Everything else - mashed in together

Question 1

List two abundant sources of geothermal energy.

Answer 1

Volcanoes and geysers.

Question 2

Summarise how heat pumps work.

Answer 2

• 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.

Question 3

Explain how a ground source heat pump works.

Answer 3

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.

Question 4

List some of the potential problems associated with heat pumps.

Answer 4

• 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

Question 5

Discuss advantages and disadvantages of introducing microgeneration into the electricity network and discuss whether continued growth is sustainable.

Answer 5

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.

Question 6

List the three main types of energy storage and list a few examples of each.

Answer 6

The three types are: bulk, distributed and fast.

Bulk: Pumped-hydro, flow batteries, flywheels
Distributed: Electro-chemical batteries, capacitors
Fast: ??

Question 7

What are typical energy storage requirements?

Answer 7

1. Readiness for deployment at scale
2. Speed of charge/discharge
3. Storage capacity
4. Ability to schedule
5. Life expectancy and reliability
6. Unit capital cost
7. Environmental impact
8. Round-trip energy efficiency
9. Ease of installation (size/weight)

Question 8

State three categories of biofuel and give an example of each one.

Answer 8

Solid - wood
Liquid - Methanol
Gas - Methane