Basic Terminology 27 The other legislative reason automakers began looking at a portfolio of solutions to improve fuel economy was the US Corporate Average Fuel Economy (CAFE) standards that were enacted in 1975. These standards were originally put in place as a result of the Organization of the Petroleum Exporting Countries (OPEC) oil embargo of the early 1970s in an effort to reduce the US reliance on foreign oil. Initially the law required that automakers passenger fleets achieve 18 miles per gallon (MPG) by 1978, increasing to 27.5 mpg by 1985.
However, during the Regan administration, the law was relaxed down to 26 mpg and then increased again to 27.5 mpg by 1990 and then for over 21 years the CAFE laws remained fixed at 27.5 mpg. In 2006, the CAFE laws were reformed and a new manner of measuring CAFE was installed in 2011, by vehicle footprint instead of weight. And a new set of fuel economy targets were put in place between 2011 and 2015 raising the target from 27.5 mpg up to 35.5 mpg by 2015 (2016 model year).
In 2012, the next generation of standards were agreed to that define the required improvements between the 2017 model year and 2025 model year, resulting in a fleet average fuel economy in 2025 of 54.5 mpg (National Highway Traffic Safety Administration, 2014). Stationary and Grid Terminology We will also briefly describe several of the key terms that are used in the large stationary energy storage market before we delve into the battery specific terminology. Stationary and grid-based energy storage generally refer to the large, often megawatt-sized systems that utility companies put in place in order to provide several functions to support the grid opera- tion.
These functions include providing storage for intermittent and renewable generation sources such as wind and solar (renewables), providing fast demand response, load leveling, managing the power quality, and ensuring reliability of their power generation services. The term Community Energy Storage (CES) refers to a relatively small energy storage device that often ranges from about 25 kWh up to about 100 kWh in size. This technology is intended to be used by utility companies to install capacity in specific neighborhoods where they see increased demand and/or that are at the periphery of the grid.
This enables both “islanding,” the ability to operate a microgrid independent of the larger grid, as well as support during downed power events. One organization, the Energy Storage Association (ESA), has pub- lished an “open-source” set of requirements for these types of application in an effort to begin industry standardization and communization (Energy Storage Association, 2014). The CES falls into the category of energy storage systems (ESSs) referred to as Distributed Energy Storage (DES) systems. In general, the DES refers to systems much larger than the CES ranging from hundreds of kilowatt hours up to megawatt hours (MWh) of installed capacity.
The DES systems are generally installed at utility-owned location such as the electrical substations and offer some of the same benefits as the CES systems, only at a much greater scale.