Battery Flashcards
ampere hour (Ah)
unit for cell capacity, represents the charge transferred by a steady current of 1 ampere flowing for one hour
kWhdc
kwh on the DC side, capacity
kWac
kw on the AC side
cask effect
how SOC (state of charge) or the performance of one battery rack influences adjacent racks (such as thermal issues
rack charge and discharge
the ability to INDIVIDUALLY charge or discharge each rack within an ESS, important for precision O&M (sungrow is 100%, which means each rack can be independently managed, charged and discharged )
RTE
round trip efficiency, measures efficiency, the actual proportion of energy that is retained after it has been stored and then retrieved from an ESS, it’s a ratio of the energy output to input expressed as percentage
DCDC unit
DC to DC, a component that adjusts voltage levels within a DC system
external aux
the external auxiliary equipments, like cooling, control system, etc
HV side with external aux
high voltage side of system requires additional external auxiliary equipment to operate
degradation profile
developers need this to proceed on deals. Sungrow’s pt2 and pt1 same degradation profile, no testing yet on pt2
islanding
sungrow pt2.0 can’t do this yet
LCOS
levelized cost of storage, a metric used to calculate the cost of storing electricity within an ESS, analogous to LCOE (levelized cost of energy)
- components: CAPEX, OPEX< efficiency, cycle life, and useful capacity
useful capacity
the amount of energy that can actually be stored and retrieved from its total nominal capacity. example: a battery has a nominal capacity of 10kwh but only 9kwh is accessible for discharge to due to operational limits. determined by: Depth of Charge (DoD), which is percentage of battery that can be used without adversely affecting its lifespan or performance. example: many lithium-ion batteries have recommended DoD of about 80-90% to prevent excessive wear.
it’s different from round trip efficiency: one is about quantity one is about quality. a battery with high UC but low RTE might deliver a lot of energy but loss would also be significant, making it less efficient.
Summarize the distinction between Useful Capacity and RTE in one sentence
While useful capacity is a measure of the energy available for discharge from the total energy capacity, RTE is concerned with how much of that energy remains after the storage process. In other words, useful capacity is about quantity, while RTE is about the quality of that quantity after the storage cycle.
