SPECTRUM: Exposing the Power Vampires in Self-Driving Cars

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Drag from rooftop sensors makes Waymo’s self-driving minivan an energy hog. Photo: Wikimedia/Dllu

By driving smarter, autonomous cars have the potential to move people around and between cities with far greater efficiency. Estimates of their energy dividends, however, have largely ignored autonomous driving’s energy inputs, such as the electricity consumed by brawny on-board computers.

 

First-of-a-kind modeling published today by University of Michigan and Ford Motor researchers shows that autonomy’s energy pricetag is substantial — high enough to turn some autonomous cars into net energy losers.

“We knew there was going to be a tradeoff in terms of the energy and greenhouse gas emissions associated with the equipment and the benefits gained from operational efficiency. I was surprised that it was so significant,” says to Greg Keoleian, senior author on the paper published today in the journal Environmental Science & Technology and director of the University of Michigan Center for Sustainable Systems.

Keoleian’s team modeled both conventional and battery-electric versions of Ford’s Focus sedan carrying sensing and computing packages that enable them to operate without human oversight under select conditions. Three subsystems were studied: small and medium-sized equipment packages akin to those carried by Tesla’s Model S and Ford’s autonomous vehicle test platform, respectively, and the far larger package on Waymo’s Pacifica minivan test bed [photo above].

For the small and medium-sized equipment packages, going autonomous required 2.8 to 4.0 percent more onboard power. This went primarily to power the computers and sensors, and secondarily to the extra 17-22 kilograms of mass the equipment contributed.

Sources of added energy consumption for Ford Fusion

Sources of added energy consumption in Ford Fusion’s autonomy system. Credit: University of Michigan

However, autonomy’s energy bill ate up only part of the overall energy reduction expected from the autonomous vehicles’ ability to drive smarter driving — such as platooning of vehicles through intersections and on highways to cut congestion in cities and aerodynamic drag on the highway. As a result the modeled Ford sedans still delivered a 6-9 percent net energy reduction over their life cycle with autonomy added, and promised a comparable reduction in greenhouse gas emissions.

EV and gas models offered comparable results. Adding equipment was less burdensome for the EVs, which provided extra power for the processors and sensors more efficiently than a gas vehicle. But autonomy delivered a slightly larger net energy reduction in the gas vehicles, whose relatively inefficient drivetrains should benefit more from smart driving.

In contrast adding the large Waymo equipment package yielded a comparatively dark picture for the modeled EVs and gasoline-fueled sedans. The larger equipment increased net energy consumption on the Ford sedans by 5 percent, thanks mostly to the aerodynamic drag induced by its rooftop sensors.

Keoleian says this modeling result likely overstates real impacts from future autonomous vehicles, which he expects will manage to streamline even substantial sensors arrays. What concerns him more is the likelihood that all of the modeled packages understate power consumption by future autonomous driving subsystems.

For instance, Keoleian says future autonomous vehicles may employ street maps of far higher resolution than those used today to ensure the safety of pedestrians, cyclists and other drivers. In fact, real-time updating of high-definition maps by autonomous cars is one of the applications pushing the development of next-generation 5G wireless data networks.

Higher-bandwidth data transmission via today’s 4G network could boost power consumption by onboard computers by one third or more according to Keoleian and his coauthors. It is premature, they write in today’s study, to judge the power consumption associated with 5G.

Another concern for Keoleian are the indirect effects of introducing autonomous vehicles. By making driving more convenient, for example, smart cars could encourage longer commutes. “There could be a rebound effect. They could induce travel, adding to congestion and fuel use,” says Keoleian.

Such indirect effects of smart cars could either slash energy consumption from driving by 60 percent, or increase it by 200 percent, according to a 2016 study by the U.S. National Renewable Energy Laboratory. Guiding the technology’s development to avoid an energy demand explosion, says Keoleian, will require a lot more study.

This post was created for Cars That Think, IEEE Spectrum’s blog about the systems making cars smarter, more entertaining, and ultimately, autonomous.

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Bomb Cyclone Exposes Perry’s Subsidy Fallacy

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Pilgrim Nuclear Power Plant: Looks good on a sunny blue sky day, but didn’t weather the storm. Photo: NRC

Extreme weather events have knocked both nuclear and coal-fired power plants offline in just the past six months, undercutting the Trump Administration’s argument that subsidizing these aging energy generators is crucial for bolstering grid stability.  The latest failure came late last week when Winter Storm Gregory forced a nuclear plant in New England offline, ratcheting up the challenge facing grid operators amidst the “bomb” cyclone’s high winds and freezing temperatures. Continue reading

Circuit Reclosers Probed as Potential Cause of California Fires

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Automatic circuit recloser generating sparks at a simulated line fault. Photo: S&C Electric

Wind-swept fires that killed more than 40 people in California in recent months have also jolted the state’s biggest utilities, Pacific Gas & Electric (PG&E) and Southern California Edison (SCE). The utilities have had to work around the clock to keep power flowing to fire-afflicted communities, even as their equipment and policies face scrutiny as potential contributors to the deadly fires. California regulatorspoliticians and trial lawyers are querying SCE and PG&E’s tree trimming and line maintenance — common culprits in prior California fires — but they are also examining a utility device that produces sparks by design: automatic circuit reclosers.

Automatic reclosers are pole-mounted circuit breakers that can quickly restore power after outages, but they can also multiply the fire risk from damaged lines. While SCE is adjusting recloser operations to reduce fire risks, PG&E’s practices are less clear. And only their neighbor to the south — San Diego Gas & Electric (SDG&E) — is tapping advanced recloser technology that is safer by design.

