3 Technical Concepts and Overview

Question 1

When is an object said to have done work?

Answer 1

When it has been displaced against physical resistance

Question 2

What it the formula to find work in terms of integrals?

Answer 2

W = ∫ F*dl

Question 3

What is a Joule?

Answer 3

Work done moving 1 meter against a force of 1 newton

Question 4

What is energy?

Answer 4

Capacity to perform work

Question 5

What are the 3 forms of energy?

Answer 5

• Kinetic
• Potential
• Chemical

Question 6

What is power?

Answer 6

Power is the rate of doing work

Question 7

What is a Watt defined as?

Answer 7

Watt, defined as 1 Joule per second

Question 8

What two quantities does ohms low relate?

Answer 8

Ohms law relates the voltage difference and the electrical current flowing through the resistance

Question 9

How does heating a wire affect the current?

Answer 9

Heating in wire increases with the square of the current

Question 10

Whats the maximum solar power at the Earths surface?

Answer 10

1𝑘𝑊/𝑚^2

Question 11

Whats the rating of an open cycle gas turbine?

Answer 11

300 𝑀𝑊

Question 12

How much is 1 barrel of oil equivalent?

Answer 12

6GJ

Question 13

How much is 1 cubic meter of gas?

Answer 13

40 MJ

Question 14

What is the fossil fuel equivalent conversion?

Answer 14

• Is approximate and depends on the reference fuel
• Depends on where the fossil fuel equivalent has come from

Question 15

Which laws of thermodynamics need to applied?

Answer 15

1. The First Law of Thermodynamics
2. The Second Law of Thermodynamics

Question 16

What is the first law of thermodynamics?

Answer 16

Energy is neither created nor destroyed but converted from one from to another

Question 17

How is energy in a frictionless environment?

Answer 17

𝑄 = 𝑞 + 𝑊𝑜𝑟𝑘

Question 18

What is the second law of thermodynamics?

Answer 18

A device operating continuously cannot export only work from an isolated source of heat

Question 19

What is a device doing work paired with?

Answer 19

Energy from a higher temperature

Question 20

What are energy flows associated with in society?

Answer 20

• Static engines
• Chemical process plant
• Keeping warm and cool
• Transport of people and goods

Question 21

What is an example or the second law of thermodynamics?

Answer 21

Heat engine that extracts mechanical work from a heat source

Question 22

What does the 2nd law state in terms of q?

Answer 22

q ≠ 0

Question 23

What happens as energy flows through a process?

Answer 23

Grade deteriorates

Question 24

What is the theoretical maximum extractable work called?

Answer 24

Exergy

Question 25

What is a heat source exergy like and what does it depend on?

Answer 25

<100% - Hot source temperature - ambient temperature

Question 26

What happens if heat source tends to infinity?

Answer 26

The source tends to pure exergy and is said to be very high grade

Question 27

What happens if heat source is close to ambient?

Answer 27

There is little content left and the heat source is very low grade

Question 28

How do you calculate efficiency?

Answer 28

𝜂 = Output/input

Question 29

What is first law efficiency?

Answer 29

Uses energy arriving at the process ignoring grade or upstream energy system losses

Question 30

What is primary energy efficiency?

Answer 30

Replaces the delivered energy* input by the primary energy* required to produce it

Question 31

What is exergy efficiency?

Answer 31

Compares the actual consumption against that required by a thermodynamically ideal process

Question 32

How do you calculate exergy efficiency?

Answer 32

𝜂 = required exergy/total exergy input

Question 33

What is an energy system?

Answer 33

Accepts one or more energy flows and transforms them to produce one or more energy flows of different grade

Question 34

Where is there a large amount of exergy lost in a conventional power station?

Answer 34

Between the combustion flame and the steam entering the turbine

Question 35

What a Combined Cycle Power Plant?

Answer 35

Use a gas turbine to take exergy from the gas flame and pass the cooled down gases (if 500C is cool!) to a steam plant driving a steam turbine.

