Efficient Energy Source Research Articles

Chicken feather fiber-based bio-piezoelectric energy harvester: an efficient green energy source for flexible electronics

We report the prototype fabrication of a flexible, biocompatible bio-piezoelectric energy harvester using keratin-enriched chicken feathers.

China’s Natural Gas Price Reform and Its Impact Analysis

With the further development of new types of industrialization and urbanization in China, the environmental deterioration and energy safety problems have been increasingly prominent. As a clean, efficient and high-quality energy source, natural gas has ushered in unprecedented development opportunities. In recent decades, the natural gas consumption has kept high-speed growth in China, but its proportion in the energy consumption structure still has a long way to go to reach the international average level, which is mainly ascribed to the not perfect enough market-oriented reform of natural gas price. Natural gas price reform is not a simple project, but instead, it is complicated as it needs to integrate the reform in the natural gas industry chain, management system reform and market supervision of natural price in different phases. Therefore, promoting the natural gas price reform and establishing a perfect supervision system is the only way to ensure China’s energy safety and realize the transformation and development of low-carbon economy. In this research, the current situation and problems existing in the natural gas price reform in China were analyzed, and the concrete solutions specific to the natural gas industry chain, pricing and market supervision.

Benchmarking of efficiency of accumulation and storage of hydrogen as a motor fuel

The development of hydrogen energy and the need to find new efficient energy sources and develop on their basis environmentally friendly alternative fuels due to two main factors: the rapid depletion of oil reserves on Earth; deteriorating environmental situation in many countries, ahead in development. Today, the attractiveness of hydrogen as a universal energy source is determined by environmental friendliness, flexibility and efficient energy conversion processes for its participation. General work support is a comprehensive situational analysis (SNW-analysis, benchmarking) of the world experience of using hydrogen as a motor fuel, which includes identification of the best technologies, trends, features of use, research of advantages and disadvantages of technological accumulation and storage of hydrogen, and ways to achieve strategic goals for hydrogen technologies in the future. It is known that hydrogen as an environmentally friendly motor fuel is provided with high-tech methods of accumulation and storage, increases the minimization of emissions of harmful substances and can significantly improve the state of the technosphere. From these data, we concluded that the best technology for storing hydrogen as a motor fuel is compressed hydrogen gas. Because the existing models of tanks made of carbon fiber are light and reliable, as well as the hydrogen supply stored in them for 400-500 km of the car. The new materials section allows you to store hydrogen for a higher pressure. The best technology for the accumulation of hydrogen as a motor fuel is - fuel cells. A significant advantage of fuel cells is the quiet operation and the absence of harmful emissions during operation. The most effective is the use of fuel cells in cars. The best feature is that the use of fuel cells involves the use of chemical energy of the fuel converted into electricity that bypassing to the combustion processes.

Аналіз застосування біотехнологій щодо одержання високоякісного садивного матеріалу рослин родини Salicaceae Mirb. in vitro для створення біоенергетичних плантацій

