Thermal Conversion Systems Research Articles

A Recyclable Energy Storage Wood Composite with Photothermal Conversion Properties for Regulating Building Temperature

AbstractAddressing the challenges of energy storage liquid leakage and long‐term stability in energy storage is crucial for achieving sustainable energy efficiency. In this study, polymethyl methacrylate (PMMA) is innovatively employed as an encapsulation film on the surface of the wood‐based phase change material, resulting in a recyclable wood‐based composite energy storage material (PPW). A novel energy storage liquid (PCMs) composed of lauric acid (LA), capric acid (CA), and polyethylene glycol (PEG) is immersed in the pretreated porous wood frame through vacuum impregnation. The PCMs imparted a phase change temperature of 21.0 °C, which is close to human comfort levels, and a high energy storage efficiency of 31.6 J g−1 to the PPW. Additionally, the PCMs provided the PPW with a photothermal conversion efficiency of 29.3%. Even after 200 freeze‐thaw cycles, the energy storage properties of the PPW remained nearly unchanged. Therefore, utilizing PMMA as an effective encapsulation material is a viable approach to prevent leakage of the phase change solution and enhance the recyclability of the PPW. Furthermore, the transparency of PMMA preserves the natural appearance of the wood, thereby broadening the application potential of PPW in residential buildings, thermal energy storage, and solar thermal conversion systems.

Effect of moisture content on pyrolysis product yield from lignite and lignite-peanut shell mixtures using slow pyrolysis

ABSTRACT The conversion of biomass-coal mixtures into energy using thermal conversion systems offers a more environmentally sustainable alternative to conventional coal consumption. A reactor with an internal compartment is proposed to improve the pyrolysis performance of lignite coal and mixtures of lignite coal with peanut shells. The study investigates lignite coal with varying moisture contents and peanut shell proportions (0%, 10%, 25%, and 50%) at a temperature of 500°C, using a heating rate of 0.1°C/s. The results indicated that dry mixtures demonstrated higher overall productivity compared to wet mixtures, particularly in terms of charcoal production. The weight of charcoal increased by 4.83%, 4.71%, 4.02%, and 2.61% across the mixtures. The total conversion rates for dry mixtures were 24.59%, 29.27%, 34.36%, and 40.44%, while for wet mixtures, the conversion rates were 29.42%, 33.98%, 38.38%, and 43.05%, respectively. The results revealed that moisture content during pyrolysis significantly influenced the productivity of lignite and lignite-peanut shell mixtures. The conversion rates in dry mixtures were lower compared to those in wet mixtures. The novelty of this work lies in its pioneering investigation of the impact of moisture on the slow pyrolysis of Turkish lignite mixed with peanut shells. It offers novel insights into optimizing the thermal conversion process for these materials by uniquely examining the effects of moisture on productivity and conversion rates.

Novel cellulose-based films with highly efficient photothermal performance for sustainable solar evaporation and solar-thermal power generation

Solar-driven interfacial evaporation has received substantial attention in a variety of applications, including water purification, seawater desalination, and energy production. However, creating a straightforward, adaptable, and scalable method for correctly integrating hybrid solar-thermal systems continues to be a challenging task. Herein, we propose an economical, scalable, and environmentally friendly approach for achieving synergistic coupling of interfacial solar energy conversion for evaporation and low-grade thermal energy conversion to electricity by incorporating zinc oxide (ZnO) nanoparticle-modified MXene (ZNM- MXene) into cellulose nanofiber (CNF) films. The vacuum filtering approach produces CNF@ZNM-MXene composite films with enhanced photothermal conversion efficiency, capillary hydrophilicity, and thermal localization. Because of its rapid water transport capability, excellent sunlight absorption, and efficient solar-thermal conversion under 1 kW m−2 irradiance, the CNF@ZNM-MXene solar evaporator's evaporation rate reaches 1.27 kg m−2 h−1, and the solar-vapor conversion efficiency is as high as 82.15%, outperforming most previously reported solar evaporators. Moreover, when compared to a standalone thermoelectric (TE) module, the output power of the solar thermal conversion system coupled with a CNF@ZNM-MXene composite films and a TE module is boosted by 15.32 times. This work offers a practical and effective method for simultaneously capturing solar energy and desalinating saltwater.

