This page describes the available wave energy available in Tongatapu and 'Eua.
The regional analysis of the cost of wave energy (See here) concluded that Tongatapu and ‘Eua could be suitable to support wave energy converters. Wave energy is larger on the South Coasts of Tongatapu (See image below) and previous study have identified the South Coast of Tongatapu as suitable to host a Oscilating water column device. This page expands the regional wave energy analysis to the whole of Tongatapu and ‘Eua to identify suitable offshore wave energy conversion hotspots.
Tongatapu has a bathymetry would allow the installation any type of wave energy converters. Wave energy converters can be divided in these three categories: Offshore, Nearshore and onshore devices.
Onshore devices are built and fixed on land. The location may be on the coastline or integrated into structures such as breakwaters. Adjacent depths are typically less than 15m. These devices are best suited where the shoreline is located on a rock platform with steep bathymetry. These geological features are present on the South Coast of Tongatapu.
Nearshore devices are predominantly fixed on the seabed. They capture wave energy nearshore and convert it to electricity in an onshore facility. Depths are typically less than 25m. These devices generally require a near horizontal (or gently sloping) bathymetry. This type of devices could be used in only a limited case in Tongatapu.
Offshore devices are moored to the seabed and transfer the generated electricity using sub-sea cables laid on the seabed. Typical depth are more than 25m but less than 200m as deploying a mooring system in greater depth becomes challenging (and costly). These devices are exposed to larger waves and often more cost effective.
Wave energy converters come with different cost and efficiency. The cost of operation and maintenance and on the environment can also vary greatly and it can be very hard to decide whether Tongatapu would benefit more from one type of device at a location or another device elsewhere. It is impossible to compare the cost and efficiency of all the wave energy converters because they are not all at the same stage of development. For example, some devices only have a theoretical efficiency while other more advance wave energy converters have a measured (i.e. verified) efficiency. In order to help with decision on what device would be more suitable for Tongatapu, we calculate the cost of energy generation of one wave energy converter, the Pelamis.
From the many wave energy devices developed globally, the Pelamis wave energy converter is one of only two to have reached commercial readiness. Although Pelamis Wave Power Ltd, the firm behind the device, went into administration at the time of writing this report, the milestones reached and the research behind the Pelamis device are unprecedented and unmatched by any other device. Because of the large amount of literature on the Pelamis, it is still a benchmark and, although it is unlikely that more Pelamis devices will ever be built (at least under the same name), the device’s physical characteristics and cost evaluation can be used to probe the economic feasibility of wave energy.
|Cost Type||Cost range|
|Operation and Maintenance||US$ 1.72 - 8.48 million|
|Total||US$ 6.32 - 14.10 million|
|Site name||Mean available wave power (kW/m)||Annual Pelamis power output (MWh)||OM cost range (USD/MWh)||Total cost range (USD/MWh)|
|Kalau Is.||32.7||1007||68 - 337||251 - 560|
|Tonga WB1||26.8||744||930 - 4583||339 - 758|
|Duff Reef||26.4||630||109 - 538||401 - 895|
|Euaiki Reef||24.4||730||94 - 465||346 - 772|
|Tonga WB2||23.1||593||116 - 572||426 - 951|
|Houma Toloa||21.9||566||122 - 600||447 - 997|
|Hufangalupe||17.9||341||202 - 995||741 - 1655|
|Montapu Beach||17.8||393||175 - 863||643 - 1436|
|Mui_Hopohopoponga Point||16.2||401||172 - 846||630 - 1407|
|Finehika Beach||13.4||301||229 - 1127||840 - 1876|