Thermal Energy Conversion Research Articles

Subsurface waste heat recovery from the abandoned steam assisted gravity drainage (SAGD) operations

A considerable fraction of the energy injected during the thermal recovery of oil remains in the subsurface and wasted in the surrounding geological formations after the profitable life of oil wells is over. This work studied the concept of thermal energy extraction from the abandoned SAGD operations in oil sands reservoirs for generating electric power. The cold water is injected as a working fluid to extract heat after the oil production is ceased, and the produced hot water is fed to a surface binary cycle to generate electric power. The results show that an oil sands reservoir after SAGD operations could be regarded as an artificial geothermal system suitable for thermal energy extraction. It is demonstrated that a total net electric energy output of 57 GWh could be achieved based on a single SAGD well pair during a ten-year heat-extraction time, indicating the huge heat extraction potential at full field scale. The results show that the thermal energy conversion efficiency to electricity for the abandoned SAGD wells can reach as high as 12%. The demonstrated subsurface waste heat recovery from the abandoned SAGD sites revealed that between 15 and 36% reduction in CO2 emission could be achieved.

Thermochemical energy applications of green transition metal doped MIL–100(Fe)

Recently metal organic frameworks (MOFs), already known as adsorbent materials, have gained increasing research interest in thermal energy storage and conversion. MOF-water working pairs have been envisaged to provide the next revolutionary advancement in the existing sorption-based thermal energy storage and conversion systems. Herein, a promising MOF for high water sorption, MIL–100(Fe), and its transition metal-doped (Ni2+ and Co2+) derivatives are produced following a green synthesis procedure. The synthesized materials were tested in water sorption measurements using a thermogravimetric technique. The experimentally obtained adsorption data were correlated with the Sun-Chakraborty adsorption isotherm model. As an example of thermal energy conversion, an adsorption chiller is considered, and hence cooling cycles were drawn using the sorption data. The cooling cycles revealed that the nickel-doped MIL–100(Fe) demonstrates the highest value of the specific cooling effect (450.79 kJ kg−1) among the studied MOFs. Inverse gas chromatography technique was employed to investigate the surface free energy of the parent and doped MIL–100(Fe) MOFs. It was found that nickel-doped MIL–100(Fe) had the highest total surface free energy of 105.41 mJ m−2. Surfaces’ Lewis acid-base activities and the work of cohesion and adhesion (towards water molecules) were investigated. The surfaces’ properties were correlated with the water adsorption isotherms, which can provide crucial information for developing optimal adsorbents targeting water as the adsorbate for an efficient and effective thermal energy storage and conversion system.

Thermodynamic Optimization of Ammonia Decomposition Solar Heat Absorption System Based on Membrane Reactor.

In this paper, an ammonia decomposition membrane reactor is applied to a solar heat absorption system, and thermodynamic optimization is carried out according to the usage scenarios. First, a model of an ammonia decomposition solar heat absorption system based on the membrane reactor is established by using finite time thermodynamics (FTT) theory. Then, the three-objective optimization with and the four-objective optimization without the constraint of the given heat absorption rate are carried out by using the NSGA-II algorithm. Finally, the optimized performance objectives and the corresponding design parameters are obtained by using the TOPSIS decision method. Compared with the reference system, the TOPSIS optimal solution for the three-objective optimization can reduce the entropy generation rate by 4.8% and increase the thermal efficiency and energy conversion rate by 1.5% and 1.4%, respectively. The optimal solution for the four-objective optimization can reduce the heat absorption rate, entropy generation rate, and energy conversion rate by 15.5%, 14%, and 8.7%, respectively, and improve the thermal efficiency by 15.7%. The results of this paper are useful for the theoretical study and engineering application of ammonia solar heat absorption systems based on membrane reactors.

Solar Energy-Based Future Perspective for Organic Rankine Cycle Applications.

