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Environmental Technology > Ch 6: Microgeneration > Flashcards

Ch 6: Microgeneration Flashcards

1
Q

What is the definition of micro generation?

A

The small-scale generation of heat and power.

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2
Q

What is meant by micro electricity technologies?

A

Refers specifically to small devices that are capable of producing electricity.

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3
Q

What are the examples of micro electricity technologies?

A
  1. Solar PV
  2. Wind
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4
Q

What is meant by micro heat technologies?

A

Refers specifically to small devices that are capable of producing heat.

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5
Q

What are the examples of micro heat technologies?

A
  1. Solar thermal
  2. Ground source heat pumps
  3. Biomass
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6
Q

What is the first benefit of home/community micro generation?

A

Reduced energy costs - the amount of energy used from fossil fuels decreases. This will lead to:
1. Less electricity used from NG,
2. Less heating oil used ,
3. Less natural gas used if a gas pipeline is available,
4. Less fuels produced for heating such as logs or turf.

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7
Q

What is the second benefit of home/community micro generation?

A

Contribution to environmental targets - the use of micro generation technologies reduces the use of fossil fuels and so reduces the emissions of greenhouse gases. The use of micro generation systems in a home will aid meeting environmental targets.

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8
Q

What is the third benefit of home/community micro generation?

A

Enhanced security of supply - when a micro generation system is installed in a house, some of the following will apply:
1. Require less electricity from NG,
2. Require less natural gas,
3. Require less heating,
4. Require less miscellaneous fuels such as turf, logs and coal.

These people will use less fossil fuels so they won’t be affected by the price rises.

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9
Q

What is the final benefit of home/community micro generation?

A

Financial incentives - there has been significant financial incentives for the installation of micro generation systems. These make the project more viable from a financial perspective and reduces the repayment period.

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10
Q

How does a heat pump work?

A

A heat pump takes thermal energy from a higher temperature environment and transfers it to a cooler temperature environment in order to heat up this area.

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11
Q

What are some examples of heat pumps?

A
  • Fridge-freezer
  • Air conditioning system (this is the reverse action of a heat pump)
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12
Q

Describe the compression of a gas.

A

When a gas is compressed work is done on the gas. This compression increases the pressure of the gas, and also a force is applied over a certain distance so work is done on the gas. When this work is done, there is more internal energy which then creates greater kinetic energy, increasing the temperature of the gas.

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13
Q

Describe the expansion of a gas.

A

This is the opposite to compression. The compressed gas exerts a force on the moveable plate so it moves. The gas expands as the volume inside the cylinder increases. The pressure of the gas has now reduced. As the compressed gas has exerted a force over a certain distance, the compressed gas has done work so this gas has less internal energy. The kinetic energy will then be reduced so the temperature will decrease.

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14
Q

What are the 4 components in a heat pump system?

A

Evaporator
Compressor
Condenser
Expansion valve

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15
Q

What is the order of the 4 components in a heating system?

A

Evaporator
Compressor
Condenser
Expansion valve

Radiant flows from the evaporator round to expansion valve

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16
Q

How can a heat pump be manipulated to become a cooling system?

A

The evaporator and condenser must switch roles. The compressor and expansion valve will never move. The radiant must also change its direction of flow.

17
Q

What is the refrigerant?

A

The heat transfer fluid.

18
Q

What is the use of the pump?

A

It is used to pump the refrigerant around the system as it changes state.

19
Q

What are the only 2 components is the heat pump system that require electrical energy?

A

Compressor and the pump

20
Q

What are the benefits of a heat pump?

A

A heat pump gives out more energy than that of which is supplied to the heat pump itself.

21
Q

What does each of the parts of the energy flow diagram represent?

A

Qc = energy absorbed from the cold end
W = electrical energy supplied to the heat pump
Qh = energy supplied to the hot end

Qh = Qc + W

22
Q

What happens in an air conditioning system?

A
  1. Energy needs to be absorbed into the refrigerant in the house.
  2. Energy needs to be emitted by the refrigerant outside the house.
  3. The radiator in the house now acts as the evaporator as it absorbs energy from the lower temperature side.
  4. The radiator outside the house now acts as the condenser as it emits energy the the higher temperature side.
23
Q

What is an air source heat pump?

A

This is a heat pump that is located outside a building, it extracts thermal energy from the air and passes this energy through the traditional heat pump system to heat your home. There is a heat exchanger located next to the condenser which transfers the thermal energy from it to the water in the heating system. Costs around £7000.

24
Q

What are the advantages of an air source heat pump?

A
  • Can be easily installed in existing buildings.
  • Lower cost than ground source heat pumps.
  • Does not require a large area of ground around a building.
25
Q

What are the disadvantages of an air source heat pump?

A
  • The heat pump makes a humming noise.
  • The air temperature can vary more than ground. Can vary from 30C to 15C. The lower temperature air contains less thermal energy and this large range limits the COP of these heat pumps.
26
Q

What is a ground source heat pump?

A

A ground source heat pump extracts thermal energy from a refrigerant that circulates in a loop in the ground. At a depth of more than 0.5m, the ground has a consistent temperature between 6C and 12C. This is a small range of consistently higher temperatures which can increase the COP. These systems can cost between £10000 and £18000 as more digging is required.

27
Q

What are the advantages of a ground source heat pump?

A
  • The ground at 0.5m depth or below maintains a more consistent higher range of temperatures, which results in a higher COP.
  • Repayment periods are smaller.
28
Q

What are the disadvantages of a ground source heat pump?

A
  • Larger upfront costs.
  • Large area of ground is required to install the pipework loops in the ground.
29
Q

What is the equation used to work out the energy used in a heat pumps?

A

Qh = Qc + W

Qc = thermal energy entering the system from the cold end in J.
W = the electrical energy supplied to the heat pump in J.
Qh = thermal energy leaving the heat pump system at the hot end in J.

30
Q

What is the benefit of a heat pumps system?

A

The thermal energy absorbed at the cold (Qc) is FREE.

31
Q

How can you maximise the efficiency of a heat pump system?

A
  • The value of Qc must be maximised.
  • The value of W must be minimised.
32
Q

What does COP stand for?

A

Coefficient of Performance for the heat Pump.

33
Q

What is the equation used to work out the COP?

A

COP = Qh/W

COP = Coefficient of Performance for the heat Pump, which has NO UNITS.
Qh = thermal energy leaving the system at the hot end in J.
W = electrical energy supplied to the heat pump in J.

34
Q

What does COP really mean?

A

How many times more energy is taken out of the system than that of what is put in.

35
Q

What is the equation of the power of the heat pump?

A

Pc + W = Ph

Pc = thermal power entering the system from the cold end in W.
W = electrical power supplied to the heat pump in W.
Ph = thermal power leaving the heat pump system at the hot end in W.

36
Q

What is the new equation for COP when using power?

A

COP = Ph/W

COP = Coefficient of Performance for the heat Pump, which has NO UNITS.
Ph = thermal power leaving the system at the hot end in W.
W = electrical power supplied to the heat pump in W.

37
Q

What are the 3 types of ground source heat pumps?

A
  1. Horizontal loop.
  2. Vertical loop.
  3. Pond loop.

Environmental Technology (6 decks)

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