Wednesday, September 20, 2023

Dead Zone, Late Season Update

The “Dead Zone” of the Chesapeake Bay refers to a volume of hypoxic water that is characterized by dissolved oxygen concentrations less than 2 mg/L, which is too low for aquatic organisms such as fish and blue crabs to thrive. Within the hypoxic area life of the bay dies and a “Dead Zone” forms. The Chesapeake Bay experiences hypoxic conditions every year, with the severity varying from year to year, depending on nutrient and freshwater flows into the bay, wind, and temperature.

In June researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey announced that they were predicting the 2023 dead zone would be the smallest dead zone on record since 1985.

This week researchers at the Virginia Institute of Marine Science (VIMS) reported that hypoxia in summer 2023 began in mid-May, increased to a moderate level, and then leveled off. They believe that this leveling off resulted from a change in the average wind direction in late-May. Hypoxia has remained at low to moderate levels throughout June, July, and into August. The spring-time nutrient supply to the Bay was relatively low and June was relatively windy, both of which may have contributed to June through August having a low amount of hypoxia. 2023 is turning out to be low hypoxia year for the Bay, we’ll know sometime over the next few months if it turned out to be the lowest on record.

from VIMS

Each year the Maryland Department of Natural Resources measures the actual dissolved oxygen in the Maryland portion of the Chesapeake Bay main stem and the size of the Dead Zone. While the Virginia Institute of Marine Science (VIMS), Anchor QEA and collaborators at UMCES, operate a real-time three-dimensional hypoxia forecast model using measured inputs that predicts daily dissolved oxygen concentrations throughout the Bay ( using the National Weather Service wind monitoring data.

Sunday, September 17, 2023

UK keeps Nutrient Neutrality

Nutrient neutrality rules were first introduced in the European Union (EU) in 2017. These rules were designed to stop developers from polluting local wetlands and waterways in protected areas when building homes. When Great Britain left the EU they retained those environmental protection rules to prevent excessive nutrient pollution of vulnerable waterways and wetlands.

Excessive amounts of nutrients can lead to a “Dead Zone” which refers to a volume of hypoxic water that is characterized by dissolved oxygen concentrations less than 2 mg/L, which is too low for aquatic organisms to thrive. Within the hypoxic area life of the waterway dies and a “Dead Zone” forms. They occur most often in estuaries and coastal waters, but also in inland lakes, rivers, and streams.

 Increasingly water bodies across the globe are experiencing hypoxic conditions every year, with the severity varying from year to year, depending on nutrient and freshwater flows into the water from agriculture, suburban and urban runoff and wastewater treatment/ release, wind, and temperature. Better nutrient control  in wastewater was able to eliminate the Dead Zone in the Thames River.

The current “nutrient neutrality” means that 62 local authorities in the UK cannot allow new developments unless projects in protected areas can be shown to be "nutrient neutral" – not releasing anymore nutrients after the development than before. In practice the rules ensure that any increase in nutrient pollution from stormwater runoff is offset by a reduction in pollution in the same area. This increased the costs for home builders in the UK. The current UK Tory government has been under pressure to increase the country's housing stock, after warnings earlier this year that residential construction could fall to its lowest level since World War II.

So, the Government introduced an amendment in the House of Lords - to the Levelling Up and Regeneration Bill that would have seen the policy removed. The attempt was rejected by the House of Lords members, the peers, over the risk it would pose to the environment. The “nutrient neutrality” rule stands and the government will have to introduce a new bill to try again.

Closer to home, we have the Chesapeake Bay Clean Water Blueprint” the newer and better name for the enforceable pollution limits for nitrogen, phosphorus, and sediment pollution in the Chesapeake Bay (formerly called the Bay TMDL) mandated by the EPA to Virginia and the other five Bay states and the District of Columbia. Each of the jurisdictions created a plan (approved by the EPA) called Watershed Implementation Plans or WIPs, to meet the required reductions in nutrient pollution by 2025. The states agreed to have the 60% of the needed programs and practices in place by 2017, and to complete the job by 2025.

Virginia remains on track to achieve its 2025 pollution-reduction commitments, largely due to aggressive action the Commonwealth took on wastewater treatment plants. Those actions account for over 90% percent the nitrogen and phosphorus reductions since the Blueprint’s establishment. This progress currently keeps Virginia on track overall, even though the Commonwealth is not meeting commitments to reduce polluted runoff from agriculture and urban and suburban areas.

