Sources of Electrical Energy
- An electric cell stores chemical energy that can be transferred to electrical energy
- Electric cells, batteries and other sources of electrical energy come in many forms, such as
- Chemical cells
- Solar cells
- Mains electricity
- Wind generators
Chemical Cells
- Batteries, or chemical cells, utilise chemical reactions to provide a potential difference
- They can be rechargeable or non-rechargeable
- Non-rechargeable batteries are by definition, only able to be used once as the chemicals within them are used up
- Examples include alkaline, or AA batteries, common in many small devices
- Rechargeable cells can be used many times as they are attached to a charger and the chemical reaction is reversed allowing the cells to store energy for use once again
- Examples include:
- Lithium-ion batteries used in laptops and other mobile devices
- Lead-acid batteries such as those used in cars and other motor vehicles
Solar Cells
- Photovoltaic cells in solar panels convert electromagnetic radiation (photons) from the Sun into electrical energy
- When photons from the Sun are incident on the solar heating panels, the light energy is transferred into thermal energy
- The solar photons are absorbed by electrons on the surface of the photovoltaic cells, giving them enough energy to move and be released from the surface
- These electrons transfer the thermal energy into electrical energy which is then transferred to the external circuit
Solar panels use solar cells to transfer energy from electromagnetic radiation into electrical energy
Advantages & Disadvantages
- Each energy source has its advantages and disadvantages, some of these are shown in the following table
| Battery type | Advantages | Disadvantages |
| Single-use battery (e.g. alkaline AA battery) |
high energy density convenient source of energy used in everyday appliances portable source of electrical energy potential to join many in series to increase p.d. low cost |
non-rechargeable/limited power supply and will need replacing high internal resistance disposal issues/contributes to pollution made from non-renewable materials |
| Mobile phone battery (e.g. lithium-ion battery) |
very high energy density high electrical efficiency convenient source of energy used in everyday appliances rechargeable, long lifetime fast charging time portable source of electrical energy low internal resistance |
capacity of the cell degrades over time internal resistance increases over time expensive |
| Car battery (e.g. lead-acid battery) |
low cost rechargeable able to deliver very high currents in a short time |
low energy density - very heavy compared to power output internal resistance increases as battery degrades limited number of full discharge cycles disposal issues/contributes to pollution, uses toxic and corrosive materials made from non-renewable materials |
| Solar cell |
unlimited supply of energy clean to produce the electricity freely available everywhere cheap maintenance no fuel is required for energy |
variable output, highly dependent on weather conditions impacted by poor weather limited efficiency only available during the day requires large investment upfront requires large areas |
| Wind generator |
zero fuel costs, freely available no chemical pollution always sustainable and will never run out high set-up cost but becomes economical |
inconsistent output, highly dependent on weather conditions requires favourable local conditions to be placed in windy locations noise/visual pollution |
| Mains electricity (fossil fuel generator) |
extensive infrastructure in place high energy density of fuel reliable/available energy at any time well-known and developed technology |
produces greenhouse gases unsustainable (non-renewable) produces pollution |
Exam Tip
You do not need to know the inner workings of all the cells. However, you must be able to compare the advantages and disadvantages of using each cell as an energy source.