Thermal Energy Requirements Research Articles

Onboard amino acid salt-based CO2 integrated absorption and mineralization: Kinetics, mechanism, economics and life cycle

The International Maritime Organization's ambitious greenhouse gas reduction strategy is driving efforts to capture carbon from marine engine exhaust gas. Onboard carbon capture and storage (OCCS) faced significant challenges, particularly due to the substantial thermal energy requirements during the capture process and the complexities of transporting captured CO2 to storage facilities. The integrated CO2 absorption and mineralization (IAM) process, a thermodynamically downhill process, offered a potential solution for rapidly absorbing and sequestering CO2 in-situ. In this study, a single-step amino acid salt-based IAM process was employed to address carbon emissions from ships. Under optimized conditions, over 85 % of the CO2 in simulated marine engine exhaust gas was captured and completely converted to calcium carbonate using a potassium glycinate/ calcium hydroxide blend absorption slurry. This approach tackled the key challenges of effectively capturing CO2 from ships, while minimizing energy consumption, and ensuring the safe storage of the captured CO2. A case study on a 1700 TEU container ship evaluated the economic benefits and global warming potential of the OCCS system, indicating that capturing CO2 from ships could be profitable (87.2 $/ton CO2) and calcium carbonate could be a commercial product. Despite high-carbon-intensity absorbents (such as calcium hydroxide) partially offset the carbon reduction effort, resulting in a decline of carbon capture efficiency from 85 % to 44 %. The proposed amino acid salt-based IAM method could be considered a promising technique for reducing carbon emissions from ships, providing a feasible technical means for achieving the International Maritime Organization's ambition strategy for zero-carbon shipping.

Integration of energy storage and determination of optimal solar system size for biomass fast-pyrolysis

This study presents a model and analysis of a heliostat field collector (HFC) system integration with fast-pyrolysis of biomass and determination of the optimal solar system size for this integrated system. Given the intermittent nature of solar energy, an auxiliary heater and a thermochemical energy storage system (TCES) are included. Four cases of HFC integration with the fast-pyrolysis process have been studied: 1) low solar radiation, 2) sufficient solar radiation, 3) high solar radiation, and 4) no solar radiation with available stored energy in TCES. The solar energy system was modeled and calculated using the Engineering Equation Solver (EES) software, while the fast-pyrolysis process and the TCES were simulated using the Aspen Plus software. A thermodynamic and economic analysis has been conducted to estimate the share of solar energy for different process configurations. Economic calculations have been conducted for three different heliostat filed areas: 4000, 8000, and 12000 m2. Solar fraction, investment and operational costs, as well as total cost were calculated for these three heliostat field areas. The results indicate that the optimum heliostat field area for the studied biomass pyrolysis plant is 8000 m2 and the average solar fraction of the required energy in summer is 0.39 and while it is 0.34 for the whole year. Simulation results considering this optimized heliostat filed area indicate that 6.27 t/h of bio-oil is produced from 10 t/h of hybrid poplar biomass. Implementing this solar-assisted system reduces CO2 emissions, increases efficiency of the system and lowers thermal energy requirement for the fast-pyrolysis process from 6MW to 3.99MW.

Entropy generated nonlinear mixed convective beyond constant characteristics nanomaterial wedge flow