In June researchers from the Chesapeake Bay Program, the University of Maryland Center for Environmental Science, University of Michigan and U.S. Geological Survey announced that they are predicting this year's dead zone will 33% smaller than the historic average (from 1985-2022), which would be the smallest dead zone on record if the forecast proves accurate. This was a feel good moment for the Chesapeake Bay. 

However, the significantly smaller than average size is forecast due in large part to a lack of rainfall and mild drought this past spring. Less rainfall means lower flows of the rivers, but also generally means there is a lower amount of nutrients being washed off the land and into the water. The apparent progress may be temporary. Pollution from stormwater continues to grow with population and increased intensity of rainstorms could end up undermining all our other efforts. 

Wednesday, September 13, 2023

Townhall for PW Climate Plan

A virtual Town Hall on the Draft Community Energy and Sustainability Master Plan (CESMP) will be held at 6:30 p.m. Thursday, September 14, 2023. Sign up here. Prince William Office of Sustainability is seeking feedback from the public on the draft CESMP. The CESMP is being developed to serve as a roadmap for meeting the county’s Climate Mitigation and Resiliency goals to reduce Prince William's greenhouse gas emissions, and increasing resilience to the effects of climate change. These goals include Prince William County achieving 50% of 2005 CO2 emissions by 2030 and net-zero by 2050; but also include plans for adaption to climate change.

I am a member of the Sustainability Commission and ask that you participate in the process and help us build a sustainable future for our children. I am concerned that the draft CESMP relies too heavily on unrealistic and expensive assumptions and the purchasing of carbon credits to meet the climate goals. At the close of the COP-27 meeting the UN Secretary-General Guterres decried and bringing integrity to net-zero commitments by industry, financial institutions, cities and regions and to support a global, equitable transition to a sustainable future.

“Using bogus ‘net-zero’ pledges to cover up massive fossil fuel expansion is reprehensible. It is rank deception. This toxic cover-up could push our world over the climate cliff. The sham must end.” Mr. Guterres said that net-zero pledges should be accompanied by a plan for how the transition is being made. Prince William’s climate goals could be moderated to what is possible for us to achieve. There is hope that Prince William will be able to “bend the curve” if smart decisions are made in the future.

Though the PW Board of County Supervisors have adopted the net-zero pledge of the MWCOG, the decisions they have made within their nexus of control, land use and roads have worked against that resolution.  In fact, decisions made within our county and Loudoun will challenge the goals of the Virginia Clean Economy Act (VCEA). In 2020, the General Assembly passed the Virginia Clean Economy Act (VCEA), which mandated a goal of 100% zero-carbon energy generation by 2050. This actually was to provide the major tool in achieving the County goals. Afterall, if all power was electric and it was carbon free, no problem in achieving net zero.

However, the VCEA is facing challenges that may prevent it from achieving its goals in the stated time frame. According to VA Energy VCEA requires the Commonwealth to retire its natural gas power plants by 2045 (Dominion) and 2050 (Appalachian Power). These facilities currently comprise 67% of the current baseload generation as well as 100% of the power plants that meet peak demand.  In May when Dominion Energy filed its 2023 Integrated Resource Plan (IRP) with the State Corporation Commission (SCC) Dominion’s  carbon emissions would instead increase  from current levels. In the IRP submitted to the SCC Dominion forecasted that power demand would rise 80% and that peak load will rise from a bit more than 17,000 megawatts now to 27,000 megawatts by 2037. You cannot plan that amount of electricity demand growth 10 years while eliminating generation capacity. It has never been done, and Dominion admits that they need to not only keep all their fossil fuel power generation operating, but  are asking to build more dispatchable fossil fuel generation to meet this forecast demand. Now, the SCC is examining and challenging the growth assumptions that went into that forecast. It remains to be seen what will actually happen.

It appears that electrifying the transportation sector also faces hurdles in cost and accessibility for all along with challenges to electrifying all heating systems county wide. Building more roads and more housing away from transportation hubs will also increase the greenhouse gas footprint of the county.  Beyond the climate resolution, most decisions of the PW BOCS has contributed to the growth in power demand. We need to change directions and bend the curve down.  

Community Energy and Sustainability Master Plan (

Sunday, September 10, 2023

Prince William’s Perennial Streams Drying Up an Ominous Sign

This has been a dry water year (October 1- September 30)- the first one in a decade. The average rainfall in the Potomac River Basin for August was 0.8 inches below normal, but 2.25 inches below normal here in Haymarket. The cumulative rain deficit for the Potomac Basin was about 7.1 inches, but until Friday's deluge here in Haymarket the year-to-date deficit was 11.8 inches. Stream flow across the basin remains below average, and groundwater monitoring indicates below-normal levels.

