Deploying and optimizing performance of a 3D hydrodynamic model on cloud

This papers presents details on deploying the Environmental Fluid Dynamics Code (EFDC) on a container-based cloud environment. Results are compared to a bare metal deployment. Application-specific benchmarking tests are complemented by detailed network tests that evaluate isolated MPI communication protocols both at intra-node and inter-node level with varying degrees of self-contention. Cloud-based simulations report significant performance loss in mean run-times. A containerised environment increases simulation time by up to 50%. More detailed analysis demonstrates that much of this performance penalty is a result of large variance in MPI communciation times. This manifests as simulation runtime variance on container cloud that hinders both simulation run-time and collection of well-defined quality-of-service metrics

A 2D model for hydrodynamics and biology coupling applied to algae growth simulations

Cultivating oleaginous microalgae in specific culturing devices such as raceways is seen as a future way to produce biofuel. The complexity of this process coupling non linear biological activity to hydrodynamics makes the optimization problem very delicate. The large amount of parameters to be taken into account paves the way for a useful mathematical modeling. Due to the heterogeneity of raceways along the depth dimension regarding temperature, light intensity or nutrients availability, we adopt a multilayer approach for hydrodynamics and biology. For free surface hydrodynamics, we use a multilayer Saint-Venant model that allows mass exchanges, forced by a simplified representation of the paddlewheel. Then, starting from an improved Droop model that includes light effect on algae growth, we derive a similar multilayer system for the biological part. A kinetic interpretation of the whole system results in an efficient numerical scheme. We show through numerical simulations in two dimensions that our approach is capable of discriminating between situations of mixed water or calm and heterogeneous pond. Moreover, we exhibit that a posteriori treatment of our velocity fields can provide lagrangian trajectories which are of great interest to assess the actual light pattern perceived by the algal cells and therefore understand its impact on the photosynthesis process.Comment: 27 pages, 11 figure

Biofuels from abandoned mines: A starting point for future developments

Abandoned mines and quarries represent sites with the request of restoration due to their pollution. On the other hand, biofuels represent a response to the present request of sustainable energy, in order to reduce the CO2 emission, in transportation, but also in energy production and domestic use. However, biofuels production seldom requires lands for the biomass cultivation. In this paper, the use of the dismissed mines and quarries is suggested for the cultivation of algae, as biomass production. To support this approach, a theoretical numerical evaluation of a typical dismissed quarry is developed in order to highlight the feasibility of the approach itself

Geographical Assessment of Microalgae Biofuels Potential Incorporating Resource Availability

Previous assessments of the economic feasibility and large-scale productivity of microalgae biofuels have not considered the impacts of land and carbon dioxide (CO2) availability on the scalability of microalgae-based biofuels production. To accurately assess the near-term productivity potential of large-scale microalgae biofuel in the US, a geographically realized growth model was used to simulate microalgae lipid yields based on meteorological data. The resulting lipid productivity potential of Nannochloropsis under large-scale cultivation is combined with land and CO2 resource availability illustrating current geographically feasible production sites and corresponding productivity in the US. Baseline results show that CO2 transport constraints will limit US microalgae based bio-oil production to 4% of the 2030 Department of Energy (DOE) alternative fuel goal. The discussion focuses on synthesis of this large-scale productivity potential results including a sensitivity analysis to land and CO2 resource assumptions, an evaluation of previous modeling efforts and their assumptions regarding the transportation of CO2, the feasibility of microalgae to meet DOE 2030 alternative fuel goals, and a comparison of the productivity potential in several key regions of the US

Investigating the hydrodynamic performance of carbonation sumps in High Rate Algal Pond (HRAP)raceways using computational fluid dynamics (CFD)

The production of microalgae requires carbonation and deoxygenation which is commonly supplied through a sump. This needs to be designed to minimise the energy loss to ensure a high net energy gain from the biofuel. Computational fluid dynamics was used to evaluate different sump designs and flow velocities in terms of energy loss and flow distribution to find the optimum configuration. It was established that increasing the radius of curvature of the corners to 0.1 m and the implantation of one flow deflector resulted in a reduction in hydraulic power of 73% compared to the basic setup. It was apparent that the central baffle resulted in considerable energy loss and when this was removed then a power saving of 95% was possible. There was, however, a much reduced flow around the sump leading to shortened contact time between the gas and fluid which could in turn decrease the carbonation of the fluid. It was also apparent that the use of standard formulas for the calculation of head loss was not applicabl

Energy balance of biogas production from microalgae: Development of an energy and mass balance model

