Gas Balancing Rules Must Take into account the Trade-off between Offering Pipeline Transport and Pipeline Flexibility in Liberalized Gas Markets

This paper analyses the value and cost of line-pack flexibility in liberalized gas markets through the examination of the techno-economic characteristics of gas transport pipelines and the trade-offs between the different ways to use the infrastructure: transport and flexibility. Line-pack flexibility is becoming increasingly important as a tool to balance gas supply and demand over different periods. In the European liberalized market context, a monopolist unbundled network operator offers regulated transport services and flexibility (balancing) services according to the network code and the balancing rules. Therefore, gas policy makers should understand the role and consequences of line-pack regulation. The analysis shows that the line-pack flexibility service has an important economic value for the shippers and the TSO. Furthermore, the analysis identifies distorting effects in the gas market due to inadequate regulation of line-pack flexibility: by disregarding the fixed cost of the flexibility in the balancing rules, the overall efficiency of the gas system is decreased. Because a full market based approach to line-pack pricing is unlikely, a framework is presented to calculate a cost reflective price for pipeline flexibility based on the trade-offs and opportunity costs between the right to use the line-pack flexibility and the provision of transport services.Massachusetts Institute of Technology. Center for Energy and Environmental Policy Research

Gas Market Distorting Effects of Imbalanced Gas Balancing Rules: Inefficient Regulation of Pipeline Flexibility

This paper analyzes the value and cost of line-pack flexibility in liberalized gas markets through examination of the techno-economic characteristics of gas transport pipelines and the trade-offs between different ways to use the infrastructure: transport and flexibility. Line-pack flexibility is becoming increasingly important as a tool to balance gas supply and demand over different periods. In the European liberalized market context, a monopolist unbundled network operator offers regulated transport services and flexibility (balancing) services according to the network code and balancing rules. Therefore, gas policy makers should understand the role and consequences of line-pack regulation. The analysis shows that the line-pack flexibility service has an important economic value for the shippers and the TSO. Furthermore, the analysis identifies distorting effects in the gas market due to inadequate regulation of line-pack flexibility: by disregarding the sunk costs of flexibility in the balancing rules, the overall efficiency of the gas system is decreased. Finally, the analysis demonstrates that the actual costs of line-pack flexibility are related to the peak cumulative imbalance throughout the balancing period. Any price for pipeline flexibility should, therefore, be based on the related trade-off between the right to use the line-pack flexibility and the provision of transport services

On physics of a hypothetical core disruptive accident in Multipurpose hYbrid Research Reactor for High-tech Applications – MYRRHA

The sensitivity of the reactivity of a fast reactor core to changes in its geometry and/or fuel relocation calls for particular attention with regard to criticality events. A category of these events, the so-called Core Disruptive Accidents (CDAs), are intensively studied in the safety assessment of Sodium-cooled Fast Reactors (SFRs), and more recently also in the case of other systems. Differences between SFRs and Heavy Liquid Metal Fast Reactors (HLMFRs) are significant and therefore warrant an understanding of phenomena and the development of models specific to HLMFRs. This paper provides a qualitative overview of the physics relevant to the investigation of a CDA in HLMFR, with a particular application to the Multipurpose hYbrid Research Reactor for High-tech Applications – MYRRHA. At first, a core compaction mechanism viable for an HLMFR has been postulated. In what follows, simulation by an already existing severe accidents code, as well as modelling based on fundamental physics and engineering, have been performed. It is demonstrated that, for a linear insertion of reactivity due to hypothetical core compaction, the reversal of reactivity evolution happens due to the Doppler effect and the thermal expansion of core materials. Subsequent expansion by fuel melting terminates the prompt-critical event and makes the system delayed-supercritical. Successive fuel and/or coolant boiling is responsible for the hydrodynamic disassembly of the core and it therefore effectively terminates the transient

On physics of a hypothetical core disruptive accident in Multipurpose hYbrid Research Reactor for High-tech Applications – MYRRHA

The sensitivity of the reactivity of a fast reactor core to changes in its geometry and/or fuel relocation calls for particular attention with regard to criticality events. A category of these events, the so-called Core Disruptive Accidents (CDAs), are intensively studied in the safety assessment of Sodium-cooled Fast Reactors (SFRs), and more recently also in the case of other systems. Differences between SFRs and Heavy Liquid Metal Fast Reactors (HLMFRs) are significant and therefore warrant an understanding of phenomena and the development of models specific to HLMFRs. This paper provides a qualitative overview of the physics relevant to the investigation of a CDA in HLMFR, with a particular application to the Multipurpose hYbrid Research Reactor for High-tech Applications – MYRRHA. At first, a core compaction mechanism viable for an HLMFR has been postulated. In what follows, simulation by an already existing severe accidents code, as well as modelling based on fundamental physics and engineering, have been performed. It is demonstrated that, for a linear insertion of reactivity due to hypothetical core compaction, the reversal of reactivity evolution happens due to the Doppler effect and the thermal expansion of core materials. Subsequent expansion by fuel melting terminates the prompt-critical event and makes the system delayed-supercritical. Successive fuel and/or coolant boiling is responsible for the hydrodynamic disassembly of the core and it therefore effectively terminates the transient

