Specific Power Production Research Articles

Performance Analysis of Organic Rankine Cycle with Internal Heat Regeneration: Comparative Study of Binary Mixtures and Pure Constituents in Warm Regions

There are various organic compounds that can be utilized in the organic Rankine cycle as working fluids. The selection of a suitable working fluid is complicated due to the large number of options and factors affecting the choice, such as thermodynamic properties, environmental impact, cost, etc. This study evaluates seven different pure organic compounds and twenty-one of their binary zeotropic mixtures as potential working fluids for the organic Rankine cycle powered by a heat source at 200 °C. The pure organic fluids show higher exergy efficiency, higher specific net power output, and lower heat exchange area requirements compared to the binary mixtures. Among the pure fluids, RE347mcc performs the best in terms of exergy efficiency, followed by neopentane, isopentane, and pentane. Cyclopentane exhibits the highest power production capacity per unit mass flow rate of the working fluid. Two mixtures, pentane/Novec 649 and cyclopentane/Novec 649, showed significantly higher exergy efficiency than their individual components, but at significantly lower specific power production capacity. The study presents an interesting trade-off between exergy efficiency and heat exchange area, indicating that a small increase in exergy efficiency can lead to a large decrease in the required heat exchange area. The outcomes of this study can help in selecting suitable working fluids for ORC operation with a heat source at 200 °C.

Estimating the limits of renewable energy from phytomass

The energy production from phytomass on agricultural and forest lands can be calculated on the basis of the annual production of hydrocarbons (cellulose, starch, sugar, etc.), without needing to take into account the type of phytomass and the mean-weighted specific power production per unit of land area. Land with a mostly uniform climate and soil class produces similar specific power per unit of land area. It was proved in the case of the Czech Republic, where the meanweighted value of specific power production has been calculated as 3.16 kW/ha. Biomass energy can be released in three ways in which conversion takes place. i) direct phytomass combustion, ii) conversion to methane (biogas), iii) conversion to bioethanol. Conclusions about the effectiveness of different conversion methods were obtained by executing the enthalpy balances of the individual transfer processes. The method using methane (raw gas) seems to be the most energetically advantageous. The close connection between the circulation of CO2, H2O, and O2 has been quantified. The same amount of water as CO2 is produced and remains int in the atmosphere, and it significantly reflects radiation away from the ground. Cooling heat flux can be lowered about 1.6 times, thus contributing to climate change.

A Harmony Search Method for the Estimation of the Optimum Number of Wind Turbines in a Wind Farm

During the last decades, renewable energy production has significantly increased in an effort to produce clean energy that will not affect the environment. Governments around the world are focusing on reducing greenhouse gas emissions by increasing the utilization of renewable energy sources in the power chain. Wind farms and wind generators are the main renewable technology that are used worldwide. The main scope of wind farm designers is the achievement of the maximum possible power, restraining the installation cost that is related to the use of a specific number of wind turbines for specific power production, and considering the area of land to be occupied. A harmony search method is presented in this paper for the determination of the optimum number of wind turbines in a wind farm and the total electric power produced. The method is applied for comparison purposes on data from previously published methodologies proving its accuracy and effectiveness. The harmony research method can be used in the studies of wind farm designers aiming to reduce installation costs.

Concentration and Temperature Effects on Water and Salt Permeabilities in Osmosis and Implications in Pressure-Retarded Osmosis.

Osmotic power extracted from the mixing of freshwater with seawater is a renewable energy resource that has gained increasing attention during recent years. The estimated energy can significantly contribute to the production of power worldwide. However, this power production will be subject to variation due to both local conditions and seasonal variation. The present paper explores the effect of concentration and temperature on water and salt fluxes in osmosis at zero transmembrane pressure for five different membranes. Further, the measured fluxes have been utilized to model water and salt permeabilities (A and B), and the structure parameter (S). The observed flux variations at different combinations of concentration and temperature have been ascribed to skin properties, i.e., changes in A and B of each membrane, whereas S was assumed constant within the range of concentrations and temperatures that were tested. Simplified equations for the variation in A and B with temperature and concentration have been developed, which enable A and B to be calculated at any concentration and temperature based on permeabilities determined from osmotic experiments at standard test conditions. The equations can be used to predict fluxes and specific power production with respect to geographical and seasonal variations in concentration and temperature for river water/seawater pressure-retarded osmosis. The obtained results are also useful for forward osmosis processes using seawater as draw solution.

