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CO 2 shipping is a viable transport alternative when pipelines are impractical. Lack of experience in large-scale CO 2 shipping projects implies uncertainty in selecting optimal cargo conditions and operational safety procedures. The risk of uncontrolled release of CO 2 arises in case of mechanical failure of storage or cargo vessels, and a thorough understanding of the discharge phenomena, including the propensity for solid formation, is necessary to develop safety protocols. A refrigerated experimental setup is established in this study to investigate the release phenomena of liquid CO 2 under shipping conditions. The rig features a dome-ended cylindrical pressure vessel, a discharge pipe section and a liquid nitrogen refrigeration system that enables conditioning near the triple point – at ∼0.7 MPa, 223 K - and higher liquid pressures (∼2.6 MPa, 263 K). Pressure, temperature and mass monitoring were considered to enable an extensive observation of the leakage behaviour under typical operation scenarios. Three different sets of experiments were considered to inform the designer in the selection of optimal process conditions, with low-pressure (0.7 – 0.94 MPa, 223–228 K), medium-pressure (1.34–1.67 MPa, 234–245 K) and high-pressure tests (1.83–2.65 MPa, 249–259 K) demonstrating distinct behaviours relative to phase transitions, leakage duration and solidification of inventory. [ABSTRACT FROM AUTHOR]

The research work explores the impact of temperature on Silicon photovoltaic (PV) panels, considering Nigeria as a case study. It is found that high solar radiation in Nigeria increases the surface temperature of PV panels above 25 °C of the optimal operating temperature. The redundant energy gain from solar irradiance creates heat at the rear of solar panels and reduces their efficiency. Cooling mechanisms are therefore needed to increase efficiency. In this study, we demonstrated a unique hybrid system design employing a heat exchanger at the back of the panel, with water circulated through the back of the PV panel to cool the system. The system was simulated using TRNSYS at three locations in Nigeria—Maiduguri, Makurdi, and Port Harcourt. The results of the peak annual electrical power output in Maiduguri give a power yield of 1907 kWh/kWp, which is the highest, due to a high solar radiation average of 727 W/m2 across the year. For Makurdi, the peak annual electrical power output is 1542 kWh/kWp, while for Port Harcourt the peak power output is 1355 kWh/kWp. It was observed that the surface temperature of Polycrystalline Si-PV was decreased from 49.25 °C to 38.38 °C. The electrical power was increased from 1526.83 W to 1566.82 W in a day, and efficiency increased from 13.99% to 15.01%. [ABSTRACT FROM AUTHOR]

A study was carried out to investigate the CO 2 capture performance of limestone under atmospheric carbonations following pressurised calcination. A series of tests was carried out to study the role of pressurised calcination using a fluidised bed reactor. In this investigation, calcination of limestone particles was carried out at three levels of pressure: 0.1 MPa, 0.5 MPa, and 1.0 MPa. After calcination, the capture performance of the calcined sorbent was tested at atmospheric pressure. As expected, the results indicate that the carbonation conversion of calcined sorbent decreases as the pressure is increased during calcination. Pressurised calcination requires higher temperatures and causes an increase in sorbent sintering, albeit that it would have the advantage of reducing equipment size as well as the compression energy necessary for CO 2 transport and storage, and an analysis has been provided to give an assessment of the potential benefits associated with such an option using process software. [ABSTRACT FROM AUTHOR]

Steam can be used to lower calcination temperatures or to provide the process heat for calcination in a Ca-looping cycle because it can be removed from the CO 2 stream by simple condensation. Here, the performance of limestone for CO 2 removal from flue gases, calcined in the presence of steam, has been investigated. Three steam concentrations (28%, 48% and 78%) were used to investigate the effect of high-temperature steam in the calciner. For comparison, the effects of steam were compared to similar levels of N 2 as the primary diluent. Subsequent to calcination at elevated steam levels, the performance of the calcined sorbent was tested during carbonation with two levels of steam (6% and 20%) typical for flue gases from fossil fuel power plants. This allowed the effects of steam in carbonation to be investigated as well. As this study focused on CO 2 capture from flue gases produced by existing power plants (using Ca-looping as a post-combustion process), the corresponding industrial conditions were simulated for the carbonation atmosphere. Steam addition in the calciner was found to be more effective in improving capture than steam addition in the carbonator, with CO 2 capture capacity being increased with increasing steam levels in the calciner. [ABSTRACT FROM AUTHOR]

High temperature CO 2 and SO 2 sequential capture in a bubbling fluidised bed was investigated using a natural limestone and synthetic composite pellets. Calcination was conducted under oxy-combustion conditions, while carbonation and sulphation occurred in an air-combustion atmosphere. The goal of sequential capture of CO 2 /SO 2 is to desulphurise the flue gas first, followed by cyclic carbonation and calcination. Here, fresh sorbent is first used in the cyclic calcination/carbonation process and then the spent sorbent is sent for sulphation. The pellet carrying capacity is 0.29 g CO 2 /g sorbents for the first cycle, while that of natural limestone is about 0.45 g CO 2 /g sorbents. The carrying capacity first fell and then finally plateaued around 0.10 and 0.12 g CO 2 /g sorbents for limestone and pellets respectively. The SO 2 carrying capacity for limestone and pellets after 20 cycles of CO 2 capture was 0.17 and 0.22 g SO 2 /g sorbents respectively. This indicates that the sorbent spent in CO 2 capture can be effectively reused for SO 2 removal. Abrasion was observed to be the main mode of attrition, but some agglomeration was also found with increasing number of cycles and this may be a concern in the use of Ca-based sorbent for CO 2 or SO 2 fluidised bed capture. • Sequential capture of carbon and sulphur was investigated with a natural and synthetic limestone pellets. • Pellets performed better cyclic activity over a large number of cycles. • Experienced some weak agglomeration which can be destroyed by gently shaking or stirring. • Intensified attrition created cracks on the surface of limestone, however smoother surface on the pellets. [ABSTRACT FROM AUTHOR]

