Power Production Efficiency Research Articles

Exergetic Analysis of Hybrid Photovoltaic - Thermal Solar Collectors Coupled to Organic Rankine Cycles

In this work, the application of hybrid solar modules that combine photovoltaic panels and solar thermal collectors coupled with a low-temperature thermal cycle such as the Organic Rankine Cycle is discussed, their main purpose being an increase in the total electric power production per available area. This work will study the thermal and electrical power production efficiency of the hybrid system, the increase in the PV module electric conversion efficiency due to their cooling through heat transfer to the thermal cycle and the total exergetic efficiency of the system. A simplified simulation of the system in steady state conditions based on a thermal efficiency model will be performed with the aid of the EES (Engineering Equation Solver) software using climate data from Campinas, São Paulo, Brazil. The study shows that while the PV/T+ORC system does fulfill the purpose of increasing the electrical power generation both from the generator coupled to the thermal cycle and from the increase in the PV module efficiency due to its cooling. Thus, there is an increase the overall exergy efficiency of the system compared to uncoupled PV/T collectors.

Energy Efficiency Analysis of Multi-Type Floating Bodies for a Novel Heaving Point Absorber with Application to Low-Power Unmanned Ocean Device

Long-term energy supplies hinder the application of the low-power unmanned ocean devices to the deep sea. Ocean wave energy is a renewable resource with amount stores of enormous and high density. The wave energy converter (WEC) could be miniaturized so that it can be integrated into the devices to make up the power module. In this paper, a small novel heaving point absorber of energy supply for low-power unmanned ocean devices is developed based on the counter-rotating self-adaptive mechanism. The floating body as an important part of the heaving point absorber, the geometric parameters is optimized to increase the efficiency of power production. Through constructing the constitutive relation between the geometric parameters, the wave force, the motion displacement, the motion velocity, and the capture width ratio of the floating body, the energy efficiency characteristics of the multi-type floating bodies are calculated, and the optimal shape is selected. On the other hand, in the calculation process of the wave force, the Froude-Krylov method is an effective method to accurately calculate the wave excitation force. Meanwhile, nonlinear static and dynamic Froude-Krylov force effectively overcomes the inaccuracy of the linear models and reduces the time consumed to simulate. Finally, the wave force, heaving velocity, heaving displacement, and capture width ratio of the three floating bodies are compared and analyzed, and the results show that the cylindrical floater that is vertically placed on the wave surface is more suitable for the novel heaving wave energy point absorber.

Dynamic simulation, control, and performance evaluation of a synergistic solar and natural gas hybrid power plant

Solar power is considered among the leading renewable energy technologies. Abundant supply, flexibility of installation, and decreasing cost makes it an interesting renewable energy resource. However, there are challenges associated with the reliability of solar power due to its intermittent nature. This work demonstrates the synergies that exist in integrated hybrid systems, where a dispatchable fuel is used in conjunction with concentrated solar power. In this simulation-based study, a parabolic trough solar concentrator is used to collect solar energy. The heat collected from the solar field is used to generate steam in a Rankine cycle. The system also utilizes natural gas combustion in the steam generator to provide supplemental steam when the solar intensity is reduced due to cloud cover or at night. Natural gas is also used for superheating the steam, which allows the system to produce higher temperatures and achieve increased thermodynamic cycle efficiencies. This flexible design produces 100 MW at nominal conditions, while it is capable of producing a maximum of 140 MW when sufficient solar energy is available. The novel contributions of this work include a complete, systems-level, dynamic model of a hybrid solar plant. The model is complete with a control system that smoothly transitions the plant from pure natural gas mode at night to solar hybrid mode during the day. It evaluates innovative design features such as flexible fuel operation, steam superheating to boost efficiency, and preheating by solar or waste heat. Furthermore, this work demonstrates that by hybridizing a solar system with a dispatchable energy source, both the reliability and efficiency of the solar power production are increased. The annual solar-to-electric efficiency increases from 15.2% to 26.13% with hybridization, which indicates that utilization of the solar energy is effectively increased.

