Integration of controlled ecological life support system

Cheng-Hsiung Lin, Purdue University

Abstract

A novel methodology that enables a sequential modular steady state simulator, ASPEN PLUS, to perform dynamic simulation was investigated. This methodology was successfully applied to the dynamic integration of a Controlled Ecological Life Support System (CELSS), which is an integration of biological and physicochemical subsystems, to produce nutritionally balanced food, potable water, and breathable atmosphere from metabolic and other wastes. The major difficulties to achieve the dynamic expansion of a sequential modular steady state simulator involved how to set up communication among the different modules such that the interconnected variables of the flowsheet were adequately represented. Four supervisory modules were designed to solve the communications among different modules. A coordinating module was developed for the initialization of the flowsheet. For pseudo-steady state subsystem, a "front" monitoring module to incorporate the dynamic inputs from upstream modules and a "rear" monitoring module to generate dynamic outputs to downstream modules were created. A recycling module was also developed to ensure that the time proceeds. Furthermore, piecewise polynomials with the user-supplied basis functions were introduced to represent the interconnected variables. An equation-oriented dynamic simulator, SPEEDUP, was introduced to the dynamic integration of a CELSS. The verification of the methodology developed was conducted by using SPEEDUP. In the integration of CELSS, a diet model was developed to investigate human nutritional requirements from limited food sources and to link the Crew Chamber, the Plant Growth Chamber, and the Food Processing Subsystem. A human metabolic model was constructed as driving forces for the system integration of biological and physico-chemical subsystems. Utilization of plants for support of human life is the major characteristic of a CELSS: A specific photosynthesis model was developed to characterize the biological functions of plants, where plants utilize solar energy to produce biomass, remove carbon dioxide, generate oxygen, and transpire water from plant leaves. A closed dynamic air loop was investigated to study the dynamics of the Crew Chamber, the sensitivity of parameters, and the trade-off of technologies.

Degree

Ph.D.

Advisors

Tsao, Purdue University.

Subject Area

Chemical engineering|Environmental science|Ecology|Systems design

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