[IMAGE]elec.jpg[/IMAGE]Electrified rail systems appear to be making a comeback. With streetcar systems in Portland and Seattle; light rail systems in Phoenix and Sound Transit's newly opened Central Link light rail service, there's no doubt that electric traction-powered rail is experiencing a boom. In addition to purpose-built electrification projects, some diesel-powered systems are also looking to get onboard by converting.

Pros and Cons

When you compare electrification versus diesel, the benefits overwhelmingly favor electric. In this time of eco-consciousness, the fact that electrified rail generates lower greenhouse gas emissions than diesel is one of the most obvious benefits. In its upcoming switch to electric traction power, San Carlos, Calf.-based Caltrain expects to reduce air pollutant emissions by up to 90 percent.

Electrified rail systems achieve faster top speeds and accelerate much quicker, and don't require refueling, says Eric Scotson, Parsons Brinckerhoff's manager, West Region, Transit & Rail Systems. "You don't have to carry the weight of the diesel fuel around with you either, which can be in the thousands of pounds, so that makes a big difference," he adds.

Regenerative braking also makes electric traction technology much more efficient. "When you are accelerating, you use the motors to drive the train. When you want to brake, you use the motors as a generator to slow the train," he says. "The generated power can be pushed back into the system to be used by other trains, or what we are expecting in the future is we'll actually be able to push some of it back into the utility company and save both power consumed and power paid for."

Electric engines are easier and less expensive to maintain, while maintaining large diesel engines is difficult and requires highly skilled mechanics to maintain them. In addition, most diesel-powered locomotives are actually diesel-electric, so you have to maintain the diesel engine and the electric motors, Scotson adds.

The downside to electrified rail is the cost, which can be substantial due to the infrastructure involved, such as the overhead contact system or third rail, and building of power substations. But, while capital costs are high, the overall lifecycle cost is a lot more favorable to electrification, says Scotson.

Overhead contact systems, required by both high-speed and light rail systems, may also be viewed as a negative in the aesthetic sense. "To the general public, catenary wires might be seen as unnecessary clutter," he says.

Looking to make the switch

One such transit agency looking to make the switch from diesel to electric power is Toronto, Ontario-based Metrolinx's GO Transit rail service, which has run diesel commuter trains over existing track that was in place for CN (Canadian National Railway) and CP (Canadian Pacific Railway) freight services. GO Transit's rail service comprises seven lines, with a total of 242 miles of track. "More recently, we've begun to acquire some of the rail bed lines in the Toronto area, but historically, we are in effect a tenant, rather than some cities where you have purpose-built electric lines," says Metrolinx President/CEO Rob Prichard.

 The agency has been considering electrification on and off for more than 20 years, he explains. "We decided this spring that we needed to do a systematic and comprehensive study of the benefits and costs of the undertaking, and to think hard about sequencing and the priority we should assign the different corridors if we're not able to electrify all at once."

To that end, the Metrolinx Board of Directors recently established a Community Advisory Committee that will work with the agency to assess the benefits, impacts and costs associated with converting the existing railway, as well as define the scope of and recommend terms of reference for a study to be done by a consulting firm. The electrification study is scheduled to be completed by December 2010.

"We need to think hard about the cost, not just in dollar terms, but in terms of foregone investments in further expansion of infrastructure," Prichard says. "Because it may be that we get more cars off the road and have a bigger environmental and transit impact to building more infrastructure instead of converting our existing infrastructure to electric."

Enhancing service power

A rail service that is already in the process of going the electrified-power route is Caltrain. The commuter rail line, which runs one line on 77 miles (50 mainline and 27 commute-hours only) of track from San Francisco to Gilroy, is in the design phase of its project, with construction slated to begin in 2011 and revenue service set for 2015.

The project scope will include electrifying 52 miles of track from San Francisco to San Jose (the San Jose-to-Gilroy section is owned by Union Pacific and would continue to run diesel trains). Two traction-power substations and eight auto-transformer stations will be installed, with a capacity of 172 trains at peak five-minute headways. Cost of the electrification infrastructure is estimated at $608 million, while $397 million is tabbed for railcars.

An overhead contact system will be installed to provide power to trains up to 90 mph, with the capability to support the alignment for the San Francisco-to-San Jose section of the California High Speed Rail Authority's line, which will travel along the Caltrain rail right-of-way.[PAGEBREAK]

 

Get there faster

Caltrain saw electrification as a way to reduce its environmental impact, according to agency officials - as well as give a much-needed boost to its service. From 2004, when Caltrain introduced its Baby Bullet express, to 2008, ridership increased by nearly four million, or approximately 48 percent. "The increase in ridership presents other challenges, as some trains during peak periods are getting more crowded," says Caltrain's Communications Director, Christine Dunn. "The railroad cannot do much more to expand its capacity or the frequency of its service until it completes electrification of its system."

