Because it\u2019s an electrochemical, not combustion energy conversion, fuel cell efficiency can far outstrip a typical four-stroke – and there are virtually no toxic emissions.<\/p>\n
So, why hasn\u2019t this tech gained greater market share before? The economic reality is that till just a few years ago, hydrogen fuel cell costs were prohibitive \u2013 but that\u2019s changing rapidly: Ballard, for example, is \u2018confident\u2019 it will soon be pitching a per-kilowatt price competitive with diesel engines. However, it\u2019s largely been driven by the car industry, points out Sami Kanerva, senior principal engineer at ABB Marine & Ports: to be pragmatic, a swathe of maritime development has to hang onto automotive\u2019s coat-tails, \u201cas mass production allows us a competitive price\u201d.<\/p>\n
But that\u2019s not the whole story: it\u2019s not a single solution, and neither, says Kanerva, \u201cis there a simple, silver bullet\u201d.<\/p>\n
Most fuel cells work on roughly the same basis. Hydrogen and oxygen will always try to hook up, but they\u2019re sat either side of an electrolyte \u2018gateway\u2019 which only passes positively charged particles. However, when either set of molecules are separated from their negatively-charged electrons by a catalyst, the (positively charged) ions rush straight through the electrolyte to party on the other side. That leaves the electrons running around the exterior circuit to join the fun, creating a current.<\/p>\n
In Kanerva\u2019s view, small to midsized vessels will likely go for Proton Exchange Membrane (PEM) cells. These have a \u2018moderate\u2019 50% to 60% efficiency, \u201cand can respond to load changes and acceleration very fast\u201d, he says, although in crossing over from the automotive sector, \u201cmarine applications will want to slow that down a bit\u201d. Cars for personal use have very different requirements, generally below 10,000 hours – but onboard the stack\u2019s lifetime is critical. He adds: \u201cAs the cells can suffer from hydrogen and oxygen imbalance, especially with repeated dynamic load changes, it\u2019s better to incorporate a battery as a protective buffer.\u201d<\/p>\n
It doesn\u2019t, however, translate into a workable alternative for larger ships. The major drawback is that PEM cells are susceptible to fuel impurities: traces of carbon monoxide can bind to the expensive platinum catalyst, poisoning it. Therefore, \u201cyou are tied to using \u2013 and carrying – pure hydrogen\u201d says Kanerva. This \u201cmakes it unlikely it will be the answer for long-distance shipping\u201d.<\/p>\n
Into this open arena steps a less well-known technology: Solid Oxide Fuel Cells (SOFCs). Already utilised in landside power generation these can also handle hydrocarbons along with ammonia and alternatives \u201csuch as ethanol, methanol, or almost any other compliant [gaseous] fuel\u201d says principal approval engineer Mun Hwa Jung, DNV GL Korea.<\/p>\n
THE GOAL: AN SOFC-POWERED AFRAMAX LNG CARRIER<\/strong><\/p>\n However, its power and heat characteristics make it \u2018big ship\u2019 technology, not one that can be easily incubated in cars or even onboard small vessels. Therefore, despite a couple of interesting pilots, it hasn\u2019t gained traction in the marine market… till now. Samsung Heavy Industries has just declared it is set to run with a 174,000m3 LNGC new building: completion is planned \u201cfor the end of 2022\u201d says SHI\u2019s senior engineer Young-Seok Yang.<\/p>\n SHI\u2019s plans are ambitious: most of these gas carriers are dual-fuel, but the yard\u2019s alternative \u201caims to replace all the existing main engines and generators\u201d explains Yang. Therefore the upgraded vessels will need to have a huge 30MWs of SOFCs onboard to cover both propulsion and hotel loads.<\/p>\n It\u2019s a direct shot across the bows for manufacturers such as W\u00e4rtsil\u00e4 which, it might be remembered, made its name from repowering LNG carriers with dual-fuel engines and continued to carve out a low-emission niche ever since.<\/p>\n The prominent shipbuilder is working with Bloom Energy, which is aggressively pitching its SOFC solutions to a number of industries and claiming a large slice of the pie. The technology has a lot going for it, typically returning 60% to 65% efficiency.<\/p>\n Like PEM cells, the solution has scalability, says Yang: \u201cA power module can produce 75kW of electricity and four or six modules can be configured into an [interconnected] system,\u201d multiples coming together to reach the desired output.<\/p>\n But most interestingly, the SOFC stacks operate at between 800\u2103 and 850\u2103: the temperature at which oxygen ions are conducted from the cathode, through the solid electrolyte, to react with the hydrogen. It also utilises carbon monoxide (CO) and handles other trace elements that would kill a PEM FC.<\/p>\n This heat has another use. A proportion is recycled inside the fuel cell, where it\u2019s used to steam-reform the LNG at the anode. The process transforms the methane into a mixture that\u2019s mostly H2 with a bit of CO, which reacts in the cell to create carbon dioxide. Admittedly, this joins the smattering of CO2 produced by the reformer, but SOFCs are a good candidate for carbon-capture techniques because the CO2 can be hived off in a containable stream, something also being considered by SHI.