An electric arc-furnace is a complex industry which demands high levels of electrical energy in order to heat iron materials and other additives needed for the production of cast iron and/or steelmaking. The cost of the electrical energy demanded by the factory during the production can be greater than 20% of the overall cost. This kind of arc-furnace allows the production of steel with levels of scrap metal feedstock up to 100%. From an electrical point of view, the factory size in terms of its maximum apparent power demanded from the grid is designed to make use of the static capacity of the transmission line that supplies the energy. In that case, it is not possible to increase the power of the factory above the static rating by adding new facilites without installing new transmission infrastructures. This paper presents a methodology that allows an increase in net power of an arc-furnace factory without installing new transmission lines. The novelty of the proposed solution is based on a mix strategy that combines Demand-Side Management (DSM) methodologies and the use of ampacity techniques according IEEE 738 and CIGRE TB601.
The application of DSM methodologies provides an improvement in the sustainability of not only the industrial customer but also in the overall grid. As a secondary effect, it reduces operational costs and the greenhouse gas emissions.
The proposed methodology has been tested in an arc-furnace factory located in the North of Spain.

Predictive maintenance strategies in power transformers aim to assess the risk through the calculation and monitoring of the health index of the power transformers. The parameter most used in predictive maintenance and to calculate the health index of power transformers is the dissolved gas analysis (DGA). The current tendency is the use of online DGA monitoring equipment while continuing to perform analyses in the laboratory. Although the DGA is well known, there is a lack of published experimental data beyond that in the guides. This study used the nearest-rank method for obtaining the typical gas concentration values and the typical rates of gas increase from a transformer population to establish the optimal sampling interval and alarm thresholds of the continuous monitoring devices for each power transformer. The percentiles calculated by the nearest-rank method were within the ranges of the percentiles obtained using the R software, so this simple method was validated for this study. The results obtained show that the calculated concentration limits are within the range of or very close to those proposed in IEEE C57.104-2019 and IEC 60599:2015. The sampling intervals calculated for each transformer were not correct in all cases since the trend of the historical DGA samples modified the severity of the calculated intervals.

Power transformers are the most important assets of electric power substations. The reliability in the operation of electric power transmission and distribution is due to the correct operation and maintenance of power transformers. The parameters that are most used to assess the health status of power transformers are dissolved gas analysis (DGA), oil quality analysis (OQA) and content of furfuraldehydes (FFA) in oil. The parameter that currently allows for simple online monitoring in an energized transformer is the DGA. Although most of the DGA continues to be done in the laboratory, the trend is online DGA monitoring, since it allows for detection or diagnosis of the faults throughout the life of the power transformers. This study presents a review of the main DGA monitors, single- or multi-gas, their most important specifications, accuracy, repeatability and measurement range, the types of installation, valve or closed loop, and number of analogue inputs and outputs. This review shows the differences between the main existing DGA monitors and aims to help in the selection of the most suitable DGA monitoring approach according to the needs of each case.

The increase in energy efficiency of power systems and the development of smart grids are strongly based on new and more accurate ways of monitoring. In overhead power line systems, the focus is on monitoring weather conditions and the main line parameters, such as the current and temperature of the conductor. Current and temperature are linked by the Joule heating effect and ampacity, which is the maximum amount of electrical current a conductor can continuously carry before sustaining deterioration given the dynamic environmental conditions. Conductor temperature is also related to another critical parameter for overhead power lines: their maximum allowable sag. These two parameters, ampacity and sag, give an idea of the importance of conductor temperature dynamic monitoring. There are several contact temperature methods on the market; however, they are expensive and challenging to implement owing to the complexity of electronic devices working in a high voltage environment related to the maintenance and life span of the instrumentation. This paper presents a novel method to estimate the temperature of overhead power lines using a non-contact infrared system. From the comparison between contact and non-contact temperature measurement methods a correction function was obtained to infer the temperature of the conductor from the infrared measurements. This option has several advantages in comparison with the current methods as it is a cheap and passive system that foregoes the need to attach electronic components to the power line, thus simplifying the maintenance and improving the safety of the operations.