This article explores the patents of solar energy technologies in the organic Rankine cycle (ORC) applications. The conversion of low-quality thermal energy into electricity is one of the main characteristics of an ORC, making efficient and viable technologies available today. However, only a few and outdated articles that analyze patents that use solar energy technologies in ORC applications exist. This leads to a lack of updated information regarding the number of published patents, International Patent Classification (IPC) codes associated with them, technology life cycle status, and the most relevant patented developments. Thus, this article conducts a current investigation of patents published between January 2010 and May 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology and keywords. One thousand two hundred ninety-nine patents were obtained as part of the study and classified in F and Y groups of the IPC. The time-lapse analyzed was between January 2010 and May 2022. In 2014 and 2015, a peak of published patents was observed. China (CN) was the country that published the most significant number of patents worldwide. However, the European Patent Office (EP), the World Intellectual Property Organization (WO), and the United States (US) publish the patents with the highest number of patent citations. Furthermore, the possible trend regarding the development of patents for each technology is presented. A high-performance theoretical ORC plant based on the patent information analyzed by this article is introduced. Finally, exploration of IPC revealed 17 codes related to solar energy technologies in ORC applications not indexed in the main search.

Influences of usage intensity and weather on optimal building energy system design with multiple storage options

In non-residential buildings, many factors affect thermal and electrical loads. Some of these factors are not known during the planning process but are essential for a proper energy system design.Conducting a simulation- and optimization-based sensitivity analysis, this study investigates the effects of usage intensity and weather uncertainties on building energy system sizing. We developed a toolchain that comprehensively covers the stages, from determining user-related electricity demand to thermal demand calculation and energy conversion system design, up to deterministic design optimization of storage systems. By means of design of experiments, we systematically applied the toolchain to an all-electric non-residential building as a use case.We find that weather has the strongest correlation with optimal storage sizes and the size of energy conversion systems. They are also affected by the usage intensity of certain building zones. In addition, the storage sizes influence each other in the complex building energy system of our use case. Depending on the scenario and objective, annuities deviate 6%, annual emissions deviate up to 10% from the base scenario.We conclude that normative design methods do not suffice for optimal building energy system design and offer a viable method that can be incorporated into existing planning processes.

Identification of nonparametric thermodynamic model and optimization of ocean thermal energy conversion radial inflow turbine

Turbine is one of the key components of ocean thermal energy conversion system, and its aerodynamic performance and geometric structure directly affect the performance of the system. At present, the design methods of radial inflow turbines can be roughly divided into three categories: trial method, best velocity ratio method and screening method, which follow no concrete rules and are not comprehensive, and rely mostly on the designers' experience. This study proposes a fully data-based non-parametric model identification and optimization method for ocean thermal energy conversion radial inflow turbines is proposed, and takes the 25 kW R134 working fluid turbine of the ocean thermal energy conversion system as an example for verification and analysis. First, the optimal Latin hypercube sampling method was used to complete the experimental design with seven initial thermodynamic parameters as independent variables. And then according to the test data and the Gaussian process regression identification, the non-parametric turbine thermodynamic model was obtained. At last, on the basis of this model, the NSGA-III multi-objective optimization algorithm was used to optimize the design with the goal to achieve maximum efficiency and minimum diameter, and the optimized results were obtained. The results show that the non-parametric model based on the Gaussian process proposed in this study has higher accuracy, and the optimization results obtained based on this model are more efficient and have a more compact structure. The research work described in this study saves time and cost for completing the aerodynamic performance design of the turbine and further improving the expansion efficiency of the radial inflow turbine. It is of great significance for the practical application of promoting ocean thermal energy conversion.

Prospects and requirements for thermophotonic waste heat energy harvesting

Thermophotovoltaic (TPV) power generators offer great possibilities for thermal energy conversion when thermal sources with temperatures nearing or exceeding 1000 K are available. While the power density of conventional TPV systems is generally determined by Planck’s law in the far field, their fundamental performance is known to be dramatically affected by near field effects between the thermal emitter and the photovoltaic cell. Another potentially disruptive enhancement to the performance may be reached by transforming the thermal emitter to exploit electroluminescence. Taking advantage of an electroluminescent emitter as the source of radiation fundamentally alters the thermodynamics of the system. This allows boosting the achievable power densities by orders of magnitude, and also provides access to electroluminescent coolers, thermophotonic (TPX) heat pumps, and TPX power generation devices that can outperform both TPV and thermoelectric heat engines, especially at the low-grade waste heat (LGWH) temperature range (300–500 K) containing in total the majority of recoverable energy. In reality, functional TPX devices are yet to be demonstrated experimentally, due to several material and design bottlenecks. Here, we discuss the thermodynamics, ideal characteristics and advantages of TPX heat engines, and quantify how non-idealities such as non-radiative recombination, optical and resistive losses affect their performance. Our results suggest that, at LGWH temperatures, TPX heat engines start to outperform the best TPV systems when reaching quantum efficiencies of the order of 90%; beyond this threshold, TPX systems become increasingly efficient and powerful. • Showing the promise of thermophotonic (TPX) heat engines (HEs) for heat recovery. • Capturing TPX-HEs’ thermodynamics by developing and using a holistic model. • Quantifying the impact of non-radiative recombination, optical and resistive losses. • TPX-HEs outperform idealized thermophotovoltaic systems at low temperatures (<600 K). • Functional TPX-HEs are within reach with existing semiconductor technologies.

