4.Microgeneration

Question 1

Define the term microgeneration.

Answer 1

Small scale generation of heat and power. {1}

Question 2

Microgeneration is defined as the small scale generation of heat and power. Identify two micro-electricity technologies. {2}

Answer 2

Answer:

Solar PV. Wind

Question 3

Identify the two main sources of renewable microgeneration in microelectricity technologies.

Answer 3

Solar PV {1} and Wind {1}

Question 4

Identify two of the main benefits of home community microgeneration of electricity. {2}

Answer 4

Any two from;
• Reduced energy costs.
• Contribution to environmental targets.
• Enhanced security of supply.
• Financial incentives.

Question 5

Explain how heat pump technology raises the heat energy from the ground to a level suitable for domestic heating purposes. You should refer only to the evaporator and compressor. {3}

Answer 5

Heat energy is absorbed from the ground in a collector loop. {1} In the evaporator this heat causes a refrigerant to become gaseous. {1}
The pressure of the gas is raised in the compressor, this causes the temperature to be increased to a level which is useable for domestic purposes.
{1}

Question 6

With reference to the roles played by the evaporator, compressor and condenser, describe how the application of heat pump technology in the figure below extracts low grade heat from the outside air and converts it to high grade heat suitable for domestic heating and hot water. {4}

Answer 6

Heat from the outside air causes the refrigerant to turn into a gas in the evaporator. {1}
This gas is pumped through a compressor which raises its temperature. {1} The gas turns back to a liquid in the heat exchanger / condenser. {1} Transferring its heat to the heating circuit of the house.

Question 7

A domestic heat pump has a Coefficient of Performance of 3.5. Explain what is meant by a Coefficient of Performance. {2}

Answer 7

A coefficient of Performance is a measure of the efficiency of a heat pump. {1}
It is the ratio of the energy output from the pump (energy out) to the amount of energy required to operate the pump (energy in). {1}

Question 8

If the heat pump uses up 3.6 MJ in one hour, what is the heat output in this time? {3}

Answer 8

Coefficient of performance =heat produced by heat pump/ energy consumed by heat pump

3.5=heat produced/3.6MJ

Heat produced=3.5 x 3.6 MJ
=12.6MJ

Question 9

Question; A heat pump has a COP of 2.8. The heat pump produces 16.8 MJ of heat in one hour. State clearly the formula for the COP of a heat pump and calculate the amount of energy it will use in one hour. {5}

Answer 9

Formula
Coefficient of performance = energy output from heat pump/ energy used by heat pump

Calculation

2.8=16.8MJ/energy used

Energy used = 16.8MJ/2.8
=6MJ