Distributed generation

When it comes to incorporating Distributed Energy Resource (DER) activity, the supplier will need to construct half hour energy blocks with prices, representing the aggregated ‘offers’ from or contracts with customers to vary premises Export and Import. These can then be compared with the sale and purchase of half-hourly energy blocks and prices being tendered in the market by other parties. Any trading with DER is simply between the supplier and its customers, to modify the supplier’s account demands and thus its purchasing requirements within the market. The trades do not enter the industry settlement process and customer actions will be reconciled dependent on the framework for participation.

All major decisions affecting genset running profiles, principally commitment, are made in market timescales. However, the market framework is the trading of energy by account by half hour. This is not precise enough to facilitate efficient merit order operation of main plant by minimising on load and startup fossil fuel burn against more accurate forecasts of total system and group demands. Thus, the market price messages may not promote the best use of DER to avoid unnecessary running of marginal plants.

In the context of Directive on energy end-use efficiency and energy services, cogeneration and advanced technologies on energy conversion take a relevant role in the energy landscape.

Simultaneous generation of electrical and useful thermal energy (hot, cold, or both) is an obvious way to optimize the consumed energy efficiency. In the last decade, cogeneration has had, in a world level, a big deployment, thanks to the use of gas and the fact of taking advantage of biomass and other waste products energetically valuable. However, there are possibilities to extend cogeneration applications by means of new technologies of multiple generation of: electrical power, heat, cold, desalination and/or regeneration of water and chemical products in general.

The priority performances about this context are being centred in the development and researching of a distinguished group of electrical micro-generation technologies, which energetic benefits highlight because of a high global index of efficiency. In this group of advanced technologies Fuel Cells, Stirling Motor and Gas Microturbines are included.

This paper presents the current state of development of above mentioned advanced technologies, in the field of distributed generation, which are involved in cogeneration and poligeneration processes.

By J Paska

Nowadays, in many countries the increase of generating capacity takes place in small units of so-called distributed generation (DG), and among them in hybrid power (generating) systems (HPS). They use primary energy conventional sources as well as renewable energy sources (RES), and in many cases produce electricity and heat (CHP). It is very often that definition of distributed generation is connected with definition of renewable energy sources. Using of renewable energy sources is one of the crucial components of the sustainable development, giving rationale economic, ecological and social effects. Support for development of renewable energy sources utilization became very important objective within the European Union. In this article present state and perspectives of using of renewable energy sources and distributed generation in Poland are depicted as well as the main tools promoting their development and utilization.

By J F Christin et al

In today’s mission critical computing environments, achieving a fault tolerant infrastructure is essential to smooth operation. Unfortunately, many users don’t completely grasp the full meaning of fault tolerance as a comprehensive solution with a defined architecture to maximize operating dependability. All too often, it is viewed as a collection of fault-mitigating products that can end up being more of a Band-Aid than a truly effective strategy for process improvement.

By J A Martinez-Velasco et al

Characteristics of voltage sags caused by faults in distribution networks depend on the design of the protection system and the coordination between the different protective devices. The presence of distributed generation (DG) changes the radial nature of distribution systems, so it can affect the performance of the protection system, and consequently the characteristics of voltage sags. In addition, DG will help to maintain the during-fault voltages of healthy phases. This paper explores the impact that DG can have on voltage sags characteristics by means of a small test distribution network and presents a simple method to compare and rank the performance of protection systems.

Smart has for some time been the buzz-word in energy circles. We should act energy-smart, we should have smart meters and smart grids. In the US we now hear several of the candidates for presidency claim that they want to support building of smart grids. In Europe the Commission has issued programmes for research on smart grids. But how smart can a grid really be and how will the grid show its’ smartness?

There seem to be at least three different perspectives of smartness that you want the grid to apply:
·         Economic Use of resources
·         Service improvement for utilities
·         Technical upgrading of functions

No doubt new technology and technology in development can make networks (grids) work better than only lining up electrons in order to be delivered through the wires. But can all the wishes be fulfilled or will some have priority over the others?

By R Hesse et al

Demands in the area of electrical energy generation and distribution, as a result of energy policies, are leading to far reaching changes in the structure of the energy supply, which is characterised, on the one hand, by the substitution of conventional power stations by renewable energy generation, a decision which has already been made, and, on the other hand, by the changeover from centralised to decentralised energy generation. From an electrical engineering point of view, a new situation will arise for consumers concerning security of supply and power quality, which calls for further technical measures by the grid operators to ensure that the increasingly stringent supply criteria can be met.

This article describes a new power electronics based approach which allows a grid compatible integration of predominantly renewable electricity generators even in weak grids making them appear to be electromechanical synchronous machines. As a consequence, all the proven properties of this type of machine which have so far defined the grid continue to do so, even when integrating photovoltaic or wind energy. These properties include, for instance, interaction between grid and generator as in a remote power dispatch, reaction to transients as well as the full electrical effects of a rotating mass. In addition, this new development can be operated in such a way that it provides primary reserve allowing, from a grid point of view, electricity generators such as wind and PV to be regarded as conventional power stations.

Investment in renewable fuels is booming. Last year, solar and wind are reported to have broken through the 100 BUSD wall and reached 117 BUSD, a growth over 3 years that averages more than 40% per year. Reportedly, there is no slow-down in sight - on the contrary! Growth 2007 was 20 BUSD above predicted values.

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To counterbalance unexpected fluctuations in electricity production or consumption.What if users consume more electrical energy than scheduled? Or less? Since liberalization, the Transmission System Operator is responsible for keeping the balance between generation and consumption. This is done by the so called 'spinning reserve'. The following minute lectures present you a short overview on the spinning reserve, how it is defined, and how it operates.

