Chapter 5 Multiple Choice Questions

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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 correct incorrect

~1 minute correct incorrect

~1 hour correct incorrect

~1 day correct incorrect

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

10%. correct incorrect

20%. correct incorrect

30%. correct incorrect

40%. correct incorrect

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3) Which is the more efficient solar thermal collector?

Evacuated tube collector correct incorrect

Flat plate collector correct incorrect

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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 correct incorrect

eliminate the radiation emitted by an absorber correct incorrect

increase the temperature of the absorber to improve the thermal efficiency correct incorrect

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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.

Your response

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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 correct incorrect

A pump with a COP of 3 correct incorrect

A pump with a COP of 0.7 correct incorrect

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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| correct incorrect

T₂/T₁ correct incorrect

T₂/|T₁ − T₂| correct incorrect

1 − T₂/(T₁ − T₂) correct incorrect

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8) GSHP stands for _____ _____ _____ .

Your response

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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. correct incorrect

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

Solar radiation is concentrated to provide higher input temperatures. correct incorrect

CSP power plants can generate electricity at night-time. correct incorrect

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

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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. correct incorrect

CSP technology does not depend on any rare element. correct incorrect

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

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

CSP can be very dispatchable. correct incorrect

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11) Match the conversion efficiencies to the technologies.

11a.

~3.5%

Select an answer choice Solar tower plant Thermoelectric generation with ΔT 500 °C Solar chimney Ocean thermal energy conversion (OTEC)

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11b.

~10%

Select an answer choice Ocean thermal energy conversion (OTEC) Thermoelectric generation with ΔT 500 °C Solar tower plant Solar chimney

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11c.

~2%

Select an answer choice Thermoelectric generation with ΔT 500 °C Solar chimney Solar tower plant Ocean thermal energy conversion (OTEC)

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11d.

~20%

Select an answer choice Thermoelectric generation with ΔT 500 °C Ocean thermal energy conversion (OTEC) Solar chimney Solar tower plant

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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. correct incorrect

Q ∝ AΔpμ⁻¹L⁻¹. correct incorrect

Q ∝ A²Δpμ⁻²L⁻². correct incorrect

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

UK correct incorrect

Iceland correct incorrect

New Zealand correct incorrect

Egypt correct incorrect

South Africa correct incorrect

Italy correct incorrect

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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 correct incorrect

~1 TJ correct incorrect

~1 EJ correct incorrect

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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. correct incorrect

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

Typical depths are around 5 km underground. correct incorrect

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

The main expense is in drilling to the depths required. correct incorrect

Interference from natural fissures is not important. correct incorrect

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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 correct incorrect

~11 m correct incorrect

~126 m correct incorrect

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

~300 EJ y⁻¹. correct incorrect

~3000 EJ y⁻¹. correct incorrect

~30000 EJ y⁻¹. correct incorrect

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

18a.

3000 TWh y^-1

Select an answer choice Geothermal Heat pumps Solar thermal Concentrated solar power

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18b.

4000 TWh y^-1

Select an answer choice Concentrated solar power Geothermal Solar thermal Heat pumps

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18c.

2000 TWh y^-1

Select an answer choice Solar thermal Concentrated solar power Heat pumps Geothermal

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18d.

1800 TWh y^-1

Select an answer choice Concentrated solar power Heat pumps Solar thermal Geothermal