Save for later Print Download Share LinkedIn Twitter While every energy scenario assumes thousands of gigawatts of new renewable capacity will be built in the next two to three decades, critics argue this is not feasible. Wind and sunlight are intermittent, they emphasize, which puts the grid — and consumers' safety and finances — at risk when the wind is not blowing and the sun not shining. They also insist that projected renewables growth is so fast that it won't be possible to find enough money to fund projects or enough raw materials and even space to build them. So, objectively speaking, are the critics right? Some of the arguments have more truth and backing than others. Claims related to inadequacy of financing or raw materials are particularly dubious. A shortage of land comes closer to validity, at least for crowded areas — although full conversion of the electricity system to wind and solar would require only 1% of the land on earth, by some estimates. Intermittency is a real problem — but with so many solutions that it no longer worries utilities.Land SpaceBecause of its low density, even in the sunniest and windiest places, renewable energy requires a lot of equipment and, perhaps more importantly, a lot of space. Stanford University's Mark Jacobson has estimated that converting the global power sector to renewables would require 1.6 million onshore wind turbines and 250,000 utility-scale solar power plants, which would occupy some 1% of the global land area.This looks very small but can be an issue in densely populated areas. Jacobson found, for example, that wind and solar plants would take over 6% of Belgium, the Netherlands and Luxembourg in a 100% renewable scenario. This could end up generating a "social backlash" against covering the planet with solar panels and wind mills, predicts consultancy EY's Gus Schellekens.In fact, Northern Europe may not have enough resources and space to accommodate its "energy hunger," industrial gases giant Linde's Tilman Weide recently told Energy Intelligence. He believes, however, that 100% renewables is possible if Europe imports clean energy from sunnier regions in the form of electrolytic hydrogen or derived molecules such as green ammonia.FinancingProjects also need finance. The International Energy Agency found in its recent net-zero report that annual investment in electricity should rise from $0.5 trillion over the past five years to $1.6 trillion by 2030, including $1.3 trillion just for renewables. But money is abundant and not really an issue, even though renewable returns are low — and unlikely to ever increase. Electricity in general is in fact a low-risk, low-return business, which is quite attractive for investors struggling to beat the current very low interest rates.Developers, including oil companies, can take advantage of this to boost returns by leveraging and farming down assets. Rather than finance, the biggest hurdle for projects might be slow permitting, Enel's boss Francesco Starace said in a press interview. Weide concurs. "Building quotas of wind and solar are not growing fast enough," he recently told Energy Intelligence.Raw MaterialsBy contrast, and despite alarmist press reports, availability of raw materials is not a significant long-term problem. Some minerals, such as copper and cobalt, are even expected to be in surplus in the next few years, a recent International Energy Agency (IEA) report found. And while medium-term projected demand surpasses the expected supply from existing mines and projects under construction for many minerals, the challenges are "not insurmountable," said the IEA's executive director, Fatih Birol.Indeed, history suggests that scarcity fears often emerge, particularly when new technologies pick up, but never materialize. Historical examples of concerns that proved unjustified revolved around platinum and platinoid metals in the 1970s and 1980s when catalytic converters were generalized in cars, or oil and gas in the early 2000s when some were predicting supply was about to peak.Intermittency ToolsThe other major criticism against wind and solar relates to intermittency. To make up for periods of reduced wind or sunlight, renewables either need backup or considerable excess capacity. They are both costly and cannot completely eliminate reliability risks, critics say.But utilities and grid operators no longer see intermittency or seasonal variations as a major obstacle. They have a variety of tools to address it, including gas turbines, which can ramp up and down very quickly. Batteries, which are already competitive for managing very short-term fluctuations, are becoming increasingly competitive with turbines for longer periods of operation.Another way of reinforcing a given power system is by expanding its geographic footprint. Weather conditions vary across geographies, and systems under stress can receive help from neighboring ones. This important feature is working well in Europe and most of the US to stabilize grids under a wide range of weather conditions. In Europe, for example, wind and solar account for 55% of generation in Denmark, which is exchanging power with Germany and Sweden, while taking advantage of Norway's hydro storage capacity.Intermittency is costly, critics also insist. The IEA recently introduced a value-adjusted cost of generation to assess each technology’s full system impact. It reflects the average power price a generator can actually capture over the course of a year, and the additional revenue it can gain from being available to run and provide energy or grid services.The IEA's analysis confirms gas turbines are "far more competitive" than their cost of generation alone suggests. Conversely, it shows that solar photovoltaic (PV) suffers from its lack of flexibility and the fact that its output is "highly concentrated during certain times of day." Pairing PV with energy storage technologies will mitigate this effect, the IEA notes.True 'Greenness'In addition to being expensive, renewables are not as clean as they claim, detractors say. A recent report by scientists from University College London (UCL) found that renewable technologies become "relatively less attractive" once indirect emissions are taken into account. But this effect is "not large" because fossil fuel technologies are hugely more carbon intensive than renewables.Rather than impacting renewables as a whole, indirect emissions mostly change relative attractiveness within renewable technologies. UCL modeling found, for example, that wind deployment is slightly increased against every other technology when indirect emissions are accounted. Wind’s life-cycle emissions amount to just 15 kilograms of CO2 per megawatt hour, according to the US' National Renewable Energy Laboratory. That compares to 20 kg/MWh for hydropower, 25 kg/MWh for nuclear and 60 kg/MWh for PV — but 465 kg/MWh for combined-cycle gas turbines and 1,050 kg/MWh for coal.Philippe Roos is a senior reporter at Energy Intelligence based in Strasbourg, France.