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Unit 6 · Energy Resources & Consumption Unit Hub Flashcards Cheat Sheet Essentials Visual Review MC Practice FRQ Practice

AP Environmental Science Unit 6 FRQ Practice

Practice a College Board-style free response question on Energy Resources & Consumption. Write your response, then reveal the model answer to see exactly what earns each point.

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Free Response Question · Unit 6 · Comparing Energy Sources

A coastal town currently generates all of its electricity from a single coal-fired power plant. The town council is considering replacing it with one of two options: a new natural gas plant, or a combination of offshore wind turbines plus battery storage. The table below summarizes key characteristics of each option.

Energy sourceCO2 emissions during operationReliability
Existing coal plantVery highHigh (consistent baseload)
Proposed natural gas plantModerate (lower than coal)High (consistent baseload)
Proposed offshore wind + battery storageNone during operationVariable (depends on wind conditions and storage capacity)
A
Identify one environmental benefit and one potential drawback of replacing the coal plant with the natural gas plant.

✓ Model answer (earns the point)

Benefit: Natural gas combustion releases less CO2 per unit of energy than coal combustion, so switching would reduce the town's greenhouse gas emissions compared to the current coal plant. Drawback: Natural gas is still a nonrenewable fossil fuel, and its extraction (often via fracking) can contaminate groundwater and release methane, a potent greenhouse gas, during extraction and transport.

Why it scores: Identifies one specific benefit (lower CO2 than coal) AND one specific drawback (extraction impacts/methane leakage) with the underlying mechanism for each — not just "gas is better" or "gas is still bad" without specifics.
B
Explain why the offshore wind + battery storage option has variable reliability compared to the coal and natural gas options, and describe one way the town could address this limitation.

✓ Model answer (earns the point)

Wind power is intermittent — turbines only generate electricity when wind speeds are sufficient, unlike coal and natural gas plants that can run continuously regardless of weather. This variability means electricity supply may not always match demand. The town could address this by increasing battery storage capacity to store excess electricity generated during high-wind periods and release it during low-wind periods, smoothing out supply to better match demand.

Why it scores: Names the specific concept (intermittency) with the correct mechanism (dependence on wind conditions) AND proposes a specific, relevant solution (expanded storage) — not just "wind isn't always available" without a proposed fix.
C
Beyond switching energy sources, propose one energy conservation strategy the town could implement to reduce overall electricity demand, and explain why this approach is often considered a cost-effective complement to any of the three options above.

✓ Model answer (earns the point)

The town could implement a program promoting energy-efficient appliances and LED lighting (or building insulation upgrades) among residents and businesses. This approach is cost-effective because reducing electricity demand avoids the cost of generating that electricity in the first place — regardless of which power source is chosen, every unit of energy not used is a unit that doesn't need to be generated, making conservation a "first fuel" that complements any generation strategy.

Why it scores: Proposes a specific, realistic conservation strategy AND explains the underlying reasoning (avoiding generation costs/impact entirely) that makes conservation broadly applicable — not just naming a strategy without the cost-effectiveness explanation.

How to score points on AP Environmental Science FRQs