Employing photovoltaic/thermal panels as a solar chimney roof: 3E analyses and multi-objective optimization

In this study, photovoltaic/thermal (PVT) panels are employed as a roof of the solar chimney power plants (SCPP), to enhance the power generation and exergy efficiency. A parametric study is conducted to scrutinize the influence of the effective parameters on the performance and energy/exergy/exergoeconomic (3E) indicators of the SCPP, PVT and SCPP/PVT system using EES software. Eventually, the proposed system is optimized by multi-objective optimization (MOO) based on a genetic algorithm to determine the optimum solution points from 3E standpoints and also the well-balanced solution point. Results of the parametric study reveal that the SCPP/PVT system operates more efficiently at lower PVT cell temperature. Results of the MOO demonstrate that at the well-balanced operating point, total exergy efficiency and cost rate of the SCPP/PVT were obtained as 3.304% and 241.6 $/h, respectively. Eventually, scatter distribution of the effective parameters indicates that the height of the tower should be around 300 m. The proposed renewable-based energy system is a promising and applicable method to considerably enhance the power production and exergy efficiency of the SCPPs.

Detailed parametric investigation of dry gasification oxy-combustion power cycle using ASPEN Plus simulations

Dry gasification oxy-combustion (DGOC) power cycle is a novel, zero-emission power production scheme. This work presents the detailed parametric study of various process performance variables namely gasifier temperature, gasifier pressure, fraction of recycle gas from combustor, molar gasification agents ratio, different type of sorbents on the process performance measured in term of product gas quality and quantity, total heat generated for power production and sulfur removal efficiency using the ASPEN Plus simulator. Various sorbents namely CaCO3, Fe2O3, MnO, CuO are considered for this study. Results shows that different sorbents posses different behavior. Temperature has significant affect on the DGOC performance. Fe2O3 is not a suggested sorbent in DGOC. CuO appears to be good sorbent in terms of temperature in the gasifier required or energy input required to the gasifier, and sulfur removal efficiency. MnO appears to be good sorbent in terms of syngas quality and total heat generated which was used to produce power by DGOC cycle.

Performance enhancement of heat recovery from engine exhaust gas using corona wind

This study develops a new type of heat exchanger with tungsten wires to produce a corona wind. Experimental data are presented for the velocity and temperature of the corona flow from wires to parallel electrodes with respect to the applied voltage and power. Additionally, a gas engine power generation system is manufactured, and its power generation efficiency is tested according to the fuel gas volume fraction between methane and carbon dioxide. Furthermore, an exhaust gas heat recovery system is fabricated using the proposed heat exchanger. A prototype of the corona wind heat exchanger is manufactured, and its enhanced heat recovery efficiency is tested with the gas engine. The corona wind heat exchanger operates well under the available exhaust gas conditions; it increases the temperature of 1 L/min water flow by 45 °C by recovering 2 kW of heat energy from the exhaust gas. The total power production efficiency was increased from 29% to 47%. The results confirm that the proposed corona wind heat exchanger can be applied to the gas engines to greatly enhance their heat recovery efficiency.

Визначення ефективності вироблення електричної енергії атомними електростанціями за методологією повних енергетичних витрат. Частина 1. Витрати енергії на будівництво

Визначення ефективності вироблення електричної енергії атомними електростанціями за методологією повних енергетичних витрат. Частина 1. Витрати енергії на будівництво

Evaluation of alternative power production efficiency metrics for offshore wind turbines and farms

Abstract The use of power production efficiency metrics for wind turbines is important for evaluating their productivity and quantifying the effectiveness of actions that are meant to improve the energy production. The goal of this research is not to propose a new efficiency metric since there are already multiple efficiency metrics widely used in practice: availability, power generation ratio, and power coefficient. Our objective here is to sort out the question of how these efficiency metrics are related to, or different from, one another. We believe addressing this research question has a great degree of practical significance as it is a question practitioners are often puzzled with. Understanding the similarities and differences of multiple efficiency metrics may even lay a foundation for the future proposals of new efficiency metrics. Our evaluation of whether the existing metrics are consistent with each other is driven by the use of actual data from an offshore wind farm. We observe that the three metrics show some degree of consistency but the power generation ratio, albeit the least popular, appears more representative of all metrics and more illustrative of the underlying efficiency. We also found that there is about 4% efficiency difference between wake-free and in-the-wake turbines for this specific wind farm.

