PRANA — A Layered Framework for Sustainable AI Compute
Position paper · July 2026 · 5 pages · 24 references
The whole paper turns on one reframe: computation does not consume energy, it relocates and degrades it. A data centre turns almost all of its input electricity into low-grade heat, and the water use is a design choice — evaporative cooling — not a requirement of computing. So the problem is not consumption. It is exergy misplacement: we generate heat where it has no value, destroy it at the cost of water and capital, and burn gas somewhere else to make the identical heat.
- PPhysics-aligned hardware
Lowest joules per operation at each tier — photonic and analog in-memory accelerators, liquid cooling as the default rather than the upgrade.
- RRight-sized intelligence
Route every query to the smallest model that clears its quality bar. Distillation, quantisation, sparsity, cascades.
- AAdaptive scheduling
Most of the fleet is deferrable in time and movable in space. Schedule it against grid carbon, regional water stress, and demand for the exhaust heat.
- NNegative-waste symbiosis
Plumb the building so its rejected heat has a customer — district heating, industrial pre-heat, greenhouses. Turn a compliance number into a revenue line.
- AAccountability metrics
Retire PUE. Measure energy-reuse-per-token: the fraction of the energy behind each token that went on to serve a second human purpose.
Follow-the-Cold routing
The inversion of follow-the-sun. Heating demand is one of the most predictable loads on Earth and it is hemispherically anti-correlated — January in Finland is July in Chile. So move deferrable work toward wherever its waste heat currently displaces a fossil boiler. The round trip costs 100–200ms, which a batch job does not notice. The carbon credit then includes the boilers you switched off, which no existing scheduler models.
The Compute Boiler
A 1–50 MW facility sitting inside a district-heating network. It draws power when renewables are over-supplying, does deferrable AI work, banks the resulting 55–65 °C heat in cheap water tanks, and releases it on the evening demand peak. One asset sells three products — grid flexibility, heat, and computation — against a single energy purchase.
I argued against myself in section 3.2, because Jevons' paradox is the obvious objection and it deserves an answer rather than a silence: efficiency alone slows the demand curve without bending it down. I also killed orbital compute as a 2026 strategy in 3.4, despite it being the most exciting option in the paper, because the launch economics do not work until roughly 2035. And I said plainly in the limitations that both proposals are architectures with plausibility arguments behind them, not measured deployments.
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- PRANA-Sustainable-AIThe full paper, with all 24 references and the limitations section.

