Picture by moonlightbulb on Flickr

After many years of research and development it seems Ocean Thermal Energy Conversion (OTEC) may be ready to begin its contribution to zero-emissions renewable power. OTEC technology has particular promise in remote island communities such as the Philippines, where Bell Pirie Power Corp. is planning the Zambales Energy Island project, a 10MW demonstration unit around 10km offshore from Luzon and 120km north of Manila.

Independent research by the Saga University, Japan and Oceanographic Co. of Norway have identified the potential for around 170,000 MW of clean renewable ocean energy in the Philippines. 22 sites have been tagged for further investigation, but OTEC has been languishing in a long research phase for many years with only a few operating test facilities and no commercial deployment. Now a 16 MW offshore OTEC plant based in Martinique has been awarded funding by the European Investment Bank under the NER300 renewable energy programme. The funding guarantees operation of the facility for its first 5 years, paving the way for large-scale demonstration of the technology and production of crucial performance figures that can be used to unlock commercial finance for OTEC facilities around the world.

The Martinique ‘NEMO’ project follows successful demonstration of on-shore OTEC technology developed by France-based naval defence company DCNS at Réunion University (Saint-Pierre).

Ocean Thermal Energy Conversion (OTEC)

OTEC technologies exploit the temperature difference between warm surface seawater and the much colder deep sea water. Electricity can be produced by an OTEC process by passing a working fluid produced from warmer surface water (heat source) to the cold deep water (heat sink) through a turbine/generator system. The working fluid may be steam/vapour (open cycle) or a refrigerant such as Ammonia (closed cycle). Fluids such as Ammonia boil at temperatures equivalent to tropical surface water and can then be condensed using cold deep-sea water creating a continuous cycle suitable for power production.

The OTEC principle has been around since 1929, but development has been slow due to the complexities of operating in a seawater environment and the costs associated with raising large volumes of deep seawater to the surface. A research facility has been operating at the Natural Energy Laboratory of Hawaii (NELHA) since 1974, and in 2013 Saga University opened a pilot facility in Okinawa, Japan.

Hydropower and Marine Energy

OTEC is not the only option for harvesting the vast ocean energy resources. Other forms of ocean energy include tidal barrages and underwater turbines. Canadian company Blue Energy are planning one such array of turbines in a 4km-long ‘Tidal Fence’ in the San Bernardino Strait. While the project is currently on hold pending local government approval it is rated at over 2GW.

Hydropower is well established in the Philippines, with over 10% of current generating capacity from hydro sources, including large-scale, mini, and micro-hydro facilities. The PNOC Renewables Corp. has recently signed an agreement with the Philippines Department of Trade and Industry to construct a 1MW mini-hydropower plant at Nueva Ecija north of Manila. Microhydropower is an important small-scale alternative that can help to power off-grid sites such as remote villages and farms. The Alliance for Mindanao Off-Grid Renewable Energy (AMORE) has helped to bring clean, renewable power to over 13,000 households in the Mindanao region by helping to deploy micro-hydro systems. Small suppliers like Australian-based Water Recycle Group have supplied equipment around the Pacific to enable remote communities to become independent of grid power and expensive diesel supplies.

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