8.Energy Storage

Question 1

State one problem associated with generating electricity from ocean waves.

Answer 1

Intermittency of wave energy sources.

• Reliability of wave energy sources.

Question 2

Renewable energy sources have the potential to deliver a significant proportion of our energy needs in the future. State one main reason why energy storage facilities are needed in order for us to make optimum use of renewable energy sources such as wind, solar, wave and tidal. {1}

Answer 2

Energy supplies from renewable energy sources (e.g. wind, solar, wave, tidal) tend to be unreliable or intermittent. {1}

Question 3

Identify the type of energy storage facility shown in the figure above and describe how the system operates. {4}

Answer 3

Pumped hydro storage. It utilises renewable energy to pump water up to the high dam / reservoir. {1}
It uses the gravity fed water supply to turn turbines {1} whenever there is a lull in renewable power {1}.

Question 4

The flow diagram shown in the figure below illustrates the stages of a typical Compressed Air Energy Storage (CAES) system. In the space provided, outline the operation of the system making reference to each stage. {5}

Answer 4

Energy from a renewable energy resource can be stored during periods of low energy demand (off peak) {1}.
Air is compressed by an electrically powered compressor {1}
And stored in mass quantity in an underground cavern {1}
For use in meeting periods of higher (peak load) {1}
When there is a demand the compressed air is released to drive a turbine connected to a generator to produce electricity. {1}

Question 5

The figure below shows a schematic diagram of an energy storage facility.
Name the type of energy storage facility shown in the figure above and describe how the system operates.
Type of facility
Description.

Answer 5

Pumped Hydro Energy Storage {1}
Description; During off peak (low demand) times, renewable electricity from the
grid is used to power pumps {1}
Which pump water from a lower reservoir to an upper reservoir {1}.
When demand increases te water from the upper reservoir is released down a pipe under high pressure {1}
This then spins turbines which drive generators to produce electricity {1}.

Question 6

State three factors that would make a potential location both beneficial as well as cost effective for the type of energy storage facility shown below. {3}

Answer 6

Availability of existing lakes / reservoirs. {1}
• Suitable topography – good height difference (‘head’) between lower and
upper reservoirs. {1}
• Proximity to high voltage power transmission network. {1}
• Accessibility for construction, operation and maintenance. {1}
• Lack of environmental concerns / objections. {1}