Does harvesting renewables like solar and wind change the planet slightly? Is there a tipping point where this harvesting becomes as harmful as the effect of fossil fuels?
Alex McDowell
London, UK
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Covering a fifth of the Sahara desert with solar panels would have adverse effects on world climate.
A found that covering the entire Sahara with wind farms and solar panels would double the local rainfall, improve vegetation and help power the world. However, another looked at the global impacts this would have. It found that effects on Earth’s climate systems from covering just 20 per cent of the Sahara with solar panels could offset any local benefits.
Solar cells are darker than sand and only convert about 15 per cent of light into electricity, hence there would be a local temperature rise of around 1.5°C. The warmer air would rise and moist air would be drawn in from the coasts, resulting in rainfall and greening of the desert. Due to interactions of this region with others, there would be droughts in the Amazon and a rise in temperatures elsewhere, including in polar regions, leading to melting of the ice caps.
Hillary Shaw
Newport, Shropshire, UK
All renewables demand resources that could be used elsewhere, such as minerals and land. It is partly an economic argument: making a resource (energy) more plentiful through renewables will lower its price, and that encourages more use, not conservation. However, if we don’t create more renewable energy, energy may remain costly and impoverish lower-income people and nations without energy resources. That may discourage installing energy conservation measures. For example, poorer homes might miss out on heat pumps and lower-income nations may retain wood or charcoal burning, damaging forests and creating a domestic health hazard.
Specific issues associated with the use of renewables include tidal energy disrupting marine ecosystems and solar energy taking up farmland. Wind harvesting reduces heat transfer (slightly) from the equator to the poles. That is good at the poles, in a warming world, but not for tropical regions.
The best energy conservation policy overall is to use less stuff.
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