Geothermal Energy

Question 1

What is the basic process of high temperature geothermal energy?

Answer 1

Water vapour is injected into turbines, generating electricity

water flows into an area closer to heat source

Question 2

What kind of energy system is utilised in areas not as geologically active as iceland?

Answer 2

enhanced geothermal system

Question 3

How does an enhanced geothermal system operate?

Answer 3

beneath a few 100m of insulating low conductivity sediments

water percolated into rock, if there are no existing cracks, hydraulic stimulation is carried out

Question 4

If not for energy production, what is the more widely available low temperature geothermal resources good for?

Answer 4

providing heating

Question 5

For shallow depths, most of the heat extracted is recharged through []

Answer 5

solar

Question 6

At high temp and shallow depth, soil acts as a heat []

Answer 6

sink

Question 7

at low temp and high depth, soil acts as a heat []

Answer 7

source

Question 8

In regards to shallow ground heat sources, how does temperature vary?

Answer 8

less variance as little as 3m below

this is due to permanent heat flux between the atmosphere and ground

Question 9

what is the average temperature of the ground?

Answer 9

12C, except in dense urban areas

Question 10

Explain simply, how does a shallow ground heat source work with the changing of seasons?

Answer 10

Summer: cooling system puts heat of house into heat storage

Winter: Stored heat can be accessed for heating the home

Question 11

In a ground heat exchanger what does compression achieve?

Answer 11

increase temperature and pressure

Question 12

What are the two types of ground heat exchange systems?

Answer 12

closed loops

open loops

Question 13

what is an example of a closed loop ground heat exchange?

Answer 13

vertical - borehole heat exchangers
horizontal - (looks like underfloor heating)

Question 14

What is an example of an open loop ground heat exchange?

Answer 14

thermo-active structures (geotechnical structures with heat exchangers installed)

Question 15

How do vertical borehole heat exchangers compare to a horizontal heat exchange system?

Answer 15

The horizontal system is much more uncertain due to its susceptibility to be affected by the environment. It is also usually installed at shallow depth where temperature is not reliably constant.

Question 16

What is the difference between an open loop and closed loop heat exchange system?

Answer 16

An open loop utilises ground water, some of which is returned to the environment whilst the rest is used in the system.

A closed loop recycles water and heat and does not let any of it out into the environment.

Question 17

Describe the flow of water in an open loop ground source heat exchanger

Answer 17

reversed groundwater flow is directed into a well, connected to a heat pump

waterflows through heat pump, and returns to the ground

The water is partly reversed back to the well and partly carried away into the environment via natural convection.

As this happens, the new thermal energy of the water is carried back into the system and dispersed into the environment with the flow of water.

Question 18

Cooling down the London underground is what kind of geothermal system?

Answer 18

open loop (interacts with the environment)