Small Electrical Systems Research Articles

Optimal investment by large consumers in an electricity market with generator market power

The investment decisions of energy-intensive consumers can alter the balance of supply and demand in an electricity market. In particular, they can increase the market power of incumbent generators such that prices may increase as a consequence of their investments. Whilst it is therefore intuitive that such investors will wish to consider their effects on the market, it is a challenging problem analytically and one that has been under-researched. In general, the problem can be manifest in any supply chain where demand-side investments influence endogenous price formation in the intermediate product markets. Theoretically, we show how the presence of producer market power decreases demand-side investments and then, computationally we formulate a quad-level program to model the operational implications for a demand-side investor in more detail. With an innovative reduction in complexity to a bilevel model, an efficient solution algorithm for the optimal investment by a demand-side investor is facilitated. We demonstrate computability on a small scale electricity system and the results confirm the theory.

Tilt-related alignment issues in miniature micromechanical on-wafer electrical probes composed of multiple flexible microcantilevers

Some new issues concerning the contacting and positioning of small electrical microelectromechanical systems (MEMS) probes based on multiple, flexible microcantilevers are presented here. A tilt error, associated with the lateral probe roll, means that contact touchdown occurs sequentially in different cantilevers upon increasing probe overtravel. To understand the relationship between probe overtravel, tip skate, tip planarity, tip tangency, and contact force in the different contacts, the relationship between mechanical bending and torsion of the flexible cantilevers needs to be accounted for. The study reveals the conditions for achieving contact planarity and desired contact force, as well as the identification of a new ‘differential skate error’ contact misalignment associated with such MEMS probes based on multiple, flexible microcantilevers. This misalignment leads to a ‘differential contact force error’ which has implications for electrical contact quality. An experimental scale model probe based on three cantilevers is used to test the modelling—the results agree well with the predictions of the model. Interestingly, the experiments revealed an effect not accounted for in the modelling; this ‘twist error’ resulted in the cantilever lead edge not being parallel to the touchdown plane. The findings may be useful for engineers involved with the automatic control positioning of such emerging miniature probes, especially in terms of the impact of probe positioning errors.

Electricity sector reforms and cost efficiency: The case of small electricity systems in Sub-Sahara Africa

The financial viability of Sub-Sahara Africa (SSA) electricity sectors has become a central energy policy issue in recent years. This follows persistent under-recovery of costs which are amongst some of the highest in the world. Discussions, however, focus on tariff and utility reforms and inadequately on costs efficiency and the role of broader sector reforms in persistently high costs. Through a synthesis of reform theories and case studies and using small electricity systems as a surrogate for liberalized electricity sectors without competitive markets, this paper examines the connection between sector reforms and costs. It brings an economic perspective to the discussion on utility financial performance in SSA electricity systems and the need for a holistic policy approach for sustainable cost-recovery. In this, we recommend the promotion of mobile power plants to facilitate contestability in generation and need for non-island small systems to participate in regional power markets to neutralize the scale limitations of their autarkic demand. Utilities and regulatory agencies should form platforms to share information on cost opportunities and possibilities to inform procurement designs and regulatory benchmarks. Regional markets could partner with national governments to develop subsidy schemes such as Contracts for Differences to remove rigidities imposed by national power purchasing contracts to promote deeper participation of small systems in regional power markets. Yardstick competition in the distribution segment remains viable in many small electricity systems and should be pursued at the regional level in the short run to medium term and at the national levels in the long term following deconcentration and the introduction of private sector participation.

Dynamical large deviations of linear diffusions.

