35 to 70 GW of solar, plus wind, could power all freight trucks in the U.S. or Europe

By Will Driscoll

Many truck manufacturers are developing electric freight trucks, whose projected lower costs for fuel and maintenance would, by one estimate, quickly outweigh their higher purchase price. With this cost advantage, electric trucks could ultimately dominate freight trucking. A charging infrastructure for an all-electric continent-wide fleet of freight trucks in the United States or in Europe could be powered by 35 to 70 gigawatts of solar farms, plus an equivalent amount of wind farms.

Tesla and Peterbilt are the first firms to develop electric heavy-freight trucks—the global term for tractor-trailers or Class 8 trucks. BYD already offers medium-sized electric trucks and a larger electric freight truck with a short range, while medium-sized electric trucks have been announced by Daimler, Cummins, Volvo, DAF, and a Navistar/Volkswagen joint venture.

The North American Council on Freight Efficiency predicts that electric trucks will have an “increasing role” in freight transportation. Also relevant—because freight trucks, like city buses, operate many hours per day—is a projection by Bloomberg New Energy Finance that electric city buses will capture 84 percent of global bus sales by 2030, due to low operating costs and declining battery costs.

In the policy arena, a report from the International Council on Clean Transportation, which supports national governments in reducing transport sector pollution, notes that “electric-drive heavy-duty vehicle technologies are essential to fully decarbonize the transport sector.”

These market and policy drivers point to a new market opening for solar power: solar farms, possibly near truck stops, to power electric freight trucks. A spreadsheet calculation shows that 35 to 70 gigawatts of solar power, plus an equivalent amount of wind power, would produce an amount of electricity each year equal to the needs of an all-electric fleet of heavy-freight trucks in the U.S. or in Europe. That’s because by coincidence, the fleets of heavy-freight trucks in the U.S. and Europe travel approximately the same distance each year. (A technical note below provides details of the calculation.)

Pursuing this market opening could help the solar industry maintain its approximate 30 percent global growth rate in recent years, even as the industry keeps expanding. Maintaining a 29% growth rate, deemed “challenging but feasible” in a research studypublished in Science magazine, would result in a global installed base of 10 terawatts of solar power by 2030.

As electric freight trucks become more widely available, solar industry participants could help ensure that charging stations for the trucks are solar-ready, and ultimately solar-powered. This could involve research and decisions regarding optimal placement of charging stations; ensuring that a sufficient number of charging stations is always available to meet growing demand; possibly optimizing charging during times of peak solar and wind production; and providing electricity storage as needed.

Powering electric heavy-freight trucks with solar and wind power would also cut CO2emissions by displacing diesel fuel. Globally, road transport accounts for 22% of energy consumption, of which 30% is long-haul road freight. Therefore, CO2reductions of about 7% (i.e., 30% of 22%) could be achieved by powering heavy-freight trucks with renewable energy, in each region that follows this path.

If most trucking firms ultimately conclude that electric heavy-freight trucks save money, they could aim to replace their diesel trucks with electric trucks as their diesel units reach the end of their useful life. The Bloomberg projection noted above projects that will happen for electric city bus sales by 2030. With global production of heavy-freight trucks estimated by Deloitte at 1.7 million in 2014, the pace of diesel truck replacements could be limited by global manufacturing capacity for electric heavy-freight trucks.

Technical note: The calculation starts with the annual distance traveled by the current U.S. and European fleets of heavy-freight trucks in 2015, as reported by the International Energy Agency; each is approximately 200 billion kilometers. For the energy needed to power a heavy-freight truck, the lower bound analysis uses an estimate of one kilowatt-hour per mile, developed by University of California/Berkeley materials science professor Gerbrand Ceder. The upper bound analysis uses a specification that Tesla reported subsequently for its heavy-freight truck of “less than 2 kWh per mile” (the upper bound uses 2 kWh per mile). Converting kilometers to miles, and kilowatt-hours to gigawatt-hours, and then multiplying shows that 124,000 to 248,000 gigawatt-hours per year would power such a fleet in either the U.S. or Europe. At a U.S. national average capacity factor for a solar farm pegged at 20 percent by the National Renewable Energy Laboratory, 70 to 140 gigawatts of solar would produce this amount of electricity each year (given 8760 hours per year). If solar and wind each provided half the energy needed, solar’s contribution would be 35 to 70 gigawatts.

Sensitivity analysis: Regarding solar’s capacity factor in the U.S., Lawrence Berkeley National Laboratory has reported the median capacity factor for utility-scale solar to be 26 percent. If this were to be the average capacity factor for future utility-scale solar installations, rather than the 20 percent value used above, the solar capacity needed would be reduced accordingly.

Hot Roofs Above Bedrooms Cause Sleep Deprivation—Can You Solve the Cool Roof Puzzle?

