By Chris Paterson

16-06-02 The Australian Antarctic Division is attempting the largest renewable energy installation of any nation in Antarctica. Australia has three permanently occupied research stations in Antarctica, and a station on sub-Antarctic Macquarie Island. They provide a modern and comfortable platform for undertaking Antarctic science, but maintaining them in the remote Antarctic environment is resource-intensive.
Although each of the Antarctic stations is located on the coast of continental Antarctica, with the sea frozen for hundreds of kilometres in winter, access to the stations by ship is limited to a couple of months in the Antarctic summer. As a result, each station usually gets a single ship-based resupply each year.

This is the only opportunity for the bulk delivery of the year's supply of food, fuel and building materials. The primary energy source at the stations is a modified diesel fuel referred to locally as Special Antarctic Blend (SAB). Each station presently uses around 600,000 litres of SAB, and while energy reduction programs have reduced this from an annual usage of closer to 800,000 litres, the stations still require an annual visit by the resupply vessel to top up supplies.
The fuel is used primarily to provide heat and electricity to the stations. Electricity is produced in conventional diesel-generating sets. Waste heat from these sets is captured and provides the primary source of building heating. Additional heat is produced by fuel -- fired boilers during the colder periods of the year.
Each station's electrical load is generally in the order of 230-260 kW at any time, while the heat load varies from approximately 240 kW in summer to significantly more in winter. The average energy load is approximately 530 kW.

The Australian Antarctic Division (AAD) has been investigating the potential of renewable energy sources to supplement existing fuel-generated energy supplies since 1993. In 1995, a 10 kW Vergnet turbine was installed at Casey station to investigate the operational aspects of using wind turbines in Antarctica.
By the end of 1996, research had revealed that the suitability of using wind power was greater at some of Australia's stations than others. Mawson station has the most suitable wind profile, with an annual average wind of 11 m/sec.
Macquarie Island's profile is also suitable. Casey has less potential, with a major issue being strong wind gusts of 81 m/sec and long periods of calm weather. Davis has much less wind and limited potential. Further wind resource research was undertaken before feasibility studies commenced for large wind turbines at Mawson and Macquarie Island in 1999. The studies concluded that commercial turbines with minimal modifications should be suitable for the stations. This, however, was only the first step.

One of the issues is to determine the optimum level of renewable energy penetration into the small electrical "grids" at the Antarctic stations. In financial terms, the high delivered cost of diesel orSAB indicates that the financial payback is proportional to the amount of renewable energy generated.
However, this is only the case when renewable energy contributes up to approximately 40 % of the load. After this point and up to approximately 80 % penetration, wind profiles usually require some form of expensive energy storage to augment wind power when the wind is less than optimal. If we wanted renewable energy to provide 100 % of the load, a massive amount of storage would be required, such as large battery banks.
In addition, the use of wind generators beyond a 40 % penetration generally requires some form of frequency control on the grid. Another issue for the establishment of wind generators at an Antarctic station is the size of the turbines themselves. A large number of small turbines will provide an amount of system redundancy, but could also provide a maintenance issue with a large number of machines to be maintained in a remote environment.

A related issue is the relatively small amount of available space at the stations. Antarctic stations are built on small areas where the rocky coast protrudes from the Antarctic ice cap. In any case, increasing the footprint of the station is undesirable.
A smaller number of large turbines would be a more elegant solution in terms of maintenance issues, but significant logistical issues can be encountered depending upon the size of the turbine. These include safely getting the equipment across the Southern Ocean, off the vessel and to the erection site at the station. There is also the problem of erecting turbines without the usual construction equipment being available on site. An initial risk assessment revealed a number of factors that need to be considered.