In conditions of a sharp reduction in the stocks of traditional fuels, it is important to find new efficient and renewable carbon-neutral energy sources. One of the most promising sources of renewable energy is the biomass of woody plants, in particular the family Willow (Salicaceae Mirb.). Traditionally, Salicaceae plants are propagated by generative and vegetative methods. Microclonal propagation, in contrast to traditional methods of reproduction, allows to obtain genetically homogeneous healthy planting material throughout the year. A significant number of biotechnological publications focus on the development of the optimal protocol for the reproduction of plants of the family Salicaceae, the study of the morphogenetic potential of tissues and optimizing their growth. However, the authors note the individually determined regenerative ability of plant material in vitro, which depends on a number of factors. The purpose of the study is to analyze the results of biotechnological research on the effectiveness (possibility) of obtaining high-quality planting material of plants of the family Salicaceae by tissue in vitro. For this purpose, we used the results of biotechnological studies of plant tissues of the family Salicaceae in vitro by foreign and domestic authors published in professional journals during 2010−2020. Research methods − analysis, comparison, synthesis, generalization. The analysis revealed that the sterilization regime of Salicaceae plant material depends on the type of explant, phenological phase and age of the donor plant. Step-by-step sterilization using mercury chloride, sodium hypochlorite and silver nitrate effectively neutralizes the exogenous biota of woody explants. The stage of active vegetation is the optimal period of isolation of explants. To obtain virus-free regenerating plants, it is advisable to use apical meristems, callus tissue − leaf blades, active regeneration − microshoots. Stable regeneration system, its type, multiplication factor of Salicaceae plants are genetically determined. For the introduction of plants in vitro, active proliferation, rooting, microclonal propagation, it is advisable to use nutrient media according to WPM (McCown & Lloyd, 1981) and MS (Murashige & Skoog, 1962). For regeneration of plants by direct morphogenesis and activation of growth of existing meristems of an explant to apply the environment with cytokinins (BAP (6-benzylaminopurine), kinetin or 2-isopentenyladenine (2-ip), for rooting − with auxins NAA (α-naphthylacetic), IBA (3-indolylbutyric acid) and IAA (β-indolyl-3-acetic acid). Further research is aimed at optimizing the propagation protocols of Salicaceae plants in vitro.

Acute respiratory infections among under-five children from households using biomass fuel in Ethiopia: systematic review and meta-analysis

Acute respiratory infections are a serious public health concern across the globe, they are, however, prominently present in Sub-Saharan Africa. In Ethiopia, different primary studies were conducted in regard to the link between household biomass fuel use and acute respiratory infections among under-five children. However, there is no national study on the association between household biomass fuel use and acute respiratory is infections among under-five children. Thus, the aim of this systematic review and meta-analysis to estimate the pooled prevalence of acute respiratory infections and their predictors among under-five children in Ethiopia.The systematic review was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guideline. We systematically searched the databases: PubMed/Medline, Cochrane library, Google Scholar, Web of Science, and Scopus were searched to access potentially relevant articles conducted in Ethiopia about acute respiratory infections among under five children. Stata/SE 14.00 statistical software was used for analysis and the pooled prevalence with 95% confidence interval (CI) were presented using tables and forest plots. To assess the heterogeneity among studies, I square (I2) tests were used. Publication bias was checked by Begg’s and Egger’s regression test. The random effects meta-analysis model was employed to estimate the pooled prevalence and predictors of under-five acute respiratory infections A total of 7 studies with 8, 529 study participants were included in this meta-analysis. The pooled prevalence of acute respiratory infection among under five children was 17.75% (95% CI: 16.95, 18.55). Child holding during cooking (OR: 2.84, 95% CI: 1.48, 5.47) and using unclean sources of energy for cooking (OR: 0.38, 95% CI: 0.21, 0.70) were identified predictors of under-five children acute respiratory infection.In the current study, the pooled prevalence of acute respiratory infection among under-five children was relatively high. Child holding during cooking and using unclean sources of energy for cooking were significantly associated with under-five acute respiratory infections. Therefore, the policies and regulations enacted should address the barriers that impede the development of clean and efficient energy sources.

Analysis of Household Energy Expenditure in Umuahia North Local Government Area of Abia State, Nigeria

Understanding household energy expenditure is important to encourage policies that support the provision of cleaner, efficient and cost effective sources of energy to households. This project analyzed household energy expenditure in Umuahia North Local Government Area (LGA) of Abia State, Nigeria. The available domestic energy commonly used by the households’ was kerosene, firewood, Liquefied Petroleum Gas (LPG), charcoal, and electricity. The most used domestic energy types was kerosene (1st), followed by Liquefied Petroleum Gas (2nd); then firewood (3rd) and charcoal (4th). Multiple regression result for the factors influencing household energy expenditure in the study area shows that five out of eight explanatory variables employed in the model significantly affected the respondent’s households’ energy expenditure. These variables were household size, sex, household income, education and frequency of cooking. Also, results from the ordered probit model shows that the significant variables influencing the choice of domestic energy expenditure was age and gender of the household head, their income level, educational level and occupation. Lack of financial resources, high cost of cleaner energy types and distance from the place of purchase significantly affected household energy expenditure in the study area. It is recommended that provision of cleaner, efficient and cost effective sources of energy be made available to households.

