The University Team Making Ships Carbon Neutral

Biofuels Engine Design, Carbon Capture/Storage/Use, Carbon Capture/Storage/Use, Co-Products, Illinois, Infrastructure, Marine/Boat Bio and Renewable Fuel/MGO/MDO/SMF, R & D Focus, Sustainability, University/College Programs, Vehicle/Engine/Motor

August 25, 2021

Print This Article Share it With Friends

(Bio Market Insights) A team of researchers from Northwestern University, Illinois have developed a novel means of decarbonising the shipping industry, using CO2-capturing solid oxide fuel cells to make vessels carbon neutral – or even carbon negative. These fuel cells ‘burn’ traditional carbon-based fuels and generate their own CO2 onboard the ship, which is later sequestered or recycled into renewable hydrocarbon fuel.

…

“It might be harder for people to see onboard CO2 capture as climate friendly because it uses conventional, carbon-based fuels,” said Scott A. Barnett, senior author of the study. “People tend to assume hydrogen fuel cells and electric vehicles are more climate friendly. In reality, they often are not. Electricity might come from burning coal, and hydrogen is often produced by natural gas, which generates a lot of CO2 in the process.”

…

The Northwestern team have also created a dual-chamber tank to store both the fuel and the captured CO2. The divider between the two chambers can move and so make space accordingly for CO2 as it is created.

“This technology really doesn’t have any major hurdles to making it work,” Barnett said. “You just have to replace the fuel tank with the double-chamber tank and add CO2 compressors. And, of course, the infrastructure eventually has to be developed to off-load the CO2 and either sequester or use it.” READ MORE

Viability of Vehicles Utilizing On-Board CO2 Capture (ACS Energy Letters)

Excerpt from ACS Energy Letters: Although battery electric and hydrogen fuel cell vehicles hold great promise for mitigating CO₂ emissions, there are still unaddressed sectors for electrified transport, e.g., the heavy-duty and long-range global shipping industry. In this Viewpoint, we examine the viability of CO₂-neutral transportation using hydrocarbon or alcohol fuels, in which the CO₂ product is captured on-board the vehicle. This approach takes advantage of the unparalleled energy density of carbon-based fuels as needed for these energy-intensive applications. A concept is developed considering the power technologies, infrastructure, and fuels required. Storage volume and mass requirements are calculated for a wide range of vehicle types and compared with those for other CO₂-neutral options, namely hydrogen fuel cell vehicles (H2FCVs) and battery electric vehicles (BEVs), and research and development needs to implement this technology are discussed.

Significant inroads have been made in efforts to decarbonize transportation (globally, responsible for 22% of yearly anthropogenic CO₂), but commercialization has been mainly limited to light-duty, short-range vehicles, responsible for approximately half of the emissions from the sector.(1,2) For this subsector, a recent Princeton report, Net-Zero America (NZA), which details a range of pathways to reach CO₂ neutrality by 2050, envisions rapid growth in the use of BEVs alongside major expansion in renewable electricity production.(2) The majority of the remaining emissions in the sector arise from vehicles considered difficult to decarbonize, e.g., those for freight transport and aviation (4% and 2% of global CO₂, respectively). Here, sufficient battery capacity is problematic, and the NZA report instead proposes comparatively more scalable hydrogen to be utilized via H2FCVs.

Where practical, BEVs provide by far the best efficiency utilizing renewable electricity, ∼77% delivered to wheels. For the remaining applications, H2FCVs with hydrogen derived from biomass gasification or electrolysis, the main production pathways as slated by the NZA report, are relatively inefficient, ∼26% and 33% delivered to wheels, respectively.(2,3) Such low efficiencies will be problematic because they require the production of much greater amounts of renewable energy upstream. Major hydrogen production and distribution infrastructure must already be in place before such vehicles are serviceable, with carbon-neutral processes eventually needing to take over market share. And while hydrogen offers impressive gravimetric specific energy, its low volumetric energy density is still a challenge, requiring energy-intensive compression to be feasible for most applications.

Here we assess a different approach, in which C-based fuels are used but with direct on-board CO₂ capture during operation. Shown schematically in Figure 1, efficiency is considerably improved over H2FCVs by avoiding the need to first convert such fuels to hydrogen. C-based fuels have the well-known advantage of markedly higher energy density than either compressed H₂ or Li-ion batteries; they also have an existing, well-developed distribution infrastructure. As shown in Figure 1, the CO₂ captured on vehicles could be returned to a CO₂ distribution network where, after sequestration, the cycle is CO₂-neutral for fossil fuels and CO₂-negative for biofuels. Another route, recycling the CO₂ back into fuel via electrolytic processes, is also possible.

Figure 1. Schematic illustration of a carbon capture fuel cell vehicle (CCFCV) and associated infrastructure. The vehicle includes a solid oxide fuel cell (SOFC) for efficient electrical generation from hydrocarbon or alcohol fuels. Fueling can be done with any of the following: biofuels, fossil fuels, or electrolytic fuels produced using renewable electricity. The captured CO₂ can be stored in a separate tank or in a unified tank with a movable partition, as shown, to minimize net storage volume. After offloading, the CO₂ can be either used in electrolytic fuel production or sequestered. Different infrastructure designs and fuel choices can yield an overall CO₂ impact ranging from mitigatory to net negative.

The vehicle illustrated in Figure 1 is referred to here as a carbon capture fuel cell vehicle (CCFCV). The solid oxide fuel cell (SOFC), shown in the vehicle inlay, is the most desirable choice for vehicle power generation with C-based fuels because it acts as a membrane air separator that combusts fuels with pure oxygen. This is necessary to maintain reasonable tank volumes—combustion with air would dilute the CO₂ with large amounts of nitrogen and thus require prohibitively large tank volumes, which, due to differing gas densities, would be around 20 times that for CO₂ alone.(4) Although separate fuel and CO₂ tanks could be used, net volume requirements can be further reduced by storing the concentrated CO₂ product stream in the volume made available by spent fuel, e.g., using a tank with a movable partition, as illustrated in Figure 1. Note that the use of SOFCs as auxiliary power units, range extenders, or the primary power source in vehicles is already seeing rapidly growing interest.(5−8)

SOFCs are able to work with minimally reformed hydrocarbon and alcohol fuels, while providing fuel-to-electricity conversion efficiency of 50–60%;(9) given a typical electric motor efficiency of 95%, the net fuel-to-wheels efficiency (47–57%) is substantially higher than for typical transportation heat engines (10–40%).(2) Assuming bioenergy-intensive pathways, the fuel flexibility of the SOFC allows it to operate on higher production efficiency biofuels (e.g., up to 85% for bioethanol)(10) versus biohydrogen (up to 60%),(3) resulting in net renewables-to-wheels efficiencies of ∼44% for the CCFCV versus ∼26% for H2FCVs. On the other hand, assuming high electrofuel pathways, the net renewables-to-wheels efficiencies of the CCFCV and H2FCV are similar, but they are substantially lower than for BEVs.(2) READ MORE

Comments are closed.

Advanced BioFuels USA