• Energy Research

The world has faced many natural and man-made disasters in the past few years, resulting in millions of people living in temporary camps across the globe. The energy and clean water needs of the relief operators in such emergency situations are primarily satisfied by diesel engine based generators and importing clean water to the site, in certain cases even for several years after the emergency. This approach results in problems such as low security of supply and high costs. Especially targeting the prolonged displacement situations, this paper presents an alternative solution – the Energy and Water Emergency Module. The proposed solution aims towards reducing the dependency on fossil fuel in prolonged emergency situations to a minimum while including local energy sources in the energy supply in a flexible and reliable way. The proposed module is built in a standard 20 ft container, and encompasses hybrid generation from solar, wind and biomass, with the possibility of using fossil sources too thanks to a dual fuel gas engine. The module can work both in grid connected and stand-alone mode. In addition the module includes a water purification unit to meet the water needs of displaced population. A demonstration unit was assembled at the Royal Institute of Technology in Stockholm during the year 2012 as a ‘concept proof’, and is now being tested and optimized for future deployment on the field. Preliminary testing and modelling shows that the proposed solution can reliably support emergency situations, and is already cost competitive with the current water and energy supply solutions for emergency situations.

Energy system modeling offers helpful insights for exploring the potential use of renewable energy technologies in various applications. Different software tools are extensively used to model and design the renewable energy systems having different features. The choice of software tools used is highly dependent on the specific objective of the respective study. Among the software tools used, HOMER and RETScreen are two most popular modeling software used for designing renewable energy systems. In this paper, a modeling framework utilizing HOMER and RETScreen has been proposed for assessing renewable energy systems focusing on power systems providing electricity. HOMER has been employed to obtain the optimization of energy system components, cost and electricity share for the system. The results from HOMER were subsequently used as input in RETScreen along with other appropriate inputs for detailed project analysis with energy scenario for the systems. As a case study, this framework has been utilized for assessing Solar PV-Diesel energy system and Wind-Diesel energy system in Kutubdia Island, Bangladesh. This modeling framework employing unique features of two different popular software tools, HOMER and RETScreen, can be beneficial for the researchers and policy makers to better assess renewable energy systems utilizing techno-economic optimization with energy analysis.

The thermodynamic performance of a two-stage vapor compression cascade refrigeration system using hydrocarbon refrigerants is studied extensively in this study. The selection of hydrocarbon refrigerants for the cascade refrigeration system is conducted based on the molecular weight, freezing point, vaporization, density, global warming potential and ozone depletion potential. In the lower temperature circuit, Trans-2-butane (T2BUTENE) is utilized while Toluene (toluene), Cyclopentane (CYCLOPEN) and Cis-2-butane (C2BUTENE) are used on the higher temperature circuit. The performance of the system is evaluated considering three major operating temperature such as evaporator temperature, condensation temperature of lower temperature circuit (LTC), and condensation temperature of higher temperature circuit (HTC). Furthermore, comparisons between the presented work and the previous established work are conducted to show the improved performance of cascade refrigeration utilizing the hydrocarbon refrigerants. The results from the simulations suggest that highest COP and exergy efficiency is achieved when Trans-2-butane is employed in lower temperature circuit while Toluene is implemented on the higher temperature circuit. The results also suggest that the highest exergy destruction occurs at the condenser and the lowest can occur either at the lower circuit expansion valve or the evaporator for different refrigerant pairs. In addition, utilizing hydrocarbon refrigerants on cascade refrigeration systems can achieve a minimum 7.21 % higher COP than the recently employed refrigerants in previously established published works.

In 2019–2020, Bangladesh imported 5.2 million metric tonnes of petroleum products, worth 2.5 billion USD, and 50% of the imports were consumed by the transportation sector. Having limited natural oil reserves and being heavily dependent on oil imports, the country is vulnerable to shocks in the international oil market, which can jeopardize its consistent economic growth. The Government announced a 5% blending of bioethanol with gasoline in 2017, with broken rice, maize, and molasses as the feedstocks, but sourcing biofuel from food crops can hamper the country’s food security. This study explores second and third generation feedstocks e.g., organic plants, seeds, agricultural residues, and waste animal fat or skin that can be collected and processed for the extraction of biofuels. Technical potential of biofuel from the feedstocks is analysed which shows that Bangladesh has a potential to extract 44.4 million metric tonnes of bioethanol in a year from agricultural residues with rice residue having the highest potential (71%). Ground nut and rubber seeds can be major feedstocks for biodiesel production having a potential of 61,000 and 42,000 metric tonnes per year, respectively. Waste chicken skin can be another promising feedstock for the extraction of biodiesel. Biofuels extracted from these non-edible feedstocks and blended with existing transport fuels can lessen Bangladesh’s import bills through a sustainable, environmentally friendly manner.

