Geothermal energy Flashcards
What is the basics of high temperature geothermal energy?
water flows into an area closer to a heat source, increasing its temperature
water is injected as a vapour into a turbine generating electricity
What is the problem with high temperature geothermal energy?
requires a very specific set of circumstances
What geothermal energy systems can be widely used and installed?
low temperature geothermal resources can be used for heating (not for electricity though)
What do we need for geothermal energy?
Anomalies in the ground, where soil acts as a heat sink in the summer, and a heat source in the winter.
In shallow ground this can be done by the sun
WHat does a shallow ground source heat resource consist of?
heat exchanger, heat storage, some pipes to connect it to a house
This creates a heat flux between the ground and the target
How does geothermal energy exhange heat?
through a heat pump involving an evaporator, compressor and condenser, as well as an expansion valve
What is a closed loop heat exchanger?
both horizontal and verticle, no flow in and out of the pipes, just around
Vertical go up and down
horizontal forms a pattern of parallel horizontal tubes or a ‘slinky’
What is an open loop?
Where water is transferred between 2 pipes at other sides of a thermal storage mass
Convection is essential
Water must be used, therefore heat extraction would be limited
What are thermo-active strucutres?
structures with geothermal technolog built in, i.e. pipes in foundations etc.
How are geothermal technologies integrated on the london tube?
warmed water is puped down into the ground, and along tubes to where the heat exchange is taking place
Cool water is pumped back up, water is refiltered and pumped back through
What are some problems with thermo-active tunnels such as the london tube?
there is large amounts of energy loss in the exposed pipes
What are some infrastructure applications for geothermal technologies?
road de-icing, the road has pipes running through it, each of them with warm water when its cold (can be extracted from the ground)
Geothermal city - places that need to be cold/ hot pump their lost heat, gained heat to each other to be used
What are the properties needed to ensure succesful heat transfer in geothermal systems?
- specific heat capacity
- thermal conductivity
- permability
How do we measure thermal and hydraulic conductivity in a lab?
with a thermal & hydraulic conductivity cell
How do we measure thermal and hydraulic conductivity in the field?
with needle probes or a thermal response test
