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Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae) is a polyphagous parasitoid known to have an extremely wide host range, attacking larvae from at least 11 lepidopteran families. It was first detected in New Zealand in 1996 and spread rapidly, raising concerns that it may disrupt an integrated pest management program for Helicoverpa armigera (Hubner) that relied on two introduced larval parasitoids: Cotesia kazak and Microplitis croceipes. A series of laboratory experiments was undertaken to assess larval competition among these three parasitoid species. H. armigera larvae were exposed to the three parasitoid species in pairwise combinations and the subsequent formation of parasitoid cocoons and emergence of adults were recorded. Separate assays were run with 0, 24 and 48 h time intervals between ovipositions by each wasp species. The results showed that C. kazak prevailed over M. pulchricornis and M. croceipes in all experimental combinations and time intervals, accounting for 79–100% of parasitoid cocoons, and that M. pulchricornis was similarly dominant over M. croceipes. The observed dominance of C. kazak in processing tomato crops in New Zealand may be partly explained by the competitive advantage of its larvae, combined with a reportedly faster development rate. However, the nature of the competitive relationship between these species may well be modified by extrinsic factors in the field. In particular, M. pulchricornis may gain an advantage in more diverse cropping systems where it may exploit alternative hosts that are not suitable for the other species.

Natural populations of Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), also known as tomato/potato psyllid, were marked in potato [Solanum tuberosum L. (Solanaceae)] crops using Bacillus thuringiensis Berliner (Bt) to investigate the impact of dispersal on crop infestation and management of potential insecticide resistance in New Zealand. The technique was adapted from previous studies that used conventional spray applications of Bt to mark Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), and identified marked individuals with selective microbiological assays and identification of characteristic crystal inclusions. Initially, marking rates of B. cockerelli were improved by using ultra-low volume applications of undiluted Bt, but this result was not consistent. Several other pests and natural enemies were also marked. In mark-capture studies, marked B. cockerelli were captured over 3 days on yellow sticky traps in small trap plots of potatoes at 60, 120, 180, 250, and 350 m from the sprayed crop. Bactericera cockerelli flight activity occurred throughout daylight hours with evidence of bimodal diurnal peaks. Significantly greater numbers of B. cockerelli were captured in downwind traps. The combined dispersal curve derived from two mark-capture experiments estimated a mean dispersal distance for B. cockerelli of 100 m in 3 days and indicated that 10% of the population dispersed further than ca. 250 m. Over the period of a growing season, this level of dispersal suggests that B. cockerelli can disperse throughout a vegetable-growing region, with implications for crop infestation and management of potential insecticide resistance.

Subsampling of potato plants was assessed as a practical tool for monitoring Bactericera cockerelli tomatopotato psyllid (TPP) and other key pests and their predators at Pukekohe The total numbers of the key insect species and all their life stages on (1) the bottom leaf; (2) a middle leaf (the bottom leaf on the top half of the stem); (3) the bottom half of the stem; and (4) the top half of the stem were compared with numbers on the whole stem Assessing the top half of the stem was the most reliable subsampling method for the three main insects sampled while assessing a middle leaf also gave a reliable estimate for two out of the three insects A crop scouting protocol for monitoring TPP infestations based on sampling 100 middle leaves off 50 randomly selected plants in a crop is now recommended by the potato industry in New Zealand

This study investigates the magnitude of movement of the area of deposition of electrospun fibres in response to an applied auxiliary electric field. The auxiliary field is generated by two pairs of rod electrodes positioned adjacent and parallel to the line of flight of the spun fibre. The changes in shape of the deposition area and the degree of movement of the deposition area are quantified by optical scanning and image analysis. A linear response was observed between the magnitude of movement of the deposition area and voltage difference between the auxiliary and deposition electrodes. A squeezing effect which changed the aspect ratio of the deposition area was also observed to result from the application of symmetric electrical fields. Statistical analysis showed that the deflection and squeezing responses can be thought of as independent control actions. The results from this experiment suggest this particular application of superposition of electric fields could be used as to control the flight path of an electrospun fibre.