Thermal performance of a motile-microorganism within the two-phase nanofluid flow for the distinct non-Newtonian models on static and moving surfaces

Nanofluid plays a crucial role in addressing the heat transmission challenges facing the industries including chemical processing systems, automobile radiators, spacecraft design, concrete heating, solar thermal conversion systems, etc. Consequently, this research is devoted to analyzing the solar radiation mechanism, thermophoresis and Brownian motion under unique conditions, specifically, temperature gradient within liquids with limiting viscosities or plastic dynamic viscosity at zero and infinite shear rate. To increase the model novelty, a model involving two phases of Casson–Carreau fluid conveying tiny particles is developed to analyze the flow of solar radiation mechanism over stationary and moving surfaces. Furthermore, the impacts of heat generation, chemical reaction and activation energy are also taken into account. The dimensionless equations are solved through numerical methods using the Galerkin-weighted residual technique and analytically employing the Homotopy analysis method with the assistance of MATHMATIACA 11.3 software. Our study reveals that the fluid temperature reduces for greater values of Weissenberg number, and Casson parameter. Additionally, the distribution of gyrotactic microorganisms decreased against the bio-convective Schmidt number and Peclet number.

Feasibility study of coffee husk char-derived carbon dots to enhance solar photovoltaic-thermal applications

Coffee is one of the most traded commodities in the world. Coffee husk makes up the majority of the solid debris generated during the dry processing of coffee, which is between 30% and 50%. Pyrolysis is a reliable and feasible technology to valorise the coffee husk. The present study proposes and investigates a novel method for producing carbon dots from coffee husk char through pyrolysis. Nanomaterials are becoming more popular to improve the thermal and optical properties of working fluids used in solar photovoltaic and thermal conversion systems. The coffee husk-char derived carbon dot (CHC-CD) nanofluids are prepared with different char concentrations (1%, 2%, 3% and 4%). The chemical and optical properties of the nanofluid produced from coffee husk char (CHC-CD nanofluid) are investigated. The morphology, size and particle size distribution of the CHC-CD particles were studied using field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The particles were found to have an average size of 5.38 nm. The CHC-CD nanofluid had a basic pH and negative zeta potential, which was found to decrease with an increase in the char concentration and pH. The nanofluid prepared with 2% char was found to have a zeta potential of −61.4 mV. It was evident from the UV–vis transmittance spectra that the CHC-CD nanofluid prepared with a char concentration of 2% had very limited transmittance in the UV region and good transmittance above 735 nm. This transmittance range is found to be favourable for the smooth and efficient operation of silicon-based solar PV cells. The CHC-CD nanofluid also showed a maximum intensity emission wavelength of 522 nm at an excitation wavelength of 450 nm. Characterisation of the carbon phase, surface functional groups, and surface defects was also done using XRD, FTIR, and Raman spectroscopy, respectively. The optical and chemical properties indicate that the developed CHC-CD nanofluid can find application not only in solar photovoltaic and thermal systems but also in applications in biomedical and chemical sensor applications.

