SCADA's role is to:

• Guarantee communication between the command control and setting the parameters for different techniques.
• Archive measurements, processes, and system status in a database as well as generate reports.

Local monitoring and control

Local control will be assured by other devices and systems provided by Schneider Electric:

• Energy monitoring of devices will be assured by a PowerLogic system (including TeSys controllers), which will take measurements and communicate them to the PLC.
• In several different parts of the station there will also be Magelis XBTG graphic terminals, which will control some devices within a zone or by technique.
• TeSys D motor starters will be used to control pumps, motors, mixers, and other motorised equipment.
• Five Altivar ATV-31H055N4 frequency inverters will control and vary the speed of the electric motors controlling the water circulation pumps in the station, making it possible to start up loads with large inertia, or large loads on a limited-power network.

Electrical distribution grid

A low-voltage electrical distribution grid equipped with Compact NS Multi 9 circuit breakers and C60 and C60SI modular equipment is to be installed in the station. Twenty Sarel Spacial 6000 switchboards will be used, which will allow the space of the electrical materials used in the switchboards to be arranged for optimal usage of space.

The distribution grid will protect cables against overloads and short circuits in the final distribution of electricity throughout the station. Every system in the station will have its own switchboard, and the PLC will have a special switchboard with special joints to protect against electromagnetic interference that could hinder its functioning and that of all other electronic devices.

Producing three-phase alternating current from Renewable energy sources

Alternating current generated by the wind turbines will be rectified into direct current via rectifiers, and then subsequently inverted back into alternating current using inverters (nicknamed "windy boys"). Direct current generated by the solar photovoltaic panels will be inverted into alternating current via inverters (nicknamed "sunny boys") grouped into sets of three in order to create three-phase AC power. All inverters will be able to communicate with each other so that the same voltage (230 V) and frequency (50 Hz) of AC will be maintained throughout the station.

The battery grid

In order to store energy and help regulate energy usage and stabilise the electrical grid, four double, valve-regulated lead acid (VRLA) OpZv 1000 battery packs manufactured by Hoppecke will be used in the station. Each battery pack will have 24 battery unit elements with an electric potential of approximately 2 V each (at 20°C). With the electrolyte fixed in gel, the battery pack can be used horizontally (most batteries can only be used vertically), allowing for the optimisation of available space in the station.

Each battery pack weighs 82 kg, measures 710 x 235 x 710 mm, has an electric potential of 48 V, an electric charge capacity of approximately 2000 Ah, and a C/10 rating. Comprised of four battery packs, the battery grid will have a total electric capacity of about 8000Ah.

Hooked up to each battery pack will be one cluster of three "sunny islands" as they are called, which are special inverters commonly used in homes in which solar photovoltaic panels are used as a supplemental source of electricity. With four clusters of battery packs in the station, this means that there will be a total of 12 sunny islands producing 5kW each. The sunny island inverters will control and stabilise the three-phase AC system.

The battery grid will be charged and discharged as energy is produced and needed, not exceeding a maximum of 80% of its capacity and not falling below 20%. The "sunny island" inverters connected to the batteries will be cycling all the time between charging the batteries and loading energy onto the grid. The batteries will remain "floating," which means that once they have been completely charged, they will be kept that way by charging them continuously with small amounts of voltage and current.

Evacuation of surplus energy

If the batteries are fully charged and excess energy is still being produced, the surplus must be evacuated; otherwise it can damage the electrical systems. This can be done by either diverting it to particular systems or by "braking" the energy production by raising the frequency of the alternating current on the station's grid up to 52Hz.

During the summer, when the station is in use, surplus energy will generally be transferred to systems that can put the energy to good use, such as the snow melters, or the weather monitoring equipment in small shelters outside the station.

During the winter months, excess energy will be evacuated via dump loads, which will heat the part of the station where the technical core is located. This, along with specially insulated panels that will be placed around the rooms containing the technical core of the station each time the crews prepare the station for overwintering, will help keep the ambient temperature in the rooms where the technical core is located at an ideal temperature for the proper functioning of the technical systems.

Back-up energy system

In case of an emergency, there will also be two 44 kVA Genset diesel-powered generators, located in the northern part of the garage.

Wiring & EMC

Schneider Electric is providing the wiring system, electrical sockets, Internet sockets, cable racks for the station. The station's wiring system will be mounted along the walls of the station in order to make easy access for inspection and repair possible.

The cable racks will be made of steel rather than plastic. Steel can not only stand up to the harsh Antarctic climate better than plastic, but it allows for electromagnetic compatibility (EMC) of all equipment in the station.

With no way to ground any electrical devices in the station (the station is built on granite and ice - both very good electrical insulators) and with the Antarctic climate so dry, static charge on the order of several kilovolts can build up on surfaces. Thus, in order to maintain everything at the same electric potential, Laborelec has designed a strategy so that everything metal in the station will need to be interconnected, and using steel cable racks to protect the wiring will allow for this. It also means any equipment and personnel entering or exiting the station will need to be either charged or discharged accordingly.

Energy-efficient appliances

In order to reduce the energy consumption to the bare minimum, household equipment was selected on the basis of its energy efficiency, such as A++ grade energy saving refrigerators and freezers, induction cookers, energy efficient light bulbs, and so on.