The paper describes the construction of a mechanistic energy balance model for the production of biogas from anaerobic digestion of micro-algal biomass grown in raceways, based on simple principles and taking into account growth, harvesting and energy extraction. The model compares operational energy inputs with the calorific value of the output biomass in terms of the energy return on operational energy invested (EROOI). Initial results indicate that production of microalgal biogas will require: a) Favourable climatic conditions. The production of microalgal biofuel in UK would be energetically challenging at best. b) Achievement of ‘reasonable yields’ equivalent to ~3% photosynthetic efficiency (25 g m-2 day-1). c) Low or no cost and embodied energy sources of CO2 and nutrients from flue gas and wastewater. d) Mesophilic rather than thermophilic digestion. e) Adequate conversion of the organic carbon to biogas (≥ 60%). The model itself provides a powerful assessment tool both for comparison of alternative options and potentially for benchmarking real schemes

Produktivitas Kolam Pembesaran Larva Nila Merah dengan Tanah Dasar Inceptisol yang Dimarel Bahan Ultisol dan Vertisol

A major constraint in the fish farming system in Yogayakarta, Indonesia, isthe low physical fertility of the pond bottom soil, which is made up of the sandyInceptisols. This study aimed to alleviate this constraint by physically mixing itwith Ultisols and Vertisols that have a higher clay content. The Inceptisols wasmixed with Ultisols (I-U) and Vertisols (I-V) with the proportion of (70:30), (50:50), and(30:70). These mixtures were then given basal fertilizer in the form of quaildroppings manure at a dose of 2 tons/ha/month, urea and super phosphate. The fishculture was divided into two systems: ponds with 50 fish/m2 and ponds without fish. Thebest mixture was 30% Inceptisols with 70% Ultisols and 50% Inceptisols with 50%Vertisols with basal fertilizer. These mixtures gave significant improvement inchlorophyll-a concentration, plankton diversity, benthic algae abundance, and fishgrowth

Analysis of mass transfer capacity in raceway reactors

In the present work, a methodology is proposed to determine the mass transfer capacity in existing microalgae raceway reactors to minimize excessive dissolved oxygen accumulation that would otherwise reduce biomass productivity. The methodology has been validated using a 100 m2 raceway reactor operated in semi-continuous mode. The relevance of each raceway reactor section was evaluated as well as the oxygen transfer capacity in the sump to different air flow rates. The results confirm that dissolved oxygen accumulates in raceway reactors if no appropriate mass transfer systems are provided. Therefore, mass transfer in the sump is the main contributor to oxygen removal in these systems. The variation in the volumetric mass transfer coefficient in the sump as a function of the gas flow rate, and therefore the superficial gas velocity in the sump, has been studied and modelled. Moreover, the developed model has been used to estimate the mass transfer requirements in the sump as a function of the target dissolved oxygen concentration and the oxygen production rate. The proposed methodology allows us to determine and optimize the mass transfer capacity in the sump for any existing raceway reactor. Moreover, it is a powerful tool for the optimization of existing reactors as well as for the design optimization of new reactors

A new model to analyze the temperature effect on the microalgae performance at large scale raceway reactors

In this paper a simplified temperature model for raceway reactors is developed, allowing to determine the temperature of the microalgae culture as a function of reactor design and environmental conditions. The model considers the major phenomena taking place in raceway reactors, especially heat absorption by radiation and heat losses by evaporation among others. The characteristic parameters of the model have been calibrated using genetic algorithms, next being validated with a long set of more than 50 days covering different weather conditions. It is worth to highlight the use of the developed model as a tool to analyze the influence of the temperature on the performance of microalgae cultures at large scale. As example, the annual variation of the performance of up to five different microalgae strains has been determined by computing the temperature index, thus the normalized value of performance of whatever microalgae at the real temperature with respect to that achievable at optimal temperature can be established. Results confirm that only strains tolerant to wide ranges of temperature can be efficiently produced all the year around in large scale outdoor raceway reactors without additional temperature control systems

Dynamic modeling of the microalgae cultivation phase for energy production in open raceway ponds and flat panel photobioreactors

A dynamic model of microalgae cultivation phase is presented in this work. Two cultivation technologies are taken into account: the open raceway pond and the flat panel photobioreactor. For each technology, the model is able to evaluate the microalgae areal and volumetric productivity and the energy production and consumption. Differently from the most common existing models in literature, which deal with a specific part of the overall cultivation process, the model presented here includes all physical and chemical quantities that mostly affect microalgae growth: the equation of the specific growth rate for the microalgae is influenced by CO2 and nutrients concentration in the water, light intensity, temperature of the water in the reactor, and by the microalgae species being considered. All these input parameters can be tuned to obtain reliable predictions. A comparison with experimental data taken from the literature shows that the predictions are consistent and slightly overestimating the productivity in the case of closed photobioreactor. The results obtained by the simulation runs are consistent with those found in literature, being the areal productivity for the open raceway pond between 50 and 70 t/(ha × year) in Southern Spain (Sevilla) and Brazil (Petrolina) and between 250 and 350 t/(ha × year) for the flat panel photobioreactor in the same locations