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From this Friday September 28 onwards, from 14h00 - 15h00 Europe Daylight Time, you can meet weekly with the Leonardo ENERGY team and other users of the Leonardo initiative inside the 3D forum. We will animate the forum with short presentations, you can power-chat (or talk by VoIP) with us or others, exchange business cards, or browse the pavillons of the 3D world.

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Petra de Boer, Jillis Raadschelders, KEMA

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Summary

A flow battery is a type of battery that can be designed very flexibly. It can be designed for high power applications as well for high-capacity electricity storage. Other types of electricity storage, like conventional batteries or flywheels, do not show this flexibility and therefore have some limitations to their applications. Flywheels are mostly used for short durations (<5 minutes) and high power storage (> 500 kW), while batteries are used for lower power (<500 kW) and long durations (> 1 hour). Flow batteries are used for large-scale projects that require high-capacity storage and also high power storage, for instance for grid-connected electricity storage at wind farms.

In a flow battery the battery is charged and discharged by a (reversible) chemical reaction between the two liquid electrolytes of the battery. These electrolytes are not stored in the power cell of the battery as in a conventional battery, but in separated storage tanks. During operation these electrolytes are pumped through the electro-chemical reactor, in which a chemical redox reaction takes place and electricity is produced. Due to this storage of the electrolytes outside the reactor, the specifications of the battery are flexible; the power and the energy content of the system can be specified separately. It is very easy to increase the amount of electrolytes or to replace the electrolytes. Moreover, the design of the power cell can be optimized for the power rating needed, as this is independent of the amount of electrolyte used.

The development of flow batteries has reached the stage of demonstration projects. Small- scale products are already available on a commercial basis, while for the larger-scale projects demonstrations have been started. These demonstration projects prove the technology and show that it can be applied on a large scale. The costs of the technology will decrease as soon as the technology becomes available as a commercial product. Based on current feasibility studies, the life cycle costs will be lower than those of the alternatives, based on the capital costs and the expected life time. Flow batteries can be very attractive for future applications, especially for large-scale applications, like peak power support at wind farms or distribution level balancing.

By Peter Vaessen and Davy Thielens, KEMA

This Application Note discusses DG in the context of the energy agenda at Global, Regional and National levels. It discusses the state of the Kyoto protocol and how it relates to European Commission policy as laid out in directives, and National implementation measures. Possible future developments, including the fate of Kyoto and its successors and new technologies, are discussed.

After reading this Application Note, the reader will have a clear view of global and European policies and national incentives for specific countries regarding DG and will easily be able to find regional specific policy and incentives.

Related:

Webinar on this application note - June 20, 15h00 - 16h00 Europe Daylight Time

This new webcast introduces the subject of distributed generation.

Distributed Generation (DG) and Renewable Energy Sources (RES) have attracted a lot of attention in Europe. Both are considered to be important in increasing the security of energy supplies by decreasing the dependency on imported fossil fuels and in reducing the emissions of greenhouse gases. Distributed generation refers to the local generation of electricity and (in the case of a cogeneration system) heat for industrial processes or space heating, etc. The economics of DG and RES depend on many factors. The main cost items are the initial investments, fuel prices, energy prices (electricity and heat) and the cost of connecting to the grid. Biomass options generally give the lowest cost electricity of all RES-based options. On-shore wind and hydro capacity come second. The most expensive option is solar cells. However, many countries have stimulation measures for renewable systems, including solar cells. The viability of DG and RES depends largely on regulations and stimulation measures. This is a matter of EU and national policies. A stable political course with regard to stimulation measures for DG and RES is necessary to encourage serious investment by market parties in additional DG and RES capacity.

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Maurits van Laarhoven, KEMA Consulting

The focus of this application note will be on standards related to the hardware, integration and performance of renewable energy systems (as discussed in the other application notes to Chapter 8: Cogen, wind, BIPV and integration & interconnection).

The purpose will be to give the reader a first introduction in related standards regarding renewable energy generation by wind, photovoltaic or cogeneration. The aim is to inform the reader (for example a potential buyer or investor) about the standards applicable to renewable energy generation.

The need to standardize a material, product or system can present itself for a number of reasons: the manufacturer’s desire to have interchangeable products, public concerns about quality and compatibility, or consumer protection measures enacted by the government. A standard is a document that interested parties have agreed upon, whether it refers to the width of a railway track, or the way a solar PV installation should perform. Standards are needed so that a product can be defined technically, in terms of its various characteristics and measures of its performance. Standards also define how this should be measured and tested, and what criteria apply for passing or failing these tests.

By Roald de Graaf and Johan Enslin

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Summary

Historically, each generation of power plants has tended to be larger than its predecessor. In the 1980s, however, the size of newly constructed generating units began to decrease. The relatively small new generating units are usually connected to distribution networks, which are not designed to host power generators. It is expected that distributed generation (DG) will transform distribution networks in the future. This paper discusses the opportunities offered by DG, but also the consequences of increased DG penetration and elaborates on some of the steps to be taken to facilitate further growth. It is concluded that for a further increase of DG penetration two key issues need to be resolved: new business models need to be developed and implemented and interconnection standards for power and data interfaces need to be further developed and harmonised.

By Jan Bloem, KEMA Consulting

Traditional electricity networks were built to transport electrical energy generated by large, centrally placed, power production units to consumers. In this model, the generators are all connected to the transmission level. Lower level distribution networks then distribute energy to consumers. Distributed Generation (DG) units cannot be connected to the transmission level because it is uneconomic to do so and they are connected to the distribution system at either medium (MV) or low voltage (LV) level. These systems were designed for power to flow only from top to bottom – from transmission level to consumer – and can accept only a limited amount of generation without major change. Studies indicate that this level is in the region of 10-15%.

This Application Note discusses how the future wide scale adoption of DG can be accommodated in existing networks.