"Forecast analysis of the supply demand balance for summer"
Forecast analysis of the supply - demand balance for summer 2007 1 Analysis of the supply - demand balance for summer 2007: For temperatures close to seasonal norms, the forecast supply-demand balance for electricity does not present any particular difficulties throughout the summer of 2007, although the early part of the period is set to be slightly less favourable than the previous year. However, a sustained heatwave with temperatures 7°C above seasonal norms would see generation fall and consumption rise, putting the stability of that balance at risk. In such a scenario, the analysis shows that demand for electricity in France would be covered with a balance based on low net exports. The analysis also looked at a deliberately extreme scenario, with sustained temperatures 9° above seasonal norms, in which case the covering of demand could need additional supplies on the European market. 1. BACKGROUND The real time management of the Supply-Demand balance in mainland France is the responsibility of the French Transmission System Operator, RTE. Based on information supplied by the various players involved in the French power network, RTE establishes a forecast for demand (French internal consumption and exports) and supply (French generation and imports). In accordance with the government's "Heatwave Plan", RTE now draws up a forecast study of the supply- demand balance and network performance during the summer period, in order to anticipate any difficulties that might affect operation in the event of a spell of unseasonably hot weather. This document includes a summary of the work carried out by RTE in preparation for summer 2007. 2 2. METHOD EMPLOYED BY RTE RTE conducts a technical analysis of forecast operating reserves on the French power system, for the period between mid-June and late September. This involves a study of the physical risk that the supply of power will be insufficient to fully satisfy demand. The extent to which this physical risk is covered is examined in terms of power levels, which are calculated at the consumption peak for each week of the summer period. RTE uses the information sent by all French market players (availability of generating plants, exchanges planned for the period studied, consumption shading possibilities as set down in contracts between suppliers and their customers) and compares it with its own consumption forecasts, based on statistical models. During the initial phase of the study, RTE assesses the physical risk that supply will be insufficient to cover demand on the French power system, based on a technical criterion: the "1% risk" 1 . This equates to reserves corresponding to a probability of 1% that "exceptional" measures will be required. These exceptional measures are as follows, activated in decreasing order of priority: exceptional offers on the balancing mechanism 2 , very rapid increases (even temporary overloading) in the power produced by certain generating units (conventional thermal and hydro-electric), decreases in voltage, and lastly, power cuts. Forecast reserves are assessed in a probabilistic way, based on several hundred different scenarios, combining contingencies affecting generating facilities (rates of unavailability of various generating units, records of water stocks), with those affecting consumption (temperature records). The average reserve resulting from these scenarios, compared with the "1% risk", is then used to determine the "maximum" balance of cross-border exchanges required to satisfy that criterion. Next, the consequences of a heatwave are considered and two stress scenarios of increasing severity are established. These determinist scenarios affect both electricity consumption, which rises due to the intensive use of air-conditioning, and supply, which drops due to a reduction in output by hydro-electric plants and restrictions on certain nuclear and conventional thermal plants. For each weekly consumption peak during the period studied, the results of simulations are used to determine the balance of exchanges on borders needed to satisfy network safety criteria. 1 Link with appendix 1"The basic about Systeme operation / A.1.5 Operating margins and balancing mechanism" of the Power System Reliability Memento - Edition 2004 (page 214) 2Link with appendix 1"The basic about Systeme operation / A.1.5.2 Balancing Mechanism" of the Power System Reliability Memento - Edition 2004 (page 215) 3 3. FORECAST SITUATION FOR TEMPERATURES CLOSE TO SEASONAL NORMS The figure below shows the maximum balance of cross-border exchanges needed to satisfy the 1% risk criterion, at temperatures close to the seasonal norm, for every week of the summer period. Balance of exchanges needed to satisfy the 1% risk criterion 14000 13000 12000 11000 10000 9000 8000 ( MW ) 7000 6000 5000 4000 3000 2000 1000 0 Week 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 x x x June July August September Over the entire period studied, forecast generation capacities should be sufficient not just to cover demand in metropolitan France, but also to give French generators the option of exporting energy on the European markets. 