Last week, the Sierra Club continued to push back against the rush to replace one dirty fossil fuel with another. Arizona Public Service Company (APS) is in the process of permitting a new natural gas “peaker” plant in Tempe, Arizona. The proposed Ocotillo plant would exacerbate air quality in an area that already violates standards for particulate matter (soot) and ozone. It would also be allowed to emit greenhouse gases at a rate that is just shy of a coal plant.
According to the EPA, modern coal plants can achieve greenhouse gas emission rates of around 1,700 lb CO2/MWh (pounds of CO2 per megawatt-hour). In contrast, natural gas power plants can achieve greenhouse gas emission rates as low as 800 lb CO2/MWh at combustion (i.e., not accounting for emissions from extraction and transport of natural gas). Even better, renewable energy, energy efficiency, and clean energy storage can provide electricity with zero greenhouse gas emissions.
The proposed Ocotillo plant would be allowed to emit greenhouse gases at a rate of 1,690 lb CO2/MWh. That’s right -- almost the same as a coal plant. Why such an inefficient plant? APS is taking a step backwards to try and meet the challenges of the modern electric grid. APS claims that variability in renewable energy production requires them to match generation with a resource that can turn up and down very quickly. In order to do that, they say they need to build a large gas plant -- called a “peaker” -- that sits there and idles inefficiently for a long time. Then, if solar generation drops off, APS would quickly rev up the peaker plant to match load. It’s kind of like idling a drag racing car at the starting gate for hours and hours; you waste a lot of fuel and create a lot of emissions by revving the engine without going anywhere.
There is a much better option that APS needs to look at. Instead of relying on a series of inefficient gas turbines just waiting around to be needed, the utility should install modern energy storage batteries. This technology is gaining ground quickly, and can provide instantaneous and clean electricity generation to the grid when it’s needed. Even better, you can charge the batteries with zero-emission clean energy during periods when the sun is shining strong. Imagine replacing that idling drag car with a Tesla. You can wait at the starting gate without burning any fuel, and then when it’s time to go, you can still hit zero to sixty in a heartbeat.