Reliability analysis of multi-state system with three-state components and its application to wind energy

In most real life situations, the system’s components contribute differently in different performance levels. Such a situation can be modeled by systems with multi-state components having more than one working status, e.g. perfect functioning, and partial working. In this paper, a multi-state system that consists of two types of three-state components is defined and studied. An explicit formula for the probability that the performance of the system is at least a given level is obtained for the most general case when the components are statistically dependent. The model is applied to evaluate the wind power system that consists of two wind plants in different regions. An optimization problem is formulated to find the optimal number of wind turbines that must be installed in the wind plants by minimizing the total cost under specific power production.

Joint specific power production in cycling: the effect of cadence and athlete level

Introduction When increasing cadence, there is increasing knee joint contribution and decreasing hip contribution to external power [1, 2]. Increasing power output leads to a decrease in knee contribution and an increase in hip contribution [2, 3]. Low cadence (<60 rpm) interval training is a widely used training method, but previous studies have primarily focused on cadences ranging from 60 to 180 rpm, without examining the effect of low cadence on joint contribution. The present study investigates joint-specific power production in recreational and elite cyclists during cycling at a range of different cadences.  Methods Ten recreational cyclists and nine elite cyclists (Continental and ProTour-level) performed cycling bouts at seven different pedaling rates (40 to 100 and freely chosen) and four intensities. Intensities were set at 55 (Int55), 85 (Int85) and 100 % (IntLT) of predetermined lactate threshold (LT) in addition to average 20 min all out power (Int20min). All tests were performed on an indoor cycle trainer with the participants’ private road bike. Joint specific power was calculated from kinematic measurements and pedal forces using inverse dynamics  Results Mean work rate at the four different intensities were 154 W (Int55), 240 W (Int85), 282 W (IntLT) and 322 W (Int20min). The elite group had an average of 32.6 % higher LT and 38.4 % higher 20 min all out power than the recreational group. The knee joint was the major power producer at all cadences, with the exception of low cadence (<60 rpm) where the hip joint were the major power producer (fig. 1.). There was a significant main effect of cadence and intensity on the relative contribution of the hip, knee and ankle joints. At cadences above 60 rpm, increasing cadence led to a significant decrease in relative hip joint power and an increase in relative knee joint power. However, there was no effect of cadence on the relative joint contribution at cadences below 60 rpm. Relative knee joint power increased with increasing intensity, however the relative hip joint power only increased from low to moderate intensity. The elite group had significantly higher relative hip joint power and lower relative knee joint power compared to the recreational group.  Discussion and Conclusions The present study demonstrates that increasing cadence leads to a decrease in relative hip joint power and an increase in relative knee joint power, however, the effect of cadence only occurred above 60 rpm. Elite cyclists have higher relative hip joint contribution, and lower relative knee joint contribution at all cadences and intensities compared to recreational cyclists. This is to the author’s knowledge the first study to report an effect of athlete level on relative joint specific power in cycling. The findings related to the effect of cadence on joint specific power complies with earlier research [1, 2] with the exception of the effect at low cadence (<60 rpm). The lack of an effect of reducing cadence below 60 rpm may have implications for how low cadence training is carried out.

Analytical and Comparative Study of a Mini Solar-Powered Cogeneration Unit Based on Organic Rankine cycle for Low-Temperature Applications

In this paper, we analyze characteristics of a small Combined Heat and Power (CHP) system based mainly on Organic Rankine Cycle (ORC) and heating plant in actual series connection regarding the low-temperature heat carrier heated by purely solar flat collector field. Simultaneously and for specific power production, comparison of this layout with stand-alone ORC, and with the traditional ORC-CHP imposing gain of condenser heat for heating aims, in second step, has been conducted. For evaluation, energetic and design criteria have been determined opposite the heating effects and also temperatures of the heat source and sink. The simulations addressed interesting optimization ratios till 24 % for the power unit throughout this series CHP utility versus single power generation at the same conditions tested. Moreover, the high heat source temperatures and CHP ratios improve the performance of the overall series plant, while the high supply and return temperatures have negative effects. Finally, the ORC-CHP scheme handled here highlights distinctive exploitation aspects and more suitability in wide range of application in comparison to yielding the high-temperature condensation heat of ORC, especially at low ambient temperatures, high supply and heat source temperatures. So, it can be advised to be adopted instead of the two other strategies.

