Energy Generation & Storage
Energy Generation & Storage
Every product that needs power must get its energy from somewhere. As a designer, you need to understand how energy is generated, how it can be stored, and how to choose the right source for a particular product or power system. This lesson covers fossil fuels, biofuels, renewable sources and the systems used to power products.
Fossil Fuels and Biofuels
Fossil fuels — oil, gas and coal — are burned in power stations to heat water into steam, which turns turbines connected to generators. They are reliable and produce a large amount of energy on demand, but they are a finite resource and burning them releases carbon dioxide, contributing to climate change.
Biofuels are produced from organic material rather than fossilised remains. Biodiesel is made from vegetable oils or animal fats and can replace diesel in engines. Biomass involves burning organic matter, such as wood chips, crops or waste, to generate heat or electricity. Biofuels are often considered more sustainable than fossil fuels because the plants used absorb carbon dioxide as they grow, but growing fuel crops still requires land, water and energy.
Fossil fuels (oil, gas and coal) are reliable and produce a high energy output, but they are finite and burning them releases carbon dioxide.
Renewable Energy Sources
Renewable energy comes from sources that are constantly replaced by nature rather than being used up. Renewable sources you need to know for this topic are wind, solar, tidal, hydro-electrical and biomass. You should also be able to discuss non-renewable generation from fossil fuels and from nuclear power.
Wind power uses turbines to convert the kinetic energy of moving air into electricity. Wind farms can be built onshore or offshore. Wind produces no emissions while generating electricity, but its output depends on the weather and turbines can affect local wildlife and views.
Solar power uses photovoltaic cells to convert sunlight directly into electricity. Solar panels have no moving parts, need little maintenance and can be built into individual products as well as large solar farms, but they only generate power in daylight and produce less energy in cloudy conditions.
Tidal power uses barrages or underwater turbines to capture energy from the rise and fall of the tide. Because tides follow a predictable pattern, tidal power is a reliable source of energy, but the equipment is expensive to install and can disturb marine habitats.
Hydroelectric power uses the flow of water, often from a dam, to turn turbines connected to generators. It can respond quickly to changes in demand and produces no emissions during operation, but building a dam can flood land and displace communities.
Wind, solar, tidal and hydroelectric power all generate electricity with little or no emissions during operation, but each depends on weather, location or expensive infrastructure.
Powering Systems
Once energy has been generated, it needs to be delivered to a product in a usable form. A battery stores chemical energy and releases it as electricity — single-use cells are used in low-drain products such as remote controls, while rechargeable cells power products such as phones and power tools. Solar cells can be built into a product itself, such as a calculator or a garden light, so it generates its own power without needing a plug or replacement batteries.
Mains electricity is the most common power source for products used in a fixed location, such as a washing machine or a desktop computer, because it can supply continuous, high power output without running out. Wind power can also feed electricity directly into a product’s power system, although it is more commonly used to supply the national grid.
Calculating Energy Use
Exam questions on energy sometimes ask you to calculate how much energy a product uses, so it is important to show every step of your working. Energy used is found using: $$\text{energy (Wh)} = \text{power (W)} \times \text{time (h)}$$ For example, a fan rated at 12 watts running for 4 hours uses \(12 \times 4 = 48\) watt-hours of energy. Marks are usually available for the correct formula, the correct substitution and the correct final answer, so setting your working out clearly can earn credit even if your final figure is wrong.
Choosing the Right Energy Source
When a designer chooses an energy source for a product or power system, several factors must be balanced against each other.
Portability matters for products used away from a power supply — a torch or portable speaker needs batteries or a solar cell, not a mains lead.
Environmental impact must also be weighed up: a rechargeable battery or solar cell produces far less pollution over its lifetime than repeatedly buying single-use batteries.
Power output determines whether a source can run a product properly — a small solar cell might power a calculator but could never run a washing machine.
Circuit and system connections must match the chosen source: a product designed to run from a 9V battery cannot simply be plugged into mains electricity without a transformer to change the voltage.
Finally, cost affects the decision — mains electricity is cheap to run for high-power products, while batteries are more practical, though more expensive per unit of energy, for portable, low-power products.
Designers consider portability, environmental impact, power output, circuit/system connections and cost when choosing an energy source for a product.