Energy storage is nowadays recognised as a key element in modern energy supply chain. This is mainly because it can enhance grid stability, increase penetration of renewable energy resources, improve the efficiency of energy systems, conserve fossil energy resources and reduce environmental impact of energy generation. Although there are many energy storage technologies already reviewed in the literature, these technologies are currently at different levels of technological maturity with a few already proven for commercial scale application. Most of the review papers in energy storage highlight these technologies in details, however; there remains limited information on the real life application of these technologies for energy storage purpose. This review paper aims to address this gap by providing a detailed analysis of real life application and performance of the different energy storage technologies. The paper discusses the concept of energy storage, the different technologies for the storage of energy with more emphasis on the storage of secondary forms of energy (electricity and heat) as well as a detailed analysis of various energy storage projects all over the world. In the final part of this paper, some of the challenges hindering the commercial deployment of energy storage technologies are also highlighted.
h i g h l i g h t sWe model two cryogenic air separation unit with compressor waste heat recovery. We compare the specific energy consumption of the models. We compare the overall energy consumption of the models. Compressor heat recovery improve the energy efficiency of the process. a b s t r a c tIn this paper, the potential of improving the energy efficiency of a conventional cryogenic air separation unit (ASU) was investigated through modelling and simulation using Aspen Plus ® v 8.1. It is achieved through converting the heat from the compressor effluent to electricity using organic Ranking cycle (ORC). Two different arrangements of combining compressor and waste heat recovery ORC system were compared with the conventional cryogenic ASU which was used as the benchmark. The benchmark is a conventional cryogenic ASU with 3 stages of compression which uses water for intercooling. In the first arrangement the water used as the cooling fluid of the intercooler/after cooler heat exchanger of a conventional cryogenic ASU process was replaced by R134a which also acts as the working fluid for the ORC system (C3WHR) while in the second arrangement, the 3 stages compressor of the conventional process was replaced with a single stage compressor with the same overall pressure ratio as the conventional process and the hot compressor effluent cooled with R134a which also acts as the working fluid of the ORC system (C1WHR).The simulation results based on a cryogenic ASU capable of processing 100 kg/s of atmospheric air at 30 C as feedstock show that the specific power consumption for the pure products which was 0.32 kWh/ kg, 0.37 kWh/kg and 17.35 kWh/kg for oxygen, nitrogen and argon respectively for the conventional cryogenic ASU process was reduced by the addition of the waste heat recovery ORC system. The C1WHR reduced the specific power consumption by an average of 0.2% across the aforementioned pure products while the C3WHR reduced it by an average of 11%. The net power consumption of the conventional cryogenic ASU which was 21826.19 kW was also found to be reduced by the same percentage.
In this paper, the IPSEpro Model of the Chena Geothermal ORC power plant had been developed and validated using the real data. The validated model was used to investigate the effect of variation in the geothermal source temperature on plant performance.The analysis showed that the variation of the geothermal source temperature affects the plant behaviour. Increase in the geothermal source temperature above the design point increases the working fluid flowrate, decreases the working fluid degree of superheat at the inlet of the turbine (evaporator exit), increases the plant net power output and reduces the efficiency while decrease in the geothermal source temperature lower than the design point increases the degree of superheat up to a certain maximum beyond which it starts to reduce. It also causes a decrease in the net power output and an increase in the plant efficiency.
Chrysophyllum albidium seed shell, an abundant, biodegradable and inexpensive natural resource was used as a precursor to bioadsorbent production for the removal of suspended and dissolved particles (SDP) from initially coagulated Brewery Effluent (BRE). Influence of key parameters such as contact time, bioadsorbent dose, pH and temperature were investigated using batch mode. The thermal behavior studies were evaluated using Thermogravimetric and Differential scanning calorimetric analyses. The morphological observations and functional groups of the bioadsorbents were determined using scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The adsorption equilibrium, thermodynamics and kinetic of SDP adsorption on H3PO4-treated shell and NH4Cl-treated shell were examined at specified temperatures. Equilibrium data sufficiently fitted the Langmuir isotherm model (R2 > 0.99; SSE < 0.09). The pseudo-second order kinetic model provided the best correlation (R2 > 0.99; SSE < 0.14) with the experimental data. The values of ΔG° and ΔH° indicated the spontaneous and endothermic nature of the process. This study demonstrated that C. albidium seed shell could be utilized as low cost, renewable, ecofriendly bioadsorbent for the uptake of SDP from BRE.
Background: The economics of producing only electricity from residues, which comprise of surplus bagasse and 50% post-harvest residues, at an existing sugar mill in South Africa was compared to the coproduction of ethanol from the hemicelluloses and electricity from the remaining solid fractions. Six different energy schemes were evaluated. They include: (1) exclusive electricity generation by combustion with high pressure steam cycles (CHPSC-EE), (2) biomass integrated gasification with combined cycles (BIGCC-EE), (3) coproduction of ethanol (using conventional distillation (CD)) and electricity (using BIGCC), (4) coproduction of ethanol (using CD) and electricity (using CHPSC), (5) coproduction of ethanol (using vacuum distillation (VD)) and electricity (using BIGCC), and (6) coproduction of ethanol (using VD) and electricity (using CHPSC). The pricing strategies in the economic analysis considered an upper and lower premium for electricity, on the standard price of the South African Energy Provider Eskom' of 31 and 103% respectively and ethanol prices were projected from two sets of historical prices.Results: From an energy balance perspective, ethanol coproduction with electricity was superior to electricity production alone. The VD/BIGCC combination had the highest process energy efficiency of 32.91% while the CHPSC-EE has the lowest energy efficiency of 15.44%. Regarding the economic comparison, it was seen that at the most conservative and optimistic pricing strategies, the ethanol production using VD/BIGCC had the highest internal rate of returns at 29.42 and 40.74% respectively. Conclusions:It was shown that bioethanol coproduction from the hemicellulose fractions of sugarcane residues, with electricity cogeneration from cellulose and lignin, is more efficient and economically viable than the exclusive electricity generation technologies considered, under the constraints in a South African context.
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