Progress and Prospects for Research and Technology Development of Supercritical CO2 Thermal Conversion Systems for Power, Energy Storage, and Waste Heat Recovery

CO2 is an environmentally friendly heat transfer fluid and has many advantages in thermal energy and power systems due to its peculiar thermal transport and physical properties. Supercritical CO2 (S-CO2) thermal energy conversion systems are promising for innovative technology in domestic and industrial applications including heat pump, air-conditioning, power generation, renewable energy systems, energy storage, thermal management, waste heat recovery and others. Both S-CO2 and transcritical CO2 thermodynamic cycles have been extensively investigated in order to improve the efficiencies of thermal and power systems and achieve net zero carbon emissions. This paper focuses on the progress and prospects for current research and technology development of S-CO2 thermal energy conversion systems and their applications including power generation, energy storage and waste heat recovery. First, the CO2 thermal transport and physical properties and benefits using CO2 as a heat transfer fluid in thermal energy and power systems are discussed. Then, classification of CO2 thermodynamic systems is presented. Next, S-CO2 for power generation, energy storage and waste heat recovery systems are presented. Finally, research needs of subcritical and supercritical CO2 heat transfer, fluid flow and heat exchangers for the development of various thermal energy and power systems are discussed.

Pyrolysis characteristics and gaseous products of bamboo shoot shells under N2 and CO2 atmospheres

To design industrial thermal conversion systems of bamboo shoot shells (BSS), pyrolysis characteristics of BSS under N2 and CO2 atmospheres were investigated using thermogravimetric analysis coupled with a Fourier-transform infrared. Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa methods were used to calculate kinetic parameters. Thermodynamics were evaluated based on Enthalpy, Gibbs free energy and entropy. Results showed that BSS pyrolysis under CO2 atmosphere had an obvious peak at the temperature range of 645–922 °C. CO2 decreased residual weight and average Eα of BSS pyrolysis, and improved the release of gaseous products. CO was the main gaseous product during pyrolysis process of BSS under CO2 atmosphere. The release of CO2 and CH4 reduced. BSS pyrolysis under N2 atmosphere and the first peak under CO2 atmosphere fitted with R2, R3, and A2 models when α increased from 0.1 to 0.5 and subsequently followed F2 model. Pyrolysis reaction of BSS was non-spontaneous and required an external heat supply.

Cellulose-based phase change membranes with reversible optical transmittance and lignin ester-enhancing photothermal conversion performance

Leakage issues and low photothermal conversion efficiencies have limited the application of organic solid–liquid phase-change materials. Herein, cellulose-based phase-change membranes (CPCM-FAS-LUEX) were prepared by physically blending three fatty alcohols (1-dodecanol, 1-tetradecanol, and 1-hexadecanol) with a cross-linked network composed of cellulose 10-undecenoyl ester (CUE), lignin 10-undecenoyl ester (LUE), and octadecyl acrylate (OA) with 2,2′-azobis(2-methylpropionitrile) as an initiator. In addition to being part of the network structure, LUE acted as a photothermal conversion enhancer. During phase change processes, the prepared membranes exhibited reversible optical transmittance, the response temperature of which could be adjusted (21–49 °C) by using different fatty alcohols. Differential scanning calorimetry revealed that the CPCM-FAS-LUEX membranes possessed good thermal energy storage capacities, with melting enthalpies up to 134.9 J/g. The introduction of LUE significantly improved the photothermal conversion performance, with an increase in efficiency from 42.06% to 88.66% at a light intensity of 230 mW/cm2. It is noteworthy that reversible optical transmittance and high photothermal conversion efficiency were achieved in the same materials. Hence, the synthesized CPCM-FAS-LUEX membranes have potential for use in thermal–response materials and solar–thermal storage and conversion systems.

Sustainable mechanism to popularise round the clock indoor solar cooking – Part II: workable solution

