Technical and economic prospect of wind energy at Lapaha, Tonga

The wind at 50 m above ground level (a.g.l) was measured for 22 months. The mean wind speed predicted by Wind Atlas Analysis and Application Program (WAsP) at Lapaha was 6.39 m/s and the power density were 279 W/m2. The prevailing wind direction at Lapaha site was East and Southeast direction with a low turbulence. The WAsP wind map indicated that Lapaha has a good wind potential for power production. A wind farm consisting of four Vergnet 275 kW wind turbines at Lapaha site is expected to pay itself back in 9 years with a Benefit to Cost Ratio (BCR) of 1.74, a Levelized Cost of Energy (LCoE) in Tongan Pa’anga (TOP) of 0.10/kWh compared to TOP 0.86/kWh presently charged to domestic consumers. The expected internal rate of return (IRR) would be 50% and with a life time of 25 years. The expected cost saved from the wind farm is TOP 1.3 million per year, which is equivalent to 1.3 million liters of diesel saved, resulting in 535 tons less CO2 emitted annually. The proposed wind farm is expected to decrease diesel consumption by 20% annually.