
414 Glossary
directly to electrical energy. Flow batteries can be rapidly “recharged”
by pumping new electrolyte into the cells while simultaneously
recovering the spent electrolyte for chemical re-energization.
y ash (FA; from coal-burning power plants): The light mineral residue
from the combustion of coal. Its composition varies widely, depend-
ing on the type of coal used and the degree of combustion. FA leaves
the burner in the exhaust stack and is generally trapped with elec-
trostatic precipitators. FA contains a large percentage of amorphous
and crystalline silicon dioxide (SiO
2
), calcium oxide (CaO) (unslaked
lime), Fe
2
O
3
, a