This study analyses the concept of a novel multi-crystallization system to achieve zero liquid discharge (ZLD) for desalination plants using an innovative heat recovery system consisting of a heat transfer fluid and a compressor to reduce energy consumption. The main focus is to recover water and separately extract salts from seawater brines with high purity, including calcite, anhydrite, sodium chloride, and epsomite, which can be sold to the cement industry. The system is compared with a conventional brine treatment system. The energy demand and economic feasibility of both systems are assessed to evaluate profitability at a scale of 1000 kg/h. The results estimate that the utilization of a heat recovery fluid reduces energy consumption from 690 kWhth/ton of feed brine to 125.90 kWhth/ton equaling a total electric consumption of 60.72 kWhe/ton. The system can recover 99.2% of water and reduce brine discharge mass by 98.9%. The system can recover 53.8% of calcite at near 100% purity, 96.4% of anhydrite at 97.7% purity, 91.6% of NaCl at near 100% purity, and 71.1% of epsomite at 40.7% purity. Resource recovery accounts for additional revenues, with halite and water accounting respectively for 69.85% and 29.52% of the income. The contribution of calcite and anhydrite to revenue is very low due to their low production. The levelized cost of water (LCOW) of the multi-crystallization system is 13.79 USD/m3 as opposed to 7.85 USD/m3 for the conventional ZLD system. The economic analyses estimate that the conventional ZLD system can achieve payback after 7.69 years. The high electricity cost, which accounts for 68.7% of the annual expenses, can be produced from renewable sources. [ABSTRACT FROM AUTHOR]

Ammonia/water absorption chillers are driven by low-grade heat and cover wide refrigeration temperatures. This paper analyses single-stage ammonia/water absorption chillers. A numerical model was developed based on the heat exchanger performance. The model captures variational heat exchanger performances and describes the actual cycle with varying boundary conditions. The detrimental effects of refrigerant impurity were analysed quantitatively under different operating conditions. The model was validated with experimental data. A basic cycle and three advanced cycles were analysed for sub-zero refrigeration by comparing the thermodynamic performances. A compression-assisted cycle extended the activation temperature from 80 to 60 °C. At the heat source of 120 °C, when a counter-current desorber or bypassed rich solution was used, the COP increased from 0.51 to 0.58 or 0.57, respectively. The operating parameters included the heat source temperatures, heat sink temperatures, the mass flow rates and mass concentrations of rich solutions. Higher heat source temperatures increase cooling capacity. The increase was around 20 kW for the basic cycle of sub-zero refrigeration. There is an optimum heat source temperature maximising the COP. Higher heat source temperatures increased the refrigerant mass flow rate and reduced the mass concentration. The mass concentration can decrease from 0.999 to 0.960. [ABSTRACT FROM AUTHOR]

This study explores the use of a novel activating agent and demonstrates the production and characterisation of activated carbon (AC) from a combine palm waste (CPW) in 3:2:1 proportion by weight of empty fruit bunch, mesocarp fibre and palm kernel shell. The resulting biomass was processed by a microwave-assisted method using trona and compared with material produced by conventional routes. These results demonstrate the potential of trona ore as an activating agent and the effectiveness of using a combined palm waste for a single stream activation process. It also assesses the effectiveness of trona ore in the elimination of alcohol, acids and aldehydes; with a focus on increasing the hydrophilicity of the resultant AC. The optimum results for the conventional production technique at 800 °C yielded a material with SBET 920 m2/g, Vtotal 0.840 cm3/g, a mean pore diameter of 2.2 nm and an AC yield 40%. The optimum outcome of the microwave assisted technique for CPW was achieved at 600 W, SBET is 980 m2/g; Vtotal 0.865 cm3/g; a mean pore diameter 2.2 nm and an AC yield of 42%. Fourier transform infrared spectrometry analyses showed that palm waste can be combined to produce AC and that trona ore has the capacity to significantly enhance biomass activation. [ABSTRACT FROM AUTHOR]

Renewable energy is a key solution in maintaining global warming below 2 °C. However, its intermittency necessitates the need for energy conversion technologies to meet demand when there are insufficient renewable energy resources. This study aims to tackle these challenges by thermo-electrochemical modelling and simulation of a reversible solid oxide fuel cell (RSOFC) and integration with the Haber Bosch process. The novelty of the proposed system is usage of nitrogen-rich fuel electrode exhaust gas for ammonia synthesis during fuel cell mode, which is usually combusted to prevent release of highly flammable hydrogen into the environment. RSOFC round-trip efficiencies of 41–53% have been attained when producing excess ammonia (144 kg NH 3 /hr) for the market and in-house consumption respectively. The designed system has the lowest reported ammonia electricity consumption of 6.4–8.21 kWh/kg NH 3 , power-to-hydrogen, power-to-ammonia, and power-generation efficiencies of 80%, 55–71% and, 64–66%. [Display omitted] • P2A to power system enhances renewable energy usage by solving intermittency issues. • Optimum P2A to power system design and operating parameters determined. • Argon-free nitrogen resulting to non-limiting Haber Bosch recycle-loop fraction. • Novel system has lowest reported ammonia synthesis electricity consumption. • High power-to-ammonia efficiency attained, and excess ammonia available for market. [ABSTRACT FROM AUTHOR]

