Hierarchical model-based predictive control of a power plant portfolio

One of the main difficulties in large-scale implementation of renewable energy in existing power systems is that the production from renewable sources is difficult to predict and control. For this reason, fast and efficient control of controllable power producing units – so-called “portfolio control” – becomes increasingly important as the ratio of renewable energy in a power system grows. As a consequence, tomorrow's “smart grids” require highly flexible and scalable control systems compared to conventional power systems. This paper proposes a hierarchical model-based predictive control design for power system portfolio control, which aims specifically at meeting these demands.The design involves a two-layer hierarchical structure with clearly defined interfaces that facilitate an object-oriented implementation approach. The same hierarchical structure is reflected in the underlying optimisation problem, which is solved using Dantzig–Wolfe decomposition. This decomposition yields improved computational efficiency and better scalability compared to centralised methods.The proposed control scheme is compared to an existing, state-of-the-art portfolio control system (operated by DONG Energy in Western Denmark) via simulations on a real-world scenario. Despite limited tuning, the new controller shows improvements in terms of ability to track reference production as well as economic performance.     

Multi-instance genetic programming for web index recommendation

This article introduces the use of a multi-instance genetic programming algorithm for modelling user preferences in web index recommendation systems. The developed algorithm learns user interest by means of rules which add comprehensibility and clarity to the discovered models and increase the quality of the recommendations. This new model, called G3P-MI algorithm, is evaluated and compared with other available algorithms. Computational experiments show that our methodology achieves competitive results and provide high-quality user models which improve the accuracy of recommendations.     

Phosphorus removal by granular activated alumina

Phosphorus removal from wastewater may be carried out by fixed-bed adsorption using activated alumina. In order to prevent unacceptable head-losses coarse-grained alumina must be used. Such systems have been referred to by several authors in literature. The mass transport characteristics of the system has so far, however, not been given a thorough investigation. This study uses the homogeneous surface diffusion model (HSDM) to describe the process as influenced by the system parameters.A sensitivity analysis is presented to optimize the process design for given conditions. The pH, the alumina particle size and the column length are found to be very important parameters determining the column performance. The process is very well suited for designing a beds-in-series system.     

工业流化床乙烯气相共聚合过程的研究 Ⅰ.产品分子量的稳态模拟

通过对Ｕｎｉｐｏｌ聚乙烯生产过程中影响聚合物分子量诸因素的分析，建立了包含乙烯分压和催化剂加料速率两个新变量的、用于表征聚合物分子量（ＭＩ）的稳态模型：ｌｎＭＩ＝Ａ０＋Ａ１／Ｔ＋Ａ２ｌｎ（Ａ３＋∑ｉｊＡｉｘｊ）利用工业装置上的操作数据对模型中诸参数进行估值。将该模型用于实际产品ＭＩ值的预测，计算值与分析结果的平均相对误差为４．６７％。表明该模型可以很好地模拟工业生产过程。     

面向并行工程的智能型约束网络管理系统

在前期研究工作的基础上，提出了一个面向并行工程管理模式的智能约束网络管理系统的功能结构。     

Assessment of the interaction between the Canadian Regional Climate Model and lake thermal–hydrodynamic models

This paper describes our preliminary assessment of the system requirements (data, interface and process) for implementation of terms describing lake effects in the Canadian Regional Climate Model. We demonstrate test results for one-dimensional (1-D) and three-dimensional (3-D) models for lake hydrodynamics that have been tested and prepared for interfacing with atmospheric circulation models. We discuss the use of a physical interface model, Canadian Land Surface Scheme (CLASS), that is under consideration for the air–water interface. Our preliminary assessment indicates that it is technically feasible to apply the combination of small shallow lake (slab) model, 1-dimensional vertical model and 3-dimensional circulation model (for very large lakes), together with the current land–air linkage used in regional climate modelling in Canada. Whether we can discern the necessary conditions for invoking each of the models to the lakes present in individual regional climate grid cells is still to be determined.     

