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Abstract Reaching universal access to electricity by 2030 requires a massive deployment of mini-grids in rural areas of developing countries. Among the many challenges hindering this process, there are the high uncertainties in assessing demand patterns in rural communities, the costs of field survey campaigns, and the absence of ample and reliable datasets coming from existing projects. This paper tries to address these issues by presenting and discussing a database of load profiles from sixty-one off-grid mini-grids from developing countries worldwide, gathered from the literature, private developers and fieldworks, and reported with technical, socio-economic and geographical characterization factors. A clustering procedure led to the identification of five archetypal load profile clusters, which are presented and analyzed together with their load duration curves. Subsequently, the distribution among the clusters of the various characterization factors selected is studied. The proposed approach allows to widen the range of load profiles usually considered, and to seek correlations between the load profile shapes, the peak power and average energy consumption per connection, the number of customers, the age of measurement, geographical position, operator model, type of tariff and generation technologies present. This work establishes a first step in the creation of a shared database for load profiles of rural mini-grids, helping to overcome the lack of available data and difficulties of demand assessment, proposing original insights for researchers to understand load patterns, and contributing to reduce risks and uncertainties for mini-grid developers.

Lipid productivity of microalgae depends considerably on the method of its cultivation. In the present study, a two-stage culture strategy was conducted to cultivate Chlorella vulgaris to enhance lipid productivity. In the first stage, C. vulgaris was grown in the synthetic medium to obtain maximum biomass concentration. Wastewater is used as a medium for growing microalgae to have commercial and environmental aptitudes for biomass production. The nutrient removal efficiencies were 80.5% (COD), 70% (TN), and 78% (TP). In the second stage, the synergistic effects of nitrogen and NaCl concentration on the lipid productivity was investigated by response surface methodology (RSM) for 2 days. The optimum conditions for relatively high lipid productivity (up to 80 mg L−1 day−1) were 2.6 mg L−1 of nitrogen, 6.3 g L−1 of NaCl, and 4.9 g L−1 of biomass concentration. The value which was predicted by model was in good agreement with the experimental value, as it was determined by the validation experiments. Saturated fatty acid composition was increased by 27.3% under optimized medium compared with synthetic medium, which is very suitable for biodiesel production. According to the above results, it is concluded that the combination of multiple stress conditions can lead to a cost-effective technology of microalgae lipid production.

Anode with good electrocatalytic capabilities is more specifically required to reduce the ohimic losses during microbial fuel cell (MFC) operation. Highly conductive polymers viz., Polyaniline (PANi) and Polyaniline/Carbon nanotube (PANi/CNT) composite were prepared by in situ oxidative chemical polymerization method. Anodes were fabricated independently by coating PANi and CNT/PANi composites on the surface of SSM. The fabricated electrodes were evaluated as anode against stainless steel mess (SSM) as cathode during MFC operation. Maximum bioelectricity generation was observed in SSM-PANi/CNT-anode with power density of 48 mW/m2 and COD removal efficiency of 80% compared with SSM-PANi-anode (38 mW/m2; 65%) and SSM-anode (28 mW/m2; 58%). Bioelectrochemical characterization of the electrode materials using cyclic voltammetry and electrochemical impedance spectroscopy showed high electrocatalytic activity of PANi/CNT composite electrode. The study concluded the efficiency of PANi/CNT composite electrodes as bioanode in operation of MFCs towards achieving increased bioelectricity production along with wastewater treatment.

A promising route to transition wastewater treatment facilities (WWTFs) from energy-consuming to net energy-positive is to retrofit existing facilities with process modifications, residual biosolid upcycling, and effluent thermal energy recovery. This study assesses the economics and life cycle environmental impacts of three proposed retrofits of WWTFs that consider thermochemical conversion technologies, namely, hydrothermal liquefaction, slow pyrolysis, and fast pyrolysis, along with advanced bioreactors. The results are in turn compared to the reference design, showing the retrofitting design with hydrothermal liquefaction, and an up-flow anaerobic sludge blanket has the highest net present value (NPV) of $177.36MM over a 20-year plant lifetime despite 15% higher annual production costs than the reference design. According to the ReCiPe method, chlorination is identified as the major contributor for most impact categories in all cases. There are several uncertainties embedded in the techno-economic analysis and life cycle assessment, including the discount rate, capital investment, sewer rate, and prices of main products; among which, the price of biochar presents the widest variation from $50 to $1900/t. Sensitivity analyses reveal that the variation of discount rates causes the most significant changes in NPVs. The impact of the biochar price is more pronounced in the slow pyrolysis-based pathway compared to the fast pyrolysis since biochar is the main product of slow pyrolysis.

