Glossary: Water & Cooling Terms

Plain definitions of the water and cooling terms used across the MetroVolt water story, from blowdown to withdrawal.

Cooling and heat rejection

• Cold sink: the reservoir that receives a heat engine's rejected heat
• Condenser: the component that condenses turbine exhaust steam, the main cooling load in a steam plant
• Rankine cycle: the steam cycle of boiler, turbine, condenser, and pump
• Heat rejection: moving waste heat from a plant to the environment
• Latent heat: energy absorbed when water evaporates, the basis of wet cooling

Cooling methods

• Once-through cooling: draws water, passes it once, returns it warmer
• Wet cooling tower: rejects heat by evaporating recirculating water
• Dry cooling (ACC): rejects heat to air with no evaporation
• Hybrid cooling: blends wet and dry to balance water and efficiency
• Closed loop: sealed coolant that carries heat without being consumed

Water accounting

• Withdrawal: water removed from a source, some returned
• Consumption: water permanently lost, mostly evaporated
• Makeup water: water added to replace evaporation and blowdown
• Blowdown: concentrated water discharged from an evaporative loop
• WUE: water usage effectiveness, litres consumed per unit of IT energy
• PUE: power usage effectiveness, total facility power per unit of IT power

Aquatic impacts

• Impingement: organisms trapped against an intake screen
• Entrainment: small organisms drawn through the plant
• Thermal discharge: warmed cooling water returned to a water body

Burner terms

• Direct energy conversion (DEC): capturing charged-particle energy as electricity without a heat engine
• Neutron fraction: share of fusion power carried by neutrons; 5.44% for the D-3He burner
• Tandem mirror: the burner's magnetic confinement geometry, 26.49 T plug and 17 T throat
• Residual heat: the small heat load, from neutrons and losses, that the burner still must cool