ABSTRACT Solar cooking is one of the significant applications of solar thermal conversion systems. In some of the developing countries of Asia and Africa, firewood was the only cooking option. Hence, outdoor solar cookers have gained popularity in such places due to household air pollution caused by the former. With the onset of urbanization, few developing countries have adopted kerosene, coal, and liquified petroleum gas in place of firewood, which in turn leads to the emission of harmful gases in the kitchen. On the other side, solar cooking has poor social acceptance in developed countries as it is an outdoor activity i.e. under the sun. Hence, a detailed review concerning the outdoor (in general) and indoor (in specific) solar cookers have been presented in part I of this paper: “Sustainable mechanism to popularize round-the-clock indoor solar cooking – Part I: Global status.” It reveals the importance of indoor solar cooking and the dearth of relevant experimental and numerical studies. Such a system is also essential to popularize solar cooking in developed countries (wherein electric cookers have already gained momentum). Hence, the present study proposes a passive indoor solar cooking system that can perform round-the-clock indoor cooking. The hypothesis of the proposed passive indoor solar cooking system, which is based on a coupled natural circulation system, is experimentally investigated with relevant assumptions. It yields the desired output and can perform efficiently without heat input, replicating off-sunshine hour cooking. Later, the experimental results are used to validate a numerical model (Ansys Fluent), which is further extended to replicate a practical system. Upon defining the appropriate boundary conditions, the numerical results depicted repetitive boiling (1 l of water for nine times) in the time range of 680–1500 s with heat load (daytime operation) and 700–1000 s without heat load (replicates off-sunshine hour cooking). Thus, the focused design is quite feasible, and with further recommendations being invoked, the evolution of a sustainable mechanism for round-the-clock indoor solar cooking is apparent.

Thermo-economic analysis and multi-objective optimization of supercritical Brayton cycles with CO2-based mixtures

• A thermo-economic analysis of Brayton cycle with CO 2 -based mixtures is performed. • The Pareto fronts of 3 working fluids are obtained by multi-objective optimization. • SCO 2 -Xe cycle shows the best thermodynamic performance compared to others. • CO 2 -Kr shows the potential for development through thermo-economic analysis. The Supercritical carbon dioxide recompression Brayton cycle (SCO 2 RBC) is regarded as one of the most promising thermal power conversion systems and mixing other gases with CO 2 to change the critical point represents an effective strategy to improve the performance of the Brayton cycle. In this work, the feasibility of using xenon and krypton as additives to the SCO 2 RBC is investigated via thermodynamic analysis. The effects of the key parameters on the thermo-economic performance of recompression Brayton cycles using CO 2 , CO 2 /xenon (mass fraction 0.55/0.45) and CO 2 /krypton (mass fraction 0.755/0.245) as working fluids are discussed by means of parametric analysis. A non-dominated sorting genetic algorithm is employed to simultaneously optimize the cycle exergy efficiency and the levelized cost of energy. The total thermal conductance, the main compressor outlet pressure, pressure ratio and split ratio are selected as the decision variables. The optimum solutions with their corresponding decision variables are selected from the Pareto frontiers. The results show that the supercritical CO 2 /krypton cycle has the huge development potential. Specifically, the optimum exergy efficiencies of Brayton cycles using CO 2 , CO 2 /xenon and CO 2 /krypton as working fluids are 0.585, 0.646 and 0.664. The addition of xenon can improve cycle efficiency up to 12.08 % higher than SCO 2 RBC while the levelized cost of energy also increased by 10.04%. The cycle efficiency of the supercritical CO 2 /krypton cycle is 9.44% higher while the cost is 2.49% higher compared to the SCO 2 RBC. There are suitable decision variables to make the cost of the cycle using CO 2 / krypton lower than that using CO 2 while achieving the same exergy efficiency when the required exergy efficiency is in the range of 0.60-0.62. The exergy destruction distribution of Brayton cycle illustrates that high temperature recuperator is the highest exergy destruction component and using CO 2 -based binary mixtures can reduce the total exergy destruction effectively.

An ultra-broadband and wide-angle absorber based on a TiN metamaterial for solar harvesting.

