In this paper we evaluate ΔT, the temperature drop across the cavity’s backwall, and its standard uncertainty u(ΔT) for the high-temperature eutectic fixed points Co-C, Pt-C and Re-C with eutectic temperatures TE of 1597 K, 2011 K and 2747 K, respectively; the evaluation involves a variety of cavity-furnace geometries. For the derivation of u(ΔT) the partial uncertainties in ΔT associated with the uncertainties in the thermal conductivity Kg of graphite, in the cavity-wall emissivity Eg and in the furnace-temperature profile ahead of the cavity are evaluated and quantified. ΔT is shown to vary with TE4 for a given cell-furnace configuration, with typical values of 12 mK, 25 mK and 92 mK at the Co-C, Pt-C and Re-C fixed-point temperatures, respectively. For the uncertainty in the temperature drop we find globally u(ΔT) ≈ 0.1·ΔT.

This paper presents a step forward respect to the 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 responsibility of the distribution company and the electrical energy consumer for the harmonic distortion measured at the point of common coupling, PCC. This way, three types of variables should be managed, namely fundamental frequency, frequencies associated with the distribution system distortion and frequencies associated with the consumer distortion. These magnitudes can be also measured in relation to power factor compensation and harmonic elimination problems in power distribution systems. Moreover, the power factors resulting from the new decomposition are also analyzed. The algorithm of the decomposition will be implemented on a measurement platform based on a digital signal processor, DSP. The general structure of the system, hardware and software, are also discussed.

Quality assessment during dc motor manufacturing should be accomplished by quality controls in order to detect the different fault conditions associated to the components included in the machine. However, some defects can be produced by the automatic manufacturing process during the assembly of the individual components. Among others, inter-turns short-circuit, turn to earth short-circuit and open-winding can result from the rotor insertion inside the stator. The main problem with these kind of faults is that the motor can operate but there is a high probability of motor breakdown in the near future.

Energy recovery in the industry is one of the most important parameters with which the companies have to play to be competitive and respectful with the environment, because it helps to improve the energy efficiency. In that way, the use of energy recovery systems plays an important role. This gets a special relevance in batch Processes, where the needs of heating and cooling are not produced at the same time. Therefore, the study and optimization of heat recovery systems with thermal storages can play an essential part.
In this paper, it is analyzed the heat recovery system made by a heat exchange network and thermal storages which will optimize the heat recovery in batch industrial processes.

In this work, the waste from 10 forest species of Cantabria have been characterized from the point of view of energy. The studied species were the waste of: Eucalyptus globulus, Eucalyptus nitens, the hybrid E. globulus × E. nitens, Eucalyptus viminalis, Eucalyptus smithii, Eucalyptus regnans, Eucalyptus gunni, Fagus sylvatica, Quercus robur and Pinus radiata. The leaves were the tree part with the greatest NCV (net calorific value) in all the species. The best results were obtained for the leaves of E. smithii (24.5 MJ/kg), F. sylvatica (22.8 MJ/kg) and E. nitens (22.5 MJ/kg), at minimum moisture. Values around 65,000 MJ per hectare and year were obtained for the Eucalyptus spp., and 47,000 MJ per hectare and year for the P. radiata. The economic-environmental analysis revealed that the use of the forest waste for energy production would mean an approximate annual income of 8 M€ and would fix the annual CO2 emitted by the Cantabrian industries at 78%.

In this article, a new design for reversible air–air heat pumps is proposed. This design is not based on the refrigerant changeover, as is proposed by ASHRAE, but rather is based on the inversion of the air flow on the ducts. Thanks to this modification it is possible to use any air–air refrigeration machine for air conditioning as a reversible heat pump.

The new design is more efficient, especially when the building requires greater air quality and therefore a larger amount of outdoor air. It also increases its efficiency as the outdoor temperatures become more extreme.

This improvement will make it possible to use heat pumps, with acceptable performances, in more rigorous climates than those in which they are used today.

Is it advisable to replace ferraris based meters with electronic meters? The permanence of the electromechanical meters currently in use is often justified on the grounds of their long working life and low price. However, it is well known that they are highly sensitive to external conditions and that many factors can lead to miscalibration. This work attempts to clarify some key points in order to answer the previous question. It reviews the operating principles of energy meters. The behavior of watt-hour meters under nonsinusoidal conditions is also studied. The disturbances considered were harmonics, unbalance and main frequency variations.

This work studied the potential use of the waste from Eucalyptus globulus and Eucalyptus nitens as energy crops, evaluating young and adult stages of both in all four seasons of the year with different moisture contents. The study was carried out made in Cantabria (North coast of Spain), located at latitude 43°28′N, and longitude 3°48′W. In this region, 29,513 ha are dedicated to the growth of Eucalyptus, with about 80% E. globulus, and 20% E. nitens. Six different plantations have been analyzed and their bioclimatic diagrams determined. After the collection of samples the potential energy of every sample was obtained, they were weighed, analyzed and burned, giving a mean net calorific value of 17,384 and 17,927 kJ/kg in the adult stage of E. globulus and E. nitens, respectively. The results for the young stage of both species were 17,708 and 18,670 kJ/kg. Moisture content in the samples has a great influence on power production. Finally, the economic and environmental consequences of these crop species for the region of Cantabria were analyzed.

The optimum energy consumption in an air conditioning system depends on many factors. Some of these are the following: the use of high performance devices, the utilization of these in the optimum efficiency range, a correct control strategy, a proper maintenance, etc.

In air conditioning facilities most of the energy consumption corresponds to the thermal production, this being heat and cold. This thermal supply is commonly accomplished with boilers, chillers and heat pumps.

In this article the efficiency of the reversible water–water heat pumps is analyzed, proposing a design that optimizes these elements. This improvement hardly requires modifications at manufacturing and operation levels, and it also contributes towards optimizing the energy consumption of these machines.

The utilization of Clarke’s transformation in the estimation of power system frequency provides the classical singlephase methods with more robustness because the estimated frequency is computed using the information provided by the threephase voltage. This approach is particularly important when asymmetric sags generate zero voltage in one of the three phases. In addition, the proposed algorithm exhibits good behavior during dynamic conditions. The Clarke components of the voltage signals are then used to compute the frequency of the system following an iterative approach based on a proportional–integral–derivative controller. The inverse component of the voltage is also used in order to detect unbalanced conditions. The proposed algorithm has been put to the test with distorted three-phase voltage supplied by an arbitrary waveform programmable power supply and with different signals generated with an Alternative Transients Program-Electromagnetic Transients Program model.

In the present article, the authors analyze different possibilities for providing heating, air conditioning and hot tap water to a hospital center. For this, several cogeneration systems with diesel engines and gas turbines were considered. From the study of the results, it is observed that the size of the facility and the control strategy have a strong influence on the system economy, showing that the most important parameter is the electricity produced. So, the solutions with diesel engines are more efficient than the equivalent ones with gas turbines, since they have a higher electrical performance.

The total harmonic distortion (THD) ratio is a wellknown parameter that characterizes the distortion degree at a specific point of the grid. In this paper, a decomposition of the THD will be presented in order to determine the responsibility of the distribution company and the electrical energy consumer for the harmonic distortion measured at the point of common coupling (PCC). For this study, the power quantities proposed in the new Standard IEEE 1459–2000 and developed by L. Czarnecki were considered. The algorithm of the decomposition will be implemented on a measurement platform based on a digital signal processor (DSP). The general structure of the system—hardware and software—are also discussed. Finally, the apparent powers, defined by both L. Czarnecki and the IEEE Standard, are also compared for single-phase and threephase systems.