Superconductivity and Hydrogen Economy : A Roadmap to Synergy

Hydrogen as an energy carrier is a promising alternative to fossil fuels, and it becomes more and more popular in developed countries as a carbon-free fuel. The low boiling temperature of hydrogen (20 K or −253.15 °C) provides a unique opportunity to implement superconductors with a critical temperature above 20 K such as MgB2 or high-temperature superconductors. Superconductors increase efficiency and reduce the loss of energy, which could compensate for the high price of LH2 to some extent. Norway is one of the pioneer countries with adequate infrastructure for using liquid hydrogen in the industry, especially in marine technology where a superconducting propulsion system can make a remarkable impact on its economy. Using superconductors in the motor of a propulsion system can increase its efficiency from 95% to 98% when the motor operates at full power. The difference in efficiency is even greater when the motor does not work at full power. Here, we survey the applications of liquid hydrogen and superconductors and propose a realistic roadmap for their synergy, specifically for the Norwegian economy in the marine industry.publishedVersionPeer reviewe

Simulation of Hydrogen Tank Refuelling

As an alternative to fossil fuels and as a sustainable energy carrier, there are considerable interestsin investigating hydrogen. Hence, it seems significant to evaluate the behavior of hydrogen in refueling or storing. The most important issue in refueling the tank pertains to the temperature. The hydrogen inside the tank heats up during the filling due to the effect of compression and negative Joule-Thomson coefficient. As a result, the main aim of this project is to examine the temperature inside the tank to not exceed 85°C in order to avoid cracking in the wall and consequently, further possible disasters. This can be done by implementing simulation with a proper software. OpenFoam is an appropriate software to consider such behaviors and it contributes to developing and considering the variety of properties including the temperature inside the tank. The cylindrical geometry is created with blockMesh in 3D while the geometry ends up with rectangular cubic in 2D. The proper boundary conditions and initial properties are set up in rhoCentralFoam solver to establish simulations in OpenFoam 5.0. According to the obtained results, it is found out that it seems necessary to precool inlet hydrogen to fulfill the main purpose of this project. The bigger inlet area also decreases the maximum temperature inside the tank however this effect is not that much considerable compared to precooling. A further point to add is that the position of the inlet can play a significant role in the final temperature. Acquired results prove that the direction of inlet velocity should be aligned with the length of cylinder otherwise the temperature increases significantly. At last, comparing the final results to what was calculated and expected reveals that the results have an acceptable concordance and consistency. So, it can be deduced that the simulations have been done properly and the results can be trusted for further studies or possible experiments

Using magnetic nanoparticles to improve flux pinning in YBa2Cu3Ox films

Superconductors application can lead to significant economic benefits, especially in combination with use of liquid hydrogen, which is becoming an important part of the renewable energy economy. While many traditional superconductors cannot operate in liquid hydrogen, new materials, like high-temperature superconductors and MgB2 perfectly suit this purpose. YBa 2 Cu 3 O x is one of the most used high-temperature superconductors. It can operate even in liquid nitrogen, at the temperature of 77.3 K, but has a strong advantage of enhanced critical current density at the boiling temperature of liquid hydrogen of 20 K. A disadvantage of this material is the absence of natural c-axis pinning centers defining its critical current density. A usual way to solve this problem is the introduction of artificial pinning centers in the form of nanoparticles. The nanoparticles, however, reduce the volume of the superconductor and can lead to the formation of high-angle grain boundaries detrimental for the critical current. Here we explore an approach of depositing magnetic nanoparticles on the surface of superconducting films, which neither reduce the volume of the superconductor nor create high-angle grain boundaries. The additional pinning by these nanoparticles is studied by recording magneto-optical images of the films

Experimental and computational studies of circulating fluidized bed

Biomass gasification represents an efficient process for the production of power, heat and biofuels. Different technologies are used for gasification and this article focuses on a circulating fluidized bed (CFB) system. Understanding the behaviour of particles is of primary importance and a cold flow CFB experimental unit was constructed and tested. The particle circulation rate is greatly affected by the loop seal performance, and therefore the loop seal should be properly optimized to maintain an uninterrupted operation. Smooth flow regimes were obtained for the CFB by varying the loop seal aeration rates. Particles with size 850–1000 µm and 1000–1180 µm were chosen for the experiments. The minimum flow rates of air into the riser for the two particle sizes were found to be 1.3 and 1.5 Sm3/ min, respectively. To obtain a smooth flow regime, a velocity range for aeration in the loop seal was found for the two particle sizes. Based on the experimental results, combinations of flow rates were suggested for the simulations. A Computational Particle Fluid Dynamic (CPFD) model was developed using Barracuda VR, and the model was validated against experimental results. The simulated results for the system regarding the pressure and the height of the bed material in the standpipe agreed well with the experimental results. The deviation between the experimental and computational pressure was less than 0.5% at all the locations for both the particle sizes. The deviation in particle level was about 6% for the 850–1000 µm particles and 17% for the 1000–1150 µm particles. Both the experiments and the simulations predicted that a small fraction of the circulating sands are emitted from the top of the rig. The validated CPFD model was further used to predict the flow behaviour and the particle circulation rate in the CFB