Filling the desert with solar panels – a good idea, right?

What’s happening? The construction of huge arrays of solar panels in the Sahara Desert could boost the production of renewable energy, but could also harm the planet’s climate, according to international researchers. Solar panels absorb the majority of the sunlight received, but a relatively small proportion of incoming energy is converted to electricity, with the remainder returning to the environment as heat, which could have global consequences. (Geophysical Research Letters, The Conversation)

Why does this matter? Schemes to fill the Sahara with solar panels to supply Europe with renewable energy have been drawn up, and fallen apart, before – but the basic concept at first glance seems like a sound one. Theoretically, if less than 2% of the Sahara’s space was covered with panels this could power the entire world. What’s not to like?

Aside from the practical limitations of actually carrying this out, which includes questions about the scale of the workforce needed for operations and maintenance, the recent study points to a more wide-ranging issue – the impact on global climate. Significant local heating brought about from the relatively darker solar equipment absorbing solar energy could result in atmospheric “teleconnections” – where a stimulus in one area affects the climate in another part of the world. It’s thought the additional heat in the Sahara could trigger the Amazon to be dried out, reduce the Arctic’s sea ice extent, and enhance tropical cyclones.

This raises a pretty fundamental problem for a solution conceptualised in part to tackle climate change. On top of the impacts above, there could be more – the authors point out their study does not take into account the potential decrease of Saharan dust reaching the atmosphere, which is an important source of nutrition for plant life in the Amazon.

So, is it a bad idea? While a Saharan solar power facility at the scale of need to power Europe, or the world, may be fanciful, large-scale solar plants are being installed in the desert. Morocco’s 800 MW Noor project, a mix of both PV and concentrated solar power with molten salt storage, is due to be expanded as part of the country’s plans to install 3 GW of renewables capacity by 2030.

On this smaller scale there are still issues to contend with, however. Noor’s renewable power comes with a significant water cost. Part of the power plant uses a wet cooling system that needs up to three million cubic metres of water a year, significantly more than a typical coal-fired power station uses. While technological solutions are available to fix this in new designs, clearly this is not a great look for a facility in such an arid climate.

Trade-offs – This story acts to highlight the potential trade-offs that are inherent with many solutions to tackle climate change. There is another related to one technology used in Noor – the Eye of Sauron-like solar tower, which uses mirrors to concentrate the sun’s rays at a high point to make stream and drive a turbine. These concentrated rays are so strong in similar plants in California they literally ignite birds that fly into their path.