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Renewables

Renewable energy has space to grow

20 Aug 2019
Wind turbines on a hill

By replacing fossil fuels with renewable energy nations could achieve their emissions commitments without encroaching on vital natural land, according to researchers in the US.

Low-emission energy sources like wind and solar can have a larger geographical footprint than fossil-fuel plants of equivalent capacity. Even so, the renewable-energy potential of already developed land is more than enough to fulfil pledges made as part of the Paris Agreement and could satisfy the total energy demand projected for 2050, the analysis shows.

At the 21st Conference of the Parties (COP21) in Paris in 2015, 196 countries agreed to aim to limit warming to less than 2 °C above pre-industrial levels. The rapid cuts in greenhouse-gas emissions needed imply a large-scale shift away from fossil fuels. Renewable-energy schemes are not without environmental impact themselves, however, so it’s important to choose locations and generation techniques that cause the least possible harm.

“Similar to conventional energy sources, we need to think beyond just the direct footprint of the wind turbine or solar panel and consider the associated structures and roads that renewable energy development brings with it,” says Sharon Baruch-Mordo of The Nature Conservancy, US. “The total sum of such development causes fragmentation of natural lands at a greater scale and creates disturbances that degrade the habitat.”

Natural lands are still relatively free from the direct impact of development; they’re typically forests, grasslands and other ecosystems that have not been appropriated for agriculture or other uses. Converting such areas to human use decreases their biodiversity and releases carbon stored in soils and biomass.

To determine whether land that is already compromised holds enough potential for renewables, Baruch-Mordo and colleagues calculated how much energy is represented by the greenhouse-gas reductions that each nation has committed to under the Paris climate agreement. The team assumed that cuts in emissions would focus on electricity and heat generation, with renewable-energy sources replacing fossil fuels.

The next step was mapping each country’s potential for wind and solar energy generation on land already converted for human use. The researchers also included the potential output from retrofitting existing hydroelectric plants – assuming their efficiency could be slightly improved – and repurposing non-hydroelectric dams to become power-generating. New dams were disallowed because of the harm they cause to natural river processes.

The analysis showed that the total renewable-energy potential of the world’s converted land is 17 times that required to meet the nationally determined contributions (NDCs) committed to during COP21. What’s more, the 10 largest emitters – including the EU28 as a single region – can all fulfil their pledges using land within their own national boundaries.

For a more ambitious target of total fossil-fuel replacement by 2050 (including transport-related energy generation), the researchers found that, globally, converted land has more than one and a half times the potential capacity needed. Fewer individual nations could achieve the goal independently, however, so international agreements and electricity interconnections would be needed.

Because converted land is already used for other purposes, integrating new energy infrastructure will be challenging.

“While wind farms may be compatible with agricultural land uses, solar farms would completely replace the current use,” says Baruch-Mordo. “On the other hand, solar is highly compatible with urban areas especially on rooftops. Development of new technologies for integration such as solar roads or building-integrated solar thermal can also open new frontiers to incorporate renewable-energy generation into areas already modified by people.”

Baruch-Mordo and colleagues reported their findings in Environmental Research Letters (ERL).

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