Energy Generation and Storage
Energy in Design and Technology
Every product requires energy to manufacture, and many require energy to use. Designers must understand where energy comes from and how it is stored, because these choices affect a product’s sustainability, cost and practicality. Energy sources fall into two broad categories: renewable energy and non-renewable energy.
Renewable Energy Sources
Solar (photovoltaic): Photovoltaic (PV) cells convert sunlight directly into electricity. Silicon-based PV cells are the most common. Solar panels on buildings and integrated into products (calculators, garden lights) reduce dependence on mains power. Efficiency of commercially available panels typically ranges from around 15–22% for silicon cells.
Wind: Wind turbines use the kinetic energy of moving air to spin a generator. Onshore turbines are cheaper to build and maintain; offshore turbines benefit from stronger and more consistent winds. Wind power is intermittent — output depends on wind speed — so energy storage is needed to smooth supply.
Hydroelectric: Water flowing through a turbine — usually in a dam — generates electricity. Hydroelectric power is reliable and controllable, but requires a suitable geographical location and raises environmental concerns about the habitat flooded by reservoirs.
Geothermal: Heat from the Earth’s crust is used to generate steam that drives turbines or to heat buildings directly. Practically available in regions with volcanic activity, such as Iceland, but less so in the UK.
Biomass: Organic material — wood, crop waste, dedicated energy crops — is burned or fermented to release energy. It is considered low-carbon (the CO₂ released was recently absorbed by the growing plant), but combustion still produces particulates and other pollutants.
Wave and tidal: The movement of ocean waves and tidal flows can drive turbines. The UK’s coastal location makes these sources potentially significant, but the technology is less mature and more expensive than wind or solar at present.
The six main renewable energy sources covered in this course are: solar, wind, hydroelectric, geothermal, biomass, and wave/tidal. All are replenished naturally, but most are intermittent or location-dependent — requiring storage or grid balancing to be practically useful.
Non-Renewable Energy Sources
Fossil fuels — coal, oil and natural gas — were formed over millions of years from the remains of ancient organisms. Burning them releases the carbon stored in them as CO₂, contributing to the greenhouse effect and climate change. They are energy-dense and have well-established distribution infrastructure, which is why they still supply the majority of global energy.
Nuclear power is sometimes described as ‘low carbon’ because it does not burn fuel. Uranium atoms are split in a process called fission, releasing large amounts of heat used to generate steam and electricity. Nuclear power produces a reliable baseload of electricity without direct CO₂ emissions, but generates radioactive waste that must be stored safely for thousands of years, and carries a small risk of catastrophic accidents.
The following table compares key characteristics:
| Feature | Fossil fuels | Renewables (e.g. solar/wind) |
|---|---|---|
| Availability | Finite; will run out | Continuously replenished |
| CO₂ emissions | High | Low to zero during operation |
| Reliability | On-demand (energy-dense) | Often intermittent (wind/solar) |
| Infrastructure | Well-established | Expanding rapidly |
Energy Storage for Products and Manufacturing
Many products need to store energy so they can be used without a permanent connection to the mains. The main storage methods are:
Batteries are the most common energy storage for portable products. Rechargeable lithium-ion batteries power smartphones, laptops and electric vehicles because of their high energy density and long cycle life. Non-rechargeable alkaline batteries are used in lower-drain products such as TV remotes. Battery disposal is an environmental concern — lithium and other metals require specialist recycling.
Mains electricity powers most manufacturing equipment and large household appliances. It is reliable and effectively unlimited in supply, but the carbon intensity of the grid depends on how the electricity was generated — a factory powered by renewable electricity has a lower carbon footprint than one on coal-sourced power.
Wind-up mechanisms store mechanical energy in a spring. Traditionally used in clockwork mechanisms and wind-up toys, they are now applied in products for regions without reliable electricity — such as wind-up radios and torches designed for off-grid use in developing countries. The Freeplay wind-up radio is a well-known example of this approach applied for social good.
Lithium-ion batteries are preferred for portable and high-drain applications because of their high energy density (they store a lot of energy per unit of weight) and long cycle life (they can be recharged hundreds or thousands of times). Alkaline batteries have lower energy density and cannot be recharged.
PV cells can be integrated directly into products to provide power without batteries or mains connection. Applications include: solar-powered calculators (very low power draw — even indoor light is sufficient); garden lighting (PV cell charges a battery during the day, powers LEDs at night); and building-integrated PV panels on roofs and facades. In wearable technology, flexible thin-film PV cells are being embedded into clothing and backpack fabric, though efficiency remains lower than rigid silicon cells. The key design consideration is surface area: PV cells must be exposed to light, which affects the form and orientation of the product.