Energy and Environment Week 11

geothermal

Geothermal applications

Electricity generation and heating

Geothermal ingredients

• heat

• fluid (in situ)

• permeability

Geothermal capacity

75% capacity factor

• has potential to act as a baseload. Typical geothermal well (conventional) will produce between 5 and 8 MW

Geothermal future

• Improved well targeting to expand conventional geothermal

• Enhanced geothermal systems (EGS)

• Supercritical (aka super hot-rock) geothermal

most of the eastern half of the country is not reliable for geothermal

Conventional geothermal

accessing geothermal heat flow in brittle rock close to the surface (<3 km at 200C)

Hot rock geothermal

Deep drills into the earth access higher levels of geothermal heat flow (10-20km at 500+C) at the cost of more risk but more reward. Rock is more ductile at these depths

Enhanced geothermal

fractures underground rock to create geothermal reservoirs (lower cost) rather than relying on natural ones. May have proppants to keep fractures open

horizontal drilling occurs as well; fluids are benign and produces no emissions

Electric heat pump

bidirectional, all-in-one heating and cooling unit. Draws in heat in winter and acts as AC in summer, circulating cool air inside

causes GHG emissions in leaking and venting of methane

Electric heat pump types

• air source

• ground (geothermal) source

Ground source heat pumps

Can be vertical or horizontal. Energy is extracted via turbines

Heat pump concerns

Land footprint, emissions, effect on water resources, wastewater

Nuclear weapons

Designed to release a large amount of energy in a short time. Use >90% uranium or plutonium. Cause extensive contamination

Nuclear reactors

Release, steady, controlled stream of heat from fission for long duration generation. Only use 3-5% uranium and provide safe fuel storage

Nuclear power

energy released from radioactive decay of elements (uranium). Decay releases a lot of energy and fission can occur spontaneously