Linear diffusions are used to model a large number of stochastic processes in physics, including small mechanical and electrical systems perturbed by thermal noise, as well as Brownian particles controlled by electrical and optical forces. Here we use techniques from large deviation theory to study the statistics of time-integrated functionals of linear diffusions, considering three classes of functionals or observables relevant for nonequilibrium systems which involve linear or quadratic integrals of the state in time. For these, we derive exact results for the scaled cumulant generating function and the rate function, characterizing the fluctuations of observables in the long-time limit, and study in an exact way the set of paths or effective process that underlies these fluctuations. The results give a complete description of how fluctuations arise in linear diffusions in terms of effective forces that remain linear in the state or, alternatively, in terms of fluctuating densities and currents that solve Riccati-type equations. We illustrate these results using two common nonequilibrium models, namely, transverse diffusions in two dimensions involving a nonconservative rotating force, and two interacting particles in contact with heat baths at different temperatures.

Energy-efficient and reconfigurable complementary filter based on analog–digital hybrid computing with SnS2 memtransistor

Sensor fusion is a widely exploited technique that combines data from two or more sensors to improve the accuracy to a level that cannot be achieved using a single sensor alone. Algorithms for sensor fusion are generally executed on conventional digital computing platforms; however, these algorithms impose a burden on small electrical systems with limited battery capacities and computing resources. In this study, we demonstrated an analog–digital hybrid computing platform based on an SnS2 memtransistor for energy-efficient and reconfigurable sensor fusion with a complementary filter algorithm. We experimentally verified that the power consumption of our hybrid computing-based complementary filter is only half that of the traditional software-based complementary filter, even with the same accuracy.

Independent power producers and deregulation in an island based small electricity system: The case of Papua New Guinea

The small island economy of Papua New Guinea (PNG) is facing severe electricity shortages and is therefore turning to implementing broader power sector reforms as a vehicle to attract private capital and investments in electricity generation. This study, based on a case-study approach, revisits the reform progress and plans in the electricity sector of PNG alongside the development and integration of IPPs in its small power system. Lessons of reform experiences and IPPs integration are drawn from three other smaller systems of Nepal, Nicaragua and the Northern Territory of Australia including stakeholder consultations, which includes two IPPs of PNG. We find a widening gap between reform ‘theory’ and ‘practice’ in the PNG power sector. Cost reflective pricing is implemented while cost recovery is never achieved by the vertically integrated state-owned utility and the insolvency of this state-owned single buyer poses the greatest perceived revenue risk to the IPPs. This lack of revenue reimbursement to the IPPs by the single buyer is a barrier towards attracting private capital into electricity generation. We recommend that strong political will and strengthening of institutional arrangements are urgent reform measures to attract private capital in power generation as political instability continue.

Small Electrical, Mechanical, and Biomechanical Systems of Electromagnetic Radiation

Small Electrical, Mechanical, and Biomechanical Systems of Electromagnetic Radiation

High efficiency high temperature heat extraction from porous media reciprocal flow burner: Time-averaged model

The high temperature heat extraction from a porous media reciprocal flow burner (RFB) is studied numerically. In RFB, the air/fuel mixture flow direction is switched periodically to contain and sustain combustion. High temperature heat extraction is essential for the efficient operation of small electrical and thermal systems based on thermoelectric generators, Stirling engines and micro-turbines. In this paper, the efficiency of the heat extraction is studied for different extraction locations, temperatures and equivalence ratios. An 1-D time-averaged model is developed and validated to represent a RFB and to further predict the behavior of the burner. Optimization on the burner’s geometry is also performed to increase the heat extraction efficiency.

Mitigation of DOCR miscoordination through distance relays and non-standard overcurrent curves

This article presents the application of non-standardized inverse-time curves and distance relays to solve the lack of sensitivity of relays during overcurrent relay coordination. The inclusion of distance relays to replace the insensitive overcurrent is proposed, the effect of underreaching by infeed is considered. Directional overcurrent relays very frequently act as backup protection in sub-transmition networks when line differential relays or pilot protection are used as primary protection. Thus, the directional overcurrent relays (DOCR) coordination application should be evaluated not only in small electrical systems but also in large and meshed networks. The model used of overcurrent relay considers five adjustable settings to enhance the coordination when distance relays are considered. The proposed method reduces the number of relays that do not coordinate, this allows to obtain results with better implementation. The results show a performance improvement in overcurrent relay coordination in several highly interconnected IEEE systems.

