Energy Storage Systems & Batteries

This lesson examines how energy is stored, with a focus on battery technologies and their application in modern products. Energy storage is covered in AQA GCSE Design and Technology (8552), Section 3.1.2, and is increasingly important as renewable energy and portable electronics grow.

---

Why Is Energy Storage Important?

Many renewable energy sources (wind, solar) are intermittent — they produce electricity only when the wind blows or the sun shines. Energy storage systems capture excess energy when supply exceeds demand and release it when demand exceeds supply.

For portable products (smartphones, laptops, electric vehicles), batteries enable operation without a mains connection.

---

Types of Batteries

Primary Cells (Non-Rechargeable)

Primary cells produce electricity from a chemical reaction that is irreversible. Once the chemicals are used up, the battery must be disposed of.

Type	Voltage	Common Uses	Notes
Zinc-carbon	1.5 V	Torches, remote controls, clocks	Cheapest; shortest lifespan
Alkaline	1.5 V	Toys, cameras, portable radios	Longer life than zinc-carbon; most popular disposable battery
Lithium primary	3.0 V	Smoke detectors, medical devices, watches	Very long shelf life (up to 10 years); lightweight
Silver oxide	1.55 V	Watches, hearing aids, calculators	Small button/coin cell format

Secondary Cells (Rechargeable)

Secondary cells use a reversible chemical reaction. When connected to a charger, the chemical reaction is reversed, restoring the battery's charge.

Type	Voltage per Cell	Energy Density	Common Uses	Notes
Nickel-cadmium (NiCd)	1.2 V	Low	Older power tools, emergency lighting	Suffers from "memory effect"; cadmium is toxic
Nickel-metal hydride (NiMH)	1.2 V	Moderate	AA/AAA rechargeable cells, older hybrid cars	Better than NiCd; no toxic cadmium
Lithium-ion (Li-ion)	3.7 V	High	Smartphones, laptops, electric vehicles, drones	Lightweight; no memory effect; dominant technology
Lithium-polymer (LiPo)	3.7 V	High	Thin devices (tablets, smartwatches)	Can be made in very thin, flexible shapes
Lead-acid	2.0 V	Low	Car starter batteries, UPS systems	Heavy; cheap; very reliable; recyclable

AQA Exam Tip: You are most likely to be asked about lithium-ion batteries because they dominate modern consumer electronics. Know their key advantage (high energy density, lightweight) and key disadvantage (risk of thermal runaway/fire if damaged, finite lithium resources).

---

Key Battery Terminology

Term	Meaning
Voltage (V)	The electrical pressure or "push" provided by the battery
Capacity (mAh or Ah)	How much charge the battery can store — higher = longer runtime
Energy density	The amount of energy stored per unit of mass (Wh/kg) — higher = lighter for the same capacity
Cycle life	The number of charge/discharge cycles before capacity drops significantly
Self-discharge	The rate at which a battery loses charge when not in use
Memory effect	A phenomenon (mainly NiCd) where partial discharge cycles reduce maximum capacity over time
Thermal runaway	A dangerous condition where a battery overheats uncontrollably, potentially causing fire

---

Energy Storage Beyond Batteries