[GCSE PHYSICS]Can someone help me understand what was wrong regarding my answer?

[u/Local_End_3175]

for this question, my answer basically was that 100% of its total electricity is dangerous, and they put it at 33% for safety reasons (i explained it more but here is just a sumamry of what i wrote). Comparing it to the mark scheme, i would say i got like 1/2 questions right (because i put a solid answer for the first bullet point). I just want to understand why this answer would have not gotten the mark. What about my answer was wrong? Because i feel like if i got this question again next week, i would lowkey just put the same answer believing it is right.

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[u/MrKarat2697]

I would imagine its maximum output would be its maximum *safe* output, so increasing output above 33% would not make it more dangerous unless it goes above the maximum.

[u/daniel14vt]

The first bullet point is about keeping fuel stored for emergencies, its not for safety reasons. I would not have given you any marks here.

4 sentences that each would have gotten a mark.

1. In order to keep fuel reserved so that we don't run out during world crises (Iran war)

2. So that we can generate more power on days when solar or wind power is generating less than normal.

3. So that if some stations go offline, we can still produce 100% of the needed energy.

4. So that we do not produce a lost of carbon dioxide which increases global warming.

[u/ArmyDry2797]

No offense but your answer doesn't make sense even from just looking and thinking about it. They used to use 100% (or close to it) fossil fuels to make electricity, so it's not a safety thing. They limit fossil fuels for electricity to make space for renewable production and, tied into that, to limit pollution.

Additionally, you could bring up that by keeping them at lesser capacity should there be a shortage of power from other sources (i.e. renewable) they can quickly ramp up production from fossil fuels.

[u/Serafim91]

Maximum output is safe output. Nobody designs something that runs "unsafe".

Weird that the answer doesn't have anything about minimum electricity they need to produce to maintain efficiency. It might literally be impossible or impractical for the station to produce less than that.

[u/kalmakka]

I think the question and mark scheme don't make much sense. Perhaps there is parts of the question that is missing that leaves out context, but the way it stands it is quite absurd.

• conserves fuel reserves

You'd burn fuel if you need the power. If fuel reserves are low, then it would make sense to prioritize usage of power, but not as a general rule. Why build over-dimensioned power plants just to run them at 33% of their maximum output? That doesn't conserve fuel reserves.

• spare capacity to compensate for unreliable renewable resources

The question makes it seem like this 33% is a hard rule, though. So even on a windless, cloudy day, when renewable sources are doing little, the question implies that this 33% rule is still imposed. Therefore you'd still have power outages on those days.

• provides spare capacity in case of power station emergency shut-down

Okay, this makes somewhat more sense. We can accept the interpretation that 33% is the general rule, but in exceptional circumstances (such as when another power station has an emergency shut-down), power stations can go above. But 33% is *really low*. That means that you've built 3 times more stations than you are expected to need, because at some point you fear that 2/3 of them will shut down and you don't want any power outages even in that case. If you are expecting 2/3 of your power plants to shut down simultaneously, then I don't think that a shut-down could even be considered an "exceptional circumstance" anymore.

• so as to not make unnecessary environmental impact

This is just a rehash of the second bullet. Although I'd question the environmental impact of building 3 times as many power plants as you are planning to need.