Optimisation of stand-alone hybrid energy systems for power and thermal loads

Stand-alone hybrid energy systems are an attractive option for remote communities without a connection to a main power grid. However, the intermittent nature of solar and other renewable sources adversely affects the reliability with which these systems respond to load demands. Hybridisation, achieved by combining renewables with combustion-based supplementary prime movers, improves the ability to meet electric load requirements. In addition, the waste heat generated from backup Internal Combustion Engines or Micro Gas Turbines can be used to satisfy local heating and cooling loads. As a result, there is an expectation that the overall efficiency and Greenhouse Gas Emissions of stand-alone systems can be significantly improved through waste heat recovery. The aims of this PhD project are to identify how incremental increases to the hardware complexity of hybridised stand-alone energy systems affect their cost, efficiency, and CO2 footprint. The research analyses a range of systems, from those designed to meet only power requirements to others satisfying power and heating (Combined Heat and Power), or power plus both heating and cooling (Combined Cooling, Heating, and Power). The majority of methods used focus on MATLAB-based Genetic Algorithms (GAs). The modelling deployed finds the optimal selection of hardware configurations which satisfy single- or multi-objective functions (i.e. Cost of Energy, energy efficiency, and exergy efficiency). This is done in the context of highly dynamic meteorological (e.g. solar irradiation) and load data (i.e. electric, heating, and cooling). Results indicate that the type of supplementary prime movers (ICEs or MGT) and their minimum starting thresholds have insignificant effects on COE but have some effects on Renewable Penetration (RP), Life Cycle Emissions (LCE), CO2 emissions, and waste heat generation when the system is sized meeting electric load only. However, the transient start-up time of supplementary prime movers and temporal resolution have no significant effects on sizing optimisation. The type of Power Management Strategies (Following Electric Load-FEL, and Following Electric and Following Thermal Load- FEL/FTL) affect overall Combined Heating and Power (CHP) efficiency and meeting thermal demand through recovered heat for a system meeting electric and heating load with response to a specific load meeting reliability (Loss of Power Supply Probability-LPSP). However, the PMS has marginal effects on COE. The Electric to Thermal Load Ratio (ETLR) has no effects on COE for PV/Batt/ICE but strongly affects PV/Batt/MGT-based hybridised CHP systems. The higher thermal than the electric loads lead to higher efficiency and better environmental footprint. Results from this study also indicate that for a stand-alone hybridised system operating under FEL/FTL type PMS, the power only system has lower cost compared to the CHP and the Combined Cooling, Heating, and Power (CCHP) systems. This occurs at the expense of overall energy and exergy efficiencies. Additionally, the relative magnitude of heating and cooling loads have insignificant effects on COE for PV/Batt/ICE-based system configurations, however this substantially affects PV/Batt/MGT-based hybridised CCHP systems. Although there are no significant changes in the overall energy efficiency of CCHP systems in relation to variations to heating and cooling loads, systems with higher heating demand than cooling demand lead to better environmental benefits and renewable penetration at the cost of Duty Factor. Results also reveal that the choice of objective functions do not affect the system optimisation significantly

Changes in the electronic structure and properties of graphene induced by molecular charge-transfer

Interaction with electron donor and acceptor molecules such as aniline and nitrobenzene brings about marked changes in the Raman spectrum and the electronic structure of graphene, prepared by the exfoliation of graphitic oxide.Comment: 13 pages, 4 figure

Biomimetic and bio-derived composite phase change materials for thermal energy storage applications: A thorough analysis and future research directions

Phase change heat storage has gained a lot of interest lately due to its high energy storage density. However, during the phase shift process, Phase Change Materials (PCMs) experience issues such as low thermal conductivity, stability, leaking, and low energy-storing capacity. Materials that mimic or derive from nature can effectively offset the shortcomings attributed. This work presents a methodical overview of the synthesis, thermo-physical properties, comparison and Thermal Energy Storage (TES) applications of bio-derived and biomimetic composite PCMs (BD/BM-CPCMs). Several studies have observed increase in thermal conductivity up to 950–1250 % for BD/BM-CPCMs, as well as great thermal stability with no matrix leakage at an average temperature of 150–250 °C. These types of composites have a relative enthalpy efficiency of up to 98.1 % and can endure 200–1000 heating-cooling cycles on average. Additionally, enviro-economic aspects, numerical approaches to heat transfer during phase change and multivariate and multi-objective optimizations from a technical, financial and environmental standpoint using machine learning techniques with underlying scopes of BD/BM-CPCM are presented. It is necessary to fabricate adaptable BD/BM-CPCM for multifunctional energy harvesting and storage in future. With regard to the advancement in substance functionalism, it is necessary to show and research the use of bio-derived composite with innovative effects like versatility, light to thermal conversion, electro-thermal conversion, and anti-bacterial qualities in real-world systems

Prospects of Rice Husk Gasification for Power Generation in Bangladesh

Electricity is the basic requirement to promote socio-economic development. In recent years, Bangladesh is facing severe power crisis all over the country, but the rural areas are the most vulnerable. This acute electricity crisis along with the conventional fuel crunch is affecting every sector of the country and economy is being crippled. To reduce the dependency on fossil fuels, rice husk which are widely abundant agricultural waste from rice industry could play a vital role in this regards. Bangladesh is an agricultural country and produces huge quantity of rice every year. In the year 2011, the total rice production was around 50.63 million tones. Husk is the waste biomass produce during the rice processing, on average it accounts around 20% of the rice produced on weight basis (10.12 million tones). The potential of power generation from rice husk by gasification is around 310 MWe in Bangladesh. The power plant to be installed near the large rice mills `cluster area' in Dinajpur, Bogra, Naogaon, Chapainawabganj and Ishwardi with the surplus rice husk. This paper consolidates information from various studies on the availability of rice husk, its characterization and estimates possible power potential that can be realized

