Dielectric properties enhancement of vegetal transformer oil with TiO2,CuO and ZnO nanoparticles

Nanofluids based on vegetal oils remain almost unexplored, especially when prepared with non-ferric oxide nanoparticles. This work has analysed the effect of three different nanoparticles on properties of a commercial vegetal oil. The first aim was to evaluate if there is an optimal concentration for dielectric improvement, and if the effect of different nanoparticles is similar. Secondly, other key properties were considered. The evaluated dielectric properties have been AC breakdown voltage, relative permittivity, volumetric resistivity and dissipation factor. The results are quite promising because dielectric properties have shown a considerable improvement. On the other hand, thermal conductivity or acidity test results, although adverse, were not definitive to refuse to continue this research.The authors of this research wish to thank the Ministry of Economy for financial support to the National Research Project: Improvement of Insulation Systems of Transformers through Dielectric Nanofluids (DPI2015-71219-C2 1-R). Also Mr. Olmo would like to acknowledge to the University of Cantabria and the Government of Cantabria for the financial support for the Ph. D. scholarship (CVE-2016-6626)

Potential production of electrical energy from forest biomass in the north of Spain: Cantabria

In this work, the authors analyze productive, power, environmental and economic aspects of the forest biomass in the north of Spain. All these points will determine the future development of this power resource, making special reference to the case of the province of Cantabria

Advances in phase change materials for thermal solar power plants quality

Thermal solar energy offers a huge opportunity to reduce fuel dependency and environmental impact created by fossil fuel consumption. One of the main disadvantages of this renewable energy is its intermittence which decreases thermal solar power plants performance. In order to reduce cost electricity is necessary to create thermal solar plants which include thermal storage. There are different options of thermal storage: sensible, latent and chemical heat. It has been demonstrated that latent heat could store large amount of energy per unit mass. Moreover, latent heat storage could store fusion heat at a constant temperature which is the phase transition temperature of the phase change materials (PCM). However, these materials have a critical limitation that needs to be resolved in order to reduce operation cost of solar plants. This limitation is their low heat conductivity. This paper gathers the main solutions that are being analyzed in order to increase the possibilities to use PCMs in a high temperature thermal storage that is essential to develop optimum thermal solar power plants

Three-phase frequency measurement under non-sinusoidal conditions using the static reference frame

The utilization of Clark's transformation in the estimation of the power system frequency provides more robustness to the classical single-phase methods. One of the advantages of this technique is that extract the frequency information contained in the three-phase system. This is particularly important when asymmetric sag generates a zero voltage in one of the three phases.The authors would like to thank the support of the Spanish Government under the CICYT research project DPI2002-04416-C04-01

Supply security and the reliability of the spanish generator system in the next two decades based on the costs of fossil fuels and nuclear option

The supply security of the primary energy sources (coal, natural gas, enriched uranium...) and the reliability of the system in terms of the oscillations of the frequency and voltage are two aspects to assess in the Generation Expansion Planning. In this article, for the first criterion, the evolution of vulnerability and degree of independence of the generator system with respect to primary energy sources has been assessed by the indexes of Shannon-Weiner and energy independence, respectively. For the second approach, the evolution of the reserve margin by means the coverage index and the progression of the inertia and regulation capacity by means of its percentage regarding the total installed capacity. These four indexes have been applied on the obtained results of a stochastic lineal model developed with the software GAMS. In this model the nuclear technology has been considered as generation option in several scenarios of costs of the fossil fuels, coal and natural gas. Also, two of clean coal technologies with greater possibility of putting into service have been taken into account. The final conclusion would be that each technology carries out several functions in the generator system but not all them. That is, a generator system should have the greatest possible number of types of generation to be reliable and have supply security

Eucalyptus globulus and the eucalyptus nitens as energy crops

The objective of this work has been to evaluate the power potential of fast growth forest species, which could be operated in Cantabria (North Coast of Spain). This region has a forest surface of 145,000 hectares with no plantation. The use of forest species as energy crops implies high density of plantation, and very short rotations (2-3 years). Therefore, it is the tree youthful stage the one that will be the focus of attention on this work. The Eucalyptus is the fast growth species that has demonstrated the greatest biomass production, by hectare, in the region. Two varieties of Eucalyptus have been planted for years in our region in order to supply the paper industry. These species are Eucalyptus Globulus and Eucalyptus Nitens. The great experience accumulated in the use of these forest species and their great productivity, make of them good candidates to join the set of suitable trees for being used as energy crops. In this work a power characterization of the young stages of the species Eucalyptus Globulus and Eucalyptus Nitens has been carried out. The power characterization has been carried out in an adiabatic high accuracy calorimeter, IKA C 5000. The work was made in the four seasons of the year, which has allowed studying the influence of the seasonality in the calorific power of the species. In addition, the influence that the implantation of these species would have on the CO2 emissions and in the greenhouse effect has been evaluated.The authors want to thank to the Council on Research and Technological Development of the University of Cantabria by their financial support; to the company Bosques 2000 S.L. for his great help by its support in the collection of samples and data

Comparative study of two cogeneration systems based on energy recovery of fumes from a casting process

This paper develops the comparison of two cogeneration systems that are suitable to perform heat energy recovery of the smoke produced by a casting process.The authors would like to thank the financial support of Government of Cantabria and NISSAN under the INVESNOVA research project and to the Council on Research and Technological Development of the University of Cantabria by their administrative assistance

Comparison of energy potential of the eucalyptus globulus and the eucalyptus nitens

In this work a power characterization of adult stages of the species Eucalyptus globulus and Eucalyptus nitens has been made. The study has been made in six different plantations in Cantabria (North coast of Spain), located at a latitude 43º28'N, and a longitude 3º48'W. The region has approximately 30,000 Ha dedicated to the growth of Eucalyptus. After the collection of samples they were weighed, analyzed and burned, resulting a mean net calorific value of 17,384 kJ/kg and 17,927 kJ/kg for the E. globulus and E. nitens, respectively. Finally, the economic and environmental consequences that the crop of these species would suppose for the region of Cantabria were analyzed.The authors want to thank to the Council on Research and Technological Development of the University of Cantabria by their financial support, to the company Bosques 2000 S.L. for his great help and to the Forest Department of the Government of Cantabria by its support in the collection of samples and data

Energy implications of the mycosphaerella sp. in eucalyptus globulus stands

In the last decade, the emergence of leaf disease caused by the fungus Mycosphaerella sp. is jeopardizing the development of some species of the genus Eucalyptus at its juvenile life stage. The development of forest species for energy purposes, namely to generate biomass in shorter periods, must take into account this circumstance at the time of measuring the energy density generated by these species. This paper defines a method which relates the measure of the severity of the disease with the energy lost per Ha. First, it has been characterized from the energy point of view, thus, it has quantified the calorific value of the biomass of Eucalyptus globulus decomposing it in their respective fractions at certain moisture. Then, depending on the degree of severity of the disease, it has been estimated the amount of dry biomass per tree at the age of 27 months and crossing it with the calorific values it has been determined the energy loss per unit of area according to the overall damage index. Finally, a brief economic analysis considering the consequences of this disease in a stand of Eucalyptus globulus for energy production, has been performed

Cogeneration in a hospital: a case study

In this paper the authors analyze different alternatives to provide energy utilities to a hospital center with cogeneration systems with diesel engines and gas turbines. The study considers several power sizes and control strategies, so it shows the influence of these parameters, showing that in this case the options with diesel engines are more efficient than the equivalent ones with gas turbines