BACKGROUND: Public opposition to aerial application of sex pheromone for mating disruption of light-brown apple moth (LBAM), Epiphyas postvittana (Walk.), in California stopped its further use in the ca $ 74 million eradication programme in 2008, underscoring the need for other eradication tactics. It is demonstrated that pheromone-treated sterile Mediterranean fruit flies (medflies), Ceratitis capitata Wied., can disrupt communication in male moths. RESULTS: Medflies topically dosed with moth pheromone (E)-11-tetradecenyl acetate showed a no observed effect level (NOEL) of ∼10 µg fly−1, with increasing toxicity from 30 to 100 µg fly−1. Greater potency and longevity of attraction and lower mortality were achieved using microencapsulated pheromone. Releases of 1000 pheromone-treated medflies ha−1 prevented male moth catch to synthetic lures in treated 4 ha plots for 1 day in suburban Perth, Australia. Releases of ca 3000 pheromone-treated medflies ha−1 disrupted catch to single female moths in delta traps, and to synthetic pheromone lures. Percentage disruption on the first four nights was 95, 91, 82 and 85%. CONCLUSIONS: Disruption of moth catch using pheromone-treated medflies is a novel development that, with future improvement, might provide a socially acceptable approach for application of the insect mating disruption technique to control invasive insects in urban environments. Adequacy of payload and other issues require resolution. Copyright © 2011 Society of Chemical Industry

Bactericera cockerelli (the tomatopotato psyllid; TPP) and associated insects were monitored weekly in unsprayed potatoes at Pukekohe by using yellow sticky traps and sampling plants from late July 2009 until mid March 2010 TPP adult catches and egg and nymphal infestations were absent or low until mid December Other exotic and native psyllid species dominated trap catches until TPP populations increased markedly in mid January and peaked at 120 adults per trap in late February with egg numbers reaching 520 per plant a week later TPP nymphs peaked at 260 per plant in early February Micromus tasmaniae (brown lacewing) was common in spring and summer but Melanostoma fasciatum (small hover fly) became the dominant predator peaking at 162 eggs and 35 larvae per plant in mid January Naturally occurring predators appear to be important biological control agents of aphids small caterpillars and probably TPP on potatoes at Pukekohe

An adjustable action threshold that uses estimates of larval parasitism of Helicoverpa armigera (Hubner) in individual fields was assessed over three consecutive years in processing tomatoes in Hawke’s Bay, New Zealand. Tomato fields were monitored weekly for levels of infestation by H. armigera larvae. When infestation levels became of concern, either approaching or exceeding the standard action threshold of one larva per plant, collections of 30+ representative larvae were made. These larvae were measured and reared individually at 30 °C, and after 4 days rates of parasitism were estimated visually. From these data, spray recommendations were made using a formula that adjusted the action threshold to allow for mortality from parasitism. At harvest, damage assessments were made to validate these recommendations. Results showed that estimates of parasitism after 4 days were accurate predictors of final assessments of parasitism. Overall parasitism during the three seasons was 71%, confirming that the original threshold, which relies on about 50% parasitism, needed revision. The dominant parasitoid was Cotesia kazak, reared from 91% of all parasitized larvae over the 3 years. Microplitis croceipes and the self introduced polyphagous parasitoid Meteorus pulchricornis were reared from 4% and 5% of the parasitized larvae respectively. In 16 of 17 fields examined, the adjustable threshold kept fruit damage at harvest below the tolerated level of 5%. The single crop with excessive damage had only 0.5% fruit damage above this level. This adjustable threshold, which varied in this study from 1–8.3 larvae per plant, has been incorporated into an updated IPM programme and contributed to a 95% reduction in insecticide use.

This paper extends the theory on capture width, a commonly used performance indicator for a wave energy converter (WEC). The capture width of a linear WEC is shown to depend on two properties: the spectral power fraction (a property introduced in this paper), which depends entirely on the sea state, and the monochromatic capture width, which is determined by the geometry of the WEC and the chosen power take off (PTO) coefficients. Each of these properties is examined in detail. Capture width is shown to be a measure of how well these two properties coincide. A study of the effects of PTO control on the capture width suggests that geometry control, a form of control that has not been the focus of much academic research, despite its use in the wave energy industry, deserves more attention. The distinction between geometry control and PTO control is outlined. While capture width is a valuable design tool, its limitations must be recognised. The assumptions made in the formulation of capture width are listed, and its limitations as a tool for estimating annual power capture of a WEC are discussed.

