In October, California Governor Jerry Brown signed into law an ambitious bill that will require the state to generate half of its electricity from renewable sources by 2030 and double energy efficiency.

The law does not lay out specific plans for how to accomplish this, but experts in the field say utility-scale solar will likely make up a large portion—assuming issues with siting and transmission can be solved, and innovations in energy storage can be applied.

“Looking at present trends, we'll see a lot more solar photovoltaics at utility-scale size,” says Ethan Elkind, associate director of climate change at the University of California, Berkeley's Center for Law, Energy and the Environment. “Barring other policy developments and technology changes,” says Elkind, “that will be the main contributor.”

Elkind spoke on a panel hosted by the San Francisco Planning and Urban Research Association last month, along with representatives from the utility Pacific Gas and Electric, the American Planning Association, and San Francisco's Public Utility Commission. The panelists discussed strategies for how California would reach its 50-percent-renewables goal.

The state is already well on its way. In 2014, California generated over 44,000 gigawatt hours of renewable electricity, or about 20 percent of its total usage. California defines renewables as biomass, geothermal, small hydro (under 30 megawatts), solar, and wind. It’-s on track to surpass 33 percent renewables by 2020.

Reaching the state’s 2030 goal may sound exceedingly ambitious, but generating enough renewables to make them the main part of its energy mix may not be too big a problem. In California, the “cost for developing solar is now comparable to the cost for developing natural gas fired plants,” says Josh Hohn, who founded APA’s energy initiative.

However, one major issue will be how that energy is stored and whether utilities can nimbly switch from storing to delivering electricity. Batteries will play a big role, as will demand-response strategies.

One idea especially favored by PG&E is solar-powered electric vehicle charging stations. That would help use surplus solar energy during the daytime, while reducing evening electricity demand. In addition, the more cars that plug into the electric grid, the more revenues for PG&E. The utility recently presented a proposal to build over 25,000 charging stations for $654 million. The California Public Utilities Commission, rejected the plan, although the agency approved a smaller-scale pilot project for 2,510 stations.

That setback for PG&E notwithstanding, California is interested in pushing electric vehicles because transportation is currently the largest source of greenhouse gas emissions, at around 38 percent of the state’s total.

Some companies are also looking to repurposed batteries from electric vehicles to store solar or wind energy. For instance, says Hohn, as the battery in an electric car loses range, customers may want to upgrade to a newer one with more range. However, that older battery still stores energy. Those batteries can be repurposed and stacked to store energy from solar and wind. Nissan and General Motors have already announced their intentions to repurpose batteries from the Leaf and Volt vehicles, respectively. And Tesla is also developing stationary battery packs aimed at homes, businesses and utilities.

Repurposing old electric vehicle batteries, says Elkind, “is very promising... [and] will be a critical piece to balancing renewables."

Hohn says another storage option is using surplus solar or wind energy to compress air. Then, when the sun isn't shining or the wind isn't blowing, the air can be released to turn a turbine. A southern California utility is looking to build a 300-megawatt pilot facility.

Another storage option is pumped hydro. Similar to the compressed air scheme, surplus wind or solar energy is used to pump water uphill. When the energy is needed, the water is released, flows downhill, and turns a turbine.

PG&E already operates one such plant: the Helms Pumped Storage Facility, which can produce 1,212 megawatts of electricity and go from a dead stop to full generation in about 6.5 minutes.

Elkind says that pumped hydro poses some challenges, however. “Mainly, where will we put them?” he asks. “We don't have a lot of water and it's not easy to build new reservoirs.”

California's four-year drought has already had a major impact on its large hydroelectric facilities. In 2014, in-state hydroelectricity production fell 32 percent from 2013 levels, and was down 61 percent from 2011.

That may not be as bad as it seems at first blush. One consequence of the drought is that it may in fact open up land for utility scale solar projects, Hohn says. As territory that was once prime farmland in the state’s Central Valley begins to dry up, installing solar may be one way for farmers there to still get value out of their land, says Hohn.