Background and objectiveNanomaterial flows at present have received much attention of the researchers. Such motivation stems for their utilization in pharmaceutical, industrial, petroleum, manufacturing and engineering applications including regenerative medicine, treatment of cancer, electronic device cooling, solar collector, mineral oil, antimicrobial agents, thermal storage system, transformer cooling and X-imaging etc. Higher thermal energy requirement in several electrical and mechanical systems is desired in recent time due to high advancement of science and technology. For important application here the stagnation point flow due to wedge with nonlinear convection is explored. For porous media, the Darcy-Forchheimer relation is considered. Characteristics of nanofluid is added by utilizing Buongiorno's model. Variable fluid characteristics are under consideration. Applied magnetic field is accounted. Energy expression comprises thermal radiation, Brownian motion, Ohmic heating, thermophoresis and heat generation. First order reaction and entropy rate are considered. MethodologyNonlinear differential expressions are changed into dimensionless ordinary systems through adequate transformations. The resultant nonlinear ordinary systems are solved through optimal homotopy analysis technique (OHAM). ResultsOutcomes for influential variables about temperature, velocity, concentration and entropy rate have been arranged. Here results show that for magnetic field the liquid flow and entropy rate have opposite scenarios. Thermal distribution and concentration have reverse effects for random motion variable while similar effect holds for thermophoresis parameter. Magnetic field and diffusion parameters contribute to augment entropy generation. Higher values of temperature dependent electrical conductivity variable lead to increase entropy rate. Thermal distribution for radiation and Eckert number is similar.

Alternate solvent for soybean oil extraction based on extractability and membrane solvent recovery.

Ethyl acetate, acetone, 2-propanol, 1-propanol, and ethanol were screened among the class 3 category solvents as an alternative to hexane based on operational and occupational safety and bio-renewability potential. All five solvents exhibited higher extractability (22.3 to 23.2%) than hexane (21.5%) with soybean flour. Additionally, there was no significant difference in the fatty acid and triacylglycerol (TAG) composition of the oils extracted using alternate solvents and hexane, indicating the oil quality was not affected. More importantly, ethyl acetate (2.1%) resulted in a marginally higher yield of TAG, while 2-propanol showed a nearly equal yield to hexane. Further, membrane desolventizing was attempted to mitigate the limitations of higher thermal energy requirements. One of the polydimethylsiloxane membranes exhibited good selectivity (TAG rejection 85.8%) and acceptable flux (59.3 L·m-2·h-1) with an ethyl acetate miscella system. Under plant-simulated recirculation conditions, a two-stage membrane process reduced the oil content in permeate to 2.5%. The study revealed that ethyl acetate could potentially replace hexane, considering its higher TAG extractability and suitability for the membrane-augmented solvent recycling process in the extraction plants.

Electropulsing anisotropy of cold-rolled Grade 2 titanium sheet: Effect of electric current direction on recrystallization and hardness

This study investigated the effects of electropulsing treatment (EPT) condition on the microstructure and microhardness of cold-rolled Grade 2 Ti sheet. Particular attention was paid to the dependence of the material properties on the electric current direction, referred to as electropulsing anisotropy. Direct-current (DC) EPT was applied along either the rolling direction (RD) or transverse direction (TD) of the rolled sheet. EPT along the TD resulted in a higher heating rate and maximum temperature, whereas that along the RD accelerated the static recrystallization (SRX) process under identical electropulsing parameters. Such a discrepancy was interpreted using the elongated grain structure and basal texture in the cold-rolled Ti sheet. These results were further supported by microhardness measurements, confirming the presence of electropulsing anisotropy during DC EPT in Ti alloys for the first time. In addition, the employed EPT was compared to a traditional furnace heat treatment (FHT) with rigorous temperature and time control, wherein the optimum EPT process spent only 13% of the processing time to complete SRX with a lower thermal energy requirement. This indicates a significant athermal contribution of EPT to electropulsing anisotropy.

Green hydrogen, electricity, and heat multigeneration via using solar, wind and hybrid RE systems: Comprehensive case studies in Arabian Peninsula Countries

