Water scarcity and declining hydraulic performance of water supply pipe networks have increased the difficulty of providing

reliable water services. Greywater reuse represents a potential approach to alleviating these challenges. This study evaluates

the effects of greywater reuse on the hydraulic performance and reliability of a water supply pipe network. Three greywater

reuse scenarios are considered: no reuse, satellite reuse, and on-site reuse, each examined for two water supply configurations,

with and without roof tanks. Hydraulic performance is assessed using a case study network modelled in WaterGEMS.

The results indicate that on-site and satellite greywater reuse increase pressure head by approximately 18% and 20%, respectively,

under peak demand conditions. However, greywater reuse also leads to reduced flow velocities, with values below 0.5 m/s

in certain pipes at peak demand, increasing the potential for sediment deposition. Reliability analysis under critical pipe failure

conditions demonstrates that greywater reuse substantially improves network resilience. In addition, fourteen combined

demand reduction and greywater reuse scenarios are analysed, showing that integrated strategies can reduce overall potable

water demand by up to 42.8%.

Managing large-scale gatherings, such as global festivals, sporting events, and religious congregations, presents substantial challenges in ensuring crowd safety and control. Innovative frameworks are essential to address these complexities effectively. The Integrated Intelligent Crowd Control and Management (IICCM) framework combines cutting-edge technologies, including Computer Vision (CV), Artificial Intelligence (AI), and the Internet of Things (IoT), to enhance participant safety and optimize crowd management. CV enables precise real time identification and tracking, AI analyzes crowd behavior to anticipate risks, and IoT gathers environmental data to improve crowd flow, alleviate congestion, and provide timely assistance. Additionally, the framework facilitates emergency evacuation planning by modeling crowd dynamics and identifying safe, efficient escape routes. Although suitable for diverse events, the Hajj pilgrimage—a uniquely large and dynamic annual gathering—provides a rigorous test case for the IICCM framework. Managing millions of participants from varied cultural and linguistic backgrounds highlights the system’s adaptability and robustness. By effectively addressing Hajj specific challenges, the IICCM framework demonstrates its scalability and applicability to other large-scale events. This research offers valuable insights for decision-makers seeking to implement advanced crowd management technologies.

Theoretical work for concentrated solar-operated green hydrogen production system using compound parabolic
concentrator (CPC) integrated with solar photovoltaic (PV) cells driving proton membrane electrolysis (PME)
was developed, analysed, and evaluated under winter and summer conditions. Mathematical models for the
system components, including the CPC-PV integrated unit and the electrolyzer, were developed and solved. Key
system performance parameters were also evaluated. The system of equations was solved using MATLAB. Results
of the mathematical model show that for 1 m2 of the PV panel, the hydrogen production flowrate reaches a peak
on 0.0175 kg/h in summer and 0.0144 kg/h in winter, while the CPC-PV system power output can reach up to
607 W in summer and 590 W in winter. The PV efficiency in the CPC-PV system increases to about 14.75 % in
both seasons. Additionally, the overall system shows a summer and winter efficiency of nearly 13 % with a slight
variation between both seasons. The minimum achieved cost of hydrogen production of the system during
summer and winter is $0.17/kg and $0.271/kg, respectively at concentration ratio of 5. The system shows
promising performance under operation of different concentration ratios provided by CPC-PV system, highlighting
the system ability to enhance the production of green hydrogen gas cost effectively.

Electric and hybrid electric vehicles are promising alternatives to tackle environmental impact and greenhouse
gas emissions associated with internal combustion engine vehicles. Electric vehicles have fueled the need for an
efficient energy storage system to provide high power output, maximum energy density, and rapid charging.
Lithium-ion batteries are a viable alternative as their high power density and energy capacity make them stand
out from their long lifespan and quick charging capabilities. However, thermal energy generated during charging
and discharging can cause safety concerns. In this regard, an experimental study was conducted to assess cooling
performance using four distinct phase-change-materials (PCM): PARA-Block, RT-54 HC, RT-44 HC and RT-35 HC
were tested in a cyclic test, which showed a reduction in the battery's maximum temperature to 59.6 
C, 50.9 ◦ C, 51.9  ◦C respectively, compared to 76.4  C with natural convection cooling. For further modification to
achieve the cell's optimum operating temperature and shape stabilized material, various weight percentages of
expanded graphite (EG) (3 %, 6 %, 12 %, 15 %) were added to obtain composite stable phase change material
(CPCM). The results showed that the battery's highest temperature decreased by almost 55 % by adding 12 % EG
to PCM RT 35 HC compared to natural cooling. In addition, the best conditions were applied for a four-battery
pack.