<\/p>\n Finally, the 300\u2103 exhaust gas exits at a little higher than atmospheric pressure, explains Yang. That makes for useful, high-grade thermal energy to be directed toward economisers, auxiliary boilers or possibly a steam power turbine. It\u2019s all mature technology, but it stands increase that 60% efficiency to an impressive 85%.<\/p>\n HURDLES<\/strong><\/p>\n Still, the utilisation of SOFC technology requires consideration.<\/p>\n \u201cYou have to think about how the cells themselves react to the heat,\u201d says Kanerva. Fast cycling between different temperatures causes stress, fatiguing and sometimes cracking structures: as a result \u201cyou need to warm up these kinds of cells rather slowly\u201d.<\/p>\n It\u2019s not a natural solution for very dynamic loads and system longevity demands the fuel cells are paired with a battery pack to mitigate thermal cycling; although \u201cthe size of this will depend on the load profile of the ship\u201d, explains Yang, adding that \u201cpower management will be developed during the JDA [with Bloom]\u201d.<\/p>\n However, it would seem to suit tankers like these Aframax LNG carriers. In fact, these cells may be kept running throughout the entire journey, says Jung. Of course, \u201ca remaining challenge is how to manage the constant power output in case the consumer load drops\u201d he explains, which, if the excess energy is to be stored, will, in turn, affect the scale of the battery. He admits, \u201cthere are more details to be worked out\u201d for this type of vessel.<\/p>\n Still, physical integration presents the most significant technical hurdle: splitting the plant into two rooms is being \u201cconsidered\u201d, says Yang. But given the extreme heat and explosive potential, there are further demands from both class and IMO regulations.<\/p>\n Therefore, \u201cthe fuel cell stacks are enclosed within a hot box as the primary barrier,\u201d says Jung, but these, and the pipework, should also be enclosed within a secondary barrier with gas detection capability and continuous ventilation. That alone makes it rather different to present LNG or low flashpoint fuel installations, where double-layer protection is limited to the fuel supply lines and doesn\u2019t extend to the plant itself.<\/p>\n It\u2019s worth underlining, each of these stacks is separately enclosed. However, as Jung points out, while it may seem troublesome, that does avoid making every electrical component in the fuel cell room ATEX compliant.<\/p>\n Generally, \u201cthe challenges are space and price… currently, these come in at a higher cost than conventional four-stroke engines\u201d says Jung. How much higher is still difficult to work out as even for landside applications, the prices are under wraps \u2013 although it appears they\u2019ve come down a lot in the last couple of years.<\/p>\n It does help that unlike PEM cells, it ditches expensive platinum-coated anodes, Bloom\u2019s tech uses inexpensive alloys \u2013 but there are other costs likely attributable to the electrolyte. Still, it seems more economies of scale will follow and possibly the SHI-Bloom partnership will explore investment easing approaches \u2013 but that remains to be seen.<\/p>\n Further, although \u201cit needs more space [in the power plant room]\u201d Jung points out: \u201cThere\u2019s one more thing to say… If the SOFC is to replace the main engines entirely, you can remove many of the traditional propulsion components from the vessel.\u201d Interestingly, Yang adds that a number of auxiliary arrangements can be eliminated \u201csuch as lubricating, compressed air, cooling water, and steam systems\u201d.<\/p>\n Will this technology find further take up? Yang believes so: \u201cFuel cells are being \u201ctouted as a next-generation\u201d marine power replacement as environmental issues ascend the agenda, adding that SHI\u2019s FC system \u201cwill be the safest and the most reliable solution in the industry\u201d.<\/p>\n The combination of efficiency, fuel flexibility and low-to-no emission running could prove very attractive to other segments, especially if paired with a \u2018mop up\u2019 carbon capture device. It might, eventually, even challenge the current two-stroke queens of long-haul shipping.<\/p>\n Engine manufacturers, the message is clear: you\u2019d better hold onto your hats.<\/p>\n","protected":false},"excerpt":{"rendered":" A new LNG carrier project seeks to harness the specific characteristics of SOFC technology, but the technical obstacles are considerable, Stevie Knight hears<\/p>\n","protected":false},"author":8,"featured_media":561,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[41],"tags":[],"sponsor":[],"class_list":["post-560","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-batteries-supercapacitors-fuel-cells-and-other-energy-storage-technology"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/posts\/560","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/comments?post=560"}],"version-history":[{"count":0,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/posts\/560\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/media\/561"}],"wp:attachment":[{"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/media?parent=560"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/categories?post=560"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/tags?post=560"},{"taxonomy":"sponsor","embeddable":true,"href":"https:\/\/www.motorship.com\/propulsion-and-future-fuels-conference\/wp-json\/wp\/v2\/sponsor?post=560"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}