A new mark-capture technique involving field applications of Bacillus thuringiensis Berliner (Bt) to study the dispersal of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated as a tool to improve information on the potential impact of insect pest dispersal on crop infestation and insecticide resistance. The acquisition and persistence of Bt on moths were characterized and potential contamination of moths from naturally occurring Bts was examined. This mark-capture technique was developed to mark larger numbers of moths than had been previously achieved with laboratory marking using fluorescent dyes in mark-release-recapture experiments. Applications of commercial preparations of Bt to 0.3 and 1.0 ha potato fields were estimated to have marked ca. 50 000 moths in each experiment. Pheromone trap catches of potato tuber moths in the Bt-sprayed fields and in potato fields at distances of ca. 80, 200, 350, and 750 m were assayed for the Bt marker using selective microbiological media and identification of characteristic Bt crystal inclusions. Marking rates of moths were 78-100% in the sprayed fields and, compared with our previous mark-release-recapture studies, marking at ca. 200 m was increased by 15-18-fold to >3.0 moths per trap. This capture rate allowed the calculation of a dispersal curve that improved the reliability of estimates of movement at farm-scale distances. These estimates indicated that 10% of the population dispersed to 240 m in 3 days, and suggested that moths can potentially disperse throughout a typical potato-growing area in one growing season. This level of dispersal has implications for the spread and management of potato tuber moth populations, especially if insecticide resistance is present.

Poly(vinyl alcohol) (PVOH) was electrospun using different methods to charge the polymer solution. A positive high voltage relative to the collecting electrode significantly increased the fibre deposition rate. Electron microscopy showed that approximately half of the increase in fibre mass was due to thicker fibres being deposited. The current flowing from the grounded electrode was measured to determine the charge carried on the PVOH jet. This showed that for a positive voltage charging condition there is a much larger current and hence more charge carriers generated in the PVOH solution. As a result, more mass is ejected from the Taylor cone, implying that a positive voltage also produces longer fibre for a given time period. We also tested whether different substrate materials caused any variation when the charging conditions were changed. Statistically significant variation between substrates was only found when the substrate was an insulator and was expected to support a high deposition rate. This confirms the view that the PVOH fibre arrives at the collecting electrode carrying a charge that must be neutralized, otherwise a repulsive charge will form where the fibre is deposited and some fibre will be lost to any alternative earth. In electrospraying, charge carriers are generated using associated redox reactions. Thus, for electrospinning a lack of symmetry in these reactions may result in the generation of different quantities of charge carriers in the PVOH solution and changes in the mass deposition rate of electrospun fibre.

Tasmanian brown lacewing, Micromus tasmaniae (Walker) (Neuroptera: Hemerobiidae), is an indigenous aphid predator in New Zealand and Australia. Lacewing mortality can result directly from contact with insecticides and/or indirectly from the consumption of insecticide-intoxicated prey. Laboratory bioassays were set up to examine the indirect non-target effects of insecticides on M. tasmaniae populations feeding on lettuce aphid, Nasonovia ribisnigri (Mosley). Larvae of M . tasmaniae were initially tested against three commonly used insecticides at two dose rates (approximate recommended field rate and half field rate). 1st to 4th instar aphids were fed on insecticide-treated lettuce for 24 h and then fed to 1st instar M. tasmaniae larvae. Pirimicarb (Pirimor ® 50) caused 30–40% mortality of M. tasmaniae larvae exposed at 1st instar for 3 days. Pymetrozine (Chess ® WG) showed less than 20% mortality, while imidacloprid (Confidor ® ) caused over 96% mortality of M. tasmaniae larvae over this period. A dose–response bioassay was then set-up to determine the impacts of lower doses of imidacloprid through until pupal development of M. tasmaniae larvae. There was no increase in mortality due to low doses (one sixth field rate or less) but from days three to eight, M. tasmaniae larvae showed significant evidence of delayed developmental rate from 3rd instar larvae into pupae. These results demonstrate that the use of imidacloprid, pirimicarb and pymetrozine for control of lettuce aphid has indirect non-target effects on M. tasmaniae. These effects need to be considered in developing Integrated Pest Management (IPM) systems for the New Zealand lettuce industry.

Tidal current turbines extract kinetic energy from tidal current in much the same way as wind turbines do with wind. Tidal current velocities are by nature slow and variable, whereas electricity generation typically requires fast and steady rotary motion. This article investigates the performance of a hydraulic transmission system based on Digital Displacement™ technology, which allows variable speed of the tidal current turbine rotor while maintaining constant generator shaft speed. The case study of a generic horizontal axis tidal turbine is considered. Control strategies based on rotor variable speed are derived to optimize yearly power generation and to cope with short-term variations in stream velocity.

