The commissioning of the Oceanlinx wave power plant is on track for December. The 1 MW ‘greenWAVE’ energy converter will be located off Port MacDonnell in South Australia and will be connected to the electricity grid. It will be a big milestone for a company that began in 1997 and has advanced through a range of prototypes since their Wave Energy Plant was installed in Port Kembla in 2006.

It’s interesting to look at some of the numbers in the company’s media release.

At $7 million, the 1 MW unit comes in at $7 per watt. At first glance, that looks expensive. The cost of solar PV in Australia is now down to around $3 per watt, including installation.

But the important figure is cost per kilowatt-hour. Oceanlinx claims that this 1 MW unit can produce enough electricity to match the consumption of 1,000 households. With the average Australian household using around 18 kWh per day, that implies an average generation capacity of 18 MWh per day or 18 watt-hours per watt of rated capacity. That’s pretty impressive, working out at 75% of its theoretical maximum capacity.

How does that compare with solar? My 1.5 kW solar PV system puts out an average of 5.3 kWh per day over the course of a year. Useful as that is, it only amounts to 3.5 watt-hours per watt of rated capacity. So, on this very rough calculation, for 2.3 times the cost per watt, the ‘greenWAVE’ should generate 3.4 times the power, making it around 30% cheaper than solar.

On the other hand, my solar panels are hardly in the sunniest place on the continent and there are vast areas of Australia that can provide 30% more sunshine. But wherever solar panels are located they can never get more than 12 hours of sunshine per day on average, and without tracking, they only receive peak radiation for a short period each day. Waves, on the other hand, wash upon the shore at any time of the day and night.

The other big thing affecting cost comparison is system longevity. Solar panels decline in efficiency over time, but it’s not unreasonable to expect them to remain functional for 40 years. Other parts of solar power systems have shorter lifespans. There is a bigger question mark over the lifespans of wave power systems. Several different wave power technologies are on the brink of deployment, and some will be more robust than others.

It’s early days yet for wave power, and economies of scale should reduce its cost. But on this ‘back of the envelope’ calculation, it looks like there’s a real future in harvesting the power of waves.

Update March 2014: Problems were encountered in towing the Oceanlinx unit to Port MacDonnell. The problem seems to be related to the airbags used to keep the unit afloat during towing. The unit was towed to shallow water about 40 nautical miles south east of Adelaide. Read more.

Image: Oceanlinx, used with permission