Higher Heating Value Research Articles

Review of organic and inorganic waste-based phase change composites in latent thermal energy storage: Thermal properties and applications

Systematization and analysis of standalone waste materials that can serve as phase change materials (PCMs), and composites consisting of commercially available PCMs combined with organic and inorganic waste materials is presented. Within the conducted review research, obtained thermal properties of so far investigated waste-derived PCMs were presented, assessing, among other, their latent heat storage capacity, thermal conductivity, and thermal and cyclic stability. Refined coconut oil and Allanblackia oil exhibited exceptional thermal and cyclic stability along with high values of latent heat, amounting 105 kJ kg−1 and 81 kJ kg−1, respectively. In some cases incorporation of waste materials significantly improved thermal properties, e.g. the addition of carbonized waste tire rubber to dodecyl alcohol increased its thermal conductivity to 0.431 W m−1K−1, representing an increase by a factor of 2.3. This enhancement led to a 17.2 % reduction in heating times and a 20 % reduction in cooling times compared to using pure PCM. Besides providing extensive data on thermophysical properties of phase change composites, the study provides a comprehensive overview of their applications, economic feasibility, and environmental implications. This extensive review shows the potential of waste-derived PCMs to contribute to a circular economy by repurposing waste materials for sustainable energy solutions and reducing environmental impacts. The findings indicate that while valorising wastes or by-products as latent thermal energy storage materials is feasible, more research efforts are required towards potential commercialization.

Silica-based aerogels encapsulate organic/inorganic composite phase change materials for building thermal management

Phase change energy storage materials are widely used in thermal management because they reduce energy consumption and effectively address issues such as energy supply and demand mismatches. However, challenges such as leakage in solid-liquid phase change materials (PCMs), flammability in organic solid-liquid PCMs, and supercooling and phase separation in inorganic solid-liquid PCMs still need to be resolved for their practical applications. In this study, we used methyl palmitate, dodecahydrate disodium hydrogen phosphate, and decahydrate sodium carbonate as the main PCMs, sodium carboxymethyl cellulose as an emulsifier and thickener, and silica aerogel as the encapsulating material to successfully prepare a novel shape-stabilized organic/inorganic composite PCM (CPCM). The prepared CPCM exhibits excellent shape stability and flame retardancy without supercooling or phase separation issues. In addition, the prepared CPCM has a high latent heat value (174.1 J/g) and a suitable phase transition temperature (22.9 °C), and its thermal performance remains basically unchanged after 100 heating/cooling cycles. Furthermore, this CPCM also demonstrates exceptional performance in building thermal management. This study provides a new solution to the problems of flammability, supercooling, phase separation and easy leakage of CPCM currently used in the field of building thermal management.

From sewage sludge and lignocellulose to hydrochar by co-hydrothermal carbonization: Mechanism and combustion characteristics

This investigation focuses on fabrication of hydrothermal carbon (HTC) using the co-hydrothermal carbonization (Co-HTC) method from the raw materials of sewage sludge (SS) and lignocellulose. The as-prepared hydrochar (HC) was characterized and analyzed by using ultimate analysis, proximate analysis, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and Fourier transform infrared spectroscopy (FTIR) to investigate its fuel properties, surface morphology, and molecular structure. Particularly, the HC obtained from the Co-HTC process with pine sawdust as raw material exhibited several advantages in terms of carbon content (40.40 %), fixed carbon (FC) content (41.82 %), and high heating value (HHV, 14.87 MJ/kg). Synergistic effects were achieved from the components in the Co-HTC system, leading to increased carbon content, retention of organics, energy yield, HHV, and HC yield. Notably, the Co-HTC treatment of pine sawdust and SS demonstrated the most notable synergistic effect. Thermogravimetric analysis and combustion characteristic index (CCI) values showed that softwood lignin, represented by pine sawdust, exhibited better performance during combustion, with a CCI value of 21.78 (10−7 min−2 °C−3). In short, Co-HTC of hydrochar from lignocellulose and SS can represent a promising approach to resource utilization for obtaining solid fuel.