Spodoptera litura (F.) and Helicoverpa armigera (Hubner) are potential non-target pests in Bacillus thuringiensis (Bt)-transformed potato and brassica crops that are currently being investigated as candidates for field release in New Zealand. The comparative susceptibility of these pests and two of their larval parasitoids to Bt toxins was examined using diets amended with commercial preparations of Bt sprays and Cry1Ac toxin preparations. Using concentrations that allowed survival of some of the parasitoids and their hosts, development and survival characteristics were compared at two rates of Dipel 2X, six rates of Cry1Ac, and two reduced-nutrition diets. For all these treatments, larval development of both parasitoids, Cotesia kazak (Telenga) and Meteorus pulchricornis (Wesmael), was delayed only when there was a significant impact on the host Lepidoptera. Survival of M. pulchricornis was unaffected even when the survival of S. litura larvae was mildly, but significantly, reduced. In H. armigera, Bt diets that caused severely reduced survival of the host were accompanied by reductions in survival of M. pulchricornis. Similar or increased levels of survival of C. kazak were noted in H. armigera that were fed less toxic Bt-amended diets. Poor survival of parasitoids on reduced-nutrition diets suggested that reduced nutrition had a comparatively greater effect on parasitoid survival than Cry1Ac toxins. Overall, when Bt was ingested at concentrations that had minor effects on development or survival of host larvae, there was no impact on either parasitoid species. Further experiments with specific Bt cultivars proposed for release are required to confirm that in any surviving larvae, the impacts of Bt on these parasitoids are likely to be fewer than the impacts on their non-target hosts.

Two parasitoids, Cotesia kazak (Telenga) and Microplitis croceipes (Cresson) have been successfully introduced into New Zealand to improve control of Helicoverpa armigera (Hubner), tomato fruitworm. C. kazak has spread throughout the North Island, but M. croceipes is restricted largely to its release areas in crops in the Gisborne and Hawke’s Bay regions in the East Coast of the North Island and in pine plantations in the central North Island. Rates of mortality of H. armigera from parasitism were studied in processing tomato crops where these parasitoids are a key component of an integrated pest management programme, and in sweet corn, lucerne and soybeans. C. kazak was the dominant parasitoid in tomatoes and soybeans. It emerged from small H. armigera larvae and usually killed the host before it caused major damage to fruit. M. croceipes emerged from larger host larvae than C. kazak . Death rates from parasitism of H. armigera larvae in tomatoes increased from less than 1% caused by native parasitoids prior to parasitoid introductions, to 25–45% in 1988 and 70–80% in 1996 following the establishment of both introduced parasitoids. M. croceipes was the most common parasitoid in lucerne and total mortality from all parasitoids was similar to that in tomatoes. Low rates of parasitism by C. kazak in sweet corn were attributed to the reduced penetration of the adult parasitoid into sweet corn fields and to the protection afforded by sweet corn when H. armigera larvae burrowed into corn cobs. The implementation of an IPM programme based partly on the effectiveness of these parasitoids has contributed to a decrease in insecticide applications to processing tomatoes.

A process tomato trial was undertaken at Pukekohe to investigate the interactions between tomato fruitworm, Helicoverpa armigera, and its larval parasitoids O the accidentally introduced generalist, Meteorus pulchricornis, and the introduced specialists, Cotesia kazak and Microplitis croceipes. Total mortality of larvae caused by parasitism was 75%, with M. pulchricornis, the dominant parasitoid, reared from 54% of parasitised larvae, and C. kazak and M. croceipes reared from 33% and 13% respectively. Cotesia kazak attacked smaller larvae than the other two species and was able to survive in the presence of the entomopathogenic fungus Zoophthora radicans late in the crop. These results contrast with those for corresponding parasitism in Hawke∑ s Bay where C. kazak is very dominant. It is concluded that the availability of alternative hosts in areas like Pukekohe is causing the displacement of C. kazak there but that this is having little impact on biocontrol of this pest in tomatoes.

The aim of this paper is to present a new method for the allocation of new generation capacity, which takes into account fault level constraints imposed by protection equipment such as switchgear. It simulates new generation capacities and connections to other networks using generators with quadratic cost functions. The coefficients of the cost functions express allocation preferences over connection points. The relation between capacity and subtransient reactance of generators is used during the estimation of fault currents. An iterative process allocates new capacity using optimal power flow mechanisms and readjusts capacity to bring fault currents within the specifications of switchgear. The method was tested on a 12-bus LV meshed network with three connection points for new capacity and one connection to an HV network. It resulted in significantly higher new generation capacity than existing first-come-first-served policies.

