Technology options for onboard hydrogen storage

The development of effective hydrogen storage systems remains a key technical challenge to the extensive use of hydrogen as an energy carrier. The most established methods of storing hydrogen are as a cryogenic liquid and as a high-pressure compressed gas. However, these conventional technologies are restricted by the high energy cost of the liquefaction and compression processes, and by their low volumetric hydrogen densities. In the past 40 years considerable research efforts have focussed on the encapsulation of hydrogen in metal hydrides but the competitiveness of the higher capacity metal hydrides, such as the magnesium-based alloys, has been hampered by sluggish sorption kinetics. In recent years hydrogen storage researchers have broadened the scope of potential materials under investigation to include complex hydrides and other advanced nanomaterials, such as nanostructured carbons and metal-oxide frameworks. This paper presents a review of the most mature of the hydrogen storage technologies, being compressed gas, cryogenic liquid and metal hydrides, and discusses promising directions in the search for suitable hydrogen storage materials

Waste materials as precursors for supercapacitor electrodes

This work highlights the potential to use waste biomass to produce electrodes for cost-effective energy storage systems based on renewable resources. Porous carbon electrodes for supercapacitors were prepared from waste coffee grounds, sugar cane bagasse, pine wood sawdust, and sucrose by activation with ZnCl2. The double-layer capacitances of these carbon electrodes were evaluated in two-electrode supercapacitor cells with 1 M H2SO4. The choice of carbon precursor and activation conditions determine the electrochemical performance, with surface area, pore size distribution, electrical conductivity, and electrochemically active surface functional groups all affecting specific capacitance. The activated carbons from sucrose, pinewood and coffee grounds all exhibited good electrochemical capacitance and stable cycling performance in H2SO4. The activated carbon from coffee grounds achieved the highest specific capacitances at low current loads, with capacitances as high as 368 F g-1 in H2SO4. The good electrochemical performance of the carbons from sucrose, pinewood and coffee grounds is predominantly attributed to well developed pore structures. Although the bagasse carbon has a surface area of 1155 m2 g-1, the bagasse carbons achieved lower specific capacitance and poor stability due to residue silica and ash content

Emission characteristics of polymer additive mixed diesel-sunflower biodiesel fuel

Combustion of fossil fuels has a significant share in producing harmful emissions in the global emission context. With a threat of fossil fuel crisis and the necessity of reducing emission from diesel engine combustion system, biodiesel is considered as one of the key environmentally-friendly diesel fuel alternatives. In this study, sunflower biodiesel has been considered as a key ingredient to infuse waste plastic (polystyrene, PS) as another cleaner source of hydrocarbon fuel in the diesel engines. Polystyrene was infused (5% w/v) into sunflower biodiesel to produce a blend of diesel-biodiesel-polymer (DBP) fuel. The emission characteristics of the diesel, diesel–biodiesel (binary blend) and diesel-biodiesel-polymer (ternary blend) were compared in an unmodified diesel engine. The results showed that the emission compositions of the DBP were comparable to those of diesel which effectively reduced the NOx emission, as compared to diesel-biodiesel blend. In addition, the brake specific fuel consumption (BSFC) and CO emission were reduced in DBP, as compared to biodiesel and diesel fuels. Based on these results, it can be concluded that the polymer blended fuels could be potentially used as another emission reducing fuel source in an unmodified diesel engine. The utilisation of waste polymers in biodiesel production could help find an alternative use for non-recyclable plastics, while also contributing to cleaner emission

Kinetic-and thermodynamic-based improvements of lithium borohydride incorporated into activated carbon

LiBH4 was incorporated into an activated carbon (AC) scaffold using a chemical impregnation method. Confinement of LiBH4 within the carbon nanopores was found to significantly improve both the hydrogen sorption kinetics and thermodynamics, compared to the bulk hydride. The LiBH4/AC sample starts to release hydrogen from just 220 °C, which is 150 °C lower than the onset dehydrogenation temperature of bulk LiBH4. The dehydrogenation rate of the LiBH4/AC sample was one order of magnitude faster than that of bulk LiBH4. The temperature and hydrogen pressure conditions required for restoring the hydride were also significantly reduced when LiBH4 was incorporated into AC. Preliminary study showed that the dissociation hydrogen pressure of LiBH4 could be enhanced by around one order of magnitude upon incorporating the hydride into AC. X-ray diffraction, Fourier transform infrared spectroscopy and nitrogen adsorption analyses were used to confirm the nanostructure of LiBH4 in the AC scaffold

The removal of CO2 and N-2 from natural gas: A review of conventional and emerging process technologies

This article provides an overview of conventional and developing gas processing technologies for CO2 and N-2 removal from natural gas. We consider process technologies based on absorption, distillation, adsorption, membrane separation and hydrates. For each technology, we describe the fundamental separation mechanisms involved and the commonly applied process flow schemes designed to produce pipeline quality gas (typically 2% CO2