Although utility-scale solar projects have a lot of potential for helping California reach the 50-percent-renewable benchmark, there are also significant land-use challenges with such projects.

A recent study found that only 15 percent of existing and proposed large-scale solar projects were on ideal sites. “Energy developers put projects where they can easily get land and where they're likely to get a power purchase agreement,” says Elkind. “They're not always thinking about the biological value of the land.”

Elkind added that, “As a state, we haven't figured out what kinds of lands we want to see solar developed on [and how to] steer incentives toward those lands.”

One potential solution is to install more solar in urban environments. Hohn says that is an idea he favors, and he does think that there will be more “solar gardens” in communities. However, he acknowledged that these smaller scale projects are less appealing financially to developers.

Another challenge, says Elkind, will be meeting the goal without increasing fossil fuel usage. Advances in the various storage technologies will be needed to handle the intermittency of renewables without relying on natural gas for stability. In addition, the state will need to integrate its renewable grid with other western states, figure out how to link grid operators, and set up the markets to trade surplus renewable electricity, he said.

“We've learned a lot of lessons getting to 20 percent renewable energy,” Elkind says. And “we're learning as we push toward 50 percent.”

The Conversation (0)
This photograph shows a car with the words “We Drive Solar” on the door, connected to a charging station. A windmill can be seen in the background.

The Dutch city of Utrecht is embracing vehicle-to-grid technology, an example of which is shown here—an EV connected to a bidirectional charger. The historic Rijn en Zon windmill provides a fitting background for this scene.

We Drive Solar

Hundreds of charging stations for electric vehicles dot Utrecht’s urban landscape in the Netherlands like little electric mushrooms. Unlike those you may have grown accustomed to seeing, many of these stations don’t just charge electric cars—they can also send power from vehicle batteries to the local utility grid for use by homes and businesses.

Debates over the feasibility and value of such vehicle-to-grid technology go back decades. Those arguments are not yet settled. But big automakers like Volkswagen, Nissan, and Hyundai have moved to produce the kinds of cars that can use such bidirectional chargers—alongside similar vehicle-to-home technology, whereby your car can power your house, say, during a blackout, as promoted by Ford with its new F-150 Lightning. Given the rapid uptake of electric vehicles, many people are thinking hard about how to make the best use of all that rolling battery power.

The number of charging stations in Utrecht has risen sharply over the past decade.

“People are buying more and more electric cars,” says Eerenberg, the alderman. City officials noticed a surge in such purchases in recent years, only to hear complaints from Utrechters that they then had to go through a long application process to have a charger installed where they could use it. Eerenberg, a computer scientist by training, is still working to unwind these knots. He realizes that the city has to go faster if it is to meet the Dutch government’s mandate for all new cars to be zero-emission in eight years.

The amount of energy being used to charge EVs in Utrecht has skyrocketed in recent years.

Although similar mandates to put more zero-emission vehicles on the road in New York and California failed in the past, the pressure for vehicle electrification is higher now. And Utrecht city officials want to get ahead of demand for greener transportation solutions. This is a city that just built a central underground parking garage for 12,500 bicycles and spent years digging up a freeway that ran through the center of town, replacing it with a canal in the name of clean air and healthy urban living.

A driving force in shaping these changes is Matthijs Kok, the city’s energy-transition manager. He took me on a tour—by bicycle, naturally—of Utrecht’s new green infrastructure, pointing to some recent additions, like a stationary battery designed to store solar energy from the many panels slated for installation at a local public housing development.

This map of Utrecht shows the city’s EV-charging infrastructure. Orange dots are the locations of existing charging stations; red dots denote charging stations under development. Green dots are possible sites for future charging stations.

“This is why we all do it,” Kok says, stepping away from his propped-up bike and pointing to a brick shed that houses a 400-kilowatt transformer. These transformers are the final link in the chain that runs from the power-generating plant to high-tension wires to medium-voltage substations to low-voltage transformers to people’s kitchens.

