Cornelia Aida Bulucea

Using Exergy to Understand and Improve the Efficiency of Electrical Power Technologies

The benefits are demonstrated of using exergy to understand the efficiencies of electrical power technologies and to assist improvements. Although exergy applications in power systems and electrical technology are uncommon, exergy nevertheless identifies clearly potential reductions in thermodynamic losses and efficiency improvements. Various devices are considered, ranging from simple electrical devices to generation systems for electrical power and for multiple products including electricity, and on to electrically driven. The insights provided by exergy are shown to be more useful than those provided by energy, which are sometimes misleading. Exergy is concluded to have a significant role in assessing and improving the efficiencies of electrical power technologies and systems, and provides a useful tool for engineers and scientists as well as decision and policy makers.

Flapping Wing as an Alternative Method of Harvesting Energy from Wind

In the last decades, the wind energy became more attractive to Romania, and thus many resources are allocated to develop the energetic systems based on wind energy. In this work we have investigated the possibility to harvest the wind energy with an actively controlled pitch-plunge aeroelastic system. The paper present some theoretical considerations and results regarding oscillating wing.

The Exergetic and Environmental Impact Assessment of Underground Electric Train Braking

Within the present industrial society, some of the greatest challenges of humanity are related to achieving a sustainable industrial metabolism, which integrates technical activity and ecological systems. Electric traction drive systems using induction motors fed by variable voltage variable frequency (VVVF) inverters have provided high performance for urban electric trains. Moreover, power converter technology based on advanced techniques in control electronics and efficient anti-slip systems allows optimum traction characteristics and minimum energy consumption. For underground electric trains, however, it is also important to assess the environmental impact of braking. From the viewpoint of exergy and environment, the braking regime, particularly electric braking, is a special aspect of non-autonomous vehicles using electric traction. As electric drive systems are used with VVVF inverters and traction induction motors, these machines with appropriate controls can realize both traction and electric braking regimes for electric traction vehicles. Concerns regarding mechanical braking are associated with unrecovered energy and material utilization. Also, for underground electric trains during mechanical braking, the abnormal but frequent situation involving the unequal charge of the traction induction motors is a concern. These aspects of underground electric trains are analysed in this article so as to assist in improving performance.

Utilizing the Exergy Concept to Address Environmental Challenges of Electric Systems

Theoretically, the concepts of energy, entropy, exergy and embodied energy are founded in the fields of thermodynamics and physics. Yet, over decades these concepts have been applied in numerous fields of science and engineering, playing a key role in the analysis of processes, systems and devices in which energy transfers and energy transformations occur. The research reported here aims to demonstrate, in terms of sustainability, the usefulness of the embodied energy and exergy concepts for analyzing electric devices which convert energy, particularly the electromagnet. This study relies on a dualist view, incorporating technical and environmental dimensions. The information provided by energy assessments is shown to be less useful than that provided by exergy and prone to be misleading. The electromagnet force and torque (representing the driving force of output exergy), accepted as both environmental and technical quantities, are expressed as a function of the electric current and the magnetic field, supporting the view of the necessity of discerning interrelations between science and the environment. This research suggests that a useful step in assessing the viability of electric devices in concert with ecological systems might be to view the magnetic flux density B and the electric current intensity I as environmental parameters. In line with this idea the study encompasses an overview of potential human health risks and effects of extremely low frequency electromagnetic fields (ELF EMFs) caused by the operation of electric systems. It is concluded that exergy has a significant role to play in evaluating and increasing the efficiencies of electrical technologies and systems. This article also aims to demonstrate the need for joint efforts by researchers in electric and environmental engineering, and in medicine and health fields, for enhancing knowledge of the impacts of environmental ELF EMFs on humans and other life forms.