DTI Centre for Distributed Generation and Sustainable Electrical Energy Transmission Investment, Pricing and Access in Systems with DG Goran Strbac, Danny Pudjianto, Charlotte Ramsay Presentation to TADG 19 December 2006 1
DTI Centre for DG & SEE • Role : to provide fundamental research in support of Government targets on renewables and other distributed generation and to provide quantitative assessments to inform government policy • Focus : Solutions for cost effective integration of DG in the UK electricity system • Contributors : Imperial College, University of Manchester, University of Strathclyde • Collaboration : Executive steering committee of representatives from 28 companies operating in the UK electricity sector • Relevant contributions : – Methodologies for new on- and off-shore T&D network security standards – Evaluation of economic efficiency of new grid code requirements and opportunities for new technologies – Cost effective integration of wind energy into the GB system – DUoS and TNUoS pricing than includes DG 2
Executive Summary • For the development of arrangements for Transmission Access of DG, the framework that provides the consistency between Transmission Investment, Transmission Access and Transmission pricing needs to considered (developed). • Concept of TEC (way in which it is being implemented and interpreted) may have significant limitations, and in its present form does not provide appropriate framework for DG – No direct relation between TEC and the need for transmission investment (driven by DG) due to inability to deal with diversity of DG outputs – TEC does not facilitate cost reflectivity in systems with DG: we demonstrate that different DG technologies have different requirements for transmission network capacity and investment – Pricing based on TEC may not be cost reflective – TEC could lead to inefficient system operation – TEC could lead to overinvestment in transmission (access to transmission network should be shared between conventional plant and DG, but TEC does not support economic operation of the system) 3
TEC Framework TEC and TEC and TEC and cost reflectivity of efficiency of efficiency of system TNUoS charging network investment operation mechanism 4
Importance of SQSS • Transmission Supply Quality and Security Standards (SQSS) define need for investment – SQSS a reasonably proxy to network design and investment for system with conventional generator technologies (electricity demand driven production), treats all generation in the same manner. – Implementation of the SQSS • Peak demand conditions relevant for design • At peak demand all generators tend to run and this broadly coincides with maximum flows across the main transmission network, i.e. network design is broadly peak demand driven • Every generator connected to a particular busbar drives the same amount of transmission network investment (as all run during the max demand period) 5
Network planning (and) investment: system with conventional generation and DG • Methodology for transmission network design with DG yet to be developed • All UK work demonstrates that wind power drives less investment than conventional plant – National Grid (updated GB SQSS) scaling factor 60% – SKM wind scaling factor 20% – DG & SEE scaling factor about 40% • Consequence: Wind and conventional generation should share transmission capacity – On windy days, wind generation would be a major user of the interconnector, while on non-wind days conventional plant should use the capacity. • Effect of diversity in outputs of generators of different technologies is of key significance for efficient network design and investment 6
TEC and network investment • No direct relationship between TEC and network investment – TEC could be relevant for connection to the main interconnected system – TEC not directly relevant for design of the main interconnected network in systems with different generation technologies (i.e. DG) – There is significant diversity in operation of DG technologies, such as CHP and wind energy – The need for transmission capacity is not determined by the total installed capacity of this generation as the assumption that all DG generators run at full output, at the same time is not credible – What matters is not the installed capacity of generation (or maximum output of individual generator - TEC) but the impact it makes on the demand for network investment, which is driven by the pattern of operation, i.e. the extent to which generation production coincides with peak flows. • TEC does not support the economically efficient sharing of network capacity between different generation technologies 7
TEC and TNUoS • Charges for use of transmission network should not only be location specific, but should be technology specific (time of use critical for diversity) • It is discriminatory not to discriminate between different generation technologies • National Grid SQSS differentiate between the need for investment driven by different generation technologies, but TNUoS charges do not 8
TEC and efficiency of system operation • Generators that purchase TEC less than their installed generation capacity are prevented from accessing transmission network even if the network is not constrained • This is inefficient as the SRMC of transmission is nearly zero in an unconstrained network and hence access should not be prevented • The way in which TEC is implemented could cause increases in generation cost and electricity prices 9
Expanding concept of TEC to DG • For the development of arrangements for Transmission Access of DG, the framework that provides the consistency between Transmission Investment, Transmission Access and Transmission Pricing needs to considered (developed). • Concept of TEC (way in which it is being implemented and interpreted) may have significant limitations, and in its present form does not provide appropriate framework for DG – Aggregated DG output that is associated with a GSP (or a GSP Group) that is relevant for Transmission System Investment is not equal to the sum of the maximum outputs of individual DG units (and maximum individual outputs cannot be directly linked with the design of transmission network) – Pricing of DG with respect to individual TEC may not be cost reflective – Preventing DG units to generate above their individual TEC is inefficient • An agent could facilitate the evaluation of relevant aggregated output of a number of DG units (together with demand) – Consistency with TNUoS arrangements 10
DTI Centre for Distributed Generation and Sustainable Electrical Energy Transmission Investment, Pricing and Access, in Systems with DG Goran Strbac, Danny Pudjianto, Charlotte Ramsay Presentation to TADG 19 December 2006 11
Recommend
More recommend
