Ocean thermal power generation

Development course

The idea of thermoelectric power generation was proposed as early as 1880 by the French D 'Arsonde (1851 ~ 1940), and in 1929 his student Claude (G. Clude) built a 22-kilowatt seawater thermoelectric power test plant on the coast of Cuba. The Claude pilot plant's power system uses an opencycle (it is worth mentioning that one of the main advantages of this cycle is that fresh water can be obtained from it). Claude's ocean thermoelectric power plant ended in failure, but it proved the feasibility of ocean thermoelectric power from the experiment. In order to avoid the problems encountered in the ocean thermal power station built by Claude, in 1965, the Anderson and his son in the United States proposed a power generation method using propane as the working medium.

In 1979 the United States first developed the ocean temperature difference generator (Oceanthermalenergyconversion OTEC) system, the capacity is only 50 kw. In 1981, it was planned to develop a large 40MW plant and put its 1MW intermediate unit into trial. The United States 50kWMINI-OTEC seawater thermal power generation ship, converted from a barge, the generator emits 50kW of electricity, most of which is used for pumping water, with a net output of 12-15kW. This is a historic development in the use of ocean heat energy. Due to the small temperature difference of the OTEC system, the net efficiency of the Rankine cycle is only 3%-5%.

In the "Sunshine Plan" of the Japanese Institute of Industry and Technology, the low-temperature differential power Generation Committee has planned a floating power station with a power generation capacity of 100,000 kilowatts, and the Rankine cycle efficiency of the power station is 3.44% and the net efficiency is 2.04%. The Peruvian seawater thermal power plant, part of Japan's "Sunshine Project", uses freon HCFC22 instead of ammonia as a working medium. Since the 1980s, Japan has developed power generation equipment with different capacities such as 50kW, 75kW, and 100kW, and in 1996, it also verified the use of NH3/ water mixed working medium cycle test equipment, as well as power generation equipment set on the surface of the ocean. The power station is built on shore and has a maximum generating capacity of 120kW and a net output of 31.5kW.

The Indian government will develop Marine thermal energy as one of the important energy sources in the future. In 1997, the National Institute of Ocean Technology of India and the University of Japan signed an agreement to jointly develop the Marine thermal energy of the Indian Ocean, jointly develop 1MW power generation equipment, and develop 25-50MW large-scale commercial equipment after the verification and evaluation of the simulator. We intend to invest in the establishment of a commercial OTEC system in India. In 1999, in the southeast sea of India, the world's first set of 1MW Marine thermal power generation experiment equipment was successfully operated.

In 1989, Taiwan proposed to the Pacific International Technology Research Center (PICHTR) to implement the OTEC commercialization strategic plan in Taiwan, preparing to build a 5MW small-scale OTEC pilot power plant on the eastern coast of Taiwan Island. Taiwan Hongchai seawater thermal power plant plans to use the 36-38℃ of waste hot water discharged from the Maanshan nuclear power plant and 300m deep cold seawater (about 12℃) temperature difference to generate electricity. The cold water pipe, with an inner diameter of 3m and a length of about 3200m, extends to a trench of about 300m depth in the Taiwan Strait. It is expected that the power generation of the power plant will be 14.25MW, and the net power generation will be about 8.74MW after deducting the power consumption such as pumps.

Key technology

So far, the Marine thermoelectric power generation technology has made great progress in the research of thermal power cycle mode, efficient compact heat exchanger, working medium selection and Marine engineering technology, and many technologies have gradually matured.

1) Heat exchanger is the key equipment of ocean thermal power generation system. Titanium heat transfer and corrosion resistance is good, but the price is too expensive. Researchers at Argonne National Laboratory in the United States have found that the life of the improved brazed aluminum heat exchanger can reach more than 30 years in the corrosive warm seawater environment. Plate heat exchanger has small volume, good heat transfer effect and low cost, and is suitable for use in closed cycle.

2) The latest Lorentz cycle organic liquid turbine can work at 20-22℃ temperature difference, suitable for closed cycle equipment. Lorentz cycle is characterized by high thermal efficiency and close to the actual cycle, and its turbine uses more than two freon mixtures as working medium, and is matched with a suitable heat exchanger.

3) There are two types of ocean thermal power generation: shore-based and offshore. The shore-based type locates the power generation device on the shore and extends the pump to 500-1000m or deeper in the deep sea. The offshore type is to lift the suction pump from the ship, the generator set is installed on the ship, and the electricity is transmitted through the submarine cable. In 1979, the United States built a mini-OTCE power generation device on the western coast of Hawaii, which was the first time in the world to obtain practical electricity from ocean temperature differences. The Pacific High Technology International Research Center (PICHTR) has also developed subsidiary industries using cold seawater for air conditioning, refrigeration and mariculture, which show good market prospects in tropical islands.