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Physics: Energy, Climate, and Sustainability - Carbon-Neutral Technologies, Hydrogen Fuel, and Future Energy Systems

Grade 8IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Carbon Neutrality: This refers to achieving a balance between emitting carbon and absorbing carbon from the atmosphere. It involves using technologies that do not add to the net amount of greenhouse gases, such as CO2CO_{2}.

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Renewable Energy Systems: Transitioning from fossil fuels to sources like solar, wind, and hydroelectric power. These systems are sustainable because they rely on resources that replenish naturally at a rate higher than or equal to consumption.

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Green Hydrogen: Hydrogen produced through the electrolysis of water using renewable electricity. The chemical reaction is represented as 2H2O(l)→2H2(g)+O2(g)2H_{2}O(l) \rightarrow 2H_{2}(g) + O_{2}(g). It is considered a clean fuel because its only byproduct during combustion or use in a fuel cell is water.

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Hydrogen Fuel Cells: Devices that convert the chemical energy of hydrogen directly into electrical energy through an electrochemical reaction: 2H2+O2→2H2O+Electrical Energy2H_{2} + O_{2} \rightarrow 2H_{2}O + \text{Electrical Energy}.

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Carbon Capture and Storage (CCS): A technology designed to prevent large amounts of CO2CO_{2} from being released into the atmosphere from fossil fuel power plants by capturing the gas and storing it underground.

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Energy Efficiency: A measure of how much input energy is converted into useful output energy. In future energy systems, maximizing efficiency reduces the total energy demand: Efficiency=EusefulEtotal×100%\text{Efficiency} = \frac{E_{useful}}{E_{total}} \times 100\% .

📐Formulae

Efficiency=(Useful Energy OutputTotal Energy Input)×100%\text{Efficiency} = \left( \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} \right) \times 100\%

E=P×tE = P \times t

2H2O→electrolysis2H2+O22H_{2}O \xrightarrow{\text{electrolysis}} 2H_{2} + O_{2}

P=V×IP = V \times I

💡Examples

Problem 1:

A sustainable housing complex uses a solar-powered electrolyzer to produce hydrogen. If the electrolyzer consumes 20000 J20000\text{ J} of electrical energy to produce hydrogen that contains 14000 J14000\text{ J} of chemical energy, calculate the efficiency of the hydrogen production.

Solution:

Efficiency=1400020000×100%=70%\text{Efficiency} = \frac{14000}{20000} \times 100\% = 70\%

Explanation:

To find the efficiency, we divide the useful energy stored in the hydrogen (14000 J14000\text{ J}) by the total electrical energy input (20000 J20000\text{ J}) and multiply by 100100 to get a percentage.

Problem 2:

A hydrogen fuel cell car motor operates at 60 kW60\text{ kW} of power for 120 seconds120\text{ seconds}. Calculate the total energy used by the motor in Joules.

Solution:

E=P×t=60000×120=7200000 JE = P \times t = 60000 \times 120 = 7200000\text{ J}

Explanation:

First, convert power from kilowatts to Watts (60 kW=60000 W60\text{ kW} = 60000\text{ W}). Then multiply the power by the time in seconds (120 s120\text{ s}) to find the total energy consumption: 7.2×106 J7.2 \times 10^{6}\text{ J}.

Problem 3:

Determine the net carbon emission if a factory emits 80000000 kg80000000\text{ kg} of CO2CO_{2} but utilizes carbon-neutral technologies and forest offsets to capture 34567892 kg34567892\text{ kg} of CO2CO_{2}.

Solution:

80000000−3456789245432108\begin{array}{r} 80000000 \\ -34567892 \\ \hline 45432108 \end{array}

Explanation:

The net carbon emission is the difference between the total emissions and the amount captured or offset. The result is 45432108 kg45432108\text{ kg} of CO2CO_{2}.