A review on erosion of a Pelton turbine bucket

Hydro-power energy is the most efficient renewable energy sources in the world. India stands in the top ten hydropower generation countries list. Pelton turbine is a well-known hydropower extraction machine. The Pelton turbine buckets play an important role in the efficiency of the hydro turbine which is in continuous interaction with high velocity jet and there are possibilities of damages to the bucket in the form of erosion as water contains small debris as sediments. Eroded buckets greatly reduce the efficiency of the turbine. Attempt is made by researchers to developed co-relations to evaluate wear rate and efficiency reduction based on the practical data. The majority of erosion takes place at splitter areas. An erosion cannot be eliminated, but it can be reduced by some amount. The results of the mathematical model indicate that the effect of silt size to the wear rate is 0.0001 gram per gram of bucket weight for a particular silt concentration and the result of silt concentration to wear rate is 0.0007 gram per gram of bucket weight for a particular silt size. The normalised efficiency loss is increased to 0.13% for a specific silt size with the variation of silt contraction. The average wear rate is nearly 3.1 mm per year for laboratory-scale Pelton turbine bucket; which is manufactured from brass and bronze materials. The coating of various materials over the buckets are used by researchers to reduce erosion. Among all coating materials, WC-Co-Cr gives better results against erosion.

Green Synthesis of Nickel Borides Supported over Multiwall Carbon Nanotube As a Novel Catalyst for Hydrogen Evolution

The use of non-renewable fuels such as coal, oil, and natural gas significantly affects ecological system and human health. A substantial effort has been spending to find an eco-friendly and efficient energy source. Hydrogen appears as a green energy source which emits water as its byproduct during the combustion. The primary concern of hydrogen fuel is its dependence on fossil fuels in the production. Hydrogen feedstock material like Sodium borohydride (NaBH4) becomes potential, alternative source for manufacturing hydrogen fuel. However, the reaction between NaBH4 and water was slow and required a durable catalyst 1,2,3. The synthesis method of some catalysts is often expensive and require the use of various toxic chemicals4. The purpose of this study was to discover a green method of synthesizing nickel borides composite (NiB@MWCNT) and to utilize it in enhancing hydrogen generation reaction. The composite was synthesized from supported nickel metal organic framework (Ni-MOF-5) in the presence of Multiwalled Carbon Nanotube (MWCNT). The structure and composition of NiB@MWCNT was determined by Powder X-Ray Diffraction (PXRD), Scanning Electron Mircroscopy (SEM, Figure 1), Energy Dispersive X-Ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The catalytic efficiency of NiB@MWCNT was tested at temperatures of 281K, 295K, and 303K. The temperature trials indicated the activation energy was 43 kJ mol-1. NiB@MWCNT also showed a steady hydrogen generation of 44.4 ml through the reusable test.

Asymmetric Porous Membranes with Improving Mass Transfer for Proton Exchange Membrane Water Electrolysis (PEMWE)

