1.6 Microgeneration Flashcards
Define the term microgeneration. {1}
Small scale generation of heat and power. {1}
Microgeneration is defined as the small-scale
generation of heat and power. Identify two micro-electricity technologies. {2}
Solar PV. {1}
Wind {1}
Identify the two main sources of renewable
microgeneration in microelectricity technologies. {2}
Solar PV {1} and Wind {1}
Coal, oil and gas are commonly used to produce energy in the forms of
electricity and heat. An alternative method of producing energy is to use
renewables.
Name two micro electricity technologies and two micro heat technologies.
Micro electricity technologies: {2}
Micro heat technologies {2}
Microelectricity: Solar PV {1}, Wind Turbines {1}
Microheat:
Any two from:
Biomass {1}, Solar thermal {1}, Ground source heat pump {1}
Identify two of the main benefits of home or community
microgeneration of electricity. {2}
Any two from;
Reduced energy costs.
Contribution to environmental targets.
Enhanced security of supply.
Financial incentives. {2}
A local school is considering the installation of a ground source heat pump.
Identify two economic benefits and two environmental benefits for the school if
they choose to install a ground source heat pump. {4}
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}
A company which owns six small holiday cottages is upgrading the heating
system by installing a ground source heat pump which could provide heat for
the holiday cottages and a nearby farm house.
Discuss three different benefits of community microgeneration with reference to
a ground source heat pump. {6}
Any three of the following:
Reduces reliance on fossil fuels. {1} Using a ground source heat pump
will provide heating for the house, therefore replacing the need to use fossil
fuels for heating. {1}
Reduces heating bill. {1} The heat from the sun replaces the need to
purchase heating fuel. {1}
Makes a contribution towards environmental targets. {1} Less fossil fuels
are being burned to produce heat, therefore less carbon dioxide emission and
GHG’s. {1}
Enhanced security of supply. {1} Not dependent on fluctuating prices of
fossil fuels. {1}
Complete the diagram by labelling parts A and B. {2}
A = Condenser. {1}
B = Expansion Valve. {1}
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}
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}
The figure below shows an air source heat pump circuit.
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}
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. {1}
Explain the role of the following parts of a ground source heat pump:
Evaporator {2}
Compressor {2}
Condenser {2}
Expansion value {2}
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}
A domestic heat pump has a Coefficient of Performance of 3.5. Explain what is
meant by a Coefficient of Performance. {2}
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}
If the heat pump uses up 3.6 MJ in one hour, what is the heat output in this
time? {3}
Coefficient of Performance (COP) = Heat Produced by Heat Pump % Energy Consumed by Heat Pump {1}
3.5 = Heat Produced % 3.6 MJ {1}
Heat Produced = 3.5 x 3.6 MJ
= 12.6 MJ {1}
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}
Formula
Coefficient of Performance = Energy output from Heat Pump {1} % Energy used by Heat Pump {1}
Calculation
2.8 = 16.8MJ % Energy used {1}
Energy Used = 2.8 % 16.8 MJ {1}
= 6MJ {1}
A householder has installed a ground source heat
pump as a way of extracting useful heat from the ground.
The ground source heat pump has a Coefficient of Performance of 3.1 and uses
up 6.0 MJ of energy in one hour. State clearly the formula for the Coefficient of Performance of the heat pump and calculate the amount of heat energy it will
produce in one hour. {5}
Coefficient of Performance = Energy Output {1} % Energy Used {1}
3.1 = Energy Output % 6.0MJ {1}
Energy Output = 3.1 x 6.0MJ {1} = 18.6MJ {1]
State the formula for the Coefficient of Performance of the heat pump and using
the information in Table 1 calculate the coefficient of performance of the ground
source heat pump.
Coefficient of Performance = Energy Output % Energy Used {1}
Coefficient of Performance = 24 % 4.8 = 5 {3}
The figure below shows two different types of closed-loop
ground source heat pump which are available for domestic use. Complete the
figure by labelling X and Y indicating the type of closed loop ground source heat
pump system each represents. {2}
X; Vertical {1}
Y; Horizontal {1}
Identify the type of ground source heat pump shown in the figure above. {1}
‘Pond’ type ground source heat pump. {1}
The school is located in a busy town and has a limited amount of space.
Discuss what type of ground loop would be best for the school’s ground source
heat pump. {2}
A vertical ground loop is the best option for the school. This is because there is
only enough available space to bore down vertically into the ground. {2}
