Journal of Energy Sustainability And Economic

Hydraulic fracturing stimulation is a common practice in petroleum industry.
The last two decades have witnessed great focusing on this process especially
in North America and more or less attention in the European and Middle East
oil fields. The process typically aims to increase the production recovery from
oil and gas that can’t be produced by conventional techniques. It applies
several hydraulic fractures along the horizontal wellbore that propagate to
different zones in the formation. The success of fracturing process is controlled
by several parameters. Fracture length, height and conductivity are the three
parameters that influence these successes. Proppant Number, defined as the
fracture volume to the reservoir volume, was proposed to judge the fracturing
process performance. Proppant Number might be expressed by fracture
conductivity and the ratio of the fracture length to reservoir width or the
horizontal penetration. A new Proppant Number for multiple hydraulic
fractures intersecting horizontal wellbore is presented in this paper. This
number is determined from the volume of specific fracture and the volume of
the drainage area surrounding the fracture. The new Proppant Number and the
vertical penetration ratio, the ratio of the fracture height to the formation
height, are two critical parameters affecting the productivity index of fractured
formation. A new model for the productivity index of finite reservoirs having
multiple hydraulic fractures has been introduced. This model reflects the
effects of the boundary dominated flow. This paper shows that the productivity
index increases with the increasing of Proppant Number and penetration ratio.
The productivity index increases significantly for the increasing of Proppant
Number when the number of fractures is small and slightly for large number of
fractures. The change in productivity index with the penetration ratio can be
noticed in short fracture lengths for large number of fractures and long
fractures for small number of fractures.

Nanotechnology has emerged as a promising approach to improve oil recovery
by altering rock–fluid interactions and reducing interfacial resistance. This
study investigates the effects of aluminum oxide (Al₂O₃) and titanium dioxide
(TiO₂) nanoparticles on two critical parameters: wettability alteration and
interfacial tension (IFT) reduction. Al₂O₃ nanoparticles were synthesized in the
laboratory using the precipitation method, while commercial TiO₂
nanoparticles were employed for comparison. Nanofluids with varying
concentrations were prepared and tested under controlled laboratory
conditions, with performance evaluated over different exposure times. The
results demonstrate that both Al₂O₃ and TiO₂ nanofluids effectively shifted
rock surfaces toward more water-wet conditions, enhancing their potential for
improved oil displacement. Al₂O₃ nanofluids showed optimal wettability
alteration at 400 ppm after 24 hours, although efficiency declined at higher
concentrations (1000 ppm) due to nanoparticle agglomeration. TiO₂ nanofluids
achieved optimal wettability improvement at 800 ppm after 24 hours and
displayed greater consistency across concentrations. In terms of IFT, both
nanoparticles reduced interfacial tension significantly, with TiO₂ achieving the
lowest value of 15.826 mN/m at 1000 ppm. Overall, TiO₂ nanofluids exhibited
more stable and effective behavior, highlighting their suitability for enhanced
oil recovery (EOR) applications.

Accurate prediction of photovoltaic (PV) panel surface temperature is essential
for evaluating thermal behaviour and minimizing efficiency losses, particularly
in hot and arid regions. This study presents an experimental and data-driven
approach for predicting PV surface temperature using locally measured
meteorological data from Nasiriyah City, southern Iraq. Field measurements
were conducted over five consecutive days in early July under real outdoor
conditions. The PV surface temperature was measured directly using
thermocouples fixed on the front surface of the panels, while solar irradiance
and ambient temperature were recorded using a solar irradiance meter and a
data logger.
The experimentally measured dataset was used to develop and evaluate three
regression-based machine learning models: Linear Regression, Random Forest,
and Gradient Boosting. A time-based validation strategy was adopted to reflect
realistic operating conditions, and model performance was assessed using the
coefficient of determination (R²) and mean absolute error (MAE). The results
showed that Linear Regression achieved the highest prediction accuracy, with
an R² value of 0.9999 and an MAE of 0.028 °C, indicating a strong linear
dependency between PV surface temperature and the selected meteorological
variables. Although Random Forest and Gradient Boosting models also
demonstrated good predictive capability, their higher error values suggest that
increased model complexity did not improve performance for the investigated
thermal regime.
The findings confirm that PV thermal behavior under steady outdoor
conditions is predominantly governed by linear heat transfer mechanisms.
Accordingly, simple and physics-consistent models can provide reliable and
efficient temperature prediction for PV systems operating in hot-climate
environments.

This paper compares Flat Plate Collector and Evacuated Tube Collector: their
thermal performance, cooling capacity, cost and applicability as a tent in a
warm climate. Case studies of two field installations in Iraq. In August 2022,
there was a field installation that used Flat Plate Collector with evaporative
cooling in Anbar. In August 2025, a field installation of Evacuated Tube
Collector was completed at Nasiriya with absorption cooling. In a site in
Anbar, the Flat Plate Collector system was able to successfully lower the inner
tent temperatures by 6–8 °C, Record outlet water temperatures of 40–65, and
thermal efficiency of about 45%. Evacuated Tube Collector sys. in Nasiriya
matched an average efficiency of 62% and generated greater outlet
temperatures of 55-90 °C (average 71 °C), which facilitated. Due to the
Evacuated Tube Collector having a higher output temperature and a stable
efficiency under strong solar radiation, they are suitable for the cooling based
on absorption in long lasting or semi-permanent camps. The Flat Plate
Collector offer an easy and inexpensive solution that is more appropriate for
faster deployment in humanitarian situations where evaporative cooling can.

High temperatures in electric motors are a major cause of reduced efficiency
and shortened lifespan. To mitigate this problem, an earth air heat exchanger
can be used as an effective cooling system. This research investigates
improving the thermal performance of electric motors by analyzing the effect
of pipe length. Five pipe lengths (10 m, 30 m, 50 m, 70 m, and 90 m) and three
inlet temperatures (30°C, 40 °C, and 50 °C) were selected, with a constant
mass flow rate of 0.6 kg/s and a constant diameter of 6 in, to determine cooling
efficiency. The results showed that rising tube length led to a significant
improvement in cooling, with the heat exchanger exit temperature decreasing
more at longer lengths. This is attributed to the larger surface area for heat
transfer. Larger lengths are associated with higher pressure differentials and
greater pumping capacity. Despite this, the longest length performed best,
achieving the highest cooling efficiency, with a reduction in motor temperature
of approximately 4.75%, 7. 33%, 8. 28%, 8.60%, and 11.21% for pipe lengths
of 10 m, 30 m, 50 m, 70 m, and 90 m, respectively. This means that the greater
the length, the greater the drop in temperature, resulting in higher system
efficiency.

This research investigates the impact of system design on energy efficiency in
variable refrigerant flow air conditioning systems. The variable refrigerant
flow systems are recognized for their precise temperature control and energy
savings potential across residential, commercial, and industrial buildings. The
project compares the efficiency of various variable refrigerant flow
configurations with conventional systems, proposing optimization methods.
Using comparative analysis, virtual simulations (Energy Plus and TRNSYS),
and real-world data from monitored buildings, energy usage, air quality, and
other parameters are assessed. The study aims to demonstrate that optimized
designs can significantly reduce energy consumption, providing practical
guidelines for system design and placement. Targeted at builders, the research
promotes environmentally friendly building practices.