AirJoule: Metal Organic Framework HVAC breakthrough?

Montana Technologies is developing AirJoule, an HVAC technology that uses metal organic frameworks, to lower the energy costs of air conditioning by 50-75%. The company is going public via SPAC and targeting first revenues in 2024. Our AirJoule technology review finds strong rationale for next-gen sorbents in cooling, good details in Montana’s patents, and challenges that decision-makers may wish to explore further.

The global HVAC market is worth $355bn per year, as air conditioning consumes 2,000 TWH per year, or 7% of all global electricity (note here).

Each one of the world’s 1.7bn vehicles also has an in-built air conditioner, and in hot/congested conditions, the AC can sap 70% of the range of an electric vehicle.

Typical air conditioners have a coefficient of performance (COP) of 2.5-3.5x, which means that each kWh of electricity inputs will deliver 2.5-3.5 kWh-th of cooling energy.

Cooling energy, in turn, is used to reject heat from air (about one-third of the total) and to reject heat from the inevitable condensation of water, as air cools down (about two-third of the total). To re-iterate: (a) cooler air can hold less water; (b) hence some water will condense as air is cooled; (c) condensation of water releases energy (called the latent heat of vaporization, and running at 41 kJ/mol, or 640 Wh/liter); and (d) this adds to the cooling load that the air conditioner needs to provide; (e) by a factor of 1-2x more than the cooling load needed to cool down the air in the first place (called the specific heat of air, or 1.0 kJ/kg-K). For more details, please see our overview of air conditioning energy demand.

Metal Organic Frameworks are a type of sorbent with a high surface area, able to adsorb water from air. To re-release that water, a vacuum pump can be used to lower the pressure (chart below). Effectively this is a swing adsorption process rather than a cryogenic process.

How does AirJoule technology work? This data-file pieces together details from Montana’s disclosures and patent filings. In particular, the work covers five core patents describing a Latent Energy Harvesting System, using Metal Organic Frameworks to adsorb and re-vaporize atmospheric water; test stable MOFs, and novel methods for manufacturing those MOFs.

What COP for AirJoule? After reflecting the loads of the vacuum pump, other fans and blowers, heat transfer from an adsorption chamber to a desorbtion chamber, and auxiliary loads, AirJoule is targeting a total electricity use of 60-90 Wh/liter of water. Hence if water is adsorbed, then desorbed, then misted, it will absorb 640Wh/liter as it re-vaporizes (see above). Divide 640Wh/liter by 60-90Wh/liter, and you derive a coefficient of performance of 7-10x. Or in other words, the energy consumption will be 50-75% below a typical air conditioner. More details are in the data-file.

What are the key challenges for AirJoule technology? We see five thematic challenges for using MOFs and sorbents in cooling systems, and two specific challenges based on reviewing Montana’s patents.

Overall, we think there is very strong potential for next-gen sorbents, and metal organic frameworks, across cooling and other industrial processes, as described in our recent research note here. Key conclusions into Montana’s technology are in our AirJoule technology review below.

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