The increase in energy efficiency of power systems and the development of smart grids are strongly based on new and more accurate ways of monitoring.
In overhead power line systems, the focus is on monitoring weather conditions and the main line parameters, such as the current and temperature of the conductor. Current and temperature are linked by the Joule heating effect and ampacity, which is the maximum amount of electrical current a conductor can continuously carry before sustaining deterioration given the dynamic environmental conditions. Conductor temperature is also related to another critical parameter for overhead power lines: their maximum allowable sag. These two parameters, ampacity and sag, give an idea of the importance of conductor temperature dynamic monitoring. There are several contact temperature methods on the market; however, they are expensive and challenging to implement owing to the complexity of electronic devices working in a high voltage environment related to the maintenance and life span of the instrumentation. This paper presents a novel method to estimate the temperature of overhead power lines using a non-contact infrared system.
From the comparison between contact and non-contact temperature measurement methods a correction function was obtained to infer the temperature of the conductor from the infrared measurements. This option has several advantages in comparison with the current methods as it is a cheap and passive system that foregoes the need to attach electronic components to the power line, thus simplifying the maintenance and improving the safety of the operations.

The increasing penetration of variable distributed generation causes the transmission lines to operate closer to their design thermal limits. In this context, Dynamic Thermal Rating is a very promising technique, since it permits a better exploitation of the real capability margins of the infrastructures and eliminate network congestions.
In this vein, the paper proposes a novel control strategy that allows maintaining the conductor temperature of a given line within its thermal limit through the real-time curtailment of distributed energy resources in the network. The impact of weather volatility and measurement uncertainty on the dynamic response of the controller is evaluated. A comprehensive case study, based on a real-world Italian sub-transmission system and measurement data serve to illustrate the dynamic behavior of the proposed controller.
The effect of measurement noise and delays is also discussed. Finally, the performance of the proposed control strategy is compared with a conventional robust optimal power flow approach.

The total renewable wind energy capacity of Spain currently accounts for more than 20% of the total installed energy capacity, which makes integration into the grid challenging for wind farm owners as well as Distribution System Operator (DSO). Electrical companies require new techniques to integrate renewable energies safety and with low investment costs. Dynamic line rating (DLR) is one of these techniques, and is used by DSOs to maximise the capacity of existing infrastructure.
This paper presents a successful case of DLR application by a DSO over several years to reduce the time that wind farms were out of service due to an excess of electrical energy generated. Over the period from January 2015 to September 2018, the application of the DLR technique prevented 4,100 hours of out-of-service time, increasing the energy supplied by the wind farms by 70.9 GWh and by extension saving 7,800 tons of CO2.

The dynamic management of electric power distribution lines has become a topic of great interest at present. Knowledge of the ampacity of cables is fundamental to carrying out dynamic management. In this study, the ampacity of buried cables in different soil resistivities and depths was calculated. A small-scale model was built in the laboratory to simulate the operating conditions of a buried cable. With the experimental results, a numerical model based on the finite element method was validated to evaluate the ampacities calculated by two standards. A comparison was made between the ampacities calculated from the IEC 60287-1 and UNE 211435 standards and those obtained from the simulated model. In addition, a comparison was made regarding the steady-state temperatures obtained at each calculated ampacity. The results obtained from the simulated model design show that the ampacity calculation method of the IEC 60287-1 standard where drying-out of the soil occurs is the most accurate, and has the least risk of exceeding the maximum permissible cable temperature.

The increase of global energy demand and new ways of electricity production are two of the main challenges for the power sector. The electric market has to address the addition of new and renewable sources of energy to the energy mix and to be able to integrate them into the grid, while maintaining the principles of robustness, security and reliability [1]. All of these changes point to the creation of smart grids, in which advanced generation, information and communication technologies are needed.
An accurate knowledge of the electric grid state is crucial for operating the line as efficiently as possible and one of the most important grid parameters to be measured and controlled is the temperature of the overhead conductors due to their relation with the maximum allowable sag of the line and its thermal limit (annealing).
This paper presents the results of real-time monitoring of an overhead power line using a distributed temperature sensing system (DTS) and compares these results with spot temperature measurements in order to estimate the loss of accuracy of having less thermal information. This comparison has been carried out in a 30 km long distributed temperature sensing system with fiber optic inside a LA-455 conductor and 6 weather stations placed along the line. An area of influence is defined for each weather station corresponding to the orography of the surroundings. The spot temperatures are obtained from the DTS in the nearest point from the weather stations assuming these six locations to be the ones where the spot temperature measurement equipment would be located.
The main conclusion is that, in the case of study, spot measurements are enough to obtain a good approximation of the average temperature of the line conductor.