Sewage sludge pyrolysis ‘kills two birds with one stone’: Biochar synergies with persulfate for pollutants removal and energy recovery

The disposal and resource utilization of sewage sludge (SS) have always been significant challenges for environmental protection. This study employed straightforward pyrolysis to prepare iron-containing sludge biochar (SBC) used as a catalyst and to recover bio-oil used as fuel energy. The results indicated that SBC-700 could effectively activate persulfate (PS) to remove 97.2% of 2,4-dichlorophenol (2,4-DCP) within 60 min. Benefiting from the appropriate iron content, oxygen-containing functional groups and defective structures provide abundant active sites. Meanwhile, SBC-700 exhibits good stability and reusability in cyclic tests and can be easily recovered by magnetic separation. The role of non-radicals is emphasized in the SBC-700/PS system, and in particular, single linear oxygen (1O2) is proposed to be the dominant reactive oxygen. The bio-oil, a byproduct of pyrolysis, exhibits a higher heating value (HHV) of about 30 MJ/kg, with H/C and O/C ratios comparable to those of biodiesel. The energy recovery rate of the SS pyrolysis system was calculated at 80.5% with a lower input cost. In conclusion, this investigation offers a low-energy consumption and sustainable strategy for the resource utilization of SS while simultaneously degrading contaminants.

Molten salt biomass torrefaction – A sensitivity analysis of process conditions

Biomass is an abundant renewable resource that can be upgraded via torrefaction. Molten salts catalyze the torrefaction reaction, creating enhanced products for fuel and soil amendment purposes at lower temperatures than inert gas torrefaction. The objective of this study is to elucidate the main effects of molten salt torrefaction process conditions on ponderosa pine (Pinus ponderosa) and cave in rock switchgrass (Panicum virgatum) in a binary salt blend of lithium nitrate and potassium nitrate using a Plackett-Burman screening analysis. The investigated process conditions include sweep gas, temperature, salt to biomass ratio (S-B ratio), residence time, and lithium content. The metrics used to evaluate torrefaction severity include mass yields, chemical composition (lignin, cellulose, hemicellulose, extractives), higher heating value (HHV), carbon and nitrogen content, pH, and water sorption. The results show that switchgrass is more severely torrefied through molten salt torrefaction than pine at the same process conditions. For example, switchgrass mass yields are on average 23.3 % lower than pine mass yields across the test conditions. For both feedstocks, the most impactful process conditions are temperature, time, and lithium content in that order with some exceptions. For instance, the effect of temperature, time and lithium content on HHV are, respectively, 3.4×, 2.3×, and 1.7× larger than the next largest process condition for pine, whereas for switchgrass, these values are 3.6×, 2.7×, and 1×. Particle size, sweep gas, and S-B ratio have minor effects depending on the metric, but are overall not significant compared to temperature. The data suggests that an inert gaseous environment need not be maintained to facilitate molten salt torrefaction. Additionally, molten salt torrefaction can produce torrefied biomass with slightly different characteristics than inert gas torrefaction.

Hydrogen production from aqueous‐phase reforming of glycerol, sorbitol, and glycine over Pt/Al2O3 catalyst in a fixed‐bed reactor

AbstractAqueous‐phase reforming (APR) is an interesting technique for generating hydrogen (H2) from biofeeds. In this work, APR of model compounds of wet biomass for H2 production was investigated. Glycerol, sorbitol, and glycine were the chosen model compounds. They represent polyols and amino acids in wet biomass such as waste sludge and microalgal biomass. The Pt/Al2O3 catalyst was preferred and it was characterized using nitrogen adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x‐ray diffraction (XRD), and x‐ray photoelectron spectroscopy (XPS) techniques. APR trials were performed in a continuous fixed‐bed reactor. The reaction conditions chosen for this work were: temperature (T) 453–498 K, pressure (P) 1.2–2.4 MPa, feed concentration 5–15 wt%, and weight hourly space velocity (WHSV) 0.15–0.6 g reactant/(g catalyst h). The best conditions for H2 production by the APR process were found to be T = 498 K, P = 2.4 MPa, and feed concentration = 15 wt%. Among the chosen model compounds, glycerol exhibited the highest H2 selectivity (82.7%) and H2 yield (21.6%) at 498 K. The analysis of kinetic data suggested first‐order reaction kinetics for all the model compounds. The values of activation energy for the reactions with glycerol (55.4 kJ/mol), sorbitol (51.6 kJ/mol), and glycine (45.7 kJ/mol) were determined. Thus, APR is a promising route for effectively producing H2‐bearing gaseous products with high heating value from wet biomass.