Mathematical modelling of operation modes and performance evaluation of an innovative small-scale concentrated solar organic Rankine cycle plant

In this paper an innovative small-scale concentrated solar 2 kWe organic Rankine cycle plant coupled with a phase change material storage tank equipped with reversible heat pipes is investigated using a simulation analysis. The plant, intended for residential applications, is going to be built and tested under the European funded H2020 Innova MicroSolar project executed by the consortium of several Universities and industrial organizations, led by Northumbria University. The authors of this work used the design of the integrated system, developed by the consortium, to preliminary estimate the overall performance of the system in order to provide useful information for its forthcoming real operation. In particular, according to the varying ambient conditions, the influence of different operation modes of the prototype plant are evaluated. The dynamic simulation analysis has shown an interesting performance of the system in terms of annual operating hours, power production and conversion efficiencies. More precisely, the organic Rankine cycle unit is able to operate for more than 3100 h/year, achieving the design performance when solar power is sufficiently high, producing about 5100 kWhe/year. For the considered operating set-point temperatures of the thermal energy storage, the plant is able to reach high conversion efficiency also when the organic Rankine cycle unit is supplied by discharging the energy stored in the storage tank, for about 800 h/year. Hence, the work has provided some useful insights into the best working conditions of such micro combined heat and power system to be integrated in residential buildings. Moreover, the analysis could serve as a general guide for the design and optimization of the mutual interactions of the different subsystems in small-scale concentrated solar organic Rankine cycle plants.

Treatment of Mineral Oil Refinery Wastewater in Microbial Fuel Cells Using Ionic Liquid Based Separators

Microbial fuel cells (MFCs) are an environmentally friendly technology that can recover electricity directly from several wastes at ambient temperatures. This work explores the use of mineral oil refinery wastewater as feedstock in single-chamber air-cathode MFC devices. A polymer inclusion membrane based on the ionic liquid methyltrioctylammonium chloride, [MTOA+][Cl−], at a concentration of 70% w/w, was used as separator, showing a good efficiency in power production and chemical oxygen demand (COD) removal. The power and the chemical oxygen demand removal reached values of 45 mW/m3 and over 80%, respectively. The evolution of other parameters of the wastewater including nitrites, phosphates and sulphates were also studied. Kjeldahl nitrogen and sulphates were significantly reduced during MFC operation. The results show that mineral oil refinery wastewater can be used as feedstock in air breathing cathode-microbial fuel cells based on polymer ionic liquid inclusion membranes. This configuration could represent a good alternative for wastewater depuration while producing energy during the process.

Thermodynamic assessment of a novel SOFC based CCHP system in a wastewater treatment plant

Wastewater Treatment Plants (WWTP) have a significant role in both processing wastewaters to return to the water cycle and in transforming between 40% and 60% of the dissolved organic matter into a non-fossil combustible gas (biogas) with a methane content of around 50–70 vol %. Significant energy cost savings can be achieved using combined cooling, heat and power (CCHP) systems in small-scale distributed power system wastewater treatment plants. In this study, feasibility of a trigeneration system in a real wastewater treatment plant is studied. A mathematical model has been developed to evaluate system performance from the thermodynamics point of view. Based on the simulation results, fuel consumption, power production, and thermal efficiency of the system were analyzed. For the proposed configuration, the electricity coverage is increased by 27% and the produced cooling load of around 20 kW in summer season is obtained. The results also reveal that integration of the trilateral cycle (TLC) and the absorption chiller system in the reference WWTP offers a 17.2% more efficient plant from the viewpoint of first law efficiency.

Using the adsorption chillers for utilisation of waste heat from rotary kilns

Waste heat utilisation and its reclamation is important for increasing the efficiency of the electric power production and for decreased consumption of primary energy. Waste heat can be utilised for the electric power production or for manufacturing and processing purposes. According to long-term forecasts, the consumption of electric power with current consumption of about 150 TWh, can be increased to about 230 TWh in around 2040, what may lead to the increased energy consumption from fuels and the increased emission of harmful contaminants to the atmosphere. The cement subsector, next to the glass industry, is among the most power-consuming industries, and it consumes about 12-15% of total energy consumed by industry in total, whereas the CO2 emission from such industry exceeds about 5% in worldwide scale. In the cement sector, there is an increasing need for useful reclamation of waste energy, in order to obtain high energy-saving factors, and hence the financial and environmental benefits. In this paper the chances for waste energy reclamation from a rotary kiln are presented, with means of the used adsorption chillers.