Mating of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was investigated in relation to the dispersal of males in laboratory and field trials. The effect of stimulating the flight of males to light sources in a large cage on their mating ability was estimated for three age groups, and compared with similar estimates for confined moths. Although the mating of males declined with ages of up to 15 days, simulated dispersal had no effect on subsequent mating when the males were paired with virgin females. The dispersal of male moths was also categorised by the initial flight activity of untethered moths to a light source. Scores for poor, moderate, and good flight provided a repeatable measure of initial male flight activity, but the degree of activity was not related to their subsequent mating ability. In the field, virgin female potato tuber moths were tethered at various distances from the edge of isolated potato crops and then dissected to determine their mating status. Female mating frequency averaged 75% at the crop margin, remained above 50% up to 200 m, and then declined to 19% at 360 m from the margin. Derivation of the mating probability for an individual male potato tuber moth confirmed earlier work by other researchers that has indicated a tendency for dispersal prior to mating, and that males retain their ability to mate as they disperse from a crop. The influence of dispersal and mating on gene flow between crops, and its potential effects on refuge size required to minimise the development of resistance to Bt transgenic potato crops was examined.

Limiting the emissions of greenhouse gases from power generation will depend, among other things, on the continuing and increased use of hydroelectric power. However, climate change itself may alter rainfall patterns, adversely affecting the financial viability of existing and potential hydro schemes. Previous work developed a methodology for quantifying the potential impact of climate change on the economics of hydropower schemes. Here, the analysis is extended to examine the potential for changes in project risk. A case study is presented that indicates that the applied climate change scenarios alter not only the mean financial performance of the scheme but also the financial risk facing it. Given that investors must balance project risk and reward, this finding has implications for the future provision of hydropower.

The use of pheromone traps was investigated as a monitoring tool to forewarn crop scouts of risk periods when diamondback moth (DBM; Plutella xylostella) larval numbers in crops are likely to increase to damaging levels We monitored traps at five brassica planting sites for 8 months and also counted numbers of DBM larvae on 50100 plants at each site Crops were scouted weekly and insecticide application decisions were made using the Crop amp; Food Research IPM programme Results showed that increases in moth trap catches predicted increases in larval infestations in three of four commercial crops in spring by 23 weeks and gave 2 weeks warning in four of five summer crops An epizootic of Zoophthora radicans caused a rapid decline in larval populations in mid to late January at all sites In these trials use of the IPM action thresholds led to a 75 reduction in insecticide use on vegetable brassica crops Overall pheromone traps were of limited value except in early spring because crops needed to be scouted regularly for other pests

Immature wheat grain in New Zealand is attacked sporadically by the native insect (bug), Nysius huttoni. This ‘bug-damaged wheat’ contains a bug salivary proteinase, and bread made from this wheat has a characteristically poor loaf volume and texture. Historical baking data suggest variations in wheat cultivar susceptibility to bug damage. This suggestion was tested in two trials (1992/1993 and 1993/1994) on immature wheat using nine or seven New Zealand cultivars and breeding lines enclosed together in nylon mesh cages with and without N. huttoni. Visible damage, bug-proteinase levels, electrophoretic protein patterns, and baking properties of the grain were analysed. Both trials showed that susceptibility to bug damage was significantly different amongst cultivars and breeding lines. The ranking of cultivar susceptibility was the same for the two trials, except for cv. Arawa, which was one of the most susceptible cultivars in the first trial, but one of the least susceptible in the second trial. Cultivars Domino and Oroua consistently showed less susceptibility to bug attack. The breeding line WW378 and the cultivar Otane were the most susceptible to bug attack. The high quality bread wheats (Otane, Oroua, Domino and Batten) were less susceptible to the effects of bug proteinase in baking than the poor baking quality wheats (Karamu, WW378, ASPS9927 and ASPS9928). Batten was significantly less susceptible than any other cultivar in test baking. There was no relationship between bug-damage susceptibility and grain characters such as colour, hardness and texture, or head characters such as shape, awns and waxiness.