Complementary Generation Based on Solar Power and Rain Power in Sponge City

Aiming at improving the environment and the problem that how to effectively use rainwater collected in the construction of a sponge city, a scheme was proposed to generate electricity by rainwater potential energy on the roof and solar power during dry weathers. When it’s raining, the amount of rainwater controlled by the intelligent level control system and discharge device enters the system through a designed collector. After passing the packet filter and pressure pipeline, the rainwater potential energy is converted into electrical energy through a hydroelectric generator and finally stored in a water reservoir. The electrical energy is stored in a battery. When there’s no rain, solar energy is stored by a solar panel and a high-efficiency light tracking system to provide water working system or a small resident electrical system with electrical energy in the sponge city. Compared with thermal power generation, they do not cause environmental pollution. As a consequence, the two mechanisms complement each other in time and space to achieve the goals of environmental protection, energy conservation and emission reduction.

Small systems, big targets: Power sector reforms and renewable energy in small systems

There is some consensus that the traditional energy-only electricity markets, where prices are based on system marginal cost, cannot function efficiently with both fossil fuels and renewables, resulting in market disruptions and price volatility. Consequently, much effort has been focused on how to integrate these different resources in larger and mature electricity systems such as the use of capacity markets in addition to energy-only markets. This paper argues that the effectiveness of competition is limited by the size of an electricity system and there is a threshold size (and associated characteristics such as tropical locations, lack of access, and the prevalence of remote communities of consumers) below which competition will not produce the expected outcomes. This paper contributes to the policy discourse by discussing the reform of small electricity systems to integrate renewable energy via the means of three case studies: Nicaragua, El Salvador, and Australia's Northern Territory. The paper concludes that electricity reforms and renewables can be complementary in small systems when supported by appropriate instruments and incentives. We draw policy lessons for other small systems that are pursuing a triad of objectives including electricity reform, large-scale renewables development and improving energy access.

Small Systems, Big Targets: Power Sector Reforms and Renewable Energy Development in Small Electricity Systems

The dominant focus of much policy attention of late has been on the suitability of electricity market reform carried out under the ‘standard’ or prescriptive approach – the end point of which is market liberalization – for the integration of intermittent renewables. There is now a growing consensus around the argument that traditional energy-only electricity markets where prices are based on system marginal cost cannot function efficiently with both fossil fuels and renewables, potentially resulting in market disruptions and price volatility. Consequently, most policy discussion has focused on finding ways to successfully integrate the two through adopting advanced competitive solutions (such as the use of capacity markets in addition to energy-only markets) in larger systems. We however argue that the effectiveness of competition is limited by the size of the system – i.e., there is a minimum threshold size (and other characteristics such as tropical locations, lack of access, and the prevalence of remote consumers) under which competition will not produce expected outcomes, and require distinctive policy solutions. This paper contributes to the policy discourse by discussing the reform of small electricity systems to integrate renewable energy via the means of three case studies: Nicaragua, El Salvador, and their application to Australia’s Northern Territory. The paper draws some policy lessons that can be considered for other small electricity systems in island economies and territories across Africa, the Caribbean, and the Asia-Pacific, that are pursuing a triad of objectives including electricity sector reform, large-scale renewables development and improving energy access.

