Dalian Ada Ship & Marine Engineering Co., Ltd.
I. Types and Industrial Structure of Ship Propulsion Systems
Ship propulsion systems, consisting of main engines (diesel engines, steam turbines, gas turbines, etc.), transmission systems (shafting, gearboxes, couplings, clutches, etc.), and propellers (propellers, omni-directional thrusters, side thrusters, etc.), are the most important and crucial equipment on board a ship. On average, their value accounts for approximately 35% of the total cost of ship equipment and about 20% of the total ship price. Currently, there are four main propulsion methods for various types of ships worldwide: ① Steam turbine propulsion system—having replaced reciprocating steam engines, it was subsequently replaced by diesel engines. Currently, it is mainly used in LNG (liquefied natural gas) carriers and nuclear-powered military vessels. The technological development trend of steam turbines is to continuously enhance reliability and maneuverability, improve controllability, and simplify equipment. ② Diesel engine propulsion system—having completely replaced reciprocating steam engines and steam turbines, it has become the most important ship power system and is currently used in various types of ships as the main equipment of the diesel engine propulsion system. ③ Gas turbine propulsion system—starting to be used as the main engine on merchant ships in the 1950s, it has never been widely adopted and is currently mainly used in military vessels as the main equipment of the gas turbine propulsion system. ④ Electric propulsion system—starting to be used in the shipbuilding field in the 1990s, it is currently used in military vessels and small merchant ships. The proportion of ships using electric propulsion is still relatively small.
Currently, the research and development, and design of ship propulsion systems are still dominated by European, American, and Japanese countries or regions, and the manufacturing of steam turbines and boilers, gas turbines, and electric propulsion devices are also controlled by companies from these countries. However, the manufacturing of diesel engine propulsion systems, which account for the largest proportion of ship propulsion systems, has largely shifted to South Korea, Japan, and China.
II. Significance of Promoting the Application of New Energy Propulsion Systems for Ships
Currently, 95% of ship propulsion systems are diesel-powered. However, ship diesel engines have several major drawbacks.
(1) Use of non-renewable energy. The power source is non-renewable fossil fuels. According to scientists' predictions, the earth's oil reserves will only last for another 60 years. In other words, fossil fuels on Earth will be depleted in 60 years. Therefore, we must use other energy sources, preferably renewable energy. (2) Air pollution. Although technological advancements have gradually controlled the emission of pollutants from diesel engines, considering that ultra-large ships consume thousands of tons of fossil fuels per voyage, and there are also old diesel engines left over from history, these will emit large amounts of pollutants, causing serious air pollution. This is undoubtedly contrary to the theme of green environmental protection. (3) Serious noise problems. According to relevant data, the noise generated by diesel engines on ships can reach 120 decibels. This is a very frightening number; long-term exposure to such an environment will severely damage the hearing of personnel. This problem is particularly prominent in smaller ships. Therefore, it is necessary to address this issue. However, due to the structure and working principle of traditional diesel engines, it is difficult to solve the noise problem. Therefore, breakthroughs can only be sought in new energy propulsion systems.
Promoting new energy propulsion systems and using sustainable energy sources to power them, while further reducing harmful gas emissions and addressing noise issues, will not only provide a better working environment for marine engineers but also align with the country's sustainable development strategy by reducing pollutant emissions. Therefore, developing new energy propulsion systems for ships is of great significance.
III. Current Status and Development Trends of New Energy Propulsion Systems for Ships
New energy refers to various forms of energy that are directly or indirectly derived from the sun or the heat generated deep within the Earth. Compared with traditional energy sources, new energy sources have the characteristics of low pollution and large reserves, and are of great significance in solving the serious environmental pollution and resource depletion problems facing the world today. As the fuel consumption of ships accounts for an increasing percentage of total fuel consumption year by year, leading to a larger proportion of fuel costs in ship transportation, how to further improve energy efficiency in ships and effectively reduce transportation costs has become an urgent issue. With the continuous advancement of science and technology, the unique advantages and benefits of new energy sources, such as wind energy, solar energy, nuclear energy, biomass energy, and tidal energy, in energy conservation and emission reduction have become increasingly prominent, and their application and promotion in the ship transportation industry have become a trend.
1. Wind energy. Wind energy originates from the kinetic energy generated by the movement of large amounts of air on the Earth's surface. It is a pollution-free and infinitely renewable resource. The history of human use of wind energy can be traced back to ancient times. With the continuous advancement of science and technology, industrial society has accumulated rich experience in utilizing wind energy, and supporting industries and infrastructure are relatively mature. However, the use of wind energy has some drawbacks that are difficult to completely eliminate, such as intermittency, high noise levels, susceptibility to terrain influences, and interference with radar signals. Currently, the use of wind energy mainly takes the form of wind power (wind-assisted navigation) and wind power generation. In ships, its application is mainly focused on being the main or auxiliary power for navigation, and wind power generation technology is only used in a few ships.
In fact, as early as the 1980s and 1990s, Japan made new breakthroughs in the research and utilization of wind-assisted navigation. In 1980, Japan built the first oil tanker equipped with ordinary wing sails, the New Aede Maru. The New Aede Maru was equipped with two sails, 12.15 m high and 8 m wide. Later, it built motor sailing cargo ships such as the Senyo Maru and Nissan Maru. In 1984, it designed and built the 2600-ton Usuki Senpou Maru and another 31,000-ton modern wind-assisted ocean-going cargo ship. On December 15, 2007, the world's first kite-powered cargo ship, the Beluga SkySails, set sail from Hamburg, Germany.
2. Solar energy. The utilization of solar energy mainly involves two aspects of technology: photothermal technology and photovoltaic technology. Photothermal technology utilizes the thermal radiation of sunlight, and its most successful application is in solar water heaters. A further extension of this technology is solar thermal power generation, which uses concentrators to concentrate solar radiation heat energy to heat water to produce steam, and then uses steam turbines and generators to generate electricity. Considering that the demand for hot water during ship operation is not high, thermal power generation
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