CH 10: Energy Storage

Question 1

What is the definition of reliable?

Answer 1

Consistently good in quality or performance; able to be trusted.

Question 2

What is the definition of intermittent?

Answer 2

Occurring at irregular intervals; not continuous or steady.

Question 3

What renewable sources of energy can be seen as intermittent?

Answer 3

• Wind
• Solar

Question 4

Why is storage needed for energy?

Answer 4

For energy sources such as wind and solar, the supply and demand for energy might not always match. So energy needs to be stored when the supply exceeds demand so that the energy can be used when demand exceeds supply.

Question 5

How will the capacity to store energy increase the effectiveness of renewable energy systems?

Answer 5

1. Decreasing the reliance on expensive, and sometimes price volatile, fossil fuels.
2. Decreasing fossil fuel usage and so helping mitigate the effects of climate change.
3. Increasing a nation’s or region’s energy security (for further information click here. After clicking on this weblink scroll to the bottom of the page to view the video). Fuel security is a topic discussed at length in chapter two.
4. Offering the possibility of nations or regions exporting excess energy to other nations or regions to derive income.

Question 6

What are the 2 forms of energy storage?

Answer 6

• Compressed Air Energy Storage (CAES)
• Pumped hydro

Question 7

What are the stages of the CAES process?

Answer 7

1. Energy is generated from a renewable source during times of low demand (off-peak) which can be stored for future use.
2. This is achieved by using this energy to operate an electrical compressor which compresses air.
3. This compressed air is transported and stored in large quantities in an underground cavern.
4. This compressed air can then be used during times of high demand (peak load).
5. The compressed air is transported from the underground cavern to a gas turbine. Here natural gas is added, and the gas is heated so that it expands. It now is used to turn a gas turbine which is connected to a generator which produces electricity.

Question 8

What are the stages of the pumped hydro process?

Answer 8

1. When electricity is generated by renewable means during off-peak (low demand) times, this electricity is used to operate electrical pumps.
   2.These pumps transfer water from the lower reservoir to the upper reservoir. This is the pumping phase. This water at the higher level has much more energy in the form of gravitational potential energy, as the water is now at a greater height.
   3.When demand increases the water from the upper reservoir is released, travelling down a pipe at high pressure to the lower reservoir.
2. This moving water then spins a turbine which drive generators to produce electricity. This is the generating phase.

Question 9

What are the key requirements for the installation of a CAES system?

Answer 9

1. The availability of an existing cavern underground. Constructing one would make such a project much too expensive and therefore make the project unfeasible.
2. The proximity of the cavern to a high voltage power transmission network. As the distance increases, it will cost much more money to connect to the National Grid.
3. Availability of natural gas supply. The natural gas supply is required to run the gas turbine power plant.
4. The cavern’s location needs to be accessible for construction, operation and maintenance of the plant.
5. The proposed plant will have to gain planning permission and so there should be no environmental concerns or other objections which would cause refusal of planning permission.

Question 10

What are the key requirements for the installation of a pumped hydro system?

Answer 10

1.The availability of existing lakes and reservoirs. These are naturally occurring and would prove too expensive to construct and so make the project unfeasible.
2.Suitable topography through an adequate height difference (‘head’) between the lower and upper reservoir.
3.The proximity of the site to a high voltage power transmission network. As the distance increases, it will cost much more money to connect to the National Grid.
4.The location of the site needs to be accessible for construction, operation and maintenance of the plant.
5.The proposed plant will have to gain planning permission and so there should be no environmental concerns or other objections which would cause refusal of planning permission.