Tidal energy has the potential to play a key role in meeting renewable energy targets set out by the United Kingdom (UK) government and devolved administrations. Attention has been drawn to this resource as a number of locations with high tidal current velocity have recently been leased by the Crown Estate for commercial development. Although tides are periodic and predictable, there are times when the current velocity is too low for any power generation. However, it has been proposed that a portfolio of diverse sites located around the UK will deliver a firm aggregate output due to the relative phasing of the tidal signal around the coast. This paper analyses whether firm tidal power is feasible with 'first generation' tidal current generators suitable for relatively shallow water, high velocity sites. This is achieved through development of realistic scenarios of tidal current energy industry development. These scenarios incorporate constraints relating to assessment of the economically harvestable resource, tidal technology potential and the practical limits to energy extraction dictated by environmental response and spatial availability of resource. The final scenario is capable of generating 17 TWh/year with an effective installed capacity of 7.8 GW, at an average capacity factor of 29.9% from 7 major locations. However, it is concluded that there is insufficient diversity between sites suitable for first generation tidal current energy schemes for a portfolio approach to deliver firm power generation. (C) 2012 Elsevier Ltd. All rights reserved.

Decarbonisation of the electricity system is driving a substantial growth in renewable energy developments. High penetration levels of intermittent and spatially variable renewable energy resources have brought about a need to evolve the passive operating principles of conventional electricity distribution networks. New solver architecture and a software environment have been developed to incorporate new active network management techniques and perform time-sequential power flow resolutions simulating future `real time' network operation. Critical evaluation of the technical, economic and environmental benefits of evolved system control can be performed in the new approach to power systems modelling. This work investigates the time-wise design choices of centralised and synergetic, community based network control schemes using steady state `optimal' network set points. Here we show that steady state analysis of new distribution network control schemes are unlikely to truly maximise the capacity, energy yield and system response of distribution networks. The system has shown conventional low frequency control scheduling to be outdated in dealing with enhanced penetrations of rapidly changing renewable energy resources. Transitioning to high resolution finite horizon control scheduling is equally inefficient as it introduces large levels of hysteresis and poor continuity of network control. A means is also discussed to evolve steady-state finite horizon distribution network control to real time receding horizon analysis. (8 pages)

This paper describes a pseudo-real time distribution network simulator developed to investigate the use of real time distribution system control presets to better integrate high levels of distributed energy resources into active distribution networks. A combination of historical and modelled generation profiles, along with varying demand patterns, are used to demonstrate the real time application and improved system response from active network management control strategies. (4 pages)

Optimal control of a wave energy converter (WEC) in polychromatic seas is possible only with accurate future knowledge of wave elevation, excitation force or WEC state. The required future knowledge is related to the bandwidth of the radiation damping, while the available future knowledge is related to the bandwidth of the wave spectrum. A new concept called premonition time is introduced, which is defined as the time by which the time-span of the required future knowledge exceeds that of the available future knowledge. The effect of the size of a WEC on the premonition time, and suitable methods for prediction of future state, are also discussed.

Environmental concerns, the need to diversify the energy mix, together with technology advances have made Distributed Generation (DG) increase worldwide over recent decades. One of the major and well-recognised benefits of DG is its ability to defer future demand-related investments, providing potentially significant savings and competitive advantage for regulated Distribution Network Operators (DNOs). In this paper an approach that considers the successive elimination method and multistage planning is proposed in order to quantify the investment deferral brought about by DG. Here, each required reinforcement and its implementation schedule affected by the connection of DG can be clearly identified by the DNO. A typical UK distribution network circuit is evaluated. Results show that characteristics of DG such as location, size, power factor and the commissioning time can result in significant reductions of the total planning costs. The investment deferral per MW of connected DG is also investigated as an index that could assist DNOs in evaluating the attractiveness of potential connection points as well as in quantifying the benefit produced by DG.

Regulators are aiming to incentivize developers and Distribution Network Operators to connect distributed generation (DG) to improve network environmental perform-ance and efficiency. A key question is whether these incentives will encourage both parties to connect DG. Here, multi-objective optimal power flow is used to simulate how the par-ties’ incentives affect their choice of DG capacity within the limits of the existing network. Using current UK incentives as a basis, this paper explores the costs, benefits and trade-offs associated with DG in terms of connection, losses and, in a simple fashion, network deferral.

With high levels of variable renewable generation in distribution or transmission systems, the application of demand and generation time series to power flow analysis can be advantageous. Demand data are often available from historic measurements, while renewable generation such as wind turbine output may be recorded or can be derived from resource measurements over the corresponding period of time. Power flow solutions with hourly time steps over a year or more can then be used to produce load duration curves for system components. This paper shows, by example, how utilities can use the method to determine overload conditions or to specify non-firm connection agreements for new generators.