Experimental Investigation of Grouted Helical Piers for Use in Foundation Rehabilitation

Building rehabilitation is critical for numerous older urban areas, many of which have inadequate foundations to support new demands. Consequently, development of practical methods to strengthen existing foundations is crucial. In engineering practice, both subsurface grouting and helical piers have been widely used to address these issues by strengthening the foundation. If the solid shaft of a typical helical pier is replaced by a hollow shaft, then helical piers provide the ability to deliver grout. It is hypothesized that these grouted helical pier systems could address foundation strengthening needs. This paper presents findings from an exploratory research program where grouting and pier placement tools were developed and tested on the large geotechnical centrifuge at the University of California, Davis. Experimental methods and procedures developed are presented, and observations regarding the formation of grout bulbs under different conditions are analyzed. Physical observation of the test specimens indicates that average grout bulb diameters of 0.6–1.9 times the helix diameter (Dh) are attainable. For similar grout mixes, 20–50% larger grout bulbs can be attained by adding just a modest amount of injection pressure. Future research may use these results to develop load performance data.     

Numerical modelling and flow visualization of mixing of stratified layers and rollover in LNG

A numerical model has been developed to study the mixing of two initially stratified layers which are subjected to a uniform lateral heat flux. An important distinction is made between the free surface and the liquid/liquid interface with regard to the different flow characteristics of the two layers. In the upper layer where warm liquid is cooled at the evaporating surface, the convective circulation is featured by a strong downward core flow; in contrast, the fluid flow in the lower layer is mainly confined to the wall boundary and is much weaker. Flow visualization experiments show that mixing of two stratified layers generally involves two stages in sequence: migration of the interface and rapid mixing between the remaining liquids. The interface movement is due to entrainment mixing at the interface. When the two layers approach density equalization, the interface becomes increasingly unstable and the core flow in the upper layer is able to break into the lower layer. The base to side heat flux ratio appears to be a major factor in determining the mode and intensity of the subsequent mixing at a rollover incident.     

The reconstruction of past patterns of tilled fields from historical cadastral maps using GIS

Information derived from a historical infield cadastral map dated 1874 and its written protocol was combined with data on four landscape characteristics (distance to the hamlet, 1 slope, folded aspect and quaternary geology) in a GIS-based 3D model in an attempt to develop a methodology for reconstructing earlier tilled field patterns. The study area was the farm of Grinde in Western Norway. The areas that the farmers themselves considered to be best for growing crops in 1874 sloped gently, faced south-west, were close to the hamlet and were on glacio-fluvial deposits or a thick layer of moraine. More than 80% of the fields expected to be the oldest appeared to be correctly identified. This pilot study shows that it is possible to identify the probable location of the oldest tilled fields both on maps and in the terrain, using land consolidation documents or other data on crop sowing and yields from historical sources even where no land consolidation documents are available. The method may be helpful in determining areas that should be managed or protected in specific ways to maintain the value of the cultural landscape.     

Modelling changes to electricity demand load duration curves as a consequence of predicted climate change for Australia

In this paper, we describe a method for constructing regional electricity demand data sets at 30 min intervals, which are consistent with climate change scenarios. Specifically, we modify a commonly used linear regression model between regional electricity demand and climate to also describe intraday variability in demand so that regional load duration curves (LDCs) can be predicted. The model is evaluated for four different Australian states that are participants in the Australian National Electricity Market (NEM) and the resultant data sets are found to reproduce each state's LDCs with reasonable accuracy. We also apply the demand model to CSIRO's Mk 3 global climate model data sets that have been downscaled to 60 km resolution using CSIRO's conformal-cubic atmospheric model to estimate how LDCs change as a consequence of a 1 °C increase in the average temperature of Australian state capital cities. These regional electricity demand data sets are then useful for economic modelling of electricity markets such as the NEM.