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Fiber Optic Temperature Sensing – Enable Electrification of World’s Shipping Fleet

posted by Rugged Monitoring on 2020-07-30

Why are Electric Ships a Popular Alternative to Conventional Ships?

Maritime transportation contributes to more than 2% of worldwide greenhouse gas emissions and transportation across water bodies is expected to increase by 3.8% by 2022. A worrying discovery is that the amount of nitrogen oxide and sulphur oxide pollutants produced by the 15 largest cargo ships is greater than the pollutants released by all the cars in the world. Scientists predict that if we do not convert to cleaner means of energy then air pollution levels will increase 250% of current level by 2050 and maritime traffic responsible for almost 20% of global carbon dioxide emissions. 

Therefore, electrification of ships is very important for countries to meet their environmental targets. Other reasons behind the high growth of electric ship industry are, increase in seaborne trade, IMO Sulphur 2020 regulations and growing maritime tourism. The major challenges electric ship industry is facing are:

  • The conventional Li-Ion battery pose a great safety risk due to thermal runway issues
  • Current EV batteries (Li-Ion) does not have enough power to move cargos around the globe.

Latest Trends in Electric Ships

Several new types of batteries have been proposed to be used in electric ships and many of them have already been implemented with the most famous option being the lead-acid batteries. Additionally, battery technologies such as lithium-ion, fuel cells are being tested to be used in electric ships and recently a new electric ship had a mix of lithium-ion batteries and ultracapacitors which allowed for an energy capacity of 2.4mWh. 

EV Traction motors of electric ships allow better speed, control, flexibility in architecture and reduced noise and vibration levels. We still need better performing traction motors with high energy efficiency for large vessels.

The need for higher voltage is just as important as a high-density battery with a large capacity. The power train operating voltage increases with larger vessels that are needed for the transportation of large containers. A higher voltage input allows us to have a smaller generator, motor, and cables which would save money and weight.

The EV battery and the EV motor help determine the range of any vehicle which is crucial as it dictates how far someone can travel before needing to refuel. Currently, the longest range of an electric ship is 12000 miles at 12 knots which is possible because of having big solar panels that create 150 kW which fuels the motor.

However, the ship will need to be charged at some time and this sector of the industry has been seeing some very impressive advancements. For example, a German company has presented an inductive charging system for electric ferries. This wireless charging technology is already been implemented in Norway and it is said to reach charging capacities up to 100kW while the ferries only wait for a few minutes at each stop.

The innovations are happening almost every week in this industry with an objective of making electric ships a commercially viable option.

Electric Powertrain Design for Ships

The companies that design and manufacture these electric ships have an uphill battle of creating an EV design that house internals which can be comparable to its gasoline fuelled counterparts. As the new technologies are being developed, these engineers need a capable testing tool that provides precise and reliable results at high voltages.

The new developments and new testing environment need safer, accurate and fast responsive sensors. These new technology sensors must reduce the test setup time and provide flexibility to test EV powertrain for all real-life conditions.

The performance and aging of EV powertrain depend on the temperature distribution and developing hot spots within EV motors, EV inverters and batteries. Therefore, identifying the hot spot location and continuously monitoring them during the EV test cycles helps in improving EV powertrain design. 

The accurate thermal profiling of Motor stator winding and cooling duct enables in selecting right kind of insulation, design for better cooling and optimizing motor control algorithm. Similarly, accurate thermal profiling of EV battery modules and battery pack helps in avoiding thermal runaway situation at later stage. 

Fiber optic temperature sensing technology is gaining a lot of interest among EV design engineers for prototype testing of EV Powertrain.

Importance of Fiber Optic Temperature Sensors in EV Thermal Management

The traditional sensors such as thermocouples are quite slow, and they deliver inaccurate results, especially when installed at high voltages. These sensors also pose a serious risk of short circuit or electrocution if not being isolated properly.

Fiber optic temperature sensing technology overcomes the challenges of conventional temperature sensors (thermocouples). The following feature of FO temperature sensors make them ideal for EV prototype testing:

  • Highly Di-electric, Safer to be used in High Voltage environment
  • No need for complex isolation and lengthy calibration/compensation
  • Ultra-small size (up to 0.4mm) to fit into Power Module and Battery cells 
  • High accuracy, ±0.2⁰C with 100% repeatability
  • High Response time <40ms
  • Robust and easy to route cabling

The fiber optic temperature sensors are being used by EV design, instrumentation, and test engineering in the following applications:

  1. Traction Motor Testing: Stator winding hot spot, Rotor temperature, HV Terminals temperature measurement. 
  2. Power Electronics Testing: Junction Temperature (IGBT, Diode), Capacitor Core Temperature, and HV Terminals temperature testing
  3. EV Battery: Cell Core/Anode thermal profiling, Intercell temperature, Battery Pack Hot Spot, HV Terminals temperature, Cooling thermal profiling, Battery Abuse Testing etc.

Rugged Monitoring Sensors and Monitors for EV Testing

Rugged Monitoring (RM) has developed several products such as the LSENST and LSENSB sensors which utilize fiber optic technology of temperature measurement. The sensors are being used by major EV manufacturers globally, in measuring temperature of high voltage components such as EV battery, EV motor, charging boards, HV connectors, EV inverters and power electronics.

The RM sensors have a temperature range of -270 °C to +250 °C and have a repeatability of ±0.2 °C. These sensors connect to the fiber optic temperature monitors for temperature measurement, data display, configuration, and data integration with third-party dataloggers. RM also provides proprietary software for remote visualization and configuration. The software is designed to provide the most relevant information while protecting the data with the greatest level of security.