By Will Driscoll

People who sleep in a top-floor bedroom under a black asphalt roof are likely to lose sleep on summer nights due to heat from the roof, with serious consequences.  Technically, the fix is simple—coat every black asphalt roof with a white coating—but progress toward that goal is slow.  Can you advise on how to make it happen, in the comments section below?

The issue: black asphalt roofs get really hot, keeping people from sleeping well, and causing real problems

Black asphalt roofs, which are common on Northeast urban row houses (townhouses), “can reach temperatures of 150°F or more in the summer sun,” reports the U.S. Department of Energy.  With or without air conditioning, a roof that hot above your bedroom will radiate heat at you all night long.

And people can’t sleep well when it’s too hot.  A research study using data reported by 765,000 people over 10 years found that “increases in nighttime temperatures amplify self-reported nights of insufficient sleep.”

Losing sleep is far worse than a nuisance.  “People make cognitive errors that matter when they sleep badly, whether crashing vehicles or making poor decisions in the workplace,” said UC Berkeley professor Solomon Hsiang in response to the study, as reported by Bloomberg.  He added, “Students learn poorly when they don’t sleep, and consistent lack of sleep harms people’s health.”

The technically easy solution:  white roof coating of asphalt roofs

Any roofing firm can apply an “elastomeric” white roof coating to a black asphalt roof, which can reduce a roof’s temperature on a 90-degree day from 150°F to 95°F.  (“Elastomeric” means the coating will stretch with the roof as it expands when it’s warm, and contract with the roof as it contracts when it’s cold.)  A homeowner who can safely get up on their own roof, with tools and supplies, can also do the job.  The cost is modest, since the job is relatively small: clean, patch, prime, and apply the finish coat.

But progress in getting black asphalt roofs coated white is slow.  For example in Philadelphia, where people have been talking for a decade about this issue, look closely at the Google Maps satellite view of the city and you will see mostly black roofs, while the roofs that aren’t black are generally gray—a color that provides only about half the cooling benefit of a white roof.

The puzzle:  How to persuade landlords and homeowners to apply white roof coating to black asphalt roofs?

This section offers some possible solutions to the white roof puzzle.  Please share your ideas in the comment section below.

Community group involvement:  People who have black asphalt roofs may not know that their roof gets as hot as 150°F in the summer, or that a simple white roof coating would fix the problem.  Community leaders could work with roofing companies to advertise the benefits of white roof coating—soliciting testimonials from those who already have a white roof—and its modest cost.  By aggregating the orders of a number of homeowners at a time, a community group could request bids from roofing companies and obtain a lower price for the work.  The challenge here is that community leaders are already busy pursuing other initiatives.

Residential “PACE” financing:  As states and cities gain experience with commercial PACE financing (i.e., “property-assessed clean energy” financing to fund energy-saving measures on commercial buildings), more states and cities are now adding residential PACE financing, to allow homeowners to borrow money for approved energy-saving expenses.  In a PACE program, a building owner’s loan repayments are billed via their property tax bill.  PACE financing could help homeowners who don’t have adequate savings to pay for white roof coating.  By making financing easier, it could also expand the market for white roof coating, and with a larger market, roofing companies might be more inclined to advertise the service.  The challenges are that some states have not yet enabled residential PACE financing, and in states that have done so, launching a city PACE program takes time and energy.

Leapfrogging to rooftop solar:  As the cost of rooftop solar installations decline, this solution becomes economical in more locations every year.  A rooftop solar system that effectively shade the roof, and does not radiate much heat to the roof, would effectively keep the roof cool.  In some locations the electricity cost savings provided by a solar panel system could pay for the system and its financing costs.  The challenge is the same as the basic challenge for white roof coating: how to persuade homeowners and landlords to take this step.

A new public health law:  Landlords who don’t pay their tenants’ air conditioning bills are under no pressure to apply a white roof coating to their properties and thus improve their tenants’ health.  Cities could institute a public health measure requiring white roof coating.  Then, if a landlord failed to comply, the city could coat the roof white and bill the landlord via the property tax bill.  (In my suburban town, letting your grass grow tall is considered a public health problem, and if you don’t cut your grass the city may cut it for you, and bill you for the work.)  The challenge is that to my knowledge no city has yet recognized hot roofs over bedrooms as a public health issue.

Other ideas:  What is missing here?  What are your ideas?  Please share them in the comments section below.

A Fast Solar Ramp in Hawaii Can Save $3-7 Billion

By Will Driscoll

Hawaii can save $3 to $7 billion by accelerating its transition to solar, according to an independent utility modeling analysis.  That conclusion is validated by the experience of the Hawaiian island of Kauai, where a new solar-plus-storage park will bring down the island’s electricity rates. 

A new state law in Hawaii advances its commitment to pursuing renewables aggressively, so now it’s up to Hawaiian Electric to verify the massive $3-7 billion savings potential from an aggressive solar transition, and then pursue that path.

Savings of $3 to $7 billion

Hawaii’s legislature has set a goal of 100 percent renewables by 2045, and Hawaiian Electric Industries is pursuing a state-approved plan to meet that goal.