The efficient absorption of solar spectrum radiation is the most critical step in solar thermal utilization. In this work, a near-perfect metamaterial solar absorber with broadband, wide angle, polarization insensitivity, and high-temperature resistance is proposed and investigated. The absorber takes advantage of the high melting point material, which consists of a TiN reflector, a SiO2 insulating layer, and a TiN ring array. In the spectral range of 300-2500 nm, an average absorption of 97.6% is achieved. The percentage of absorbed energy in the AM1.5 spectral radiation can reach 95.8%. The electric and magnetic field distributions show that the high absorption is attributed to the coupling effect of surface plasmon resonance, guided mode resonance and cavity resonance. Furthermore, the absorber is found to maintain high absorption performance at large angles of solar radiation and to be insensitive to polarization. The designed absorber maintains its broadband absorption performance well within certain geometric tolerances. This reduces the complexity and cost of manufacturing and facilitates practical applications. The research indicates that this work will benefit the design and application of solar thermal conversion and thermophotovoltaic systems.

Cobalt-rich spinel oxide-based wide angular spectral selective absorber coatings for solar thermal conversion applications

Solar energy conversion technologies attain enormous attention to create more efficient energy production sources to meet the current world's demand. The solar thermal conversion system converts solar energy to heat, and the receiver tube is crucial for achieving high photo-thermal conversion efficiency. The absorber coatings with high solar absorptance at normal and wide incidence angles of solar radiation improve the performance of concentrated and non-concentrated solar thermal systems. To achieve high photo-thermal conversion efficiency in the solar thermal conversion system, a novel spinel structured cobalt-rich transition metal oxide-based absorber coating was developed by a cost-effective wet chemical route. The developed absorber coatings with sub-micron scaled surface protrusions with porous structure (size 0.75 μm) exhibit an excellent spectral selectivity (α/ε = 0.91/0.13). In addition, the coatings show an excellent wide angular solar absorptance of 0.97–0.96 at incidence angles of 10°–40°. Extensive characterization has been carried out to analyze the structural properties of the absorber coatings and correlated to the spectral selectivity and wide angular solar absorptance property. The stability of the absorber coating at 400 °C for 100 h in an open-air atmosphere assessed by the performance criteria (PC) function value of 0.015 indicates the ability of the optimized absorber coatings to employ in solar thermal systems.

A comprehensive review of recent progress of nanofluid in engineering application: Microchannel heat sink (MCHS)

Nanofluid is a new class of heat transfer fluid that is introduced to enhance the heat transfer performance in various heat exchanging systems. Prior to invention of nanofluid, water is the most common fluid used to extract heat generated from the systems. The application of water has reached thermal bottleneck since it can only enhance the heat transfer performance up to a certain extent. The suspension of nanoparticles with enhanced thermal conductivity provides augmentation in heat transfer performance. Since then, nanofluids have received great interest from scientists and researchers due to significant higher thermal conductivity. Due to enhanced thermophysical properties, nanofluids can be incorporated into high heat transfer device such as solar thermal conversion system, heat exchanger, and electronic equipment. Understanding the factors that influence the heat transfer performance is extremely important for appropriate selection and implementation of nanofluids. The influence of nanoparticles material, nanoparticles size, nanoparticles concentration, nanoparticles shape and surfactant are reviewed systematically to provide a comprehensive understanding of nanofluids. The review aims to extensively discuss the application of nanofluids in engineering application such as microchannel heat sink (MCHS). Finally, the review aims to update the readers about the current progress of nanofluids along with challenges of nanofluids in engineering field.

Thermo-hydraulic performance investigation of heat pipe used annular heat exchanger with densely longitudinal fins

To enhance the heat transfer capacity of the condenser end in the heat pipe heat exchanger, heat transfer and flow characteristics investigations of three densely longitudinal fin-equipped annular heat exchangers have been carried out by using a combined method of experimental testing and numerical simulation. One of the heat exchangers as a baseline is featured by the long straight fins. The other featured folded fins and arc-shaped fins, in which 40 rows of short fins were arranged just like the blade-lattice. The attained results showed that the short fold fins and arc-shaped fins had Nusselt numbers that were 27% and 35% higher than the long straight fins, and had friction factors that were 1088% and 2209% higher than the long straight fins. It indicates that the dense fin arrangement has a relatively limited influence on the wall temperature and overall heat transfer capacity. However, the friction loss is significantly sensitive to the fin arrangement because of the severe flow drag and flow separation induced by the blade-lattice like fins. The thermo-hydraulic performance evaluation suggests that the three densely longitudinal fins are suitable for different application scenarios with different heat transfer and pressure loss requirements. This work serves as a reference for the heat exchanger design in the heat pipe-based thermal power conversion system.