Steady state ferroresonances in isolated neutral electrical systems result in sustained abnormal system oscillations, which can damage inductive voltage transformers (IVTs) and other system elements. During this phenomenon, the IVT becomes saturated; consequently, the dimensions of the ferromagnetic material of the IVT change owing to magnetostriction. Because of this inherently nonlinear behaviour, the natural vibration modes of the IVT are excited. The aim of this study is to take advantage of these anomalous vibration modes to reveal the occurrence of ferroresonance in IVTs. The methodology for ferroresonance detection in IVTs through vibration analysis is described and demonstrated experimentally.

Power quality events associated with the occurrence of ferroresonances in medium voltage (MV) isolated-neutral distribution power systems are well known but they still happen in nowadays grids. This work deals with the study of ferroresonance events in a distribution grid region characterised by having distributed generators and being lightly loaded. The study shows that well-known solutions, i.e. voltage transformer damping, are difficult to apply due to the legal considerations and, alternatively, the distribution system operator can take actions to minimise their effect on the distribution system. The data provided and the obtained results correspond to a three-year measurement campaign at a real MV isolated-neutral distribution power system. The measurements and analysis given allow reaching general conclusions about the distribution system operation oriented to minimise the effect of ferroresonances

Since the first wind farms began operating in the early 1980s, several important factors have changed in the overall picture of energy politics worldwide.
The total renewable wind energy capacity of Spain currently accounts for more than 20% of the total installed capacity, which makes integration into the grid challenging for wind farm owners as well as electricity transportation and distribution companies. The smart-grid concept, which focuses on realtime monitoring and dynamic rating operation of power lines, is an important component in the solution to these new challenges.
This paper explains how a more efficient operation of energy-generating activities via dynamic rating of the electric grid due to a better knowledge of the main parameters contributes to more clean, renewable energy and decreases the CO2 footprint.
The dynamic rating operation of a Spanish overhead power line is analysed, and different scenarios are studied. The dynamic rate achieved in 2015 has saved more than 1100 tonnes of CO2 and has generated over 240,000 € of extra income. This dynamic rating operation also increased the actual annual energy generated from 231.5 GW h to 834.7 GW h with only a 2% greater loss along the line due to Joule and magnetic effects.

DYNELEC es un planteamiento innovador que, mediante información climática local y de la temperatura de los conductores ent iempo real, permite operar las líneas por encima de la capacidad estática, aprovechando de esta manera las posibilidades tecnológicas para el aprovechamiento de los activos.
Este documento trata de mostrar los retos que la implantación de un proyecto de estas características contempla, en términos de monitorización y estimación de medidas, de seguridad y protección de los datos y de la información, de la incorporación de tecnologías no habituales, y de aplicabilidad estratégica para el futuro.

The European Commission has explained how heating and cooling in buildings and industry account for half of the energy consumption of the EU. Several studies explain how to achieve an energy saving at home, and the use of smart thermostats will help to reduce energy consumption while increasing the efficiency of households. In this article, a comparative evaluation was carried out between four smart thermostats that are now on the market, whose characteristics vary in terms of price, precision of measurements and set temperature, algorithms, etc. A thermal test chamber was designed and constructed from a refrigerator, a thermal blanket, a Raspberry Pi and the necessary electronic components for its control and data collection. From the tests carried out in the thermal chamber, data on the operation of the four thermostats such as the maintenance and the anticipation of the setpoint temperature, were obtained. It was necessary to run the system enough times for each thermostat to memorize the housing characteristics, such as its inertia and its thermal insulation. This would also allow for the generation of a better algorithm to regulate the temperature, which would create a lower oscillation with respect to the setpoint temperature. The learning of the thermostats was not demonstrated and for the anticipation mode it was seen that the thermostats failed to improve or learn in this aspect, as they did not improve the start-up times of the heating system, with the consequent increase in energy consumption.