We present all-solution processed, indium tin oxide-free organic solar cells on mechanically flexible polyethylene terephthalate (PET) substrates with power conversion efficiencies up to 4.8%. The mechanical properties of the devices are dictated by the electrodes from either metal-organic silver inks or a combination of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) and silver nanowires. Both electrodes can sustain high tensile strains. The influence of mechanical strain on the solar cell performance was experimentally studied in situ by measuring the J–V curves of elongated samples under illumination. At a strain of 14%, we still observed 90% of the initial device power output. At higher strain, crack formation within the electrodes was identified as the origin for device failure.

This paper describes the design and implementation of an energy efficient solar tracking system from a normal mechanical single axis to a hybrid dual axis. For optimizing the solar tracking mechanism electromechanical systems were evolved through implementation of different evolutional algorithms and methodologies. To present the tracker, a hybrid dual-axis solar tracking system is designed, built, and tested based on both the solar map and light sensor based continuous tracking mechanism. These light sensors also compare the darkness and cloudy and sunny conditions assisting daily tracking. The designed tracker can track sun’s apparent position at different months and seasons; thereby the electrical controlling device requires a real time clock device for guiding the tracking system in seeking solar position for the seasonal motion. So the combination of both of these tracking mechanisms made the designed tracker a hybrid one. The power gain and system power consumption are compared with a static and continuous dual axis solar tracking system. It is found that power gain of hybrid dual axis solar tracking system is almost equal to continuous dual axis solar tracking system, whereas the power saved in system operation by the hybrid tracker is 44.44% compared to the continuous tracking system.

This work presents a detailed thermodynamic analysis of a triple cascade vapor refrigeration system (TCRS) utilizing hydrocarbon refrigerants for ultra-low temperature application. Different hydrocarbon refrigerants pairs are used in different circuits (High temperature circuit HTC, Mid temperature circuit MTC, and Low temperature circuit LTC) to obtain the most suitable refrigerant combination by mathematical modeling of the system. The design and operating parameters considered in this study include (1) evaporator temperature (2) LTC condensation temperature (3) MTC condensation temperature. A thermodynamic analysis consisting of energy and exergy analysis were employed in terms of operating conditions to obtain COP, total compressor work, exergy efficiency, total exergy destruction, mass flow rate and discharge temperatures of compressors. Furthermore, an analysis on component exergy destruction was conducted to show the possibilities of improvement of TCRS utilizing the hydrocarbon refrigerants. The results suggest that at different evaporator temperatures different hydrocarbon refrigerants on TCRS give higher COP and exergy efficiency. The highest COP and exergy efficiency at −100 °C evaporator temperature was calculated to be 0.5931 and 54.446 %, respectively. This study also suggests that hydrocarbon refrigerants can be used in ultra-low temperature applications without compromising the thermodynamic performance of the refrigeration system.

In this experimental study, a series of extensive investigation have been performed to evaluate the possibility of production of biodiesel from local and marine sourced micro-algae. Authentic empirical information on the production of biodiesel from different species of microalgae has been demonstrated. Primarily, two different species of microalgae have been collected, isolated and have been cultivated in batch using the Bold’s Basal Medium (BBM) and harvested properly. Production of dry mass from a small scale batch medium has shown a satisfying rate which can be industrialized. Comparative growth rate of these species have been studied by OD method using Spectrophotometer. Biodiesel have been extracted from the dry biomass using Soxhlet extraction method. The properties of biodiesel are being explored and the results of these experiments have been depicted in lucid and cognitive interpretations. Also the contemporary context of biodiesel and the possibilities of microalgae in mitigating the forthcoming global energy crisis have been composed.