Experimental and numerical investigations of solar charging performances of 3D porous skeleton based latent heat storage devices

Volumetric-absorption-based solar charging via phase change processes is an emerging technology to harvest solar energy, however, how pore-scale radiation transport interacts with latent heat thermal energy storage processes is still vague. In this paper, volumetric-absorption-based solar charging processes at pore scale are investigated by experiments and numerical simulations based on Monte Carlo ray tracing coupled with the Finite Volume Method. The solar radiation transport, temperature distribution, liquid fraction, and solar thermal energy storage efficiency are systematically evaluated under different radiation intensities and skeleton thermal conductivities. Compared to the traditional surface-absorption-based mode, solar thermal energy storage efficiency of the volumetric-absorption mode is enhanced by 94% due to presence of multi-region heat sources. The solar thermal energy storage efficiency reaches a peak value of 54.09% at a radiation intensity of 10 kW·m−2. That is because low radiation intensities increase the melting time while too high intensities lead to large temperature nonuniformity, leading to high heat losses for both scenarios. Increasing the skeleton thermal conductivity can continuously improve the efficiency by reducing temperature nonuniformity, but further enhancement becomes marginal for thermal conductivity over 90 W·m−1·K−1. This work paves the way for the design and deployment of efficient integrated solar thermal conversion and latent heat storage systems.

Magnetically tightened form-stable phase change materials with modular assembly and geometric conformality features

Phase change materials have attracted significant attention due to their promising applications in many fields like solar energy and chip cooling. However, they suffer leakage during the phase transition process and have relatively low thermal conductivity. Here, through introducing hard magnetic particles, we synthesize a kind of magnetically tightened form-stable phase change materials. They achieve multifunctions such as leakage-proof, dynamic assembly, and morphological reconfiguration, presenting superior high thermal (increasing of 1400–1600%) and electrical (>104 S/m) conductivity, and prominent compressive strength, respectively. Furthermore, free-standing temperature control and high-performance thermal and electric conversion systems based on these materials are developed. This work suggests an efficient way toward exploiting a smart phase change material for thermal management of electronics and low-grade waste heat utilization.

Plastic-containing food waste conversion to biomethane, syngas, and biochar via anaerobic digestion and gasification: Focusing on reactor performance, microbial community analysis, and energy balance assessment

To manage the mixture of food waste and plastic waste, a hybrid biological and thermal system was investigated for converting plastic-containing food waste (PCFW) into renewable energy, focusing on performance evaluation, microbial community analysis, and energy balance assessment. The results showed that anaerobic digestion (AD) of food waste, polyethylene (PE)-containing food waste, polystyrene (PS)-containing food waste, and polypropylene (PP)-containing food waste generated a methane yield of 520.8, 395.6, 504.2, and 479.8 mL CH4/gVS, respectively. CO2 gasification of all the plastic-containing digestate produced more syngas than pure digestate gasification. Syngas from PS-digestate reached the maximum yield of 20.78 mol/kg. During the digestate-derived-biochar-amended AD of PCFW, the methane yields in the biochars-amended digesters were 6–30% higher than those of the control digesters. Bioinformatic analysis of microbial communities confirmed the significant difference between control and biochar-amended digesters in terms of bacterial and methanogenic compositions. The enhanced methane yields in biochars-amended digesters could be partially ascribed to the selective enrichment of genus Methanosarcina, leading to an improved equilibrium between hydrogenotrophic and acetoclastic methanogenesis pathways. Moreover, energy balance assessment demonstrated that the hybrid biological and thermal conversion system can be a promising technical option for the treatment of PCFW and recovery of renewable biofuels (i.e., biogas and syngas) and bioresource (i.e., biochar) on an industrial scale.