AbstractSlaughterhouses generate highly polluted effluents, and if not treated before discharge can cause major adverse environmental and public health impacts. Treatment of this waste by anaerobic digestion can reduce those impacts while producing a potentially valuable source of energy. The purpose of this study was to investigate this process efficiency under pilot operating conditions for a more accurate scaling up. Blood waste from a slaughterhouse was treated in a pilot‐scale digester of 30 dm3 total volume under mesophilic temperature conditions. Operating parameters such as pH, alkalinity, organic loading, volatile fatty acids, biogas composition, total and volatile solids were monitored in order to study the behavior of the fermentation process. The results show that no significant inhibition were caused by the accumulation of volatile fatty acids, due to the high buffering capacity of treated sludge. An efficient reduction of organic matter was obtained with a COD decrease of about 67% within 40 days of fermentation. The biogas produced was of a good quality with high CH4 yields (above 70%) and low CO2 yields, corresponding to a biomethane potential of 225.9 dm3 CH4/kg TVS. Logistic model described accurately the methane production kinetic and enables an easy process scaling up for industrial applications.

Abstract A consideration of second-law analysis has been extended from the heat exchanger network to an overall energy balance of a chemical process. This enables the simultaneous integration of all kinds of energy-active apparatus (e.g. reactors, compressors, turbines, boilers, refrigerators, coolers, heaters) and hot feeds or effluents into a process flowsheet. The apparatus and the feeds or effluents together represent a utility exchanger network (UEN), process streams are utilized by several types of energy (utilities) that are of a chemical, mechanical, electrical, transmissible, radiative, or heat flow origin. Inherent and avoidable utilities are distinguished. An action of each utility on the enthalpy change of the process stream is represented in a temperature—enthalpy diagram by the corresponding utility stream. Hot utility streams are composed into a hot composite curve (UCC). It sums up the energy inflows and energy production of the system, called energy donors. On the other hand, cold utility streams are composed into a cold UCC that comprises energy outflows and energy consumption (energy acceptors). Process streams are excluded in this step. By matching both UCCs the method enables the direct targeting of an economical overall utility system through is structural and parametric modifications. Targeting is facilitated by using general rules for appropriate integration of energy donors and energy acceptors relative to the utility pinch temperature. At the same time, the improved energy system changes the dynamical performances; the control configuration must be adopted to the new structure of the total system. The method is based on a detailed thermodynamic analysis of process units and is followed by an optimal thermodynamic synthesis of the total system. The final detailed parametrical optimization is similar to the classic pinch analysis. It deals with process streams and brings additional savings. The whole procedure has been tested on an existing chemical process and its effectiveness has been proved.

AbstractRemittances to the Philippines constitute a prominent part of its economy. However, remittances' effects on its environment have not been researched. In this regard, this research examines the direct and indirect impacts of remittance inflows on the Philippines' environmental sustainability for the 1977–2016 period by proposing a multivariate model, and by utilising the augmented ARDL and VECM methods to estimate this model. Our findings indicate that remittance inflows threaten environmental sustainability in the long‐run both directly and indirectly through boosting income and energy (oil) consumption. The results additionally imply that income and energy consumption also increase the ecological footprint of the Philippines in the long‐run. However, economic globalisation's long‐run impact is insignificant, yet its short‐run impact is significantly negative on the country's level of environmental degradation. Additionally, the findings reveal that the feedback hypothesis is valid between income and energy consumption in the long‐run, but the neutrality hypothesis is valid in the short‐run. This research's findings reveal that remittance inflows' impact on the environment is significant, and can occur through direct and various indirect channels, therefore, these inflows should be an integral part of sustainability policies in the Philippines, as ignoring them could cause further environmental decline.

Abstract The residential sector accounts for most of energy-consumption in developing countries in the form of traditional energy. The use of commercial energy is nominal and confined mostly to urban areas where fuelwood is already monetized. A model, based on an end-use/process analysis approach, is developed on a spreadsheet, which is capable of simulating scenarios to address issues of increasing traditional energy-demand caused by population growth, sustainable supply capacity of the existing energy resources, potential for development of new and renewable energy resources, technology. This paper is divided into two parts: general energy issues and the modelling approach, and the application of this approach to Nepal in the context of fuelwood-supply sustainability.

A clear path toward enhanced use of abundant domestic coal resources was established by the U.S. government and industry in the 1970s, but more recently that path has become less traveled, overgrown with the underbrush of environmental rules, cheap natural gas, renewable energy mandates, and economic downturns. As we look ahead, taking the path recently less traveled may make all the difference to our nation's future energy security.