Laurentiu Constantin Lipan

By Lucian Pîslaru‐Dănescu and Lipan Laurențiu Constantin

This study presents an apparatus for the measurement of the electrical volume resistivity of concrete structures in civil and industrial constructions in 2.5 accuracy class, which operates at 500 Hz, for measuring the in situ resistivity of concrete in the range of 5–100 Ωm that is immune to errors due to the polarization phenomena at the interface probe/concrete sample. Also, a quench protection active system (QPS), which works in tandem with a superconducting coil structures (SCSs), in order to prevent the damaging effects when the coil structures pass from the superconducting state into normal conduction state (quench), is presented. An SCS made of YBCO tape high‐temperature superconductor (HTS) type, with a critical temperature of 92 K, has been experimented. In order to minimize the heat transfer influx by convection, the SCSs are confined to a cryostat, which is vacuumed at about 0.001 mbar. The working temperature of the HTS coil structures is about 77 K, ensured by liquid nitrogen as cryogenic agent. Finally, the measurement of the electrical resistance of the sensing element (SE) as part of the resistive‐type gas sensor is shown. The SE is placed on a Wheatstone bridge. The electrical resistance of the SE is variable by an amount ΔR, on when all the resistances of a Wheatstone bridge are nominally equal.

Part of the book: Electrical Resistivity and Conductivity

By Lucian Pîslaru-Dănescu and Lipan Laurențiu Constantin

This study starts with the ZnO nanostructured materials used for improve the efficiency of polycrystalline solar cells operation under low solar radiation conditions. The ZnO nanowires were prepared using the hydrothermal method of deposition on the seed layer by a new and complex process, with controllable morphological and optical properties. The analysis of the XRD patterns, scanning electron microscopy images (SEM) of the ZnO nanowires and a lot of tests made Pasan Meyer Burger HighLight 3 solar simulator, confirm the advantages of using the ZnO nanowires in solar cells applications for antireflection coatings. Then, piezoelectric structures based on new modified PZT zirconate titanate designed for energy harvesting applications is presented. Based on their piezoelectric characteristics, modified PZT zirconate titanate ceramics made of Pb(Zr0.53Ti0.47)0.99Nb0.01O3 ceramic have efficient applications in energy harvesting devices. A piezoelectric transducer, consisting of a thin plate of this piezoceramic material, with dimensions (34 mm × 14 mm × 1 mm), is illustrated. A multiphysics numerical simulation further illustrates such piezoelectric transducer operation. Finally, the miniature planar transformer with circular spiral winding and hybrid core—ferrite and magnetic nanofluid, designed for new energy harvesting systems is presented. We purpose now that the magnetic nanofluid be used both as a coolant and as part of the hybrid magnetic core.

Part of the book: Advanced Electronic Circuits

By Lucian Pîslaru-Dănescu and Laurențiu Constantin Lipan

The continuity of power supply to users is considered to be one of the main problems in the design and implementation of low-voltage smart microgrid configurations. Switching to the backup power supply, when using two frequency converters, one of which is alternately maintained in cold reserve, is presented. Switching to the backup power supply, in the case of low-voltage symmetrical smart microgrids, is another highlighted aspect. In the case of modern residential buildings, the automatic switching is necessary between two or more types of users, critical and noncritical ones to the available sources, like the public grid, photovoltaic panels, power generator, etc. Also, in this study, the implementation of smart power microgrids, featuring auto-reconfiguration, is proposed. It is considered the conversion of the public grids to active (distribution/using) smart power microgrids, which have the autoconfiguration option and use high-tech smart devices, like recloser type. Thus, the faults and contingencies will be limited or even removed, creating the frame for the supplied equipment (in a continuously increasing number due to the local and regional expansion) to operate until the removal of the fault.

Part of the book: Smart Microgrids

By Laurentiu Constantin Lipan

Greenhouse gas emissions and climate change are currently major international problems. This makes it important to increase energy efficiency. The implementation of energy efficiency improvement measures has reduced energy demand for industrial platforms, so that energy plans designed before these measures are no longer appropriate for current tasks (extensions are not considered at this time). I intended to give a clear image and a better understanding of the factories’ power consumption (the industrial area in question is located near a city). A power plant-specific power system is quite disruptive, as can be seen from the monitored data at the power plant users and from the general power supply voltage bars (110 kV, 20 kV) as well as from the voltage bars of the adjacent users. Based on real-time measurements and monitoring devices, the following characteristic curves have been extracted for local energy systems. That is because data analysis is easy to be used for monitoring energy efficiency and elaborating optimization measures to improve power performance.

Part of the book: Alternative Energies and Efficiency Evaluation

By Laurentiu Constantin Lipan and Sorin Dimitriu

Romania is one of the European countries that has a rich geothermal potential, the main uses of this resource being the spaces heating and thermal baths. Recently, concerns about increasing energy efficiency and limiting greenhouse gas emissions, have determined an increased attention to heating systems using geothermal water. These will play an important role in the future in developing sustainable energies and reducing the use of fossil fuels. The authors present a case study on a heating system in the city of Călimănești, initially using liquid fuel, which was modernized by using geothermal hot water for the preparation of the thermal agent. As geothermal water, with an initial temperature of 95°C, cannot be cooled below 50°C, the authors considered the possibility of using a heat pump to fully exploit the thermal potential of geothermal water, increase the capacity of the system and increase its energy efficiency. The implementation of the heat pump in the district heating system and the results expected to be obtained are discussed. It was considered that the heat pump works in parallel with the heating system, obtaining an increase in its capacity by approx. 60% and an increase in energy efficiency by approx. 30%.

Part of the book: Sustainable Smart Cities