Microgen 2008 Conference

The 1st International Conference and Workshop in Microgeneration Technologies and Applications held in the National Arts Centre, Ottawa, Canada, attracted more than 100 delegates from industry and academia from all over the globe. The Conference provided an ideal international forum within which to present the work of the HDPS Consortium. To this end, the Consortium sponsored a special session featuring 8 papers from Consortium members and two guest speakers. These covered a variety of research topics ranging from electric load analysis through to power electronic interfaces for micro-generation devices.

Conference website

The First International Conference and Workshop on Micro-Cogeneration Technologies and Applications “Micro-Cogen 2008” held at the National Arts Centre in Ottawa Canada from April 29 - May 1, 2008. A forum for presenting the latest research, development and demonstration results in a broad range of small cogeneration technologies including technical and policy analyses, deployment strategies, comparative analysis, and studies on sustainability and societal and environmental impacts.

An Overview of the Highly Distributed Power System

A potential future direction of the electricity supply industry in the United Kingdom is to move away from relying almost exclusively on large transmission connected thermal power stations, and to accommodate smaller, more environmentally sustainable forms of generation connected across the network.

D. Pudjianto, A.A. Shakoor, P. Djapic, C. Ramsay, G. Strbac, "System Level Implications of HDPS", First International Conference and Workshop on Micro-Cogeneration Technologies and Applications National Arts Centre, Ottawa, Ontario, April - May 2008

Using a range of techniques and models this paper analyses the implications of increasing penetration of Renewable Energy Sources (RES) and Distributed Generation (DG) on the integral electricity system. From the generation perspective, as the level of intermittent and inflexible generation increases, the system will value DG with a high capacity credit and opportunities for flexible operation. Our models explore the ability of RES and DG technologies to displace incumbent generation capacity and quantify the value of flexibility in the emerging system. From a network perspective, key findings obtained from some case studies show the positive impact of some DG technologies on distribution network losses and deferral of network reinforcement where output is well aligned with peak demand conditions.

M. Thomson, "High-Density Micro-Generation in UK Distribution Networks", International Conference and Workshop on Micro-Cogeneration Technologies and Applications, Ottawa, Canada, 2008.

The widespread introduction of micro-generation in homes and small commercial premises could have significant technical impacts on the operation of local distribution networks. Detailed modelling of such generation, particularly micro-cogeneration (known in the UK as micro combined heat and power – micro- CHP) and solar photovoltaics (PV) has been completed and a discussion of the key results is presented. The modelling covers a significant area of UK distribution network (over 1000 properties) and employs unbalanced load-flow analysis within a time-domain simulation framework. Both generation and demand are represented with a one-minute time resolution and are stochastic and diverse as expected in real networks. The results include quantification of voltage rise, reverse power flow, altered transformer and line loadings and altered losses.

S.R.Allen, G.P. Hammond, H. Harajli, C.I. Jones, M.C. McManus, and A.B. Winnett, "Integrated Appraisal of Micro-Generators: Methods and Applications", Proc. Micro-Cogen 2008, Ottawa, Canada, 29 April - 1 May 2008, Paper MG2008-SG-005, 8pp

A range, or ‘toolkit’, of integrated appraisal techniques have been utilised to study the performance of various domestic micro-generators. Energy, environmental impact and cost-benefit analysis methods, employed on a ‘whole systems’ or life-cycle basis, are described. The application of the appraisal techniques is illustrated via the evaluation of three micro-generators: a micro- wind turbine with 1.7m rotor diameter and power rating 600W at 12m/s; a generic 15m2, 2.1kWp, monocrystalline solar photovoltaic array; and a solar hot water system based upon a 2.8m2 collector. They are estimated to typically provide 25–49% of the average UK household electricity or hot water demand, and have energy paybacks well within their estimated lifetimes. Significant life-cycle environmental impacts are associated with the use of aluminium to produce the solar hot water unit and micro-wind turbine. All three domestic micro-generators were found to be uncompetitive in the present UK liberalised market. Increased production volumes, and technical improvements in the next generation of devices, such as their manufacturing processes and operational efficiencies, are necessary in order to improve their economic performance.

Power Eelectronic Interface for Distributed and Microgeneration

Many of the technologies being deployed for distributed and micro generation require the use of a power electronic interface to convert their electrical output to a form compatible with the AC network. The design of this component and its associated control will determine how this generation is seen by the network. This area presents challenges for the power electronic system. In practice the grid connection may be poorly characterized and subject to significant transient effects Added to this, interface performance is subject to strict regulation. This paper reviews the key building blocks which form the power electronic interface. Design considerations and limits are identified and discussed. Current developments and research themes are identified.

Co-Generation and Operating Network Cells

In Denmark several thousands of generators are connected to the distribution system (10 kV and 0.4 kV). The production from these generators many times exceeds the load. The generators can be divided into two types, Wind turbines and CHP generators. These generators have one thing in common, the power system they are connected to, has never been designed to accommodate so many generators. In Denmark we now expect a third type of generators: the micro- generators. This time we want to be prepared. Denmark therefore now participates in a lot of research and full scale demonstration projects. A key concept in along these lines is the “Network Cell”.