Question 36

What is an ideal heat engine called?

Answer 36

Carnot Engine

Question 37

What two energy systems are exergetically more efficient?

Answer 37

* Heat Pump * Combined Heat and Power

Question 38

How does heat pump work?

Answer 38

Energy is taken from a cool (low grade source) and power is supplied (100% exergy) to raise its grade to discharge as heat at a higher temperature

Question 39

How does the Carnot engine work?

Answer 39

Takes energy at a rate 𝑄̇ from a heat source at 𝑇_h and discharges waste heat at a rate 𝑞̇ to a heat sink at 𝑇_c. while producing power 𝑊̇ , without loss of exergy in the process

Question 40

What does a refrigerator do in a heat pump system?

Answer 40

Extracts energy from a cold volume and discharges it at above kitchen temp at the back of the fridge.

Question 41

what is the function of an air conditioning mit?

Answer 41

Removes heat from a room and discharges at a higher temp in a “condenser” usually located on the roof

Question 42

How is power supplied in refrigerant circuit?

Answer 42

Compressor

Question 43

How does an air-to-air heat pump work?

Answer 43

Takes heat from ambient and ups its grade by adding exergy of its shaft power to the flow of energy into building

Question 44

How much work supplied to heat pump?

Answer 44

13% of the heat requirement

Question 45

What is the temp of the heat flow of an air-to-air heat pump?

Answer 45

30 - 40˚C

Question 46

What is the equation for COP?

Answer 46

𝑄̇ = 3 − 4 𝑊̇

Question 47

How can performance of a2a improve?

Answer 47

Geothermal heat source rather than air

Question 48

Why is condensing at 35˚C in a steam turbine not good?

Answer 48

Too low for use in central heating, and therefore it is genuinely waste heat

Question 49

What is CHP?

Answer 49

Use of a heat engine or power station to generate electricity and useful heat

Question 50

What is raw fuel entering the economy termed as?

Answer 50

Primary energy

Question 51

What are the examples of secondary energy?

Answer 51

- Refined oil - Town gas - Electrical power

Question 52

What is useful energy?

Answer 52

Energy may need to be converted on site to provide the final service

Question 53

Why must energy supply match demand approximately?

Answer 53

To ensure stability of the energy grid and constant supply, despite the variability in consumption

Question 54

How is electricity stored in the UK, and what is its significance?

Answer 54

Limited to short durations, typically 1-2 minutes using batteries with around 1GW capacity

Question 55

What are the challenges in electricity supply and demand matching in the UK?

Answer 55

- complex real-time system operations - spatially-distributed and time-varying demand - need for a variety of generators

Question 56

What mechanisms are used in the UK to ensure electricity supply meets demand?

Answer 56

regulated electricity market

Question 57

What happens if sufficient capacity is not provided in markets like housing and transport?

Answer 57

- Housing price goes up - Impacts on time and GDP in the transport market

Question 58

How is the electricity market different from other markets when capacity is insufficient?

Answer 58

Insufficient capacity can lead to system failure

Question 59

What does the "day ahead market" in the electricity sector signify?

Answer 59

The day ahead market represents the wholesale price of electricity for the next day, reflecting anticipated demand and available supply.

Question 60

Why's is capacity not always utilised?

Answer 60

- Variability in renewable energy sources (like wind and solar) - Market demands - Maintenance cycles - System efficiency

Question 61

What is the capacity factor?

Answer 61

Ratio of average generation rate to installed capacity

Question 62

What is the LCoE?

Answer 62

Lowest price that consumers need to pay for the electricity generated to break even at the end of the project lifetime

Question 63

How do you calculate LCoE?

Answer 63

(OPEX + CAPEX)/E

Question 64

What is the learning rate?

Answer 64

Characteristic parameter that defines the cost reduction [%] for each doubling of cumulative capacity.

Question 65

What cost reductions due to?

Answer 65

Mainly due to **technology innovation** and to a **reduction in perceived risk**.