Statistical description of the error on wind power forecasts via a Lévy a-stable distribution

As the share of wind power in the electricity system rises, the limited predictability of wind power generation becomes increasingly critical for operating a reliable electricity system. In most operational & economic models, the wind power forecast error (WPFE) is often assumed to have a Gaussian or so-called B-distribution. However, these distributions are not suited to fully describe the skewed and heavy-tailed character of WPFE data. In this paper, the Lévy a-stable distribution is proposed as an improved description of the WPFE. Based on 6 years of historical wind power data, three forecast scenarios with forecast horizons ranging from 1 to 24 hours are simulated via a persistence approach. The Lévy a-stable distribution models the WPFE better than the Gaussian or so-called B-distribution, especially for short term forecasts. In a case study, an analysis of historical WPFE data showed improvements over the Gaussian and B-distribution between 137 and 567% in terms of cumulative squared residuals. The method presented allows to quantify the probability of a certain error, given a certain wind power forecast. This new statistical description of the WPFE can hold important information for short term economic & operational (reliability) studies in the field of wind power

Short-term CO2 abatement in the European power sector : 2005-2006

This paper provides an estimate of short-term abatement of CO2 emissions through fuel switching in the European power sector in response to the CO2 price imposed by the EU Emissions Trading Scheme (EU ETS) in 2005 and 2006. The estimate is based on the use of a highly detailed simulation model of the European power sector in which abatement is the difference between simulations of actual conditions with and without the observed CO2 price. We estimate that the cumulative abatement over this period was about 53 million metric tons. The paper also explains the complex relationship between abatement and daily, weekly, and seasonal variations in load, relative fuel prices, and the price of CO2 allowances

LONG TERM UNIT COMMITMENT OPTIMISATION FOR LARGE POWER SYSTEMS; UNIT DECOMMITMENT VERSUS ADVANCED PRIORITY LISTING ABSTRACT

Unit Commitment is a term used for the strategic choice in which of the available power plants have to be on-line at every time. Most Unit Commitment models described in the literature are specially designed for the power utilities. They are typical short term models for relatively small power systems. Apart from practical use in the utilities themselves, Unit Commitment is also implemented in the broader context of electricity generation modelling. For these purposes, however, the power systems can be much larger and the time scale more extended. Since Unit Commitment is only a minor part of these models, the calculation time dedicated to Unit Commitment has to be limited, possibly sacrificing somewhat on accuracy. Two methods are compared. Unit Decommitment which is considered completely accurate and Advanced Priority Listing which is less accurate but also less complicated. Simulations demonstrate that Unit Decommitment is slightly more accurate (0.03 to 0.6%) but takes much more calculation time (5 to 10 times more) than Advanced Priority Listing

Impact of large amounts of wind power on the operation of an electricity generation system : Belgian case study

Wind power can have considerable impacts on the operation of electricity generation systems. Energy from wind power replaces other forms of electricity generation, thereby lowering overall fuel costs and greenhouse gas (GHG) emissions. However, the intermittency of wind power, reflected in its variability and relative unpredictability restrains the full potential benefits of wind power. The variable nature of wind power requires power plants to be ready for bridging moments of low wind power output. The occurrence of forecast errors for wind speed necessitates sufficient reserve capacity in the system, which cannot be used for other useful purposes. These forecast errors inevitably cause efficiency losses in the operation of the system. To analyse the extent of these impacts, the Belgian electricity generation system is taken as a case and investigated on different aspects such as technical limitations for wind power integration and cost and GHG emissions’ reduction potential of wind power under different circumstances

Effect of the accuracy of price forecasting on profit in a price based unit commitment

This paper discusses and quantifies the so-called loss of profit (i.e., the sub-optimality of profit) that can be expected in a Price Based Unit Commitment (PBUC), when incorrect price forecasts are used. For this purpose, a PBUC model has been developed and utilized, using Mixed Integer Linear Programming (MILP). Simulations are used to determine the relationship between the Mean Absolute Percentage Error (MAPE) of a certain price forecast and the loss of profit, for four different types of power plants. A Combined Cycle (CC) power plant and a pumped storage unit show highest sensitivity to incorrect forecasts. A price forecast with a MAPE of 15%, on average, yields 13.8% and 12.1% profit loss, respectively. A classic thermal power plant (coal fired) and cascade hydro unit are less affected by incorrect forecasts, with only 2.4% and 2.0% profit loss, respectively, at the same price forecast MAPE. This paper further demonstrates that if price forecasts show an average bias (upward or downward), using the MAPE as measure of the price forecast might not be sufficient to quantify profit loss properly. Profit loss in this case has been determined as a function of both shift and MAPE of the price forecast