1. Chicago Transit Authority Energy Initiatives
Energy Storage Association
April 19, 2017

2. Big Challenges with Energy Storage at CTA
Location, location, location.
ROI
CTA’s electricity is cheap – 7 cents/KWh
Equipment and infrastructure is expensive and complex (but getting cheaper and easier)
Energy savings and revenue opportunities not a sure thing

3. The Case for Wayside Energy Storage System (WESS)
When there are no accelerating trains, regenerative braking energy dissipates as heat.
WESS can capture excess braking energy and discharge it to the third rail, provide voltage support, or participate in grid ancillary markets.
To estimate ROI, two issues need to be addressed first:
The opportunity from “breaking events”
Physical space
WESS

4. CTA WESS Feasibility Study (Consultant: Mott McDonald)
1. Load flow analysis – a model of power flows along the entire Red Line and connecting sections
How much electricity is being captured from regenerative braking trains today?
How much more electricity could be captured if we installed WESS?
Where are the best locations to install WESS to capture and reuse the most electricity?
2. Site surveys – physical assessment of high-potential WESS locations
Are high-potential locations accessible and physically fit for the installation of a WESS?
Load flow analysis data inputs:
Rail car data – motor characteristics, mass, length, power, regenerative braking characteristics
Signal data – line layouts, stations, junctions, gradients, speed limits
Traction power data – substation connections, substation equipment ratings
Planning data – train schedules, passenger loads, dwell times at stations

5. CTA Rail Stats Getting people around Infrastructure 1,400 rail cars
239 million passengers in 2016
78 million miles run in 2016
Infrastructure
Runs on continuous electrified (“third rail”) network
8 lines
145 stations
66 substations
1,400 rail cars
700 cars with regenerative braking deployed on Red, Green, Purple, Yellow, and Pink Lines in (“5000” series)
700 without regenerative braking (“2600” & “3200” series) to be replaced beginning in 2020
About 430GWh in consumption, annually, costing $30M
WESS modeled on Red Line (red arrows)
5000 trains also deployed on Green, Pink, Yellow, and Purple Lines (blue arrows).

6. Regenerative Braking Performance
5000 series trains weigh more than older cars and have additional electric features. A single 5000 car uses more electricity than an older car, but…
In live simulation in 2010, a group of 5000 series cars running on the same segment of track used 20% less electricity than older cars.
Since the full 5000 series deployment, electricity consumption is 10% lower than predicted—and that’s with only half the fleet with regenerative braking.*
Wow!
*Validated by regression model forecasting energy consumption and load flow study.

7. Load flow analysis data inputs:
Rail car
Signal
Traction power
Planning
Motor characteristics
Mass
Length
Power
Regenerative braking characteristics
Line layouts,
Stations
Junctions
Gradients
Speed limits
Substation connections
Substation equipment ratings
Train schedules
Passenger loads
Dwell times at stations

8. Modeling Results 6 candidate substations identified.
Model simulated electricity savings with various configurations of one, two or three WESS units in substations.
One WESS achieved 436MWh in annual savings; adding a second only produced 7% more and adding a third resulted in no additional benefit.
A single WESS saved KWh per hour but…
There was only 20-80KWh savings for the system as a whole.
CTA’s network and third rail composite mean regen energy can flow two miles or more.
WESS ends up intercepting energy that would go to other trains, making other substations work harder.

9. Payback Estimate for Single WESS Unit
Specs
2000 Amperes
Rated between 6 and 8 KWh storage capacity
ROI
Cost of $ K up front
$30K in energy savings per year
20-year payback period
Does not include revenue from ancillary markets like Frequency Regulation, but capacity for participation likely to be low, intermittent.

10. Other CTA Energy Initiatives: E-buses
Progress
2 in service, in planning stage
Existing 2 are charged in garage—slow charge
New cohort would charge in route—quick charge
Expect savings on energy, maintenance
Challenges
Buying E-buses is easy; installing charging stations is hard.
Limited number of locations have space and optimal electric utility interconnection
Concerns about service delays due to charging time when there is bad weather, constructions, or accidents. There is little margin for error with a tight route schedule.

11. Other Energy Initiatives: Solar
Cook County sponsoring “community solar business case studies” funded by Department of Energy grant
Array placed on government-owned land
Electricity generated sold to surrounding neighborhood.
CTA’s rail maintenance facility one of 15 sites selected out of 110 applicants.
Study will determine feasibility, potential ROI

12. Questions? Pete Ballard Chicago Transit Authority 773-960-4016 pballard@transitchicago.com