In recent years, Mammoth Cave National Park has lessened its dependence on the electrical grid through the addition of solar panels.

When the new Visitor Center was constructed in 2012, the park included roof solar panels that now offset an estimated 25 percent of the annual facility electric use. The park has since added solar panel sites to power parking lot lights and provide part of the energy needs for employee housing and park offices.

Now, park officials eye opportunities to continue this progress with plans to install solar-powered charging stations for electric vehicles in the Visitor Center parking lot. So far, the solar panels are in place, but the actual charging stations await funding.

“Any new construction we’re looking at or buildings we’re redoing, we consider if solar panels are something we can use,” said park spokeswoman Molly Schroer.

But due to current funding limitations, all projects that include solar panels, which could include the ranger office and a new curatorial building, remain in the planning stage.

“Our hope is to have some of the projects started by 2021,” Schroer said.

The park will continue to explore opportunities for clean – or at least cleaner – energy when designing new sites and purchasing new vehicles.

Since 1999, the park has used ethanol, biodiesel and propane in park vehicles and boats.

Park buses transport people from the Visitor Center to cave entrances using propane “autogas,” which is liquified petroleum gas. Compared to a diesel equivalent, a 2014 U.S. Department of Energy study revealed that propane buses saved school districts 50 percent on a cost-per-mile basis for fuel and maintenance. The buses also showed a 15 percent reduction in lifecycle greenhouse gas emissions.

The park also has six low-speed “neighborhood” electric vehicles and one hybrid electric vehicle. Electric vehicle emissions depend on the source of the electricity.

Using the park ZIP code and the average miles per gallon, battery electric vehicles produce 197 grams of equivalent carbon dioxide emissions, plug-in hybrid electric vehicles produce 232 grams, and gasoline-only cars produce 381 grams of equivalent CO2, according to the Union of Concerned Scientists “EV Emissions Tool.”

Nationally, the average annual emissions for an all-electric vehicle are 4,352 pounds of carbon dioxide equivalent compared to 11,435 pounds for gasoline vehicles. In Kentucky, the average annual emissions for all-electric vehicles is 8,196 pounds of CO2 equivalent, as the state electricity grid runs on about 75 percent coal, according to the U.S. Department of Energy.

Creating a cleaner grid and reducing harmful emissions is critical in national parks.

Steps to create a cleaner grid and reduce harmful emissions in national parks are critical. Average temperatures in national parks are increasing at twice the rate as the rest of the nation while annual rainfall decreases further – which has resulted in worse wildfires, melting glaciers and impacted vegetation, according to a 2018 University of California at Berkeley and University of Wisconsin-Madison study.

Earlier this year, a new National Parks Conservation Association report suggested that air pollution burdens Mammoth Cave with “significant concern” for visibility, nature and climate.

“For human health and safety, the air we breathe is important for both visitors and people who work at the park,” Tim Pinion, chief of sciences and resource management, said in a previous interview about the report. “Clean air is (also) important because there can be impacts to species and plants in the park.”