Utilization of waste heat from separation process of Ulubelu’s geothermal power plant by implementing an Absorption Refrigeration System (ARS) to improve plant performance

Utilization of geothermal energy for water-dominated reservoir usually involves a separation process that turns geothermal fluid mixtures into pure steam and brine water. This process also occurred on Ulubelu’s geothermal power plant (GPP). As waste energy from the power generation process, the remaining heat energy in brine water is still high enough to run an absorption refrigeration system (ARS). This study proposed an integrated power generation and absorption system that operate side by side for a further cooling process. ARS will be employed to produce a lower temperature of cooling water from the GPP’s cooling tower and then pass it to GPP’s condenser. The lower temperature of cooling water will affect steam condensation process and the vacuum pressure of condenser, moreover, increase power production and exergy efficiency of Ulubelu’s GPP. The improvement of exergy efficiency & production capacity will be observed along with the rise of the investment cost as form as the annual cost of the ARS. A Multi-objective optimization using genetic algorithm will be conducted to minimize exergy efficiency and the annual cost of ARS. The optimization will be conducted using MATLAB along with EES for work fluid properties database. The temperature of generator, absorber, condenser, and evaporator of ARS are used as decision variables. Finally, the effect of integrated system and optimum value for each decision variables are presented in this study.

Hydrogen-oxygen steam generator applications for increasing the efficiency, maneuverability and reliability of power production

The comparative feasibility study of the energy storage technologies showed good applicability of hydrogen-oxygen steam generators (HOSG) based energy storage systems with large-scale hydrogen production. The developed scheme solutions for the use of HOSGs for thermal power (TPP) and nuclear power plants (NPP), and the feasibility analysis that have been carried out have shown that their use makes it possible to increase the maneuverability of steam turbines and provide backup power supply in the event of failure of the main steam generating equipment. The main design solutions for the integration of hydrogen-oxygen steam generators into the main power equipment of TPPs and NPPs, as well as their optimal operation modes, are considered.

High Electrical Power Densities from Salinity Gradients By Combining Electrode and Donnan Potentials in a Single Electrochemical Cell

Salinity gradients exist when two waters have different salt concentrations (e.g., when freshwater reaches seawater at coasts or when desalination brine is mixed with less saline water). Salinity gradients contain an immense amount of potential energy, which can theoretically provide 40% of the global electrical demand. One means to harvest salinity gradient energy is to use electrochemical techniques. In an electrochemical cell, a voltage can be created by using salinity gradients to alter electrode potentials in Capacitive Mixing or creating Donnan potentials across ion-exchange membranes in Reverse Electrodialysis. The main challenge with these techniques is that they yield power densities that are too low for commercialization (Capacitive Mixing: ~0.4 W/m2, Reverse Electrodialysis: ~3 W/m2). Here, we combined these two types of potentials in a single electrochemical cell, greatly increasing power densities to values that exceed 12 W/m2 when mixing synthetic freshwater and seawater. We examined how cell design and operating parameters as well as electrode and membrane materials influenced power production and energy efficiency. The results suggest that this type of cell may be used to effectively harvest salinity gradient energy at coasts and produce electricity from saline desalination brines.

One-step pyrolysis route to three dimensional nitrogen-doped porous carbon as anode materials for microbial fuel cells

The design and synthesis of low-cost and favourable anode materials is crucial to both power production efficiency and overall performance of microbial fuel cells (MFCs). Herein, we reported the preparation of three dimensional (3D) nitrogen-doped porous carbons (N/PCs) by one-step pyrolysis of solid mixture of sodium citrate and melamine. a variety of techniques, including electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), etc., were applied to characterize the surface physicochemical properties of the products, featuring macroporous structure with rich nitrogen doping on the as-prepared N/PCs. When applied as anode materials of MFC, the N/PCs exhibits a maximum power density of 2777.7mWm−2, approximately twice higher than that of the MFCs with the commercial carbon cloth (CC) as anode. The significantly improved performance of the N/PCs was attributed to the unique structure and properties, such as favourable porous structure, good electrical conductivity, and large pore volume (0.7cm3g−1) in the present N/PCs. Nitrogen dopant on the surface of porous carbon contributed to an increasing in biocompatibility, resulting in a suitable micro-environment for microbial growth and thus helps to decrease charge transfer resistance at the electrode interface.

Toward Interoperability of Smart Grids

Smart grid has emerged as the next generation of power grids for improved control and efficiency of power production, delivery, and consumption. Unlike the traditional power grid, a smart grid involves significant data communication across the grid. However, in the current practice, different areas of the power domain use different data semantic models, which has caused significant interoperability issues among systems and become a major barrier toward smart grids. Interoperability issues can also arise in communication. There has been growing interest in adopting publish-subscribe communication for improved quality of communication in smart grids. However, adopting publish-subscribe communication requires resolving potential interoperability issues with the client-server communication in the traditional power grid. In this article, we explore interoperability issues in smart grids and discuss how they can be addressed from the data and communication perspectives.