Hydrogen is a promising and efficient energy source that can replace fossil fuels. Hydrogen can be obtained from various raw materials, including water. Recently, among various hydrogen production methods, high purity of hydrogen gas can be obtained by hydroelectricity. It also focused on water electrolysis, where efficient and continuous production of hydrogen is possible. Moreover, in terms of efficient and continuous production of hydrogen and environmental effects, PEMWE (Proton Exchange Membrane Water Electrolysis) has been evaluated as the most inspiring technology for producing high purity hydrogen of renewable energy and has the strength to discharge only oxygen by-products without hazards. These days, PEMWE research is surging as demand for hydrogen-based energy increases. Therefore, considerable research has recently been completed on membrane development for PEMWE. Currently, the PFSA (Perfluorosulfonic acid) polymer is used in PEMWE systems. A previous study reported that the thinner the PFSA membrane used for PEMWE, the lower the resistance of the MEA (Membrane Electrode Assembly), resulting in improved single-cell performance. Nevertheless, the single cell operates using a thick electrolyte membrane considering the safety aspects of the PEMWE system. Applying thick electrolytic membranes to PEMWE systems improves physical and chemical durability, but increasing the thickness of the MEA increases the resistance and mass transfer resistance, which degrades the performance of PEMWE. To compensate for these limitations, Previous studies have been conducted to reduce the resistance by modifying the catalyst structure constituting the MEA, but any case hasn't been reported to modify the structure of the membrane for PEMWE.Therefore, in this study, an asymmetric membrane was prepared to improve the performance of the PEMWE single cell by applying a porous structure into a thick membrane to ensure high durability. Research on asymmetric membranes has been conducted in energy fields such as vanadium redox flow batteries, fuel cells, and lithium-ion batteries. As a result of applying an asymmetric membrane to each energy research, it has been reported that the doping amount of the electrolyte increases due to the strengthening of the capillary force according to the porous structure, and accordingly, the ionic conductivity increases, thereby improving the performance of the cell. Besides, studies are showing that the diffusion rate of water and ions increases, and the internal resistance decreases due to the structure of the dense layer and the porous layer.In this study, to apply the performance improvement effect of the previous study to the electrolyte membrane for electrolysis, we referred the porous structure to confirm the performance of the PEMWE single cell. The porous layer of the asymmetric membrane was prepared using a solvent/non-solvent evaporation method. The solvent of the Nafion dispersion solution is alcohol, and the non-solvent is ortho-dichlorobenzene (ODB). The porous surface was prepared using the difference in boiling point and density between the solvent/non-solvent. Through the SEM analysis, the porous layer on the surface of the asymmetric membrane and dense layer on the bottom was observed. The Uniform round micropores distributed on the entire surface of the porous layer, which was below 10 μm. A cross-sectional view showed that the thickness of the asymmetric membrane is 175 ~ 180 μm. As a result of an EIS analysis, the asymmetric membrane showed a tendency to have lower ohmic and mass transfer resistance than the Nafion 117 membrane of the same thickness. Through the evaluation of a single cell performed under 80 ℃ temperature conditions, Nafion 117 was 1.5 A/cm2 and the asymmetric membrane was 2.5 A/cm2, about 1.67 times higher than Nafion117. The results of PEMWE single cell measurement confirmed that the porous structure of the asymmetric membrane improved the material transfer efficiency of the membrane, thus lowering the material transfer resistance, thereby improving the PEMWE performance.

Hydroxy Gas (HHO) Supplement of Ethanol Fuel Mixture In A Single-Cylinder Spark-Ignition Matic-Engine

<p class="TTPAbstract">Hydroxy Gas (HHO) has been identified as an efficient alternative energy source. HHO is considered an alternative fuel. It can be applied alone or mixed with other kind of fuels in different ratios. In this analysis, the composition of HHO-ethanol was mixed in different variations. Ethanol-HHO was chosen because of its high-octane rating yet low exhaust emissions, and ease of obtaining from engine products. It has been applied on fuel prepared by mixing it with gasoline in various ratios (E30-HHO, E40-HHO, and E50-HHO). The ethanol-HHO mixture has been used in a single-cylinder 4-stroke spark machine for performance, by varying speed of engine from 4000 to 9000 RPM and by applying a platinum spark plug electrode type. In experiments, engine power, average effective pressure (MEP), specific fuel consumption (SFC), and thermal efficiency have been analyzed. The analysis of combustion is accomplished by taking a pressure cycle in the chamber, monitoring the automatic control of engine control unit (ECU) and ensuring utilization in the same parameters of the various fuels tested, in addition to the fuel injection time, which increases with increasing ethanol percentage. Optimal power, MEP and thermal efficiency values are obtained with ethanol-gasoline (E50-HHO) mixture which is operated at 7200 rpm, an increase of about 5% compared to gasoline. Significant reduction in SFC was observed using HHO-ethanol mixture, reduced by about 6% compared to gasoline.</p>

