Last month the UK’s Olympic and Paralympic team gathered in Manchester to celebrate their record-breaking medal haul at the Rio Olympics. Leading the celebratory parade was a gold Nissan LEAF which symbolises the continued strength of the UK automotive industry. However the gold LEAF wasn’t the only contender Nissan fielded at this year’s games. Before the celebrations in Manchester, Nissan President Carlos Ghosn unveiled a demonstrator electric van with a fuel cell range extender. The van was the result of a collaboration between Nissan and AVL who integrated a 5kW solid oxide fuel cell into an existing e-NV200 electric van.
Fuel cells aren’t new territory for Nissan. Their patent application rate in fuel cells gathered momentum in 1999 and peaked in 2004 but what sets this announcement apart is Nissan’s focus on solid oxide fuel cells. There are many types of fuel cell, but the two most relevant to the automotive sector are proton exchange membrane fuel cells (PEMFC) and solid oxide fuel cells (SOFCs). Both technologies convert chemical energy into electrical energy but how this is achieved differs. PEMFCs require purified hydrogen that is converted into electrical energy with the by-products being heat and water. Whilst SOFCs are also fuelled by hydrogen, their greater tolerance to impurities makes it possible to use an on-board reformer to convert liquid fuel into hydrogen. However the on-board reforming process does produce CO2 and other emissions.
For light duty vehicles the favoured fuel cell technology has been the PEMFC which has led to a number of strategic partnerships forming in recent years. Ford and Daimler have established a joint venture, the Automotive Fuel Cell Corporation, whilst Honda and General Motors are collaborating to develop common fuel cell systems and hydrogen tanks. Similarly bus manufacturers use PEMFC technology manufactured by Tier 1 suppliers such as Ballard Power and Hydrogenics.
SOFCs are commonly used for stationary power generation. Funding from the US Department of Energy has enabled UK technology developer Ceres Power and Cummins to develop SOFC systems that will provide power to data centres. However there are also programmes (such as the EU’s Fuel Cells and Hydrogen Joint Technology Initiative) that support SOFC development in vehicles. For example companies such as AVL, Eberspächer and Delphi are developing SOFC auxiliary power units for trucks, which help to reduce fuel consumption when idling by up to 30% compared to a diesel generator.
However one of the major challenges to commercialising SOFCs in the transport sector is the high temperatures needed for them to operate. These high temperatures can result in a delay of up to 30 minutes before they become functional. However the higher operating temperatures also make SOFCs less sensitive to impurities in the hydrogen. This enables SOFCs to run on a number of different fuels that are converted locally into hydrogen via a reformer.
Despite the low number of vehicles on the road, the early fuel cell market is distinguishing between fuel cells intended as range extenders and fuel cells intended as prime movers. For applications where the fuel cell acts as the prime mover, PEMFCs prove a more reliable choice as they can provide faster start up times. However when slower start up times can be mitigated by a bigger battery, SOFCs could potentially function as a range extender with the added benefit of being able to use the existing refuelling infrastructure.
The future role of PEMFCs and SOFCs is uncertain. To reach mass market both technologies face their own set of development challenges. However if the market for fuel cells does grow, the UK is well positioned to capitalise on the opportunity. The Advanced Propulsion Centre’s recently published Low Carbon Automotive Propulsion Technologies report identified that during 2010 – 2015, £35 million was co-invested in automotive fuel cell projects in the UK. A number of the projects focussed on PEMFCs with companies such as Intelligent Energy, Microcab, and Gordon Murray Design all co-investing in collaborative R&D projects. Furthermore early stage research activities from Imperial College London looked at the feasibility of using SOFCs as range extenders. More recently in March 2016 Ceres Power, Nissan and M-Solv were awarded grant funding by Innovate UK and the Office for Low Emission Vehicles to develop a compact, on-board SOFC stack for range extension of electric vehicles.