This paper aims to assess the impact of solar and wind renewable energy (RE) potentials on the performance and economics of different RE systems located in Saudi Arabia and the rest of the Arabian Peninsula Countries (APC) to meet hydrogen, electrical, and thermal energy requirements. Techno-economic studies were carried out to evaluate the performance of a solar Photovoltaics (PV), a wind turbine (WT), and a hybrid solar/wind (PV/WT) system. The performance of different configurations of the considered systems are simulated and optimized in hourly basis at various locations in the APC region using a developed MATLAB computer code. The findings showed that the hybrid PV/WT system is more effective than PV or WT systems. In Riyadh, for the hybrid PV/WT system, Net Present Cost (NPC), Cost of Electricity (COE) and Cost of Hydrogen (COH) are 97.792 K$, 0.137 $/kWh and 2.01 $/kg, respectively. However, for the PV system, the findings showed that NPC, COE and COH increased by 30, 27 and 32%, respectively. For a standalone WT system NPC, COE and COH values increased by 53, 52, and 54%, respectively. In Saudi Arabia, it is obsereved that the minimum costs of both electricity and hydrogen productions are achieved for the hybrid standalone PV/WT system in Neom City with values of COE = 0.128 $/kWh and COH = 1.881 $/kg. For the APC region, the most cost-effective hybrid standalone PV/WT system is found in Kuwait City with COE = 0.120 $/kWh and COH = 1.765 $/kg. Furthermore, COE and COH contours of PV, WT, and PV/WT systems economics are developed which give the decision makers a full vision about solar and wind potentials in the region and identify the locations that minimize the cost of production.

Heat and mass transfer analysis of desiccant-coated heat exchanger with desiccants and metal-organic framework for bus air conditioning applications

Desiccant-coated heat exchangers (DCHEs) in air conditioning offer advantages like independent temperature and humidity control, reduced energy consumption, and high performance. However, the availability of desiccants with high water adsorption and low thermal energy requirements is limited. The present study proposes that aluminum fumarate (Al-Fum) MOF-coated heat exchangers will outperform conventional desiccants, especially at low regeneration temperatures (around 50°C). In order to evaluate this hypothesis, the performance of DCHEs was evaluated with a validated analytical model for different solid desiccant coatings: silica gel, zeolite, and Al-Fum MOF. Water vapor sorption characteristics, heat and mass transfer, and adsorption and desorption capacities were determined. The results showed that the Al-Fum MOF-coated heat exchanger outperformed silica gel and zeolite at low regeneration temperatures under adiabatic conditions. The MOF exhibited superior water uptake capacity (0.39 g/g) between 20% and 80% RH compared to the other studied conventional desiccants. Moreover, the MOF achieved the lowest outlet air temperature. At 19.5 g/kgda, the MOF demonstrated higher adsorption rates (4 % and 0.3 %) than zeolite and silica gel. These findings highlight the potential of Al-Fum MOFs as energy-efficient solutions for controlling indoor air humidity, particularly for latent-sensible heat separation systems with conventional vapor compression bus air-conditioning systems.

Transient analysis of an efficient solar assisted air-conditioning system for subtropical climate with various solar thermal collectors

The air conditioning demand of the world is largely fulfilled by vapor compression systems; however, these systems are also responsible for depleting ozone layer due to the nature of refrigerants. Desiccant cooling systems integrated with solar thermal energy technologies could be an attractive alternative with some performance enhancement techniques. In this study, transient seasonal performance investigation is performed for an innovative solar integrated desiccant cooling system that uses regenerative evaporative cooler known as solar assisted desiccant integrated Maisotsenko cycle cooler for better cooling performance. Furthermore, transient annual performance analysis of solar system for meeting thermal energy requirement for regenerating the desiccant wheel in summer season and handling heating load of the building in winter season is also carried out with three different solar thermal collector technologies for finding out more efficient technology. The key performance indicators in this study are useful energy gain, solar source efficiency, auxiliary energy sharing, coefficient of performance, and solar fraction. The results of the key performance parameters are reported as monthly average values. The proposed integrated system resulted to be very efficient with a maximum COP value of 1.13 in April when latent cooling loads are low and 0.78 in August when latent cooling loads are higher. The system’s maximum cooling capacity is 24 kW in April corresponding to a sensible heat factor of 0.720. Furthermore, the regeneration temperature requirements ranged from 50 °C to 78 °C, respectively that makes it favorable to use low grade thermal energy through non concentrating solar thermal collectors. The regeneration thermal energy requirement for desiccant wheel fluctuates throughout the year, maximizing in August due to higher dehumidification requirements. The study also revealed that the evacuated tube collector technology is most suitable with average annual efficiency of around 36 %.