Optimization of mixing in a Chinese dome digester for tropical regions

Optimization of mixing in a Chinese dome digester for tropical regions

Design of a future hydrogen supply chain: A multi period model for Turkey

There is no doubt that energy will have one of highest priorities in agendas of strategic plans of countries. Since fossil fuels are running out and carbon emissions are more important than ever, researchers seek alternative clean and efficient energy sources. One of the best alternatives is hydrogen. The systems in which hydrogen flows from its production to end users are called hydrogen supply chains (HSC). Since hydrogen is not in active use, its HSC infrastructure is not complete and should be planned very carefully. We study the design of HSC of Turkey to meet the hydrogen demand of the period between 2021 and 2050. Our aim is to minimize total cost of the HSC while meeting the demand of the transportation sector. We address the problem by using a mixed integer programming (MIP) model and derive several insights for the future HSC. The results show that while decentralization (being able to fulfill the demand from local production facilities) is 12% in the first period, this rate raises up to 48% by the end of the planning horizon. Analysis also reveal that almost all grids do not produce and import hydrogen simultaneously, i.e., they either produce or import hydrogen. The results are robust in the sense that solutions of different optimality gaps have minor differences in terms of established facilities.

Evaluating renewable energy choices among rural communities in Nigeria. An insight for energy policy

PurposeThis study aims to examine the effects of policy incentives and cost on the choice and use of renewable energy in North-Central Nigeria.Design/methodology/approachThe data for this study are collected from a sample of 290 respondents drawn from across 6 states in North-Central Nigeria, including the Federal Capital Territory. This study uses descriptive statistics and multinomial logistic regression to analyze the data.FindingsThe findings reveal that there is a huge potential demand for renewable energy sources (particularly solar photovoltaic) in the rural communities in Nigeria. It also indicates a positive and highly significant relationship between the level of awareness, availability and income and the use (consumption) of renewable energy sources among the rural communities. Furthermore, the cost of installation and maintenance of renewable energy, its reliability and availability are significant determinants of renewable energy choices among rural inhabitants in Nigeria.Practical implicationsThe authors submit that inefficient policy strategies, high cost of installation and lack of awareness remain the major hindrances to the use of more efficient renewable energy sources. From a policy point of view, a viable strategy for effective use of renewable energy sources is the involvement of government, development partners and agencies for the funding of renewable energy technology in the rural sector of the country. The usage of modern renewable energy would increase if policy incentives are aimed at covering parts of the maintenance and installation cost of renewable energy users. The authors recommend that apart from creating awareness on the benefits of renewable energy, policymakers should provide a desirable policy environment for private energy firms to supply renewable energy at an affordable cost to the rural communities in Nigeria.Social implicationsA majority of the rural households in Nigeria, as shown in this article, are poor and therefore use firewood as their main source of cooking energy because of the cost of renewable energy.Originality/valueDespite the abundance of renewable energy sources and government effort at improving renewable energy use, more than 15 million people live without access to electricity and 54 million are without modern energy services for cooking and lightening in Nigeria. A total of 61% of these people live in rural areas. Therefore, this study is novel in providing energy policy insights for rural communities in North-Central Nigeria.

A combined experimental and simulation approach for short circuit prediction of 18650 lithium-ion battery under mechanical abuse conditions

Abstract Lithium-ion batteries are considered an efficient energy source for current electric vehicles (EVs); however, the safety of these batteries is vital when it comes to large-scale deployment. Short circuit of batteries is one of the concerns as it can spread quickly within the battery module or pack if not controlled at the cell level. In this paper, single lithium-ion battery cell is investigated where mechanical abuse conditions are applied to investigate short circuits and propagation of failures due to short circuits. The numerical simulation tool LS-DYNA is used for the battery-layered model, each layer thickness is considered 0.3 mm, and concentrically layered formation is used for this purpose. An improved element size of 0.5 mm is used for steel casing and 1 mm for all other layers. A total of 27 layers are simulated in a single cell and the innermost radius is considered 1 mm. Displacement at short circuit, mean temperature at the short circuit, and mean maximum temperature change criterion are used to understand short circuit and propagation of failures. Simulation models are developed for quasi-static load analysis to understand the severity of failures, which can be used to reduce the risk of sequential failure of batteries in the battery pack.

