The best of EcoWatch, right in your inbox. Sign up for our email newsletter!
Rooftop Solar and EVs Save Water and Cut Pollution: Better Use of Data Will Optimize the Benefits
By Beia Spiller
Thanks to improvements in technology, it's easier than ever to be green.
Solar panels and electric vehicles (EVs) are two prime examples of technologies that can help people minimize their environmental footprint, without sacrificing comfort or having to radically change their daily behavior. But the question still remains: How much of an environmental benefit do these technologies actually produce? And, are there actions that owners of these technologies can take to minimize their pollution footprint even more?
A new paper by my colleagues and me, recently published in Energy Economics, attempts to answer these two questions for households in Austin, Texas. These homes are part of Pecan Street Inc., a living smart-grid laboratory with the largest customer energy-use database on the planet. Using detailed household-level data from 2013-2015, we were able to track solar panel performance and EV use and charging patterns, and match these actions to two important environmental impacts: water use and greenhouse gas (GHG) emissions.
Our paper confirms that, in Texas, using residential solar panels consumes less water and pollutes the air less than using the central-grid power (based on its electricity sources during those years), and driving an EV instead of a gasoline vehicle generally reduces the household's water and emission footprint, even though EVs charge from the grid. Moreover, our analysis demonstrates how carefully examining energy-use data can help us make sure we're maximizing clean energy's benefits.
People may know that burning fossil fuels—whether to create electricity or drive gasoline vehicles—emits gases that pollute the air. But you may ask, how do the central electric grid and cars use water?
Water is used to produce many forms of energy, including both fossil-fuel based electricity and gasoline. For electricity generation in a natural gas or coal plant, large quantities of water are used for process-related needs, as well as to cool the power plant. The production and refinement of gasoline also uses a lot of water; in fact, we calculate that it takes about four gallons of water to produce one gallon of gasoline.
Wind and solar PV, on the other hand, need virtually no water to create power, and they do not emit GHGs or other pollutants in the process.
The solar findings
Because solar panels consume no water and emit no pollution, installing a solar panel allows a household to reduce both the water use and air pollution associated with grid electricity.
In fact, we find that solar panels in Texas have a very large and positive impact on both water and GHG emissions, reducing a household's combined footprint by about 75 percent (a previous Pecan Street study also found solar panels reduce homes' water-intensity by approximately 79 percent).
In Texas during the day when the sun shines, the main power sources are natural gas and coal. So, if you're getting some or all of your power from your own solar panels, you're avoiding using that high-GHG emitting, thirsty electricity from the grid.
Importantly, we find that a household can improve its environmental footprint even further by facing its solar panels south, capturing more sun throughout the day. However, this can conflict with local electric system attempts to maximize production during periods of peak demand, generally in the afternoon when people are getting home from school and work. For example, Pecan Street provided subsidies for solar owners in their community who face their panels west, thereby generating more electricity during that afternoon period, but less overall over the course of the day. Less electricity from the solar panels overall means more water use and emissions from the central grid.
This contradiction highlights the importance of analyzing data. A better understanding of hourly energy usage and emissions can inform electric system policies and pricing that lead to a reduction in total costs, including those related to the environment.
The EV findings
Understanding electric vehicles' environmental impact by these measurements is a bit trickier, because EVs avoid gasoline (thereby reducing water use and GHGs), but they also charge using the grid, which in Texas is largely powered by fossil fuels (thereby increasing both water use and GHG emissions).
Our paper therefore tested whether, on net, EVs are good for the environment—in this case by reducing water use and GHGs—in Texas.
To be able to quantify the environmental benefits of EVs, we needed to think about what vehicle the household would have driven had it not purchased an EV. Vehicle owners have many choices in the marketplace, and fuel efficiency is not the only deciding factor. For example, a family with many children or someone who needs to haul a trailer may not be willing to trade off vehicle size or horsepower in favor of a more compact EV. On the other hand, a person who likes small cars may place greater weight on fuel efficiency; this person's alternative to an EV is more likely to be a hybrid, whereas the large family's alternative vehicle is more likely to be a minivan.
Understanding what the alternative choice would have been is key in measuring the environmental impact of an EV: the less fuel-efficient the alternative vehicle, the better the EV is for the environment. For example, if you switch from driving a gas-guzzler to an EV, that's more beneficial than someone switching from a hybrid. In fact, we find that if the household's alternative-choice vehicle is a hybrid, using an EV can actually increase its net water use—the reduction in gasoline use is very small due to the high efficiency of the hybrid, and the EV is charged with thirsty grid electricity.
That said, we find that EVs always reduce GHG emissions, on net, regardless of the alternative vehicle. Although the benefits do vary largely with the efficiency of the alternative vehicle, they would always increase the cleaner the grid becomes.
