Energy Recovery Workshop Madrid, September, 29, 2015 Regenerative braking and the different traction systems Ignacio González and Eduardo Pilo Spanish Railways Foundation
Index 1. Introduction 2. Traction systems and energy recovery 3. Practical evaluation of the energy recovery in three study cases 4. Conclusions
Introduction (1/2) The efficiency of regenerative braking depends on the reachability of a consumer (another train, an ESS, the grid, etc.) for the regenerated energy. The closer, the better. The characteristics of each system determine this reachability : Topologies more or less meshed, Directionality of the substations reversible or not, The type of current AC or DC etc.
Introduction (2/2) This presentation describes the energy flows in the railway infrastructure of 3 european countries (UK, Sweden and Spain) in order to provide an overview of the impact of regenerative braking This evaluation has been performed in the WP1 of the FP7 Project Merlin, based on the infomation provided by the partners for year 2011 and using a common approach.
1. Introduction 2. Traction systems and energy recovery 3. Practical evaluation of the energy recovery in three study cases 4. Conclusions
Traction systems (1/3): AC 50Hz System Catenary split into independent sectors Each sector connected to the grid with a transformer AC grid is always receptive Public grid (3-phase AC 50Hz) Catenary Connected to the grid with transformers a bidirectional power flow is always possible Short isolated sections (30-50 km) lower probability of feeding other trains when regenerating
Traction systems (2/3): AC16.7 Hz system Fed from dedicated power plants or from the public grid (by means of converter stations) Power plant G May be supplied directly by dedicated power plants no bidirectional flow is possible CS Public grid (3-phase AC 50Hz) Railway Transmission Grid (1-phase, 16.6Hz, 110-132kV) AC grid is always receptive CS Catenary Catenary is virtually continuous higher probability of feeding other trains when regenerating Railway transmission grid higher probability of feeding other trains when regenerating, at longer distances May be connected to the grid with converter stations a bidirectional power flow is sometimes possible
Traction systems (3/3): DC System Fed from the power grid (typically distribution grids) by means of electronic converters Some bidirectionnal converters Good! Public grid (3-phase AC 50Hz) Converters are normally unidirectional lower probability of feeding other trains in off-peak periods When catenary not segmented higher probability of feeding other trains when braking. BUT only at shorter distances Catenary
1. Introduction 2. Traction systems and energy recovery 3. Practical evaluation of the energy recovery in three study cases 4. Conclusions
Practical evaluation of the energy flows: Network Rail (United Kingdom) Consummed energy, by input voltage (2011) 22 kv 0% 11 kv 2% 400 kv 13% 275 kv 2% Energy returned to grid, by input voltage (2011) 66 kv; 0,01% 33 kv; 0,00% 11 kv; 0,00% 22 kv; 0,00% 400 kv; 0,40% 33 kv 35% 275 kv; 0,06% 66 kv 8% 2x25 kv 4% 650 V 1% 132 kv 40% Consummed energy, by catenary voltage (2011) 132 kv; 1,25% Energy returned to grid, by catenary voltage (2011) 650 V; 0,00% 2x25 kv; 0,12% 750 V; 0,00% 750 V 43% Electrification capability (km of electrified track) Network-wide 2011/12 AC overhead 8,049 3rd rail 650/ 750V DC 4,469 Dual AC, overhead/3rd rail DC 35 1500V DC overhead 39 Total electrified 12,592 Non-electrified 18,471 Total 31,063 1x 25 kv 52% 1x 25 kv; 1,60%
Practical evaluation of the energy flows: Network Rail (United Kingdom) G GWh/año 3,174.9 Public grid (Transmission and Distribution Grids) Energy entering substation Energy regenerated (Returned to the public grid) Infrastructure Auxiliary Other Loads (Stations, workshops) 3,074.8 GWh/año 52.8 GWh/año 80 GWh/año 449 GWh/año Regenerated 54.9 GWh/año Used by other trains 165 GWh/año Pantograph 2,711.5 GWh/año 221 GWh/año Regenerated energy Rheostatic energy 8 GWh/año Braking energy 229 GWh/año
Practical evaluation of the energy flows: Adif (Spain) Energy returned to grid, by input voltage (2011) 66 kv 0% 30-36kV 11-15 kv 20-27.5 kv 0% 0% 0% 44-55 kv 0% 132-145 kv 4% 220 kv 36% 380-400 kv 60% Consummed energy, by catenary voltage (2011) 2X25 kv 24% Energy returned to grid, by catenary voltage (2011) 3000 V 0% 1X25 kv 18% Single track non electrified Single track electrified Double track non electrified Double track electrified Total Conventional network 5,274.5 3,421.1 115.8 3,084.9 11,869.3 High-speed network 0.0 140.6 0.0 2,084.7 2,225.4 Total 5,247.5 3,561.7 115.8 5,169.7 14,094.7 1X25 kv 12% 3000 V 64% 2X25 kv 82%
Practical evaluation of the energy flows: Adif (Spain) G GWh/año 2,456.6 Public grid (Transmission and Distribution Grids) Energy entering substation Energy regenerated (Returned to the public grid) Infrastructure Auxiliary Other Loads (Stations, workshops) 2,363.2 GWh/año 62.6 GWh/año 235 GWh/año 300 GWh/año Regenerated 64.3 GWh/año Used by other trains 163 GWh/año Spain Electric Generation Mix (2011) 21,2 % Nuclear 18,7% Solar 18,6% Natural Gas 16% Coal Pantograph 1,968.8 GWh/año 228 GWh/año Regenerated energy Braking energy Rheostatic energy 264 GWh/año 36 GWh/año 15,3% Wind 10,2% Hydroelectric
Practical evaluation of the energy flows: Trafikverket (Sweden) CS Public grid (3-phase AC 50Hz) Railway Transmission Grid (1-phase, 16.6Hz, 110-132kV) CS Catenary Energy returned to the grid is negligible. Consummed energy, by input voltage of converter (2011) 130 kv 7% 50 kv 7% 22 kv 9% Connected to grids in the range 20kV-220kV with a step down transformer 6,3 kv 77%
Practical evaluation of the energy flows: Trafikverket (Sweden) G GWh/year 2,268.4 Public grid (Transmission and Distribution Grids) Energy entering substation Energy regenerated (Returned to the public grid) Infrastructure Auxiliary Other Loads (Stations, workshops) 2,159.2 GWh/year 0 GWh/year 113 GWh/year 35 GWh/year Regenerated 0 GWh/year Used by other trains 180 GWh/year Pantograph 1,968.8 GWh/year 180 GWh/year Regenerated energy Rheostatic energy 95 GWh/year Braking energy 276 GWh/year
1. Introduction 2. Traction systems and energy recovery 3. Practical evaluation of the energy recovery in three study cases 4. Conclusions
Conclusions Summary of the key quantities in the consumption maps: UK Spain Sweden Energy measured at PCC 100,0% 100,0% 100,0% Energy consumed at pantograph 88,0% 83,3% 91,2% Energy returned to catenary 7,2% 9,6% 8,3% Energy returned to grid 1,7% 2,6% 0,0% Energy cons. for ancillary systems 2,6% 9,9% 5,0% Energy to feed other loads 14,6% 12,7% 1,6% Energy regeneration can still be improved by further adoption of existing energy efficient technologies (regenerative trains, ESS, reversible substations, etc.)
Thanks for your attention Ignacio González Franco Igonzalez@ffe.es Eduardo Pilo de la Fuente epilo-merlin@ffe.es, eduardo.pilo@eprail.com