Impact of Insulation using Bio-sourced Materials on the Thermal and Energy Performance of a Typical Residential Building in Morocco

Among the measures to be taken to design and construct buildings with envelopes that are more energy-efficient, sustainable, and environmentally friendly is thermal insulation using a very wide range of insulating materials, either synthetic or of natural origin or derived from biomass. The present work represents a thermal and energy study aimed at improving the thermal comfort levels and energy requirements of a typical residential building located in the city of Al-Hoceima, Morocco. To this end, a series of numerical simulations were carried out using TRNSYS software to assess the impact of applying three bio-based insulation materials, namely hemp wool, wood fiber, and expanded cork, in the wall layer of the building. Different insulation scenarios were studied to make a choice that would ensure optimum comfort in the building with low energy demand. The results of this study show that insulating the roof with 8 cm of hemp wool contributes to energy savings of up to 36.7% and 35.2% for cooling and heating demand respectively. In thermal terms, improvements in the temperature inside the building have been achieved: in January, the maximum temperature recorded is 20.94°C, while in July, the maximum temperature is around 26.80°C.

Ambient wind conditions impact on energy requirements of an offshore direct air capture plant

This study proposes an off-grid direct air (carbon) capture (DAC) plant installed on the deck of an offshore floating wind turbine. The main objective is to understand detailed flow characteristics and CO2 dispersion around air contactors when placed in close proximity to one another. A solid sorbent DAC design is implemented using a commercially deployed air contactor configuration and sorbent. The sorbent is assumed to undergo a temperature vacuum swing adsorption cycle. Computational fluid dynamics (CFD) is used to determine the local conditions entering each unit based on varying wind speed and angle. Two-dimensional (2D) simulations were used to determine the pressure drop through a detailed air contactor design considering the sorbents APDES-NFC, Tri-PE-MCM, MIL-101(Cr)-PEI-800, and Lewatit VP OC 106. Only APDES-NFC was explored for further analysis in the three dimensional (3D) CFD dispersion model. 3D simulations were used to model flow patterns and CO2 dispersion using passive scalars. A worst case scenario is analyzed for all DAC units in adsorption mode with fans running simultaneously. 2D simulations show an under utilization of contactor length, and quantify pressure loss curves for four common sorbents. One commercially deployed sorbent is considered for further analysis; a pressure drop of 390.62 Pa is experienced for a flow velocity of 0.73 m s−1 through a 1.5m×1.5m×1.5m contactor. Using 3D simulations, fan energy demands are computed based on flow velocities and applied pressure gradients. There is found to be a decrease in overall fan power demand as wind speed increases. High wind speeds can passively drive the adsorption process with fans shut off at certain wind directions. This occurs at an average contactor inlet velocity of 17.5 m s−1, correlating to a hub height (150 m) wind speed of 24 m s−1. Thermal energy demands are computed based on inlet CO2 concentrations entering downstream units. Thermodynamic work for desorption based on an assumed second law efficiency is compared to thermal energy for desorption computed using a simplified isotherm method, taking into account the impacts of humidity on CO2 adsorption. Going from 414.72 ppm to 300 ppm CO2 inlet concentration requires an additional 63.9 kWh (t- CO2)−1 using the 2nd law thermodynamic efficiency method and 25.9 kWh (t- CO2)−1 using the isotherm method. Contactor arrangement, wind angles, and wind speeds have a significant impact on flow patterns experienced, and resulting CO2 dispersion. High wind speeds assist in CO2 dispersion, resulting in higher inlet concentrations to downstream DAC units and decreased thermal energy requirement.

Performance investigation of solar energy-aided compression-based building air conditioning strategies for variable climatic regions.

