1.1.4 Energy Storage & Renewability
D&T 2026 — 1.1 Core Knowledge & Understanding
Renewable and non-renewable energy sources
Renewable energy — energy from a source that is naturally replaced as fast as it is used, so it will not run out.
Non-renewable energy — energy from a finite source that cannot be replaced within a human timescale. Once used, it is gone.
Renewable sources
| Source | How it generates energy |
|---|---|
| Wind | Moving air turns the blades of a wind turbine, which drives a generator. Sited on exposed land or offshore. |
| Solar (photovoltaic cells) | PV cells convert light directly into electricity. Solar thermal panels use the sun’s heat to warm water. |
| Hydrogen fuel cells | Hydrogen reacts with oxygen to produce electricity, with water as the only emission at the point of use. |
| Geothermal | Heat from hot rocks below the earth’s surface heats water to drive turbines or warm buildings directly. |
| Hydroelectric | Water held behind a dam is released through turbines as it falls. |
| Wood and biomass | Organic material — wood, crops, waste — is burned, or converted to biogas, to release energy. |
| Wave and tidal | The movement of waves, or the predictable rise and fall of tides, drives turbines. |
Non-renewable sources
| Source | Notes |
|---|---|
| Coal | Burned in power stations. The most polluting fossil fuel per unit of energy. |
| Oil | Refined into petrol, diesel and the feedstock for most plastics. |
| Gas | Burns more cleanly than coal but is still a fossil fuel and still releases carbon dioxide. |
| Nuclear | Not a fossil fuel and produces almost no carbon dioxide in operation, but the fuel is finite and the radioactive waste stays dangerous for thousands of years. |
Issues surrounding the use of fossil fuels
Coal, oil and gas still supply much of the world’s energy, but their use brings serious problems.
- Greenhouse gases — burning them releases carbon dioxide, the main driver of climate change.
- Air pollution — sulphur dioxide and particulates harm health and cause acid rain.
- Finite supply — reserves are limited, so prices rise and become unstable as they are used up.
- Extraction damage — mining, drilling and fracking damage landscapes and habitats, and spills pollute land and sea.
- Political dependence — countries without their own reserves depend on imports, leaving supply and price vulnerable to events elsewhere.
Advantages and disadvantages of renewable energy
| Source | Advantages | Disadvantages |
|---|---|---|
| Wind | No fuel cost or emissions in use; can be sited offshore; quick to build | Only generates when the wind blows; considered visually intrusive; noise and risk to birds |
| Solar / PV | Free energy once installed; no moving parts so little maintenance; works at any scale from a calculator upwards | Expensive to install; generates nothing at night and less in poor weather; needs a large area for large output |
| Hydrogen fuel cells | Only emission at point of use is water; quick to refuel; high energy for the weight | Most hydrogen is currently made from fossil fuels; hard to store and transport; very few refuelling stations |
| Geothermal | Constant output day and night; very small surface footprint | Only viable in certain locations; high drilling costs; can trigger minor earth tremors |
| Hydroelectric | Reliable and long-lasting; output can be increased on demand; reservoir can store energy | Dams flood large areas and displace people and wildlife; very high construction cost |
| Wood and biomass | Uses waste material; can be regrown; existing power stations can be converted | Burning still releases carbon dioxide and particulates; land used for fuel crops cannot grow food |
| Wave and tidal | Tides are entirely predictable, unlike wind and sun; high energy density | Very high set-up cost; salt water corrodes equipment; can disturb coastal habitats |
Renewable energy in manufacturing
Manufacturing uses a great deal of energy, and most of it still comes from fossil fuels. Moving production onto renewable sources matters because of the scale involved.
- Lower running costs once the installation is paid for, and protection from rising and unstable fuel prices.
- Lower carbon footprint for every product made on the site, which improves the product’s whole life cycle analysis.
- Meeting legal targets on emissions, and meeting the environmental standards customers now demand.
- Factories commonly fit roof-mounted PV arrays, use waste heat recovery, or buy electricity on a renewable tariff.
The barrier is cost. Installing renewable generation is expensive up front, and a factory that runs continuously still needs a supply when the wind drops, so most sites use a mix of sources.
Energy storage
Generating energy is only half the problem. Renewable sources produce power when conditions allow, not when it is needed, so storage is what makes them practical.
| Method | How it works | Typical use |
|---|---|---|
| Batteries | Chemical energy converted to electrical energy. Rechargeable cells reverse the reaction. | Phones, tools, electric vehicles, home storage for solar panels |
| Kinetic / wind-up | Turning a handle winds a spring or drives a small generator, storing mechanical energy | Torches, radios, emergency chargers |
| Pumped storage | Surplus electricity pumps water uphill; releasing it drives turbines when demand rises | National grid balancing |
| Hydrogen | Surplus electricity splits water into hydrogen, stored and later converted back | Fuel cell vehicles, industrial energy storage |
Battery types you should recognise:
- Alkaline (single use) — cheap and widely available, but discarded after one use.
- Rechargeable (NiMH, lithium-ion) — higher initial cost but used hundreds of times, so cheaper and greener overall. Lithium-ion holds more energy for its weight, which is why it dominates in phones and electric cars.
- Batteries contain valuable and hazardous materials, so they must be recycled, never put in general waste.
Energy in motor vehicles
| Type | How energy is supplied and stored | Considerations |
|---|---|---|
| Petrol / diesel | Fuel burned in an internal combustion engine; energy stored chemically in the fuel tank | Long range and quick refuelling, but emits carbon dioxide and pollutants; production of new petrol and diesel cars is being phased out |
| Electric | Battery pack charged from the mains, driving electric motors | No emissions at the point of use, cheap to run and few moving parts, but slower to recharge, limited range, and the batteries are resource-intensive to make |
| Hybrid | Combines a small engine with a battery and motor, recovering energy through regenerative braking | Lower emissions than petrol alone without range anxiety, but more complex and heavier |
| Hydrogen fuel cell | Hydrogen stored in a tank generates electricity on board | Refuels in minutes and emits only water, but refuelling stations are rare |
Energy in household products
- Mains electricity — constant, high power supply for products that stay in one place: ovens, washing machines, televisions. Cheapest per unit but ties the product to a socket.
- Battery — makes products portable and safe at low voltage, used in remote controls, tools and toothbrushes. Limited capacity, and needs recharging or replacing.
- Solar — powers calculators, garden lights and trickle chargers without any wiring, but output depends entirely on light levels, so it is usually paired with a small rechargeable cell.
Renewable energy in products
Designers build renewable generation directly into products so they work without mains power or disposable batteries.
- Photovoltaic cells power calculators, garden and security lighting, road signs, and chargers for phones and small equipment.
- Wind-up (clockwork) technology stores energy in a spring or drives a small generator by hand. Wind-up torches and radios are used in emergency kits and in regions without a reliable electricity supply, where they avoid the cost and waste of batteries entirely.
- Kinetic charging in watches and wearables uses the movement of the wearer to keep the device charged.