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Rapid population growth and increasing energy demand in developing countries are the key drivers behind rising concerns such as energy poverty and environmental degradation. Harnessing solar energy can help the developing countries inch closer to sustainable economic growth. This article presents the performance analysis of a solar water heating system based on an evacuated flat-plate collector (EFPC). EFPCs offer higher optical performance and lower thermal losses in comparison with conventional solar collectors. In this study, a multiparametric analysis provides the guidelines for the design and optimization of a novel low vacuum EFPC system under ambient conditions, for domestic hot water (DHW) applications. A small-scale solar thermal collector system based on a low vacuum (17.5–20 kPa) EFPC of a total area of 4.0 m2 is designed and installed. The system is coupled with a storage tank composed of the helical copper coil configuration inside the tank, which is used as a heat exchanger from a primary loop to a secondary loop. A series of real-time experiments are performed under ambient conditions from December to April. The thermal efficiency of the EFPCs reaches a maximum value of 73.2%, with the glycol–water mixture as a heat transfer fluid at an inlet temperature of 31.2 °C, when the ambient temperature is 15.3 °C, average irradiance is 679.2 Wm−2, and vacuum pressure is 20 kPa. For this duration, the exergy efficiency reaches a peak value of 16%. This EFPC system provides 100 liters of hot water at 57–69 °C per day for DHW consumption when the average ambient temperature is 24 °C. The overall results highlight the potential of EFPCs for hot water applications. Furthermore, an efficiently optimized EFPC system can also be used for space heating during the winter season.

With the increasing demand of clean and energy-efficient air conditioning systems, evaporative air cooling technique is gaining significant attention owing to less energy consumption and environmentally safe technology in comparison with conventional refrigerant-based air conditioners. In this study, commercial desiccant dehumidifier is coupled with experimentally developed direct evaporative cooling (DEC) system to first dehumidify the air and then pass it through DEC to achieve human thermal comfort level defined by ASHRAE standards. Under the climatic conditions of Islamabad, Pakistan, multiple experiments were carried out at different temperatures, flowrate, and relative humidity of air during November, when air temperature and relative humidity were in the range of 25–30 °C and 40–60%, respectively. To analyze the system performance under summer ambient conditions, indoor temperature was increased by 8–10 °C and relative humidity by 15–25% in laboratory. Experimental analysis showed that the system can provide human comfort level for a range of temperature 29–39.7 °C and relative humidity of 65–80% at flowrate of 180 m3/h. To achieve thermal comfort at higher humidity level, DEC is coupled with commercial desiccant dehumidifier. However, due to desiccant regeneration by an electric heater in the dehumidifier, the overall power consumption of the whole system increases up to 1.95 kW. Two well-known indices coefficient of performance (CoP) and energy efficiency ratio (EER) are used to analyze the system performance. Experimental analysis revealed that CoP decreases with the increasing specific humidity of air, decreasing ambient temperature, and flowrate.

Energy is a key parameter for a country's development. From recent decades Pakistan is facing energy crises due to the limitation of traditional energy resources. In Pakistan, natural gas, electricity, and coal are used for domestic hot water systems and industrial process heat. Due to climate change, traditional energy resources are declining, and energy demand is increasing. To support the developmental work, increasing population, and industries, Pakistan will need energy in an abundant amount to run the system on the proper track. To solve these problems, we just need to replace traditional energy resources with renewable energy. Solar thermal collectors are sources to complete the demand for hot water on small and large scales. This paper demonstrates an evacuated flat plate collector having an area of 4 m2 and working fluid water-glycol mixture inside the tubes circulates with different mass flow rates of 0.01 to 0.1 kg/s with the help of a pump. The vacuum is created inside the collector with the help of a vacuum pump and pressure maintained less than 1 bar. Program is generated in MATLAB and simulated under design conditions of the collector with input weather data collected from meteorological high precision equipment installed at US-PCASE, NUST Islamabad, Pakistan having a latitude of 33.64° N and longitude of 72.99° E. By evacuating the enclosure convective losses from plate to cover are drastically reduced, which in turn decreases overall heat loss coefficient from 7.50 to 4.60 W/m2K. absorber temperature is also increased due to reduction of convective losses, which in turn increases fluid outlet temperature by 7 to 9 °C and also increases the efficiency of the collector by 7 % as compared to non-evacuated flat plate collectors.

