The Pacific Islands Renewable Energy Project (PIREP) has assessed the potential for renewable energy technologies in the country, and determined the following options: Biomass energyAlthough around 65% of the land area is forested for crop production (mostly coconuts), for the near term, there is little opportunity for biomass from forest products to be a significant energy resource. Timber milling is a small scale industry, with mostly senile coconut trees used as raw materials. Pine and hardwoods for export are being planted, but it will take many years until they can be harvested. However, after harvesting, there may be sufficient mill waste to provide biomass for energy. In general, agricultural and forest residues are not considered an exploitable resource for energy production.Biofuels In 1995, potential copra production was estimated to be sufficient to produce around 10 million litres (ML) of coconut oil per year. If rehabilitation efforts for the coconut industry are carried out, and if barriers to the production of biofuels can be eliminated, the maximum offset of diesel fuel by biofuel could be as high as 50%.BiogasAlthough there has been no assessment of the resource, sewage, urban waste and animal manure represent a useful resource. However, the potential is not considered sufficient to offset a significant percentage of petroleum imports, and no projects have been proposed as of yet. Should new sewage treatment facilities or landfill facilities be developed, including biogas generation, they could provide enough energy to operate the facilities themselves, with some surplus to feed into the national grid.Solar energySolar energy resources have a high potential in Tonga, particularly towards the north, where satellite measurements indicate average insolations of up to 5.8 kWh/m2/day. Nearly 20 years of solar powered rural electrification experience confirms that there is a viable resource. Plans are included in the country’s 2010 Energy Road Map to develop a comprehensive renewable resource assessment, including solar resources. A 2008 SOPAC study reported that there are 169 solar PV stand-alone systems in 6 islands in Tonga. Each of these systems has a capacity of 60 W.Wind energyA resource assessment carried out in Tongatapu in 1995 indicated that there is potential to develop wind energy in Tonga. However, due to turbulence issues, locating the turbines away from tall coconut trees will be necessary. Consideration should be given to locating turbines off-shore or in open swamp areas, to avoid turbulence from nearby trees, as well as avoiding land use issues. Average wind speeds for the islands vary between 3 and 6 m/s, with highest averages seen from May to October, and peaks of up to 8 m/s in coastal areas. Geothermal energyThere is a strong evidence of geothermal sources, however, there has not yet been a geothermal energy study for Tonga.HydropowerTonga does not currently utilise hydropower, nor is there any recognised potential for small- or large-scale hydro-electric power generation in the country, primarily due to the topography of the nation.There are sites in Vava’u which could provide tidal energy; however, it is unlikely that the cost of installation can be justified, and the potential resource has not been assessed. In addition, the potential has been recognised for utilising Ocean Thermal Energy Conversion (OTEC). Due to the relatively experimental status of this technology, it is unlikely that developments will occur in the near future.