Bamboo derived SiC ceramics-phase change composites for efficient, rapid, and compact solar thermal energy storage

Integrated solar thermal conversion and latent heat storage based on phase change materials (PCMs) has emerged as a promising way for improving solar thermal utilization by avoiding redundant energy transport processes. However, the poor solar absorptance and low thermal conductivity of PCMs prohibit achieving high solar thermal energy storage efficiency. Here, bamboo-derived silicon carbide (BSiC) eco-ceramics based phase change composites are proposed to realize efficient, rapid, and compact solar thermal energy storage. BSiC/paraffin demonstrates a high thermal conductivity of 40 W m −1 K −1 at the porosity of 66%, where 96% pores are filled with paraffin and no prominent deterioration is observed after 2500 cycles. By further loading TiN nanoparticles on BSiC skeletons, an ultrahigh solar absorptance of 96.23% is obtained due to exciting broadband plasmonic resonances. Subsequently, the solar-thermal energy storage efficiency achieves as high as 91.1% at 1.62 W cm −2 . The high-performance solar thermal energy storage benefits from continuous thermal conductive channels and excellent solar absorptance of BSiC/PCMs composites. For high temperature applications, BSiC/LiOH–LiF composites are developed and possess high thermal conductivity of 35.0 W m −1 ·K −1 and large latent heat of 309 kJ kg −1 simultaneously, but corrosion problems need to be tackled before long-time utilization. This work paves the way for applying BSiC eco-ceramics in high-performance solar thermal energy conversion and storage. • Bamboo derived SiC-PCMs is proposed for high performance solar thermal energy storage. • BSiC-paraffin demonstrates a high thermal conductivity of 40 W m −1 K −1 at large porosity of 66%. • Solar absorptance of 96.23% and solar thermal energy storage efficiency of 91.1% are demonstrated. • BSiC/LiOH–LiF shows thermal conductivity of 35 W/m-K and energy density of 309 kJ kg −1 .

Semiconductor-dielectric-metal solar absorbers with high spectral selectivity

An ideal solar thermal absorber has a sharp transition between high and low absorptance at the wavelength where the blackbody emissive power begins to exceed the solar irradiance. However, most real selective absorbers have a fairly broad transition, leading to both solar absorption and thermal emission losses. Here, we model, fabricate, and characterize a highly selective semiconductor-dielectric-metal (Ga0.46In0.54As - MgF2 - Ag) solar absorber with an extremely sharp transition from high to low absorptance. The thin semiconductor serves as a selective filter, absorbing photons with wavelengths shorter than the bandgap and transmitting those with longer wavelengths. The highly reflective dielectric-metal rear mirror allows the structure to have very low emittance for longer wavelengths. These characteristics provide the absorber with a measured solar absorptance >91% below the bandgap wavelength and infrared emittance <5% at 100 C above the bandgap wavelength. This transition wavelength can be tuned by modifying the semiconductor composition, and modeling indicates that the absorber's optical properties should be stable at high temperatures, making the structure a good candidate for unconcentrated to highly concentrated solar thermal energy conversion.

Operation Control and Performance Analysis of an Ocean Thermal Energy Conversion System Based on the Organic Rankine Cycle

The development and utilization of marine renewable energy is an important measure for achieving energy conservation, emissions reduction and carbon neutrality. Ocean thermal energy is the most stable energy among all the types of marine renewable energy. This paper built a simulation model of an ocean thermal energy conversion system based on actual device specifications by Aspen and MATLAB and put forward a corresponding control strategy. The opening control signal of the control valve at the turbine inlet was the condenser inlet pressure in this paper, and the frequency control of the working fluid pump depended on the evaporating pressure and flow rate of the working fluid. This paper analyzed the key operating parameter changes of the system under different working conditions. According to the analysis results, the turbogenerator in this system was able to generate 50 kW power for about 8 months per year. The highest net output power of the Organic Rankine Cycle was 47.3 kW; the highest cycle thermal efficiency was 3.2%.