Rising concerns of environmental degradation and energy security particularly in developing countries like Pakistan has exhilarated the need for energy storage systems for efficient source utilization. Phase Change Material (PCM) based Thermal Energy Storage (TES) systems are used with air conditioning systems for thermal load management in buildings. The TES system discussed in this paper consists of a macro-encapsulated PCM Magnesium chloride hexahydrate (MCHH) in aluminum cylinders. The system is integrated with a domestic gas heater to capture extra energy dissipated by the gas heater, used to raise the room temperature to the thermal comfort level. A numerical model is developed in MATLAB based on the enthalpy method for the performance analysis and investigating the phase transition phenomenon of MCHH, followed by experimental validation. Different thermal performance indices of TES are investigated such as liquid fraction, energy, and exergy stored during the charging/discharging process. The model has predicted 42 kJ and 9 kJ of energy and exergy stored, respectively during the charging cycle, while experimentations showed 39.6 kJ and 6 kJ energy and exergy stored in the material, respectively. The deviation of 15% in energy and 33.33% in exergy from experimental results indicated that the actual phase transition is non-isothermal and the mathematical model does not include the factor to accommodate the actual melting phenomenon with changing thermophysical properties of PCM. This performance analysis is significant to design and optimize the PCM-based TES coupled with conventional heating sources.

In this study, the waste eggshell has been utilised to synthesise structure modified CaO using organic acids and employed for CO2 capture in the thermogravimetric analysis (TGA) based systems. Different characterisation techniques were used such as XRD, SEM/EDS, XRF, N2 sorption-desorption (BET) and TGA to investigate the suitability for CO2 adsorption. The modified CaO using organic acids showed high surface area, easy upgradation of pore structure makes the CaO a suitable sorbent for CO2 capturing as an economical sorbent. Three of the organic acid modified sorbent achieved the highest conversion and stability over a period of 20 cycles. Citric acid modified sorbent (CaO CA-10%) obtained a CO2 uptake of 0.38 g CO2/g sorbent (CaO conversion of 55%) that was highest among the acid used whereas in term of stability malic acid modified sorbent (CaO MA-10%) has the lowest average decay rate of 4.43 mg CO2/cycle as compared to various acids used in this work. It is concluded that modified surface structure by employment of organic acids lead to the reduction of sintering and led towards better sorbents performance towards CO2 capturing for multiple cycles.

Some of the recent challenges encountered in research and development of the solar photovoltaic (PV) industry include the decrease in electrical output efficiency of a conventional solar PV module due to the rise in its surface temperature. The main objective of this research work is to enhance and improve the electrical output efficiency of a common silicon-based solar PV module by lowering the operating temperature of the PV module, which was accomplished by attaching hollow rectangular aluminum tubes as a fin to the rear surface of the solar PV panel. The proposed geometrical configuration of tubes helped to increase the PV module heat transfer rate to the surrounding air by increasing the effective heat transfer area without increasing the overall weight of the PV module. In this experimental study, a comparative analysis has been presented for PV modules with fins and without fins. The results obtained from experiments demonstrated that the attached fins reduced the average temperature of the front and rear surfaces up to 8.97% and 8.41%, respectively. The cooling effect produced due to fins improved the open circuit voltage up to 12.97% and the electrical output efficiency up to 2.08%. Furthermore, the results are thoroughly compared with other published studies, which revealed that the proposed configuration is cost effective and structurally sound.

