The climate cost of 100% renewable energy

06/09/2017 05:34 am ET Updated Jun 12, 2017

How much fossil fuels are needed to build a CO2 free energy system?

Also without President Trump on board, with the landmark Paris Agreement adopted in December 2015, more than 190 governments committed to endeavor to keep global warming below 1.5 °C and set a deadline for net zero greenhouse gas emissions in the second half of this century. This historic agreement signals what lies ahead: the unprecedented and complete decarbonization of the energy system, transforming it to 100% renewable energy within the next few decades.

While this is probably the biggest challenge of today's generation, the good news is that this transformation is feasible. Already in 2009, Stanford researchers Jacobson and Delucchi showed that wind, water and solar technologies can provide 100% of the world's energy by 2030. In 2015, the Greenpeace Energy [R]evolution scenario concluded that moving towards 100% renewable energy by 2050 is even cost competitive, and can be entirely financed by fuel cost savings. In addition, job numbers in the RE industry may reach more than 46 million by 2030. A new model developed at Lappeenranta University of Technology in 2016 shows how a 100% renewable electricity system can be realized for all hours of the year by 2030, meeting the targets set by the Paris Agreement. In fact, looking across the world, an increasing number of cities, municipalities, regions and countries prove that setting a 100% RE target is a viable political decision today. Many consider it not only a technically and economically feasible option but an ethical imperative in the face of global climate change.

While this transition will ultimately lead to a fully decarbonized energy system, some fossil fuel based energy needs to be invested to actually build it. A popular objection from the critics of a fast RE transition is that the installation of 100 percent RE itself needs so much additional energy that it would thwart the intended reduction of CO2 emissions. And indeed at the early stage of the RE transition, the production of PV units for example was very energy intensive.

The encouraging news is that the energy payback time for renewables has decreased dramatically over the past years. Looking at photovoltaics material usage for silicon cells has been reduced significantly during the last 10 years from around 16 g/Wp to less than 6 g/Wp due to increased efficiencies and thinner wafers.

Despite this, concerns continue to be raised around the question: ‘Is the energy demand needed for a fast 100 RE transition so high that it could hinder the speedy global reduction of CO2?’

The World Future Council and LINGO have estimated the additional energy required and the related CO2 emission generated to build a 100% RE infrastructure. As a starting point, we assumed a global energy demand figure of 23.6 Terawatt in 2050 (Greenpeace Energy Revolution, 2015, page 13).

Because the energy needed to produce RE units decreases over time and also differs depending on the technology used, we can only roughly estimate the size of the CO2 emissions generated by the energy transition (for detailed calculation see here).

Our calculation shows that about 25 Gt CO2 will be emitted to build a 100% RE system. Currently, the world emits 40 Gt CO2 annually. From the perspective of a global carbon budget, one could say that the global energy transition to 100% renewable energy comes relatively “cheap” - needing less than a year's worth of global emissions. However, the science on the long-term impacts of CO2 levels above 350ppm (Hansen et al. 2008) suggests that there is no room for complacency. We urgently need to undertake the transition to a 100% clean energy economy on a global scale to make sure that global warming does not trigger a run-away reaction in the global climate system, involving huge carbon “bombs” such as methane clathrates from the ocean floor that may dwarf human emissions.

The above-mentioned commitments to 100% RE are very encouraging. But, current policy pathways are far from steering us in this direction. Some governments are actually slowing down the transformation, legislative measures are falling short and fossil energy interest groups are gaining political power.

Instead, policy makers should incorporate these facts when developing their NDCs and national fiscal and energy policies in the coming years. Fossil fuel subsidies must be phased out quickly, energy policies must be redirected towards meeting basic needs in an efficient way, new financing mechanisms for the renewable energy roll-out must be established and above all, investments and support for new fossil fuel extraction and infrastructure must urgently be halted.

Our calculation gives hope that the transition to 100% renewable energy can be achieved without adding a huge burden on atmospheric CO2 levels. This will not happen in time for avoiding climate chaos without substantial additional efforts.

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