Stochastic programming approach for optimal day-ahead market bidding curves of a microgrid

The deregulation of electricity markets has driven the need to optimise market bidding strategies, e.g. when and how much electricity to buy or sell, in order to gain an economic advantage in a competitive market environment. The present work aims to determine optimal day-ahead market bidding curves for a microgrid comprised of a battery, power generator, photovoltaic (PV) system and an electricity load from a commercial building. Existing day-ahead market bidding models heuristically fix price values for each allowed bidding curve point prior to the optimisation problem or relax limitations set by market rules on the number of price–quantity points per curve. In contrast, this work integrates the optimal selection of prices for the construction of day-ahead market bidding curves into the optimisation of the energy system schedule; aiming to further enhance the bidding curve accuracy while remaining feasible under present market rules. The examined optimisation problem is formulated as a mixed integer linear programming (MILP) model, embedded in a two-stage stochastic programming approach. Uncertainty is considered in the electricity price and the PV power. First stage decisions are day-ahead market bidding curves, while the overall objective is to minimise the expected operational cost of the microgrid. The bidding strategy derived is then examined through Monte Carlo simulations by comparing it against a deterministic approach and two alternative stochastic bidding approaches from literature

A unified way of analyzing some greedy algorithms

A unified way of analyzing different greedy-type algorithms in Banach spaces is presented. We define a class of Weak Biorthogonal Greedy Algorithms and prove convergence and rate of convergence results for algorithms from this class. In particular, the following well known algorithms --- Weak Chebyshev Greedy Algorithm and Weak Greedy Algorithm with Free Relaxation --- belong to this class. We consider here one more algorithm --- Rescaled Weak Relaxed Greedy Algorithm --- from the above class. We also discuss modifications of these algorithms, which are motivated by applications. We analyze convergence and rate of convergence of the algorithms under assumption that we may perform steps of these algorithms with some errors. We call such algorithms approximate greedy algorithms. We prove convergence and rate of convergence results for the Approximate Weak Biorthogonal Greedy Algorithms. These results guarantee stability of Weak Biorthogonal Greedy Algorithms

Testing the GRACE follow-on triple mirror assembly

We report on the successful testing of the GRACE follow-on triple mirror assembly (TMA) prototype. This component serves to route the laser beam in a proposed follow-on mission to the Gravity Recovery and Climate Explorer (GRACE) mission, containing an optical instrument for space-based distance measurement between satellites. As part of this, the TMA has to meet a set of stringent requirements on both the optical and mechanical properties. The purpose of the TMA prototype testing is to establish the feasibility of the design, materials choice and fabrication techniques. Here we report on co-alignment testing of this device to the arc second (5 μrad) level and thermal alignment stability testing to 1 μ rad {{K}-1}

Laboratory intercomparison of solar absorptance and thermal emittance measurements at room temperature

Solar thermal absorber coatings play an important role in the opto-thermal efficiency of receivers in Concentrated Solar Power (CSP). Two standard figures of merit are the solar absorptance αsol and thermal emittance εth, derived from spectral directional hemispherical reflectance measurements at room temperature. These two figures of merit allow comparing coating formulations in terms of performance and durability. In this study, a black coating and a solar selective coating are optically characterized by different laboratories to compare spectral datasets, solar absorptance αsol and thermal emittance εth calculations. The comparison includes various benchtop spectrophotometers operating in the UV-VIS-NIR and Infrared spectral ranges as well as three commercial portable reflectometers/emissometers. A good agreement is found between the nine parties participating in this intercomparison campaign. The black coating αsol value is 96.6 ± 0.2%, while the solar selective coating αsol value is 94.5 ± 0.4%. For the thermal emittance, spectral data is concatenated and integrated from 0.3 to 16 μm. The black coating εth value calculated at 650 °C is 80.8 ± 3.8%, while the solar selective coating εth value calculated at 650 °C is 25.0 ± 0.5%

In-Orbit Performance of the GRACE Follow-on Laser Ranging Interferometer

The Laser Ranging Interferometer (LRI) instrument on the Gravity Recovery and Climate Experiment (GRACE) Follow-On mission has provided the first laser interferometric range measurements between remote spacecraft, separated by approximately 220 km. Autonomous controls that lock the laser frequency to a cavity reference and establish the 5 degrees of freedom two-way laser link between remote spacecraft succeeded on the first attempt. Active beam pointing based on differential wave front sensing compensates spacecraft attitude fluctuations. The LRI has operated continuously without breaks in phase tracking for more than 50 days, and has shown biased range measurements similar to the primary ranging instrument based on microwaves, but with much less noise at a level of 1 nm/Hz at Fourier frequencies above 100 mHz. © 2019 authors. Published by the American Physical Society

Analysis of flame patterns in cryogenic propellant combustion

International audienceAbstract: Design and optimization of high performance rocket engines may be improved by detailed studies of the basic combustion mechanisms. Much detailed information exists on elementary processes such as atomization, multiple jet interactions, vaporization of single droplets, structure of spray flames, ignition of nonpremixed systems etc. It is however important to approach the real conditions existing in rocket motors and to this purpose several facilities for cryogenic propellant combustion research have been designed and constructed. One experimental set-up designated as ''Mascotte'' is operated by ONERA and used for fundamental research as well as technical studies. This article describes results of experiments conducted in this facility by our laboratory. Two series of tests carried out during the last two years have provided a large set of images of combustion in a liquid oxygen/gaseous hydrogen coaxial injection geometry operating at atmospheric pressure and at 5 and 10 bars. The data correspond to laser elastic scattering of the spray, spontaneous emission of OH radicals and planar laser induced fluorescence of these radicals. Fluorescence is obtained by pumping the X-2 Pi(upsilon '' = 0) --> A(2) Sigma(upsilon' = 1) band of OH. Off-resonance light radiation is observed with an intensified CCD camera. The large data base of images collected in these experiments provide the general flame structure in the injector nearfield, and may be used to determine the position of flame stabilization. Effects of global injection parameters (momentum flux ratio, Weber number, mixture ratio) and operating pressure are described. It is shown that the conditions prevailing in the liquid and gaseous jets influence the flame stabilization process, the instantaneous combustion patterns and the mean flame shape

Investigation of cryogenic propellant flames using computerized tomography of emission images

International audienceAbstract: Cryogenic propellant combustion is investigated in this paper. It is shown that the mean flame structure may be obtained by applying computerized tomography principles to oxygen-hydrogen (OH) emission images obtained from experiments on a shear coaxial injector. The data correspond to injection conditions typical of those found in rocket motors, but to lower operating pressures of 1, 5, and 10 bar. The transformed emission images yield the mean volumetric OH emission distribution. This quantity may be roughly interpreted as the mean volumetric rate of reaction. The data provide the location of the mean flame zone and confirm that stabilization takes place in the immediate vicinity of the injection plane

European Unions and the problems of an ecology of work

2.00SIGLEAvailable from British Library Document Supply Centre- DSC:9261.962(34) / BLDSC - British Library Document Supply CentreGBUnited Kingdo