topic 6 (microgeneration)

Question 1

Define the term microgeneration.

Answer 1

Small scale generation of heat and power.

Question 2

Identify two micro-electricity technologies.

Answer 2

Solar PV.
Wind

Question 3

d two micro heat technologies.

Answer 3

Biomass [1], Solar thermal [1], Ground source heat pump [1]

Question 4

Identify two of the main benefits of home or community
microgeneration of electricity.

Answer 4

Reduced energy costs.
* Contribution to environmental targets.
* Enhanced security of supply.
* Financial incentives.

Question 5

Identify two economic benefits and two environmental benefits for the school if
they choose to install a ground source heat pump.

Answer 5

Economic Benefits: Any two from:
* Lower heating bills for the school [1]
* Benefit from government incentives, e.g. Renewable Heat Incentive [1]
* Government may provide a grant to cover some or all of the cost of the
ground source heat pump [1]
Environmental Benefits: Any two from:
* Does not burn fossil fuels as a fuel source, therefore doesn’t produce
carbon dioxide on site [1]
* Deliveries of heating fuel are no longer necessary [1]
* Does not require any fuel to be mined from the earth, therefore has a
less detrimental effect on the environment [1]

Question 6

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.

Answer 6

Heat energy is absorbed from the ground in a collector loop.
In the evaporator this heat causes a refrigerant to become gaseous.
{1}
{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.

Question 7

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.

Answer 7

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.
Transferring its heat to the heating circuit of the house.

Question 8

Explain the role of the following parts of a ground source heat pump:
* Evaporator
{1}
{1}
{2}
55 | P a g e
Environmental Technology – AS Past Papers Overview 2019;
* Compressor
* Condenser
* Expansion value

Answer 8

Evaporator – In the evaporator heat is transferred from the ground loop into the
refrigerant. [1] The refrigerant boils and evaporates (even at a low temperature)
thus storing the generated energy in its gaseous form. [1]
Compressor – The gas from the evaporator is compressed to increase its
pressure. [1] This increases the temperature of the refrigerant. [1]
Condenser – The condenser acts as a heat exchanger where heat is
transferred to the heating system of the house. [1] This cools the refrigerant
again. [1]
Expansion Valve – The refrigerant passes through the expansion valve
reducing its pressure and temperature. [1] The refrigerant returns to the
evaporator where the process begins again. [1]

Question 9

Explain what is
meant by a Coefficient of Performance.

Answer 9

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).

Question 10

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

Answer 10

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

Question 11

– Identify the common types of closed-loop ground source heat pump
systems available for domestic homes including:

Answer 11

vertical;
− horizontal; and
− pond.;