41,790 research outputs found
Assessment on the Efficiency of an Active Solar Thermal Facade: Study of the Effect of Dynamic Parameters and Experimental Analysis When Coupled/Uncoupled to a Heat Pump
The building sector presents poor performance in terms of energy efficiency and is looking for effective alternatives aimed at reducing the use of fossil fuels. The facade is a key element able to harness renewable energy as an Active Solar Thermal Facade (ASTF). The main purpose of this study is the assessment of a novel design concept based on a steel sandwich panel technology. The performance of the active system will be first addressed by a parametric study in order to analyze its behavior and secondly, by describing a real case based on an experimental test by connecting the active panels to a heat pump. The study shows the impact of solar irradiation and mass flow on the thermal jump achieved, while ambient and fluid inlet temperatures are the most influencing parameters in the efficiency of the facade. When coupled to the heat pump, results from a measurement campaign demonstrate a remarkable improvement in the performance of the ASTF. The results presented provide significant proof about the benefits of a synergetic combination of both technologies—solar facades and heat pumps—as efficient alternatives for the building sector, aiming to improve energy efficiency as well as reduce their dependence on non-renewable sources.This research was partially funded by the Basque Government through IT781-13 and IT1314-19 research
groups and by the University of the Basque Country UPV/EHU through PES17/25. Additionally, TECNALIA
Research & Innovation supported the research activities research through a cooperation agreement (PT10516) with
UPV/EHU
Transforming Energy Networks via Peer to Peer Energy Trading: Potential of Game Theoretic Approaches
Peer-to-peer (P2P) energy trading has emerged as a next-generation energy
management mechanism for the smart grid that enables each prosumer of the
network to participate in energy trading with one another and the grid. This
poses a significant challenge in terms of modeling the decision-making process
of each participant with conflicting interest and motivating prosumers to
participate in energy trading and to cooperate, if necessary, for achieving
different energy management goals. Therefore, such decision-making process
needs to be built on solid mathematical and signal processing tools that can
ensure an efficient operation of the smart grid. This paper provides an
overview of the use of game theoretic approaches for P2P energy trading as a
feasible and effective means of energy management. As such, we discuss various
games and auction theoretic approaches by following a systematic classification
to provide information on the importance of game theory for smart energy
research. Then, the paper focuses on the P2P energy trading describing its key
features and giving an introduction to an existing P2P testbed. Further, the
paper zooms into the detail of some specific game and auction theoretic models
that have recently been used in P2P energy trading and discusses some important
finding of these schemes.Comment: 38 pages, single column, double spac
Power quality and electromagnetic compatibility: special report, session 2
The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems.
Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages).
The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks:
Block 1: Electric and Magnetic Fields, EMC, Earthing systems
Block 2: Harmonics
Block 3: Voltage Variation
Block 4: Power Quality Monitoring
Two Round Tables will be organised:
- Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13)
- Reliability Benchmarking - why we should do it? What should be done in future? (RT 15
Synchronous power controller merits for dynamic stability improvement in long line by renewables
Postprint (author's final draft
Magneto-acoustic wave energy from numerical simulations of an observed sunspot umbra
We aim at reproducing the height dependence of sunspot wave signatures
obtained from spectropolarimetric observations through 3D MHD numerical
simulations. A magneto-static sunspot model based on the properties of the
observed sunspot is constructed and perturbed at the photosphere introducing
the fluctuations measured with the \SiI\ 10827 \AA\ line. The results
of the simulations are compared with the oscillations observed simultaneously
at different heights from the \HeI\ 10830 \AA\ line, the \CaIIH\ core
and the \FeI\ blends in the wings of the \CaIIH\ line. The simulations show a
remarkable agreement with the observations. They reproduce the velocity maps
and power spectra at the formation heights of the observed lines, as well as
the phase and amplification spectra between several pair of lines. We find that
the stronger shocks at the chromosphere are accompanied with a delay between
the observed signal and the simulated one at the corresponding height,
indicating that shocks shift the formation height of the chromospheric lines to
higher layers. Since the simulated wave propagation matches very well the
properties of the observed one, we are able to use the numerical calculations
to quantify the energy contribution of the magneto-acoustic waves to the
chromospheric heating in sunspots. Our findings indicate that the energy
supplied by these waves is too low to balance the chromospheric radiative
losses. The energy contained at the formation height of the lowermost \SiI\
10827 \AA\ line in the form of slow magneto-acoustic waves is already
insufficient to heat the higher layers, and the acoustic energy which reaches
the chromosphere is around 3-9 times lower than the required amount of energy.
The contribution of the magnetic energy is even lower.Comment: Accepted for publication in The Astrophysical Journa
Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications
An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics
Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications
An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics
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EcoBlock: Grid Impacts, Scaling, and Resilience
Widespread deployment of EcoBlocks has the potential to transform today's electricity system into one that is more resilient, flexible, efficient and sustainable. In this vision, the system will consist of self- su cient, renewable-powered, block-scale entities that can deliberately adjust their net power exchange and can optimize performance, maintain stability, support each other, or disconnect entirely from the grid as needed. This report is intended as an independent analysis of the potential relationships, both constructive and adverse, between EcoBlocks and the grid
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