The hybrid renewable energy system based on concentrated solar power (CSP) technology has been demonstrated as a promising approach to utilise renewable energy. To combine the configuration and operation with practical application scenarios, this study investigates three different operation modes of the hybrid system which consists of one or more components of a CSP power plant, a thermal energy storage system, photovoltaic (PV) panels, wind turbines, batteries and electric heaters. A multi-objective optimisation for the capacity parameters of subsystems is conducted for three operation modes and two typical locations, considering the actual power demand and electricity prices. Results show that cooperating with the given CSP plant, the simultaneous development of PV panels, wind turbines and batteries is recommended in Delingha, while in Lhasa, the improvement relies more on the expansion of PV panels and batteries. By providing 31.50%–38.72% of the total power, the CSP subsystem contributes significantly to providing reliable electricity in fluctuating weather conditions and at night. And 20.58–59.85 GWh of excess electricity is reused through electric heaters instead of being wasted. Furthermore, the operation in local consumption mode shows the best resilient to uncertainty of the meteorological conditions, with the deviation within 1% under forecast error of 5%–20%. • Optimal configurations are obtained for three operation modes in two locations. • Performance curves in local consumption mode show consistency across sites. • Similar trends but higher profit is obtained in VPP mode compared to sales mode. • Electric heaters enable 20.58–59.85 GWh of electricity reused instead of wasted. • A deviation of 1 % is seen in local consumption mode for forecast errors of 5%–20 %. [ABSTRACT FROM AUTHOR]

The agricultural sector faces multiple challenges linked to increased climate uncertainty, causing severe shocks including increased frequency of extreme weather events, new pest and disease risks, soil degradation, and pre and postharvest food losses. This situation is further exacerbated by geopolitical instability and volatility in energy prices impacting on fertiliser supplies and production costs. Net zero strategies are vital to achieve both food security and address negative environmental impacts. This perspective paper reviews and assesses the most viable options (actions) to achieve net zero with a focus on the arable/livestock and protected cropping sectors in the UK. The methodology was based on a synthesis of relevant literature, coupled with expert opinions using the holistic PESTLE (Political, Environmental, Social, Technological, Legal and Environmental) approach to categorise actions, leading to formulation of a roadmap to achieve net zero. The PESTLE analysis indicated that there are technically and economically viable actions available which need to be prioritised depending on the ease of their implementation within the two crop sectors investigated. These actions include (i) policy changes that are better aligned to net zero; (ii) circular economy approaches; (iii) connectivity and accessibility of information; (iv) increased resilience to shocks; (v) changing diets, nutrition and lifestyles; (vi) target setting and attainment; and (vii) farm economics and livelihoods. The outputs can be used by stakeholders and decision makers to inform policy and drive meaningful changes in global food and environmental security. [ABSTRACT FROM AUTHOR]

Poor sanitation is one of the major hindrances to the global sustainable development goals. The Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation is set to develop affordable, next-generation sanitary systems that can ensure safe treatment and wide accessibility without compromise on sustainable use of natural resources and the environment. Energy recovery from human excreta is likely to be a cornerstone of future sustainable sanitary systems. Faeces combustion was investigated using a bench-scale downdraft combustor test rig, alongside with wood biomass and simulant faeces. Parameters such as air flow rate, fuel pellet size, bed height, and fuel ignition mode were varied to establish the combustion operating range of the test rig and the optimum conditions for converting the faecal biomass to energy. The experimental results show that the dry human faeces had a higher energy content (∼25 MJ/kg) than wood biomass. At equivalence ratio between 0.86 and 1.12, the combustion temperature and fuel burn rate ranged from 431 to 558 °C and 1.53 to 2.30 g/min respectively. Preliminary results for the simulant faeces show that a minimum combustion bed temperature of 600 ± 10 °C can handle faeces up to 60 wt.% moisture at optimum air-to-fuel ratio. Further investigation is required to establish the appropriate trade-off limits for drying and energy recovery, considering different stool types, moisture content and drying characteristics. This is important for the design and further development of a self-sustained energy conversion and recovery systems for the NMT and similar sanitary solutions. [ABSTRACT FROM AUTHOR]

With the improvement of people's living standards, they have higher requirements for indoor thermal comfort in the cold season. Solar wall utilizing solar energy for heating can reduce carbon emissions and achieve carbon neutrality. In the aspect of solar wall research, the influence of wall structure on the thermal performance of double-channel porous solar wall is limitedly investigated. In fact, the optimization design of wall structure is important for the thermal performance of solar wall and its applications. Therefore, a simplified three dimensional room model is built to study the influence of the wall structure on the thermal performance of porous solar wall by numerical simulation. With this model, different channel spacing and thickness of porous walls were used to determine the optimal design for a double-channel porous solar wall in terms of enhancing the heat storage. Moreover, the influence of the surface emissivity on the characteristics of heating and temperature field of double-channel porous solar wall are studied based on the optimal structure. The CFD simulation results indicate that the optimal structure parameters should include spacing of 0.08 m for channel 1, the porous wall thickness should be 0.08 m, and the air channel 2 spacing should be 0.06 m. The temperature of air channel 1 and air channel 2, the indoor temperature, and the heat storage of porous wall decrease with the increase of the surface emissivity of the porous wall. In order to improve the heat storage performance of double-channel porous solar wall, the outer surface of the porous wall should use a lower emissivity material. The outer surface emissivity of porous wall has a significant impact on the heat storage of the porous wall and little effect on the thermal storage wall. The temperature of porous wall is always higher than that of outdoor environment temperature. [ABSTRACT FROM AUTHOR]

