EigoPro 準1級 読解 — Storing Renewable Energy

Solar panels and wind turbines have grown astonishingly cheap, and in many regions they now generate electricity more cheaply than coal or gas. Yet a stubborn obstacle stands between this abundance and a fully decarbonised grid: the sun sets and the wind drops, often precisely when demand peaks. A power system that runs on renewables must therefore store vast quantities of energy when generation is plentiful and release it on demand. Storage, not generation, has become the defining engineering challenge of the energy transition. The default solution today is the lithium-ion battery, the same chemistry that powers laptops and electric cars. Such batteries respond to fluctuations in milliseconds and have plummeted in price, but they are ill-suited to the task of carrying a city through a windless week. Storing energy for days rather than hours would require batteries on a scale that is prohibitively expensive, and the lithium and cobalt they depend on are neither limitless nor cleanly mined. For short bursts they are unrivalled; for long droughts of supply they falter. This is why engineers are reviving older and stranger ideas. Pumped hydro—using surplus electricity to push water uphill, then letting it fall through turbines when needed—already accounts for most of the world's storage capacity, though suitable sites are scarce. Newer schemes propose hoisting massive concrete blocks, compressing air in underground caverns, or storing heat in molten salt or even crushed rock. None is a panacea; each trades efficiency, cost, or geography against the others. The deeper lesson is that no single technology will suffice. A resilient grid will likely weave together a portfolio of storage methods, each matched to a particular timescale, alongside smarter pricing that nudges consumers to shift their demand. Politicians who promise that cheap renewables alone will deliver clean power are telling only half the story; the harder, less glamorous half is learning how to keep the lights on after the sun goes down.

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この単元の問題を3問、解説つきで公開しています

準1級 · 読解 · 全5問

問 1

What is the main idea of the passage?

  • Storing renewable energy, rather than generating it, is now the central challenge in moving to clean power.
  • Pumped hydro should replace all other forms of energy storage worldwide.
  • Lithium-ion batteries have already solved the problem of powering cities entirely on renewables.
  • Renewable energy will never be cheap enough to replace coal and gas.
Phrase

Storage, not generation, has become the defining engineering challenge of the energy transition.

準1級読解技術論説主旨把握
⚡ひとことで

本文の論旨は「再エネは安くなったが、課題は発電ではなく『貯蔵』だ」。

選択肢の解説Choice Analysis

「Storing renewable energy, rather than generating it, is now the central challenge in moving to clean power.」

正解

第1段の結論文 Storage, not generation, has become the defining engineering challenge of the energy transition がそのまま主旨。本文は (1) 再エネは安いが供給が断続的→ (2) だから貯蔵が必要→ (3) 電池の限界→ (4) 多様な貯蔵法の組合せが要る、という流れで一貫して『貯蔵こそが鍵』を論じる。よって『発電ではなく貯蔵がクリーン電力移行の中心課題』が正解。

  • 「Lithium-ion batteries have already solved the problem of powering cities entirely on renewables.」

    = リチウム電池が都市の再エネ給電をすでに解決済 ━ 第2段は電池が『数日規模の貯蔵には不向き (ill-suited)』と明言しており『解決済』とは正反対。

  • 「Renewable energy will never be cheap enough to replace coal and gas.」

    = 再エネは石炭・ガスを代替できるほど安くならない ━ 冒頭で再エネは『石炭やガスより安く発電する』と述べており逆。

  • 「Pumped hydro should replace all other forms of energy storage worldwide.」

    = 揚水発電が他の貯蔵法を全て置き換えるべき ━ 本文は『どれも万能ではない (None is a panacea)』『単一技術では足りない』と述べており極端すぎる。

▦Collocation
パターン意味例
the defining challenge of ~~の決定的な課題the defining challenge of the transition
run on renewables再生可能エネルギーで動くa system that runs on renewables
on demand必要に応じてrelease it on demand
stand between A and BAとBの間に立ちはだかるan obstacle stands between abundance and a clean grid
demand peaks需要がピークに達するwhen demand peaks
❝例文

  • Storage, not generation, is the real bottleneck.

    本当のボトルネックは発電ではなく貯蔵だ。

  • A grid that runs on renewables must store energy.

    再エネで動く電網はエネルギーを蓄えねばならない。

  • The plant releases power on demand.

    その発電所は必要に応じて電力を供給する。

💡Tip · 覚えるコツ

主旨設問は『not A, but B』型の対比文を探すと速い。本文は第1段末でズバリ主張を言い切っている。

問 2

According to the passage, why are lithium-ion batteries poorly suited to long-duration storage?