Development of a System Suitable for an Apartment Complex for the Collective Recovery of Solid Resources from Food Waste: A Study on South Korea

The installation of food waste disposers has been prohibited in South Korea, due to conflicts with governmental policies that are focused on resource recovery from food waste and concerns about potential damage to the city’s sewer system. However, there is a growing demand for such systems in the country. This study proposes a system for the collective recovery of solid resources from food waste tailored for apartment complexes in South Korea, using an innovative solid–liquid separation technology. In the pilot experiment, 49.60% of the solids fed into the system were recovered as solid matter, confirming its practical applicability. Ultimately, a solid resource collective recovery system suitable for the high-rise apartment residence style of South Korea was developed and applied to an actual apartment complex. The final-stage solids were discharged from the system and processed through bio-drying, subsequently exhibiting a combustible material content of 67.06%, higher heating value (HHV) of 4843 kcal/kg, and lower heating value (LHV) of 3759 kcal/kg; moreover, they have the potential to be repurposed as biomass–solid refuse fuel (bio-SFR), compost, feed, and substrate for biogas production. The proposed food waste disposal system not only aligns with governmental policies, but also facilitates the recovery of high-quality resources from food waste, while providing a sustainable waste management solution.

Alternative green application areas for olive pomace catalytic pyrolysis biochar obtained via marble sludge catalyst

Evaluating industrial wastes in the system with minimum preprocessing and generation economically valuable products from them have critical importance. In this regard, especially cheap, wieldy, and readily available catalysts have been researched to increase variety of useful products in pyrolysis systems, to reduce process time, and to increase quality and diversity of products. Therefore, in this study, marble sludge (named K1) was evaluated as catalyst at different dosages (10%, 20%, 30%, 50%) and pyrolysis temperatures (300, 500, 700 °C) in olive pomace (OP) pyrolysis and; the potential green applications of produced new biochars at new usage areas with different purposes based on characteristics were investigated. ANOVA test results showed that temperature and catalysts ratio had significant effect on pyrolysis product yields since significance value for K1 and temperature was lower than 0.05 for pyrolysis products. OP-K1 biochars had alkaline properties and high earth metal quantities. Moreover, increment in K1 ratio and temperature resulted in decrement of the biochar surface acidity. Therefore, it can be indicated that these biochars can have a potential usage for anaerobic digestion processes, lithium-ion batteries, and direct carbon solid oxide fuel cell (DC-SOFC) but further electrochemical property test should be performed. Moreover, produced biochars can be alternative fuels in some processes instead of coal since they have low S content and high heat values. Consequently, it is foreseen that produced biochars will have an important place in the development of potential usage areas with a new and environmentally friendly approach in different areas apart from the conventional uses of catalytic pyrolysis chars.Graphical abstract

Transforming olive-processed waste and almond shells into high-quality Biofuels: a comprehensive development and evaluation approach

ABSTRACT Amidst the energy crisis, biomass energy has emerged as a pivotal solution, given its abundant distribution, impressive storage capabilities, and carbon-neutral nature. The study aims to develop biofuels of good quality using various agroalimentary waste products, Examining the pelletization process of including wet olive pomace (wet olive pomace (2 phases)(OP)), de-oiled olive pomace (DOP), olive stones (OS), and almond shells (AS), this research assesses its effectiveness in enhancing both bulk and energy densities, highlighting it as the optimal method for such enhancement. The preparation of these biofuels without binder has yielded promising results in terms of bulk density, hardness, calorific value, and ash content. Tests comparing biofuels to commercial olive pomace pellets (COP) showed the following: Using biomass with moisture content below 15%, granulometry of 1 mm or smaller, and no binder produces high-quality pellets. These pellets had high density (889, 675, 643, and 621 kg/m3), high hardness (99.18%, 99.80%, 98.92%, and 99.14%), and high heating values (18.93, 20.29, 22.51, and 20.38 MJ/kg) at average temperatures and pressures. These results are comparable to those of commercial products. In general, biomass and solid biofuels offer credible alternatives to produce energy in the form of electricity, heat, or both, using various processes, such as combustion, pyrolysis, and gasification. The knowledge gained from this research is very helpful in developing and improving bioenergy systems and promoting sustainable methods of producing energy from agricultural wastes.

