Harmonic Adsorption Recuperative Power (HARP)

Battelle Number: 30978-E | N/A

Technology Overview

Primary energy production and use in the U.S. ultimately results in rejection to the environment of approximately 59 quads of low- or mid-grade heat—the energy equivalent of more than 10 billion barrels of oil. Underutilized low-grade geothermal resources are estimated to potentially supply another 100 GWth or enough to power up to 20 trillion LED lights. What if even a fraction of these heat resources could be used to provide power, economically? Unfortunately, these energy resources have traditionally been expensive to exploit, and current approaches cannot produce energy under certain conditions, such as high ambient temperatures.

The Harmonic Adsorption Recuperative Power (HARP) system, developed by researchers at Pacific Northwest National Laboratory, makes power generation from these vast resources economical and practical. Conventional systems transfer heat to a working fluid until it vaporizes at a constant pressure. The high-pressure vapor is passed through a turbine, or other engine, that produces electricity. The vapor is then condensed back to a liquid and recycled using an electric-powered pump. The HARP cycle scraps all those components and substitutes a patented, multi-bed heat engine and a specially formulated metal organic framework (MOF) sorbent to drive the engine.

In the HARP system, the working fluid vapor is adsorbed into the nanostructured pores of the MOF sorbent, resulting in near-liquid-phase density. This working fluid remains in a vapor state the entire time; the only difference is that the working fluid vapor attaches, detaches, and reattaches into the MOF pores. A set of four heat exchangers packed with the MOF work in tandem, adsorbing and desorbing the working fluid in a “harmonic” cycle that swings the pressure and temperature every one to two minutes. The multi-bed heat exchanger system thus becomes a thermal compressor that powers the HARP system.

The system generates power 40 percent more efficiently than standard systems at lower cost, typically below 5 cents per kilowatt-hour versus 15 to 20 cents for traditional systems—resulting in a 75 percent cost savings. A 10-kW unit—big enough to power about eight average U.S. households—can be paired with many different sources of low-grade heat, including waste heat from diesel generators, solar arrays, produced water at oil and gas sites, or shallow-depth geothermal sites. Scaling up to 1 MW or even larger systems is straightforward as a result of the simple design of the thermal compressor components, which are readily manufacturable at scale. 


HARP has the potential to transform power production from low-grade heat sources that are uneconomic to exploit today. No heat is “waste heat” with the HARP system. It is especially suited to reduce fuel consumption for power generation on ships, at military bases, and in remote communities that use diesel generators to produce power. These applications require a power-generation system with minimum size, weight, and cost, which is exactly what the HARP system can deliver.


  • Provides 40 percent greater efficiency than traditional systems, making exploitation of waste heat practical and economical
  • Lowers cost per kilowatt-hour by as much as 75 percent
  • Can be used in situations where size, weight, and cost are at a premium
  • Requires no cooling water to operate a condenser
  • Can be configured to work as a chiller in periods where power is not needed


Available for licensing in some fields


power generation, renewable energy, geothermal energy, diesel generators, waste heat, metal organic framework, MOF, HARP, harmonic adsorption recuperative power



Market Sectors

Energy Production and Efficiency