Economic Viability Analysis for an OTEC Power Plant at San Andrés Island

This paper presents the economic feasibility analysis of a 2 MW Ocean Thermal Energy Conversion (OTEC) power plant in the open cycle. The plant can supply 6.35% of the average annual consumption of the electricity demand located at San Andrés Island (Colombia). On the one hand, the work presents the selection of the place to locate an offshore facility considering the technical viability while, on the other hand, the economic viability analysis is performed. The latter considers two scenarios: one without desalinated water production and another one with desalinated water. In this way, it is intended to first determine its construction’s technical requirements to analyse its economic performance. This approach allows us to have a general idea of the implementation costs and the benefits obtained with this type of plant, for the particular case of San Andrés, an island in the Colombian Caribbean with sustained stress on electricity production and freshwater generation. The results obtained show that the technology is viable and that the investment can be recovered in an adequate time horizon.

The comparison of colloidal, optical, and solar collection characteristics between Fe2O3 and Fe3O4 nanofluids operated in an evacuated tubular volumetric absorption solar collector

BackgroundThe iron oxide nanoparticles as low-cost, eco-friendly, and efficient nanomaterials exhibit interesting optical properties which make them valuable for nanofluids-based volumetric absorption solar collectors. MethodsThe first aim of this study is to experimentally compare the colloidal stability and optical properties of Fe2O3 and Fe3O4 nanofluids in three volume fractions of 0.005, 0.01, and 0.02%. To the following, it is intended to examine the energy conversion efficiency of these nanofluids in an evacuated tubular volumetric absorption solar collector according to the ASHREA standard. Significant findingsBased on the results, the size and morphology of the iron oxide nanoparticles were nearly similar together, but when dispersed in water they exhibited different colloidal and optical properties. For example, the Fe2O3 nanofluids showed considerable spectral extinction coefficients in the visible range, while the Fe3O4 nanofluids presented limited extinction coefficients in the ultraviolet region with the lower values. At penetration depth of 4 cm, the 0.02%-Fe2O3 nanofluid resulted in a 100% solar weighted absorption fraction in comparison to 83.2% of the Fe3O4 nanofluid with the same volume fraction. According to the collector results, the Fe2O3 nanofluids displayed greater enhancement in the solar to thermal energy conversion than the Fe3O4 nanofluids. The maximum efficiency was 73% at 0.02%-Fe2O3 nanofluid and 51% at 0.02%-Fe3O4 nanofluid.

Biomass Homogeneity Reinforced Carbon Aerogels Derived Functional Phase‐Change Materials for Solar–Thermal Energy Conversion and Storage

We devised a functional form stable composite phase‐change materials (PCMs) to achieve a three‐dimensional (3D) interconnected porous carbon aerogel structure for encapsulating polyethylene glycol (PEG). A novel homogeneity reinforced carbon aerogel with a well‐interconnected porous structure was constructed by combining a flexible carbon resource from biomass guar gum with hard‐brittle carbon from polyimide, to overcome severe shrinkage and poor mechanical performance of traditional carbon aerogel. The supporting carbon aerogel‐encapsulated PEG produced the novel composite PCMs with good structure stability and comprehensive energy storage performance. The results showed that the composite PCMs displayed a well‐defined 3D interconnected structure, and their energy storage capacities were 171.5 and 169.5 J/g, which changed only slightly after 100 thermal cycles, and the composites could maintain the equilibrium temperature at 50.0−58.1 °C for about 760.3 s. The thermal conductivity of the composites could reach 0.62 W m−1 K−1, which effectively enhanced the thermal response rate. And the composite PCMs exhibited good leakage‐proof performance and excellent light–thermal conversion. The compressive strength of the composite PCMs can improve up to 1.602 MPa. Results indicate that this strategy can be efficiently used to develop novel composite PCMs with improved comprehensive thermal performance and high light–thermal conversion.