Decoupling cooling and ventilation tasks with an existing air conditioning methodology are a promising performance-enhancement technology. In this direction, different configurations of a desiccant-integrated independent ventilation element attached to a conventional cooling system are proposed in this study. This work establishes a quantitative comparative performance analysis among the different process air cooling (obtained through desiccant dehumidification) techniques for three different climates, namely, hot-dry, tropical, and Mediterranean. EnergyPlus simulations have been executed on a small-scale office building of 400-m2 area. The building constructional details and other required simulation input parameters follow benchmark standards. As the chemical dehumidification increases, the process air, i.e., supply air temperature that cannot be sent directly to the room, needs to be cooled. Three approaches for process air cooling have been considered: direct expansion (DX) cooling coil, indirect evaporative cooling (IEC), and sensible heat recovery wheel (SHRW). A solar collector assembly with a supporting heating arrangement is coupled with desiccant unit for regeneration. Outdoor air is used for regeneration in the case of the DX cooling coil and IEC, whereas return air is used in the heat recovery wheel case. Annual simulation results reveal that the SHRW-aided case performs superior than DX coil case for the pertinent climatic conditions, with 9.6 to 45.01% of annual energy savings. For the IEC, energy consumption was 1.8 to 18.38% less than that of DX coil. Also, using return air in this best-suited case reduces the net thermal energy requirement for regeneration by 14.63 to 71.65% with respect to DX coil.

Scenarios for the energy renovation of a residential building

In this paper, the results of the energy renovation of a residential building, aimed at introducing it into a Renewable Energy Community (CER), are presented. A case study located in Florence (Italy) is discussed. Static and dynamic energy models have been used to evaluate the energy performance of the building, to compare different scenarios based on heat pumps (independent or centralised generator) and to evaluate them under the perspective of EPBD parameters. A comparison has been made concerning energy consumption and CO2 emissions. In its current state, the building presents an energy performance index of 129.8 kWh/(m2year) (class D). The energy refurbishment with heat pump (A4, 24.7 kWh/(m2year)) and VMC system (A4, 39.3 kWh/(m2year)) ensures a strong reduction in CO2 emissions, respectively 5.5 kg/(m2year) and 8.7 kg/(m2year) against 24.4 kg/(m2year) with the current gas fired boiler. The centralized heat pump configuration allows to further reduce the energy consumption. With the same thermal energy requirement, the results show a reduction of 14% of the power needs (without total recovery), thanks to the better sizing of the generator. Furthermore, the centralized heat pump opens a perspective of direct self-consumption of the energy product by the photovoltaic system into a CER configuration. The paper shows that the energy renovation with a heat pump is an effective way to reach the EPBD objectives and decarbonize the residential heating and cooling sector.

Low-Temperature Vapor-Phase Growth of 2D Metal Chalcogenides.

2D metal chalcogenides (MCs) have garnered significant attention from both scientific and industrial communities due to their potential in developing next-generation functional devices. Vapor-phase deposition methods have proven highly effective in fabricating high-quality 2D MCs. Nevertheless, the conventionally high thermal budgets required for synthesizing 2D MCs pose limitations, particularly in the integration of multiple components and in specialized applications (such as flexible electronics). To overcome these challenges, it is desirable to reduce the thermal energy requirements, thus facilitating the growth of various 2D MCs at lower temperatures. Numerous endeavors have been undertaken to develop low-temperature vapor-phase growth techniques for 2D MCs, and this review aims to provide an overview of the latest advances in low-temperature vapor-phase growth of 2D MCs. Initially, the review highlights the latest progress in achieving high-quality 2D MCs through various low-temperature vapor-phase techniques, including chemical vapor deposition (CVD), metal-organic CVD, plasma-enhanced CVD, atomic layer deposition (ALD), etc. The strengths and current limitations of these methods are also evaluated. Subsequently, the review consolidates the diverse applications of 2D MCs grown at low temperatures, covering fields such as electronics, optoelectronics, flexible devices, and catalysis. Finally, current challenges and future research directions are briefly discussed, considering the most recent progress in the field.