Calcium looping process is an important technology for high temperature CO2 scrubbing. Calcium based sorbent decays rapidly after cyclic reactions, hence enhanced cyclic stability of the sorbent should be developed. We studied three different refractories including Al, Mg and La based supports which were synthesized using the dry mixing, wet-mixing method and Sol Gel Combustion Synthesis (SGCS) methods, through which the dopants are completely mixed into CaO/CaCO3 particles. The sorbents were characterized by SEM/EDS and XRD. The carbonation conversion and cyclic stability of sorbents were tested by Thermo-Gravimetric Analyser (TGA) under similar conditions. TGA results demonstrated that marble-dust doped sorbents are able to achieve higher conversion than eggshell sorbents. Hence, further analysis was focused on marble-dust sorbents. SGCS exhibit much superior cyclic performance as compared to wet and dry method, however, wet method is effective due to the low cost less time consumption and scale up issues. This analysis demonstrated that marble-dust sorbents doped with Al i.e CaO:Al (90:10) maintained the best conversion (91 %) and stability over 20 reaction cycles in comparison with dopant ratio CaO: Al (80:20) i.e., 73 %. Similarly, Mg and La dopants showed best conversion and cyclic strength at the doping ratio of 90:10. Hence, conversion rate and cyclic stability is maximum for all the dopants Al, Mg and La with dopant ratio of 90:10 in comparison with ratios 80:20 and 70:30. Furthermore, among all the dopants, Al dopant gives highest conversion rate and cyclic stability.

Micro gas turbines (mGT) are emerging power sources for distributed generation facilities with promising features like environment friendliness, high fuel flexibility, cost effectiveness and efficient cogeneration of heat and power (CHP). However, curtailed heat demand during summers reduces the plant operating hours per year and negatively affects the overall economic feasibility of a CHP project. The micro Humid Air Turbine (mHAT) cycle is one of the novel cycles to increase the electrical efficiency of the gas turbine by utilizing the exhaust gas heat in periods of low heat demand, thus avoiding the system shutdown. However, the water injection system can introduce additional pressure losses in the mGT cycle, which may lead to compressor surge and it may also affect the recuperator performance in the long run due to corrosion. Hence, numerical simulation and diagnostic tools are essential for cycle optimization of mHAT and prediction of performance degradation. This work is focused on the real time application of the AE-T100 model for the mHAT system located at the Vrije Universiteit Brussel (VUB), which is based on the T100 mGT equipped with a spray saturation tower. The AE-T100 model is a steady-state simulation tool for mGT cycles, which has been developed within a collaboration between the University of Genova (Unige) and Ansaldo Energia, and has been successfully applied at the Ansaldo Enegia test rig (AE-T100) for the diagnostic purpose. For this study, the basic AE-T100 model has been modified to simulate the humidified cycle according to the VUB plant configuration. The modified AE-T100 model has been validated against the experimental data obtained from the mHAT unit at nominal and part load. Once the model was validated using real operating conditions, it has been used for monitoring the recuperator performance over large number of tests in dry mode, conducted over the past five years, as well as initial tests in wet mode, from the VUB-mHAT system. This work has proved the modeling capability of the AE-T100 tool to simulate the mHAT cycle with reasonable accuracy and first diagnostic application of the AE-T100 tool, in dry mode. However, the lack of data available at present in wet mode does not allow to provide a complete and robust diagnostics of this novel cycle under wet operation. Hence, this preliminary analysis will provide basis for more detail diagnostics of the mHAT cycle using AE-T100 tool, over a longer time period under wet operation, in future.

Integration of Thermal Energy Storage (TES) is one of the promising features of Concentrated Solar Power (CSP) technology which allows the Renewable Energy Sources (RES) to provide uninterrupted and dispatchable power supply, and thus facilitates the RES grid integration. Hybrid Solar Gas Turbine (HSGT) systems along with TES integration have gained great attention for the last decades. Numerical modelling and simulation tools are essential for the TES design optimization and analysis of its thermal behaviour during charging and discharging phases. This paper deals with the dynamic modelling and experimental validation of a TES at laboratory scale, which is part of the HSGT system. The TES is modelled with two different approaches: the CFD model using a commercial tool and a reduced-order model using the in-house transient simulation tool TRANSEO, which has been developed by Thermochemical Power Group (TPG) for the energy system dynamic analysis. The validation of both model results against the data obtained by the Authors through experimental investigation has highlighted that 2D discretization of the TES through the CFD model gives accurate representation of the thermal behaviour of the system, but it causes a significant computational expense. On the other side, 1D dynamic model reasonably predicts the time dependent thermal behaviour of TES, except some deviations from the experiments which are related to the simplified discretization scheme. However, due to its fast approach, the TRANSEO model can be effectively used to perform both TES initial design and sensitivity analysis, and also to develop or verify the control system at a later stage of HSGT system development.