The Potomac River, its tributaries, reservoirs and the associated groundwater resources are the source of drinking water for the over 6,000,000 people in the Washington Metropolitan area. The Interstate Commission on the Potomac River Basin (ICPRB) coordinates water supply/withdrawal operations for the Potomac River during times of drought and recommends releases of stored water from the jointly owned reservoirs. This is to ensure adequate water supplies for the large Washington metropolitan area water companies and for environmental flow levels.
from Drought Monitor 9/7/2023

Much of the Potomac watershed is currently in D1 drought (beige) according to the U.S. Drought Monitor, though more rain could change this in the usually wet fall. However, current conditions have triggered the Metropolitan Washington Council of Governments (MWCOG) Drought Coordination Technical Committee to consider initiating a “Drought Watch” stage. For now, the Potomac River’s flows are adequate to meet the water demands of the Washington metropolitan area without requiring releases from upstream reservoirs. However, the groundwater, an essential part of our water supply, remains an unknown. Groundwater has very little monitoring and management, but there have been some troubling observations recently.

Round Hill and Purcellville, Virginia whose town water supplies come from a series of wells have in recent days issued water conservation notices to utility customers as dry conditions continued to persist in the region. Round Hill Town staff were concerned that a creek near one of the wells has dried up and that Catoctin Creek in Purcellville had also run dry. Two of the town wells have been pulled off-line in Purcellville to allow them to recharge.

In Haymarket, there were also signs of concern. These pictures were sent to me from the Bull Run Mountain Conservancy last Friday morning. They showed that the perennial streams: Little Bull Run and Catlett’s Branch were dry. Catharpin Creek, another perennial stream, appeared to have been reduced to a series of puddles. This was the driest the Conservancy had seen the streams, ever. This Bull Run watershed is an essential part of the Occoquan watershed that directly supplies water to 800,000 people in Northern Virginia and allows the ICPRB to “ask” Fairfax Water to draw less from the Potomac River in times of need.
Catharpin Creek from BRM Conservancy, M. Kieffer

Catlett's Branch from BRM Conservancy, M. Kieffer

Little Bull Run from BRM Conservancy, M. Kieffer

Generally, groundwater in the Culpeper Basin is renewed each year through precipitation. The water stored in the watershed has always been able to provide adequate water in droughts because historically the withdrawal of water was within the average recharge rate. However,  the only nearby US Geological Survey groundwater monitoring well is no longer stable. The water level has been slowly falling since before the last drought- despite a series of wet years.

USGS Groundwater Monitoring Well 49V1

Properly managed and protected groundwater can be extracted indefinitely and still serve its ecological function. Groundwater recharge through precipitation requires adequate area for infiltration; control of sheet flow created by roads and paved areas, as well as protecting the most geologically favorable infiltration points. In a natural environment much of the precipitation soaks into the ground. Some water infiltrates deep into the ground and replenishes aquifers, which store huge amounts of freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into rivers, creeks, and ponds through the hyporheic zone.

A stream is a living ecosystem. It includes not just the water flowing between the banks but the earth, life and water around and under it. Beneath a living streambed is a layer of wet sediment, small stones and tiny living creatures called the hyporheic zone. Stream water filters down into this dynamic layer between surface water and groundwater, mixing with the groundwater pushing up to feed the rivers during dry spells. Water in the hyporheic zone cannot push up the groundwater if the groundwater level has fallen too low. The stream becomes disconnected from the groundwater. The level of groundwater falls usually due to overuse and reduced recharge.

Maintaining open areas provides areas of groundwater recharge. According to the U.S. Environmental Protection Agency, impervious cover levels of less than 5%-10% can significantly impact watershed health increasing stormwater runoff and reducing groundwater recharge. When runoff volume increases, runoff velocity increases, and peak storm flows increase and you get flooding with soil erosion, fast moving stormwater carrying contamination and reduced or eliminated water infiltration into groundwater. The groundwater is essential as the base flow to the streams and rivers that feed the Occoquan Reservoir during the dry months. Is this a little hint of the beginning of the end.

This weekend's rain might be some small relief in the region and the long-term forecasts call for 1 to 2 inches of rain from the remnants of hurricane Lee in the coming days. The trajectory of Hurricane Lee is still up the air, but it could bring some significant rain as it heads our way. Nonetheless, bad land use decisions and poor management of our water resources is magnifying precipitation changes due to a changing climate.


