The analysis is pretty comprehensive and covers a wide range of options. The options that produce the highest reliability have excess generation of 1.5X to 3X, have 12 hours of storage and cover continent wide geographical areas. No area achieves 100% reliability though reliability in the high 90% range is achievable for all geographies. This still leaves some long duration outages everywhere.
This analysis can be regarded as optimistic as it only covers 39 years of data. A simple analysis of California shows that there are very bad events that only occur once in 100 years or more. It also assumes perfect long distance transmission and a control system that always connects available supply with demand. The article discusses this and assumes some backup from non intermittent sources like geothermal, fuel synthesis, hydro etc. will be necessary.
Say the shortfall is 1%. That does not mean that the backup generation capacity is 1% of generation capacity. It means that backup generation capacity approaching 100% of capacity is necessary for 1% of the time. So along with a very expensive wind and solar based electricity generation system, a large and expensive backup generation system is needed as well.
This analysis shows that the true cost of using intermittent energy sources is not the direct cost of generation but the costs of trying to make them reliable by mitigating the effects of long duration intermittency. Stratosolar's big benefit is it has NO long duration intermittency and so does not have to incur the costs of excess generation capacity or long distance transmission that far exceed the costs of generation alone.
Combined with Stratosolar’s 3X capacity factor advantage, the absence of these extra costs mean that Stratosolar's overall cost advantage over ground intermittent wind and solar is in the region of 5X to 10X cheaper. This means that synthetic fuels made using Stratosolar electricity will be 5X to 10X cheaper and provide an affordable source of seasonal storage and transportation fuels.
Hopefully analysis like that from this paper will bring some sanity to the 100% renewables debate and open up discussion of alternatives that can achieve the reliability of power generation that is essential to modern economies.
By Edmund Kelly