The 100 Percent Renewable Dream: A Problem of Physics and Scale
By Brent Bennett, Ph.D. and Michael J. Nasi, Life:Powered
The drumbeat of press about the declining costs of installing wind and solar generators has led most of the public and our policy-makers to believe that an energy transition from fossil fuels to wind and solar is just around the corner. However, this belief overlooks the fundamental physical limitations of producing electricity from wind and solar. There is a wide gulf between using wind and solar energy for marginal electricity production, as we are doing now in many places, and relying on it for the majority of our electricity.
In this piece, we will elaborate on the two biggest challenges of generating electricity from wind and solar – energy storage and energy density – and explain why making the energy transition a reality is not just a problem of technology but primarily one of physics and scale.
It is often said that the biggest problem with wind and solar energy is their intermittency, the fact that a wind or solar generator cannot count on exactly how much wind or sun they’ll have at any time. But the wind is always blowing and the sun is always shining somewhere, and there is plenty of wind and sun at any given time around the globe to meet our needs. Intermittency is fundamentally a local problem.
Fossil fuels are also unevenly distributed throughout the world. They must be mined, stored and transported in discrete amounts to where they are needed. What allows coal, gas and nuclear to reliably power our electric grid 24/7 is the flexibility they provide and the infrastructure available to store and transport them. Whether in an oil barrel, a gas tank or a coal yard, it is possible to store fossil fuels cost-effectively and have them ready to be used at any time. No energy resources come to us in a magic continuous stream. Fossil fuels are unique because they are energy-dense and easy to store.
The problem with wind and solar energy is that they cannot be stored and transported like fossil fuels. They must first be converted to electricity, and storing and transporting electricity is difficult and expensive. This is the fundamental physical problem with the 100 percent renewable dream. Transporting the electricity for a 100 percent wind and solar grid would be a huge task, requiring a massive investment in transmission lines. A lot of energy would be lost in long-distance transmission, and the lines would bring significant property and environmental impacts. But storing electricity is the real backbreaker.
Let’s compare what it takes to store coal at a 500 MW power plant versus storing an equivalent amount of electricity from wind or solar in a lithium-ion battery. A typical 500 MW unit can convert a thousand tons of coal into 2,500 MWh of electricity in five hours. A 2,500 MWh battery that mimics the power plant, providing a constant 500 MW for five hours, would cost nearly $600 million at today’s prices, compared to about $30,000 for the thousand tons of coal.
However, even that comparison is generous. Providing 500 MW of 24/7 power from a 100 percent wind and solar grid will require significantly more than 500 MW of wind turbines and solar panels and at least a full day of energy storage in the best of locations. Comparing the levelized cost of 500 MW of wind and solar to a 500 MW coal plant does not account for the difference in the cost of the stored energy in coal vs. storing that much electricity in a battery.
By reducing the land needed for energy production, energy-dense fuels have saved our forests, expanded the efficiency and available land for agriculture, and reduced the need to dam rivers. When considering a transition to wind and solar energy, we have to account for their low energy density relative to fossil fuels. The impact on the land of collecting diffuse wind and solar energy and mining the materials for wind turbines and solar panels is difficult to overstate.
A 1,000 MW power plant using wind requires approximately 60 times as much land as a coal plant, including the land needed to extract the coal, and a solar plant 13 times as much. That calculation notably excludes the land needed to make the components for wind turbines and solar panels and to build the extra transmission lines they require, which varies dramatically depending on location. Relying on wind and solar for a majority of our energy needs will undoubtedly require an expansion of our energy footprint dozens of times over.
To say it more simply, energy density equals environmental stewardship. A major problem in the energy narrative today is the myopic focus on air emissions, particularly carbon dioxide. We’ve done a tremendous job reducing our emissions of real air pollutants known to cause human harm, such as particulate matter and nitrous oxide, by nearly 75 percent over the past 50 years. However, we’ve elevated the status of CO2 so high – even though its impact on our climate is very uncertain – that wind, solar, hydro and geothermal are the only resources driving our national conversation about energy.
Our energy system has become so complex and so effective that most people take it for granted and don’t understand even the smallest pieces of it. It is not enough to use facts to explain why policies that will force us to rebuild our energy system will also destroy the prosperity and freedom we enjoy. We have to teach, persuade and demonstrate why people must care about where their energy comes from. Only then will they understand why we can’t simply legislate a new energy system into existence.
Our prosperity has grown so much over the past century that most Americans are unaware of what life is still like for the millions of Americans still living in energy poverty and the billions around the world with zero or limited access to energy. Our societal values have shifted away from maximizing human flourishing toward minimizing human impact at any cost, and we spend billions of dollars on minor environmental problems – often with no measurable benefits – instead of working to relieve the real and substantial human suffering that still exists in the world today. We need to restore balance to this conversation, not just to maintain our prosperity and freedom, but also to help the billions around the world who are entitled to enjoy the prosperity and freedom that affordable and reliable energy provides.
Brent Bennett, Ph.D., is the policy analyst and Michael J. Nasi is the director of Life:Powered, an organization focused on raising America’s energy IQ.