Passive Environmental Control. Passive Environmental Control Systems. Passive Environmental control. Cooling by evaporation

Transcript

1 Passive Environmental Control Passive Environmental Control Systems Comfort is connected to flollowing environmental variables Air temperature Mean radiant temperature Air relative humidity Air velocity Environmental control actions: Use of ventilation Direct and indirect evaporation Use of building mass Use of solar radiation Shading Envelope action Passive Environmental control At different times along the year can work different strategies. to reduce costs you will have to choose one or two techniques compatible each other and integrate them into the design of the building Suggestions from the bioclimatic diagram refers to residential buildings with limitated internal loads. Cooling by evaporation

2 Cooling by evaporation Cooling by evaporation Cooling with indirect evaporation Cooling by evaporation Cooling by evaporation B. Grimshaw UK Pavillion Expo Seville 92 Cooling by direct evaporation

3 Cooling by evaporation Cooling by evaporation: tradition Mashrabìya Egypt Zion Park Visitors Center Utah USA Malqaf Egypt Salsabìl, la Zisa Palermo Cooling by evaporation The water to evaporate has to receive energy (latent heat of evaporation of about 2500 kj / kg). Evaporation extract energy from air % % Enthalpy, 40% Btu/lb dry air 35 Aria in uscita % 25 RH Aria in 15 entrata Dry bulb temperature, F 55 Cooling by direct evaporation 60 Hu m idity ra tio, lb w a te r p er lb dry a ir The more air is dry the more works the cooling Dump thermal variation with the mass

4 Thermal Mass Thermal Mass attenuazione ritardo Thermal Mass Thermal Mass Mesa Verde - Colorado Mat-mata - Tunisia

5 Themal mass Thermal Mass Cooling by ventilation Cooling by ventilation

6 Cooling by ventilation Cooling by ventilation of mass ANTILLE Academy, C. Hauvette & J. Nouel MARTINIQUE EASTGATE BUILDING, Pierce, Arup ZIMBABWE Cooling by ventilation of mass Natural ventilation and comfort Does Natural ventilation work? Thermal loads amount is foundamental

7 Solar radiation Direct gain Solar radiation captation Energy storage Solar radiation Solar radiation Direct gains Isolated gain: greenhouse

8 Solar radiation Indirect gain: Trombe Wall Shading and Shadow Shading Solar shading tipology A seconda dell ora, del luogo e del periodo il sole si trova in posizione diverse. Schermature orizzontali sul fronte sud, schermature verticali sui fronti est e ovest

9 Solar shading tipology: shading coefficient Cool surfaces Surfaces energy budget Emissivity, absorption, reflection r shortwaves Ideal heatsink ε l =1 r c =0 The quantities playing a role: Absorption coefficient, α r long waves emissivity, ε ε long waves Convection coefficient, h conductivity, λ density, ρ Specific heat, c porosity, φ A shortwaves Ideal absorber ε l =0 a c =0

10 Surfaces characteristics White envelope Commercial building at Davis - California Proposed by LEED - GBC Green envelope Green envelope azione su radiazione solare - ombreggiatura azione su emissione radiativa azione su moti aria barriera antivento evapotraspirazione calore latente di vaporizzazione azione su deposizione secca di inquinanti e PM10 azione di cattura CO 2 azione di emissione O 2 azione di protezione acustica azione psicologica The quantities playing a role: Absorption coefficient, α emissivity, ε Evaporation and transpiration by plant and soil

11 Evapo-transpiration Evapo-transpiration 100% 43% Evapotraspirazione + Fotosintesi 15% Riflessione 70% Assorbimento 40% Convezione 17% Radiazione 15% Trasmissione Superficie evaporazione riscaldamento dell aria Foresta di abeti 66,5 % 33,4 % Foresta di pini 64,8 % 33,8 % Querceto 70,0 % 30,0 % Faggeta 83,8 % 14,6 % Prato 78,8 % 16,2 % Città (calcolato) 15,0 % 60,0 % Una consistente percentuale dell energia solare incidente viene utilizzata nell evapotraspirazione e non rilasciata all aria Green walls Green roof

12 Green surroundings