Do we currently have the technology to create an energy infrastructure that is based 100% on renewable energy? That is a legitimate and very useful debate to have, and one that is playing out in the published literature.

Two recent systematic reviews in particular take opposite sides of this question. In one Heard et al argue that the burden of proof for feasibility and viability have not been met. In the same journal, Brown et al respond, saying that 100% renewable is both feasible and viable.

Both articles get fairly wonky, but they are reasonably easy to follow for the main points.

Heard argues that studies looking at plans for total renewable energy fail to consider critical factors, such as the feasibility of grid storage, of load balancing, and the necessary ancillary services required to maintain such a grid. They conclude that we would have to reinvent the electrical grid and infrastructure if we wish to go to 100% renewable.

Brown responds by arguing that only incremental advances to evolve our energy infrastructure are needed, and that 100% renewable are feasible with current technology, and economically viable.

From reading both papers, which if you are interested in this topic I suggest you do, I came down somewhere in the middle. I give the edge to Brown, but I think he and his coauthors made a bit of a biased case for renewables. Meanwhile Heard, I think, overemphasized current limitations. I got the sense that both were making a lawyer’s case for their side.

Here is what I get from these articles: First, it seems clear that we are capable of making sufficient energy from renewable sources to meet world demand. Further, renewable energy is cost effective, and the price is continuing to drop. So energy production is simply not the problem.

Further, renewables (mostly wind and solar) have some strong advantages. The first is that they are renewable – they do not depend on a limited resource that will eventually run out. The second is that they do not directly release carbon into the environment. There is a carbon footprint associated with the production of solar panels and wind turbines, but this is a small fraction of other energy sources.

Also, if you consider the externalized costs of the environmental and health effects of fossil fuels, non-polluting energy sources are massively cost effective.

So where are the problems? Renewable energy’s main downside is that they are intermittent, not on-demand. This creates challenges for grid stability, balancing supply and demand, grid storage, and reserve capacity for occasional dry spells (sustained periods of low light or low wind).

Both authors agree that right now we do not have the infrastructure to deal with significant renewable penetration. They differ about how radically and quickly we would have to change or infrastructure – but we have to change it.

Grid storage is clearly needed, and this is the main area where I disagree with Brown. He suggested that existing grid storage options are adequate, and even gave a positive nod to lithium ion batteries.

However, while he gave us calculations on the finite amount of uranium in the world, there was no mention of the finite amount of lithium and rare earths. We may find more reserves of lithium, but we may also find more reserves of uranium. We may find substitutes for lithium and the rare earths, but we also may develop thorium reactors (thorium is much more abundant than uranium).

In any case, I simply don’t think we are there yet with battery technology. We are making steady incremental advances, and I think we will get there, but we may be 10-20 years away from a viable widely distributed system of grid storage based on battery technology.

There are other options, which I review here, but none of them great. Pumped hydro is the best, but is limited by terrain. We may need to develop hydrogen fuel cells, use renewables to make hydrogen, and use the hydrogen to store the energy. But this will require a massive change to our energy infrastructure.

This is where I think Brown skirted some real issues. He essentially argued that there are options that do not require any new technology or massive upgrade to the system, and there are options that can meet all our demands. But these are not the same options – there are no options that meet all the criteria he detailed at the same time.

Another alternative to grid storage to level off supply and demand is simply demand capacity – creating electricity on demand as needed. Brown acknowledges that worst case we may need to keep some fossil fuel plants on hand to meet demand needs.

He also points out that nuclear is not a good option for demand power generation. Nuclear plants operate most effectively when they are always on a peak production. But there is a recent analysis that indicates that nuclear power plants can produce variable power to meet demand, and that this would improve the economics of nuclear power.

I also think he does not consistently apply his criterion of viability of not requiring any new technology. I agree that we should not count on any technological breakthroughs, like fusion reactors. But I do think we can count of incremental advances that are already in the pipeline. This should apply equally to nuclear as to battery and solar technology.

I do agree with the bottom line conclusion of all the authors that we need to have a healthy evidence-based debate about how to move forward. We cannot make plans without a detailed analysis of technological feasibility and economic and political viability.

We need to chart a course forward that will get us to a sustainable minimal carbon energy infrastructure as soon as possible and in the most cost-effective way.

But at this time I do not think there is on clear option, because every options has serious limitations that will require some technological advances and significant upgrades to our infrastructure.

I think we still need to explore all our options. Clearly we will benefit from continued incremental advances in solar, wind, and battery technology. But I also think there is tremendous potential for advances in nuclear technology, and that we should not ignore this option.

We need to explore all our grid storage options, and will likely need a system that uses many components, optimized to location and other considerations.

The good news is that I think we will get there. The economics is on the side of renewables, and that will ultimately drive the development. The big variable right now is time – how much carbon will we release and with what consequences before we move to mostly low-carbon energy?

This is where political will comes into play. And here, I think all we may need is to properly consider the externalized costs of fossil fuel. If fossil fuel use has to pay for the health and environmental effects, all other forms of energy become a no-brainer.