• PCM technology saves energy, moderates temperatures, boosts solar control, and cuts consumption by 14–90%. • Windows with PCM panels reduce heat transfer up to 66%, lower solar gain. • PCMs plus nocturnal radiative cooling cuts surface temperatures over 13° Celsius. • Solar-powered desiccant AC with PCM achieves 75% average energy savings, 60–90% peak load reduction. • PCM-infused surfaces reduce energy use by 20%-66%, offering adaptive thermal regulation across various climates. Phase Change Materials (PCMs) present cutting-edge technology with substantial promise for advancing sustainable and energy-efficient cooling in buildings. These materials can absorb and release latent heat during phase transitions, facilitating thermal energy storage and temperature regulation. This comprehensive literature review explores various strategies and methods for implementing passive cooling with PCMs in buildings. The integration of PCMs enhances multiple passive cooling approaches, including solar control, ground cooling, ventilation-based heat dissipation, radiative cooling, and thermal mass-based heat modulation. The analysis delves into PCM classifications, encapsulation techniques, melting enthalpies, integration into diverse building envelopes, and performance across different climates. The findings from this comprehensive review indicated that PCM walls introduce a 2-hour delay in heat transfer and mitigate external temperature fluctuations. Windows equipped with PCM panels reduce heat transfer by 66 %. Combining PCMs with nocturnal radiative cooling leads to interior surface temperature reductions exceeding 13 °C. Natural ventilation with PCMs results in notable energy savings of up to 90 % in hot climates. The combination of free cooling and PCM thermal storage reduces charging times by 35 % while enhancing heat transfer. Simulations performed in the open literature suggested that strategic placement of PCMs in lightweight building walls reduces heat flux and overall energy consumption. Despite facing challenges related to scalability, compatibility, reliability, and recycling, PCM solutions demonstrate robust potential. When integrated thoughtfully into building design, PCMs significantly improve thermal performance and energy efficiency. Experimental validations confirm energy reductions ranging from 14 % to 90 %, underscoring the adaptability of passive cooling techniques leveraging PCM thermal storage and heat transfer capabilities across various climates. [ABSTRACT FROM AUTHOR]

• Integration of four novel sCO 2 cycles with coal-fired power plant. • Efficiency of sCO 2 cycle is higher than steam Rankine cycle by 3–4%pts. • sCO 2 cycles can reduce the cost of electricity by 6–8% than steam Rankine cycle. • Increasing turbine inlet temperature by 140 °C increases efficiency by 3–4%pts. • Increasing turbine inlet temperature doesn't show reduction in cost of electricity. Supercritical carbon dioxide (sCO 2) cycles can achieve higher efficiencies than an equivalent steam Rankine cycle at higher turbine inlet temperatures (>550 °C) with a compact footprint (tenfold). sCO 2 cycles are low-pressure ratio cycles (~4–7), therefore recuperation is necessary, which reduces the heat-addition temperature range. Integration of sCO 2 cycles with the boiler requires careful management of low-temperature heat to achieve higher plant efficiency. This study analyses four novel sCO 2 cycle configurations which capture the low-temperature heat in an efficient way and the performance is benchmarked against the state-of-the-art steam Rankine cycle. The process parameters (13–16 variables) of all the cycle configurations are optimised using a genetic algorithm for two different turbine inlet temperatures (620 °C and 760 °C) and their techno-economic performance are compared against the advanced ultra-supercritical steam Rankine cycle. A sCO 2 power cycle can achieve a higher efficiency than a steam Rankine cycle by about 3–4% points, which is correspond to a plant level efficiency of 2–3% points, leading to cost of electricity (COE) reduction. Although the cycle efficiency has increased when increasing turbine inlet temperature from 620 °C to 760 °C, the COE does not notably reduce owing to the increased capital cost. A detailed sensitivity study is performed for variations in compressor and turbine isentropic efficiency, pressure drop, recuperator approach temperature and capacity factor. The Monte-Carlo analysis shows that the COE can be reduced up to 6–8% compared to steam Rankine cycle, however, the uncertainty of the sCO 2 cycle cost functions can diminish this to 0–3% at 95% percentile cumulative probability. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the theory on the translation of a measured chord length distribution (CLD) into its particle size distribution (PSD), which was developed in the first part of this study [Li and Wilkinson, 2005. Determination of non-spherical particle size distribution from chord length measurements. Part 1: theoretical analysis. Chemical Engineering Science 60, 3251–3265], has been validated using experimental results. CLDs were measured using the Lasentec focused beam reflectance measurement (FBRM) with three different materials, spherical ceramic beads and non-spherical plasma aluminium and zinc dust particles. Meanwhile, the particle shape and PSD of each material were also investigated by image analysis (IA). Comparison of the retrieved PSDs with the measured PSDs by IA shows that the PSD can be retrieved from a measured CLD successfully using the proposed iterative nonnegative least squares (NNLS) method based on the PSD–CLD model. [Copyright &y& Elsevier]

• Assessed CO 2 shipping as a global decarbonisation strategy for future developments. • Identified technical and safety challenges encountered during in CO 2 shipping chain. • Evaluated the environmental impact of shipping emissions in the transport chain. • Summarised emission control technologies as a key enabler in the CO 2 shipping chain. Carbon Capture, Utilisation and Storage (CCUS) can reduce greenhouse gas emissions for a range of technologies which capture CO 2 from a variety of sources and transport it to permanent storage locations such as depleted oil fields or saline aquifers or supply it for use. CO 2 transport is the intermediate step in the CCUS chain and can use pipeline systems or sea carriers depending on the geographical location and the size of the emitter. In this paper, CO 2 shipping is critically reviewed in order to explore its techno-economic feasibility in comparison to other transportation options. This review provides an overview of CO 2 shipping for CCUS and scrutinises its potential role for global CO 2 transport. It also provides insights into the technological advances in marine carrier CO 2 transportation for CCUS, including preparation for shipping, and in addition investigates existing experience and discusses relevant transport properties and optimum conditions. Thus far, liquefied CO 2 transportation by ship has been mainly used in the food and brewery industries for capacities varying between 800 m3 and 1000 m3. However, CCUS requires much greater capacities and only limited work is available on the large-scale transportation needs for the marine environment. Despite most literature suggesting conditions near the triple-point, in-depth analysis shows optimal transport conditions to be case sensitive and related to project variables. Ship-based transport of CO 2 is a better option to decarbonise dislocated emitters over long distances and for relatively smaller quantities in comparison to offshore pipeline, as pipelines require a continuous flow of compressed gas and have a high cost-dependency on distance. Finally, this work explores the potential environmental footprint of marine chains, with particular reference to the energy implications and emissions from ships and their management. A careful scrutiny of potential future developments highlights the fact, that despite some existing challenges, implementation of CO 2 shipping is crucial to support CCUS both in the UK and worldwide. [ABSTRACT FROM AUTHOR]

