Global Energy Resources: Trends, Intermittency, and Innovation

Comprehensive practice questions covering global energy trends, renewable engineering (HAWT vs. VAWT), solar technologies, biofuels, and nuclear waste management based on lecture notes.

How did the global percentage supply of solar power change between 2012 and 2021?

Solar power supply grew from near $0.5\%$ in 2012 to approximately $3.7\%$ in 2021.

What are the primary drivers for the rapid transition to solar energy?

The trend is driven by falling costs and government subsidies aimed at reducing greenhouse gas emissions.

Why can 10-year energy plans suddenly become obsolete?

Rapid innovation, such as a sudden breakthrough in battery storage or solar panel efficiency, can render plans obsolete in just a few months.

How does cloud cover impact the reliability of solar power?

Cloud cover can cut solar output by $90\%$ in a matter of minutes.

What are the three main advantages of biofuels like ethanol?

1. Reliability (they are not intermittent); 2. High energy density (portable); 3. Infrastructure (compatible with existing engines/fuel stations).

Why is the carbon neutrality of biofuels often considered a myth?

While the plants absorb $CO_2$ during growth, carbon is added to the cycle through the use of fossil fuels for tractors, fertilisers, and processing.

What are the environmental and health consequences of burning wood with more than $20\%$ moisture?

It leads to incomplete combustion (wasted energy) and emits more than twice the smoke particles ($PM2.5$ and $PM10$), which can cause respiratory issues.

What are the specific advantages of Horizontal Axis Wind Turbines (HAWTs)?

HAWTs offer higher efficiency because blades stay perpendicular to the wind, tall towers reach stronger winds, and variable pitch blades can maximize energy or 'feather' during storms.

In what scenarios are Vertical Axis Wind Turbines (VAWTs) superior to HAWTs?

VAWTs are better for urban rooftops because they handle turbulent wind well and are quieter; they are also easier to maintain as the generator and gearbox are at ground level.

How does Photovoltaic (PV) solar technology generate electricity?

It uses semi-conductor materials like silicon to convert photons directly into a flow of electrons ($DC$ electricity).

What is Passive Solar Architecture?

A building design technique that uses orientation, thermal mass (such as concrete floors), and glazing to trap heat without mechanical systems.

Compare the properties of Alpha ($\alpha$), Beta ($\beta$), and Gamma ($\gamma$) radiation.

Alpha has high ionising power but low penetration (stopped by paper); Beta has moderate ionising power and penetration (stopped by aluminium); Gamma has low ionising power but high penetration (stopped by thick lead).

What is the definition of radioactive half-life?

Half-life is the time taken for half of the radioactive nuclei in a sample to decay.

How does a short half-life differ from a long half-life in terms of activity and safety?

A short half-life means activity falls quickly and is safe sooner despite intense initial radiation; a long half-life means activity falls slowly and remains hazardous for thousands of years.

What is vitrifaction in the context of nuclear waste management?

It is the process of mixing liquid radioactive waste with glass and solidifying it into blocks to prevent leakage.

What three methods are used for managing nuclear waste?

1. Cooling Ponds (water absorbs heat and blocks radiation); 2. Vitrifaction (mixing waste with glass); 3. Deep Storage (sealing in steel containers buried in stable rock).