Are the Current Smart Grid Concepts Likely to Offer a Complete Smart Grid Solution?

At present, the structure of power systems is greatly changing due to the penetration of decentralized generations. Although they encompass a high flexibility potential, their large-scale penetration interferes with the power system operation at all voltage levels. To get rid of this flaw and exploit their flexibility, different concepts like Virtual Power Plants, Microgrids and Cellular Approach have been introduced but still no solution is in sight. Under these conditions, it seems quite intriguing to find out whether these concepts are likely to offer a complete solution or not. This paper presents ten criteria to assess the complete Smart Grid solution and introduces a comprehensive evaluation system based on cloud-charts. The paper looks into the already existing solutions, which are respectively based on Virtual Power Plants, Microgrids and Cellular Approach concepts. The investigations have shown that none of these solutions meets all criteria necessary for a complete Smart Grid solution. Even a combination of different criteria fails to yield the desired results.

Beyond cost reduction:improving the value of energy storage in electricity systems

From a macro-energy system perspective,an energy storage is valuable if it contributes to meeting system objectives,including increasing economic value,reliability and sustainability.In most energy systems models,reliability and sustainability are forced by constraints,and if energy demand is exogenous,this leaves cost as the main metric for economic value.Traditional ways to improve storage technologies are to reduce their costs;however,the cheapest energy storage is not always the most valuable in energy systems.Modern techno-economical evaluation methods try to address the cost and value situation but do not judge the competitiveness of multiple technologies simultaneously.This paper introduces the‘market potential method’as a new complementary valuation method guiding innovation of multiple energy storage.The market potential method derives the value of technologies by examining common deployment signals from energy system model outputs in a structured way.We apply and compare this method to cost evaluation approaches in a renewables-based European power system model,covering diverse energy storage technologies.We find that characteristics of high-cost hydrogen storage can be more valuable than low-cost hydrogen storage.Additionally,we show that modifying the freedom of storage sizing and component interactions can make the energy system 10% cheaper and impact the value of technologies.The results suggest looking beyond the pure cost reduction paradigm and focus on developing technologies with suitable value approaches that can lead to cheaper electricity systems in future.

Effects of the Reactive Power Injection on the Grid—The Rise of the Volt/var Interaction Chain

The major challenge to increase the decentralized generation share in distribution grids is the maintenance of the voltage within the limits. The inductive power injection is widely used as a remedial measure. The main aim of this paper is to study the effect of the reactive power injection (by what-ever means) on radial grid structures and their impact on the voltage of the higher voltage-level grids. Various studies have shown that, in addition to the major local effect on the voltage at the injection point, the injection of the reactive power on a feeder has a global effect, which cannot be neglected. The reactive power flow and the voltage on the higher voltage level grid are significantly affected. In addition, a random effect is introduced by the DGs which are connected through inverters (using wind or PVs). Although their operation is in accordance with the grid code, a volatile reactive power flow circulates on the grid. Finally, this study proposes the implementation of the “Volt/var secondary control” interaction chain in order to increase the distributed generation share at every distribution voltage level, be it medium or low voltage, and at the same time to guarantee a stable operation of the power grid. Features of Volt/var secondary control loops ensure a resilient behavior of the whole chain.

Comparison of three different CFD methods for dense fluidized beds and validation by a cold flow experiment

This work focuses on a comparison between three different numerical CFD methods, namely Euler-Euler, Euler-Lagrange-stochastic, and Euler-Lagrange-deterministic, to treat a dense spouted bed, A simple cold flow experiment was used to investigate the hydrodynamics of a gas-solid flow in a three dimensional lab-scale spouted bed, In this context, two different air mass flow rates, 0,005 and 0.006 kg/s, were applied during fluidization. The experimental bed behaviour was recorded with a high-speed camera to validate the numerical predictions in terms of bubble size, bed expansion rate, and particle velocities at different reactor heights. The numerical setup was kept similar between all three modelling approaches, At both gas mass flow rates all three approaches are able to capture the overall bed expansion. However, at higher gas mass flow rates, discrepancies between experiment and simulation increase for the Euler-Euler and Euler-Lagrange-stochastic models. The Euler-Lagrange deterministic model most accurately predicts the flow pattern at both mass flow rates. The main reasons for discrepancies between simulation and experiment result from modelling of the collision and friction forces.

An experimental study of rotational pressure loss in rotor-stator gap

The annular gap between rotor and stator is an inevitable flow path of a throughflow ventilated electrical machine,but the flow entering the rotor-stator gap is subjected to the effects of rotation.The pressure loss and volumetric flow rate across the rotor-stator gap were measured and compared between rotating and stationary conditions.The experimental measurements found that the flow entering the rotor-stator gap is affected by an additional pressure loss.In the present study,the rotational pressure loss at the entrance of rotor-stator gap is characterised.Based upon dimensional analysis,the coefficient of entrance loss can be correlated with a dimensionless parameter,i.e.rotation ratio.The investigation leads to an original correlation for the entrance loss coefficient of rotor-stator gap arisen from the Coriolis and centrifugal effects in rotating reference frame.

Tracer advection in a pair of adjacent side-wall cavities, and in a rectangular channel containing two groynes in series

A model is presented of particle advection near groynes in an open channel. Open channel hydrodynamics is modelled using the shallow water equations, obtained as the depth-averaged form of Reynolds-averaged continuity and Navier-Stokes momentum equations. A Lagrangian particle-tracking model is used to predict trajectories of tracer particles advected by the flow field, with bilinear interpolation representing the continuous flow field. The particle-tracking model is verified for chaotic advection in an alternating flow field of a pair of blinking vortices. The combined shallow flow and Lagrangian particle-tracking model is applied to the simulation of tracer advection in flow past a pair of side-wall cavities separated by a groyne, and in an open rectangular channel containing a pair of parallel groynes oriented normal to the channel wall. The study is potentially useful in understanding mixing processes in shallow flow fields near hydraulic structures in wide rivers.

Tracer advection in an idealised river bend with groynes

This paper presents numerical simulations of particle advection in the bend of an open channel containing groynes, which is an idealised form of a shallow river bend in a wide river. The flow field is computed using a boundary-fitted solver of the non-orthogonal, curvilinear shallow water equations. The computational grid is generated by solving Poisson-type elliptic partial differential equations using an iterative multi-grid scheme for prescribed boundary coordinates. The shallow water equations are discretised with finite differences in space, and 4 t h order Runge-Kutta integration in time. Tracers introduced at specific initial locations have their trajectories computed using Lagrangian particle tracking. The numerical shallow flow model is verified by comparison to the analytical solution of fully developed flow in an open channel. The combined shallow flow and Lagrangian particle-tracking model is then used to simulate the advection of tracer particles in a rectangular channel containing a pair of parallel groynes, and tracer particles in a curved open channel containing groynes, of dimensions roughly equivalent to a Danube River bend.