-- Transport:
Larger turbines can have components up to 15 metres in length weighing up to 13 tons. This has implications for the normal resupply operations at the station.
-- Siting:
Turbine life and output can be reduced by turbulence generated by other turbines or land features.
-- Foundation design:
The high winds, cold temperatures and possible permafrost ground conditions make the foundation design a critical aspect of the project. Large concrete structures require a high level of quality control during their construction in Antarctica.
-- Erection methodology:
Conventional turbine towers require cranes with a load capacity in excess of 100 tons. Alternative methods such as tilt-up tower designs and self-erecting towers were investigated.
-- Training of maintenance staff:
Specialised maintenance of turbines will require station staff to undergo training each year.
-- Radio frequency interference:
Large variable speed turbines use complex switching electronics to maintain fixed voltage and frequency output to the load. It is a requirement that these electronic systems must not interfere with the other scientific equipment at the stations.
-- Static electricity:
The extremely dry atmosphere and dry, blowing drift snow produces staticthat builds up on cables and structures, particularly at Mawson station. This will be an issue for turbines, their blades and cables. Sound earthing practices have been incorporated at the system design stage.
-- Wildlife:
It is believed that the chance of bird-strikes is greatly reduced if the turbine towers are not guyed, and if the turbines are mounted as high as possible and are slow-revving. Most modem large-scale turbines fit this profile.
-- Temperature:
The constant low temperatures in Antarctica can lead to costly problems with gearbox oils and oil seals. Turbines without gearboxes are therefore preferred. Metal fatigue on structures can also be an issue.
-- Icing:
The icing of blades, furling mechanisms and monitoring equipment can be a problem at sites where on-shore wind-blown wet snow or rain occurs. This becomes a siting issue, although most modem turbines are available with blade heating.
-- Wind abrasion:
"Sandblasting" of the turbine blades can occur at sites where the prevailing wind is from an ice-free area. This may also be an issue with Antarctica's very dry snow, although to a lesser extent.
-- Fatigue:
Metal fatigue due to cyclic loading and constant high winds is a major issue that could shorten the design life of the turbines. These issues are compounded by Antarctica's cold temperatures.
-- Snow ingress:
The fine dry drift snow has a habit of getting into everything. A system of turbine tower ventilation that keeps out this snow is being considered.

Taking into account these potential challenges, a worldwide search was undertaken to determine the suitability of the commercially available turbines for use at Mawson station.
The criteria for the turbines were:
-- output in the 100-230 kW range;
-- ability to withstand the strongest wind gusts of 70 m/sec;
-- a mature design with low maintenance requirements and a high level of reliability;
-- a design that was suitable to the cold climate; and
-- a design that we could get to Antarctica and erect with existing systems or equipment.

One of the turbine options available on the world market was a 230 kW machine built by German manufacturer Enercon. The E-30 was the right output, and a Darwin-based company named Powercorp was in the process of installing three E-30s to power the township of Denham in Western Australia. The turbines appeared to meet all the criteria, and initial contact with both Powercorp and Enercon were positive.
Initial discussions with Powercorp indicated that, due to the physical risks associated with the project, the contract would be prohibitively expensive if the contractor was required to carry that risk. Given the significant engineering that was required, the unpredictable nature of the Antarctic environment and the reliance of the contractor on AAD logistics, a partnering agreement was signed to allow the design and development work to proceed, the production of project estimates and a business case. This led to the eventual approval for the project to proceed.

Design work is now completed for a new cold climate E-30, and the initial prototype has been erected in Germany. The Mawson machines will be on 33 metre towers, reduced from the standard height of 50 metres due to the strong Antarctic winds. It is expected that turbine blade diameter will be reduced from 30 metres to 27 metres, and that the machine when delivered will be rated to 300 kW rather than the standard 230 kW.
With continued effort by all the parties, it is anticipated that Antarctica's first large-scale renewable energy generators will be commissioned next summer. This will signify a new era in Australia's Antarctic program, and will showcase the management of renewable energy technology in the Antarctic environment.
It will provide a catalyst to the development of a number of cold climate systems within the renewable energy industry and will, in a small way, assist in protecting the global environment.

Chris Paterson is Chief Engineer at the Australian Antarctic Division.