Chapter 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}
and Wind {1}
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: Biomass [1], Solar thermal [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.
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 [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]
Discuss three different benefits of community microgeneration with reference to a ground source heat pump. (6)
• 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. [1]
• Enhanced security of supply. [1] Not dependent on fluctuating prices of fossil fuels. [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}
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}
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.
