Taiwan’s environment ministry has once again delayed approval of a proposed ocean thermal energy plant, saying developers must provide more data on potential impacts of pumping water from deep offshore before the pioneering project can move ahead.
The project at the Heping coal-fired power plant on the island’s east coast – the first attempt in Taiwan to use ocean thermal energy conversion (OTEC) – would draw cold water from about 600 metres under the Pacific to generate electricity by exploiting the temperature difference between warm surface water and deep ocean water.
OTEC works by using warm surface seawater to vaporise a working fluid such as ammonia, which drives a turbine, then condensing it again with cold deep seawater, a cycle that can deliver continuous, low carbon baseload power if conditions allow.
But regulators have repeatedly flagged deep-sea ecology and data gaps as major concerns. At a second environmental review last week, members of the environmental impact assessment (EIA) panel pressed Taiwan Cement Corporation (TCC), the developer, to explain the need to draw such cold water and how it would monitor and mitigate impacts on deep-sea ecosystems before the project is reconsidered.
“We hope it will not need to be so deep,” one EIA panel member said during the review, echoing concerns that the lack of scientific knowledge about deep ocean currents, biological communities and geological stability makes it hard to assess potential harm.
The intake pipe – planned about 1.6 kilometres offshore – would pull up to 820,000 tonnes of 7°C water per day from 600 metres below the surface.
The project has been repeatedly delayed. In July, an earlier review similarly concluded that existing ecological surveys, particularly of the deep ocean, were insufficient, sending the plans back for more data. At that meeting, regulators also asked developers how the system would operate if the coal plant’s warm wastewater discharge – a key heat source – were discontinued in the future.
TCC has said the plant would be built in two phases, with completion goals of 2029 and 2033, and that the system could eventually make Taiwan the site of what the company says would be the world’s first megawatt-scale OTEC facility
Regulators have also criticised the lack of detailed plans for monitoring impacts on whales, dolphins and other species that may frequent the deeper waters, and called for clearer mitigation strategies. Citing international research, they noted deep-sea water extraction has shown significant effects on crustacean populations in other contexts.
Local residents have added social pressure. Some have pointed out that the facility is now planned on a green buffer zone previously earmarked to protect village residents from power plant impacts, a shift they say was not clearly communicated earlier.
Taiwan is pushing to reduce dependence on fossil fuels and expand renewable energy under targets set in its Renewable Energy Development Act, which aims to lift total installed renewable capacity to around 27 gigawatts (GW) by 2025, with major growth in solar and offshore wind power.
While solar and wind have dominated Taiwan’s renewable strategy, with offshore wind projects rapidly expanding, OTEC represents a smaller but potentially significant source of 24/7 renewable baseload power in regions with high ocean temperature gradients. Regions where surface water remains warm year-round and deep water stays cold, as off Taiwan’s steep east coast, are considered promising for the technology.
However, the lack of extensive commercial experience with OTEC and remaining environmental uncertainties underscore the regulatory caution. The environment ministry reiterated last week that revised data and mitigation plans are required before the project can advance to the next stage of environmental impact assessment.
Ocean thermal energy conversion remains rare globally, with no large-scale commercial plants in operation. Most projects worldwide are limited to small pilot facilities in places such as Japan, Hawaii and parts of the Caribbean, reflecting high costs, engineering challenges and unresolved environmental questions.
One of the most advanced projects is Japan’s pilot OTEC facility on Kumejima island in Okinawa, which produces around 100 kilowatts of electricity, far below commercial scale, and has been used primarily for research into technical feasibility and environmental impacts rather than power generation.