A Simple and Effective Model for Predicting the Thermal Energy Requirements of Greenhouses in Europe

In this paper, a simple model is proposed for predicting the thermal energy requirements of greenhouses in Europe. The model estimates the annual heating requirements and the maximum required heating power, along with the corresponding heating and zero-energy operating periods. It is based on the greenhouse technical data (the overall heat loss coefficient, cover transmission, sensible absorbance), the cultivation conditions (temperature range), and the meteorological data (solar radiation and ambient temperature) according to the site characteristics (longitude and latitude). The model results can be obtained using a hand calculator. The model results are compared with those of a detailed model simulating a greenhouse’s thermal performance and they agreed with real data from the literature. Moreover, a model sensitivity analysis revealed the effect of various factors on the greenhouse’s energy requirements. The results proved that the most significant factor affecting heating requirements, the maximum heating power, and heating periods is the latitude of the greenhouse site, whereas zero-energy periods are primarily influenced by the plant cultivation temperature range and then by the latitude. According to our findings, in lower latitudes (40 to 50 degrees), heating requirements range from 250 to 430 kWh/m2/y, whereas, in higher latitudes (50 to 60 degrees), heating needs range from 430 to 650 kWh/m2/y.

Experimental investigation of a compound parabolic concentrator with aerogel and polycarbonate cover

This study experimentally investigates the performance of a novel compound parabolic concentrator integrated with aerogel and polycarbonate cover for process heat generation in low to medium temperature ranges. The experimental setup included a compound parabolic concentrator with a flat absorber surface at its focal plane, with an optically transparent and thermally insulating aerogel placed over it. The assembly was enclosed within a compound parabolic shape made of anodised aluminium sheets, with a concentration ratio of four, and protected by a transparent polycarbonate cover. The under-the-sun experiments were performed in Mumbai, India between March and June, 2022. A test set-up was developed to characterise the performance of this collector using the Indian Standard code 16648 (Part5, 2017). Four compound parabolic concentrator configurations were examined: only compound parabolic concentrator, compound parabolic concentrator with aerogel, compound parabolic concentrator with aerogel and polycarbonate cover, and compound parabolic concentrator with polycarbonate cover. The results indicate that while the addition of the polycarbonate cover offered protection to the reflector against environmental elements such as rain, wind, dust, snow, and bird droppings, it also led to a reduction in optical performance by about 16 %. It was also observed that using compound parabolic concentrator with aerogel results in a 30.6 % increase in the collector efficiency at the testing site with an inlet water temperature of 60°C, ambient temperature of 20°C, and an incident solar radiation of 700Wm-2. Thus, this research contributes to the advancement of stationary, non-imaging concentrating collectors, catering to the thermal energy requirements of various processes in the low to medium temperature range.

Simulation-based assessment of the climate change impact on future thermal energy load and indoor comfort of a light-weight ecological building across the six climates of Morocco

The potential effects of global climate change on buildings are a growing concern worldwide, as rising temperatures can significantly impact their energy performance and indoor thermal comfort conditions. This article examines the impact of global warming across six different climate zones of Morocco by comparing under 2050 RCP8.5 scenario the current and future thermal energy requirements and indoor comfort levels of a light-weight ecologically-designed detached residential house. The reference case study building is in a semi-arid climate of Morocco and empirically validated following the ASHRAE guideline 14, with CV(RMSE) less than 3.2 and NMBE less than 1.4 for the two 38-day monitored thermal zones.The study includes aframework to evaluate the thermal energy needs for maintaining indoor thermal comfort and the overheating intensity triggered by climate change and varying due to spatial scale. Overall, the findings show that Morocco will suffer with differing magnitudes from the temperature increase linked to global warming, which will result in an upsurge in the thermal needs for cooling, particularly in the southern regions of Morocco, and a general reduction in the heating thermal energy needs across the different climates of Morocco, with an annual thermal energy demand change ranging from −2.7% to 17%, depending on the investigated city. This wide variation in thermal energy demand underlines the need to assess the effects of the warming climate in the local context. Besides, under conditions of Air Conditioning (AC) failure, the Indoor Overheating Hours (IOH) increase up to 27% between the current climate conditions and the 2050 climate conditions while indoor temperature changes exceed 1.5 °C during the hottest days of the summer.Strategically, the research study intends to support global efforts to build resilient societies by bringing awareness to how susceptible indoor occupants are to projected warming temperatures. The study also lays the groundwork for prioritizing and assessing adaptation solutions to protect people's health, comfort, and productivity within buildings despite climate change in the most sustainable manner.