Achieving Negative Emissions with the Most Promising Business Case for Bio-CCS in Power and CHP Production

The urgency for significant reductions in global greenhouse gas (GHG) emissions highlights the importance of carbon sinks, i.e. solutions that can remove CO2 from the atmosphere, and the possibility for offsetting historical emissions. The later the global GHG emissions turn to decline, the greater is the need for sinks or so called “negative emissions”. Achieving negative CO2 emissions is possible by applying carbon capture in processes using biomass as feedstock (bio-CCS).Electricity production efficiency of chemical looping combustion (CLC) power plant is higher than in power plants based on solid fuel and other CO2 capture technologies. The higher efficiency of CLC in comparison to other CCS technologies emphasizes the cost benefit of bio-CLC in terms of both, merit order and overall economic feasibility. The advantage of combined heat and power production (CHP) over the sole power production has been recognised also in the case of CCS applications. By CHP, process efficiencies over 90% (on LHV basis) are possible and efficiency penalties of the CCS processes can be minimised as decreased efficiency in power production can be compensated by additional heat production.In this paper, the most feasible concept for bio-CCS in power and CHP production is presented based on improved efficiency, negative emissions and benefits of CHP within Nordic bioenergy context. Techno-economic analyses of industrial scale CLC power plant and CHP plant are presented in different market situations. Feasibility of CLC investment and the utilization of such plants are investigated and compared to oxy-fuel and air combustion references in a fictive energy system. In general, the smaller scale is often limiting biomass applications, CLC, CHP and utilisation of CO2. In the presented bio-CLC concept, all of these advantages are combined in a scale which is realistic for commercial application.

Electrical power production from low-grade waste heat using a thermally regenerative ethylenediamine battery

Thermally regenerative ammonia-based batteries (TRABs) have been developed to harvest low-grade waste heat as electricity. To improve the power production and anodic coulombic efficiency, the use of ethylenediamine as an alternative ligand to ammonia was explored here. The power density of the ethylenediamine-based battery (TRENB) was 85 ± 3 W m−2-electrode area with 2 M ethylenediamine, and 119 ± 4 W m−2 with 3 M ethylenediamine. This power density was 68% higher than that of TRAB. The energy density was 478 Wh m−3-anolyte, which was ∼50% higher than that produced by TRAB. The anodic coulombic efficiency of the TRENB was 77 ± 2%, which was more than twice that obtained using ammonia in a TRAB (35%). The higher anodic efficiency reduced the difference between the anode dissolution and cathode deposition rates, resulting in a process more suitable for closed loop operation. The thermal-electric efficiency based on ethylenediamine separation using waste heat was estimated to be 0.52%, which was lower than that of TRAB (0.86%), mainly due to the more complex separation process. However, this energy recovery could likely be improved through optimization of the ethylenediamine separation process.

Time‐dependent climate impact and energy efficiency of combined heat and power production from short‐rotation coppice willow using pyrolysis or direct combustion

AbstractA life cycle assessment of a Swedish short‐rotation coppice willow bioenergy system generating electricity and heat was performed to investigate how the energy efficiency and time‐dependent climate impact were affected when the feedstock was converted into bio‐oil and char before generating electricity and heat, compared with being combusted directly. The study also investigated how the climate impact was affected when part of the char was applied to soil as biochar to act as a carbon sequestration agent and potential soil improver. The energy efficiencies were calculated separately for electricity and heat as the energy ratios between the amount of energy service delivered by the system compared to the amount of external energy inputs used in each scenario after having allocated the primary energy related to the inputs between the two energy services. The energy in the feedstock was not included in the external energy inputs. Direct combustion had the highest energy efficiency. It had energy ratios of 10 and 36 for electricity and heat, respectively. The least energy‐efficient scenario was the pyrolysis scenario where biochar was applied to soils. It had energy ratios of 4 and 12 for electricity and heat, respectively. The results showed that pyrolysis with carbon sequestration might be an option to counteract the current trend in global warming. The pyrolysis system with soil application of the biochar removed the largest amount of from the atmosphere. However, compared with the direct combustion scenario, the climate change mitigation potential depended on the energy system to which the bioenergy system delivered its energy services. A system expansion showed that direct combustion had the highest climate change mitigation potential when coal or natural gas were used as external energy sources to compensate for the lower energy efficiency of the pyrolysis scenario.