Adaptive Wavelet Packet Transform

Two-dimensional over-complete wavelet packet transform can better represent the texture and long oscillatory patterns in natural images

Evaluation of peer-to-peer energy sharing mechanisms based on a multiagent simulation framework

Peer-to-peer (P2P) energy sharing involves novel technologies and business models at the demand-side of power systems, which is able to manage the increasing connection of distributed energy resources (DERs). In P2P energy sharing, prosumers directly trade energy with each other to achieve a win-win outcome. From the perspectives of power systems, P2P energy sharing has the potential to facilitate local energy balance and self-sufficiency. A systematic index system was developed to evaluate the performance of various P2P energy sharing mechanisms based on a multiagent-based simulation framework. The simulation framework is composed of three types of agents and three corresponding models. Two techniques, i.e. step length control and learning process involvement, and a last-defence mechanism were proposed to facilitate the convergence of simulation and deal with the divergence. The evaluation indexes include three economic indexes, i.e. value tapping, participation willing and equality, and three technique indexes, i.e. energy balance, power flatness and self-sufficiency. They are normalised and further synthesized to reflect the overall performance. The proposed methods were applied to simulate and evaluate three existing P2P energy sharing mechanisms, i.e. the supply and demand ratio (SDR), mid-market rate (MMR) and bill sharing (BS), for residential customers in current and future scenarios of Great Britain. Simulation results showed that both of the step length control and learning process involvement techniques improve the performance of P2P energy sharing mechanisms with moderate ramping / learning rates. The results also showed that P2P energy sharing has the potential to bring both economic and technical benefits for Great Britain. In terms of the overall performance, the SDR mechanism outperforms all the other mechanisms, and the MMR mechanism has good performance when with moderate PV penetration levels. The BS mechanism performs at the similar level as the conventional paradigm. The conclusion on the mechanism performance is not sensitive to season factors, day types and retail price schemes

Effects of variogram characteristics of coal permeability on CBM production: a case study in Southeast Qinshui Basin, China

The coalbed methane (CBM) resources of China are located mainly in 9 basins, Ordos, Qinshui, Jungar, Diandongqianxi, Erlian, Tuha, Tarim, Tianshan and Hailaer. Qinshui Basin, one of the richest CBM basins in China, has boosted its annual CBM production to 3 × 109 m3 (106 Bcf). The coal seams in Qinshui Basin are significant with high gas content but strong heterogeneous permeabilities ranging from 0.1 to 10 mD. This paper investigates the effects of spatial distribution characteristics of coal permeability on CBM production. The study area is the South Shizhuang CBM district, Southeast of Qinshui Basin. The distributions of porosity, ash content, coal density and gas content of the coal seam are generated using sequential Gaussian simulation (SGS) with only one realisation because this paper only justifies the effects of coal permeability on CBM production. The permeabilities of 17 wells are determined by matching these wells' water and gas production with bottom-hole pressure as constraint. Then, the distributions of coal permeabilities are generated using SGS with a commercial simulator. The history matched permeabilities range from 1.5 to 12 mD with average of 2.9 mD of the 17 wells. Eight variogram models are used to build the distributions of permeability. The cumulative gas productions of two different well-spacing cases, 300 m and 2000 m, are compared. There are 20 realisations of permeability for each of the eight models. The results show that historical matching can be used to obtain the porosity multipliers and the permeabilities in wells. The major direction of variogram has less effect on the uncertainty of field CBM production than variogram range. The effects of variogram range on the uncertainty of CBM production are positive for the case with short well spacing and vice versa for the case with long well spacing

Enhanced frequency response from industrial heating loads for electric power systems

