Science Centres: Energy

Wave energy device hits the water

The proof-of-concept device (one-quarter size) hanging upside down. (Photo: Robert Stuart, IRL)

Wave energy device upright in the water during Lyttelton sea trials. (Photo: Robert Stuart, IRL)

A proof-of-concept wave energy device developed by WET-NZ has been undergoing sea trials in Lyttelton Harbour.

WET-NZ (Wave Energy Technology-NZ) is a collaboration between Industrial Research Ltd, NIWA, and Power Projects Ltd, and the research is funded by the Foundation for Research, Science & Technology.

The team has produced a unique design, for which patent is pending. This involves a small, streamlined device which pivots at the surface. Power is generated by the device’s rotation at the pivot point, between the main spar (below water) and the float. For ease of transport, the float locks in place so the device can be towed flat like a speedboat. To deploy, the float is unlocked so it can flex, and the ballast tanks are emptied so the spar tips into vertical position.

The proof-of-concept device is a one-quarter scale model, and has performed well in the four sea trials to date. The trials are a staged process, says NIWA marine physicist Dr Craig Stevens. "We’re running a sequenced research programme, where we test how the device responds then introduce a new element or planned modification."

So far, modifications include:

• upgrade of the device cladding, including painting in the international standard yellow
• encasing the measurement and telemetry modules
• installation of an adjustable floatation mechanism
• installation of two drive mechanisms
• changes to the electronics and control circuitry

Next steps

In the Lyttelton sea trials the device has either been free floating or tethered by a single line. Next, the device will be moved to Wellington so NIWA can begin a series of mooring trials.

In addition, Industrial Research will build a full-scale prototype, required to test the complete electro-mechanical componentry.

Northland a good prospect

Meanwhile, NIWA’s Wave Buoy has been monitoring conditions off the Northland coast for over a year. The conditions have proved very similar to that indicated by NIWA’s wave hindcast – computer modelling based on satellite observations. The waves are generally of moderate energy, reasonably consistent, but on some occasions can get up to 8 metres. This tells us that waves off this coastline (out of sight from land) would be a good prospect for marine energy, whether it be to service remote communities in Northland or metropolitan areas around Manukau.

The buoy is likely to redeployed in coming months to monitor wave conditions in another part of the country.

More information: www.wavenergy.co.nz