Desalination is an energy intensive process requiring adequate pre- and post- treatment. The novelty of this paper is that it jointly reviews the technologies for pre-treatment, desalination and post-treatment and bridges the gap between them while comparing the treatment methods needed depending on the type of feed water including seawater, brackish water, municipal and industrial wastewater. Those different streams show wide variability, sometimes containing organics, oil or scaling precursors which require adequate treatment. Nowadays, membrane pre-treatment methods have become promising alternatives to conventional pre-treatment techniques thanks to their flexibility. Hybrid desalination technologies have shown great potential in reducing energy consumption. Moreover, desalination plants produce large quantities of brines which require post-treatment to reduce environmental impacts. Current research on post-treatment is looking into recovering salts, metals and potable water from brines to achieve zero liquid discharge (ZLD). Thermal-based ZLD technologies are capable of extracting those resources while membrane-based ZLD methods are mostly limited to pre-concentration and water recovery due to fouling issues. Several studies have shown that ZLD systems can lower the cost of water and increase profitability if crystals and water are recovered and sold for additional revenue. • Overview of pretreatment technologies and scrutinize its potential role in the desalination industries. • Potential environmental impact of the waste brines with reference to the zero liquid discharge and their management • Pre and post treatment mapping to support desalination industries. • Explore options in the potential reduction of the environmental damage via zero liquid discharges [ABSTRACT FROM AUTHOR]

• A general integration method of multi-heat-source systems is proposed. • The external and internal irreversibility due to finite-time was considered. • The distribution diagram of the optimum thermodynamic structure was drawn. • Four coupled systems were applied to determine the optimum integration position. Multi-heat-source power generation system is a promising technology to reduce fossil fuel consumption and save investment costs by integrating several heat sources and sharing power equipment components. Researchers have conducted many case studies based on specific power plants to find the preferred integration scheme. However, there is still no unified theory to guide the integration of different energy sources. To explore a common method to integrate various energy sources, this work developed a general multi-heat-source integrated system model based on finite-time thermodynamics, considering the external and internal irreversibility due to the constraint of finite-time and finite-size. The generalised expressions for optimum integration method are explored and expressed in dimensionless parameters. This study indicated the system with two heat-sources performs differently in four regions due to the variation of endothermic temperatures. The characteristics of energy flow and irreversibility reveal that by adding a second heat-source, the first heat-source energy can be substantially reduced at the cost of system efficiency slightly decreasing. Then four application cases for solar-aided coal-fired power plants are conducted to check its feasibility and potential to provide the performance bound of integrating multi-heat-sources. [ABSTRACT FROM AUTHOR]

Solar-aided coal-fired power generation systems have been extensively studied and exhibit several advantages in the utilisation of solar energy. The issue with the solar augmentation of coal-fired plants is the limitation of the potential solar contribution that is practical to achieve when considering boiler safety issues. This study proposes the combination of parabolic troughs and solar towers to collect solar energy, that is then introduced into the preheaters and boilers of coal-fired power plants. Under the same investment conditions, this combination of solar technologies can provide more solar exergy and reduce the practical constraints on the solar contribution. The paper shows that the potential for a 660MW e power plant, integrated with a combined solar field allows the highest solar exergy share of 8.51% to be reached. This enables an increased fuel saving of at least 1.58 and 4.24 g/kWh compared to other systems, that gives a minimum coal consumption of 253.17 and 255.83 g/kWh, respectively. The combined solar field provides a maximum available solar exergy of 69.43 MW th , which is 7.83%–11.88% higher than the alternative compared systems. The enhanced solar exergy contribution and cost-effectiveness can be observed in this novel system under different solar loads and cost conditions. • Original combined solar trough and tower aided coal-fired power is proposed. • Solar exergy share increased by 0.57–1.65% under the same investment condition. • In proposed system, minimum 1.58–4.24 g/kWh coal fuel can be further saved. • Optimum configuration of solar field for better cost-effectiveness is explored. [ABSTRACT FROM AUTHOR]

• Identified the optimal GT pressure ratio requirements for four sCO 2 cascaded cycles. • Pressure ratio of a sCO 2 cycle at maximum efficiency is higher than a steam cycle. • Multi-objective optimisation is done to compare sCO 2 cycles on equivalent basis. • Performance prediction maps were produced to help selecting an optimal GT. • A new sCO 2 cycle is proposed that improves efficiency by 1.4 percentage points. A closed-loop, indirect, supercritical Carbon Dioxide (sCO 2) power cycle is attractive for fossil-fuel, solar thermal and nuclear applications owing to its ability to achieve higher efficiency, and compactness. Commercial Gas Turbines (GT's) are optimised to yield maximum performance with a conventional steam Rankine cycle. In order to explore the full potential of a sCO 2 cycle the whole plant performance needs to be considered. This study analyses the maximum performance and cost of electricity for five sCO 2 cascaded cycles. The plant performance is improved when the GT pressure ratio is considered as a design variable to a GT to optimise the whole plant performance. Results also indicate that each sCO 2 Brayton cycle considered, attained maximum plant efficiency at a different GT pressure ratio. The optimum GT pressure ratio to realise the maximum cost reduction in sCO 2 cycle was higher than the equivalent steam Rankine cycle. Performance maps were developed for four high efficient cascaded sCO 2 cycles to estimate the specific power and net efficiency as a function of GT turbine inlet temperature and pressure ratio. The result of multi-objective optimisation in the thermal and cost (c$/kWh) domains and the Pareto fronts of the different sCO 2 cycles are presented and compared. A novel sCO 2 cycle configuration is proposed that provides ideal-temperature glide at the bottoming cycle heat exchangers and the efficiency of this cycle, integrated with a commercial SGT5-4000F machine in lieu of a triple-pressure steam Rankine cycle, is higher by 1.4 percentage point. [ABSTRACT FROM AUTHOR]

