Differentiating the Effects of Climate Change-Induced Temperature and Streamflow Changes on the Vulnerability of Once-Through Thermoelectric Power Plants.

Thermoelectric power plants with once-through cooling systems generated 30% (∼300 GW) of U.S. electricity in 2016. Factors that reduce once-through cooling capacity and thus power output are environmental regulations, warming surface waters, and drought. The latter two may become more frequent as global climate changes. Previous research indicates that reduction in power plant capacity caused by environmental regulations can be significant while that by surface water warming is minor. Here, we address the effect of droughts on power output, which until now has remained conflated with temperature impacts. We do this using a widely used electricity generation model alongside hourly operational and meteorological data for 52 once-through plants located across the U.S. The effect of drought on plant output is examined for different water-availability and temperature scenarios, with and without regulations on plant water discharge. We find that if surface waters warm 3 °C and river discharges drop 20%, droughts would account for ≤20% of total capacity reduction depending on the plant, warming surface waters ≤2.3%, and environmental regulations up to 80%. This suggests that maintaining environmental regulations will require the continued conversion of plant cooling systems from once-through to recirculating, and mitigating climate impacts will require more stringent drought-specific watershed management.

Effects of Environmental Temperature Change on the Efficiency of Coal- and Natural Gas-Fired Power Plants.

Modeling studies predict that droughts and hotter water and air temperatures caused by climate warming will reduce the efficiency (η) of thermoelectric plants by 0.12-0.45% for each 1 °C of warming. We evaluate these predictions using historical performance data for 39 open- and closed-loop coal and natural gas plants from across the U.S., which operated under daily and seasonal temperature fluctuations multiples greater than future average warming projections. Seven to 14 years of hourly water (Tw), dry-bulb air (Ta), and wet-bulb air (Twb) temperature recordings collected near each plant are regressed against efficiency to attain estimates of Δη per 1 °C increase. We find reductions in η with increased Tw (for open-loop plants) up to 1 order of magnitude less than previous estimates. We also find that changes in η associated with changes in Ta (open-loop plants) or Twb (closed-loop plants) are not only smaller than previous estimates but also variable; i.e., η rises with Ta or Twb for some plants and falls for others. Our findings suggest that thermoelectric plants, particularly closed-loop plants, should be more resilient to climate warming than previously expected.

A Participatory Science Approach to Evaluating Factors Associated with the Occurrence of Metals and PFAS in Guatemala City Tap Water.

Limited information is available regarding chemical water quality at the tap in Guatemala City, preventing individuals, water utilities, and public health authorities from making data-driven decisions related to water quality. To address this need, 113 participants among households served by a range of water providers across the Guatemala City metropolitan area were recruited as participatory scientists to collect first-draw and flushed tap water samples at their residence. Samples were transported to the U.S. and analyzed for 20 metals and 25 per- and polyfluoroalkyl substances (PFAS). At least one metal exceeded the Guatemalan Maximum Permissible Limit (MPL) for drinking water in 63% of households (n = 71). Arsenic and lead exceeded the MPL in 33.6% (n = 38) and 8.9% (n = 10) of samples, respectively. Arsenic was strongly associated with groundwater while lead occurrence was not associated with location, water source, or provider. One or more PFAS were detected in 19% of samples (n = 21, range 2.1-64.2 ppt). PFAS were significantly associated with the use of plastic water storage tanks but not with location, water source, or provider. Overall, the high prevalence of arsenic above the MPL in Guatemala City tap water represents a potential health risk that current water treatment processes are not optimized to remove. Furthermore, potential contaminants from premise plumbing and storage, including lead and PFAS, represent additional risks requiring further investigation and public engagement.