Uses and Reliability of Energy Resources

Worked Example:

Calculate the kinetic energy of a 1200 kg electric car travelling at 20 m/s.

• Step 1: Identify values: $m = 1200\text{ kg}$, $v = 20\text{ m/s}$.
• Step 2: Substitute into the equation: $E_k = 0.5 \times 1200 \times 20^2$
• Step 3: Calculate the final answer: $E_k = 240,000\text{ J}$ (or $240\text{ kJ}$).

Comparing Energy Resources for Heating

• Why does a hot water radiator stay warm long after the boiler turns off?
• Heating buildings and water accounts for a massive portion of national energy use.
• Historically, heating relied heavily on non-renewable resources, but there is an increasing use of renewable alternatives.

• Specific Heat Capacity is used to calculate the energy required by these heating systems: $\Delta E = m \times c \times \Delta\theta$.

Comparing Energy Resources for Electricity Generation

• Behind every plug socket is a complex chain of energy transfers starting at a power station.
• The National Grid is supplied by a mix of non-renewable and renewable energy resources.

• In most power stations, a fuel is used to turn a turbine, which then turns a generator to produce electricity.
• Different resources have different energy transfers:
  • fossil fuels: Chemical $\rightarrow$ Thermal (water/steam) $\rightarrow$ Kinetic (turbine) $\rightarrow$ Electrical.
  • Nuclear: Nuclear store $\rightarrow$ Thermal $\rightarrow$ Kinetic $\rightarrow$ Electrical.
  • Hydroelectric: Gravitational Potential Energy (water) $\rightarrow$ Kinetic $\rightarrow$ Electrical.
• Power station efficiency is calculated using:

Understanding Reliability and Environmental Impact

• Imagine if your TV only worked when the wind was blowing outside.
• A Reliable Energy Resource is one that can provide energy at any time to meet demand, independent of the weather.
• fossil fuels, nuclear, biofuels, geothermal, and tides are reliable. Tides are considered reliable because they are completely predictable twice daily.
• Wind, solar, and water waves are Intermittent (unpredictable and weather-dependent).
• Environmental impacts vary drastically: burning fossil fuels releases Carbon Dioxide ($CO_2$), which contributes to global warming, and Sulfur Dioxide ($SO_2$), which causes acid rain.
• biofuels are considered Carbon neutral because the $CO_2$ absorbed by the plants during growth equals the $CO_2$ released when they are burned.

Managing the National Grid: Base Load and Peak Demand

• The National Grid must constantly balance the electricity generated with the electricity demanded by the country.
• Base Load is the constant, minimum level of electricity demand required 24 hours a day. This is met by nuclear and coal power stations because they have long start-up times (nuclear takes up to 48 hours) and run efficiently continuously.
• Peak Demand occurs during sudden increases in electricity usage. This is met by natural gas (which has a fast start-up time of about 30 minutes) and Pumped storage.
• Pumped storage acts like a giant battery to manage demand. During low demand at night, surplus base load electricity pumps water up to a high reservoir (storing Gravitational Potential Energy).
• During peak demand, the water is released through a turbine to generate electricity almost instantly.