Highlights • Solar aided coal-fired power system is simulated for typical meteorological year. • Annual efficiency and levelized cost of electricity are characterized. • Annual coal consumption reduced over 14,000 tons for a 600 MW e power system. • Thermal storage capacity is optimized to achieve lowest cost of electricity. Abstract The integration of solar energy into coal-fired power plants has been proven as a potential approach in the utilization of solar energy to reduce coal consumption. Moreover, solar augmentation offers low cost and low risk alternatives to stand-alone solar thermal power plants. In this study, the annual performance of a solar tower aided coal-fired power (STACP) system is investigated, and the influence of thermal storage system capacity on the annual solar generating power and annual solar-to-electricity efficiency is explored. The thermal storage system capacity is optimized to obtain the lowest levelized cost of electricity (LCOE). At the same time, the influence and sensitivity of several important economic factors are explored and assessed. Results demonstrate that compared to a coal-fired power system, the reduction in the annual average coal consumption rate of the STACP system with high direct normal irradiance (DNI), medium DNI, and low DNI are 5.79, 4.52, and 3.22 g/kWh, respectively. At a minimum, the annual coal consumption can be reduced by 14,000 t in a 600 MW e power generation unit. Because the same solar field is considered under different DNI conditions, the LCOE in the high DNI, medium DNI, and low DNI scenarios are all fairly similar (6.37, 6.40, and 6.41 ¢/kWh, respectively). When the solar multiple is 3.0, the optimal thermal storage capacity of the STACP system, with high, medium, and low DNIs are 6.73, 4.42, and 2.21 h, respectively. The sensitivity analysis shows that the change in economic parameters exerts more influence on the STACP system with the high DNI compared with the other two scenarios. [ABSTRACT FROM AUTHOR]

Abstract Solar aided coal-fired power system has been proven to be a promising way to utilise solar energy in large scale. In this paper, the performances of the solar tower aided coal-fired power (STACP) system at 100% load, 75% load, and 50% load for different days are investigated and the maximum solar power that the boiler can absorb under different plant loads are explored. Then, the effects of solar multiple (SM) and the thermal energy storage (TES) hour on the daily performance of STACP system are investigated. Results show that the maximum solar power that a 600 MW e boiler can absorb at 100% load, 75% load and 50% load are 76.4 MW th , 54.2 MW th and 23.0 MW th , respectively. Due to the augmented energy from the solar field, the maximum standard coal consumption rate is reduced by 13.53 g/kWh, 12.81 g/kWh and 8.22 g/kWh at 100% load, 75% load and 50% load, respectively. With an increase of solar power input, the boiler efficiency, overall system efficiency and solar thermal-to-electricity efficiency show a downward trend. In addition, the daily coal consumption of summer solstice is the lowest while the winter solstice is the highest for a particular SM and TES hour. Highlights • Performances of STACP system are investigated at different loads with different solar shares. • The maximum solar energy that the boiler can absorb is determined. • Performances of STACP system are investigated at different weather conditions. • Daily performance of STACP system are explored with different SM and TES hours. [ABSTRACT FROM AUTHOR]

A Solar Tower Aided Coal-fired Power (STACP) system utilizes a solar tower coupled to a conventional coal-fired power system to reduce pollutants, greenhouse gas emissions and the investment of solar energy facilities. This paper examines three different schemes for integrating solar energy into a conventional boiler. For each scheme, an energy and exergy analysis of a 600 MW e supercritical coal-fired power system is combined with 53 MW th of solar energy in both a fuel saving mode and a power boosting mode. The results show that, for all these integration schemes, the boiler’s efficiency and system’s efficiency are reduced. However, the standard coal consumption rate is lower in comparison to conventional power plants and the standard coal consumption rate in the fuel saving mode is lower than that in the power boosting mode for all three schemes. Comprehensively considering both the standard coal consumption rate and efficiency, the scheme that uses solar energy to heat superheat steam and subcooled feed-water is the best integration option. Compared with a coal-fired only system, the saved standard coal consumption rate of the above mentioned scheme in fuel saving mode and power boosting mode can reach up to 11.15 g/kWh and 11.11 g/kWh, respectively. Exergy analysis shows, for STACP system, exergy losses of boiler and solar field contribute over 88% of whole system’s exergy loss. [ABSTRACT FROM AUTHOR]

This article describes the design and commissioning of a micro-combustor for energy recovery from human faeces, which can operate both in updraft and downdraft modes. Energy recovery from faecal matter via thermochemical conversion has recently been identified as a feasible solution for sanitation problems in low income countries and locations of high income countries where access to sewage infrastructures is difficult or not possible. This technology can be applied to waterless toilets with the additional outcome of generating heat and power that can be used to pre-treat the faeces before their combustion and to ensure that the entire system is self-sustaining. The work presented here is framed within the Nano Membrane Toilet (NMT) project that is being carried out at Cranfield University, as part of the Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation. For this study, preliminary trials using simulant faeces pellets were first carried out to find out the optimum values for the main operating variables at the scale required by the process, i.e. a fuel flowrate between 0.4 and 1.2 g/min of dry faeces. Parameters such as ignition temperature, residence time, and maximum temperature reached, were determined and used for the final design of the bench-scale combustor prototype. The prototype was successfully commissioned and the first experimental results, using real human faeces, are discussed in the paper. [ABSTRACT FROM AUTHOR]

