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Abstract Reversible carbonation/calcination of CaCO3 is a promising technology for thermochemical energy storage in concentrated solar power plants. However, the major drawback of this technology is the rapid deactivation of CaO due to sintering. In this study, newly developed CaCO3/graphite nanosheets composites were synthesized as the heat storage medium through a one-pot route varying the graphite nanosheets load (3–12 wt%). The impregnation of the composites with H3BO3 solutions enhance the initial weightlessness temperature of graphite nanosheets from 900 °C to 1050 °C in pure CO2 atmosphere, thus upgrading the stability of graphite nanosheets during heat storage/release process. The performances of the synthesized composites were evaluated by thermogravimetric analysis, which simulates the heat storage cycle. The composites showed improved heat storage/output capacity and faster heat input/output rate compared to pure CaCO3. Only 3 wt% of graphite nanosheets was needed to effectively stabilize the heat storage capacity of the material. The heat storage capacity of composites with 3 wt% graphite nanosheets is 1313 kJ/kgcomposite after 50 cycles, corresponding to 2.9 times as much as that of pure CaCO3. This high stability is attributed to the unique synthetic strategy in which the CaCO3 nanoparticles uniformly coated on graphite nanosheets surface, and their sintering and aggregation were prevented. This work brings the development of this technology to a level closer to its industrial application.

Shale gas, due to its clean-burning and efficient nature, is becoming an increasingly promising alternative energy resource. It is commonly held that promoting shale gas development will gradually play a significant role in meeting the energy needs of economic and social development as well as reducing harm to the environment. Given the significant implications, many countries are pursuing shale gas opportunities. However, numerous concerns have been raised about the economics of shale gas development, as it is difficult to evaluate. Accurately evaluating the economic viability of shale gas development to reduce investment risks and increase investment opportunity is the key issue that needs to be urgently addressed. This paper presents a systematic review and examination of the technical and economic evaluation techniques for the development of shale gas to provide an overview of their current status. Over time, some progress has been made in existing technical–economic evaluation techniques. It is worth noting that these techniques need to be further improved to more precisely assess the economic feasibility of developing shale gas for assisting investment decisions effectively. For this reason, various potentially useful ideas and approaches are presented to propose some potential improvement in evaluation techniques for shale gas development, which may materialize in possible future trends.

Abstract In solid fuel (such as lignite) chemical looping combustion, solid fuels undergo pyrolysis and gasification. The volatiles from pyrolysis and the gasification product (CO/H 2 ) react with oxygen carriers. The gas conversion (to CO 2 /H 2 O) in the fuel reactor is a key point. However, char particles of different sizes and conversion ratios cause segregation in the fuel reactor, which influences the contact time between fuel gases and the carrier, thereby changing the gas conversion behavior. In order to gain information on obtaining a high gas conversion in the fuel reactor, this work focused on the effect of the char particle segregation on gas conversion. Different factors – the char particle size, the fluidizing gas velocity, and the oxygen carrier reactivity – were taken into account. Smaller char particles with low density would float on top of the fluidized bed, corresponding to a low gas conversion ( U mf in the Fe63Al bed) can reduce the segregation effect, resulting in a higher CO conversion. High reactivity carriers can convert CO completely although segregation exists, whereas low reactivity carriers exhibit the segregation effect and thus corresponds to a low CO conversion.

Abstract With increasing prosumers employed with flexible resources, advanced demand-side management has become of great importance. To this end, integrating demand-side flexible resources into electricity markets is a significant trend for smart energy systems. The continuous double auction (CDA) market is viewed as a promising P2P (peer to peer) market mechanism to enable interactions among demand side prosumers and consumers in distribution grids. To achieve optimal operations and maximize profits, prosumers in the electricity market must act as price makers to simultaneously optimize their operations and trading strategies. However, the CDA-based market is difficult to model explicitly because of its information-based clearing mechanism and the stochastic bidding behaviors of its participants. To facilitate prosumers actively participating in the CDA market, this paper proposes a novel prediction-integration strategy optimization (PISO) model. A surrogate market prediction model based on Extreme Learning Machine (ELM) is developed, which learns the interaction relationship between prosumer bidding actions and market responses from historical transaction data. Moreover, the prediction model can be conveniently transformed and integrated into the prosumer operation optimization model in the form of constraints. Therefore, prosumer operations and market trading strategies can be jointly optimized through the proposed approach, facilitating the integration of flexible resources into electricity markets. Numerical studies demonstrate the effectiveness of the proposed model by comparing with existing CDA trading strategies under various market conditions.