Increasing penetration of renewable generation results in lower inertia of electric power systems. To maintain the system frequency, system operators have been designing innovative frequency response products. Enhanced Frequency Response (EFR) newly introduced in the UK is an example with higher technical requirements and customized specifications for assets with energy storage capability. In this paper, a method was proposed to estimate the EFR capacity of a population of industrial heating loads, bitumen tanks, and a decentralized control scheme was devised to enable them to deliver EFR. Case study was conducted using real UK frequency data and practical tank parameters. Results showed that bitumen tanks delivered high-quality service when providing service-1-type EFR, but underperformed for service-2-type EFR with much narrower deadband. Bitumen tanks performed well in both high and low frequency scenarios, and had better performance with significantly larger numbers of tanks or in months with higher power system inertia

Real interpolation of variable martingale Hardy spaces and BMO spaces

In this paper, we mainly consider the real interpolation spaces for variable Lebesgue spaces defined by the decreasing rearrangement function and for the corresponding martingale Hardy spaces. Let 0<q\le \infty 0 < q ≤ ∞ and 0<\theta <1 0 < θ < 1 . Our three main results are the following: \begin{aligned}{} & {} ({\mathcal {L}}_{p(\cdot )}({\mathbb {R}}^n),L_{\infty }({\mathbb {R}}^n))_{\theta ,q}={\mathcal {L}}_{{p(\cdot )}/(1-\theta ),q}({\mathbb {R}}^n),\{} & {} ({\mathcal {H}}_{p(\cdot )}^s(\Omega ),H_{\infty }^s(\Omega ))_{\theta ,q}={\mathcal {H}}_{{p(\cdot )}/(1-\theta ),q}^s(\Omega ) \end{aligned} ( L p ( · ) ( R n ) , L ∞ ( R n ) ) θ , q = L p ( · ) / ( 1 - θ ) , q ( R n ) , ( H p ( · ) s ( Ω ) , H ∞ s ( Ω ) ) θ , q = H p ( · ) / ( 1 - θ ) , q s ( Ω ) and \begin{aligned} ({\mathcal {H}}_{p(\cdot )}^s(\Omega ),BMO_2(\Omega ))_{\theta ,q}={\mathcal {H}}_{{p(\cdot )}/(1- \theta ),q}^s(\Omega ), \end{aligned} ( H p ( · ) s ( Ω ) , B M O 2 ( Ω ) ) θ , q = H p ( · ) / ( 1 - θ ) , q s ( Ω ) , where the variable exponent p(\cdot ) p ( · ) is a measurable function

Enhanced temperature uniformity by tetrahedral laser heating

emperature profile on a spherical sample that is heated by laser beams in various geometries while processed in vacuum is analyzed. Sample heating by one or four laser beams was considered. An analytical expression was derived for directional sample heating cases. It suggests an enhanced temperature uniformity over the samples when heated with four diffuse laser beams arranged in a tetrahedral geometry. This was experimentally verified by heating a spherical stainless steel sample by laser beams. Both the calculated and experimentally determined temperature variations over the sample suggest that use of diffuse four beams arranged in tetrahedral geometry would be effective in reducing temperature variation to within 1 K. The enhancement in the temperature uniformity for four diffuse beams arranged in a tetrahedral geometry by a factor of 50 over a single focused beam is promising to accurately measure of thermophysical properties. This drastic improvement in temperature uniformity might even enable atomic diffusion measurements in the undercooled liquid states of the bulk glass forming alloys since Marangoni and gravity driven convection will be substantially reduced

Unlocking the flexibility of combined heat and power for frequency response by coordinative control with batteries

Owners of combined heat and power (CHP), e.g., industrial manufacturers, are motivated to provide frequency response to power grids due to clear financial benefits. Yet, the slow response speed of CHP limits its capability in providing such services. Moreover, frequent adjustments would cause a faster lifetime reduction of CHP and rapid pressure fluctuation in the gas network. To further unlock the flexibility of CHP, this paper integrates a battery unit with CHP via a power electronic interface. A filter-based coordinative controller is designed for smoothing short-term fluctuations in CHP outputs. Based on the filter parameters and frequency response requirements, the minimum required capacity of the battery is identified. The results show that the proposed system enhances the capability of CHP for frequency response and mitigates the associated adverse effects on the gas network. The required capacity of the battery is economically feasible considering the benefit it brings to the CHP