Resource scarcity in palladium membrane applications for carbon capture in integrated gasification combined cycle units

Abstract Recently, many reviews on pre-combustion CO 2 capture (CCS) in an IGCC plant have been focused on the techno-economic performance of palladium-based membrane reactor modules downstream of conventional steam reforming or shift reactors. Although the determination and minimisation of the amount of palladium necessary for a specific power production capacity has been the target of many research studies, surprisingly little attention has been paid in the open literature to the availability of this metal in the large quantities required for large scale applications. To fill this gap, the scope of this work was to compare the amount of palladium needed for pre-combustion CCS with Pd-membranes and the available production capacity of palladium. Two specific techno-economic studies with a different net IGCC power output were selected from the literature. In each case, the amount of palladium that is necessary for the plant to be in operation was compared with the world supply and demand for palladium. The results show that even for a power plant of “only” 1 GWe net electricity production utilizing membranes with the best reported performance, a relatively large (∼0.7%) amount of palladium is required compared to the total world supply. Considering the total worldwide electricity production from fossil fuels (14,455 TWh in 2010) a tremendous increase in the world supply of Palladium would be required to redirect from the traditional IGCC power plants without CO 2 capture units to the new membrane technology. We conclude that large scale pre-combustion capture of CO 2 using palladium membranes seems to be unfeasible and research on Pd-based membrane reactors should focus on small(er) scale applications.

After fogging process in water injected gas turbine systems

In gas turbine system with after fogging, water droplets are injected after compressor. After fogging could have more significant potential for enhancement of specific power production compared to inlet fogging alone, since a larger water injection rate is possible. Transient analysis of after fogging process is carried out by using a heat and mass transfer modeling on water droplet evaporation. Transient variables such as droplet diameter and air temperature are evaluated as the droplet evaporation proceeds for different values of initial droplet diameter, pressure ratio of compressor, and water injection ratio. The evaporation time for injected droplets are also estimated. Present results show that the evaporation time decreases sensitively with increasing pressure ratio or initial droplet diameter. However, the effect of water injection ratio on evaporation time is relatively insignificant unless water injection ratio is near the critical ratio.

Estimation of wind turbines optimal number and produced power in a wind farm using an artificial neural network model

One of the most significant issues in the design of a new wind farm is the estimation of optimal number of wind turbines that has to be installed in it. The goal of every wind farm designer is the production of the maximum possible power, minimizing the installation cost. The cost can be significantly reduced using the minimum required number of wind turbines for specific power production, occupying at the same time the least possible acreage of land. In this work an artificial neural network (ANN) model is developed which has the ability to estimate the optimal number of wind turbines and the total produced power in a wind farm. The ANN model’s results are compared with those of earlier studies that have followed other approaches, proving that the ANN model is well working and has an acceptable accuracy. The proposed model can be useful in the studies of wind farm designers as a supportive tool for the estimation of the optimal number of wind turbines in a wind farm.

Application of Powell's optimisation method for the optimal number of wind turbines in a wind farm

The goal of every wind farm designer is the production of the maximum possible power and minimising the installation cost. The cost can be significantly reduced using the minimum required number of wind turbines for specific power production, occupying at the same time the least possible acreage of land. In this work, Powell&apos;s optimisation method has been used for the estimation of the optimal number of wind turbines and the total produced power in a wind farm. The method&apos;s results are compared with those of earlier studies that have followed other approaches, presenting its effectiveness. The proposed method can be useful in the studies of wind farm designers as a supportive tool for the estimation of the optimal number of wind turbines in a wind farm.

