Impacts of Renewable Energy Resources

What percentage of a country's energy comes from wind if it produces 30 TWh from wind out of a total 120 TWh?

Step 1: Identify the specific source output and total output.

• $\text{Specific Source Output} = 30$ TWh
• $\text{Total Output} = 120$ TWh

Step 2: Substitute the values into the equation.

• $\text{Percentage} = (30 / 120) \times 100$

Step 3: Calculate the final percentage.

• $\text{Percentage} = 25\%$

Assessing Environmental Impacts

It might surprise you to learn that wind turbines and solar panels are not entirely carbon-free. While renewables produce near-zero emissions during operation, they have a carbon footprint due to indirect emissions released during their manufacture, construction, and transport. For example, the lifecycle footprint of wind is roughly $11\text{ gCO}_2\text{e/kWh}$ and solar is $41\text{ gCO}_2\text{e/kWh}$. However, this is vastly superior to coal, which produces $740 - 1689\text{ gCO}_2\text{e/kWh}$ through direct emissions.

Despite global climate benefits, renewables can have severe local environmental impacts. Hydroelectric power requires massive dams; the Three Gorges Dam in China flooded over $600\text{ km}^2$ of land, causing habitat destruction and releasing methane from decomposing underwater vegetation. Similarly, solar farms compete with agricultural land, and cultivating biofuels can lead to deforestation.

Renewables also have a much lower energy density than fossil fuels. One coal plant produces as much energy as approximately 233 wind turbines. Because so many turbines are needed, wind farms require huge amounts of raw materials and space, which can disrupt migratory patterns and kill birds or bats.

Calculate the percentage carbon saving per kWh when switching from a coal plant emitting $1,000\text{ gCO}_2\text{e/kWh}$ to a wind farm emitting $11\text{ gCO}_2\text{e/kWh}$.

Step 1: Calculate the difference in emissions.

• $1000 - 11 = 989\text{ gCO}_2\text{e/kWh}$ saved

Step 2: Divide the saving by the original coal emissions and multiply by 100.

• $(989 / 1000) \times 100 = 98.9\%$

Social and Economic Impacts

Why do people protest against green energy projects built near their own homes? This phenomenon is known as NIMBYism ("Not In My Back Yard"). Local residents frequently object to visual pollution, arguing that projects industrialise coastlines and rural landscapes. For instance, the Rampion Wind Farm features 116 turbines that are 460ft tall and visible from 20 miles away. Turbines also create noise pollution, generating around $45\text{ dB}$ at a distance of 300m, which is the World Health Organization limit for avoiding sleep disturbance.

Large-scale projects can cause devastating social displacement. The construction of the Three Gorges Dam forced 1.3 million people to relocate. However, renewables also provide significant social benefits through job creation and the multiplier effect. The London Array wind farm created 6,700 jobs during construction and supports 73 to 150 permanent roles, while the Rampion project regenerated Newhaven Port by creating 60 permanent jobs.

Economically, renewable energy projects are incredibly capital-intense. The capital costs (upfront expenses for land and construction) are massive: offshore wind costs between £3m and £4.5m per MW, while onshore wind costs £1m to £1.6m per MW. Furthermore, connecting remote renewable sites (like the Scottish Highlands) to city grids is highly expensive. Conversely, the operational costs (ongoing running expenses) are very low at just 1-2% of capital costs per year, because the "fuel" (wind, sun, or water) is completely free.

Energy Security and Intermittency

The wind does not always blow, and the sun does not always shine. This variability is known as intermittency and is the primary challenge of relying on renewable energy. For example, wind turbines only operate when wind speeds are between $3 - 4\text{ m/s}$ (the cut-in speed) and $25\text{ m/s}$ (the cut-off speed). Because renewables cannot be switched on demand to meet sudden spikes in electricity use, national grids still rely on a base load—a constant, stable supply of power usually provided by nuclear or gas plants.

Despite the challenge of intermittency, developing domestic renewables drastically improves a country's energy security. By generating their own power, countries reduce their reliance on imported fossil fuels and protect themselves from volatile global energy prices. For example, the London Array alone powers 584,000 homes, providing 2.4% of UK domestic electricity in 2020 and helping the UK towards its target of an 80% reduction in carbon emissions by 2050.

To truly overcome intermittency, grids require massive battery storage systems (like lithium-ion batteries) to store excess energy for days when the weather is calm. However, mining and processing lithium creates its own environmental challenges, producing an estimated 1.3 million tonnes of $\text{CO}_2$ globally each year.

Concluding Judgement

Overall, when assessing the impacts of developing renewable energy, the long-term global benefits outweigh the short-term and local drawbacks. While projects require high capital costs and can cause significant local environmental and social disruption (such as habitat loss and visual pollution), these negative impacts are offset by the overwhelming need to mitigate global climate change. Renewables offer vastly lower lifecycle carbon footprints compared to fossil fuels and crucially enhance a country's energy security by reducing reliance on imported, volatile energy sources. Therefore, despite the ongoing challenges of intermittency and storage, the transition to renewable energy is essential for a sustainable future.