Air Management Engineering for a Greenhouse Module for Space System Erik Mazzoleni Lorenzo Bucchieri Bioregenerative Live Support ISLSWG Workshop Turin,

This project has been developed in close collaboration with the German Aerospace Center DLR (project coordinator) and it is embedded in the MELiSSA framework of ESA research projects. 2 Greenhouse Module for Space System (GMSS) Enginsoft has participated as partner/coordinator in the following ESA research project:  ALISSE: Advanced Life Support System Evaluator  SCALISS: SCAling of LIfe Support System  FC1: Food Characterization Phase 1  HYSSE - FC2: HYdroponic SubSystem Engineering - Food Characterization Phase 2 GMSS: Project partners GMSS: Project logoGMSS: a MELiSSA project

This projects is a feasibility study to develop a greenhouse module for a lunar base. 3 GMSS - Project description Global Objectives: 1.Structure and design of Greenhouse Module layout (e.g. primary & secondary structure, mechanisms, subsystem accommodation, piping, cabling) 2.Design of interface of Greenhouse Module with habitat 3.Budgets on subsystem detail, mainly power, mass, thermal, dimensions and equipment lists for each domain 4.Determination of optimal plant accommodation strategies w.r.t. handling, safety and optimal growth 5.Investigation of human interaction with systems and set-up of process procedures and operation tasks of humans e.g. harvest, maintenance (crew time estimations) 6.Detection of knowledge gaps w.r.t. cultivation technologies and processes Study domains: Systems Engineering Air Management System Plant Health Monitoring & Quality Assurance Nutrient Delivery System Illumination System Design/ Structure Human Factors (crew) Horticulture Expert Thermal/ Power Control System Greenhouse module system borders First concept of a greenhouse on the moon

Air Management System has to create adequate climate conditions for the plant wellness and to allow their growth inside the Greenhouse module. 4 Objectives: 1.Define the flow path to distribute the «fresh» air and collect the «waste» air inside the greenhouse 2.Select and characterize the necessary components for air treatment and recirculation 3.Define function modes to control the air composition (concentration of O2 and CO2) 4.Check the efficiency of the system from a fluid dynamic point of view Air Management System: objectives AIR TRANSPORTATION (ducts, dampers, actuators) CONTROL AIR CHARACTERISTICS (Manipulate velocity, pressure, temperature, presence of contaminants) INTERFACE WITH HABITAT (provide O2 to habitat and receive CO2 from habitat) ADEQUATE CLIMATE CONDITIONS (local distribution of velocity and temperature) Functional requirements :

The Greenhouse is composed by four growth chambers (called “petals”) and one central core 5 Internal layout External layout Greenhouse module layout 5

 Each crop requires a proper environment (nutrient, light and air condition) that is usually different from the other plant needs. For this reason each petal is a growth chamber with a specific climate and with the cultivation of a single crop Single petal internal layout Growth chamber The petal: one climate 6

7 Definition of components to satisfy the following requirements:  Control pressure, temperature and air composition (concentration of O2, CO2 and humidity)  Recover water through condensation of moisture  Air cleaning from chemical and biological contaminants List of components: Fans, UV sterilizer, Trace gas filter, cooling coil, heater, sensor packages, humidifier, CO2 /Air injection system and particle filter. Position of components Scheme of flow path List of components for each petal

8 Each component is selected from industrial producers: mass, maximum energy demand and technical capabilities are taken into account. Axial fans Selection of the components Air control valves (dampers and actuators) Rigid and inflatable ducts Particle filter Rigid ducts: Mass =1350[kg]; Inflatable ducts: Mass=385[kg] Particle filter: Mass =3.4[kg] Axial fan: Mass =39[kg], Power demand=2.7kW]; Mass flow range=2.0[m^3/s]-4.2[m^3/s] Damper: Mass =11[kg]; Actuator: Mass=1[kg]

Habitat interface: Function Modes for O2/CO2 exchange A direct gas exchange (O2 and CO2) with the habitat has been selected, using the following function modes:  NOMINAL MODE. In this mode the air is recirculated in a continuous loop. Air is treated but there is no connection with the habitat.  BREATHING MODE. In this mode each petal is directly connected to the habitat infrastructure. O2-rich air is provided to the habitats form the growth chamber and CO2-rich air is received in the opposite direction. 9

 The air is treated and then is blown down under the petal floor. The air inside the (inflatable) plenum is pressurized by the fans that are located just before the plenum entrance.  Moreover the top surface of the plenum is perforated (grid) with circular holes and the air is distributed inside the petal. Then the air is collected at the top part of the petal through a suction duct. 3D model of Air management systemSingle petal internal layout Petal Core Air transportation: ducts, plenum and grids Petal 10

CFD analyses: model and physical hypotheses A CFD model of a growth chamber has been created to check internal climate of the petals: these simulations has allowed to calculate pressure, velocity, temperature, local concentration of O2/CO2 and humidity level. CFD model of a growth chamber Hypotheses:  Plants are at their max level of growth (max O2 emission, CO2 consumption and max occupied space)  Max Heat load inside the chamber (all led lamps are on)  Steady state simulations Two petals simulated:  Petal A  Crop=Potato  Heat load from LED panel=53037[W]  Petal B  Crop=Bread wheat  Heat load from LED panel=116993[W] Two Inlets: Total mass flow = 8200[m 3 /h] Temperature =20[°C] Outlet: Relative Pressure = 0[Pa] Trays Boxes that represents plants LED panels 11

Results: Velocity contours (Petal A and B) The velocity distribution remains below 1[m/s] in correspondence with the plants: a low velocity is necessary to not stress the plants. Petal A: plane 1 Plane 1 Plane 2 Petal A: plane 2 Petal B: plane 1 Petal B: plane 2 12

Results: Temperature contours (Petal A and B) A particular attention has been paid to the temperature distribution which is the most critical aspect to guarantee adequate living conditions for plants. In petal B high temperatures (over 35[°C]) have been reached due to an high heat load. Petal A: plane 1 Plane 1 Plane 2 Petal A: plane 2 Petal B: plane 1 Petal B: plane 2 T>35[°C] 13

Results: Temperature contours (Petal B and B-mitigated) To decrease the temperature gradient in Petal B the following mitigating strategies could be applied:  Reduction of inlet temperature (from 20[°C] to 16[°C])  Increase inlet mass flow using the auxiliary fans (from 8200 [m^3/h] to 16400[m^3/h]) Petal B: plane 1 Plane 1 Plane 2 Petal B: plane 2 Petal B-mitigated: plane 1 Petal B-mitigated: plane 2 14

Conclusions  In this project a greenhouse module layout has been developed, defining all the necessary subsystem for the plants growth.  In particular, the air management system has been designed with the selection and characterization of components to control the climatic condition inside each growth chamber.  A direct habitat interface has been defined for O2/CO2 exchange: a switch between two operating modes of the air system can adjust the O2/CO2 levels.  With a final CFD analysis the local distribution of velocity and temperature is verified. A mitigating strategy has also been proposed in case of high temperatures. 15

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