A look at the Mawson station wind turbines, and poor weather prevents the midwinter swim.

The Mawson station wind turbines

One of the first things that immediately captures the eye when arriving at Mawson station are the two Enercon E-30 turbines that make up the skyline.

Each turbine is capable of producing 300 kW of power. They were installed in 2003 and now make a significant contribution to the station’s power requirements.

Due to the changing sea ice conditions around Mawson station, this year the Aurora Australis was unable to reach Horseshoe Harbour to deliver the full 450 000 litres of fuel required to run Mawson station for the year. This forced the AAD to fly in a limited amount of fuel to see us through our season, which means there will be a greater reliance than ever on these machines to provide station power and conserve the fuel for the year ahead.

Since installation the wind turbines have produced a combined 17 010 megawatt hours of electricity, saving the AAD approximately 5 million litres in diesel, making it one of the most environmentally friendly bases on the continent.

The Mawson wind turbine system ranks among the world’s most innovative and is capable of providing 600 kW of renewable power. The AAD worked closely with German turbine manufacturer Enercon and the Australian company PowerCorp to install these turbines and the associated computerised powerhouse control system. It is a design that was so successful that it was selected for the Ross Island wind farm installation of Scott base and McMurdo Station when they were looking for wind power alternatives in 2008.

The Enercon E-30 turbine is a variable speed, 300 kW machine without gearboxes, mounted on a steel tower 30 m above the ground. The PowerCorp station management system (SMS) controller is vital to the efficient operation of the Mawson wind farm and optimises the instantaneous wind resource and diesel generator outputs to that of the station load.

One diesel generator is required to run at all times to aid the frequency control and provide “spinning reserve” if there is a sudden lull in the wind. In addition to this control, Mawson station makes use of a boiler grid interface (BGI) where the electric boiler power electronics acts as a regulator to absorb the power fluctuations common on small wind turbine grids. This is a system unique to Mawson station.

Another common term when assessing the effectiveness of a wind farm is “wind penetration” (the ratio of wind-provided power to diesel power), which is usually between 55–60% for the year at Mawson station and has the ability to save in excess of 200 000 litres of diesel in that time. It is the goal of the current Mawson engineering team to make this percentage as high as possible for this season. We hope to achieve this through a mixture of Kingston-introduced power saving initiatives, running tighter power controls and responding to turbine breakdowns in the quickest possible manner.

Since we have been at station we have recorded wind penetration of 81%, 62% and 57% for the months of April, May and June respectively. This highlights the need for the correct wind conditions for optimal performance, because while the wind turbines have a reduced capacity at low winds they also ramp down power output in higher wind conditions, having an optimum working range between 16–25 m per second. These are conditions that have been eluding us for the last two months but we wait and hope for better conditions (and fuel savings) in the months to come.

Aidan Heather — Electrician and proud Kiwi

Why we didn’t swim at midwinter

Those of you who read our midwinter wrap up in last week’s newsletter might have noticed one omission from the usual line up of midwinter activities. There was no mention of the midwinter swim. This is because, due to poor weather, we have not yet had a chance to take a dip here at Mawson. On midwinter day, and the days leading up to it, we experienced gale strength winds. On the day itself we recorded wind gusts of 111 km/h. Not great swimming weather at all. As a consolation we did have the station’s energy saving regime relaxed so we could run the station spa for the first time since we arrived, so those who wanted to have a dip had one in the comfort of a heated tub as opposed to jumping in the freezing sea.

Immediately following midwinter day we had four days of blizzard conditions with wind gusts recorded at 183 km/h. The blizzard kept the trades team very busy, with these types of conditions putting many of the systems required to run the station under considerable pressure. As with most blizzards we also had plenty of snow and ice getting into various buildings around station, requiring much shovel and spade work to get cleared out. During this blizzard we also had some pretty impressive bliz build up inside one of the Hägglunds (tracked vehicle).

While on the topic of shovels, it is worth mentioning the digging of our swimming hole in the sea ice the weekend before midwinter. The hole was made well in advance so it would just be a quick job of clearing the relatively thin ice that had formed on the surface when we wanted to use it for the swim. A site just in front of the wharf was selected for the swimming hole. The first step in the process was drilling the ice to measure the thickness — 1.3 m in this case. Next the diesos used chainsaws to cut neat edges for the hole and also to cut the ice to be removed into smaller squares. The excavator was then used to dig out the hole. When the bucket on the excavator could dig no further it was swapped for a ripper attachment. This was used to punch through the remaining ice at the bottom of the hole. When the sea ice was breached a lot of water came out of the hole, flooding much of the shore in front of the station. At the time it was speculated that this might have been caused by a high tide, seeing that the ice that the hole had been made in is attached to the land and not floating like the rest of the sea ice. A look at the tide chart showed that at almost exactly the time that the hole was being finished we were predicted to experience the highest tide that we were going to get for the rest of the year. I guess that the tides in Horseshoe Harbour have not really been in the forefront of our minds seeing as its surface has been frozen solid since our arrival at Mawson. It is a shame that we didn’t manage to get our swim to happen. Since the blizzard at midwinter there is no longer any evidence of the hole on the surface as the area has been covered in snow.

Despite the poor weather around midwinter, Mawson station still had quite good weather for the month of June. During the first couple of weeks of the month we had hardly any wind, with an average wind speed for those weeks of only 23 km/h. The strong winds later in the month meant that by the end of June we ended up almost matching the long term averages for wind at this time of year. Temperatures during June were slightly lower than the long term average. The mean daily maximum temperature for the month was −15°C and the mean daily minimum temperature was −22°C. The coldest temperature recorded at Mawson during June was −30°C.