There are thousands of these transformers in a typical city. But if too many electric cars in one area need charging, transformers like this can easily become overloaded. Bidirectional charging promises to ease such problems.

Kok works with others in city government to compile data and create maps, dividing the city into neighborhoods. Each one is annotated with data on population, types of households, vehicles, and other data. Together with a contracted data-science group, and with input from ordinary citizens, they developed a policy-driven algorithm to help pick the best locations for new charging stations. The city also included incentives for deploying bidirectional chargers in its 10-year contracts with vehicle charge-station operators. So, in these chargers went.

Experts expect bidirectional charging to work particularly well for vehicles that are part of a fleet whose movements are predictable. In such cases, an operator can readily program when to charge and discharge a car’s battery.

We Drive Solar earns credit by sending battery power from its fleet to the local grid during times of peak demand and charges the cars’ batteries back up during off-peak hours. If it does that well, drivers don’t lose any range they might need when they pick up their cars. And these daily energy trades help to keep prices down for subscribers.

Encouraging car-sharing schemes like We Drive Solar appeals to Utrecht officials because of the struggle with parking—a chronic ailment common to most growing cities. A huge construction site near the Utrecht city center will soon add 10,000 new apartments. Additional housing is welcome, but 10,000 additional cars would not be. Planners want the ratio to be more like one car for every 10 households—and the amount of dedicated public parking in the new neighborhoods will reflect that goal.

This photograph shows four parked vehicles, each with the words \u201cWe Drive Solar\u201d prominently displayed, and each plugged into a charge point.Some of the cars available from We Drive Solar, including these Hyundai Ioniq 5s, are capable of bidirectional charging.We Drive Solar

Projections for the large-scale electrification of transportation in Europe are daunting. According to a Eurelectric/Deloitte report, there could be 50 million to 70 million electric vehicles in Europe by 2030, requiring several million new charging points, bidirectional or otherwise. Power-distribution grids will need hundreds of billions of euros in investment to support these new stations.

The morning before Eerenberg sat down with me at city hall to explain Utrecht’s charge-station planning algorithm, war broke out in Ukraine. Energy prices now strain many households to the breaking point. Gasoline has reached $6 a gallon (if not more) in some places in the United States. In Germany in mid-June, the driver of a modest VW Golf had to pay about €100 (more than $100) to fill the tank. In the U.K., utility bills shot up on average by more than 50 percent on the first of April.

The war upended energy policies across the European continent and around the world, focusing people’s attention on energy independence and security, and reinforcing policies already in motion, such as the creation of emission-free zones in city centers and the replacement of conventional cars with electric ones. How best to bring about the needed changes is often unclear, but modeling can help.

Nico Brinkel, who is working on his doctorate in Wilfried van Sark’s photovoltaics-integration lab at Utrecht University, focuses his models at the local level. In his calculations, he figures that, in and around Utrecht, low-voltage grid reinforcements cost about €17,000 per transformer and about €100,000 per kilometer of replacement cable. “If we are moving to a fully electrical system, if we’re adding a lot of wind energy, a lot of solar, a lot of heat pumps, a lot of electric vehicles…,” his voice trails off. “Our grid was not designed for this.”

But the electrical infrastructure will have to keep up. One of Brinkel’s studies suggests that if a good fraction of the EV chargers are bidirectional, such costs could be spread out in a more manageable way. “Ideally, I think it would be best if all of the new chargers were bidirectional,” he says. “The extra costs are not that high.”

Berg doesn’t need convincing. He has been thinking about what bidirectional charging offers the whole of the Netherlands. He figures that 1.5 million EVs with bidirectional capabilities—in a country of 8 million cars—would balance the national grid. “You could do anything with renewable energy then,” he says.

Seeing that his country is starting with just hundreds of cars capable of bidirectional charging, 1.5 million is a big number. But one day, the Dutch might actually get there.

This article appears in the August 2022 print issue as “A Road Test for Vehicle-to-Grid Tech.”

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