Wednesday, September 6, 2023

Well Owners are Responsible for their Water

While the U.S. Environmental Protection Agency (EPA) regulates public water systems, the responsibility for ensuring the safety and consistent supply of water for the more than 21 million private wells belongs to the well owner. These responsibilities should include knowing the land and well’s history, testing the water quality annually, and having any well system repairs performed by a well driller licensed or certified by the appropriate state agency where the well is located. In Virginia that is the Department of Professional and Occupational Regulation, DPOR.

Groundwater is the largest and most reliable source of freshwater on earth. In the United States 26% of public supplied water is from groundwater in addition to the homes supplied by private wells pump. It has always been assumed that groundwater is protected and safe, but that turns out to be less and less certain. Groundwater and surface water are connected in many ways, not all of them fully understood. Wastewater from agricultural irrigation is used to recharge groundwater and effluent discharge from wastewater treatment plants is intentionally and accidently finding its way into groundwater. In Los Angeles waste water effluent is used to recharge the groundwater, septic systems return their effluent water to groundwater and several studies by the U.S. Geological Survey (USGS) scientists Paul M. Bradley and Larry B. Barber (and others) have shown that waste water contaminants including pharmaceuticals are carried not only downstream into drinking water intakes, but into the shallow groundwater at least 65 feet from the stream.

Scientists are finding that groundwater aquifers are vulnerable to a wide range of man-made and naturally occurring contaminants. Only some of the substances have regulatory or human health screening levels. The presence of a contaminant in water does not necessarily mean that there is a human-health concern. Whether a particular contaminant in water is potentially harmful to human health depends on the contaminant’s toxicity and concentration in drinking water. Other factors include the susceptibility of individuals, amount of water consumed, and duration of exposure.

The USGS has done lots of groundwater testing over the years. In one study published in 2012 the USGS found that 10 contaminants were widely detected in groundwater and small percentage of the detections were at concentrations greater than human-health recommended levels. Of the ten contaminants, seven were from natural sources and three were man-made. The seven contaminants from natural sources included four geological trace elements (arsenic, manganese, strontium, and boron) and three radionuclides (radon, radium, and gross alpha-particle radioactivity). Radon has been considered several times for regulation in water in the past, but never seems to make the cut.

The three contaminants that exceeded MCLs from mostly man-made sources were nitrate (a nutrient), dieldrin (an insecticide that has been banned by the US EPA, but was previously used for termite control and other applications), and perchloroethene (or PCE, a solvent and degreasing agent used for drycleaning). Each of these contaminants was widely detected in groundwater tested. Nitrate occurs naturally, but most nitrate concentrations greater than 1 milligram per liter (which is one-tenth of the nitrate MCL) originates from man-made sources such as fertilizers, livestock, and human wastewater from septic systems or wastewater treatment plants. 

Installation of private wells is regulated by various state agencies, but these regulations do not require testing the groundwater for a suite of contaminants. State/local agencies that oversee private wells are usually responsible for approving the location of a well, inspecting the well after construction to verify proper grouting and adequate water yield, maintaining records of the well driller’s log, verifying the most basic potability of water by requiring at a minimum bacterial testing. In some regions of the country the Department of Health tests wells annually. 

A drinking water well that is contaminated could significantly impact your health and the value of your property. There are no national regulation and standards for testing a private well; however,  I test my drinking water for all the primary and secondary contaminants of concern to the US EPA under the Safe Drinking Water Act every few years and for a smaller list of 14 contaminants annually.

As the providers of our own water supply we need to serve as our own watch dogs, and ensure our safe water supply, no one else will. Part of the price of your own water supply is maintaining it and testing it. The local health departments have local rules and regulations for the installation of wells and can often help with testing for bacteria and nitrates which are the typical contaminants from septic systems, drain fields and livestock, but as the well owner you will need to take the initiative.

The water well test that was performed when you bought your house probably only tested for bacteria and nitrates (unless you live in New Jersey), which is inadequate to be certain that your water is safe to drink. In addition, the EPA recommends that you test your water well every year for total coliform bacteria, nitrates, total dissolved solids, and pH levels at a minimum. If you suspect other contaminants, test for those. Always use a state certified laboratory that conducts drinking water tests.

On March 14, 2023, EPA announced the proposed National Primary Drinking Water Regulation (NPDWR) for six Per- and Polyfluoroalkyl Substances (PFAS) including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX Chemicals), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS). 

