100% Renewable. It’s a phrase that gets tossed around with increasing frequency with the renewable energy crowd, climate change proponents and even with elected officials. While the phrase has become ever increasingly popular, very few users fully understand that the term 100% renewable is virtually 100% impossible. Let’s examine why this term so amusing.
First, we must begin with what the composition of a truly 100% renewable grid looks like. Power production would come from two primary sources, wind and solar, with batteries connected to provide power production when the two primary sources are not generating (i.e. when the wind is not blowing, or the sun is not shining). While it sounds great in theory, it falls completely flat in reality.
The first big obstacle to a 100% renewable world is the sheer scale. Where renewable energy currently makes up about 2% of the world’s energy production, to become the sole source of energy generation it would have to see a 90-fold increase in utilization. Keep in mind that fossil fuel witnessed a 10-fold increase in the last 50 years. So, what would be the likelihood that in the next 10 to 30 years an expansion of renewables would be deployed 9X greater than the expansion of fossil fuels in just a fraction of the time.
Let’s forget about the scale of the project for now and focus more on the technology. Renewable advocates are constantly touting the efficiency gains renewables have been achieving with even greater advances on the horizon. While it is true that renewables have become more efficient, and more efficiencies are to come, they will encounter what all technologies have encountered, the principle of diminishing returns. This is a normal phenomenon encountered by all physical systems where engineers achieve big gains in early years and over time the gains become miniscule. Its not that we don’t want to have faith in technology, but unfortunately our world is governed by the laws of physics and not fantasy.
No matter how we want to “feel”, we can’t overlook or even argue the laws of physics. Physical laws of nature prescribe that every technology has a maximum theoretical efficiency. For the combustion engine it is known as Carnot efficiency. Carnot efficiency for an engine is roughly 80% and in the evolution of the combustion engine, engineers have only been able to achieve between 50%-60%. For wind power it is called the Betz limit and efficiency is capped at roughly 60%. The most modern wind turbines currently are around 45%. With Photovoltaic the physics boundary is the Shockley-Queisser limit which proposes a limit of 33% with some arrays currently achieving around 26% efficiency. What I am driving at is that we should not expect any earth-shattering technological advancements that would assist with the sensational 90-fold increase in renewable deployment that would be necessary to transform the world to 100% renewable.
I’ll conclude with a short discussion on batteries. Batteries have some extreme shortfalls as the sheer number that would be required to power the grid in the absence of wind or solar is mind boggling. I’ll use the following analogy as I think it sums it up best. At any given time, the U.S energy grid has enough fossil fuels stored to power the grid for two full months. This includes coal, natural gas and other heating fuels. If we examine the Tesla “Gigafactory” in Nevada which is the largest battery production facility in the world, its annual battery production could power the U.S grid for three minutes. To just power our grid for two days, it would take 1000 years of Gigafactory production, to power the full two months it would take 30,000 years of battery production. Even if we could produce them, where would we put them?
I hope you see that a 100% renewable grid, short of a technological “miracle”, will never be a reality. In this discussion we only talked about the scope of the project and some natural limitations to the technologies, but renewables have a host of other serious issues to overcome. I’m scared to even begin to discuss the cost. As I see it, the only way to be truly 100% renewable is to essentially give up energy.