Micro gas turbines (mGT) are emerging power sources for distributed generation facilities considering their environment friendliness, high fuel flexibility and efficient cogeneration of heat and power (CHP). Numerical simulation and diagnostic tools are essential for cycle optimization of mGT and prediction of performance degradation. This work is focused on fault diagnostics of T100 mGT through the application of AE-T100 model, a simulation tool, which has been developed within a collaboration between the University of Genoa (Unige) and Ansaldo Energia. This model has been developed for steady-state simulation of mGT in off-design conditions. Leveraging on previous efforts for model development, tuning, first phase of validation through Ansaldo Enegia test rig (AE-T100) and diagnostic application of the model, the present work deals with further utilization of the diagnostic capability of the model for mGT cycles. For this purpose, it was used in real operating conditions through the AE-T100 test rig for the diagnostic aim of some unexpected machine behavior. The model results indicated high deviation from the actual field data in terms of fuel flow and efficiency, and so justified the diagnostic capability of the AE-T100 tool. Afterwards, based on the experimental observation of some bypass leakage from the burner in the same test rig, AE-T100 model was applied to model such leakage through the variation of AS ratio, leakage from the recuperator outlet to the ambient, combustor pressure drop and turbine section modification, and carried out the sensitivity analysis of these parameters. Sensitivity analysis has verified that the accurate impact of this leakage on overall mGT performance cannot be modeled with the help of AE-T100 tool in its current capacity. Therefore, some other investigations like analysis of compressor maps must be carried out to explain such a performance deviation in case of leakage. Afterwards, the analysis of compressor maps resulted from the operating conditions of the test conducted on the same machine after leakage repair, has highlighted the change in compressor operating point and thus, more efficient compressor functioning, which results in higher net power. Hence, this analysis has provided a more comprehensible explanation of this leakage impact on the mGT performance.

Calcium looping is a widely used CO2 capture technology, where calcium oxide (CaO) is used as a sorbent. However, it has many drawbacks such as expensive raw material and reduction in sorbent capacity over multiple cycles. This study is aimed at developing economic as well as environment friendly sorbents for CO2 capturing. For this purpose, chicken eggshells were collected from household municipal waste as a CaO sorbent for CO2 capture. The eggshell sorbent was characterized using different techniques such as SEM-EDS, XRD and TGA. Three different organic acids were used to improve the conversion of eggshell sorbents i.e., lactic, oxalic and tartaric acid. The results showed that one out of three acids i.e., lactic acid (ES LA-10%) showed improved conversion and stability over a period of 20 cycles as compared to other acids. In terms of CaO conversion ES LA-10% displayed the maximum performance of 47.8% and had improved cyclic stability during 20 cycles. Hence, this study showed that modifying sorbent (eggshells) by using acid is a better sorbent in comparison with other natural and synthetic sorbent, therefore reducing waste and cost simultaneously.

The growing environmental impacts and dwindling supply of conventional fuels have led to the development of more efficient and clean energy systems. Micro gas turbines (mGT) have emerged as energy conversion technology, which offer promising features like high fuel flexibility, low emissions level, and efficient cogeneration of heat and power (CHP). Numerical simulation is a vital tool to predict the off-design performance of mGT cycles, and it also helps in cycle optimization. Starting from a model available at Ansaldo Energia, for steady state simulation of mGT T100 cycles based on user requirements, within the cooperation between University of Genova (Unige) and Ansaldo Energia, a new more comprehensive simulation tool has been developed through the incorporation of additional components, features, and involving a more detailed mathematical approach. The most important upgrades involved a number of different air path flows and the power electronics, which takes into account the power consumption from auxiliary components as well as the generator and inverter efficiencies. Once the model has been verified against the existing tools, it was used in real operating conditions at the Ansaldo Energia test rig. The mGT performance has been assessed for different power levels, starting from 100 kW (nominal power) to 60 kW and then back to 100 kW, with 10 kW steps. The two tests at 100 kW operating conditions have been carried out with two different ambient temperatures: 20°C and 25°C, respectively. Data have been acquired under stable operating conditions, considering the recuperator cold outlet temperature as the stability indicator. Finally the new model AE-T100 has been used also for diagnosis of the whole mGT cycle. The model has been successfully applied to a special mGT equipped with an on-purpose damaged recuperator, identifying the causes of performance degradation.