Chapter 5 Multiple Choice Questions

1) In what period of time does the Earth receive as much energy from the Sun as is consumed globally in one year?

~1 second

~1 minute

~1 hour

~1 day

2) The percentage of the world's energy consumption in buildings from space heating or cooling and heating water is approximately…

10%.

20%.

30%.

40%.

3) Which is the more efficient solar thermal collector?

Evacuated tube collector

Flat plate collector

4) Selective emitters are used in solar thermal applications to ______.
Please select all that apply.

absorb a high fraction of the incident solar radiation and significantly decrease the amount of radiation emitted

eliminate the radiation emitted by an absorber

increase the temperature of the absorber to improve the thermal efficiency

5) The radiative power absorbed by a receiver at a temperature T is that concentrated on to it, less the amount _____ ______ which depends on T⁴.

6) An air-source heat pump powered by electricity with a carbon intensity of 0.4 kg CO₂ per kWh is available as an alternative to gas heating. Which one of the following would be more efficient?

A pump with a COP of 1.5

A pump with a COP of 3

A pump with a COP of 0.7

7) Which is the correct expression for the coefficient of performance of an ideal heat pump, where the internal temperature is T₂ and the external one is T₁?

T₁/|T₁ − T₂|

T₂/T₁

T₂/|T₁ − T₂|

1 − T₂/(T₁ − T₂)

8) GSHP stands for _____ _____ _____ .

9) What statements about concentrated solar thermal power (CSP) are true? Please select all that apply.

Clear days with high solar intensities are often found within 15° of the equator.

Parabolic trough reflectors are usually aligned with their axes E-W.

Solar radiation is concentrated to provide higher input temperatures.

CSP power plants can generate electricity at night-time.

The LCOE is dominated by the capital cost of the plant.

10) Which of the following statements about concentrated solar power (CSP) are correct? Please select all that apply.

The output from a solar chimney is proportional to its height.

CSP technology does not depend on any rare element.

Thermal energy storage (TES) currently costs less than battery storage or pumped storage.

The output in ocean thermal conversion plants depends on the cube of the temperature difference between the surface and water below 1000 m.

CSP can be very dispatchable.

11) Match the conversion efficiencies to the technologies.

11a.

~3.5%

11b.

~10%

11c.

~2%

11d.

~20%

12) The dependence of the volume flow rate Q through a porous rock of cross-sectional area A and thickness L on the pressure drop Δp and viscosity of the water μ is of the form…

Q ∝ AΔpμ⁻¹L⁻².

Q ∝ AΔpμ⁻¹L⁻¹.

Q ∝ A²Δpμ⁻²L⁻².

13) Where would you expect to find geothermal power plants?
Please select all that apply.

UK

Iceland

New Zealand

Egypt

South Africa

Italy

14) What is the thermal energy stored in 2 km³ of granite at a temperature of 250 °C? The density and specific heat of granite are 2700 kg m⁻³ and 790 J kg⁻¹ °C⁻¹, respectively.

~1 GJ

~1 TJ

~1 EJ

15) What statements apply to enhanced geothermal systems?
Please select all that apply.

The challenge is in making a network of fractures with a large surface area that also allows a high flow rate.

The thermal power output is proportional to ΔT ², where ΔT is the temperature rise of the injected water.

Typical depths are around 5 km underground.

Typical hot rock temperatures at 5 km depth are 500 °C.

The main expense is in drilling to the depths required.

Interference from natural fissures is not important.

16) Heat diffuses a distance of ~ (kt)^1/2 in a time t, where k is the thermal diffusivity of rock ~ 10^-6 m² s^-1. Over what distance will heat diffuse in 4 years?

~1 m

~11 m

~126 m

17) The global geothermal power resource is estimated to be…

~300 EJ y⁻¹.

~3000 EJ y⁻¹.

~30000 EJ y⁻¹.

18) Match the accessible potential by 2050 to the technologies.

18a.

3000 TWh y^-1

18b.

4000 TWh y^-1

18c.

2000 TWh y^-1

18d.

1800 TWh y^-1

Quiz Content