Passive cooling of photovoltaic systems has been demonstrated to enhance their electrical performance at costeffective
methods. Among passive mechanisms, evaporative cooling stands out, particularly when utilizing
water-saturated porous structures. This study explores the parametric analysis of a porous clay structure as an
evaporative cooler for building integrated photovoltaic (BIPV) systems. It examines key parameters such as water
saturation levels and meteorological conditions, including wind velocity and relative humidity, assessing their
influence on system’s cooling performance. A numerical heat and mass transport model, along with the evaporation
model based on energy balance principle were presented and solved for this purpose. Further, experimental
evaluation of material variations was conducted utilizing hollow porous clay and traditional hollow red
brick structures, concurrently validating the numerical model. The experimental results highlight significant
improvements, with a 6 % reduction in peak PV temperature observed when using a porous clay structure
compared to conventional red bricks. The parametric study further revealed a maximum 9.7 % reduction in peak
PV temperature at higher water saturation levels. Notably, PV electrical efficiency and output power showed
peak enhancements of 0.93 % and 1.6 %, respectively, when humidity levels were halved rather than doubled.
Additionally, doubling wind velocity led to a 1.13 % decrease in indoor room temperature compared to halved
velocity values, demonstrating the effectiveness of these parameters in optimizing building cooling and PV
performance. Moreover, water evaporation rates reached a maximum of 6.07 L/h.m
2 and a minimum of 2.4 L/h. m 2 when the wind velocity and humidity values were doubled. Moreover, the system attained its highest water consumption rate of 10.19 L/h.m 2 when wind velocity values were doubled. Hence, these findings offer essential insights, underscoring the considerable impact that different operational conditions have on the effectiveness of evaporative cooling systems.

Solar energy electricity generation with concentrated photovoltaic (CPV) panels delivering substantially higher
power output than non-concentrated panels. However, CPVs suffer from excessive heat accumulation and non-
uniform temperature distribution, both of which severely impact electrical efficiency and shorten the panels’
lifespan. This study explores the implementation of a passive evaporative cooling strategy coupled with heat pipe
to mitigate CPV temperature rise. To address this challenge, a novel dual-function mechanism is proposed,
enabling efficient CPV cooling while simultaneously capturing and condensing fresh water to minimize evaporative
cooling losses. The study evaluates the proposed water harvesting indirect cooling mechanism
(WH-ICM) against two alternative cooling strategies: the direct cooling mechanism (DCM),
where the evaporative structure is directly attached to the panel’s backside, and the indirect cooling mechanism
(ICM),b which incorporates a heat pipe. The findings revealed that the ICM attained the highest average PV temperature reduction of 45.2 C, representing a 45.3 % improvement over the conventional PV system. Meanwhile, the WH-ICM followed closely with a 42.3  C reduction, marking a 42.4 % enhancement. Furthermore, WH-ICM boosted the average PV output power by 36.8 % and improved average efficiency by 30 % compared to the standard PV system. It also harvested
2.87 kg/day.m ◦2 of water, with a consumption of 25.36 kg/day.m2, recovering around 11.3 % of the total water
used. Notably, integrating WH-ICM increased the system’s daily average overall efficiency to 19.43 %, reflecting
a 36.26 % improvement over the conventional PV system, and a 7.7 % and 3.1 % raise compared to the DCM and
ICM, respectively.

This study evaluates the performance of a new standalone integrated system for independent hydrogen production combining waste heat recovery (WHR) via thermoelectric generators, humidification-dehumidification
(HDH), and a proton exchange membrane (PEM) electrolyzer. The system’s behavior is analyzed at varying
steam inlet temperatures and qualities to identify the best configuration for power generation. A complete
mathematical model of the whole system unit is constructed, programmed inside Matlab, solved, and validated.
Four configurations are studied for the thermoelectric generator unit distributions [100 × 100], [50 × 200],
[25 × 400], and [12 × 833]. Configuration 4 (12 ×833 TEG arrangement) outperforms others, generating
36.88 kW at 160 ◦C and 0.97 steam inlet quality, a 130 % increase compared to 100 C. This configuration extracts 337 kW from steam, enabling a hydrogen production rate of 15.5 kg/day with PEM efficiency peaking 73.65 % (declining to 68.94 % at 160 ◦◦C due to overpotentials). The HDH unit is operating at a GOR of 1.892. The system efficiency increased from 4.45 % at 100 ◦C to 4.95 % at 160 C, driven by enhanced TEG power generation. Economic analysis reveals a levelized hydrogen cost (LCOH) of 2.22–2.22–2.96/kg, competitive with blue hydrogen markets. Net Present Value (NPV) analysis shows profitability at 3–5 $/kg hydrogen, with breakeven 10–20 years for 3 $/kg and 4–5 years for 5 $/kg. Excess water utilization in the PEM electrolyzer reaches near-zero at 160 ◦ C, contrasting with 55 % excess at 100 ◦◦C. Trade-offs between steam quality and hydrogen yield are quantified: increasing quality from 0.05 to 0.97 at 100 C raises hydrogen production by 0.45 % (6.97–7.01 kg/day), while higher temperatures prioritize power over electrolyzer efficiency.