Exploring the Potential of Phase Change Material for Thermal Energy Storage in Building Envelopes

Buildings, with their significant energy consumption, pose a pressing concern for the future. Inadequate heating, ventilation, and air-conditioning (HVAC) systems further exacerbate thermal management difficulties and energy requirements. To address these challenges, Phase Change Materials (PCMs) offer valuable potential for sustainable energy reduction within the building sector, leveraging passive cooling and heating techniques. Numerical study has been conducted to explore the impact of embedding PCM within the building envelope on energy efficiency and thermal performance. The results reveal that PCM integration significantly reduces temperatures across all sections compared to scenarios without PCM. By passively absorbing and storing heat energy during phase change, PCM mitigates heat transfer through convection and conduction, leading to improved energy efficiency and reduced power consumption for cooling and heating purposes. Within the first 2 hours, the PCM achieves 50% of its average melting process, followed by a gradual decrease in the melting rate. It takes approximately 6 hours for the PCM to completely melt. As the PCM undergoes the melting process, the system's entropy values increase, reflecting an increase in disorder. At the tip of the building, the entropy value reaches 130 K/kg·K, which is more than three times the initial value. The integration of PCM in building envelopes shows promising potential for enhancing energy efficiency, thermal comfort, and durability. Future research should focus on optimizing PCM placement and configuration to maximize its benefits in diverse building designs and climatic conditions.

Thermal Integration of Solid Oxide Electrolysis Cell Systems with External Heat Sources to Maximize Heat Recuperation and Exergetic Efficiency

Green hydrogen is expected to play a significant role as an energy carrier in the future energy system. As the issue of climate change due to greenhouse gas emissions has recently emerged, efforts are being made to change from a carbon-based energy society to a hydrogen-based energy society worldwide. Among several hydrogen production technologies, green hydrogen refers to hydrogen that does not generate carbon dioxide at all in production processes such as water electrolysis by using renewable energy. The hydrogen production through water electrolysis is more mature than other green hydrogen production technologies and is the most popular green hydrogen production method because it is easy to mass-produce with a modular structure. In particular, a solid oxide electrolysis cell (SOEC) system, which has the highest efficiency among electrolysis systems, is drawing significant attention.The high efficiency of SOEC systems originates from heat utilization for water electrolysis, which makes it critical to have optimal thermal integration. The SOEC systems operating at the high temperature above 700°C need a significant amount of thermal energy for steam generation and inlet gas heating. To deal with these thermal energy requirements, the internal heat recuperation and the external heat source integration with system components must be implemented in an effective manner. The thermal integration is the most important part of the SOEC system design. However, the majority of previous studies have concentrated on the performance of unit-cells and stacks, ignoring thermal energy consumption of the systems and heat integration.The purpose of this study is to explain the basis of thermal integration and to investigate the effects of internal and external thermal integration on the whole system performance. The basic concept of the thermal integration of SOEC system is presented while considering internal heat recuperation and coupling with external heat sources. By using temperature-heat transfer analysis, the procedure to design the optimal thermal integration of the SOEC system is described. Based on the proposed system, a parametric study with respect to stack operating conditions (i.e., stack inlet temperature, air utilization, steam conversion, hydrogen fractions) is conducted in order to elucidate their effect on the system level performance. Then, the effects of external heat sources such as steam injection, indirect heat transfer with hot fluids and heat supply by an electrical heater are examined, with pinch analysis and exergetic performance evaluation. The results show that high temperature external heat is not always a prerequisite for the SOEC system. The systematic comparison with several heat integration methods provides a clear guideline to maximize the exergetic efficiency when designing and operating SOEC systems. Through the analysis, this study provides understanding the internal and external characteristics of the thermal integration.

