Monday, April 14, 2008

Carbon Neutral Rail

NOTE: We've moved! Visit us at the California High Speed Rail Blog.

The BayRail Alliance is hosting a talk this Thursday on Carbon Neutral Rail Service in Mountain View. David Dearborn is a San José native who has worked out a tentative plan to power Caltrain entirely by solar power. Presumably the technology and practice of the system can be applied to high speed rail as well - perhaps mixed with wind power, which the California High Speed Rail Authority has been promoting in its advertisements. Already there are plans to include some form of "hybrid" technology by which the HSR trains would restore power to the grid when braking, but to maximize the environmental and climate benefits of HSR it would be ideal to have the system entirely powered by renewables.

I won't be able to attend the meeting, but I recommend it and the BayRail Alliance to you all; hopefully someone can go and report back to us. Also, as you may have noticed, I'm not an expert on the engineering and tech aspects of HSR - but feel free to use this as an open thread to discuss such things.

UPDATE In the comments another Robert points out that the CHSRA is in fact studying ways to make the system carbon neutral:

The California High-Speed Rail Authority Board yesterday authorized a study to determine the feasibility of achieving zero greenhouse gas emissions for the power needs of the 700-mile electric high-speed train system. The study, timed to be completed by June of this year, will focus on costs, potential location of facilities and partnerships with utilities for on-site production of clean energy sources.

"The proposed route of the system intersects with many of the state's best location for wind, solar and geothermal facilities," said Quentin Kopp, chairman of the Authority. "High-speed trains will help California meet the goals set out by the state to reduce greenhouse gas emissions; using new clean energy technologies to power the system will be an added bonus and establish California as a leader in reducing global warming while developing renewable energy sources."


Rubber Toe said...

I remember reading back in February that CHSRA was going the study the feasibility of powering the system with 100% renewable energy. Here is the link that I saw back then:

I believe that the increased cost of doing this would be well worth the extra expense in the short run. Because in the long run the renewable energy will be cheaper than power from the coal plants. Having a 20 year agreement for a fixed/known cost of electricity will put the project on much firmer financial footing. Any outside private company looking to invest will be more inclined to do so if there are fewer *unknown* costs moving forward.

I think that it would make the vote in November a complete slam dunk if they decided to go 100% renewable too. JMHO...


Rubber Toe said...

Try this...

Anonymous said...

For reference, a 14-car Alsthom AVE trainset supports up to 700 passengers and has an empty mass of 395 metric tons. Fully loaded the stored kinetic energy at 220mph (~100 m/s) is ~650kWh.

The simplest solution is to use the recuperated brake power from one train to help accelerate another train on the same network segment. Note that the collection of electric machines on that trainset are rated at 12000kW in motor but only 8000kW in generator mode.

Another option is to briefly reduce the flow of water through a turbine at a hydro plant that supplies the grid. In that case, the recuperated energy is used to briefly maintain the already high speed of other trains.

A third option is to add a sink/source in the form of a high-power ride-through facility based on banks of ultracapacitors (solid state), superflywheels (cheaper) or Li-ion batteries (high capacity, overdimension 2-3x for longevity).

The old munitions bunkers in the Concord Naval Weapons Center would be a good place to house such a facility because (a) they can contain uncontrolled releases of energy during an earthquake, (b) bunkers are hard to wreck and (c) the soil there is contaminated with arsenic.

All of the above are preferable to the alternative, which is to dissipate the kinetic energy as heat in the brakes - still needed for emergencies, of course - or else in snubber circuits embedded in the grid.

However, regardless of how the brake energy is recuperated, that AVE trainset probably needs around 10000kW to sustain a speed of 220mph on a level track without ambient wind. That means another 650kWh is consumed roughly every four minutes just to overcome rolling and wind resistance.

Put another way: recuperative braking actually does much less for the total energy budget of HSR than it would for a subway system like BART. Its trains have to stop much more frequently, accelerate more rapidly and, there are more trainsets in motion at any given time - albeit at more moderate speeds.

Nevertheless, HSR would still benefit from using recuperative braking. For one thing, running the electric motors as generators reduces thermal fatigue on the eddy-current brakes in the bogies.

For another, so-called ride-through buffers smooth out the load on the grid, which is operating very close to rated capacity on hot summer days in California. Stabilizing the grid is especially valuable if the electricity is produced using a highly dynamic mix of renewable energies.

For reference, here are a few videos on recent research into such virtual power plants in Germany plus info on renewable energy facilities in California.

