UK scenario of islanded operation of active distribution networks with renewable distributed generators

This paper reports on the current UK scenario of islanded operation of active distribution networks with renewable distributed generators (RDGs). Different surveys indicate that the present scenario does not economically justify islanding operation of active distribution networks with RDGs. Anti-islanding protection schemes currently enforce the renewable distributed generators (RDGs) to disconnect immediately and stop generation for grid faults through loss of grid (LOG) protection system. This greatly reduces the benefits of RDG deployment. With rising RDG penetration, much benefit would be lost if the RDGs are not allowed to island only due to conventional operational requirement of utilities. For preventing disconnection of RDGs during LOG, several islanding operation, control and protection schemes are being developed. Technical studies clearly indicate the need to review parts of the ESQCR (Electricity Safety, Quality and Continuity Regulations) for successful islanded operations. Commercial viability of islanding operation must be assessed in relation to enhancement of power quality, system reliability and supply of potential ancillary services through network support. Demonstration projects under Registered Power Zone and Technical Architecture Projects should be initiated to investigate the usefulness of DG islanding. However these efforts should be compounded with a realistic judgement of the associated technical and economic issues for the development of future power networks.     

Unconventional complexity measures for unconventional computers

Unconventional computers—which may, for example, exploit chemical/analogue/quantum phenomena in order to compute, rather than electronically implementing discrete logic gates—are widely studied in both theoretical and practical contexts. One particular motivation behind unconventional computation is the desire efficiently to solve classically difficult problems—we recall chemical-computer attempts at solving NP -complete problems such as the Travelling Salesperson Problem—, with computational complexity theory offering the criteria for judging this efficiency. However, care must be taken here; conventional (Turing-machine-style) complexity analysis is not always appropriate for unconventional computers: new, non-standard computational resources, with correspondingly new complexity measures, are often required. Accordingly, we discuss in the present paper various resources beyond merely time and space (and, indeed, discuss various interpretations of the term ‘resource’ itself), advocating such resources’ consideration when analysing the complexity of unconventional computers. We hope that this acts as a useful starting point for practitioners of unconventional computing and computational complexity.     

Application of novel polar representation method for monitoring minor engine condition variations

In an earlier study, a Noval Polar Presentation (NPP) method has been suggested to detect the engine combustion-related faults for medium-speed diesel engines. The earlier proposed NPP method basically used the signature of the crankshaft torsional vibration to identify the faulty cylinder accurately. However, the detection of only a large fault like the cylinder misfiring for the 2 typical engines (16-cylinder and 20-cylinder engines) has been demonstrated in the earlier study. Now the usefulness of the NPP method in detection of even a very small level of the engine combustion fault like an earlier or later opening of the fuel injection valve by just a few degrees has been presented here.     

Middle distillates from hydrocracking of FT waxes: Composition,characteristics and emission properties

A light cobalt catalyzed Fischer–Tropsch (FT) wax was subjected to hydrocracking in the range of temperature 319–351 °C and hydrogen pressure between 3.5 and 6.0 MPa. The catalyst used was platinum on amorphous silica–alumina. Hydrocracking reaction led to an increase of middle distillate yield up to 85% with a contemporary increase of iso-paraffins concentration which resulted in a remarkable improvement of cold flow properties of the products. The freezing point of C₁₀–C₁₄ fraction passed from ?23 to ?45 °C while the pour point of C₁₅–C₂₂ fraction decreased from 13 to ?23 °C. The latter fraction displayed high cetane numbers ranging between 75 and 80. Changes in carbon distribution and molecular structure of products during hydrocracking have been rationalized in the light of the accepted hydrocracking mechanism where n-paraffins undergo to consecutive isomerization reactions leading to isomers with progressively higher branching degree and concomitant cracking reaction. Experimental evidences support the view that apparent reactivity of n-paraffins is chain length dependent, increasing with the molecular weight. Detailed characterization by NMR and GC showed that branching groups abundance in the middle distillate products was the following: methyl ? ethyl > propyl.Emission tests carried out with FT diesel and commercial ultra low sulfur diesel showed that FT diesel has excellent combustion properties and leads to a reduction of emissions.     

Characterization of filled rubbers using small-angle X-ray scattering

It is demonstrated how small-angle X-ray scattering (SAXS) can be used to characterize the structure of fillers such as carbon black and silica both before and after their incorporation into natural rubber. It is found that SAXS has significant advantages over conventional techniques such as gas adsorption or electron microscopy in determining both the size and distribution of sizes of the filler particles. The results are shown to be in good agreement with those obtained using conventional techniques. In addition it is demonstrated that SAXS can be used to characterize the filler particlesin situ enabling the volume fraction, particle size and particle surface area to be determined for a filled rubber and factors such as aggregation to be examined.     

Local mass transport effects in the FM01 laboratory electrolyser

A number of patterns of segmented line electrodes have been manufactured using copper printed circuit board technology. These segmented electrodes have been used to investigate local mass transport effects in ICI's FM01-LC parallel plate electrolyser. It is shown that in the absence of a turbulence promoter the current distribution is uneven. Along the direction of electrolyte flow, a tertiary current distribution is observed. In addition, close to the cell entrance, an uneven current distribution occurs perpendicular to the direction of electrolyte flow; this reflects the design of the electrolyte distributor. With a turbulence promoter the current distribution is more even and the entry effects are much reduced. The turbulence promoter can, however, impose its own pattern on the current distribution perpendicular to the flow.     

Modelling of catalyst particle skin effects using a 3-D pore network model and quantitive microscopy

The pore structure of fragments of steam reforming catalyst ring-shaped pellets was characterised so as to simulate a larger particle using larger pore networks comprising millions of pore segments. The pore size distribution generated for a 3-D stochastic network was deduced from the experimental mercury penetration curve. The penetration processes which take place within the pore network at different pressures can be visualised by randomly slicing irregular 3-D pore networks to create 2-D “Virtual reality slice” images. The experimental visualisation technique of low-melting alloy impregnation was applied to the larger ring catalyst fragments at several pressure levels in order to investigate the effect of size, the fragment geometry, and a suspected skin effect on the mercury penetration curve for these particles. The experimental scanning electron microscopy images, obtained from polished sections of a large 5-mm ring fragment, can be compared directly with the 2-D virtual slice images from randomised 3-D pore networks for direct quantification of the pore structure using image analysis techniques.     

Advanced combustion,cooling and refrigeration,waste gas treatment,heat integrated separation and case studies

This is an overview of a Special Issue that has been dedicated to the 8th conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction – PRES’05. Twelve papers from the conference have been selected and peer-reviewed and cover various subjects of advanced combustion, cooling and refrigeration and waste gas treatment. These have been supplemented with heat integrated separation and case studies.