Because electric trains can accelerate and decelerate faster than diesel-powered trains, it is anticipated that travel time between San Francisco to San Jose will be reduced by 13 percent, she says.

Although it is still to be determined whether electric locomotives or electric multiple unit (EMU) trainsets will be purchased for the system, the agency is working with the FRA to obtain a waiver to operate EMUs. "We would be able to continue to operate diesel equipment 'under the wire,' Dunn says. "The diesel equipment would continue to be used to provide service to Gilroy and could also be used on the mainline to fill in as appropriate."

Filling in Power Gaps

One of the light rail systems built during the boom years of the 1980s was Sacramento Regional Transit District's (SRTD) 38-mile system, which links both the eastern and northeastern suburbs with Downtown and South Sacramento carrying 51,000 passengers on a typical weekday.

"We were one of the first New Start systems in North America in the early 80s, so we built a system with relatively simple rail vehicles, with substation spacing, in some cases, that were a mile-and-a-half and approaching two miles apart," says Sacramento SRTD's COO Mark Lonergan.

This excessive spacing resulted in fairly significant voltage drops in some locations during commute periods. To make matters worse, when the transit agency later added heavier, more sophisticated light railcars to its fleet, featuring A/C propulsion using an onboard inverter, more power-related challenges arose. "The consequence of that is now the car has a lower voltage limit of 525 volts and if the line voltage drops below 600, the performance of the car starts to ramp back until you get to 525 volts where the car won't run at all," Lonergan says.

In its quest to find a solution to its line voltage problems, the agency partnered with Mount Olive, N.C.-based IMPulse NC INC., to test a battery substation that would provide supplemental power to the train during voltage drops. Per the one-year demonstration project, the company supplied SRTD with the equipment free of charge so that it could conduct testing. PB is doing an independent analysis of the system's performance, says Scotson.

Battery voltage boost

The BASS (battery substation), manufactured by Canadian-based Envitech, and exclusively distributed by IMPulse, is an alternative energy power supply that will compliment any type of traction power system, says Jeffrey Wharton, IMPulse executive VP/GM.

 "Supplemental power is something that transit systems can use to alleviate weak points on the line where 'voltage sags' occur," Wharton says referencing the aging transit systems built 15 to 20 years ago that have undersized substations. "As train technology improves, they're adding air conditioning and more cars to the train system, so there's not enough power to support the system," Wharton says.

The project's main focus was to provide a voltage boost to SRTD's blue line, where they had begun running four-car trains. "The system is very underpowered, and the trains would be very sluggish going through certain sections of the line, so we took some data measurements," he says. One section of the line, which should have measured 800 to 850 volts, collapsed to 750 volts, and in some cases, it would get so low that it would trip the substation due to an under voltage condition.

"Now, when the train goes by, the battery substation will pump out as much energy as the train needs," Wharton says, adding that battery usage has maintained the 800-volt level. "We've interviewed some of the train operators and they've said that they've definitely noticed a difference in the performance of the train going through that particular section."

Another item IMPulse is testing is the ability to lower the utility peak demand rate, which would save energy at existing substations by providing energy through the batteries - known as "peak shaving." "What that does from an energy savings standpoint is the substations at either end of the location where the batteries are don't have to work as hard, or put out as many kilowatts of demand," he says.

The BASS system is comprised of a battery enclosure, which houses approximately 500 kW of power supply and a control power module, which consists of a DC circuit breaker to protect the line from over voltage or fault currents. This modular system, which can be moved by either a forklift or a crane, can be set on a rock pad, and doesn't require any concrete footing.

The battery substation retains its power two different ways. The first is through a trickle charge, where the batteries are connected directly to the contact system, whether it be a third rail or an overhead contact system, which is being fed by the traditional substation. The batteries can also be charged via train braking or regeneration. "Half of Sacramento's fleet is regenerative cars and the other half are older, which are not," Wharton says. "We are testing it for both systems."

IMPulse monitors the testing remotely through an Internet connection on a wireless modem. "We're able to get 24/7 real-time data, and we can remotely turn the battery station off and on through the Internet," says Wharton.

Another feature IMPulse hopes to test on the Sacramento line is the emergency backup system. "If you were to have a massive power outage in the area and the trains stop, the battery substation has the stored energy that will keep the train moving, so you can safely drive the train to the next station and offload your passengers," Wharton says.

 

0 Comments