Improving the Efficiency of Stand-Alone Solar PV Power Plants

As a source of alternative energy, solar energy has apparent advantages, including a renewable, inexhaustible, and environmentally friendly resource. However, it has not become widely spread in the Russian Federation. Among the disadvantages of using solar energy are high equipment cost, low efficiency of photovoltaic solar cells, the generated electrical energy instability. The spatio-temporal variability of solar access causes electrical energy instability. It is possible to increase solar photovoltaic plant efficiency by using a tracking system to change the plant sun's spatial orientation. The paper offers mathematical and simulation models of a solar photovoltaic plant with a solar tracking system that allows the plant to be automatically oriented to the sun by matching the production mode and the solar access level. The use of the azimuth plant control system on the sun will increase the power production of the solar PV plant by an average of 28%. The same value will increase by 40% when using the full plant control system.

Sizing Control and Hardware Implementation of a Hybrid Wind-Solar Power System, Based on an ANN Approach, for Pumping Water

In our day, solar energy and wind energy are becoming more and more used as renewable sources by various countries for different uses such as in an isolated home. These energies admit a unique limitation related to the characteristic of energy instability. For this, the objective of this manuscript is to command and synchronize the power flow of a hybrid system using two sources of energy (solar and wind). The first contribution of our work is the utilization of an artificial neural network controller to command, at fixed atmospheric conditions, the maximum power point. The second contribution is the optimization of the system respecting real-time constraints to increase a generating system performance. As a matter of fact, the proposed system and the controller are modeled using MATLAB/Simulink and a Xilinx System Generator is utilized for hardware implementation. The simulation results, compared with other works in the literature, present high performance, efficiency, and precision. The suggested system and its control strategy give the opportunity of optimizing the hybrid power system performance, which is utilized in rural pumping or other smart house applications.

Stability Analysis of Water-Resistant Strata in Karst Tunnel Based on Releasable Elastic Strain Energy

In this paper, the energy instability criterion of water-resistant strata and rock mass failure index (RMFI) are proposed, respectively, based on releasable elastic strain energy Ue. RMFI is employed to represent the damage extent of water-resistant strata. When RMFI<1.0, rock mass is stable. When RMFI=1.0, rock mass is in the critical instability state. When RMFI>1.0, rock mass is unstable. The releasable elastic strain energy Ue and RMFI program is performed by FISH programming language of Flac3D software. Then, the authors apply Flac3D software to analyze the distribution law of releasable elastic strain energy Ue and failure zone under different width of concealed karst cave. Finally, combined with the numerical analysis, a case study is carried out to illustrate the rationality, effectiveness, and feasibility through using RMFI to predict safe thickness of water-resistant strata.

South African energy instability could return

Headline SOUTH AFRICA: Eskom energy instability could return

Negative energy, instability, and AdS–CFT This paper was presented at the Theory CANADA 4 conference, held at Centre de recherches mathématiques, Montréal, Québec, Canada on 4–7 June 2008.

We consider a freely orbifolded AdS5 × S5 and demonstrate that standard boundary conditions allow states of arbitrarily negative energy. These states describe bubbles that are regular up to singularities due to smeared D3-branes. We discuss the evolution of this data and point out that if the usual boundary conditions are enforced such bubbles may never reach infinity.