Electricity generation is changing as new, renewable and smaller generation facilities are created, and classic topologies have to accommodate this distributed generation. These changes lead to the creation of smart grids in which advanced generation, information and communication technologies are needed.
Information metering is important, and one of the most important grid parameters to be measured and controlled is the temperature of overhead conductors due to their relation to the maximum allowable sag of the line.
The temperature and current of an overhead conductor and the weather conditions surrounding the cable are measured every 8 min for more than a year. With these data, the accuracies of the different algorithms presented in the standards (CIGRE TB601 and IEEE 738) are studied by implementing them in MATLAB®.
The use of precise measurements of solar radiation and low wind speeds with ultrasonic anemometers, improves the accuracy of the estimated temperature compared with the real measured conductor temperature. Additionally, using dynamic algorithms instead of assuming a steady state analysis increases the accuracy. However, an equilibrium between the accuracy and mathematical complexity should be obtained depending on the specific needs.

Together with the impurities, the thermal fluxes are one of the major sources of uncertainty during the realization of the International Temperature Scale of 1990 (ITS-90) defining fixed points. The use of computational fluid dynamics (CFD) is a valuable tool to develop models that describe the time evolution of the phase transformation (essentially the evolution of the solid–liquid interface) as a function of given theoretical assumptions and given parameters (furnace thermal gradients, freezing initiation, ambient temperature and insulation). The models can be validated by observing the impact of the selected parameters on the observed corresponding melting curves and used to achieve a full understanding of these thermal effects and their impact on uncertainty. This paper proposes an ITS-90 metallic fixed points CFD model together with some results about the influence of the furnace thermal gradients and the freezing initiation techniques.

This paper presents the steady and dynamic thermal balances of an overhead power line proposed by CIGRE (Technical Brochure 601, 2014) and IEEE (Std.738, 2012) standards. The estimated temperatures calculated by the standards are compared with the averaged conductor temperature obtained every 8 min during a year. The conductor is a LA 280 Hawk type, used in a 132-kV overhead line. The steady and dynamic state comparison shows that the number of cases with deviations to conductor temperatures higher than 5ºC decreases from around 20% to 15% when the dynamic analysis is used. As some of the most critical variables are magnitude and direction of the wind speed, ambient temperature and solar radiation, their influence on the conductor temperature is studied. Both standards give similar results with slight differences due to the different way to calculate the solar radiation and convection. Considering the wind, both standards provide better results for the estimated conductor temperature as the wind speed increases and the angle with the line is closer to 90º. In addition, if the theoretical radiation is replaced by that measured with the pyranometer, the number of samples with deviations higher than 5ºC is reduced from around 15% to 5%.

The transformers lifespan depends importantly on its refrigeration. Mineral oils perform this work in the majority of the power transformers. However, this type of coolant has two main drawbacks: low biodegradability and low ignition point. Several alternative liquids are being developed in order to overcome these drawbacks. This paper compares their thermal-fluid behavior with a mineral oil by means of several parameters, such as temperature, flow rate, fluids velocity, convective heat transfer coefficient (h) and the cooling criterion (P). These are calculated using the numerical results of the simulation of a 3D-model of a Low Voltage Winding that belongs to a power transformer with ONAN cooling. The software COMSOL Multiphysics has allowed the simulation of the geometry using a physical model in which buoyancies and viscous forces are the only considered establishing the natural convection. As a result of the comparison, it is clear that the mineral oil is the best coolant liquid. Among the alternative liquids, silicone oil would be the second best coolant fluid, followed by the synthetic and natural esters, respectively. On the other hand, it seems to be clear that the 3D simulations can be used to compare properly the cooling capacities of the liquids.