Power-scaling performance of a three-dimensional tritium betavoltaic diode

Three-dimensional diodes fabricated by electrochemical etching are exposed to tritium gas at pressures from 0.05 to 33 atm at room temperature to examine its power scaling performance. It is shown that the three-dimensional microporous structure overcomes the self-absorption limited saturation of beta flux at high tritium pressures. These results are contrasted against the three-dimensional device powered in one instance by tritium absorbed in the near surface region of the three-dimensional microporous network, and in another by a planar scandium tritide foil. These findings suggest that direct tritium occlusion in the near surface of three-dimensional diode can improve the specific power production.

Influence of anodic biofilm growth on bioelectricity production in single chambered mediatorless microbial fuel cell using mixed anaerobic consortia

The effect of anodic biofilm growth and extent of its coverage on the anodic surface of a single chambered mediatorless microbial fuel cell (MFC) was evaluated for bioelectricity generation using designed synthetic wastewater (DSW) and chemical wastewater (CW) as substrates and anaerobic mixed consortia as biocatalyst. Three MFCs (plain graphite electrodes, air cathode, Nafion membrane) were operated separately with variable biofilm coverage [control; anode surface coverage (ASC), 0%], partially developed biofilm [PDB; ASC ∼44%; 90 days] and fully developed biofilm [FDB; ASC ∼96%; 180 days] under acidophilic conditions (pH 6) at room temperature. The study depicted the effectiveness of anodic biofilm formation in enhancing the extracellular electron transfer in the absence of mediators. Higher specific power production [29 mW/kg COD R (CW and DSW)], specific energy yield [100.46 J/kg VSS (CW)], specific power yield [0.245 W/kg VSS (DSW); 0.282 W/kg VSS (CW)] and substrate removal efficiency of 66.07% (substrate degradation rate, 0.903 kg COD/m 3-day) along with effective functioning fuel cell at relatively higher resistance [4.5 kΩ (DSW); 14.9 kΩ (CW)] correspond to sustainable power [0.008 mW (DSW); 0.021 mW (CW)] and effective electron discharge (at higher resistance) and recovery (Coulomb efficiency; 27.03%) were observed especially with FDB operation. Cyclic voltammetry analysis documented six-fold increment in energy output from control (1.812 mJ) to PDB (10.666 mJ) operations and about eight-fold increment in energy from PDB to FDB (86.856 mJ). Biofilm configured MFC was shown to have the potential to selectively support the growth of electrogenic bacteria with robust characteristics, capable of generating higher power yields along with substrate degradation especially operated with characteristically complex wastewaters as substrates.

Bioelectricity generation from chemical wastewater treatment in mediatorless (anode) microbial fuel cell (MFC) using selectively enriched hydrogen producing mixed culture under acidophilic microenvironment

Bioelectricity generation from composite chemical wastewater treatment was evaluated in a dual chambered microbial fuel cell (MFC) [anode chamber (mediatorless; perforated plain graphite electrode); cathode chamber (50 mM potassium ferricyanide [K 3Fe(CN) 6] in phosphate buffer; pH 7.5; plain graphite electrode)] inoculated with selectively enriched hydrogen (H 2) producing mixed culture under acidophilic microenvironment (pH 5.5). Anode chamber, which resembles anaerobic suspended contact reactor was fed with wastewater and operated in absence of artificial mediator at acidic environment to proliferate H 2 producing bacteria. Experimental data showed the feasibility of producing bioelectricity from wastewater treatment, though power production was found to be dependent on the substrate loading rate. Maximum voltage of 271.5 mV (5.43 mA) and 304 mV (6.08 mA) was recorded at operating organic loading rates (OLR) of 1.165 kg COD/(m 3 day) and 1.404 kg COD/(m 3 day), respectively when measured at 50 Ω external resistors at stable operating conditions. COD removal efficiency of 35.4% (substrate degradation rate (SDR) of 0.412 kg COD/(m 3 day)) and 62.9% (SDR, 0.88 kg COD/(m 3 day)) was observed at OLRs 1.165 kg COD/(m 3 day) and 1.404 kg COD/(m 3 day), respectively. Maximum specific power production of 0.163 W/kg COD R (1.165 kg COD/(m 3 day); 50 Ω) and 0.198 W/kg COD R (1.404 kg COD/(m 3 day); 100 Ω) was observed during stable phase of fuel cell operation. Current density of 747.96 mA/m 2 (1.165 kg COD/(m 3 day)) and 862.85 mA/m 2 (1.404 kg COD/(m 3 day)) was documented at 10 Ω. Utilizing chemical wastewater for the production of renewable energy (bioelectricity) from anaerobic treatment is considered as a feasible, economical and sustainable process.