Biochar and syngas from wet torrefaction of oil palm empty fruit bunches and palm oil mill effluent: A renewable energy approach

Abstract Palm oil mill effluent (POME) and oil palm empty fruit bunches (EFB) constitute the highest waste generated in the mill. This study investigates thermochemical approaches, specifically wet torrefaction and gasification, aiming to transform these wastes into higher-value products such as biochar. Wet torrefaction was initially applied to EFB and POME at 200 °C, with a heating rate of 5 °C/min for 30-min residence time under nitrogen-inert conditions, resulting in a solid yield of 82%. This process led to a notable increase in the heating value of raw EFB by 30.6%, from 17.3 to 22.6 MJ/kg. Subsequently, the product underwent gasification at various temperatures ranging from 600 to 800 °C, with a constant heating rate of 10 °C/min, gas flow rate of 20 ml/min, and a retention time of 30 min. The gasification reaction improved the solid yield and resulted in the generation of liquid products and syngas. The results indicated that 45-59% of biochar, 12-17% of bio-oil, and 30-39% of syngas were produced. The syngas composition, determined using gas chromatography, revealed the presence of CO2, H2, CH4, and CO. The solid product, characterised by a higher heating value, is a viable alternative for solid fuel. The findings suggested that both wet torrefaction and the gasification process have the potential to address the abundance of palm mill waste issues and offer an alternative approach for utilising and generating energy within the mill.

Hydrochar production through co-hydrothermal carbonization of water hyacinth and plastic waste

Abstract The global expansion of the economy and concerns about greenhouse gas emissions and climate change necessitate the exploration of sustainable alternatives to fossil fuels. Water hyacinth (WH) is globally recognized as one of the most problematic aquatic weeds, posing significant challenges to urban management by clogging waterways, polluting water sources, and causing harm to ecosystems. However, water hyacinth is enriched with hemicellulose, cellulose, and lignin, making it a noteworthy and superior biomass resource. Hence, this study focuses on the hydrothermal carbonization of water hyacinth into a renewable fuel source, the hydrochar. Hydrothermal treatment was implemented in this work as it can treat wet biomass, in this case, the water hyacinth, without the need of energy-extensive drying process. Plastic waste (PW), or more specifically low-density polyethylene (LDPE), was added as the co-feedstock during the HTC process with the purpose to boost the higher heating value (HHV) of the end product. The co-hydrothermal carbonization (co-HTC) process of the mixture of WH and PW at various ratios and temperatures were conducted to investigate the optimal HTC condition for high hydrochar yields. As the result, the highest hydrochar yield of 29.23 wt% was obtained with 12.5% LDPE substitution percentage, at 200 °C after a holding time of 90 min. However, in term of energy recovery efficiency (ER), the highest efficiency (27.28%) was achieved with 12.5% LDPE substitution percentage at 260 °C. The HHV value of the hydrochar produced in this work is in the range of 17.71-24.69 MJ/kg. In summary, the co-HTC of WH and LDPE could definitely be a promising alternative to bridge the gap from solid waste to renewable fuels.

Evaluation of pyrolysis characteristics and kinetic parameters from several prospected biomass residues by thermogravimetric analysis