The paper discusses the effect of two-front melting on the liquidus temperature of the eutectic Pt–C and the eutectic temperature of the system in its pure state. This influence factor has not been considered thus far in the uncertainty budget associated with the assignment of thermodynamic temperatures to the eutectics Co–C (1597.15 K), Pt–C (2011.05 K), and Re–C (2747.35 K), selected in the European Metrology Research Programme project Implementing the New Kelvin. For Pt–C, simulation of the effect of two-front melting on the melting process has been done before in a 1D analytical model, and this formed the starting point to the present study. In this study the melting process is analyzed by means of a 2D axisymmetrical finite-volume model. In the model, freezing and melting are considered for an impure ingot and for a pure ingot. As to the impure ingot, the impurity concentrations are the concentrations met in current practice of the realization of the high-temperature reference fixed point, but formulated in terms of an effective concentration and associated effective distribution coefficient k<1k<1 , related to a Scheil fit to the melting curve at given melting conditions as measured for the eutectic Pt–C. Heat injection rates for melting varied from 15 000 Wm^(−2) down to 3000 Wm^(−2). In any case for the impure system, two melting fronts are showing up. For the pure system, only one melting front is generated, traveling from the outside of the ingot toward its inside.

This study forms part of the European Metrology Research Programme project implementing the New Kelvin to assign thermodynamic temperatures to a selected set of high-temperature fixed points (HTFPs), Cu, Co–C, Pt–C, and Re–C. A realistic thermal model of these HTFPs, developed in finite volume software ANSYS FLUENT, was constructed to quantify the uncertainty associated with the temperature drop across the back wall of the cell. In addition, the widely applied software package, STEEP3 was used to investigate the influence of cell emissivity. The temperature drop, ΔTΔT , relates to the temperature difference due to the net loss of heat from the aperture of the cavity between the back wall of the cavity, viewed by the thermometer, defining the radiance temperature, and the solid–liquid interface of the alloy, defining the transition temperature of the HTFP. The actual value of ΔTΔT can be used either as a correction (with associated uncertainty) to thermodynamic temperature evaluations of HTFPs, or as an uncertainty contribution to the overall estimated uncertainty. In addition, the effect of a range of furnace temperature profiles on the temperature drop was calculated and found to be negligible for Cu, Co–C, and Pt–C and small only for Re–C. The effective isothermal emissivity (εeff)(εeff) is calculated over the wavelength range from 450 nm to 850 nm for different assumed values of surface emissivity. Even when furnace temperature profiles are taken into account, the estimated emissivities change only slightly from the effective isothermal emissivity of the bare cell. These emissivity calculations are used to estimate the uncertainty in the temperature assignment due to the uncertainty in the emissivity of the blackbody.

This paper presents a comparative study of the electricity consumption (EC) in an urban low-voltage substation before and during the economic crisis (2008–2013). This low-voltage substation supplies electric power to near 400 users. The EC was measured for an 11-year period (2002–2012) with a sampling time of 1 minute. The study described in the paper consists of detecting the changes produced in the load curves of this substation along the time due to changes in the behaviour of consumers. The EC was compared using representative curves per time period (precrisis and crisis). These representative curves were obtained after a computational process, which was based on a search for days with similar curves to the curve of a determined (base) date. This similitude was assessed by the proximity on the calendar, day of the week, daylight time, and outdoor temperature. The last selection parameter was the error between the nearest neighbour curves and the base date curve. The obtained representative curves were linearized to determine changes in their structure (maximum and minimum consumption values, duration of the daily time slot, etc.). The results primarily indicate an increase in the EC in the night slot during the summer months in the crisis period.

When characterizing high-temperature fixed points, the fraction of the melting time of the regular part of the plateau with respect to the total melting time, is critical. Maximizing the melting duration minimizes the uncertainty associated with the determination of the fixed-point temperature. One factor that affects this quality is the effect of the thermal bridging between the external and internal surfaces of the ingot enclosed by the cell. This paper presents the results of simulations for the eutectic Pt-C, investigating the effects of different ingot shapes on the duration of the melt plateau. It was found that the formation of a thermal bridge from the rear of the blackbody cavity toward the outer surface of the ingot was critical and that its formation could be delayed or suppressed through a proper choice of the ingot shape. The shapes considered included, firstly, the shape of the rear of the cavity, in contact with the ingot, either cone-shaped or dome-shaped, and secondly, the inside rear surface of the cell, in contact with the ingot, being a cone, a convex dome, or flat. The presence of impurities in the alloy was taken into consideration, and its influence in the evolution of the liquid–solid interface compared with that for the pure alloy. The effect of changing the thermal isolation of the cell, at its front side, was also considered. A dome-shaped surface for the rear of the cavity was found to be more favorable for the development of a regular melting front, in conjunction with the segregation of impurities during melting. At the rear of the cell, a flat surface ensures the back wall is the last to experience thermal bridging, resulting in more extended melting plateaus.