Water sources for cyanobacteria below desert rocks in the Negev Desert determined by conductivity

We present year round meteorological and conductivity measurements of colonized hypolithic rocks in the Arava Valley, Negev Desert, Israel. The data indicate that while dew is common in the Negev it is not an important source of moisture for hypolithic organisms at this site. The dominance of cyanobacteria in the hypolithic community is consistent with predictions that cyanobacteria are confined to habitats supplied by rain. To monitor the presence of liquid water under the small Negev rocks we developed and tested a simple field conductivity system based on two wires placed about 0.5 cm apart. Based on 21 replicates recorded for one year in the Negev we conclude that in natural rains (0.25 mm to 6 mm) the variability between sensor readings is between 20 and 60% decreasing with increasing rain amount. We conclude that the simple small electrical conductivity system described here can be used effectively to monitor liquid water levels in lithic habitats. However, the natural variability of these sensors indicates that several replicates should be deployed. The results and method presented have use in arid desert reclamation programs.

11,8-100% Rural Renewable Energy and Power Supply and its Influence on the Luxembourgish Power System

Abstract Currently, the majority of countries tries to reduce their dependency on fossil fuels by the introduction of renewable resources in their energy systems. In the following the relatively small Luxembourgish electricity system is analysed (0.55 Mio Inhabitants). Current power-system-models mainly focus on larger systems, due to the unavailability of specific consumption-data. Prices and effects on the Luxembourgish power system of different supply scenarios for rural-private households are analysed. A linear optimisation for the minimum-cost of the power-supply of a village with the following renewable energy resources: wind- (max.100 kW), solar-PV- and hydrokinetic-power is made. The electricity-demand scales with the number of inhabitants and agricultural-consumers. The wind-power-potential differs with the location of the village. The solar-radiation is assumed to be the equal over the country, due to the small size of approximately 80 by 50 km. The hydrokinetic turbines complete the supply where a village is located close to a river. The minimum cost of the specific village power-supply is the result of the optimization. The installation- and maintenance-cost of each renewable technology are considered. The whole number of a rural Luxembourgish model villages private households is considered and their electricity contribution to the system is estimated for different renewable energy supply scenarios, namely from 20% to 100% renewable-energy-scenarios. For each scenario the power exchanged from the village to the grid is calculated in 15-min-steps for 9-years, the amount differs widely with the number of applied generation technologies. Due to the high share of imported electricity of about 80% in the recent years, every consideration of national power generation does not harm the supply security. Luxembourg is a good model country to analyse the high share of distributed, renewable generators, due to its structure of rural and civic regions and their effects on a central European region with a high electricity-consumption.

Comparative impacts of wind and photovoltaic generation on energy storage for small islanded electricity systems

This paper addresses the annual energy storage requirements of small islanded electricity systems with wind and photovoltaic (PV) generation, using hourly demand and resource data for a range of locations in New Zealand. Normalised storage capacities with respect to annual demand for six locations with winter-peaking demand profiles were lower for wind generation than for PV generation, with an average PV:wind storage ratio of 1.768:1. For two summer-peaking demand profiles, normalised storage capacities were lower for PV generation, with storage ratios of 0.613:1 and 0.455:1. When the sensitivity of storage was modelled for winter-peaking demand profiles, average storage ratios were reduced. Hybrid wind/PV systems had lower storage capacity requirements than for wind generation alone for two locations. Peak power for storage charging was generally greater with PV generation than with wind generation, and peak charging power increased for the hybrid systems. The results are compared with those for country-scale electricity systems, and measures for minimising storage capacity are discussed. It is proposed that modelling of storage capacity requirements should be included in the design process at the earliest possible stage, and that new policy settings may be required to facilitate a transition to energy storage in fully renewable electricity systems.

Reliability of Divided Small Electric Energy System

Reliability is one of the most important factors of electrical energy system. This paper presents analysis of reliability of electrical energy system and divided small electrical energy system. To meet stated requirements of reliability is needed to increase energy supply reliability by increasing equipment reliability, distributing energy generation and creating smaller electric energy systems during fault period. The small electrical energy system creation impact to energy supply reliability has been investigated for defined divided electrical energy system during occurrence of a fault. The main reliability parameters of electrical equipment have been identified and calculated. Reliability of different small electrical energy system regimes has calculated and compared. DOI: http://dx.doi.org/10.5755/j01.eee.19.10.2727