Abstract With fossil fuel supplies dwindling and persistent environmental concerns surrounding their consumption, biomass has emerged as a highly promising renewable energy source. Understanding the characteristics of biomass pyrolysis is crucial as it provides valuable insights and guidance for designing and optimizing the pyrolysis process. In this regard, a thermogravimetric assessment was conducted to evaluate the pyrolysis characteristics and kinetic parameters of four prospective biomass sources: Yang Na wood (Dipterocarpus alatus), palmyra palm shell, cotton stalk, and spent coffee grounds with a condition temperature range of 33 °C to 700 °C and a heating rate of 10 °C·min-1 in a nitrogen atmosphere. The kinetic parameters were evaluated using the Coats and Redfern methods, employing various reaction order models. The activation energy and pre-exponential factor were determined for the active pyrolysis stage. The results revealed that the high heating values for all samples ranged from 18.20 to 23.00 MJ·kg-1. Additionally, the onset temperature fell within the range of 243 to 254 °C, while the offset temperature ranged from 365 to 452 °C for all samples. The conversion rate at the offset temperature was 0.67 for Yang Na wood, 0.62 for palmyra palm shell, 0.65 for cotton stalk, and 0.74 for spent coffee grounds. Moreover, the activation energies were measured as 46.47 kJ·mol-1 for Yang Na wood, 52.46 kJ·mol-1 for palmyra palm shell, 64.20 kJ·mol-1 for cotton stalk, and 69.01 kJ·mol-1 for spent coffee grounds. The higher activation energy corresponded to a higher pre-exponential factor. In conclusion, the pyrolysis characteristics and kinetic parameters of the four types of biomasses have been found to be favourable, indicating their potential for promotion and application as a raw material for the pyrolysis process.

Catalytic Microwave Pyrolysis of Albizia Branches Using Iraqi Bentonite Clays

Catalytic microwave-assisted pyrolysis of biomass is gaining popularity as an alternative to fossil fuels due to health, environmental, climate, and economic issues. This study conducted a catalytic pyrolysis process of the Albizia plant's branches using an Iraqi clay catalyst (bentonite) focusing on the variables including the biomass-particle size, experimental time, microwave power level, and the catalyst-to-biomass ratio. The physical and chemical properties of the resulting biofuel were analyzed presented by HHV, acidity, density, viscosity, GC-MS, FTIR for bio-oil and SEM, EDX, BET, HHV, FTIR for biochar. The study revealed that addition of bentonite as a catalyst led to enhanced production of biogas produced from 5% to 45% and decreased the power level used from 700 W to 450 W. Also, it raised the production of bio-oil generated with less power level and duration time. The addition of catalyst also affected the characteristics of bio-oil produced such as reducing the acidity by increasing its pH from 5 to 5.7, lowering the viscosity from 4.8 to 3.3 cSt, and the density from 1045 to 1039.2 kg/m3. Adding catalyst increased the percentage of aromatic and alcoholic substances in the bio-oil which led to improve the calorific value from 19.5 to 23 MJ/kg. Additionally, the biochar properties also improved, where the surface area and pore volume increased from 0.5512 to 40.384 m2/g and 0.00011 to 0.0361cm3/g respectively. The higher heating value was raised from 23.5 to 25 MJ/kg also. CH4 is also increased from 3.6 to 8.6% which is one of the essential fuel gasses.

Comparative studies of machine learning models for predicting higher heating values of biomass

This study addresses the challenge of efficiently determining the higher heating value (HHV) of biomass, a crucial parameter in large-scale biomass-based energy systems. The conventional method of measuring HHV using an oxygen bomb calorimeter is time-consuming, expensive, and less accessible to researchers, particularly in developing nations. To overcome these limitations, we employed four machine learning (ML) models, namely Random Forest (RF), Decision Tree (DT), Support Vector Machine (SVM), and Extreme Gradient Boosting (XGBoost). These models were developed by using proximate and ultimate analysis parameters as input features. Up to 200 datasets were compiled from literature and used for the ML models. Our results demonstrate the effectiveness of all ML models in accurately predicting the HHV of biomass materials. Notably, the XGBoost model exhibited superior performance with the highest R-squared (R2) values for both training (0.9683) and test datasets (0.7309), along with the lowest root mean squared error (RSME) of 0.3558. Key influential input features identified for HHV prediction include carbon (C), volatile matter (Vm), ash, and hydrogen (H). Consequently, this research provides a reliable alternative for predicting HHV without the need for costly and time-intensive experimental measurements, facilitating broader accessibility in biomass energy research.

