Energy Reuse by Matching Hot and Cold Streams in Advanced Life Support Systems

Reduction in power requirements for long-term space travel remains a critical technological challenge, since power provision for an advanced life support system determines a significant portion of the system's equivalent system mass (ESM). Optimization of individual processors alone is not sufficient to minimize power needs; system studies must be performed in order to maximize power savings. It is important to develop system designs that are more efficiently integrated from an energy standpoint, so that the equivalent system mass of future life support systems can be reduced. In a procedure referred to as the ‘pinch technique’, hot and cold streams within the system are matched and their energy exchanged in order to lower the external cooling and heating requirements.

This paper describes an investigation of power savings by application of the pinch technique to a closed life support system under steady-state conditions. The example system is a candidate design for the Johnson Space Center Advanced Life Support (ALS) Bioregenerative Planetary Life Support Systems Test Complex (BIO-Plex). The assumed design has partial food production using a biomass production chamber and treatment of 25% of solid wastes. First, steady state flowrates for the example system are determined. Next, the enthalpy loads associated with streams that require heating or cooling are calculated, and a heat cascade is performed to determine the minimum amounts of external heating and cooling required for the system. Then, a network representation of heat exchange equipment layout is developed. Next, savings for power and cooling are estimated. Lastly, recommendations are made on system designs that incorporate energy reuse, and plans for future applications of the pinch technique to dynamic systems are discussed.