In evaluating solutions to the limits of renewables penetration, it is important to distinguish what is real from what is research. On the real side, current Wind and Solar electricity generation are mature technologies with annual investment exceeding $250B. This represents about half the world investment in new generation. Beyond investment in generation, there is also some investment in transmission to get the electricity from the remote locations where much of it is generated to where it is needed. As with all such large scale endeavors money is only invested in proven technology, low risk projects. The technologies vying for entry to the “real” proven low risk category are offshore wind and to a lesser extent Concentrated Solar Power. Its also important to understand that current wind and solar deployment rely almost completely on fossil fuel backup generation.

Technologies that are in development and not being deployed include the following:

1. most energy storage (except for pumped hydro),
2. generation of hydrogen from electrolysis
3. redundant long distance transmission within the current grid to enable transfer of intermittent power across regions,
4. control systems that monitor and control the long distance distribution of intermittent energy across large regions

Up until recently, as Wind and Solar have grown, the existing grid could adapt to their relatively small contribution. In a few markets limits are now appearing and additional infrastructure has to be contemplated. This NREL study is an attempt to forecast how the combined grids of the US east coast could achieve 30% renewables penetration by 2026. This article is a review of the report. The report is based on sophisticated modelling on a supercomputer of projected grid changes. These include growth in wind and solar in specific locations, growth in transmission and a monitoring and control system that manages balancing variable supply with variable demand. The study highlights the complexity of what seems a modest goal with limited technological changes. Fossil fuels and nuclear are still the dominant generation technologies. The model is limited. It is based on one year and does not cover worst case events. Implementing the monitoring and control aspect of the model would be technically difficult and politically really difficult. The goal is still only a modest 30% penetration.

So getting back to the theme of limits to renewables penetration, its clear that only as the problem is becoming real, is there some focus on how the problem can be solved.  We are in the very early stages of recognizing the problem. This NREL study and the more academic and theoretical Solutions Project highlight how a centralized monitoring and control system is an essential part of a solution. This, in many ways would seem a bigger problem than developing and deploying energy storage, in large part because there is a big political problem as well as a big technical problem.

The NREL study only contemplates 30% penetration and relies on significant new technology not yet developed. The solutions project relies on even more technology not yet developed and is a more simplistic model that does not model an actual interconnect. These studies at least are starting to outline the problem as opposed to ignoring it as has been the attitude so far.

As I have previously maintained, the problems with renewables penetration need to be accepted before alternative solutions are evaluated. At this stage all the technologies being investigated or developed are very far from significant deployment. When viewed from this perspective, StratoSolar is no farther from deployment and no more speculative than the technologies being contemplated by these investigations. StratoSolar specifically addresses the daytime intermittency, nighttime storage, long distance transmission and cost of generation that will limit the future penetration of current PV solar and wind generation. Its cost of development is low. The timeframe to deployment if proven is long before 2026.
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By Edmund Kelly
 

Gail Tverberg wrote a recent article titled “Intermittent renewables can’t favorably transform grid electricity”. It’s a good in depth article with lots of solid data and references to back up her arguments. It is a far more comprehensive analysis than my recent posts on the topic. 

The solutions to this problem all involve adding substantial energy storage and additional long distance transmission and distribution along with grid demand response changes. The combined cost of this additional (yet to be developed) infrastructure far exceeds the cost of the wind and solar generation which is already very high.  

​This paper from Mark Jacobson et al. is a very comprehensive and imaginative analysis that shows how it might be done by 2050 within known technological constraints. It draws on deploying a wide range of new technologies and avoids reliance on battery storage. Instead it relies on energy users storing heat and cold and the generation of hydrogen from electrolysis for transportation fuel. It makes extensive use of technologies that have proven difficult and expensive, like Concentrated Solar Power with thermal storage and offshore wind power. Given the long periods that wind and solar can disappear the paper does not make it clear how this is covered. Also the geographic constraints of the UK or northern europe covered by David MacKays book are not addressed.

A central problem with academic solutions is they rely on government support to prop up the costs and mandate behavior. This can work up to a point as current wind, solar and nuclear can testify. On the other hand, history can also testify to the fickle nature of government support for energy. Its hard to imagine stable government support out to 2050.

This StratoSolar analysis of a 2050 energy scenario addresses the same problem. The StratoSolar solution has the benefit of not needing any changes to the grid or energy consumers. StratoSolar power
 plants include gravity energy storage and provide a drop in replacement for dispatchable electricity. The only decision is where to put them. They can be deployed to provide new capacity in the developing world or replace fossil fuel capacity in the developed world. Because they provide low cost electricity they don’t need government subsidy or mandates, just regulatory permission to exist. As StratoSolar electricity continues to fall in price, end users will adapt to consume it over other sources. Natural market forces will drive the adoption of the scenario. This has great advantages as it works worldwide without global political agreement.
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By Edmund Kelly