The beam‐down design is standing out as a very promising technology in the field of solar central receiver systems. In this paper, we show that the use of concave heliostats strongly improves the overall performance of the system, allowing for a better concentration of the solar radiation at the receiver. To this aim, the spot at the horizontal plane containing the lower focus of the secondary reflector is analyzed under different conditions, such as secondary reflectors of different eccentricities and solar fields composed of concave or flat heliostats. The performance analysis of a realistic beam‐down system is also proposed to stress both the feasibility of the plant and the need of using concave heliostats. This study has been conducted with the use of the CRS4‐2 numerical code (an acronym for CRS4 research software for Central Receiver Solar System Simulation S), developed in our laboratory.
Hydrogen sulfide (H2S) coming from oil and gas refineries, after purifying in amine sweetening unit, is routed to Sulfur Recovery Unit (SRU), wherein converted to elemental sulfur. In order to compensate the low performance of SRU, the remained acid gas is then fed to Tail Gas Treatment (TGT) unit for more processing. TGT unit increases the overall sulfur recovery and therefore, decreases the environmental pollution. The absorber column is an important equipment in the TGT unit. The main function of this column is the selective absorption of H2S in the presence of CO2. In this paper, the effect of operating temperature on the performance of TGT absorber column will be investigated. For this purpose, a typical industrial TGT unit is simulated and then, the results are illustrated and analyzed in terms of technical points of view.
Indonesian brown‐coal with high ash content is gasified by two microwave steam‐plasmas heating up a reaction chamber of 1145 liters in a swirl‐type gasifier for production of hydrogen‐rich synthetic gas. With additional heating of the gasifier by a partial oxidation of coal, the inner temperature of the gasifier can be increased from 1100C to 1700C. In this regard, the influence of the gasifier temperature on the gasification efficiency can be investigated in this experiment. The carbon conversion rate and cold gas efficiency are less than 90 percent and 65 percent, respectively, for the inner temperature of the gasifier below 1400C. On the other hand, the carbon conversion rate at the chamber temperature of 1600C is almost 100 percent, ensuring a complete gasification of carbons in a low‐grade coal. The cold gas efficiency of the hydrogen‐rich synthetic gas at the high inner temperature of the gasifier wall is 84%, very high in a relatively‐small gasifier like the experiment here. The total calorific power of the synthetic gas can be easily more than 500kW in this particular experiment.
This article presents a study about environmental impacts resulting from the construction and operation of wind power farms. For this matter, a research in national and international literature reviews was carried out, as well as technical visits to wind power plants in several Brazilian states and discussions with the working group about environmental licensing of wind mills in land surface of the Ministry of Environment, which FEAM (Fundacao Estadual do Meio Ambiente – Environmental State Foundation) takes part, aiming the formation of plans, projects and wind power programs, according to the provisions of the “Carta dos Ventos” (Charter of Winds). These surveys were carried out in the last three years and used as base for the implementation of relevant work to the theme. The article discusses the impacts in biotic and physical environment, physical and socioeconomic status, identifying the biotic environment, which results from the removal of vegetation, intervention in fauna, degradation of the affected area, changes in the hydrostatic level of aquifer, and still on the socio‐economic environment, the issue of noise, visual impact, the corona visual or glare, the electromagnetic interference, the strobe effect and the local interference. The noise and the strobe effect can harm the health of people near the plants, but the distance can avoid such effects. The generation of electricity through wind farms has major advantages in reducing greenhouse gases and CO2 concentration during operation when compared with other sources. However, the environmental impacts coming from the implementation and operation of a wind power plant cannot be neglected.
The combined efficiency of simple hybrid photovoltaic/thermal (PV/T) solar water system is less due to its low concentration ratios and, non-standardization of PV heat exchanger surfaces. The simple and cost effective technique to increase PV/T efficiency is the use of reflectors which will boost solar radiation on PV module surface. Flat reflectors fitted to sides of PV module of hybrid system helps in improving the concentration of solar radiation on it. This paper provides design and performance analysis of spiral flow heat exchanger used in hybrid system with flat reflectors of aluminum sheets. The experimental results like performance efficiencies of photovoltaic, thermal, and combined photovoltaic/thermal system over a range of actual working conditions are discussed and evaluated for latitude of Mumbai. The results at solar radiation of 950 W/m2 and water mass flow rate of 0.042 kg/sec through heat exchanger with reflectors showed combined PV/T efficiency of 71.40 % with PV efficiency of 12.40%.
