Ships' energy sources

Summary: Ships have used a broad range of energy sources, from human muscle to wind, steam, fossil fuels, nuclear power, and alternative systems designed to improve energy efficiency.

Throughout history, humans have tended to live near water. Since the earliest civilizations, boats have been utilized to transport people and merchandise. Initially, boats were powered by paddles, poles, and oars. Sails were then used to reduce the need for manual work. In 1783, after James Watt’s invention of the steam engine, steam engines were commonly used to power boats. In 1839, the first electric boat was developed in St. Petersburg, Russia. In the mid-1900s, both naval and nonmilitary maritime vehicles upgraded to gas turbine internal combustion power. In 1955, the first nuclear-powered submarine went to sea. Because of economic concerns in the 1980s, many gas-powered engines were replaced by diesel engines. To reduce the world’s dependence on natural resources, new technologies are currently being investigated. These include the use of liquid natural gas (LNG), tidal turbines, solar wind marine power systems, kite-assisted propulsion, biodiesel, fuel cells, and other design improvements.

Poles, Paddles, Oars, and Sails

Initially, small, flat-bottom boats, similar to punt boats, were powered in shallow water by the punter pushing against the riverbed with a pole. These boats operate as a gondola does, propelled by an oar.

Egyptian hieroglyphs, from as early as 3000 BCE., depict boats being rowed downstream in the Nile and boats sailing upstream against the current. By 1100 BCE, Phoenicians were using vessels for war. At this time, the only opportunity for increasing speed was directly related to the number of oarsmen. Lengthening the boats to accommodate additional oarsmen led to structural issues. By 700 BCE, a bireme was constructed. This type of vessel included an additional deck to hold additional oarsmen. Soon thereafter, the trireme was developed to hold three banks of oarsmen. During the fighting of the First Punic War in the 260s BCE, the Romans used the quinquereme (developed about a century earlier), with five banks holding about 300 oarsmen. Sea battles involving a large number of oarsmen ramming the enemy lasted until about 1571.

As interest in exploring the oceans increased in the 15th century, additional masts were added that included four to eight sails. During the 17th and 18th centuries, merchant ships were developed; these focused more on size, beauty, comfort, and safety (against pirates) than speed.

Steam Engine

In 1769, James Watt invented the improved steam engine, thereby starting the Industrial Revolution. In 1783, the French used steam to power a boat across the Seine River. In the United States, Robert Fulton demonstrated practical steamboat travel in 1807 with the Clermont, which steamed between New York City and Albany. In 1838, the Sirius made the first transatlantic voyage entirely on steam. Early shipping companies, such as Cunard and Peninsular Steam Navigation, competed for the fastest transatlantic passage

By 1850, the compound steam engine was developed, which used steam twice in each engine cycle, allowing heavier ships to be constructed. The development of the compound steam engine, as well as the screw propeller, the triple expansion engine, and the replacement of iron with lighter steel, facilitated the task of increasing speed.

During the majority of the 19th and part of the 20th centuries, paddle-wheel steamboats dominated commerce on the Mississippi River. In June 1897, Charles Parsons demonstrated a steam turbine in the Turbinia, which was much faster than any ship in the Royal Navy. Steam turbines were widely used by ships in the 20th century, including all nuclear-powered vessels.

Gas Turbines

Since 1949, when the gas turbine ship Auris was constructed, gas turbines have been used to power vessels. Gas turbines are still being used and may be the future of power for nautical vessels. They offer high power-to-weight ratios. However, the use of fuel presents many environmental, economic, and efficiency challenges.

The gas turbine consists of a compressor, a combustion area, a turbine, an accessory driver gearbox, and a reduction gearbox. The gas turbine produces a rotational force that is usually used to turn a propeller or generator. When compared to the acceleration and deceleration of the pistons in other internal combustion engines, the gas turbine produces a much more fluid power process. The biggest disadvantage is its inability to burn cheap, dirty, heavy fuel oils. A gas turbine that is testing heavy fuel oil generators is being used in parallel with a steam turbine to power the Celebrity Cruise ship, the MV Millennium. The RMS Queen Mary 2 is powered by two gas turbines in parallel with four diesel engines.

Diesel Engines

Piston-driven diesel marine engines, currently the most common engines in the shipping industry, generate higher torque, which allows for more load to be carried with less engine strain. Diesel engines are composed of a clutch, marine reduction gear, the thrust block, the OD box (which operates the controllable pitch propeller, or CPP, system), and the electric motor. Most large engines currently in the shipping industry contain a slow-speed, two-stroke engine directly connected to a propeller shaft.

On February 14, 1912, the MS Selandia was built at the Burmeister and Wain shipyard in Denmark; it was the first oceangoing motor ship. It contained two B&W DM815OX, four-stroke, reversible engines. During World War II, Fairbanks Morse began supplying the US Navy with marine diesel propulsion plants.

