Final Review

Question 1

Units of energy

Answer 1

kW, mW

Question 2

Nameplate capacity (kW)

Answer 2

The maximum rated output of a generator, prime mover, or other electric power production equipment under specific conditions designated by the manufacturer.

(Percent of Building Load * Annual Building Load (kWh)) / (8760 * Capacity Factor )

Question 3

kWh (per day/month/year)

Answer 3

kW x #h

Question 4

Sectors impacting climate change

Answer 4

Energy and agriculture

Question 5

Sectors under energy

Answer 5

1. transport
2. heating and cooling
3. electricity

Question 6

Sectors under agriculture

Answer 6

1. food production
2. land use change
3. deforestation

Question 7

Parts of a solar panel

Answer 7

cell
forms module
forms array

Question 8

Energy efficiency of solar PV (2020)

Answer 8

15%-24% of solar energy is converted to electricity

Question 9

Transforming solar radiation energy into electrical energy

Answer 9

Solar array -> inverter DC -> AC, grid
Transforming solar radiation energy into electrical energy

Question 10

Solar economies of scale

Answer 10

Bigger is better
Prefer commercial rather than residential buildings
Prefer old derelict sites to green fields
The sky is the limit

Question 11

Solar collector loop

Answer 11

Hot water, underfloor heating and central heating → boiler → mains for cold water feed → solar thermal twin coil cylinder → pump → flat panel or evacuated tube collector → pump → boiler → hot water

Question 11

Poly-crystalline vs mono-crystalline solar cell

Answer 11

Mono-crystalline is more efficient and more expensive

Question 12

Solar district heating (SDH)

Answer 12

Consist of large fields of solar thermal collectors feeding their produced solar heat into block or DH networks in urban quarters, smaller communities, or large cities

Question 13

Solar collector

Answer 13

Pipes with water heated by the sun, no electricity/moving parts
Should work even on a cloudy day (contrary to photovoltaics)
Low-tech, cheap, materials are widely available

Question 14

Closed loop water

Answer 14

Closed loop, no waste of water
Very little electricity needed
Very cheap to install and run

Question 15

Need hot water but no sun?

Answer 15

Insulated storage tank
Insulated pipes (hot and cold)
Large holes in the ground that is insulated and sometimes has black balls for covers

Question 16

Hot water infrastructure costs

Answer 16

Hot water network is expensive to install but very cheap to run (low maintenance costs)

Question 17

Summary of solar thermal

Answer 17

Bigger is better: economies of scale
Significant surface needed (competes with farm land)
Meets only a portion of the demand
Cheap technology
A number of barriers to overcome

Question 17

Main components of a wind turbine

Answer 17

1. blade
2. rotor
3. brake
4. gearbox
5. nacelle
6. anemometer
7. controller
8. generator
9. yaw drive
10. yaw motor
11. power cable
12. computer system

Question 18

Price of solar

Answer 18

Biggest drop in electricity production cost between 2009 and 2019 – 89% in these 10 years

Question 19

What is the capacity factor?

Answer 19

The ratio of the actual energy produced in a given period, to the hypothetical maximum possible, i.e. running full-time at rated power.

It is geographically relevant

Question 20

Capacity factor formula

Answer 20

Energy output (kWh/year) = nameplate capacity x capacity factor x hours of use per year

Average power generated by wind/peak capacity
ex. 5MW wind turbine, if it produces an average of 2 MW, then its capacity factor is 2/5=40%

Question 21

Trias Energetica

Answer 21

1. Limiting the demand for energy
2. Use as much sustainable energy as possible
3. (When necessary) deploying fossil fuels as efficiently and cleanly as possible, reducing the use of fossil fuels

Question 22

Difference between energy and electricity

Answer 22

Electricity is a specific form of energy that you use to power your home/vehicle.

Question 23

Basic principle of wind turbine

Answer 23

Transforming kinetic energy into mechanical into electrical energy

Question 24

Betz Law

Answer 24

Maximum theoretical energy efficiency of a wind turbine MAX of 59.3% efficiency

Question 25

Pros and cons of bioenergy

Answer 25

Pros -renewable -waste reduction -reliability Cons -expensive -space requirements -some adverse environmental impact

Question 26

Limitations of bioenergy

Answer 26

Storing and processing of biomass requires large amounts of space (which limits the location options). Some fuel sources are seasonal, may compete with food production in specific cases, large footprint

Question 27

Constraints of biomass

Answer 27

-lack of sustainable supply of biomass -biomass production competes with food production -bio-energy may not always be low carbon on a life-cycle basis

Question 28

District heating in Copenhagen

Answer 28

The district heating system is supplied by heat from combined heat and power (CHP) plants and from waste incineration plants in the region. A system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating.

Question 29

Hydrogen formula

Answer 29

2H2 + O2 = Energy +2H20 Hydrogen + oxygen = energy + water

Question 30

Basics of H2

Answer 30

Most common element in the universe Can be produced anywhere you have electricity and water Generates heat OR electricity Produced, stored, transported, used without pollution/CO2 3x energy density of oil Fuel cell can reach 60% efficiency

Question 31

Challenges of H2

Answer 31

Does not exist in nature Requires a lot of energy to separate Needs to be stored at high pressure (700 atm) Needs to be refrigerated (-253ºC) 25% of energy for the same volume of gas, big tanks needed Fuel cells need maintenance (moving parts) Subject to leaks (very small gas) Exposive

Question 32

Green H2

Answer 32

Only sustainable way, produces zero carbon emissions Electrolyzers split water into hydrogen and oxygen (electrolysis) May compete on cost vs blue/brown H2 in 2030

Question 32

Demand side of H2

Answer 32

Industry: 50% efficient, worse than batteries, potential use in industries such as chemical production Heating: space heating out-competed by heat pumps (efficiency and cost) Transport: 20% more expensive than EV, hopefully for planes and ships Potential for large power plant Fertilizer, hydrogenation, methanol, hydrocracking, desulphurization, shipping, off-road vehicles, steel, chemical feedstock, long-term storage, etc.

Question 33

Summary of H2

Answer 33

Large public funding Big expectations: small achievements Can help resilience in a fluctuating wind/solar economy Good when large excess wind power available (unconnected island)