A Multi-period Optimization Model for the Design of an Off-Grid Micro Hydro Power Plant with Profitability and Degradation Considerations

Micro hydroelectric power is a clean and efficient source of energy that has been used for the electrification of rural off-grid communities. However, numerous micro hydro installations have failed as caused by factors such as poor site selection and uneconomical design of materials, among others. A multi-period mixed integer linear programming model for the design of an off-grid micro hydro power plant is then developed. The proposed model is able to provide technical specifications such as the penstock dimensions, turbine choice, weir height, and site choice in order to fulfill a community’s demand while simultaneously maximizing the net present value of the investment. The model may choose among different productive end uses, with each being subject to a respective investment cost as well as a set-up time and degradation rate. Computational experiments demonstrate the different capabilities of the model to address real-life scenarios such as population growth and streamflow variability. An increase in energy consumption due to population growth leads to the requirement of a more powerful turbine. Capacity limitations likewise prevent the community to invest in productive end usage. Meanwhile, streamflow variability potentially reduces the capability of the power plant to produce electricity. In these instances, batteries had to simultaneously be used in order to augment the increase in energy requirement.

Performance evaluation of renewable energy R&D activities in Malaysia

This study explores the performance of R&D activities in five renewable energy resources, namely, solar, wind, biomass, biogas, and mini hydro. The case study is Malaysia and considers the data from 2012 to 2017 in relation to two policy thrusts, namely, systematic R&D program and human capital development toward the renewable energy deployment in Malaysia. This research uses the DEA method to evaluate the efficiency of the R&D activities of renewable energy resources considering the variables in the government’s renewable energy policy. Result indicates that mini hydro is the most efficient renewable energy source in Malaysia, whereas wind is the most inefficient one from the perspective of R&D activities. Although the R&D activities related to mini hydro are few, the output of installed capacity is proportional to the input in R&D activities compared with other renewable energy resources. Wind is the most inefficient renewable energy resource due to its high R&D activities compared with those of other sources, and installed capacity is the lowest among others.

Modeling interfacial tension of methane-brine systems at high pressure and high salinity conditions

Natural gas which consists mainly of methane (usually more than 90% in volume), is becoming increasingly an important and efficient source of energy because of the lower greenhouse gas emissions and air pollution. Achieving satisfactory recovery factors in gas reservoirs is sensitive to the methane-brine/water interfaces induced by the interfacial tension (IFT) between these systems. Accordingly, accurate determination of IFT of the systems methane-brine/water is extremely important for natural gas production. In this paper, several intelligent models were implemented to accurately estimate interfacial tension (IFT) of the systems brine/pure water-methane under wide temperature, pressure and salinity ranges of (278.1–477.59 K), (0.01–260 MPa) and (0–200,000 ppm), respectively. The established models were based on an extensive databank including 879 experimental measurements. The implemented intelligent models in this study were Extreme Learning Machine (ELM), Radial Basis Function (RBF) neural network, Multilayer Perceptron (MLP), Least Square Vector Machine (LSSVM), and Generalized Regression Neural Network (GRNN). Various optimization algorithms were applied for improving the learning phase of these models. Furthermore, a Committee Machine Intelligent System (CMIS) scheme was proposed by linking the best-found paradigm under a linear single model. The results showed that all the developed intelligent-based paradigms exhibit reliable prediction abilities. In addition, it was found that CMIS and GRNN are the fittest paradigms with overall absolute average percent relative error (AAPRE) values of 1.117% and 1.003%, respectively. Besides, the performance assessment revealed that our best paradigms outperform the existing approaches. Finally, the sensitivity analysis revealed that salinity has a slight impact on IFT.