4 4. HEATWAVE SCENARIOS To assess the consequences of a heatwave, RTE has developed two "stress" scenarios affecting consumption and generating facilities. These scenarios are based on the phenomena observed during the heatwaves in August 2003 and July 2006, and identify the sites at which generation was reduced to comply with legislation on the temperature of the cooling water released by plants. High temperatures Consumption calculated with temperatures 7° above seasonal norms (1% probability of occurrence). Reductions in generation at nuclear and conventional thermal sites subject to environmental restrictions, equivalent to those recorded in 2006. Reduction in available capacity of hydro-electric units. Reduction in wind generation. Extreme Consumption calculated with temperatures 9° above seasonal norms (0.1% temperatures probability of occurrence 0.1%). Reductions in generation at nuclear and conventional thermal sites equivalent to the maximum reductions recorded during the 2003 and 2006 heatwaves. More severe reduction in available capacity of hydro-electric units. More severe reduction in wind generation. 4.1 Impact on consumption To reflect the high sensitivity of electricity consumption to temperatures (due to the use of air-conditioning and ventilation equipment), the scenarios include a rise in electricity consumption. This rise in consumption has been based on an analysis of experience from previous summers: the temperature gradient is evaluated at 380MW/°C at the consumption peak around 1pm (rise in consumption associated with a temperature rise of 1°C). The graph below shows our consumption forecasts for 2007 under normal conditions (NC), and with temperatures 7°C and 9°C above the norm: 5 Consumption at weekly peak Consumption under NC Consumption at +7°C Consumption at +9°C 64 000 62 000 Consumption Consumption 60 000 increase for +7°C increase for +9°C 58 000 ( MW ) 56 000 54 000 52 000 50 000 Week 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 x x x June July August September 4.2 Impact on supply During periods of high temperatures, the output of certain thermal plants must be reduced to comply with local regulations and environmental requirements. Similarly, hydro-electric and wind generation may also be affected. In the scenarios adopted, the hypotheses for reductions in generation were developed by RTE on the basis of actual figures recorded during previous summer periods, especially the heatwaves of 2003 and 2006, and the risk of reductions in the power supplied by generators. On average, the generation reductions forecast are 7,400 MW under the "High Temperatures" scenario and 11,600 MW under the "Extreme Temperatures" scenario. 5. FORECAST SITUATION FOR HEATWAVE SCENARIOS The scenarios adopted by RTE for summer 2007 can be used to determine the "maximum" balance of cross- border exchanges needed to satisfy safety criteria and maintain the supply-demand balance. 6 This power level, calculated for every week of the period concerned, represents the difference between the available capacity of the French generating fleet on the one hand, and on the other hand total consumption (minus shading identified by certain players) and capacity reserves 3 contractually agreed by RTE with French electricity generators, needed to operate the power system safely. Balance of cross-border exchanges needed to satisfy safety criteria EXTREME scenario HIGH TEMP. scenario 8000 7000 6000 Exports ( MW ) 5000 4000 3000 2000 1000 0 Imports ( MW ) -1000 -2000 -3000 -4000 Week 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 x x x June July August September For the "high temperatures" scenario, the graph indicates that the forecast supply-demand balance for mainland France should be maintained, provided the export balance does not exceed values between 1800 and 3000 MW in late June and early July, the period when the balance comes under the most severe strain. In the "extreme temperatures" scenario, France would actually be a net importer of electricity during the summer period, apart from the first three weeks of August. During such a period, French market suppliers could apply extra consumption shading measures to their customer portfolios; these elements are not known by RTE at this stage and are therefore not taken into account. Finally, before taking exceptional measures, RTE could also draw on existing provisions: accepting demand response offers made by French consumers or by international consumers via the balancing mechanism to reduce their consumption, and activating backup contracts signed with other European TSOs. If these preventive measures nonetheless prove insufficient, RTE alerts the government of the risk that supply will be interrupted, and takes action in real time to limit the impact on the power system. 3 Link with appendix 1"The basic about Systeme operation / A.1.5 Operating margins and balancing mechanism" of the Power System Reliability Memento - Edition 2004 (page 214) 7