warm thoughts


Written on: August 30, 2022

A new report provides architects and engineers with data on the emissions performance of different types of generators.

As climate change and resulting extreme weather events wreak environmental and economic havoc on the globe, power outages have become one of the most direct and dire problems to solve.

In California, for example, public safety power shutoffs have been implemented as a stopgap measure for mitigating wildfires that have greatly intensified in recent years because of climate change. And the U.S. as a whole isn’t faring much better, with the country enduring more blackouts (both unplanned and scheduled) than any other developed nation.

To deal with the increase in power outages, much of the focus has turned to power generators as a partial solution. But with all the options available, which fuel source is ideal? Power Generation: The Emissions Shifting Problem, a new report from the Propane Education & Research Council (PERC), sheds light on this question with evidence that shows propane can provide emissions and resilience benefits, particularly compared with diesel.

“Replacing diesel assets with propane-powered equipment will continue to push us toward significant air quality improvement and decarbonization,” says Gokul Vishwanathan, author of the report and director of research and sustainability at PERC.

As architects and engineers evaluate power generation solutions that can provide resilience in the face of outages — and help in the battle against climate change — this report provides clear data to help inform their decisions. Here are some of the highlights.

1. Propane can displace diesel generators in many markets and significantly improve air quality, mainly by lowering the release of nitrogen oxides (NOx) and particulate matter into the air. The use of backup generators has surged in recent years. In California, for example, the number of backup generators has increased 34 percent from 2018 to 2021 in the Bay Area Quality Management District and 22 percent from 2020 to 2021 in the South Coast Air Quality Management District, according to M.Cubed, an economic and public policy consulting group. Currently, 90 percent of the backup generators in both the districts are powered by diesel.

But this prevalence of diesel generators doesn’t mean they’re the best choice for architects and engineers worried about air quality. Propane engines can improve air quality by providing significant particulate matter and NOx emissions reductions relative to diesel, according to the PERC report. Depending on whether the engine is optimized for propane, propane generators can also provide CO2 emissions reductions. (See the report for the full comparison data.)

2. Dedicated propane engines and renewable propane can help with decarbonization. Unlike generators that have been retrofitted to work with propane, dedicated propane engines are designed to work with the fuel from the start and are optimized to reduce CO2 emissions while increasing efficiency.

And there’s more than one type of propane available to put in that generator. Renewable propane, produced from renewable feedstocks such as used cooking oil and animal tallow using hydrotreated vegetable oil process, is identical to conventional propane structurally and functionally. But it can lead to a 50–70 percent reduction in lifecycle CO2 emissions compared with conventional diesel and can accelerate deep decarbonization. And to add to the fuel’s flexibility, blends of conventional and renewable propane are also practical solutions for accelerating the crucial process of decarbonization.

3. Combined heat and power (CHP) solutions provide significant reductions in NOx, particulate matter, and CO2 emissions. CHP systems generate power with higher efficiency by reusing the engine’s exhaust to create heat for buildings or hot water. Propane is used for several CHP solutions in the 1 kilowatt–1 megawatt range. Typically, the engines employed have higher thermal efficiency (more than 30 percent fuel to electrical conversion efficiency), higher durability (40,000–60,000 hours), and low emissions. And depending on the unit, a 16–43 percent reduction in CO2 emissions can be achieved.

When considering resilience, CHP solutions are a great fit for residential, commercial, and industrial applications by providing not only electricity but also heat, hot water, and cooling during power outages, depending on the model and setup. When used in CHP mode, these solutions can have more than 80 percent fuel conversion efficiency to electricity and useful heat.

In addition, propane opens the door for fuel cells, a technology that boasts high efficiency and low emissions — and that seldom runs on diesel.

For a deeper dive into these insights and more, download the full report: Power Generation: The Emissions Shifting Problem.