Microbial Fuel Cell for Wastewater Treatment as Power Plant in Smart Grids: Utopia or Reality?

Microbial fuel cells (MFCs) have undergone great technological development in the last 20 years, but very little has been done to commercialize them. The simultaneous power production and wastewater treatment are features those greatly increase the interest in the use of MFCs. This kind of distributed power generation is renewable and friendly and can be easily integrated into a smart grid. However, there are some key issues with their commercialization: high construction costs, difficulty in developing high power structures, MFC lifespan, and maintaining a high level of efficiency. The objective of this article is to explore the possibilities of using MFCs in urban wastewater not only regarding the technical criteria of their application, but also mainly from an economic point of view, to determine the conditions through which the viability of the investment is ensured and the possibilities of their integration in a smart grid are identified. Initially, this article explores the implementation/configuration of a power plant with MFCs within an urban wastewater treatment plant on a theoretical basis. In addition, based on the corresponding physical quantities for urban wastewater treatment, the construction and operational costs are determined and the viability of the investment is examined based on classic economic criteria such as net present value, benefit–cost ratio, internal rate of return, and discounted payback period. Furthermore, sensitivity analysis is carried out, concerning both technical parameters, such as the percentage of organic matter removal, power density, sewage residence time, MFC efficiency, etc., and economical parameters, such as the reduction of construction costs due to change of materials, change of interest rate, and lifetime. The advantages and disadvantages of their use in smart grids is also analyzed. The results show that the use of MFCs for power generation cannot be utopian as long as they are integrated into the structure of a central wastewater treatment plant on the condition that the scale-up technical issues of MFCs are successfully addressed. Copyright © 2022 Tsekouras, Deligianni, Kanellos, Kontargyri, Kontaxis, Manousakis and Elias

Onboard DC grid employing smart grid technology: challenges, state of the art and future prospects

Summarization: Research in All Electric Ship (AES) and onboard DC grids has already been initiated and it is going to be intensified because of its promising perspectives. This study aims to present in a coherent and methodical way why onboard DC distribution systems, smart grids and AES concept can greatly improve ship efficiency. Emerging technical challenges and future prospects are presented; state of the art is summarised while directions for a complete research roadmap are proposed.Παρουσιάστηκε στο: Electrical Systems in Transportatio

New challenges emerged from the development of more efficient electric energy generation units

Summarization: The current trends in ship technology are turning ships into more energy efficient ones. Thus, the extensive electrification of ship systems, including propulsion, is a most appealing alternative as, the more electrified a ship, the greener and more efficient it turns. In this paper, a brief overview of novel trends regarding electric energy generator schemes is made, and it is shown that these result in new challenges leading to amendments of the traditional concepts dominating over design and operation standards. The discussion is supported by the results of a model comprising a ship generic power grid with multi-type supply units.Παρουσιάστηκε στο: Electric Ship Technologies Symposium , IEE

Design of particular electrical machines by using similarity theory and scale factors

Summarization: Design and operation analysis of electrical machines can be performed by using either full-size or different scale models. This paper deals with the development of electromagnetic field analysis and electrical circuit models of geometrically similar electrical machines based on similarity theory and scale factors. The proposed methodology can be exploited for the design of micro and nano scale electrical machines used in medical and other applications, as it allows the construction of up-scale models more suitable for laboratory measurements.Παρουσιάστηκε στο: Electrical Machines International Conference o

Simplified method for the assessment of ship electric power systems operation cost reduction from energy storage and renewable energy sources integration

Summarization: The extensive electrification of ship power systems has become a very appealing option for the development of more efficient and environmentally friendly ships. Renewable energy sources and energy storage systems will have a key role in such systems as they can lead to fuel consumption reduction and increase of ship efficiency. In this study, analytic formulas are obtained for the estimation of system marginal cost of a ship power system equipped with photovoltaics and energy storage system and its operation is analysed from the economical point of view. The major advantage of the proposed method is that the obtained formulas require almost zero computational capacity although they provide a qualitative view of the problem not easily attainable by other conventional methods. Hence, it could be a convenient tool for the technical-economical study of such systems. In this context, it could be exploited for the assessment of a large number of ship power system operation scenarios during ship design phase.Παρουσιάστηκε στο: Electrical Systems in Transportatio

An effort to formulate frequency modulation constraints in ship-electrical systems with pulsed loads

Summarization: One of the most significant power supply quality problems in ship electric networks is `frequency modulation`. This is a phenomenon most frequently met in extensively electrified ships and it is caused by the operation of certain electric loads, known as `pulsed loads`, which require high power repeated on a regular or random basis. To the best of the authors` knowledge, no well-based theoretical analysis of the phenomenon exists in the literature, although any existing constraints limiting the operation of pulsed loads are not properly explained in the respective standards. Hence, in this study, an effort is made, first to establish a theoretical explanation of the modulation phenomenon via an analytical mathematical expression comprising all the critical parameters that affect it, and then highlight the appropriate procedure of setting limits via standards. In this way, the frequency modulation is expressed as a function of several parameters of the ship electric system. Furthermore, using the obtained expression, a sensitivity analysis of the particular effect of each of these system parameters is made. The proposed method is a useful design tool for ship electric power systems enabling the assessment of acceptable pulsed loading level without the need of complicated simulation models comprising many parameters usually not readily available.Παρουσιάστηκε στο: Electrical Systems in Transportatio

Comparison of ship power systems from an optimal economic operation point of view

Summarization: For many years, the predominant concept on board ships was to have separate propulsion and generator engines. However, more recently, the adoption of hybrid installations with shaft generators, is becoming increasingly common. In this paper, a case study is presented where measurements from actual equipment are used to compare the propulsion and power plants of a typical ship to a hybrid one. Also, a new algorithm for electrical load distribution is introduced and examined in this case.Παρουσιάστηκε στο: Electric Ship Technologies Symposium IEE