In a recent study by the USGS least one PFAS (of the group tested for) was detected in 20% of private-wells (55/269 tested) and 40% of the public-supply (182/447) samples collected throughout the US. (McMahon et al., 2022). Median cumulative PFAS concentrations (estimated given the detection limits) were comparable between public-supply (median = 7.1 ng/L) and private–well point-of-use tap water (median = 8.2 ng/L ). Private well owners are going to have to address that problem, but first we need to have the public water suppliers figure it out for us and adapt their solutions to our situations. I’m still waiting for an easy to use test before I test my well.

According to the Water Systems Council, you need to monitor the condition of the wellhead and inspect the well system annually. In their publications developed in partnership with the EPA they recommend that you routinely inspect your wellhead several times a year. Check the condition of the well covering, casing and well cap to make sure all are in good repair, leaving no cracks or other entry points for potential pollutants. Note any changes in condition. In addition, you should have the well system, including the pump, storage tank, pipes and valves, and water flow, inspected every 5-10 years by a qualified well driller or pump installer. The soil types, groundwater supply and materials of construction and depth of the well will determine the life of the well. Many wells can continue to produce water supply after a pump has failed and only need a new pump to return to service. This is especially true in areas of hard water where the well pump can have a relatively short life. If you notice a change in your water pressure, it may be time to have your system inspected. Do not ignore any changes in your water supply.

A drop in water pressure can originate in the pressure tank, the pressure switch, the pump or the well and water supply. A loss of charge in the pressure tank can be caused by a leak in the bladder. Pressure to the tank is controlled by an electric switch that turns the pump on when pressure is low and off when the proper tank pressure is reached. A pressure switch can fail. In the well, a diminished water supply can be caused by drop in water level in the well due to drought or over pumping of the aquifer, iron bacteria or other buildup in the pipe, or the well could be failing or a drop in pressure could be caused by a failing or damaged pump. Of course, a drop in water pressure could just be caused by increased demand, if your pump is undersized for the number of plumbing fixtures in the house then using more than one bathroom at a time or doing laundry while hosing down the patio will cause a noticeable drop in water pressure. 

These are just examples of the kind of understanding you need to have when you operate your own water system. When you own a well, you are in charge, you are responsible, you need to be informed. 

Monday, September 4, 2023

Groundwater and a Sustainable U.S.

America is blessed with a wealth of groundwater and surface water that helped create the 20th century America with vast cities, industry and bountiful farmland. That era may be ending. We are using up our groundwater faster than it can be recharged.

The New York Time just published an excellent article: “America Is Draining Its Groundwater Like There’s No Tomorrow.” For the article the Times performed an analysis of over 84,500 of the U.S. Geological Survey (USGS) groundwater monitoring wells. They found an emerging crisis that threatens American prosperity. The Times analysis found: “Nearly half the sites (groundwater levels) have declined significantly over the past 40 years as more water has been pumped out than nature can replenish.”

The Times looked at the water level in the groundwater wells. This level in a well usually fluctuates naturally during the year. Groundwater levels tend to be highest in the early spring in response to winter snow melt and spring rainfall when the groundwater is recharged. Groundwater levels begin to fall in May and typically continue to decline during summer as plants and trees use the available shallow groundwater to grow and streamflow draws water. Natural groundwater levels usually reach their lowest point in late September or October when fall rains begin to recharge the groundwater again and the leaves fall from the trees reducing their need for water. The seasonality for a long time can disguise a diminishing groundwater supply, but over time the falling level emerges.

Though the New York Times focused on irrigated agriculture, which was the first problem to emerge. Groundwater levels are affected by how many other wells draw from the aquifer, how much groundwater is being used in the surrounding area for agricultural, industrial or commercial use, or how much groundwater is being recharged. Development of an area can impact groundwater recharge. Land use changes that increase impervious cover from roads, pavement and buildings does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. Slowly, over time, this can reduce groundwater supply and the water table falls.

Increasing population density increases water use. Significant increases in groundwater use and reduction in aquifer recharge can result in slowly falling water levels that indicate that the water is being used up. Unless there is an earthquake or other geological event groundwater changes are not abrupt and problems with water supply tend to happen very, very slowly as demand increases with construction and industrial use (for data center cooling for example), and recharge is impacted by adding paved roads, driveways, commercial buildings, houses and other impervious surfaces. 