Yet a new study of Hawaii’s grid by the Rhodium Group found that moving faster on solar (with minimal growth in other renewables) would save Hawaii $3 to $7 billion between 2020 and 2045.

Whereas Hawaii on its current path would reach 40 percent renewables by 2030, the study found that the least-cost path would achieve 46 percent renewables just three years from now, by 2021, and then 58 to 84 percent renewables by 2030.

The range in savings, between $3 and $7 billion, reflects two bounding analyses: 1) moderate renewables costs combined with low oil prices (for $3 billion in savings); and 2) low renewables costs combined with high oil prices (for $7 billion in savings).  (Hawaii generates most of its electricity using imported oil.)

Beyond solar, the study found that Hawaii would need “up to two gigawatts of lithium-ion battery or functionally equivalent storage in 2030” to achieve the least-cost energy system. Kauai has shown the way here, as it is relying on battery storage provided by Tesla and the AES Corporation to store solar power for later release onto the grid.  (The study’s methodology is described in a technical note below.)

Kauai’s new solar-plus-storage park will bring down electricity rates

Kauai, where a member-owned co-op utility provides the power, shows how easy it is to adopt renewables quickly. Kauai has advanced from 8 percent renewables in 2011 to 44 percent now.

That’s well above the 27 percent for the rest of Hawaii, which is served by Hawaiian Electric.

Kauai aims to generate 50 percent of its electricity from renewables by 2023, and 70 percent by 2030. That 70 percent figure is the approximate midpoint of the 58 to 84 percent range found in the Rhodium study to be the least-cost range for Hawaii as a whole by 2030.

The cost of electricity from a new AES-built solar-plus-storage system on Kauai will be 11 cents per kilowatt-hour—significantly lower than the 14.5 cents per kWh for Tesla’s system just two years ago—and “will provide downward pressure on rates,” said the Kauai utility’s CEO David Bissell.

The Government of Hawaii wants affordable electricity and rapid integration of renewables

Hawaii’s governor recently signed a law providing that by 2020 the public utilities commission must set performance incentives and penalties to tie an electric utility’s revenues to its achievement on performance metrics—breaking the direct link between investment levels and allowed revenues. Two of the key performance measures align with the solar progress in Kauai and the results of the Rhodium Group study—namely, affordability of customer electric bills, and rapid integration of renewable energy.

Hawaii’s elected officials have been concerned about Hawaiian Electric at least since 2015, when 40 elected officials called for a study of publicly owned electric utilities, as on Kauai, for all of Hawaii.

The Rhodium Group study itself indicated interest across Hawaii in accelerating solar, as it gained the participation of Hawaiian stakeholders in 200 hours of focus groups and interviews, and was funded by a Hawaiian technology firm incubator, Elemental Excelerator.

It’s now up to Hawaiian Electric to verify the projected $3-7 billion savings, and pursue a fast solar ramp

The best course for Hawaiian Electric would be to run the Rhodium Group’s numbers through its own utility model to develop its own estimate of the cost savings possible from a fast renewables ramp. If Hawaiian Electric does not yet have a sophisticated utility planning model for this purpose, which includes, for example, battery storage as an option, the utility would be wise to first upgrade its planning model, and then re-run the Rhodium Group’s analysis. Or, if Hawaiian Electric’s most recent planning analysis, as reflected in its December 2017 Power Supply Improvement Plan, was limited by any artificial constraint on the amount of solar that it would allow, the utility would do well to re-run its analysis without any such constraint.

Assuming that Hawaiian Electric confirms the Rhodium study’s results—which Kauai’s experience already validates—then it should roll out an aggressive solar ramp. To its credit, Hawaiian Electric has been working with the National Renewable Energy Laboratory to understand how it can best modernize its island grids to incorporate low-cost solar. Hawaiian Electric could now quicken its pace to accelerate its renewables transition. Its customers would be happier paying less for electricity, and Hawaiian Electric could receive performance incentives, rather than pay penalties for failing to meet performance metrics, under Hawaii’s new state law.

Technical Note: 
The Rhodium Group study simulated Hawaii’s grid using a modified version of SWITCH, an “open source optimization modeling platform,” which contained detailed representations of the electric grid on Hawaii’s four most populous islands. For oil price scenarios, the study used the upper and lower bounds of electric power sector diesel and residual fuel oil prices in Hawaii between 2006 and 2017. For renewable price scenarios, the study started with renewable energy costs assumed by Hawaiian Electric in its December 2017 Power Supply Improvement Plan. Then, to account for future cost reductions for renewables due to technological improvements and economies of scale, the study “scaled those prices to projections from NREL’s mid-cost and low-cost scenarios.” The study’s authors then ran the modified version of the SWITCH model to find the least-cost energy system for 1) moderate renewables costs combined with low oil prices, and 2) low renewables costs combined with high oil prices.