The surprising need to explain StratoSolar's higher utilization %

By Edmund Kelly

Recently we got some surprising feedback. The opinion voiced was that StratoSolar could not achieve a lower Levelized Cost of Electricity (LCOE)  than ground based PV. We got no detail on what drove that opinion, but it was from an important source. In some ways this represents an advance on simple disbelief. If it were expanded upon, the opinion may have been more like; "even if the concept were practical, you cannot produce lower cost electricity". Given that the case for StratoSolar fundamentally rests on producing lower cost electricity its interesting to ask what part of the argument have we not presented clearly or lacks credibility.

LCOE is a relatively simple calculation based on a few inputs: Capital Cost ($/W), Utilization (%),  Financing cost($) and Operations & Maintenance (O&M). Comparing a ground PV array to same sized StratoSolar array, we can assume for this argument that financing and O&M costs are the same for both. This leaves $/W and utilization%. The StratoSolar argument is that it has a higher utilization based on more solar insolation and a similar or lower capital cost $/W. To say that we fundamentally cannot have a lower LCOE is to challenge these assertions.

The higher insolation claim is based on very well validated data from many sources which we describe in detail on the website. Its an externality we have no control over but we are starting to appreciate that it may not be well understood. A perspective we have heard voiced regularly  from technologists is that the Watts on the ground are 1000W/m2 and in space its 1366W/m2, so the benefit is only about a third, which is too little to be worth chasing. This perspective mistakes peak daytime irradiance for the total daily energy or insolation in kWh/m2. Energy is what matters to LCOE not peak irradiance.  It seems that the fundamental 3X utilization benefit from more sunshine at 20km altitude may be the thing we need to emphasize more as it seems it may not be well understood or accepted as valid by almost everybody.