Entropy generation minimization (finite time thermodynamics, or thermodynamic optimization) is the method that combines into simple models the most basic concepts of heat transfer, fluid mechanics, and thermodynamics. These simple models are used in the optimization of real (irreversible) devices and processes, subject to finite‐size and finite‐time constraints. The review traces the development and adoption of the method in several sectors of mainstream thermal engineering and science: cryogenics, heat transfer, education, storage systems, solar power plants, nuclear and fossil power plants, and refrigerators. Emphasis is placed on the fundamental and technological importance of the optimization method and its results, the pedagogical merits of the method, and the chronological development of the field.

Entropy generation minimization: The new thermodynamics of finite-size devices and finite-time processes

As the fossil fuels are depleting day by day, there is a need to find out an alternative fuel to fulfill the energy demand of the world. Biodiesel is one of the best available resources that have come to the forefront recently. In this paper, a detailed review has been conducted to highlight different related aspects to biodiesel industry. These aspects include, biodiesel feedstocks, extraction and production methods, properties and qualities of biodiesel, problems and potential solutions of using vegetable oil, advantages and disadvantages of biodiesel, the economical viability and finally the future of biodiesel. The literature reviewed was selective and critical. Highly rated journals in scientific indexes were the preferred choice, although other non-indexed publications, such as Scientific Research and Essays or some internal reports from highly reputed organizations such as International Energy Agency (IEA), Energy Information Administration (EIA) and British Petroleum (BP) have also been cited. Based on the overview presented, it is clear that the search for beneficial biodiesel sources should focus on feedstocks that do not compete with food crops, do not lead to land-clearing and provide greenhouse-gas reductions. These feedstocks include non-edible oils such as Jatropha curcas and Calophyllum inophyllum , and more recently microalgae and genetically engineered plants such as poplar and switchgrass have emerged to be very promising feedstocks for biodiesel production. It has been found that feedstock alone represents more than 75% of the overall biodiesel production cost. Therefore, selecting the best feedstock is vital to ensure low production cost. It has also been found that the continuity in transesterification process is another choice to minimize the production cost. Biodiesel is currently not economically feasible, and more research and technological development are needed. Thus supporting policies are important to promote biodiesel research and make their prices competitive with other conventional sources of energy. Currently, biodiesel can be more effective if used as a complement to other energy sources.

A comprehensive review on biodiesel as an alternative energy resource and its characteristics

http://biodiesel.persiangig.com/Cultivation/(3)Microalgae%20biofuels-%20A%20critical%20review%20of%20issues,%20problems%20and%20the%20way%20forward%20Review%20Article.pdf

Microalgae biofuels: A critical review of issues, problems and the way forward

https://openscholar.dut.ac.za/bitstream/10321/1400/1/rawat__kumar__mutanda___bux_2013_aplplied_energy.pdf

Biodiesel from microalgae: A critical evaluation from laboratory to large scale production

The economically significant production of carbon-neutral biodiesel from microalgae has been hailed as the ultimate alternative to depleting resources of petro-diesel due to its high cellular concentration of lipids, resources and economic sustainability and overall potential advantages over other sources of biofuels. Pertinent questions however need to be answered on the commercial viability of large scale production of biodiesel from microalgae. Vital steps need to be critically analysed at each stage. Isolation of microalgae should be based on the question of whether marine or freshwater microalgae, cultures from collections or indigenous wild types are best suited for large scale production. Furthermore, the determination of initial sampling points play a pivotal role in the determination of strain selection as well as strain viability. The screening process should identify, purify and select lipid producing strains. Are natural strains or stressed strains higher in lipid productivity? The synergistic interactions that occur naturally between algae and other microorganisms cannot be ignored. A lot of literature is available on the downstream processing of microalgae but a few reports are available on the upstream processing of microalgae for biomass and lipid production for biodiesel production. We present in this review an empirical and critical analysis on the potential of translating research findings from laboratory scale trials to full scale application. The move from laboratory to large scale microalgal cultivation requires careful planning. It is imperative to do extensive pre-pilot demonstration trials and formulate a suitable trajectory for possible data extrapolation for large scale experimental designs. The pros and cons of the two widely used methods for growing microalgae by photobioreactors or open raceway ponds are discussed in detail. In addition, current methods for biomass harvesting and lipid extraction are critically evaluated. This would be novel approach to economical biodiesel production from microalgae in the near future. Globally, microalgae are largest biomass producers having higher neutral lipid content outcompeting terrestrial plants for biofuel production. However, the viscosities of microalgal oils are usually higher than that of petroleum diesel.

Biodiesel from microalgae: a critical evaluation from laboratory to large scale production. Appl Energy

Variables affecting the in situ transesterification of microalgae lipids

Anaerobic digestion of microalgae residues resulting from the biodiesel production process

Second law analysis of combined heat and mass transfer in internal and external flows

Second law analysis of combined heat and mass transfer phenomena

For the design of energy efficient dryers employing heat pump systems, the dynamic response of the product to the kiln conditions must be taken into account. In this paper, the formulation of a dynamic, kiln-wide drying model is described. The model solves the unsteady-state mass, momentum and energy balance equations for both the air flow and the wood boards in drying three types of stack: normal stack, aligned stack and staggered stack. In order to represent the dynamical response of the system, the model equations provide more complete energy and mass balances than those presented in recent publications. The transient profiles of the air humidity, temperature, pressure, and velocity, and the wood temperature and moisture content along the air flow direction within the stack are obtained using this model. To illustrate the use of the model, the drying processes of sapwood boards of Pinus radiata under typical dehumidifier kiln conditions have been calculated, and the modelled results have been discussed in detail. In addition, the model has been tested by using the performance data for a commercial scale kiln. The agreement between the modelled and measured performance results shows that the model is suitable for the design and analysis of dehumidifier wood dryers.

C.G. Carrington

Papers

Variables affecting the in situ transesterification of microalgae lipids

Anaerobic digestion of microalgae residues resulting from the biodiesel production process

Second law analysis of combined heat and mass transfer in internal and external flows

Second law analysis of combined heat and mass transfer phenomena

Dynamic Modelling of the Wood Stack in a Wood Drying Kiln