The demand for water rises as population, economic activity and agricultural irrigation grow. However, water resources of accessible water are actually decreasing, due to overuse and pollution. Water resources can be used sustainably only if their volume and variation through time are understood and managed. Groundwater availability varies by location and is limited. Precipitation and soil type determines how much the shallower groundwater is recharged annually. However, the volume of water that can be stored is controlled by the reservoir characteristics of the subsurface rocks. Groundwater may be present today in places with very dry climates because of the nature of the local geology and the historic climate cycles that have occurred through time.

A tiny group of the USGS monitoring wells examined are in Virginia. These wells measure groundwater conditions daily and can be viewed online. Only one of the Virginia wells is within the former Rural Crescent in Prince William County. That well is in the northwest corner of the county just west of Route 15 in the Culpeper groundwater basin. This area supplies groundwater for private drinking water wells, but also is an essential element in Bull Run portion of the Occoquan watershed that provides drinking water to over 800,000 people in Northern Virginia.

from USGS

from USGS

It is clear from the first USGS graph that the groundwater level in well 49V-1  has falling since before 2008. The groundwater is being used up. In the second graph you can see that for decades before that the groundwater level was fairly stable.

Virginia is dependent on groundwater. According to information from Virginia Tech, the Rural Household Water Quality program and the National Groundwater Association approximately 30% of Virginians are entirely dependent on groundwater for their drinking water. In Prince William County about a fifth of residents get their water directly from groundwater, but the health of our watersheds and stream flow are dependent on groundwater, too.  While groundwater is ubiquitous in Virginia it is not unlimited. There are already problems with availability, quality and sustainability of groundwater in Virginia in places such as Fauquier County, Loudoun County and the Coastal Plain. 

Wednesday, August 30, 2023

EV Batteries and PFAS

Yoo, Dong‐Joo, Liu, Qian, Cohen, Orion, Kim, Minkyu, Persson, Kristin A., and Zhang, Zhengcheng. Rational Design of Fluorinated Electrolytes for Low Temperature Lithium‐Ion Batteries. Germany: N. p., 2023. Web. doi:10.1002/aenm.202204182.

Lithium-ion batteries are used widely in portable electronics because of their long operation time, life span, and relatively simple manufacturing process. Lithium-ion batteries operate best at moderate temperatures.  Lithium-ion batteries have also been adopted for electric vehicle use. Lithium-ion batteries are rechargeable, lightweight, and capable of higher energy density than most other available battery types.

They are smaller than the batteries used to start gas-powered vehicles’ internal combustion engines. Of course, as well as starting the car, batteries in electric vehicles keep it moving, and they run the vehicle’s other systems like air conditioning, entertainment, and driver assistance systems.

When lithium-ion batteries are exposed to cold temperatures, their storage capacity –how much energy they can store between charges – drops to approximately 77% at around −5 °F. As the temperature falls, the storage capacity continues to fall. This happens because the ethylene carbonate used as the electrolyte solidifies at about -4 °F.

Now, however, with the spread of electric vehicles, the performance of the lithium-ion batteries at low temperatures has become an issue due to the vast performance difference depending on regions and seasons. To have the entire local transportation fleet knocked out during a polar vortex could be disastrous.

Low temperature performance is one of the most challenging aspects of lithium-ion batteries and EV adoption itself. The lithium-ion batteries used in most battery electric vehicles suffer reduced charging efficiency, significant capacity loss, and accelerated aging in low temperatures. This has a negative effect on electric vehicles’ driving range in cold climates and winter.

The batteries in the electric vehicle also power all the other systems.  Heating the cabin area of the vehicle requires significant amounts of power in cold climates (as does cooling the cabin in hot climates). Testing has shown that, because of this, electric vehicles’ range is reduced to approximately 45% when the external temperature is 5 °F or lower and recharging the batteries is slower.

The authors of the above cited study searched for a solvent that would stay liquid at low temperatures yet still form the crucil SEI barrier over the anode. They have found that replacing the left handed  terminal methyl groups of the ethyl acetate with a  trifluoromethyl group produced the desired effect.

In laboratory tests the ethyl acetate trifluoromethyl was found to be as stable in its energy storage capacity over 400 recharging cycles at  5 °F as the battery containing ethyl acetate was at room temperature. While this solves the problem of EV batteries in winter weather, it potentially adds another PFAS (a forever chemical) to wide spread use. Are we destroying ourselves and planet to reduce greenhouse gasses. The researchers have applied for a patent. You can read the research at the link above.