Experimental comparison of CO2, N2, and CH4 permeability of water saturated coals of different ranks

ABSTRACT Coalbed methane is a kind of highly efficient and clean energy source. The permeability of coal seam affects the application of gas extraction. There are so many factors affecting gas permeability, such as gas pressure, temperature, moisture content, confining pressure, and coal rank. We experimentally investigated gas permeability of three different coals at four different temperatures (23°C, 34°C, 45°C, and 60°C) and three different moisture contents (dry, medium moisture and moisture-saturated coals). Injection gas pressure varied from 1 MPa to 6 MPa (up to 8 MPa for N2) at constant axial confining pressure of 9 MPa. The results show that under constant axial and confining pressure conditions, with the increase of gas injection pressure, the permeability of N2 and CH4 shows a “V”-shaped change trend, that is, “inflection point”; CO2 permeability decreases with the increase of gas injection pressure. The permeability of coal core samples decreases with increasing temperature, caused by thermal expansion, decrease of gas absorption and increase of porosity. As the temperature rises, the decline gradually flattens. The permeability of coal core samples decreases with the increase of moisture content, related to moisture and gas competitive adsorption, coal porosity reduction. The permeability of high rank coal is lower than the medium rank coal under the same experimental conditions, caused by the pore structure of coal sample.

Economic growth or electricity, what came first in Spain after 1958?

PurposeWith the opening up of the economy since the 1959 Economic Stabilization Plan, was it the production of electricity that drove the growth of gross domestic product (GDP) in Spain or, on the contrary, was it the growth of GDP that drove the production of electricity well into the 21st century? The purpose of this paper is to answer this question.Design/methodology/approachA cointegration approach based on the studies conducted by Pesaran and Shin (1999) and Pesaranet al.(2001) is applied, as it is suitable for short data series like those used in this paper.FindingsThe results of this paper allow us to conclude that electricity production boosted economic growth in Spain during the period under study, confirming the growth hypothesis.Research limitations/implicationsThe results of this paper should be interpreted with caution, as electricity today amounts to less than a quarter of the total amount of energy used in Spain. It was not possible to incorporate other inputs to the production function (such as other energy inputs, technological or human capital), but the methodology used avoids the problems of omitted variables and of autocorrelation.Practical implicationsThe results show that a small economy with limited resources, such as the Spanish one, is more vulnerable to energy shocks than other energy-sufficient economies. As Spain is a country with high energy dependence from abroad, the government must first ensure the electricity supply. Increased availability and access to different sources of electricity will improve the outlook for the Spanish economy. Conversely, a shortage in supply of electricity will constrain the regular pace of economic growth.Social implicationsSpain should investigate and explore more efficient and cost-effective sources of energy, in particular the renewable energies, as traditional energy sources will be scarce before long.Originality/valueThis paper differs from previous ones carried out for Spain in several aspects: it considers a broader period of time, from 1958 to 2015; the relationships between electricity production and GDP are analysed for the first time in a neo-classical production function where electricity, capital and employment are considered as separate factors; and a cointegration approach based on the studies conducted by Pesaran and Shin (1999) and Pesaranet al.(2001) is applied, as it is suitable for short data series like those used in this paper.

A dish-stirling solar concentrator coupled to a seasonal thermal energy storage system in the southern mediterranean basin: A cogenerative layout hypothesis

In the future, renewable energy sources will increasingly represent an efficient energy source capable of meeting the demands of residential and industrial buildings avoiding the emissions of greenhouse gases into the atmosphere. In this paper, a heat and electric power cogeneration plant implementing a field of dish-Stirling collectors, a seasonal geothermal storage and a system of water-to-water heat pumps is proposed for the first time. The cogeneration plant has been designed both to supply thermal energy to the heating system of Building 9 of the Department of Engineering in Palermo and to produce electricity. The operation of the plant has been tested by means of hourly-based numerical simulations that have been carried out using a numerical model implemented with Transient System Simulation Tool. The experimental data of a pilot dish-Stirling collector, located in the same area, has been used to carefully calibrate the numerical model. Using energy and economic performance indicators, it was possible to select the best configurations among 1440 analysed cases. Results of simulations show that with the best plant configuration, it is possible to cover 97% of the building's annual thermal loads with energy produced by the solar system. The remaining 64% of electrical energy produced by the electric engines is free to be used for other applications. Financial analyses have shown that market penetration of this type of plant would need a strong support through incentives.