Availability: Fuel Cell

Proton Exchange Membrane or PEM Fuel Cells are considered to be the most versatile type of fuel cells currently in production. They produce the most power for a given weight or volume of fuel cell. Because they are lightweight, have such high power-density, and cold-start capability, they qualify for many applications, such as stationary combined-heat-power, transport, portable power and even applications in space.

 

 

 

Fuel Cells Comparison – Image courtesy of Nedstack Fuel Cell Technology BV

 

Pure hydrogen-powered PEM Fuel Cells emit zero particulate matter, SOx or NOx, zero CO or CO2. They have long lifetimes (>20,000 hours) before refurbishment is required and they have a high power density.

 

Their low operation temperature makes them ideal for operation on ships, as well as being a proven technology with a strong track record in a large variety of applications. (From Nedstack Fuel Cell Technology BV)

Design

 

A wide range of product and application-relevant standards to safeguard fitness-for-use exist for all relevant applications of fuel cells. The cornerstone of compliance is that all stack designs and the production system observe the IEC 62282-2 standard on the safety of PEM Fuel Cell stacks. Product designs should be independently verified and production systems should be designed to verify every stack by means of a standard compliant exit-factory inspection routine, as shown below. (From Nedstack Fuel Cell Technology BV)

 

 

 

IEC 62282-2 Tests – Image courtesy of Nedstack Fuel Cell Technology BV

 

Use on ships

 

The use of fuel cells on ships is allowed by international conventions. In April 2022, the IMO approved the ‘Interim guidelines for the safety of ships using fuel cell power installations’. In addition, all major classification societies have rules or guidelines in place.

 

New developments and innovations in fuel cells, which may not be directly covered by the existing rules and guidelines can still be safely installed on board using the alternative design method in accordance with SOLAS Regulation II–1/55 for demonstration of an equivalent level of safety.

Degradation of materials

 

In the graph below, the variation of voltage with current is shown for a typical PEM stack. A fuel cell always follows the imposed load.

 

 

Stack Voltage vs Stack Current – Image courtesy of Nedstack Fuel Cell Technology BV

 

To follow this load, adequate hydrogen and oxygen must be present. If reactants are lacking, the fuel cell consumes materials of the electrodes, such as carbon, and damages itself.

 

Prevention is ensured by assuring the availability of hydrogen and air must before a load is applied. Cell voltage monitoring is installed to prevent damage when the load settings are too high. A group of stacks will stop automatically when the cell voltage on any stack in that group drops below a threshold value. (From Nedstack Fuel Cell Technology BV)

 

Constructing fuel cells with durable materials reduces risk of degradation and increases life span. For example, PowerCell’s unit cells consist of compact and lightweight metallic bipolar plates combined with durable and highly efficient membrane electrode assemblies. (From PowerCell Sweden AB)

Overheating

 

The PEM fuel cell stacks manufactured by Nedstack operate at temperatures around 65ºC. Excess heat generated during power generation is transferred by a cooling medium. This is pure water with an electric conductivity below 5 µS/cm. The water needs to maintain a low conductivity to prevent short circuit currents between individual cells. The demineralized water efficiently carries the generated heat. (From Nedstack Fuel Cell Technology BV)

A fuel cell stack will not operate stand-alone, but needs to be integrated into a fuel cell system to generate power. On a ship, this is called marinisation.

 

In the fuel cell system, different auxiliary components such as compressors, pumps, sensors, valves, electrical components and control unit provide the fuel cell stack with a necessary supply of hydrogen, air and coolant.

 

The control unit enables safe and reliable operation of the complete fuel cell system.

 

Operation of the fuel cell system in the targeted application will require additional peripheral components i.e. power electronics, inverters, batteries, fuel tanks, radiators, ventilation and cabinet.

 

 

Marinised Fuel Cell System – Image courtesy of PowerCell Sweden AB

 

 

– Information from PowerCell Sweden AB –

Several unit fuel cells are arranged in series into a so-called fuel cell stack to match voltage and power levels required in different applications. (From PowerCell Sweden AB) Such PEM-stacks are the building blocks of larger fuel cell systems. (From Nedstack Fuel Cell Technology BV)

 

 

Fuel Cell Stack – Image courtesy of Nedstack Fuel Cell Technology BV

 

A fuel cell stack is in itself a completely passive component which needs to be integrated into a fuel cell system to generate power. (From PowerCell Sweden AB)

On a ship, a Battery Management System (BMS) is an integrated control and monitoring software which continually ensures the safe operation of a battery propulsion and/or storage system on board.

 

BMS software has large bandwidth and uses an ethernet connection with remote update capability and protocols to mitigate packet loss.

 

BMS carry out the following services:

 

• Ensures smooth and safe system start-up
• Provides current control to ensure the optimal charge/discharge rate for battery longevity
• Alarms and warnings including early identification of potential points of failure, hidden failures and failure prediction
• Remote monitoring and reporting of battery performance to inform maintenance

 

Redundancy is provided using direct emergency stop controls for the crew, redundant power supplies for each string, Redundant Management Software and remote monitoring for onshore investigation of anomalies by the service team.

 

– Information from SHIFT Clean Energy –