Authors: Daniel Brouse and Sidd Mukherjee
Date: July 2, 2026
This is a “secret” invention Sidd and I developed some time ago.
I call it secret not because it is proprietary in the usual sense, but because we tend to apply a fairly strict internal filter before releasing anything into the wild. Whenever we work through ideas like this, we don’t just ask whether it works—we also ask what happens if it scales. What happens if everybody does it? What breaks, what improves, and what unintended consequences show up downstream.
That second question usually slows things down more than the first.
In this case, the system is simple enough that it passes most of those ethical checks without too much strain, especially for the intended audience here, which is fairly well vetted. Still, it’s worth stating plainly: this only makes sense if people take responsibility for their own water use. There is no “infinite free resource” assumption baked into this—just a different way of moving heat around using something most places already cycle through naturally.
For our evaporative cooling experiments, we didn't use potable water indiscriminately. We collected rainwater in trash cans, and everyone in the family saved the water that normally goes down the drain while waiting for their showers to warm up, along with other reusable household water. The goal was to reduce both energy use and water waste by making use of water that would otherwise have been discarded.
The motivation for sharing it is straightforward. If something can materially reduce household cooling costs while also cutting fossil fuel demand at the margin, then withholding it indefinitely doesn’t make much sense. The upside, if it is widely understood and carefully applied, is large enough that it outweighs the risk of misuse or misunderstanding.
As always, the ethics are part of the engineering.
Authors: Daniel Brouse and Sidd Mukherjee
Updated from: 2003
This paper evaluates a passive cooling strategy using evaporative water films on building surfaces. The system leverages the latent heat of vaporization of water (~2.26 MJ/kg) to remove heat from structures. Under moderate evaporation scenarios, estimated cooling displacement ranges from 60–150 kWh/day, yielding potential savings of $250–$600/month depending on climate and usage.
Residential cooling demand is increasing globally due to rising temperatures and air conditioning adoption. Typical vapor-compression systems operate at COP values of 2.5–4.0.
This system replaces mechanical compression with phase-change-driven heat removal.
The latent heat of vaporization of water is approximately:
2.26 MJ/kg (at 100°C) ~2.45 MJ/kg at ambient temperatures ~970 BTU/lb
Water density:
1 cubic foot = 62.4 lb
Energy absorbed per cubic foot:
62.4 lb × 970 BTU/lb ≈ 60,500 BTU ≈ 61,000 BTU per cubic foot evaporated
1 kWh = 3,412 BTU (thermal equivalent). With typical COP ≈ 3:
1 kWh ≈ 10,000 BTU cooling
Cooling displacement:
61,000 ÷ 10,000 = 6.1 kWh per cubic foot evaporated
Electricity price (July 2026): $0.11759/kWh
6.1 kWh × 0.11759 ≈ $0.72 per cubic foot
Result: Each cubic foot evaporated saves approximately $0.72
Assumed evaporation: 10–25 ft³/day
| Scenario | Daily Savings | Monthly Savings |
|---|---|---|
| Low (10 ft³/day) | $7.20 | $216 |
| High (25 ft³/day) | $18.00 | $540 |
This system operates as a solar-driven phase-change heat pump where the atmosphere acts as the heat sink.
| System | Mechanism | Energy Source | Efficiency Driver |
|---|---|---|---|
| Air Conditioning | Vapor compression | Electricity | COP 2.5–4 |
| Waterfall House | Phase change evaporation | Solar + ambient heat | Latent heat of vaporization |
As temperatures rise, cooling demand increases sharply. This drives a cascading set of system stresses:
This creates a reinforcing sequence:
more heat → more cooling demand → higher energy use → higher emissions → further warming → more heat
In practice, what emerges is not a single isolated feedback loop, but a coupled network of reinforcing systems—biophysical (permafrost thaw, forest stress and mortality, wildfire regimes, hydrological intensification) and socioeconomic (energy demand, infrastructure constraints, and grid response). These systems can interact nonlinearly, particularly under sustained warming and extreme heat conditions.
The key point is that these feedbacks are already operating, but their magnitude, interaction strength, and long-term dominance relative to human emissions vary by region, sector, and timeframe. Reducing risk ultimately depends on rapidly reducing greenhouse gas emissions, especially from fossil fuel combustion, while adapting infrastructure to rising heat extremes.
* Our probabilistic, ensemble-based climate model — which incorporates complex socio-economic and ecological feedback loops within a dynamic, nonlinear system — projects that global temperatures are becoming unsustainable this century. This far exceeds earlier estimates of a 4°C rise over the next thousand years, highlighting a dramatic acceleration in global warming. We are now entering a phase of compound, cascading collapse, where climate, ecological, and societal systems destabilize through interlinked, self-reinforcing feedback loops.
We examine how human activities — such as deforestation, fossil fuel combustion, mass consumption, industrial agriculture, and land development — interact with ecological processes like thermal energy redistribution, carbon cycling, hydrological flow, biodiversity loss, and the spread of disease vectors. These interactions do not follow linear cause-and-effect patterns. Instead, they form complex, self-reinforcing feedback loops that can trigger rapid, system-wide transformations — often abruptly and without warning. Grasping these dynamics is crucial for accurately assessing global risks and developing effective strategies for long-term survival.