In 1942, the Danish introduced one of the first dual-fuel operating boats, the Frank FN282. It had a two-cylinder, 90/100-horsepower, alpha diesel type 342 engine, which was used to ignite the natural gas.

In 1972, Burstein and Wain launched a new Selandia with improved technology. It was 2.5 times longer, twice as wide, and 2.5 times faster than the original of about 60 years earlier. It used three diesel turbocharged, two-stroke engines (one 12-cyclinder and two 9-cyclinder Gotaverken engines).

If a ship operates at a slower speed, diesel engines have improved fuel consumption and lower fuel costs. Although diesel fuel costs may be lower, the general maintenance and repair costs on diesel engines are usually higher, and therefore the overall operating cost of a diesel engine is higher. Additionally, the Environmental Protection Agency’s rules requiring lighter, cleaner, and more fuel-efficient diesel engines have reduced the reliability of new diesel engines in the United States. In the European Union in 2009, the HERCULES-Beta Project was approved to develop optimally efficient and clean marine diesel engines.

Nuclear Fuel

A much more efficient method for powering ships is the use of nuclear fuel. A small amount of nuclear fuel can provide the energy equivalent of millions of times its weight in coal or oil. The need for a much smaller facility to house this fuel allows for additional space for cargo or weapons. Furthermore, nuclear reactors do not need the space for combustion air or exhaust air stacks. This makes submarines powered by nuclear reactors quite feasible. The USS Nautilus, the first nuclear-powered submarine, was introduced in 1955. By 1990, more nuclear reactors were used on ships than large reactors for commercial electric power plants.

Nuclear-propelled merchant ships have used low-enriched uranium. In 1962, the United States built the NS Savannah. It was neither economical enough to run as a merchant ship nor efficient enough to run as a freighter or passenger line. The Russians have successfully capitalized on the benefits of nuclear power to have eight nuclear-powered ships as icebreakers.

The use of nuclear power on ships raises many technological, environmental, and political concerns. First, marine nuclear reactors, unlike land-based power plants, must operate in turbulent seas. The marine nuclear reactor fuel is usually more enriched than the land reactor fuel. Questions remain regarding the proper decommissioning of these vessels and civil liabilities worldwide. The US government is investigating ways to use ships, especially nuclear-powered vessels, in military or disaster locations.

Alternative Power Sources

It is estimated that improved hydrodynamics and machinery could reduce a ship’s energy cost by 5 to 30 percent. In 2024, the demand for shipping was at an all-time high, reaching an estimated 15.94 Twenty Foot Equivalent Units (TEUs) at one point in the year. Changes in the ship design—for example, incorporating bulbous bows and stern flaps—could make new ships more dynamic and efficient. During the late 1950s, to reduce the drag on commercial cargo ships, a bulbous bow was developed to reduce fuel consumption by 5 percent. This technology became much more important after 1973, when the Organization of Petroleum Exporting Countries (OPEC) reduced the supply of oil, increasing fuel prices worldwide. Side bulbs, bilge bulbs, and stern bulbs have also been investigated, but these technologies have not been as successful at improving fuel efficiency as bulbous bows. Today, bulbous bows can reduce fuel consumption by as much as 15 percent. Improving turbine design, such as through the use of intercooled recuperated (ICR) turbines or integrated electric-drive propulsion, could improve fuel efficiency by 20 percent.

In the future, large towing kites attached at the bow may reduce fuel consumption by up to 35 percent. Another project for utilizing wind energy involves the German rotor ships. Instead of traditional sails, tall cylindrical towers spin (like a windmill) to produce significantly more power than a sail. Another future option for powering vessels may be to use fuel cells or line traditional sails with solar panels. These panels would provide auxiliary power and perhaps reduce fuel consumption by 40 percent.

Emissions from coal- and oil-powered engines have a negative effect on the environment. Although more expensive, LNG is being considered as a viable fuel source. Currently, the North Sea offers LNG from Norway’s own gas fields. Although the supply of LNG for fueling ships is limited, LNG would significantly reduce carbon dioxide emissions and nitrous oxides, as well as eliminate particulate and sulfur emissions.

Bibliography

Gallucci, Maria. "Dirty Diesel Ships Can Start Decarbonizing Now. Here's How." Canary Media, 10 July 2023, www.canarymedia.com/articles/sea-transport/dirty-diesel-ships-can-start-decarbonizing-now-heres-how. Accessed 6 Aug. 2024.

Hennessey, Philip. "Record-Breaking Demand for Ocean Container Shipping Adds to Perfect Storm in Market." Xeneta, 10 July 2024, www.xeneta.com/news/record-breaking-demand-for-ocean-container-shipping-adds-to-perfect-storm-in-market. Accessed 6 Aug. 2024.

InterAcademy Council. “Transportation Energy Efficiency.” In Lighting the Way: Toward a Sustainable Energy Future. Amsterdam: InterAcademy Council, 2007.