Low-temperature heat is a widely encountered source of energy that is currently used little. Absorption cycles are uniquely capable of upgrading low-temperature heat to useful form (refrigeration or power) at high efficiency and low cost. A new dual-function ammonia-water absorption cycle is being developed that accepts heat in the range of 120°C to 300°C to produce power, refrigeration, and/or air conditioning in interchangeable amounts, depending on user needs.

The cycle builds upon 100+ years of absorption cycle developments and particularly upon 20 years of development of the advanced generator absorber heat exchange (GAX) cycle. The high efficiency is due to the close temperature match between the cycle heat acceptance and the source heat availability. Compared to other recently developed ammonia-water cycles, this cycle can achieve larger temperature glides, which significantly increases the overall energy conversion efficiency. Closer approach temperatures are achieved in simpler hardware without using risky components such as total evaporators. Compact equipment, avoidance of vacuum, and favorable transport properties yield attractive economics in many applications.

This paper presents a description of the dual-function absorption cycle. General background is presented on absorption power cycles, including a comparison to better known power cycles. Several advantageous applications of the dual-function cycle are outlined, including turbine-inlet-cooling plus power in distributed generation, solar or geothermal heated applications, and process-cooling plus power in indus¬trial applications. The absorption cycle can be directly integrated with industrial process streams or with prime movers such as turbines, fuel cells, and reciprocating engines. The mix of power and refrigeration is easily adjusted to meet seasonal requirements for cooling or power.

Units: SI