With the rapid increase in distributed generation (DG), the issue of voltage regulation in the distribution network becomes more significant and centralized voltage control (or active network management) is one of the proposed methods.Alternative work on intelligent distributed voltage and reactive power control of DG has also demonstrated benefits in terms of the minimization of voltage variation and violations as well as the ability to connect larger generators to the distribution network. This paper uses optimal power flow to compare the two methods and shows that intelligent distributed voltage and reactive powercontrol of the DG gives similar results to those obtained by centralized management in terms of the potential for connecting increased capacities within existing networks.

One solution to reduce the extent of climate change is to replace fossil-fuelled electricity generation with renewable sources including hydropower. However, simultaneous changes in climate may alter the available hydropower resource, threatening the financial viability of schemes. To illustrate the potential problem, a sensitivity analysis is presented that considers the impact of altered precipitation and temperature on river flows, energy production and financial performance measures of a planned hydro scheme in Sub-Saharan Africa. The behaviour of the river basin was found to amplify changes in precipitation and, while the design and planned operational strategy of the station tended to moderate the impact, the overall financial impact remained significant. Comparison with (non-climate) project parameters indicated that financial performance, not surprisingly, depends strongly on discount rate and electricity sales price and that, importantly, it showed a similar sensitivity to precipitationchange and rising temperature. Critical changes in climate were identified in order to indicate the severity of climate change that could be tolerated before the project becomes financially non-viable.

Wave energy will have a key role in meeting renewable energy targets en route to a low carbon economy. However, in common with other renewables, it may be sensitive to changes in climate resulting from rising carbon emissions. Changes in wind patterns are widely anticipated, and this will ultimately alter wave regimes. Indeed, evidence indicates that wave heights have been changing over the last 40 years, although there is no proven link to global warming. Changes in the wave climate will affect wave energy conversion. Where the resource is restricted, there may be reductions in energy exports and, consequently, negative economic impacts. On the other hand, increased storm activity will increase installation survival risks. Here a study is presented that, for the first time, indicates the sensitivity of wave energy production and economics to changes in climate.

The capacity of distributed generation (DG) is set to increase significantly with much of the plant connecting to distribution networks. This paper briefly reviews the technical problems associated with the connection of DG plant at distribution-level and the mitigation strategies currently available. Further it examines the shortcomings of current connection practice in terms of the potential for inadvertently limiting network capability in absorbing new DG. Finally, it demonstrates the use of optimal power flow with a technique that could facilitate maximisation of renewable generation capacity in the deregulated electricity market.

The hydrological interdependence of plants in cascade hydro-electric systems means that operation of any one plant has an effect on water levels and storage at other plants in the system. Hydro plants may be dispatched to meet predicted demand, to trade electricity at a commercially opportune time, or to adjust water levels in the system. Hydrologically and commercially efficient operation of cascade systems requires that water resources and energy trading are managed simultaneously. This paper describes some of the principles of cascade water management and the development of an expert system which assists in the optimal scheduling of hydro plant within Scottish Hydro Electric plc's system.

There is widespread potential for generating modest amounts of hydroelectric power at water treatment plants in the United Kingdom water supply industry. This paper identifies some of the potential sources of mini-hydro power, reviews the applicable mechanical, electrical and control equipment and considers some of the factors influencing technical and economic viability of power generation at these sites. The institutional regulations applicable to new plants are also identified.

In recent intensive sampling of insecticidefree potatoes at Pukekohe several insect predators and spiders have been found in association with the new pest Bactericera cockerelli tomatopotato psyllid (TPP) Micromus tasmaniae (brown lacewing) Melanostoma fasciatum (small hover fly) Coccinella undecimpunctata (11spotted ladybird) and sheet web spiders (Linyphiidae) were collected from potatoes at Pukekohe Research Station and reared in the laboratory to assess their potential as predators against TPP nymphs Individual predators were presented every 24 h to a maximum of 10 TPP nymphs of different instars ranging from 2nd to 4th instar depending on the size of the predator All predator species fed on TPP nymphs and all predatory life stages were capable of consuming more than five nymphs per day Ongoing studies with these species show that all predatory life stages of all predatory species feed on all life stages of TPP Together with separate data on predator incidence these results suggest that naturally occurring predators are likely to be important biological control agents of TPP particularly early in the season when TPP infestations are low