With about 2.4 billion people worldwide without access to improved sanitation facilities, there is a strong incentive for development of novel sanitation systems to improve the quality of life and reduce mortality. The Nano Membrane Toilet is expected to provide a unique household-scale system that would produce electricity and recover water from human excrement and urine. This study was undertaken to evaluate the performance of the conceptual energy and water recovery system for the Nano Membrane Toilet designed for a household of ten people and to assess its self-sustainability. A process model of the entire system, including the thermochemical conversion island, a Stirling engine and a water recovery system was developed in Aspen Plus®. The energy and water recovery system for the Nano Membrane Toilet was characterised with the specific net power output of 23.1 Wh/kg settledsolids and water recovery rate of 13.4 dm 3 /day in the nominal operating mode. Additionally, if no supernatant was processed, the specific net power output was increased to 69.2 Wh/kg settledsolids . Such household-scale system would deliver the net power output (1.9–5.8 W). This was found to be enough to charge mobile phones or power clock radios, or provide light for the household using low-voltage LED bulbs. [ABSTRACT FROM AUTHOR]

• Conversion feasibility of bread waste (BW) into bioethanol and biomethane. • High glucose yield (75–98 g/L) was achieved from acidic/enzymatic hydrolysis of BW. • Ethanol yield of 0.47 g/g from AH and BMP of 345 CH 4 /g VS from ABW + FR was obtained. • Ethanol yield of 0.49 g/g from EH and BMP of 379 CH 4 /g VS from EBW + FR was obtained. • BW-based ethanol reduces 50% fossil energy use and GWP of 0.018 kg CO 2 /kg of BW. Bread is the second most wasted food in the UK with annual wastage of 292,000 tons. In the present work, bread waste (BW) was utilized for fermentative production of ethanol by Saccharomyces cerevisiae KL17. Acidic and enzymatic saccharification of BW was carried out resulting in the highest glucose release of 75 and 97.9 g/L which is 73.5 and 95.9% of theoretical yield, respectively. The obtained sugars were fermented into ethanol initially in shake flask followed by scale up in bioreactor in batch and fed-batch mode. In the fed-batch mode of cultivation, the maximum ethanol titers of 111.3, 106.9, and 114.9 g/L with conversion yield and productivity of 0.48, 0.47, and 0.49 g/g, and 3.1, 3.0, and 3.2 g/L.h was achieved from pure glucose, glucose-rich acidic and enzymatic hydrolysates, respectively. Further to improve the process economics, the solid residues after acidic (ABW) and enzymatic (EBW) hydrolysis of BW along with respective fermentation residues (FR) obtained after the ethanol production were pooled and subjected to anaerobic digestion. The solid residue from ABW + FR, and EBW + FR yielded a biochemical methanation potential (BMP) of 345 and 379 mL CH 4 /g VS, respectively. Life cycle assessment of the process showed that the total emissions for ethanol production from BW were comparable to the emissions from more established feedstocks such as sugarcane and maize grain and much lower when compared to wheat and sweet potato. The current work demonstrates BW as promising feedstock for sustainable biofuel production with the aid of circular biorefining strategy. To the authors knowledge, this is the first time, such a sequential system has been investigated with BW for ethanol and biomethane production. Further work will be aimed at ethanol production at pilot scale and BMP will be accessed in a commercial anaerobic digester. [ABSTRACT FROM AUTHOR]

Pollutant emissions from coal-fired power system have been receiving increasing attention over the past few years. Integration of solar thermal energy can greatly reduce pollutant emissions from these power stations. The performances of coal-fired power system (S1), solar aided coal-fired power system with thermal storage (S2), and solar aided coal-fired power system without thermal storage (S3) with three capacities of each kind of system (i.e., nine subsystems) were analyzed over the entire life span. The pollutant emissions and primary energy consumptions (PECs) of S1, S2, and S3 were estimated using life cycle assessment (LCA). The evaluation value of global warming potential (GWP), acidification potential (AP), respiratory effects potential (REP) and PEC were obtained based on the LCA results. Furthermore, the system investments were estimated, and grey relation theory was used to evaluate the performance of the three types of systems comprehensively. Finally, in order to find the effect of some main factors on the solar aided coal-fired power system (SACFPS), uncertainty analysis has been carried out. The LCA results show that the pollutant emissions and PEC mainly take place in the fuel processing and operation stages for all three system types, and S2 performs the best among the three systems based on the grey relation analysis results. And the uncertainty analysis shows that with longer life span, the power system have better performance; with higher coal price, the power system will have worse performance; with lower solar collector field cost, the solar aided coal-fired power system will be more profitable than the base-case coal-fired power system. [ABSTRACT FROM AUTHOR]

The new challenge of the European Commission is to limit water consumption in Concentrating Solar Power (CSP) plants, especially significant in the cooling process. Hybrid cooling systems are presented as a potential solution to achieve water consumption reduction since they also avoid a high penalty of efficiency loss in the power block. In this work, a hybrid cooling pilot plant installed at Plataforma Solar de Almería is evaluated experimentally. The system has been tested under different ambient and operating conditions to analyze their influence on the water and electricity consumption. The results reveal that significant water savings were achieved in comparison with the conventional only-wet configuration. Concretely, a maximum water consumption saving of 67% was found at high ambient temperatures (between 25 and 30 °C) and for a thermal load of 80% when a hybrid configuration was used. The optimal operating strategies that achieve a tradeoff between low water and electricity consumption have been identified by two efficiency indexes: the specific electricity and water consumption. The parallel configuration was the optimal one in most of the cases. At high ambient temperatures and 80% thermal load, the electricity and water consumptions of this configuration were 0.033 kW e /kW th and 0.071 L/kW th , respectively. • Test campaign to investigate the optimal configurations of a hybrid cooler. • Trade-off between water and electric energy consumption under several conditions. • Specific electricity consumption and specific water consumption for the evaluation. • Maximum water consumption saving of 67% for parallel configuration split ratio 25%. • Maximum electricity reduction of 59% for parallel configuration split ratio 50%. [ABSTRACT FROM AUTHOR]