  • They cannot store any energy beyond a few milliseconds.
  • Storing energy for days would demand batteries at a scale that is too expensive, and their materials are limited and not cleanly mined.
  • They are more expensive than every other storage method for short bursts.
  • They respond to fluctuations too slowly to be useful in a power grid.
Phrase

would require batteries on a scale that is prohibitively expensive, and the lithium and cobalt they depend on are neither limitless nor cleanly mined

準1級読解技術論説詳細把握
⚡ひとことで

数日規模の貯蔵は『法外に高価』で、材料 (リチウム・コバルト) も有限かつ採掘が汚い。

選択肢の解説Choice Analysis

「Storing energy for days would demand batteries at a scale that is too expensive, and their materials are limited and not cleanly mined.」

正解

第2段で『Storing energy for days rather than hours would require batteries on a scale that is prohibitively expensive』と述べ、続けて lithium と cobalt が『neither limitless nor cleanly mined (無限でも、きれいに採掘されてもいない)』とする。これを言い換えた『数日分の貯蔵は高すぎる規模の電池を要し、材料も有限で採掘も汚い』が正解。

  • 「The batteries respond to any fluctuations a great deal too slowly to be of any use within a national power grid.」

    = 変動への反応が遅すぎて電網に使えない ━ 本文は逆に『milliseconds で反応する』と長所として挙げている。

  • 「The batteries themselves are quite unable to store any energy at all for longer than a few milliseconds at a time.」

    = 数ミリ秒を超えてエネルギーを蓄えられない ━ milliseconds は『反応速度』の話で、貯蔵時間ではない。誤読を誘う罠。

  • 「They are a great deal more expensive than every other available storage method for the short bursts of power.」

    = 短時間用途では他の全方式より高い ━ 短いバーストでは『unrivalled (無敵)』と明言しており逆。

▦Collocation
パターン意味例
be ill-suited to ~~に不向きであるill-suited to long storage
prohibitively expensive法外に高価なa scale that is prohibitively expensive
neither A nor BAでもBでもないneither limitless nor cleanly mined
depend on ~~に依存するthe lithium they depend on
for short bursts短時間の用途ではfor short bursts they are unrivalled
❝例文

  • The plan is prohibitively expensive.

    その計画は法外に高くつく。

  • This tool is ill

    suited to heavy work. — この道具は重作業には不向きだ。

  • Cobalt is neither limitless nor cleanly mined.

    コバルトは無限でもなく、きれいに採掘もされない。

💡Tip · 覚えるコツ

detail 設問では本文の長所・短所を取り違えた罠 (milliseconds=長所) が紛れ込む。設問の『long-duration』に対応する段落だけを精読する。

問 3

What does the passage say about pumped hydro storage?

  • It has been abandoned because suitable sites no longer exist.
  • It already provides most of the world's storage capacity, but appropriate locations for it are limited.
  • It is the cheapest and most efficient option in every location.
  • It is a brand-new technology that engineers have only just invented.
Phrase

Pumped hydro ... already accounts for most of the world's storage capacity, though suitable sites are scarce

準1級読解技術論説詳細把握
⚡ひとことで

揚水発電=世界の貯蔵容量の大半を占めるが、適地が少ない。

選択肢の解説Choice Analysis

「It already provides most of the world's storage capacity, but appropriate locations for it are limited.」

正解

第3段で『Pumped hydro ... already accounts for most of the world's storage capacity, though suitable sites are scarce』とある。accounts for most → provides most、suitable sites are scarce → appropriate locations are limited と言い換えた選択肢が正解。

  • 「It is a brand-new technology which the engineers have only just recently managed to invent.」

    = 技術者がつい最近発明した最新技術 ━ 本文は揚水を『older and stranger ideas』を『reviving (復活)』する文脈で挙げており『最新の発明』とは逆。

  • 「It is by far the cheapest and the most efficient option available in every single location.」

    = あらゆる場所で最も安く効率的 ━ 本文は『どの方式も効率・費用・地理を互いに犠牲にする』と述べ、万能ではないとする。

  • 「It has been abandoned altogether because any suitable sites no longer exist anywhere at all.」

    = 適地がもう無いので放棄された ━ 本文は『すでに世界の貯蔵容量の大半を占める』と現役であることを述べており逆。

▦Collocation
パターン意味例
account for ~~を占めるaccounts for most of the capacity
suitable sites are scarce適地が乏しいthough suitable sites are scarce
revive an ideaアイデアを復活させるengineers are reviving older ideas
trade A against BAをBと引き換えにするeach trades cost against geography
storage capacity貯蔵容量the world's storage capacity
❝例文

  • Pumped hydro accounts for most storage today.

    今日の貯蔵の大半は揚水発電が占める。

  • Suitable sites for the dam are scarce.

    そのダムに適した場所は乏しい。

  • Engineers are reviving an old idea.

    技術者たちは古いアイデアを復活させている。

💡Tip · 覚えるコツ

though / but の譲歩節は detail 設問の宝庫。『〇〇だが△△』の両側を選択肢が正しく押さえているか確認する。

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