A self-sustaining renewable energy driven hydrogen refuelling system utilising a metal hydride-based compressor

The transition towards carbon-free transportation is only possible by the adoption of renewable energy alternatives. Hydrogen-based transportation is an attractive option considering the availability of the required refuelling infrastructure. A well-established network of hydrogen refuelling infrastructure is important for the widespread commercialization of fuel-cell electric vehicles. The most expensive H2 refuelling components originate from hydrogen compression. Due to their ability to run on solar thermal energy, a metal hydride hydrogen compressor is used in this study. In this communication, the aim is to present a study on solar thermal based hydrogen compressors for a hydrogen refuelling station. An analytical study is presented on the energy assessment of a metal hydride compressor by considering three candidate pairs of metal hydrides (Pair 1: Ti0.95Zr0.05Cr0.8Mn0.8V0.2Ni0.2/Ti0.8Zr0.2Cr0.95Fe0.95V0.1; Pair 2: TiCr1.55Mn0.2Fe0.2/Ti0.9Zr0.1Mn1.4Cr0.35V0.2Fe0.05, Pair 3: La0.35Ce0.45Ca0.2Ni4.95Al0.05/Ti0.8Zr0.2Cr0.95Fe0.95V0.1) to achieve refuelling pressure of 700 bar. The variation in thermal efficiency of the compressor and thermal energy requirements with changes in heat source temperature, supply pressure and heat losses are presented. Furthermore, the economics of three pairs of alloys for high-pressure compression is compared. It was found that Ti0.95Zr0.05Cr0.8Mn0.8V0.2Ni0.2/Ti0.8Zr0.2Cr0.95Fe0.95V0.1 pair has the maximum compressor efficiency of 7.2% at supply pressure and heat source temperature of 25 bar and 150 °C, respectively. In addition, the study revealed that heat losses from the reactor could reduce efficiency by around 12.5%. The economic study revealed that the Ti0.95Zr0.05Cr0.8Mn0.8V0.2Ni0.2/Ti0.8Zr0.2Cr0.95Fe0.95V0.1 pair has the least cost for hydrogen compression among the other chosen pairs.

Modeling, simulation and performance evaluation of a PVT system for the Kenyan manufacturing sector

Manufacturing is an end-use sector that uses the most delivered energy, accounting for around 50% of all transported fuel globally and 40% of carbon dioxide emissions worldwide. Solar photovoltaic-thermal (PVT) energy can substitute the transported energy to meet thermal and electrical energy requirements, mitigating high energy costs and climatic problems. This research aimed to develop, simulate, and evaluate the capabilities of a solar photovoltaic-thermal system for potential use in Kenya's manufacturing sector. A multistage cluster sampling technique was used in the study to characterize the manufacturing industry. Additionally, a PVT system was simulated using MATLAB Simulink to ascertain the relationship of temperature and the PV electrical efficiency. The impact of incorporating a thermal collector into the PV system on electrical, thermal, and overall system efficiency, and also the system's potential for use in thermal processes in manufacturing, were assessed. From the characterization results, the agro-processing sector dominates with 35% representation, and the small-scale thermal energy category dominates at 80%. The simulation findings show that a small temperature increase leads to a small increment in short circuit current but a significant decline in open circuit voltage. As a consequence, the maximum power (Pmax) of the PV decreases, lowering its electrical efficiency. However, the integration of PV with thermal collector improved the electrical, thermal, and the entire system efficiencies by, 16.01%, 20%, and 36.13%, respectively. More than 75% of the electrical and thermal energy processes fall in the small energy category. Hence, the PVT system is suitable for small-scale low-to-medium heat thermal energy categories or as a substitute system for higher temperature processes to raise feed water temperatures and reduction of thermal energy cost. This study gives a new approach of the application of PVT system for thermal industrial applications.