Reclosers make quick work of many line faults, the great majority of which result from temporary insults such as a branch striking a line or the electrocution of an unlucky squirrel. As Australian recloser manufacturer NOJA Power puts it: “Like the success of Vanilla Ice, Dexy’s Midnight Runners and Devo, most network faults are transient.” In such cases the recloser detects a power surge, momentarily interrupts electricity flow, and then automatically re-closes its contacts to restart flow down the affected line.

Reclosers usually try restarting a line 2-3 times before giving up and “locking out” a line. Sometimes multiple attempts are needed to do the job, writes NOJA Power, such as when high-temperature electrical arcing at the site of the fault burns away hung trees or tree limbs.

Under the wrong conditions, however, such arcing and ignition can obviously spark a fire. Reclosers contributed to several of Australia’s deadly Black Saturday bushfires of February 7, 2009, according to the official report of the Victorian Bushfires Royal Commission. Continue reading

Mexico Border Wall Won’t Stop Cross-border Power Push

Relations between the United States and Mexico are strained at the national level, with President Donald Trump pushing his promised border control wall and demanding a U.S.-favored rewrite of the North American Free Trade Agreement (NAFTA). But Mexico and the southwestern states have continued working towards an international agenda for electricity, and regional players are talking up a first set of projects due to be completed before Trump’s term is up — projects that put the region on a path to a far more electrically-porous border.

These projects include a trio of new crossborder links between California, Arizona and Mexico to be completed in the next three years. They also include grid studies, revised market rules, and new power lines within Mexico that could rapidly expand flows over all of the U.S.-Mexico interties. “The proposition right now is fairly small because the interconnections are small. But that’s going to change,” says Carl Zichella, director for Western transmission at the Natural Resources Defense Council. Continue reading

Solar Microgrids May Not Fix the Caribbean’s Devastated Power Systems

After the destruction inflicted across the Caribbean by hurricanes Harvey, Irma, and Maria, renewable energy advocates are calling for a rethink of the region’s devastated power systems. Rather than simply rebuilding grids that delivered mostly diesel generation via damage-prone overhead power lines, renewables advocates argue that the island grids should leapfrog into the future by interconnecting hundreds or thousands of self-sufficient solar microgrids.

“Puerto Rico will lead the way for the new generation of clean energy infrastructure. The world will follow,” asserted John Berger, CEO for Houston-based solar developer Sunnova Energy in a tweet before meeting in San Juan with Puerto Rico Governor Ricardo Rosselló this week. Rosselló appears to be on board, inviting Elon Musk via tweet to use Puerto Rico as a “flagship project” to “show the world the power and scalability” of Tesla’s technologies, which include photovoltaic (PV) rooftops and Powerwall battery systems.

Some power system experts, however, say the solar-plus-batteries vision may be oversold. They say that the pressing need to restore power, plus equipment costs and other practical considerations, call for sustained reliance on centralized grids and fossil fuels in the Caribbean. “They need to recover from the storm. Unfortunately I think the quickest way to do that is to go back to how things were before,” says Brad Rockwell, power supply manager for the Kauaʻi Island Utility Cooperative that operates one of the most renewable-heavy grids in the U.S. Continue reading

NATURE Scientists Get Political on Climate

By Peter Fairley for Nature / October 11 2017

It’s moving day at the Legislative Assembly of British Columbia on a sunny summer morning in Victoria, Canada, and climate scientist-turned politician Andrew Weaver is battling to retain an expansive leather sofa for his new basement office. Just a few weeks earlier, in May 2017, thousands of people in and around Victoria cast their votes for the British Columbia Green Party, which Weaver leads, growing the caucus from his one lonely seat to three. The wider of the office’s sofas, he explains, will be crucial during long nights of debate and voting. “This is the one you can sleep on. And we need that.”

Three seats in an 87-seat legislature might sound modest, but it’s enough to make Weaver — a professor at the University of Victoria — into a political kingmaker. The incumbent Liberal Party and the opposition New Democratic Party (NDP) each garnered fewer than half of the seats, giving Weaver’s Green Party the balance of power. Weaver exercised his new-found influence in the weeks after the election to remove Christy Clark, the Liberal premier of British Columbia, who had championed fossil fuels and neglected climate policy. He negotiated climate-friendly terms with the NDP to install John Horgan as the party’s first premier in 16 years.

Weaver is an internationally recognized pioneer of models that represent Earth’s physical systems at a modest resolution, facilitating the simulation of climate over tens of thousands of years. His ascent from academic to political power broker is a far cry from the attacks on climate scientists that are under way in the United States. But there are US researchers who dare to dream that they too can tilt the political balance. In fact, dozens have declared the intent to run for local, state or national office, promising to reverse the dismissal of climate change and other anti-science positions espoused by US President Donald Trump’s administration and other Republican Party leaders.

… READ ON AT NATURE.COM

Floating Wind Turbines on the High Seas

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Norwegian oil and gas giant Statoil positions 6-megawatt turbines off the coast of Scotland for the world’s first floating wind farm. Photo: Roar Lindefjeld/Woldcam/Statoil

The world’s first wind farm employing floating turbines is taking shape 25 kilometers off the Scottish coast and expected to begin operating by the end of this year. New research by atmospheric scientists at the Carnegie Institution for Science in Stanford, Calif. suggests that the ultimate destination for such floating wind farms could be hundreds of kilometers out in the open ocean. The simulations, published today in the Proceedings of the National Academy of Sciences, show that winds over the open ocean have far greater staying power than those over land.

Wind power generation is obviously contingent on how fast and how often winds blow. But only over the past decade have scientists and wind farm developers recognized that the winds measured prior to erecting turbines may not endure. For one thing, dense arrays of wind turbines act as a drag on the wind, depleting local or even regional wind resources. Continue reading