Our findings related to EVs suggest three distinct policy solutions:
- Ensure that vehicles such as SUVs and trucks have electric offerings, which manufacturers like Tesla and Volvo are already working on. This will help steer those who require larger sized vehicles towards choosing an electric option, thereby drastically reducing their environmental footprint.
- When people purchase a new EV, a well-designed rebate program that pays them to surrender their inefficient vehicle to be destroyed (such as an improved "Cash-for-Clunkers" program from 2009) could lead to even greater reductions in the environmental impacts of driving.
- Ensure more grid electricity comes from solar and wind, thereby further improving the water- and emission-intensity of EVs. Especially as EV adoption increases, having a clean grid will help us achieve a more environmentally-friendly transportation sector.
Solar panels and electric vehicles will help pave the way to a cleaner future, but we must dig into the details to ensure we maximize the environmental benefits. The more data we have and examine, the better that decision-makers can design energy programs and incentives to improve our environmental footprint.
EcoWatch Daily Newsletter
By Patti Lynn
2018 was a groundbreaking year in the public conversation about climate change. Last February, The New York Times reported that a record percentage of Americans now believe that climate change is caused by humans, and there was a 20 percentage point rise in "the number of Americans who say they worry 'a great deal' about climate change."
England faces an "existential threat" if it does not change how it manages its water, the head of the country's Environment Agency warned Tuesday.
By Jessica Corbett
A new analysis revealed Tuesday that over the past two decades heat records across the U.S. have been broken twice as often as cold ones—underscoring experts' warnings about the increasingly dangerous consequences of failing to dramatically curb planet-warming emissions.
By Madison Dapcevich
Ask any resident of San Francisco about the waterfront parrots, and they will surely tell you a story of red-faced conures squawking or dive-bombing between building peaks. Ask a team of researchers from the University of Georgia, however, and they will tell you of a mysterious string of neurological poisonings impacting the naturalized flock for decades.
The initial cause of the fire was not yet known, but it has been driven by the strong wind and jumped the North Santiam River, The Salem Statesman Journal reported. As of Tuesday night, it threatened around 35 homes and 30 buildings, and was 20 percent contained.
The unanimous verdict was announced Tuesday in San Francisco in the first federal case to be brought against Monsanto, now owned by Bayer, alleging that repeated use of the company's glyphosate-containing weedkiller caused the plaintiff's cancer. Seventy-year-old Edwin Hardeman of Santa Rosa, California said he used Roundup for almost 30 years on his properties before developing non-Hodgkin's lymphoma.
"Today's verdict reinforces what another jury found last year, and what scientists with the state of California and the World Health Organization have concluded: Glyphosate causes cancer in people," Environmental Working Group President Ken Cook said in a statement. "As similar lawsuits mount, the evidence will grow that Roundup is not safe, and that the company has tried to cover it up."
Judge Vince Chhabria has split Hardeman's trial into two phases. The first, decided Tuesday, focused exclusively on whether or not Roundup use caused the plaintiff's cancer. The second, to begin Wednesday, will assess if Bayer is liable for damages.
"We are disappointed with the jury's initial decision, but we continue to believe firmly that the science confirms glyphosate-based herbicides do not cause cancer," Bayer spokesman Dan Childs said in a statement reported by The Guardian. "We are confident the evidence in phase two will show that Monsanto's conduct has been appropriate and the company should not be liable for Mr. Hardeman's cancer."
Some legal experts said that Chhabria's decision to split the trial was beneficial to Bayer, Reuters reported. The company had complained that the jury in Johnson's case had been distracted by the lawyers' claims that Monsanto had sought to mislead scientists and the public about Roundup's safety.
However, a remark made by Chhabria during the trial and reported by The Guardian was blatantly critical of the company.
"Although the evidence that Roundup causes cancer is quite equivocal, there is strong evidence from which a jury could conclude that Monsanto does not particularly care whether its product is in fact giving people cancer, focusing instead on manipulating public opinion and undermining anyone who raises genuine and legitimate concerns about the issue," he said.
Many regulatory bodies, including the U.S. Environmental Protection Agency, have ruled that glyphosate is safe for humans, but the World Health Organization's International Agency for Research on Cancer found it was "probably carcinogenic to humans" in 2015. A university study earlier this year found that glyphosate use increased cancer risk by as much as 41 percent.
Hardeman's lawyers Jennifer Moore and Aimee Wagstaff said they would now reveal Monsanto's efforts to mislead the public about the safety of its product.
"Now we can focus on the evidence that Monsanto has not taken a responsible, objective approach to the safety of Roundup," they wrote in a statement reported by The Guardian.
Hardeman's case is considered a "bellwether" trial for the more than 760 glyphosate cases Chhabria is hearing. In total, there are around 11,200 such lawsuits pending in the U.S., according to Reuters.
University of Richmond law professor Carl Tobias told Reuters that Tuesday's decision showed that the verdict in Johnson's case was not "an aberration," and could possibly predict how future juries in the thousands of pending cases would respond.