This paper reports thermal modelling that aims to establish if the measurement method – either by a radiation thermometer or by a thermocouple – significantly influences the measured temperature of the high temperature fixed points Co-C, Pd-C and Ru-C. It is clear that both measurement techniques have specific physical characteristics which may affect the temperature measured during the melting plateau. With the radiation thermometer, the radiation heat transfer is directly influenced by the environment because the back-wall is effectively viewing the cold outside environment. In the case of a thermocouple direct viewing of the outside world is blocked so radiation transport is significantly reduced; however, in the case of the thermocouple there is a different component of heat transfer, namely conduction from the thermowell walls in contact with the thermocouple along the thermocouple stem itself.

We explore the evolution of the Spanish power system vulnerability over the next two decades and its dependency on fossil fuel prices and CO2 allowances costs. Also, the influence of different generation technologies (clean coal, nuclear and solar technologies) on this vulnerability has been considered. The diversity of primary energy resources has been evaluated to carry out the above analysis by means of two indexes: the Shannon index (H) and an adapted biodiversity index (Δ). These indexes have been applied to the power results of the period 2013–2032 that are obtained from a stochastic linear model of the Spanish generating system. As a main conclusion, the vulnerability calculated with Δ is bigger than that deduced from H and showing a negative trend throughout the period. In order to reverse this tendency, the future Spanish generating system should be composed of all the available technologies, considering all the primary energy resources.

The increasing use of small wind energy has made it necessary to develop new methods to improve the efficiency of this technology. This improvement is best achieved considering the interaction between the various components, such as the wind rotors, the electrical generators, the rectifiers and the inverters, as opposed to studying the individual components in isolation. This paper describes a methodology to increase the efficiency of Small Wind Turbines (SWTs) equipped with a Permanent Magnet Synchronous Machine (PMSM). To achieve this objective, capacitor banks will be connected between the PMSM and the rectifier. This methodology is motivated by two clear aims. The first one is to operate the SWT with its maximum power coefficient Cp. The second one is to select the most suitable capacitor bank for each wind speed to optimise the energy supplied to the grid. The methodology will be tested on a commercial 3.5 kW SWT, and the results will be studied to determine its feasibility.

The implementation of batch processing has increased due to its intrinsic flexibility and adaptability. These are essential characteristics when it comes to producing high-value added materials such as agrochemicals, pharmaceuticals, specialty chemicals…the demand for which has grown in recent decades.

Although industrial processes are highly diverse, a common feature to all is that they utilize fossil fuels as the energy source. The reliance on fossil fuels as a primary source of energy generates a negative impact on the environment. The implantation of renewable energies and efficient usage of energy has thus become crucial. Improving energy use could be achieved through advancements in plant machinery and the use of methodologies such as ‘process integration’.

Process integration can be described as system oriented methods that could be used during the design and retrofit of industrial processes in order to obtain an optimal utilization of resources. The methods have traditionally focused on an efficient energy use, although recently process integration techniques cover other areas such as efficient use of raw materials, emission reduction and process operations. Energy integration tries to reach the optimization of heat, power, fuel and utilities.
The consideration of energy integration complicates the process design and the generation of batch process design alternatives, so what is now required is the proposal and development of different approaches and methods oriented towards recovering energy in this kind of industrial process. Improving energy end-use efficiency will make it possible to reduce dependence on energy imports and bring about innovation and competitiveness.

The aim of this work is report the main contributions that have been carried out in order to attain energy integration in batch processes, as well as different examples of applications that have shown the possibilities offered by the developed tools.