Flame-retardant and phase-changing microcapsules incorporating black phosphorus for efficient solar energy storage

A novel phase change microcapsule has been developed and synthesized for solar energy storage systems. The fabrication process involved the in-situ polymerization of phase change microcapsules, wherein cellulose nanocrystals (CNCs) were employed as Pickering emulsifiers and nano-fillers to enhance the properties of the melamine formaldehyde resin (MF) shells. These enhancements included improved emulsifying ability, mechanical strength, and sustainability. Subsequently, black phosphorus (BP), a two-dimensional material with high solar absorption intensity and a wide frequency range, was covalently modified by MF to enhance the photothermal capacity of the microcapsules and reduce the thermal resistance between the photothermal material and the phase change material (PCM), this functionalized BP was referred to as MF@BP. The phase change microcapsules without and with MF@BP exhibit high latent heat values of 210.79 J g−1 and 207.92 J g−1, respectively. Furthermore, the PCM core content was measured at 88.9% and 88.5%, and the encapsulation rates are 99.0% and 98.8%, respectively. The PCM microcapsules with MF@BP demonstrated excellent photothermal characteristics with an efficiency of 92.04%. Additionally, the PCM microcapsules exhibit stability below 200 °C and retain 99.4% of their latent heat even after 100 cycles of heating and cooling. Furthermore, the PCM microcapsules display self-extinguishing properties due to the flame retardancy of the MF shell, and the incorporation of black phosphorus further enhanced the flame retardancy. Overall, these PCM microcapsules exhibit significant potential for utilization in solar energy systems.

Selective production of high-value fuel via catalytic upgrading of bio-oil over nitrogen-doped carbon-alumina hybrid supported cobalt catalysts

Bio-oil derived from biomass fast pyrolysis can be upgraded to gasoline and diesel alternatives by catalytic hydrodeoxygenation (HDO). Here, the novel nitrogen-doped carbon–alumina hybrid supported cobalt (Co/NCAn, n = 1, 2.5, 5) catalyst is established by a coagulation bath technique. The optimized Co/NCA2.5 catalyst presented 100 % conversion of guaiacol, high selectivity to cyclohexane (93.6 %), and extremely high deoxygenation degree (97.3 %), respectively. Therein, the formation of cyclohexanol was facilitated by stronger binding energy and greater charge transfer between Co and NC which was unraveled by density functional theory calculations. In addition, the appropriate amount of Lewis acid sites enhanced the cleavage of the C–O bond in cyclohexanol, finally resulting in a remarkable selectivity for cyclohexane. Finally, the Co/NCA2.5 catalyst also exhibited excellent selectivity (93.1 %) for high heating value hydrocarbon fuel in crude bio-oil HDO. This work provides a theoretical basis on N dopants collaborating alumina hybrid catalysts for efficient HDO reaction.

Evaluation of Growth and Energy Parameters of One-Year-Old Raspberry Shoots, Depending on the Variety

The article examines the influence of six varieties of primocane raspberries, Rubus idaeus L., on the growth parameters and energy properties of the biomass. The unique aim of this study was to show the impact of primocane raspberry varieties, grown for a single harvest, on the growth parameters of the bushes and the energy and emission characteristics of the biomass obtained from the pruned canes. To the best of our knowledge, there is no such analysis connected to varieties of raspberries available in the literature. The following primocane raspberries were assessed: Polana, Polesie, Delniwa, Poemat, Polonez, and Poranek. Among the studied raspberry varieties, Polana was characterized by the highest number of side shoots and the greatest sum of the shoot lengths, while the Polonez variety was characterized by the highest average shoot length and shoot thickness. In the tested raspberry varieties, the weight of the shoots per hectare varied significantly, ranging from 6.06 t in the Poranek variety to 9.05 t in the Delniwa variety. It was shown that the raspberry variety had a significant impact on the higher heating value (HHV) and the lower heating value (LHV). The lowest energy value was found in the Delniwa (HHV—17.32 MJ·kg−1; LHV—16.07 MJ·kg−1) and Polana (HHV—17.33 MJ·kg−1, LHV—16.19 MJ·kg−1) varieties, and the significantly highest value was observed in the Poranek variety (HHV—17.63 MJ·kg−1, LHV—16.39 MJ·kg−1). The assessment of the total volume of exhaust gases showed the highest value of this parameter for the Polesie and Delniwa varieties (6.89 m3·kg−1), with the lowest for the Polana variety (6.69 m3·kg−1).

