Engines that can operate using a mixture of two different fuels are called dual-fuel engines. Frequently, diesel and natural gas fuels are used together within dual-fuel engines. Often, dual-fuel engines that mix diesel and natural gas can also operate using diesel fuel only if the natural gas is temporarily unavailable. Dual fuel engine technology has proven itself over the years in drilling and well-servicing applications.
The dual-fuel engine is one of these incremental steps in our energy transition towards 100% renewable energy by reducing its environmental footprint and improving its financial performance.
Dual-fuel engine is the diesel engine that can run on both gaseous and liquid fuels. When running in gas mode, the engine works according to the Otto process where the lean airfuel mixture is fed to cylinders during the suction stroke. Efficiencies exceeding 47% have been routinely recorded. When running in diesel mode, the engine works according to the Diesel process where the diesel fuel is fed to cylinders at the end of compression stroke. The engine is optimised for running on gaseous fuels and diesel fuel is used for back-up fuel operation.
Diesel fuel goes through a longer journey in reaching the engines on a well site. This journey includes oil production, oil transportation, diesel production at a refinery, storage, transportation, and delivery to the pump truck. All these steps within diesel’s journey come with additional costs. Meanwhile, natural gas produced at the wellhead can be processed on location and delivered to the engines. Using available on-site natural gas instead of diesel, results in operational savings for drilling and well-servicing contractors.
Power density is an engine’s power output per unit of engine volume. For example, for large displacement engines, you would often see larger natural gas engines deliver power output comparable to smaller diesel engines. In other words, diesel engines have higher power density than natural-gas only engines. Meanwhile, there are also diesel engines upfitted for dual fuel applications. This combined with the electronic controls within the engine allows a dual fuel engine to feature diesel-like power density while operating in dual fuel model.
The DF technology enables the engine to be operated on either natural gas, light fuel oil or HFO. Switching between fuels can take place seamlessly during operation, without loss of power or speed. The engine is designed to have the same output regardless of the fuel used.
LNG shipping : Since the beginning of the 21st century, LNG has been very much in the picture. Oil majors are expecting that LNG will be taking a much larger share in the energy mix in the next 25 years. The LNG value chain necessarily involves LNG shipping. It’s in this part of the value chain that we’ve seen some major technology changes recently. .
This electricity is used to drive the propeller for propulsion of the vessel, as well as to operate equipment for regasification. DFDE has been commonly employed as the main engine for newbuild Floating Storage and Regasification Unit (FSRU) since substantial electricity is required for operating regasification equipment. Powerships® also adopt DFDE to generate electricity for the shoreside.
The introduction of the dual fuel diesel electric (DFDE) LNG carrier (LNGC) and the slow speed diesel driven LNGC with onboard reliquefaction (DRL) are radical departures from the currently dominant steam turbine drive technology. The introduction of the dual fuel diesel electric drive systems could also open the door for dual fuel gas turbine electric (DFGTE) propulsion systems, as they are based on the same electric drive concept.
Electric propulsion systems for LNGC’s include the following components:
•Prime movers, i.e. dual fuel diesel engines;
• Prime mover driven generators;
• Main switchboard to distribute the generated power to the various consumers;
• Propulsion transformers;
• Frequency converters;
• Electric propulsion motors;
LNG as an alternative/duel fuel for maritime operations offers
- Lower costs per measurement energy of fuel
- Adheres to new emissions regulations
- Technological and operational improvements in vessels and terminals
LNG as a fuel needs to follow a carefully planned implementation process that is fully integrated (economic, technologically, public awareness, political, protect the environment, safety, etc.)
MAN and ABB Partner on Dual-fuel Electric Propulsion
Engine manufacturer MAN Energy Solutions and technology company ABB will work together to develop a dual-fuel electric plant concept for liquefied natural gas (LNG) carriers, engineered as part of the companies’ efforts to help the international shipping industry reduce its emissions footprint.
Under a Memorandum of Understanding, signed at September’s SMM trade show in Hamburg, the two companies will develop a Dual-Fuel, Electric+ (DFE+) propulsion system concept based on MAN’s new 49/60DF four stroke engine and ABB’s Dynamic AC (DAC) power distribution and control system. It will be suitable for LNG carriers as well as floating storage units (FSU) and floating storage and regasification units (FSRU).
A combined dual-fuel electric power and propulsion system could be installed with an energy storage solution to enhance load management, or come coupled with ABB’s Azipod electric propulsion. MAN and ABB will also explore integrating fuel cells as the technology matures. “This agreement represents an agile response from MAN and ABB, using our technologies to deliver a next-generation, Dual-Fuel, Electric+ (DFE+) propulsion concept. This technology will help customers to reduce their CO2 footprint and fuel costs, and provide flexibility in operation. ABB’s DAC system and global presence are an ideal match for our new four-stroke engine.”
Whereas the conventional DFDE concept is characterized by constant-speed operating engines (gensets) over the entire engine load, optimized for high load, for example, the 85% load point and in part- and low-load have high methane slip and less efficiency, the new MAN/ABB DFE+ concept comprises variable-speed operating engines (gensets) over the entire engine load and better efficiency with significant reduction of methane slip over the entire engine map.
While variable-speed applications are well established for liquid-fuel systems up to 10mWe, torque requirements and the low efficiency of first-generation dual-fuel engines – including limitations in the e-systems design for diesel-electric propulsion systems over 10 mWe – killed variable speed for propulsion systems over 10mWe.
ABB’s Dynamic AC technology enables the operation of propulsion systems above 10 mWe at variable speed with all the accompanying benefits. In combination with the second-generation, high-efficiency MAN 49/60DF engine (with ALSi – Air Lubrication System interface, as an add-on), this DFE+ concept will provide customers with next-level efficiency and flexibility.
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