This paper takes us a step forward with respect to previous definitions for the measurement of electric power quantities under non-sinusoidal conditions.A new decomposition of voltage, current and power is presented in order to determine the extent to which the distribution company and the electrical energy consumer are each responsible for the harmonic distortion measured at the point of common coupling, PCC.This gives us three different quantities: fundamental frequency, frequencies associated with the distribution system distortion and frequencies associated with consumer distortion. These magnitudes can also be measured in relation to power factor compensation and harmonic elimination problems in power distribution systems.In addition to this, the power factors resulting from the new decomposition are also analyzed and the decomposition algorithm implemented on a measurement platform based on a digital signal processor, DSP.Finally, the general structure of the system, focusing on both hardware and software, is also discussed.

The utilization of LED technology in lighting applications has been increasing during the last several years. Parameters like efficiency, reliability, chromatic response and cost are important to consider this technology as a competitive one. LED technology involves power converters so overall Power Quality performance has to be analyzed in terms of emission and susceptibility. This paper reviews the Power Quality behavior of some commercial grade LED lamps and establishes a comparison with the long established incandescent lamp.

This article is the result of an analysis into the behavior of several forest species that could be used as energy crops in Cantabria. The species studied belong to several botanical genera. The study was conducted in several stages: firstly, the species was introduced to explore growth data and discard those species of slower growth. Once the genus maximising the biomass production was determined, several species of it were studied from the energy perspective. This combination of both allows the energy density for each species to be obtained, therefore making it possible to determine how big a cultivation area is required for a specific thermal power plant. Thus, for a power plant of 10 MWe, between 15,451 and 24,578 ha of Eucalyptus would be necessary, depending on the species chosen, at an approximate age of 4 years.

The eutectics Co–C, Pt–C, and Re–C, with phase transition temperatures of 1597 K, 2011 K, and 2747 K, respectively, are presently investigated for their suitability to serve as reference points for dissemination of T (and T90) within the context of the “Mise en pratique of the definition of the Kelvin” (MeP-K) at high temperature. Temperatures are to be measured by means of radiation thermometry of cavity radiators embedded in the associated eutectic. This paper deals with the determination of the cavity spectral effective emissivities, which are influenced by the reflective properties of the graphite constituting the cavity on the one hand, and by the temperature distribution within the cavity and over the radiation-shield structure in front of the cavity, on the other. We have begun a comprehensive effort to determine the cavity effective spectral emissivities at 405 nm and 650 nm. The overall program involves diverse measurements on representative graphite samples, furnace-temperature profile measurements, calculations of temperature distributions, and, finally, based upon this information, calculation of effective emissivity dependencies for cavity radiators. Here we report the current status of the study, including cavity temperature distributions and Monte Carlo modeling results, associated with appropriate steps of the envisaged overall project. For the time being, the modeling assumes current estimates of the graphite emissivity and the bi-directional reflectance distribution function (BRDF), which will be updated as experimental data become available.

This article shows that lamp aging has a significant correlation with flicker generation. In this research work, a test system and a methodology able to measure optical fluctuation produced by different types of lamps and ballast are presented. This experimental platform provides a correlation between voltage flicker levels and optical flicker perception. This platform can be considered as a first step in the definition of new lamp models. The limits of the severity of flicker caused by voltage fluctuations are defined in Europe by the standard CENELEC EN 50160.

The evolution of the vulnerability of the Spanish power generation system with respect to the primary energy resources hasbeen assessed by three new indexes developed from biodiversity analysis. The first of these indexes measures, in percentage, the uniformity of the primary energy resources in the system. The second one quantifies the diversity by means of the equivalent number of primary energy resources that are present in similar proportions in the system. The third one allows the calculation of the diversity reduction in the system with the non-evenness of these primary energy resources. They have been applied to the energy results of a stochastic linear model, developed with
the software GAMS, in order to demonstrate their usefulness. In this model several generation technologies have been considered (nuclear, clean coal technologies, etc), and also several scenarios
of fossil fuel costs. The number of primary energy resources that have to be used depends on the degree of uniformity of the system and on their influence on diversity. In the Spanish case, if nuclear generation is not considered as an energy source, the diversity of the system will diminish significantly in the future, making the system more vulnerable.