Shipping is a growing sector in the global economy and its contributions to global greenhouse gas (GHG) emissions are expected to increase. Energy efficiency has always been an important factor to minimize GHG emissions. Waste heat recovery (WHR) systems can be used for both improving energy efficiency and reducing energy consumption and GHG emissions. Organic Rankine Cycles (ORC) systems are the most widely used technology for low temperature heat recovery from exhaust gases in the industrial applications. But this system is not widely used in ship applications. In this study thermodynamic performance criteria of ORC system for a container ship are developed and thermodynamic, environmental and economic effects of the system are analyzed. It can be achieved additionally 2% reduction for the ship fuel consumption by utilizing the ORC system.
World is facing acute energy crisis. Attention is being directed towards other unconventional sources of energy. Recently more attempts are being made to produce biodiesel as an alternative source of ecofriendly energy using biomass of plant origin. One such biomass is Jatropha curcas. But during biodiesel production from 100 kgs of Jatropha seed only 30% of oil is extracted while 70% of de-oiled cake is generated as a byproduct. Based on this fact work on enhancement of biogas by Jatropha amendment was studies in detail and studies showed that 20% amendment of Jatropha oil cake seems optimum with respect to gas production and volatile solids reduction. It is preferable to run the digester with optimal addition because addition of higher volume of Jatropha may pose a problem and may be rate limiting factor.
This paper purposes to examine the relationship between energy consumption and economic growth in OECD countries during the period of 1980–2010. The panel data methods are used to analyse the causal relationship between energy and growth. It is important to see observe the ways of causality between energy consumption and economic growth for the policy-makers. The research outcomes reveal that there is significant correlation between energy consumption and economic growth in OECD countries.
This paper is the modest attempt towards experimental study in lab backed with field work for energy efficient cooking devices based on various solid biomass fuel. The study is designed in such a way so as to compare these energy efficient cook stoves as opposed to traditional cook stoves in terms of their thermal efficiency, time of cooking, fuel consumption; finally being helpful in assessing the sustainability of such new technology interventions particularly in rural areas.
This paper presents a closed-loop control of a 440kW fuel cell system including power electronics and grid side filters. Simulation results show the dynamics of a phosphoric acid fuel cell (PAFC) and its associated power electronics including grid connection. The proposed model is based on empirical equations and Simulink blocks. The modeling and simulation is done in Matlab/Simulink software with its Power System Blockset (PSB). This model mathematically calculates cell output voltages and their consequent losses. Moreover, this model includes dc power conversion of fuel cell output into ac and grid interface. Presented model is simple and easy to understand.
This paper proposes a wind turbine and battery storage based packet energy system. The proposed energy packet network can be used to make renewable energy sources more practical and supply energy on demand. The flow of energy in the energy packet network is controlled by a Smart Energy Dispatching Centres (SEDC). SEDCs receive the energy requests from the customers and it tries to optimize the energy flows by making the best use of renewable energy resources, existing price and policies. The proposed energy system can take energy flow instructions from a SEDC. In the present analysis a small wind energy system with battery storage has been simulated in Matlab/Simulink. The system has been modelled using low order transfer functions. Random switching has been done to get energy packets from the model. A prototype of the battery based energy storage system has been designed and implemented. Lab tests and simulation results indicates that the designed packet energy network system is able to provide energy packet as required by the grid. Additionally the output power from a very large energy packet network is also found to be stable with the existence of large load fluctuation.
This paper analyzes the permanent magnet synchronous motor used for electric vehicle, and the influence of the built-in “V” type size parameters on direct axis inductance, quadrature axis inductance as well as PM flux linkage. The research is about the change rule of permanent magnet torque and reluctance torque. In the view of the optimal driving system, it summarizes the design method for rotor magnetic circuit structure of PMSM used for electric vehicle, and analyzes the influence on Flux Weakening ability of the main electromagnetic parameters. It also includes the design of two sets of prototype of 25 kW with different rotor structure. Experimental results of the speed regulation characteristic curve and efficiency MAP verify the feasibility of the design rules proposed in this paper.
In this study, performance of MFC using three different mediators was investigated in terms of power density and internal resistance. Methylene blue (MB), neutral red (NR) and 2-hydroxy-1,4-naphthoquinone (HNQ)mediators were used to increase power generation in MFC with the mediator concentrations of 50, 100, 200, 300 and 400 µM. The maximum power densities were recorded as 36, 31 and 18.7 mW/m2withthe mediators of MB, NR and HNQ corresponding optimal mediator concentrations of 300, 200 and 50 µM, respectively. Further, it was observed that internal resistance changed with mediator concentration.