Micro and Macro Thermal Degradation Behavior of Cotton Waste

Fulfillment of energy demand and simultaneously to find proper solution of MSW from economical, social and environmental point of view waste-to-energy is the best option; also, the energy crisis is the new challenge in the front of world to push the economy in the progressive direction and simultaneous global warming and efficient use of energy are also challenging tasks. The thermal degradation of cotton was studied at temperature values () of 5,7,10,15,20 0C/min in a nitrogen atmosphere utilizing the TG/DTG 32 horizontally differential systemic balance method, which occurs in three stages. The three separate independent parallel mechanism’s defining the degradation was considered to derive the kinetic parameters. In first and second stage there might be degradation is with 10-15 % of total weight and 60-70 % of total weight respectively and finally 4-9 % residue remains in case of all heating rate. The elemental analysis of residue shows the existence of different elements in the residue on basis of which possible pollutants and cleaning requirement of thermal conversion system can be decided. The current TGA data was compared to sample decomposition using a Batch Type Pyrolyser (BTP) with a sample weight of 60 gm and a heating rate of 10 0C/min in a nitrogen atmosphere. The information obtained will aid in the modelling, designing, and operations of MSW thermal conversion methods.

Physical and thermo-chemical characterization of agricultural residues and municipal waste

Characteristics of crop residues such as size, angle of repose, colour and density, calorific value, percentage of moisture content and chemical composition affect the production of bio-fuels. These properties also affect drying and handling of biomass and the design of thermal conversion systems. These characteristics can vary noticeably from waste to waste. In this study, four local varieties of rice straw (Nabina, Tamapasara, Swarnaand NuaAchharmati), sugarcane bagasse, coconut coir and vegetable waste were characterized. Study revealed that the sugarcane bagasse has the darker color, higher particle density (384.66 kg.m-3) compared to others tested biomass. Sugarcane bagasse contained highest percentage 82.7% of volatile matter followed by coconut coir, vegetable waste and rice straw. Rice straw variety Nabina has shown the highest calorific value 22.98 MJ/kg compared to Tamapasara, Swarna and NuaAchharmati and can be utilized for biofuel production.

Spent coffee ground characterization, pelletization test and emissions assessment in the combustion process

Industrial development and increased energy requirements have led to high consumption of fossil fuels. Thus, environmental pollution has become a profound problem. Every year, a large amount of agro-industrial, municipal and forest residues are treated as waste, but they can be recovered and used to produce thermal and electrical energy through biological or thermochemical conversion processes. Among the main types of agro-industrial waste, soluble coffee residues represent a significant quantity all over the world. Silver skin and spent coffee grounds (SCG) are the main residues of the coffee industry. The many organic compounds contained in coffee residues suggest that their recovery and use could be very beneficial. Indeed, thanks to their composition, they can be used in the production of biodiesel, as a source of sugar, as a precursor for the creation of active carbon or as a sorbent for the removal of metals. After a careful evaluation of the possible uses of coffee grounds, the aim of this research was to show a broad characterization of coffee waste for energy purposes through physical and chemical analyses that highlight the most significant quality indexes, the interactions between them and the quantification of their importance. Results identify important tools for the qualification and quantification of the effects of coffee waste properties on energy production processes. They show that (SCG) are an excellent raw material as biomass, with excellent values in terms of calorific value and low ash content, allowing the production of 98% coffee pellets that are highly suitable for use in thermal conversion systems. Combustion tests were also carried out in an 80kWth boiler and the resulting emissions without any type of abatement filter were characterized.