Grid-neutral hydrogen mobility: Dynamic modelling and techno-economic assessment of a renewable-powered hydrogen plant

The seasonally varying potential to produce electricity from renewable sources such as wind, PV and hydropower is a challenge for the continuous supply of hydrogen for transport and mobility. Seasonal storage of energy allows to avoid the use of grid electricity when it is scarce; storage systems can thus increase the resilience of the energy system. For grid-neutral and renewable hydrogen production, an electrolyser is considered together with a Power-to-Gas seasonal storage system, which consists of a methanation, the gas grid as intermediate storage and a steam reformer. As feed stream, electricity from an own photovoltaic (PV) system is considered, and for some cases additional electricity from the grid or from a wind turbine. The dynamic operation of the plant during a year is simulated. It is possible to safely supply fuel cell vehicles with hydrogen from the grid-neutral plant without using electricity when it is scarce and expensive. To supply 135 kgH2/day, unit sizes of 1 MW–2.9 MW for the PV system and 0.9 MW–2.6 MW for the electrolysis are required depending on the amount of available grid-electricity. The usage of grid-electricity increases the capacity factor of the electrolysis, which results in decreased unit sizes and in a better economic performance. Seasonal storage of energy is required, which results in an increased hydrogen production in summer of approximately 50% more than directly needed by the fuel cell vehicles. The overall efficiency from electricity to hydrogen is decreased due to the storage path by 10%-points to 56% based on the higher heating value. Assuming a cost-equivalent hydrogen price per driven kilometre in comparison to the actual diesel price and electricity costs of 10 Ct/kWhel from the grid, the revenues of the system are higher than the operating costs.

Experimental and modeling study of medical waste based on plasma gasification

Plasma gasification melting (PGM) provides reliable disposal of toxic medical waste with a low heating value, which is capable of converting waste into energy. This study investigates the performance of experiments on plasma gasification for the treatment of chemical-pharmaceutical medical waste (CPMW) with an air medium. A comparative analysis is performed for gasification characteristics at three reactor temperatures (1000, 1400, and 1800 °C). Moreover, a thermodynamic equilibrium model is developed to assess performance features such as syngas yield, high heating value, and cold gas efficiency in the gasification temperature range of 1000–1800 °C. A comparison of the experiment and computational outcomes shows a good agreement. The results show that the quality of syngas and heating value is improved by increasing the temperature of the plasma gasifier so that at 1800 °C, H2, CO, and higher heating value (HHV) are obtained as 41 %, 37 %, and 10 MJ/Nm3, respectively. The obtained syngas is a clean fuel with low sulfur-containing and nitrogen-containing. The experimental results provide an extensive comprehension of CPMW gasification in a plasma reactor and consider a possibility for hydrogen and energy production.

Comprehensive study on social, compositional and thermal aspects of household solid waste for waste-to-energy potential estimation in Tashkent city

The management of household solid waste (HSW) has emerged as a key issue in developing nations. A critical analysis of the physical and chemical components of MSW management and infrastructure is necessary to address current socioeconomic issues. According to the World Bank projections, the annual global generation of solid waste from municipalities is expected to reach 2.59 billion tons by 2030 and and 3.40 billion tonnes by 2050. Inadequate handling of waste products frequently results in harm to the environment, the spread of diseases, and the generation of greenhouse gases, all of which have contributed to climate change and global warming. The waste-to-energy (WtE) strategy, which drastically reduces waste volume and produces renewable energy, has been adopted by a number of countries to address these issues. In this study, the social, compositional, and thermal aspects of household solid waste in a typical Tashkent District were studied. A Social survey was conducted to investigate residents’ behavior towards waste sorting. The survey was conducted in the Uchtepa district of Tashkent, Uzbekistan. The composition of household solid waste was studied to explore the fractional distribution of the waste in the area. The American Society for Testing and Materials (5231–92) and European PN-EN standards were used for sampling, sorting, and for the rest of the analyses. Subsequently, proximate and ultimate analyses were performed to better understand combustion properties. A high heating value was identified to estimate the energy generation potential of household solid waste. Social survey results showed that the waste generated in the apartments will be discarded either on the day of its generation or the maximum after three days. Overall, 52 % of the respondents chose to sort their waste, compared to 48 % who had no real desire to separate their household solid waste. Food waste, plastics, and paper constituted 70 % of the total waste generated in the district. The mixed waste sample had a high heating value of 23.87 Mj/kg. The analysis revealed an energetic potential of HSW generated from the landfill as thermal energy.