Fully renewable: biogas + wind + solar

From waste to watts: biofuel bonanza

Fatal attraction: birds and wind turbines

Solar power makes a comeback

Robert Cruickshank said...

robert, thanks so much for the link to that article. It would indeed be well worth the initial cost, especially since so much of California's electricity is generated via fossil fuels - meaning HSR would have lower overall costs with a renewable power source, alongside the environmental and climate benefits of carbon neutrality.

anonymous, that is some excellent information you've given. I don't confess to understand all the engineering and tech, but I'm glad we have someone here who does. It sounds as if recuperative braking isn't going to be as important to the HSR system as sustainable, renewable power sources.

Rubber Toe said...

Thanks for the clarification on why recuperative (i.e. regenerative) braking isn't as important on HSR as it would be on a normal subway or BART like system. In layman's terms it sounds like the energy required to simply run the trains at speed is so much more than what is generated by the infrequent braking that the primary energy/cost driver is the high operational speed.

Something else that occurred to me during lunch related to overall operational costs. I remember reading somewhere that the HSR was 3x more energy efficient than a plane, and 5x more than a car. It is important to note that it is not possible to run a commercial jet on anything other than liquid fuel (i.e. not electricity).

Something like 30% of the operating cost of airplanes is directly attributable to the cost of oil. As the cost of oil goes up, the cost of flying goes up too. If you power the HSR with renewable energy, the cost of oil is a complete "don't care". Actually the reverse is nearly true, the higher oil costs, the more competitive HSR travel becomes relative to flying or even more so compared to driving.

Think about it this way. In the last several weeks 4 different airlines have declared bankruptcy! The higher cost of oil has had a lot to do with that coming about. Basically, you have an industry flying people around on very old planes (i.e. typically <15 years old), that is chronically bleeding money despite billions of dollars of federal subsidies, that is absolutely hostage to the price of a commodity that has quadrupled in price in the last 5 years, and shows no inclination to slow down anytime in the foreseeable future.

If you just think about it in that context, you would never build another plane if you were inclined to make money or be energy wise.


Anonymous said...

@ Robert Cruickshank -

correct, and actually the scale of what's needed isn't even all that large, relatively speaking.

The CHSRA is estimating some 86 trains will be traveling in each direction on any given day. For a quick estimate, let's assume each of those is a full 14-car trainset of 700 seats each, i.e. 120000 available seats per day, ~44 million a year.

Further, let's assume that betweeen noise ordenances and customer demand mean trains will only travel between 6:00am and 11:00pm, with average time in transit roughly 3 hours (SF-LA express trains are faster, of course).

If we assume roughly equal spacing between train departures from the ends of the line, we end up with roughly one train every 10 minutes in each direction. Ergo, during the day, there will be 35-40 trainsets in transit at any given time.

Not all of these will be traveling at 220mph, since only a subset of the route supports these very high speeds. At 110mph, only 1/8 of the power is required. Therefore, as a quick-and-dirty estimate, figure 20 trains @ 10000kW plus 20 @ 1250kW = 225MW of electrical power. So, figure peak load for the whole HSR system will not exceed 300MW - and that's only when the system is fully operational.

For reference, total generating capacity in the state is currently around 50GW, i.e. over 165 times that number. By 2020, that factor will have gone well above 200 even with conservation measures. Geothermal delivers ~3GW today, with potential for 2-8x that number. PG&E's Ivanpah thermal solar power plant in the Mojave is scaled at 400MW (land use ~2500 acres = ~4 sq. miles).

Wholesale rates for renewable electricity are competitive with natural gas co-generation at peak time, but still well above base load. If CHSRA decided to run exclusively on renewable electricity, that might add $5-10 to the cost of an SF-LA ticket, compared to running on the cheapest possible mix of fossil fuels and nuclear.

Quick reality check: if you go to the Southwest airlines web site and book a business flight from SFO to LAX and back on the same day a week before departure, you can expect to shell out about $250 in air fare incl. taxes, fees etc. A full-fare same-day return HSR ticket might cost about the same.

Ergo, the incremental cost of running HSR exclusively on renewable electricity isn't going to break the business model. Indeed, offering true zero emissions travel may well increase ridership by enough to reduce the premium to zero, especially if you get fringe benefits like wireless Internet access plus free electricity for your laptop and/or the battery pack of the electric folding bicycle you're taking along (how's that for 100% renewable?)

Electrochromic windows in business would be a nice touch to keep the sun's glare off your flat panel so you can get some work done on the way.

無名 - wu ming said...

very cool stuff. given the potential for thermal solar in the hot-as-hell central valley, and wind in the delta and on the coast, this should totally be doable (and is a nice illustration of how a strategic initiative such as this has a virtuous cycle of stimulating multiple interconnected solutions at once).