Smart grid is a concept and not a computer system or some sort of hardware. Therefore, smart grids can have multiple shapes because there is no single unified concept of what constitutes a ＂Smart Grid＂. Smart grid i...Smart grid is a concept and not a computer system or some sort of hardware. Therefore, smart grids can have multiple shapes because there is no single unified concept of what constitutes a ＂Smart Grid＂. Smart grid is considered a core concept in sustainable electricity generation and consumption while being projected as a silver-bullet to electric power system challenges. South Africa＇s dwindling reserve margin, high CO_2 emissions and future energy mix are outstanding reasons for her smart grid deployment. Who receives the credit for smart grid neology is contentious and smart grid definition is diverse. However, there is a consensus on its attributes or benefits. The establishment of SASGI （South Africa Smart Grid Initiative） and Eskom＇s commencement of deploying a hybrid smart grid model are proofs of the country＇s commitment towards smart grid concept and developments. Having recognized the relevance of smart grid concept and its developments, South Africa is presented with the opportunity to ＂leap-frog＂ and enhance the relevant proven applicable smart grid solutions.展开更多
A new model of a quantum heat engine （QHE） cycle is established, in which the working substance consists of an interacting electrons system. One of our purposes is to test the validity of the second law of thermodyn...A new model of a quantum heat engine （QHE） cycle is established, in which the working substance consists of an interacting electrons system. One of our purposes is to test the validity of the second law of thermodynamics by this model, which is more general than the spin-1/2 antiferromagnetic Heisenberg model since it would recover the spin model when the on-site Coulomb interaction U is strong enough. On the basis of quantum mechanics and the first law of thermodynamics, we show no violation of the second law of thermodynamics during the cycle. We further study the performance characteristics of the cycle by investigating in detail the optimal relations of efficiency and dimensionless power output. We find that the efficiency of our engine can be expressed as η = t22/t21 in the large-U limit, which is valid even for a four sites QHE.展开更多
文摘Smart grid is a concept and not a computer system or some sort of hardware. Therefore, smart grids can have multiple shapes because there is no single unified concept of what constitutes a ＂Smart Grid＂. Smart grid is considered a core concept in sustainable electricity generation and consumption while being projected as a silver-bullet to electric power system challenges. South Africa＇s dwindling reserve margin, high CO_2 emissions and future energy mix are outstanding reasons for her smart grid deployment. Who receives the credit for smart grid neology is contentious and smart grid definition is diverse. However, there is a consensus on its attributes or benefits. The establishment of SASGI （South Africa Smart Grid Initiative） and Eskom＇s commencement of deploying a hybrid smart grid model are proofs of the country＇s commitment towards smart grid concept and developments. Having recognized the relevance of smart grid concept and its developments, South Africa is presented with the opportunity to ＂leap-frog＂ and enhance the relevant proven applicable smart grid solutions.
基金supported by the National Natural Science Foundation of China (Grant Nos.50971011,11174022 and 10974011)the Beijing Natural Science Foundation (Grant No.1102025)+1 种基金the State Key Laboratory of Software Development Environment (Grant No.SKLSDE-2011ZX-19)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20091102110038)
文摘A new model of a quantum heat engine （QHE） cycle is established, in which the working substance consists of an interacting electrons system. One of our purposes is to test the validity of the second law of thermodynamics by this model, which is more general than the spin-1/2 antiferromagnetic Heisenberg model since it would recover the spin model when the on-site Coulomb interaction U is strong enough. On the basis of quantum mechanics and the first law of thermodynamics, we show no violation of the second law of thermodynamics during the cycle. We further study the performance characteristics of the cycle by investigating in detail the optimal relations of efficiency and dimensionless power output. We find that the efficiency of our engine can be expressed as η = t22/t21 in the large-U limit, which is valid even for a four sites QHE.
