List two abundant sources of geothermal energy.
Volcanoes and geysers.
Summarise how heat pumps work.
- Heat pumps transfer heat from low-quality heat sources
- Sources can include the ground, water or air (GSHP, hSHP and ASHPs)
- The heat sources is solar energy, not geothermal. However, GSHPs are often called geothermal devices.
Explain how a ground source heat pump works.
Example: Underfloor heating/radiators in the home.
- Trenches dug near the home, usually 1-2 metres deeps and boreholes 15-100m depending on energy needs. The longer the coil the more energy it produces.
- The ground loop absorbs heat from the ground.
- Heat is transferred to a refrigerant by the evaporator, changing it from a liquid to a gas
- The compressor conpresses the gas, causing the temperature to rise
- The condenser then transfers the heat from the hot gas to the central heating system.
List some of the potential problems associated with heat pumps.
- Increased strain on the electricity network with significant take up
- Poor performance if incorrectly installed
- Failure of GSHP installations (over time) if incorrectly sized
- Poor performance of ASHP in low temperatures and humid climates
Discuss advantages and disadvantages of introducing microgeneration into the electricity network and discuss whether continued growth is sustainable.
Advantages:
- Fewer losses and power transmitted over shorter distances
- Reduces CO2 emissions
- Could provide income for homes or schools/communities
Disadvantages:
- Could cause power surges e.g from solar power during the summer days when demand is lowest and supply is highest.
- Non-dispatchable sources are generaly variable and unpredictable
- Technical maintenance costs would have to covered by the landlord/school/community
- Stochastic as placement of e.g small scale wind turbines needs carefully planned and can be disrupted in urban environments
- Requires batteries or other methods of storage to make more dispatchable.
List the three main types of energy storage and list a few examples of each.
The three types are: bulk, distributed and fast.
Bulk: Pumped-hydro, flow batteries, flywheels
Distributed: Electro-chemical batteries, capacitors
Fast: ??
What are typical energy storage requirements?
- Readiness for deployment at scale
- Speed of charge/discharge
- Storage capacity
- Ability to schedule
- Life expectancy and reliability
- Unit capital cost
- Environmental impact
- Round-trip energy efficiency
- Ease of installation (size/weight)
State three categories of biofuel and give an example of each one.
Solid - wood
Liquid - Methanol
Gas - Methane