Before new renewable generators can be connected to the electricity network, it is necessary to carefully evaluate the impact they will have. Firm connection agreements are based on snapshot assessments of the worst-case situation of maximum generation and minimum demand, which restrict renewable capacities despite infrequent occurrence. This work describes how time series of several renewable generation technologies together with demand can be applied to examine the opportunities and challenges offered by non-firm generation connections. It applies optimal power flow to extract maximum energy from available renewable resources while using curtailment of generation to maintain the network within thermal and voltage limits. By way of a case study of potential wind, wave and tidal current development in the Orkney Islands, Scotland, the analysis provides estimates for the degree of curtailment and consequent economic impact a renewable generator operating under non-firm connection may experience. The methods described provide a first-level analysis that could facilitate appraisal of non-firm connections at the planning stage by estimating the consequences of concurrent generation and demand as well as the frequency and duration of necessary curtailments.

The Jake Canyon reverse fault trends northwest for more than 18 mi along the northeastern flank of the Blacktail Mountains. Archean metamorphic rocks are displaced over Paleozoic carbonate strata along the northwestern part of the fault and are displaced over other Archean metamorphic rocks along the southeastern part. The Jake Canyon fault is separate and distinct from the Cenozoic Blacktail normal fault that marks the common boundary of the range and the valley to the northeast. Mineralizing hydrothermal fluids caused argillic and propylitic alteration along the Jake Canyon fault in the middle and southeastern parts of the mountain range. Fission-track ages were determined on apatite recovered from nine samples of propylitized gneiss and gneiss beyond the zone of hydrothermal alteration. The combined geologic and geochronologic evidence indicate that the ages of fault movement and the hydrothermal event that produced the mineralized, altered rock are Late Cretaceous.

Distributed generation capacity will increase significantly as a result of UK Government-led targets and incentives. Whereas the technical problems arising from distribution-level connections may be mitigated for individual connections, the anticipated connection volumes imply a potential risk of conflict between connections, in that inappropriately sized or located plant could constrain further development of the network and consequently threaten the achievement of renewable energy targets. One means of addressing this risk is to encourage development at sites that are more suitable and at the same time discouraging those at inappropriate ones. First of all network operators must be able to evaluate the available capacity on the system (i.e. the headroom). A technique is presented that facilitates such an analysis. Termed ‘reverse load-ability’, the approach models fixed-power factor distributed generation as negative loads and uses the optimal power flow to perform negative load shedding that effectively maximises capacity and identifies available headroom. The technique is applied to an extensive distribution and sub-transmission network. It rapidly identifies available headroom within the imposed thermal and voltage constraints. Furthermore, its use is demonstrated in examining the consequences of a sequence of connections in terms of the impact on available headroom and in sterilising the network.

The paper discusses the implications of the increasing capacity of synchronous generators at the remote ends of rural distribution networks where the line resistances are high and the X/R ratios are low. Local voltage variation is specifically examined and two methods of compensation are proposed. The first of them is a deterministic system that uses a set of rules to switch intelligently between voltage and power factor control modes, while the second is based on a fuzzy inference system that adjusts the reference setting of the automatic power factor controller in response to the terminal voltage. Extensive simulations have verified that the proposed approaches may increase the export of real power while maintaining voltage within the statutory limits.

This paper describes a wave-to-wire model of an array of wave energy converters developed in MATLAB/Simulink. The effects of connecting a 1MW wave farm to a weak, rural electricity network are investigated. Impacts of the wave farm on voltage quality are examined and both conventional and more intelligent control methods by which these impacts can be mitigated are discussed. The control methods compared are: constant voltage operation, constant power factor operation, On Load Tap Changing Transformer (OLTC) operation, automatic voltage and power factor controller (AVPFC) operation and fuzzy logic power factor controller operation. The applicability of these control methods are compared using certain indices - flicker severity index, voltage fluctuation index and global voltage regulation. Drawbacks of power factor control, voltage control and control using the OLTC transformer and the advantages of using more intelligent control methods, like the AVPFC or the fuzzy logic power factor controller, are established.

This paper describes the construction and test of a software model of a weak rural distribution network containing embedded water turbine driven synchronous generators (EGs). The characteristics of the network and its influence are related by development of the universal power circle diagram. The delivery of active and reactive power when the EG is operated purely in automatic power factor control (APFC) is compared with that when operated in automatic power factor control modified by voltage control (AVPFC). It is shown that this combined control enables increased EG dispatch within statutory network conditions.