Control strategy of load following for ocean thermal energy conversion

Ocean thermal energy conversion (OTEC) provides a feasible solution for sustainable and stable power supply in remote islands. In this paper, a thermodynamic model of the OTEC system is developed to study the dynamic response of power output and superheating degree to manipulated variables. Afterward, a control strategy of load following for the island OTEC system is proposed. Finally, two controllers, MPC and PI, are designed and compared under fast and slow load changes as well as disturbance rejection test. The results indicate that the power output of OTEC system is sensitive to the speed of working-fluid pump, reaching the adjustment range of 14.7 kW when the nominal speed decreases by 30%. In addition, model predictive control (MPC) shows better performance in both rapid and slow load-change modes. Especially, in the rapid load-change mode, the MPC controller could always keep the evaporator outlet superheating in the range of 2–4.5 °C, while the PI controller may introduce no superheat that may cause liquid impact. Both MPC and PI controller can stabilize the power output at the set point under one day's measured disturbance, while MPC controller makes the superheating degree of evaporator outlet within smaller temperature fluctuations (<0.2 °C).

Thermal Stability and Thermodynamic Performances of Pure Siloxanes and Their Mixtures in Organic Rankine Cycles

Organic Rankine cycles are often the best solution for the conversion of thermal energy. The many working fluids include silicon oils. One crucial issue that determines the choice of a working fluid is its thermochemical stability, as this sets a limit to the maximum temperature at which the fluid can be used in a power plant. A second subject, much debated today, is the use of mixtures in ORCs. In the first part of this study, an investigation into the thermal stability of siloxanes using two different approaches was carried out. The results confirmed a limit working temperature for the considered siloxanes of about 300 °C, with a degradation that advanced significantly over time at 350 °C. In the second part of the study, an analysis of the thermodynamic performances of some siloxane mixtures was carried out. It was found that the efficiencies of the corresponding thermodynamic cycles were substantially the same as for the pure fluids used today. By changing the composition of the mixture, it was also possible to vary, within reasonable limits, the values of the condensation pressure, adapting the thermodynamic cycle to the different situations that can be encountered in current practice.

The effect of non-ionizing excitations on the diffusion of ion species and inter-track correlations in FLASH ultra-high dose rate radiotherapy

Purpose. We present a microscopic mechanism that accounts for the outward burst of ‘cold’ ion species (IS) in a high-energy particle track due to coupling with ‘hot’ non-ion species (NIS). IS refers to radiolysis products of ionized molecules, whereas NIS refers to non-ionized excitations of molecules in a medium. The interaction is mediated by a quantized field of acoustic phonons, a channel that allows conversion of thermal energy of NIS to kinetic energy of IS, a flow of heat from the outer to the inner core of the track structure. Methods. We perform step-by-step Monte Carlo (MC) simulations of ionizing radiation track structures in water to score the spatial coordinates and energy depositions that form IS and NIS at atto-second time scales. We subsequently calculate the resulting temperature profiles of the tracks with MC track structure simulations and verify the results analytically using the Rutherford scattering formulation. These temperature profiles are then used as boundary conditions in a series of multi-scale atomistic molecular dynamic (MD) simulations that describe the sudden expansion and enhanced diffusive broadening of tracks initiated by the non-equilibrium spectrum of high-energy IS. We derive a stochastic coarse-grained Langevin equation of motion for IS from first-principle MD to describe the irreversible femto-second flow of thermal energy pumping from NIS to IS, mediated by quantized fields of acoustic phonons. A pair-wise Lennard-Jones potential implemented in a classical MD is then employed to validate the results calculated from the Langevin equation. Results. We demonstrate the coexistence of ‘hot’ NIS with ‘cold’ IS in the radiation track structures right after their generation. NIS, concentrated within nano-scale volumes wrapping around IS, are the main source of intensive heat-waves and the outward burst of IS due to femto-second time scale IS-NIS coupling. By comparing the transport of IS coupled to NIS with identical configurations of non-interacting IS in thermal equilibrium at room temperature, we demonstrate that the energy gain of IS due to the surrounding hot nanoscopic volumes of NIS significantly increases their effective diffusion constants. Comparing the average track separation and the time scale calculated for a deposited dose of 10 Gy and a dose rate of 40 Gy s−1, typical values used in FLASH ultra high dose rate (UHDR) experiments, we find that the sudden expansion of tracks and ballistic transport proposed in this work strengthens the hypothesis of inter-track correlations recently introduced to interpret mitigation of the biological responses at the FLASH-UHDR (Abolfath et al 2020 Med. Phys. 47, 6551–6561). Conclusions. The much higher diffusion constants predicted in the present model suggest higher inter-track chemical reaction rates at FLASH-UHDR, as well as lower intra-track reaction rates. This study explains why research groups relying on the current Monte Carlo frameworks have reported negligible inter-track overlaps, simply because of underestimation of the diffusion constants. We recommend incorporation of the IS-NIS coupling and heat exchange in all MC codes to enable these tool-kits to appropriately model reaction-diffusion rates at FLASH-UHDR. Novelty. To introduce a hypothetical pathway of outward burst of radiolysis products driven by highly localized thermal spikes wrapping around them and to investigate the interplay of the non-equilibrium spatio-temporal distribution of the chemical activities of diffusive high-energy particle tracks on inter-track correlations at FLASH-UHDR.