Integrating Distributed Resources with the Automated Distribution System

This paper describes the EPRI distribution automation roadmap.. Important areas include the communication and information systems to support automation, new approaches for system simulation that can provide the basis for both real time optimization and advanced planning applications, and control strategies that combine distributed controls with advanced centralized controls and management. These development will enable integration of renewables and distributed resources that include new technologies like PHEV and demand response for optimizing both local and system wide performance.

D. Beyer and N.J. Kelly, "Modelling the Behaviour of Domestic Micro-Co-Generation under Different Operating Regimes and with Variable Thermal Buffering", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

This paper describes the preliminary outcomes from a comprehensive modelling exercise that explored the performance of domestic cogeneration for different UK housing types under different operational scenarios, and with and without thermal buffering. The simulation results indicate that thermal buffering has a dramatic effect on the performance and operational characteristics of micro-cogeneration devices however, due to standing losses in the thermal buffering, carbon emissions levels show only small variations.

N. J. Kelly, S. Galloway I. Elders R.M.Tumilty and G.M.Burt, "Modelling the Imapct of Micro Generation on the Electrical Distribution System", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

In the UK and elsewhere there is considerable debate as to the future form of the electricity distribution system. The coming years will see a rise in the amount of micro-generation connected to the network at low voltages and the emergence of highly-distributed power systems (HDPS). However, there is considerable uncertainty as to the impact that this micro-generation will have on the quality of power supplied to our homes or to the stability of the electricity system as a whole. To address these engineering challenges the UK Engineering and Physical Sciences Research Council (EPSRC) is funding a three year research programme featuring a multi-disciplinary team from a variety of UK Universities: Supergen HDPS. This paper documents one piece of work emerging from the consortium, where a multi-tool approach is used to analyse the impact of micro-generation on the electricity system. This used a building simulation tool to produce electrical generation profiles for domestic cogeneration device models. These, along with profiles produced for other micro-generation technology models and electrical load profiles are then replicated and aggregated using a customised statistical approach. The profiles were then used as boundary conditions for a set of electrical load flow simulations on a model of a section of real network, where the number of micro- generators was varied according to different scenarios for the future of the UK electricity grid. The results indicate that a significant number of micro-generation devices can be accommodated before any power quality problems arise, however this is dependent upon maintaining a robust central grid.

N.J. Kelly, A. Ferguson, B. Griffith and A. Weber, "The Development of a Generic Systems-Level Model for Combustion-Based Domestic Cogeneration", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

A long established and appropriate means to evaluate the energy performance of buildings and their energy systems is through the use of dynamic building simulation tools. However, until now, only a very limited number of micro-cogeneration device models have been available to the modelling community and generally these have not been appropriate for use within building simulation codes. This paper describes work undertaken within the International Energy Agency’s Energy Conservation in Building and Community Systems Annex 42 to address this problem through the development of a generic, combustion- based cogeneration device model that is suitable for integration within building simulation tools and can be used to simulate the variety of Internal Combustion Engine (ICE) and Stirling Engine (SE) cogeneration devices that are and will be available for integration into dwellings.

C.N.Jardine, "Synthesis of high resolution domestic electricity load profiles", First International Conference and Workshop on Micro-Cogeneration Technologies and Applications National Arts Centre, Ottawa, Ontario, 2008

A novel method of synthesising high-resolution domestic electricity loads has been developed in order to provide the necessary accuracy to a forthcoming network model. It is based on measured 30 minute resolution data of household loads and average appliance usage. The model utilises an occupancy model, which can serve as a proxy for both non- baseload electricity demand and heat demand. Synthesised ‘activity’ profiles were then generated for a sample of 1000 homes. The 30 minute appliance data provides the probability that an appliance will be on. With knowledge of appliance ownership levels, typical appliance power and the ‘activity’ profiles, appliance turn-on events can be triggered, and load profiles built up for each dwelling. Behavioural characteristics, relating to the number of appliances owned, rated power of these appliances, and how often they are used, are also included to replicate the variability in electricity consumption observed between houses.

L. Peeters, N.J. Kelly and W. D`haeseleer, "Thermal comfort in residential buildings with water based heating systems: a tool for selecting appropriate heat emitters when using micro-cogeneration", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

As a consequence of people becoming more aware of their impact on the environment, there is an increasing demand for low energy buildings. Forced by regulation, building envelopes are improving and heating and cooling systems with higher efficiencies are being installed. The public are willing to embrace these new technologies, as long as they do not affect the quality of their indoor environment. In this paper, an introduction to research on the realisation of the indoor thermal comfort in residential buildings with water based, low-energy heating systems is given. The basis for this work is a more realistic definition of comfort temperatures for residential buildings. Subsequently, appropriate heat emitters to realise that thermal comfort in an efficient way are identified, taking into account the limitations of the production system under consideration. An example of a µ-cogeneration system is presented as a case study.