  Power consumption (supply, heat, cost) and associated carbon emissions
(environmental impact) are increasingly critical challenges in scaling
supercomputing to Exascale and beyond. We proposes to exploit stranded power,
renewable energy that has no value to the power grid, for scaling
supercomputers, Zero-Carbon Cloud (ZCCloud), and showing that stranded power
can be employed effectively to expand computing [1]. We build on those results
with a new analysis of stranded power, characterizing temporal, geographic, and
interval properties. We simulate production supercomputing workloads and model
datacenter total-cost-of-ownership (TCO), assessing the costs and capabilities
of stranded-power based supercomputing. Results show that the ZCCloud approach
is cost-effective today in regions with high cost power. The ZCCloud approach
reduces TCO by 21-45%, and improves cost-effectiveness up to 34%. We study many
scenarios. With higher power price, cheaper computing hardware and higher
system power density, benefits rise to 55%, 97% and 116% respectively. Finally,
we study future extreme-scale systems, showing that beyond terascale, projected
power requirements in excess of 100MW make ZCCloud up to 45% lower cost, for a
fixed budget, increase peak PFLOPS achievable by 80%.