A comparison between the hat cycle and other gas-turbine based cycles: Efficiency, specific power and water consumption

The search for improved power cycles leads to various gas-turbine based cycles with very different characteristics and complexities, ranging from the traditional recuperated gas-turbine cycle to complexes' combinations of components such as intercooled compression, compressed air aftercooling, recuperation and/or reheat. In this work the HAT cycle (humid air turbine) is compared with the simple-cycle gas-turbine, the recuperated (and the intercooled-recuperated) gas-turbine cycles, the STIG (steam injection gas-turbines) and also with the combined-cycle. The focus of comparison is also put on the needed water quality and consumption, as well as on performance and emissions. The efficiency and/or specific power production advantages of each analyzed cycle are weighted against the cycle complexity, specific emissions and water needs. The different degrees of water purity for each use are also discussed and a differentiation is made between water circulation and water consumption. The possible best-range of applicability is addressed to each cycle, taking into account the power plant size and also the gas-turbine classical operating parameters as pressure ratio, turbine inlet temperature and operation profile.

Control and Power Supply Problems of Instrumented Satellites

Schemes for an attitude control system and for electric power supplies for an unmanned satellite of a few hundred pounds total weight are presented. The attitude of the satellite with respect to the earth's center is controlled within ±10 degrees by utilizing the shadowing effect of the earth on the isotropic cosmic radiation. A number of Geiger counters are arranged so that they sense the location of the shadow cone of the earth. Signals resulting from the counting rates of the counters control fly wheels that cause the satellite to rotate around its center of gravity. Three sources for electric power are described, each of which delivers an average of about 100 watts. The first converts the sun's radiating energy with a silicon junction photoelectric generator. A sun-seeking device keeps the generator oriented toward the sun during daytime. In the second system, the sun's radiation is directed toward a pile of thermocouples made of ZnSb and constantan. Thermocouples have been built of these materials which convert solar energy into electric energy with an efficiency of 5.6%. The third method uses a radioactive, isotope, strontium 90, and its daughter product, yttrium 90, as heating element for a pile of thermocouples. The half life of strontium 90 is 20 years. Each of these three sources has a specific power production of the order of 0.4 to 0.7 watts per pound of weight. The attitude control system and the methods of power supply described are applicable also to larger satellites.

Control and Power Supply Problems of Instrumented Satellites

Schemes for an attitude control system and for electric power supplies for an unmanned satellite of a few hundred pounds total weight are presented. The attitude of the satellite with respect to the earth's center is controlled within ±10 degrees by utilizing the shadowing effect of the earth on the isotropic cosmic radiation. A number of Geiger counters are arranged so that they sense the location of the shadow cone of the earth. Signals resulting from the counting rates of the counters control fly wheels that cause the satellite to rotate around its center of gravity. Three sources for electric power are described, each of which delivers an average of about 100 watts. The first converts the sun's radiating energy with a silicon junction photoelectric generator. A sun-seeking device keeps the generator oriented toward the sun during daytime. In the second system, the sun's radiation is directed toward a pile of thermocouples made of ZnSb and constantan. Thermocouples have been built of these materials which convert solar energy into electric energy with an efficiency of 5.6%. The third method uses a radioactive, isotope, strontium 90, and its daughter product, yttrium 90, as heating element for a pile of thermocouples. The half life of strontium 90 is 20 years. Each of these three sources has a specific power production of the order of 0.4 to 0.7 watts per pound of weight. The attitude control system and the methods of power supply described are applicable also to larger satellites.