High-temperature fixed points (HTFPs) based on eutectic and peritectic reactions of metals and carbon are likely to become, in the near term, reference standards at high temperatures. Typically for radiation thermometry applications, these HTFPs are generally formed of a graphite crucible, with a reentrant well, an included 120° cone, and a nominal aperture of 3 mm. It is important to quantify the temperature drop at the back wall of the cavity, and to understand the influence of the crucible configuration and furnace conditions on this drop. In order to study these influences, three different situations have been modeled by means of the finite volume method for numerical analysis. The first investigates the influence of the furnace temperature profile on the temperature drop by simulating four different furnace conditions. The other two study variations in the crucible configuration, namely, the thickness of the graphite back wall and the length of the blackbody tube.

En el mundo existe un número importante de factorías de fundición que, por su proceso productivo, son grandes consumidoras de energía. Las factorías trabajan con diversos tipos de hornos como son los de gas, de inducción eléctrica, y de cubilote. El estudio de este artículo se centra en los de cubilote y más concretamente en aquellos que tienen una producción de colada continua. Los gases que estas instalaciones emiten al exterior tienen un gran contenido energético, ya que se encuentran a alta temperatura y por lo tanto son susceptibles de aprovechar energéticamente. Actualmente las instalaciones suelen tener un aprovechamiento energético para el calentamiento del aire soplado a la combustión. Pero incluso después de este aprovechamiento térmico los gases de escape se pueden expulsar a temperaturas superiores a 600ºC y por lo tanto aún son susceptibles de aprovechar energéticamente. La recuperación de calor de estos gases se puede destinar a producir electricidad, siendo ésta una alternativa que conduce a: incrementar la eficiencia del proceso, disminuir las emisiones de contaminantes gaseosos (la generación eléctrica no emite nada que no se emitiera anteriormente), y reducir los costes de operación de la planta.
En este trabajo se han analizado dos alternativas de aprovechamiento energético del calor residual de estos gases mediante cogeneración. La primera consiste el empleo de módulos prefabricados, y la segunda en una instalación clásica de cogeneración con caldera de recuperación y turbina de vapor. Para cada alternativa se han realizado dos análisis: uno económico (considerando inversión, ingresos por electricidad y los costes de operación) y otro técnico (considerando la viabilidad técnica de su instalación, presentando ventajas y desventajas de cada una de las alternativas). Esto nos ha permitido establecer una serie de conclusiones generales que se aportan al final del artículo.

This paper presents the influence of a nuclear generation option on CO2 emissions and on the cost of the Spanish long-term generation system by means of the development of a stochastic linear model, based on the software GAMS, where multiple aspects have been contemplated: the uncertainty regards fossil fuel and CO2 emission allowance prices by analysing different scenarios, the stability and supply security of the system by considering different restrictions, the maximum grade of penetration of the different technologies by means of commissioning plans, etc. Only two of the conclusions drawn are focused on here. First, it is possible to get a clean system without nuclear power generation but the cost would be higher than in the case where the existing nuclear power plants continue to operate. Second, the development of clean coal technologies could be affected negatively by the development of nuclear generation.

This paper investigates, through thermal modeling the effect on the radiance temperature of imperfectly filled thermometric fixed points. A two dimensional axisymmetric thermal model was established and the effect on the radiance temperature of various ingot imperfections such as voids and cracks in different places and of different dimensions in the ingot structure was calculated. It was found that the radiance temperature of the fixed point is quite tolerant to even relatively large flaws in the ingot structure. Only when flaws of significant dimensions near the radiating back wall were introduced was the overall radiance temperature significantly affected.

Quality assessment during DC motor manufacturing should involve quality controls designed to detect various fault conditions associated with the components included in the machine.

Some defects, however, can be produced by the automatic manufacturing process during the assembly of the individual components. Inter-turn short-circuits, turn to earth short-circuits and open winding, among other fault conditions, can result from the field poles manufacturing and insertion inside the stator. The main problem with these kinds of faults is that though the motor is likely to be operational, there is a high probability of motor breakdown in the near future.

In this paper, the above fault conditions are analyzed and a thermal model and an infrared monitoring test method for manufacturing quality control is proposed.

En los últimos años, el diseño de máquinas eléctricas se ha ido apoyando, cada vez más, en herramientas informáticas de pre-dimensionamiento, diseño y simulación, en los ámbitos eléctrico, magnético y térmico.