Managing regional security of supply : a case study from Scotland

Securing the supply of electricity to a region of a power system requires either generation capacity within that region, or transmission import capability coupled with generation elsewhere in the power system. The problem is one of co-optimising generation and transmission infrastructure. This paper begins by discussing changes in Great Britain (GB) regulator environment affecting the provision of regional security of supply: changes to the transmission charging regime; new regulatory arrangements including enhancements to the System Operator’s role, and the opening up of major new transmission projects to competition; and some limitations of the existing standard defining the methodology for calculating secure transmission capabilities. Scotland, as a region of the GB power system, provides an interesting case study in which to investigate the allocation of contributions to regional security of supply between transmission and various categories of generation. In particular, intermittent generation is currently ignored when calculating the level of transmission import capability required to maintain security of supply in a region, whilst it is considered in overall generation adequacy calculations at a system level. Whilst wind generation is not dispatchable, it is shown here that it does provide an additional source of generation availability that should be considered in studies into transmission import requirements. This paper uses historical data for Scottish generation availability from recent winters to investigate the likely impact of changes to the Scottish generation fleet on the need for secure transmission import capability into Scotland. It calculates transmission requirements based on the risk of requiring demand reduction within a region. Scenarios representing possible generation backgrounds in Scotland over the coming decade show that, measured in this way, wind generation can offset transmission import requirements by up to 25% of its installed capacity. The key conclusions of the paper are that a risk-based analysis of regional security of supply and transmission requirements can help allocate the true impact of different generators on the transmission import capability needed to secure supply to a region. Such a method can therefore be useful in informing the allocation of charges between parties and in developing planning standards to shape future investment in the system

Capacity markets and the EU target model – a Great Britain case study

The growth of interconnection between national electricity markets is key to the development and competitive efficiency of the Single EU Market for Electricity. However, in parallel with the development of the Single Market, a growing number of EU Member States have implemented – or are in the process of developing – national Capacity Mechanisms in order to ensure future security of supply, which may distort the cross-border trade of energy across interconnectors and reduce total welfare. In particular, the Electricity Market Reform (EMR) legislative package recently brought in by the UK government introduced a Capacity Market (in which two rounds of auctions have taken place to date) for the provision of generation capacity from 2018. In order to ensure that such national markets do not distort the wider energy market, it is important that the role of cross-border capacity, and the availability of interconnector capacity, is correctly consolidated into such mechanisms. In the first annual GB auction the net contribution of interconnection was included on a conservative basis informed by historical data, and while interconnectors have since been permitted to bid into the Capacity Market at a de-rated value (in a similar manner to domestic generation), generators in other markets are still not able to explicitly participate. This may continue to introduce market distortions and adversely impact both short-term dispatch and long-term investment decisions in both the GB and neighbouring markets. A number of routes are available to resolve this through a mechanism to permit cross-border participation of generators, but this requires resolution of a number of complicating factors, not least a means for properly allocating transmission capacity without introducing further distortions to the energy market. Alternative solutions could be enacted at an EU-level, such as through the alignment of Capacity Mechanisms to a common model, or the introduction of an EU-wide single Capacity Mechanism, but the current regulatory focus appears to remain on resolution of such issues at a national level

Synthesis of wind time series for network adequacy assessment

When representing the stochastic characteristics of wind generators within power system simulations, the spatial and temporal correlations of the wind resource must be correctly modelled to ensure that reserve and network capacity requirements are not underestimated. A methodology for capturing these correlations within a vector auto-regressive (VAR) model is presented, and applied to a large-scale reanalysis dataset of historical wind speed data for the British Isles. This is combined with a wind speed-to-power conversion model trained against historically metered data from wind farms on the Great Britain (GB) electricity system in order to derive a lightweight model for simulating injections of wind power across a transmission network. The model is demonstrated to adequately represent ramp rates, both at a site and network level, as well as the individual correlations between sites, while being suitable for network adequacy studies which may require the simulation of many years of operation

Adequacy assessment of future electricity networks

Liberalisation of electricity markets, changing patterns in the generation and use of electricity and new technologies are some of the factors that result in increased uncertainty about the future operating conditions of our power system. In this context, planning for future investments in power system requires careful selection and assessment of future operating conditions. This paper revisits the notion of power system adequacy and highlights the need for consideration of some factors that have hitherto tended not to be part of a transmission expansion planning process, in particular in respect of the credible range of possible values of system operating conditions and transitions between successive operating states. Firstly, we present some definitions of power system operational regions. Secondly, we present a stochastic optimisation model that measures the adequacy of a transmission network for given future operating conditions. Uncertainties in demand and generation are modelled using a large number of scenarios. The optimisation model identifies the critical future operating conditions needing the special attention of a power system planner. The proposed model is simulated on a 39-bus network, whereby it is shown that this model can identify critical operating conditions that need the attention of a system planner

Folding of a donor–acceptor polyrotaxane by using noncovalent bonding interactions

