Chapter 6 Flashcards
What is the definition of Microgeneration?
The small-scale generation of heat and power
What is the definition of microelectricity technology?
Small devices that are capable of producing electricity.
What is microheat technology?
Small devices that are capable of producing heat
List 2 microelectricity technologies
1- solar pv
2- wind
List 3 microheat technologies
1- solar thermal
2- ground source heat pump
3- biomass
Identify 4 main benefits of home/ community microgenerations.
1- Reduced energy costs
2- contributions to environmental targets
3- enhanced security of supply
4- Financial incentive
Explain the role of the evaporator in a heat pump
The evaporator takes in a liquid, called the refrigerant, at colder temperature than the air outside. It absorbs thermal energy from the air and transfers into a gas.
Explain the role of a compressor in a heat pump
The refrigerant, in gaseous form, is pumped to the compressor. Here the gas is compressed, increasing the pressure and critically the temperature of the gas.
Explain the role of an expansion valve in a heat pump
The expansion valve allows the gaseous part of the refrigerant to expand, reducing its temperature and condensing fully into a liquid but now at lower temperature than the evaporator end of the system.
Explain the role of the condenser in a heat pump
The condenser now transfers this thermal energy to the water being circulated through the heat exchanger. The water from the hot water tank is circulated from the tank to the heat exchanger and then back to the top of the tank at high temperature. The refrigerant in the condenser loses thermal energy and starts to condense back into a liquid. It is now a mixture of gas and liquid at high temperature.
Name 2 advantages of an air source heat pump
1- Can be easily installed in existing buildings as well as new building.
2- Does not require a large area of ground around the building
2 disadvantage of air source heat pumps
1- Air temperatures varies a lot more than ground temperatures and the low temperature in the air does not carry as much thermal energy.
2- The pump makes a humming noise.
What liquid circles in a loop in a ground source heat pump and how deep is this loop.
Refrigerant circulates to extract thermal energy from the ground and the loop is usually 0.5M deep.
What degree of temperature does the ground change throughout the year?
6° and 12°
2 advantages of a ground source heat pump.
1- The ground at 0.5 m depth or below maintains a more consistent higher range of temperatures, compared to an air source heat pump, which results in a higher COP.
2- Repayment periods are smaller