Integration of thermal energy storage with concentrated solar power (CSP) plant aids in smoothing of the variable energy generation from renewable sources. Supercritical carbon dioxide (sCO 2) cycles can reduce the levelised cost of electricity of a CSP plant through its higher efficiency and compact footprint compared to steam-Rankine cycles. This study systematically integrates nine sCO 2 cycles including two novel configurations for CSP applications with a two-tank sensible heat storage system using a multi-objective optimisation. The performance of the sCO 2 cycles is benchmarked against the thermal performance requirement of an ideal power cycle to reduce the plant overnight capital cost. The impacts of the compressor inlet temperature (CIT) and maximum turbine inlet temperature (TIT) on the cycle selection criteria are discussed. The influence of the cost function uncertainty on the selection of the optimal cycle is analysed using Monte-Carlo simulation. One of the novel cycle configurations (C8) proposed can reduce the overnight capital cost by 10.8% in comparison to a recompression Brayton cycle (C3) for a CIT of 55 °C and TIT of 700 °C. This work describes design guidelines facilitating the development/selection of an optimal cycle for a CSP application integrated with two-tank thermal storage. • Optimisation of 9 sCO 2 cycles (2 novel) integrated with CSP and sensible heat TES. • Techno-economic evaluation of impact of heat addition temperature difference (ΔT). • Maximum cycle efficiency away from the optimal heat addition ΔT increases TES cost. • Increasing turbine inlet temperature from 600 to 700 °C increases overnight cost. • Novel cycle reduces the overnight capital cost by 10.8% over recompression cycle. [ABSTRACT FROM AUTHOR]

• Off-design Pareto fronts of sCO 2 cycle using multi-objective optimisation approach. • Storage capacity reduces by 25% at 55 °C compressor inlet temperature (design = 42 °C). • Off-design compressor inlet pressure estimation method to maximise efficiency. • Capacity factor increases by 10.8% when operating the plant in maximum power mode. • Number of start-ups reduce by about 50% when operating in maximum efficiency mode. Supercritical Carbon Dioxide (sCO 2) cycles can achieve higher efficiency compared to steam-Rankine or Air-Brayton cycles, therefore they are promising for concentrated solar power applications. Although sCO 2 cycles show higher design efficiency, the off-design efficiency is highly sensitive to the ambient conditions, impacting the power block net-power and heat input. In the present work a recompression sCO 2 cycle is connected to a central-tower solar field with two-tank thermal storage delivering molten chloride salt at 670 °C. The temperature of the molten-salt exiting from the power block and returning to the cold storage tank increases by 46 °C with respect to the design value when the compressor inlet temperature is raised by 13 °C relative to the design condition of 42 °C, which implies that the capacity of the thermal storage reduces by 25%. The main focus of this work is to investigate the off-design performance of a sCO 2 recompression cycle under variable ambient temperature, molten-salt inlet temperature and molten-salt flow rate. Multi-objective optimisation is carried-out in off-design conditions using an in-house code to explore the optimal operational strategies and the Pareto fronts were compared. Since the power cycle can either be operated in maximum power mode or maximum efficiency mode, this study compares these two operational strategies based on their annual performance. Results indicate that the capacity factor of the concentrated solar power can be increased by 10.8% when operating in maximum power mode whilst the number of start-ups is reduced by about 50% when operating in maximum efficiency mode. [ABSTRACT FROM AUTHOR]

• Six retrofitted SE-SMR processes are simulated and investigated. • A sensitivity analysis and competitiveness study are conducted. • The results offer flexible options for blue H 2 production scale up. • The integration of SE-SMR with PSA and CLC can achieve CO 2 -free, pure H 2 production. Clean and carbon-free hydrogen production is expected to play a vital role in future global energy transitions. In this work, six process arrangements for sorption enhanced steam methane reforming (SE-SMR) are proposed for blue H 2 production: 1) SE-SMR with an air fired calciner, 2) SE-SMR with a Pressure Swing Adsorption (PSA) unit, 3) SE-SMR thermally coupled with Chemical-Looping Combustion (CLC), 4) SE-SMR+PSA+CLC, 5) SE-SMR+PSA with an oxy-fired calciner, 6) SE-SMR+PSA with an indirect H 2 -fired calciner. The proposed process models with rigorous heat exchanger network design were simulated in Aspen Plus to understand the thermodynamic limitations in achieving the maximum CH 4 conversion, H 2 purity, CO 2 capture efficiency, cold gas efficiency and net operating efficiency. A sensitivity study was also performed for changes in the reformer temperature, pressure, and steam to carbon (S/C) ratio to explore the optimal operating space for each case. The SE-SMR+PSA+H 2 recycle process (Case 6) can achieve a maximum of 94.2% carbon capture with a trade-off in cold gas efficiency (51.3%), while a near 100% carbon capture with the maximum net efficiency of up to 76.3% is realisable by integrating CLC and PSA (Case 4) at 25 bar. Integration of oxy-fuel combustion lowers the net efficiency by 2.7% points due to the need for an air separation unit. In addition, the SE-SMR with the PSA_process can be designed as a self-sustaining process without any additional fuel required to meet the process heat utility when the S/C ratio is ~3–3.5. [ABSTRACT FROM AUTHOR]