Mechanically interlocked compounds, such as bistable catenanes and bistable rotaxanes, have been used to bring about actuation in nanoelectromechanical systems (NEMS) and molecular electronic devices (MEDs). The elaboration of the structural features of such rotaxanes into macromolecular materials might allow the utilization of molecular motion to impact their bulk properties. We report here the synthesis and characterization of polymers that contain π electron-donating 1,5-dioxynaphthalene (DNP) units encircled by cyclobis(paraquat-p-phenylene) (CBPQT4+), a π electron-accepting tetracationic cyclophane, synthesized by using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The polyrotaxanes adopt a well defined “folded” secondary structure by virtue of the judicious design of two DNP-containing monomers with different binding affinities for CBPQT4+. This efficient approach to the preparation of polyrotaxanes, taken alongside the initial investigations of their chemical properties, sets the stage for the preparation of a previously undescribed class of macromolecular architectures

High-density information storage in an absolutely defined aperiodic sequence of monodisperse copolyester

Synthesis of a polymer composed of a large discrete number of chemically distinct monomers in an absolutely defined aperiodic sequence remains a challenge in polymer chemistry. The synthesis has largely been limited to oligomers having a limited number of repeating units due to the difficulties associated with the step-by-step addition of individual monomers to achieve high molecular weights. Here we report the copolymers of ??-hydroxy acids, poly(phenyllactic-co-lactic acid) (PcL) built via the cross-convergent method from four dyads of monomers as constituent units. Our proposed method allows scalable synthesis of sequence-defined PcL in a minimal number of coupling steps from reagents in stoichiometric amounts. Digital information can be stored in an aperiodic sequence of PcL, which can be fully retrieved as binary code by mass spectrometry sequencing. The information storage density (bit/Da) of PcL is 50% higher than DNA, and the storage capacity of PcL can also be increased by adjusting the molecular weight (~38???kDa)

Human eosinophil-airway smooth muscle cell interactions.

Eosinophils are present throughout the airway wall of asthmatics. The nature of the interaction between human airway smooth muscle cells (ASMC) and eosinophils was investigated in this study. We demonstrated, using light microscopy, that freshly isolated eosinophils from healthy donors rapidly attach to ASMC in vitro. Numbers of attached eosinophils were highest at 2 h, falling to 50% of maximum by 20 h. Eosinophil attachment at 2 h was reduced to 72% of control by anti-VCAM-1, and to 74% at 20 h by anti-ICAM-1. Pre-treatment of ASMC for 24h with TNF-alpha, 10 nM, significantly increased eosinophil adhesion to 149 and 157% of control after 2 and 20 h. These results provide evidence that eosinophil interactions with ASMC involve VCAM-1 and ICAM-1 and are modulated by TNF-alpha

How to win friends and influence people: the value of the cohort in a doctoral research training programme

open access articleThis article is not about retention and attrition rates, or about successful outcomes, or about supervision, even though these are at the nub of most research on the doctoral experience. This article concerns the experiences of doctoral students undertaking educational research methods training, as opposed to the experiences of the PhD itself. The specific phenomenon identified in this small group study is the value of peer interaction within the cohort. Three strands of this relationship, namely peer support, cultural mix and bonding/ad-hoc social gatherings have been investigated. Our findings illustrate the importance and unexpected value of the ‘cohort’ on the participants in this study as they journey towards academia

Gluon distributions in nucleons and pions at a low resolution scale

In this paper we study the gluon distribution functions in nucleons and pions at a low resolution $Q^2$ scale. This is an important issue since parton densities at low $Q^2$ have always been taken as an external input which is adjusted through DGLAP evolution to fit the experimental data at higher scales. Here, in the framework of a model recently developed, it is shown that the hypothetical cloud of {\it neutral} pions surrounding nucleons and pions appears to be responsible for the characteristic valence-like gluon distributions needed at the inital low scale. As an additional result, we get the remarkable prediction that neutral and charged pions have different intrinsic sea flavor contents.Comment: final version to appear in Phys. Rev. D. Discussion on several points enlarge

Do we expect light flavor sea-quark asymmetry also for the spin-dependent distribution functions of the nucleon?

After taking account of the scale dependence by means of the standard DGLAP evolution equation, the theoretical predictions of the chiral quark soliton model for the unpolarized and longitudinally polarized structure functions of the nucleon are compared with the recent high energy data. The theory is shown to explain all the qualitative features of the experiments, including the NMC data for $F_2^p (x) - F_2^n (x)$, $F_2^n (x) / F_2^p (x)$, the Hermes and NuSea data for $\bar{d}(x) - \bar{u}(x)$, the EMC and SMC data for $g_1^p(x)$, $g_1^n(x)$ and $g_1^d(x)$. Among others, flavor asymmetry of the longitudinally polarized sea-quark distributions is a remarkable prediction of this model, i.e., it predicts that $\Delta \bar{d}(x) - \Delta \bar{u}(x) = C x^{\alpha} [ \bar{d}(x) - \bar{u}(x)]$ with a sizable negative coefficient $C \simeq -2.0$ (and $\alpha \simeq 0.12$) in qualitative consistency with the recent semi-phenomenological analysis by Morii and Yamanishi.Comment: 14pages, including 5 eps_figures with epsbox.sty, late