Reforming small electricity systems under political instability: The case of Nepal

This paper assesses the issues and options in reforming small electricity sector systems in general while citing Nepal as a specific case. Political instability and increasing electricity demand are two major complicating factors in power sector reform of small systems such as that of Nepal. Lessons from international experience suggest that measures such as cost-reflecting pricing, restructuring and independent regulation are important for the success of reforms. In small systems, the creation of an independent regulatory authority is more important than unbundling of the sector. In the present context of Nepal accounting separation of the main activities may be a pragmatic restructuring approach given the present political and market condition. As the systems gradually grow larger, vertical separation of the system and horizontal splitting of the generation segment and competition in organised wholesale market followed by privatisation remains an option in the long run.

How to make a European integrated market in small and isolated electricity systems? The case of the Canary Islands

This paper presents a geographic dimension not often studied in the dynamics of creating an internal market for electricity within the European Union, namely the case of small European electricity systems like those found on the Greek islands of Cyprus and Crete. Our question, then, is how to achieve a suitable internal market for electricity in small and isolated systems. To address this issue, we identify the main problems to be overcome by introducing a methodology in which the Canary Islands experience is taken as a case study for understanding the challenges in creating an “EU-like market for electricity”. Our results show that the design of the vertical industrial structure and the figure of the grid operator and its attributes are key features for the proper operation of any electrical system. We also stress the minor roles of other possible options to achieve this EU-compatible market by highlighting first, in the wholesale market, the call-for-tender solution to introduce more generation and the risk of using safety requirements as barriers to entry in these small markets, and second, in the supply activities, the potential problems of an improperly regulated tariff scheme.

Electricity industry reforms in smaller European countries and the Nordic experience

Under its 1996 Electricity Directive, revised and strengthened in 2003, the European Commission requires Member States to reform their electricity industries along competitive lines. While the provisions of the Directive seem strong, there are ways countries can meet them without introducing real competition. A particular problem is the lack of will amongst Member States and the Commission to reduce the market power of dominant companies. Amongst the countries with small electrical systems, outside the Nordic region, national systems are still usually dominated by one or two integrated companies. However, in the Nordic region, reforms seem to have been successful, merging the four countries' systems into one market. This apparent success is based on a combination of several factors specific to the region, such as the dominance of hydro-electric power and public ownership. In one key respect, stimulation of new capacity, the reforms are still unproven. Hong Kong is now considering the future of its electricity industry after current arrangements expire in 2008 and there is pressure to move to a competitive model. Experience from small electricity systems in Europe suggests that it would be unjustifiably risky to abandon the proven monopoly model in favour of an unproven competitive model.

Rosetta: semantic support for model-centered systems-level design

With the advent of system-on-chip (SoC) technology, the design of small electrical systems has become a systems engineering task. Such tasks require working at high levels of abstraction to build systems by either integrating information from various design domains or modeling different aspects of the same component. Designers of traditional computer-based systems usually rely on component-based techniques that parallel the physical architecture. The model-based approach encompasses the component-centered approach, treating structural decomposition as a single model in the overall hierarchy. Model-centered semantics and languages let designers concentrate on the data, computation, or communication models that describe complex computer-based SoC requirements. Appropriate design semantics specify each system aspect, and the designer assembles those aspects into models to define complete systems and components. The developers of Rosetta, a heterogeneous systems-level modeling language that supports predictive design analysis, have identified mechanisms for defining and composing models that specify multiple domains of interest from many perspectives. Rosetta requirements and domains define test cases and generate abstract vectors for each test scenario. Several analysis tools are under development for transforming Rosetta into existing analysis environments, and the authors describe their authors are also developing native analysis tools for symbolic verification and simulation environments. The authors use Rosetta to provide computation models for customized digital and mixed-signal system-specification environments. Other domains to support, optical and microelectrical mechanical systems specifications are under consideration.