Thermal Concentration on Thermoelectric Thin Film for Efficient Solar Energy Harvesting

Thermoelectric generators can directly harvest and convert ambient thermal energy into electricity, which makes it ideal for thermal energy conversion. However, the limited working temperature gradient developed by direct solar radiation severely restricts the performance and the application of solar thermoelectric generators. Here, we report a multilayer thin film integrating a solar selective absorbing coating and a thermoelectric layer, where an in-plane temperature gradient was established. The temperature gradient was relatively large since the absorbed solar energy could only flow through the restricted cross-section of the thin film, representing a high thermal concentration. The fabricated thin-film solar thermoelectric generators (100 mm × 15 mm) achieve an open-circuit voltage of about 300 mV, and an output power of 0.83 μW under AM 1.5G conditions. Our work opens up a promising new strategy to achieve the simple and cost-effective conversion of solar energy into electricity by thermal concentration.

High-Performance Thermionic Energy Converters Based on Cd3As2 Anode

The unusual electronic properties of 3-D topological Dirac semimetals have led to intensive research efforts focusing on their potential applications in high-performance electronic, photonic, and optoelectronic devices. In this work, we propose a conceptual design of thermionic energy converters (TECs) based on a Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> anode with significantly improved performance. Using the electronic properties of Cd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> —an air-stable topological Dirac semimetal—from first-principle density functional theory (DFT) calculation, such a device can achieve a maximum output power density and conversion efficiency of 10.96 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 57.29% at 1800 K, respectively. The advantages of topological Dirac anode over conventional metal- and graphene-based TECs are revealed. This work opens an exciting route toward high-performance energy converters via the union of topological material and thermionic devices.

Hybrid thermionic-photovoltaic converter with an In0.53Ga0.47As anode

Thermionic-photovoltaic (TIPV) converters exploit both electrons and photons emitted by a hot cathode to produce electric power. In this work, a TIPV converter structured with a tungsten cathode and an In 0.53 Ga 0.47 As photovoltaic (PV) anode (0.75 eV bandgap) is demonstrated to provide an increased output voltage with respect to the reference thermionic energy converter made of the same materials and operating under similar conditions. The higher voltage, measured to be from 0.3 to 0.5 V in the explored 1150–1450 °C temperature range, is explained by the additional contribution of the PV anode. Another work function engineered TIPV converter, obtained by coating the W cathode with LaB 6 and the In 0.53 Ga 0.47 As PV anode with BaF x , has led to an output power 2 orders of magnitude higher than the uncoated TIPV converter at 1200 °C cathode temperature. This opens the route towards future optimized TIPV electrodes. • Thermionic-photovoltaic (TIPV) devices with In 0.53 Ga 0.47 As anodes were assembled. • TIPV converter showed output voltages up to 0.5 V higher than the thermionic one. • A TIPV converter with low work function coatings (LaB 6 and BaF x ) was fabricated. • The coated TIPV energy converter provided an output power 100-fold than the uncoated one.

Production Process of Steam Power Plant and Calculation of Thermal Efficiency: Case Study of Teluk Sirih Steam Power Plant

The performance of a power plant can be known from the calculation of efficiency in the generating sector. Steam power plants utilize a series of energy conversion processes including: conversion of chemical energy into thermal energy when extracting heat from coal as fuel to heat boilers, conversion of thermal energy into mechanical energy in turbines and conversion of mechanical energy into electrical energy in generators. Like other steam power plants, the Teluk Sirih PLTU located in Bungus Teluk Kabung, West Sumatra has the same energy production process. it's just that the source of the water is taken from the sea so it requires special treatment to turn the water into water suitable for producing steam used in this power plant. The electricity production process will be explained in this study and an efficiency calculation process with a simple Rankine cycle is carried out to determine the efficiency of this power plant. From the calculation results, the thermal efficiency of PLTU Teluk Sirih is 29%. Based on the results of these calculations, it is known that the Telusk Sirih PLTU can be classified as a power plant with good efficiency.