In the industrial plants where the sugarcane bagasse is used for self energy generation, it is possible to produce more power than it is required for the sugar milling process. Therefore, the excess of power can be exported to the electricity grid in a process known as cogeneration. In the present work, the potential of sugarcane bagasse generated in the several plants in the Brazilian State of Minas Gerais is evaluated for energy production in the process of cogeneration. The main aim is to demonstrate the possibility of increasing in the cogeneration potential using the bagasse at Minas Gerais. The results show, in theory, that the production of electricity for export to the regional grid would be significatively intensified if several actions could be taken as, for example, better use of the total bagasse generated in Minas Gerais and, mainly, providing the modernization of the plants for cogeneration. Predictions considered cogeneration using all bagasse produced in Minas Gerais according with data from the 2010/2011
With the rapid development of highway construction and automotive industry, the transportation industry is one of the main carbon source. In the paper, the carbon measurement model established through the analysis of factors influencing highway carbon emissions. “Turner” model was used to prove the validity of the carbon measurement model. The CO2 concentration measurement software has been completed based on VB.NET technology. Finally, the carbon measurement model was verified through examples.
This paper presents a combinatorial standalone permanent magnet synchronous generator (PMSG) based variable speed wind turbine (VSWT) and small-size superconducting magnetic energy storage (SMES) system into the DC microgrid system. The principal purpose of SMES system is to preserve power balance by absorbing power during peak wind generation and to release it during low power generation. This work accomplished by describing the optimized design of the SMES solenoid coil, ensuring the desired energy storage capacity based on the simulated annealing (SA) algorithm. More importantly, the new control technique is developed for bi-directional DC-DC converter to level output power of the wind turbine depending on the demand thereby reducing the capacity of the DC-DC converter system. Detailed simulation studies implemented in PSCAD/EMTDC corroborate the superior robustness and balancing performance of the proposed micro-SMES controller with an optimal coil size under various situations including variable wind speed. This combination will result in “scaling-factors” knowledge through downsizing strategy which will lead to the most efficient system from cost cutting, energy savings, and downsizing viewpoints.
The Comunitat Valenciana is the largest orange producing area in the European Union. During the past decade, orange cropping has been under severe economic stress arising from increasing competition from less-costly foreign imports. Consequently, farm-gate prices are depressed to the extent that it has effectively fallen to the same or below the cost of production. Orange groves are being abandoned in many instances. Preliminary assessment showed that conversion of orange grove in Ribera Baixa to produce energy does not appear to be a viable option. Electric power generation is not practicable in the absence of government feed-in tariff subvention. Photovoltaic power generation might however be practicable for self consumption under certain circumstances. Use of crude microalgal oil does not provide sufficient economic benefits to the prospective on-road end uses, in absence of any excise tax exemption. The production yield of crude moringa oil is far below that of crude microalgal oil to be of competitive interest.
Developing optimum decision policy for gradual replacement of conventional energy sources by clean ones is an important field of current research and the main concern of this article. Eight main energy sources are considered and the decision policies are formulated with the objective of minimizing the implementation and environmental costs while meeting the electricity demand during the entire plan period. The selected energy sources are Coal, Petroleum, Natural Gas, Hydropower, Wind, Solar, Geothermal and Biomass. A nonlinear dynamic Lotka-Volterra model, first introduced in Miah, Ahmed and Chowdhury [1] and later extended in Parsa, Ahmed and Yagoub [2], is used for modeling the dynamic changes in the level of electricity generation from each of the eight available energy sources. Optimal control theory is used to find the optimum decision policies for integration of renewable energy sources into the national power gird of any country. As a case study for our numerical results, official released data of United States Energy Information Administration website is used for the level of electricity generation from each of the energy sources mentioned above. Different scenarios are considered for the electricity demand. These range from U.S prediction for twenty years plan period to two percent annual growth rate for different plan periods of twenty and thirty years. The proposed methodology is general enough and hence applies to other energy problems with slight modifications based on the planner's objectives.
The amount of heat extracted from bottom surface of PV module of hybrid solar water system is strongly influenced by the air gap between the bottom surface of module and top surface of heat exchanger. The heat transfer analysis between these two surfaces is studied in this research work. For this, outside heat transfer coefficient of stagnant air was calculated & found to be 50 W/m 2 0 k. By using desired correlation, air gap between these surfaces was found to be 0.53 mm. For this air gap with solar radiation of 918 W/m 2 and mass flow rate at 0.035 kg/sec, this system generated a combined PV/T energy with efficiency of 53.7 % with maximum PV efficiency of 11.7 %. These results showed that heat transfer from these surfaces had been strongly influenced by the air gap or air resistance.