Modeling and performance investigation of novel inorganic Cs4CuSb2Cl12 nanocrystal perovskite solar cell using SCAPS-1D

For the next generation of photovoltaic devices, perovskite solar cells (PSCs) appear as a good choice because they are simple and convert energy to electricity very efficiently. Recent years have seen a great deal of interest in organic-inorganic lead halide perovskites due to their exceptional optoelectronic properties. Nonetheless, additional commercialization of the Pb element is still restricted by its inevitable toxicity. To address the instability and toxicity of the lead hybrid perovskite, it is imperative to produce entirely inorganic lead-free perovskite nanocrystals. Cs4CuSb2Cl12 offers promising qualities and strong stability against light, heat, and humidity to overcome these drawbacks. It possesses an efficient photo-generated carrier and good carrier mobility. In this study, a lead-free perovskite solar cell with the novel configuration of FTO/WS2/Cs4CuSb2Cl12/CuSbS2/Ni has been optimized using SCAPS-1D simulation software and investigates the potential of Cs4CuSb2Cl12 nanocrystal solar cell. The impact of different characteristics of charge transport materials on Cs4CuSb2Cl12 nanocrystal solar cells has been reported. Additionally, the study computationally optimizes the thickness of perovskite layer, doping concentration, defect density, and other input parameters to propose an effective PSC with power conversion efficiency of 23.10 %, Voc of 1.1675V, and FF of 83.33 %

Energy management and sizing of a stand-alone hybrid renewable energy system for community electricity, fresh water, and cooking gas demands of a remote island

Research into the off-grid hybrid energy system to provide reliable electricity to a remote community has extensively been done. However, simultaneous meeting electric, freshwater, and gas demands from the off-grid hybrid energy sources are very scarce in literature. Power- to-X (PtX) is gaining attention in recent days in the energy transition scenarios to generate green hydrogen, the primary product of the process as an energy carrier, which is deemed to replace conventional fuels to reach absolute carbon neutrality. In this study, renewable–based hybrid energy is developed to simultaneously meet the electricity, freshwater, and gas (cooking gas via methanation process) demands for a remote Island in Bangladesh. In this process, an energy management strategy has been developed to use the excess energy to generate both freshwater and the hydrogen, where hydrogen is then converted to natural gas via methanation process. The PV, wind turbine, diesel generator, battery, and fuel cell have been optimized using non-dominating sorting algorithm-II (NSGA-II) to offer reliable, cost-effective solutions of electricity, freshwater, and cooking gas for the end users. Results reported that the PV/WT/DG/Batt configuration has been found the most economic configuration with the lowest COE (0.1724 $/kWh) which is 9$/m3 and 3.978 $/m3, respectively

Experimental investigation on hydrogen-rich syngas production via gasification of common wood pellet in Bangladesh: Optimization, mathematical modeling, and techno-econo-environmental feasibility studies

Since hydrogen produces no emissions, there is increasing interest in its production throughout the world as the need for clean and sustainable energy grows. Bangladesh has an abundance of biomass, particularly wood pellets, which presents a huge opportunity for gasification to produce hydrogen. Gasification of mahogany (Swietenia mahagoni-SM) and mango (Mangifera indica-MI) wood is performed in a downdraft gasifier to evaluate the impact of particle size, equivalence ratio, and temperature on hydrogen gas composition and gasifier performance. Under the optimal conditions determined by central composite design-response surface methodology (CCD-RSM) optimization, gasification of SM and MI wood can greatly increase hydrogen yield and cold gas efficiency, offering a workable, environmentally friendly, and long-term solution to Bangladesh\u27s energy shortage and pollution problems. Through RSM analysis the best operating conditions for gasification of SM wood include a feed size of 22.5 mm, equivalence ratio of 0.34, and operating temperature of 1176 K, where a total yield of hydrogen 11.2% was obtained. In the case of MI wood gasification, the optimum condition was found at feed size 22.5 mm, equivalence ratio 0.34, and operating temperature of 1132.47 K, where a total yield of hydrogen 12.85% was obtained. The economic study provides an LCOE of 0.1116 $/kWh, the project payback period is determined to be 10.7 years. By reusing wood waste from nearby sawmills, this study helps to manage waste sustainably by lowering pollution levels and deforestation. It also highlights wider sustainability effects by assisting international initiatives to fight climate change and advance energy independence

Economic Evaluation of the PV Micro Utilities Installed by Grameen Shakti for Rural Electrification in Bangladesh

Sharing expensive technology can serve many users, even poor users. Grameen Shakti has developed a special programnamed PV micro utility to make it easier for those who cannot afford SHSs individually. Under this program, GrameenShakti allows people to share the cost and the subsequent benefit of using a SHS. In this study, operation and financialmechanism, analysis of cost of systems, tariff system, simple payback period, NPV and IRR of the micro utility systemshave been analyzed to show the financial viability of PV MU from the PV MU owner’s perspective. Results suggest thatthese systems have simple payback period of around 4-6 years. The NPV of systems varied from 27,000 BDT to 144,000BDT. The levelized electricity cost of PV MU systems is 70 BDT (~0.86 $)/kWh in Bangladesh. The owner has to spendonly 7.50 BDT/day but can earn at least 30-40 BDT per day, and up to 130-200 BDT/day.Keywords - Rural Electrification, Solar PV, Grameen Shakti, Bangladesh, Economic Evaluation