Gestão de energia: 2010/2011

Transcription

1 Gestão de energia: 2010/2011 Class # T11 Energy in Buildings Á Prof. Miguel Águas miguel.aguas@ist.utl.pt

2 There are many ways to reduce energy consumption in buildings Reduce the Increase the Reduce demand efficiency losses Passive actions Active actions Controle actions Thermal insulation Efficient ce tequp equipment, e Shading or sun heating like lamps, air Thermal inercia conditioning, etc Natural ventilation Solar thermal Natural light Photovoltaics Biomass Cogeration Environment and energy awareness Metering Controle systems Tariff management Class # T11: Energy in buildings Slide 2 of 53

3 Thermal comfort Standart ISO 7730: States that thermal comfort is achieved when less than 10% of occupants are uncomfortable, relating thermal comfort with energy balance. To ensure thermal comfort, there must be balance between the heat produced by the body and heat lost from the body. Class # T11: Energy in buildings Slide 3 of 53

4 Thermal comfort depends on individual factors: Activity Clothing and environmental factors: Air temperature Relative humidity Air speed Wall temperature Gestão de Energia Thermal comfort Class # T11: Energy in buildings Slide 4 of 53

5 It is based on the equation of thermal comfort Gestão de Energia Thermal comfort Accumulation of heat S = Metabolism and work M-W Diffusion )} -{3.05e-3*( (M-W)-p vap Transpiration -{0.42*((M-W)-58.15)} Breathing - latent )} -{1.7e-5 7e5*M(5867- p vap Breathing - sensible Radiation Convection )} -{0.0014*M(34- T ar { )} -{3.96e-8* f vest ((T vest +273) 4 -(T rad +273) 4 )} -{f vest t*h*(t h(t vest -T ar Class # T11: Energy in buildings Slide 5 of 53

6 Thermal comfort Problem: cost of equipment for control of environmental factors and the current inability to control individual factors. Comfort is in practice: Keep the air temperature between 20 and 25 degrees C. and when there is humidity control: Maintain relative humidity between 40 and 60%. This combination of comfort to the psychrometric properties of air is the basis of most HVAC systems. Class # T11: Energy in buildings Slide 6 of 53

7 Solar radiation Extra-atmospheric radiation (average): Solar constant (S 0 ) = 1353 W/m 2 Translational motion implies an elliptical variation of ± 3%: n 10 S S cos 2 (n is calendar day) 365 But the main effect comes from the angle of declination: Gestão de Energia Climate Class # T11: Energy in buildings Slide 7 of 53

8 Climate Solar radiation The sun's apparent motion is described by the angles: azimuth elevation Class # T11: Energy in buildings Slide 8 of 53

9 Climate Solar radiation Values: W/m RADIAÇÃO SOLAR - LISBOA Julho/1989 Global l -Dia 15 Global Mês Difusa -Dia 15 Difusa -Mês Horas do dia Radiação Solar Global - LISBOA kwh/m mês European Commission: PVGIS Solar Irradiance Data 0 jan fev mar abr mai jun jul ago set out nov dez Class # T11: Energy in buildings Slide 9 of 53

10 Climate Outdoor project temperature Objective: Design of equipment The outside project temperature is calculated on a cumulative probability bilit of occurrence of 99%, 97.5%, 95% and 90%. A cumulative probability of occurrence of 99% means that in summer the temperature indicated is exceeded only in probabilistic terms, 1% of the time, ie, 30 hours per year. Lisbon (Summer) Probabilidade Acumulada de Ocorrência Temperatura de Projecto (ºC) 90% 27 95% % % 33.3 Class # T11: Energy in buildings Slide 10 of 53

11 Climate Degree-days Objective: Estimate of annual consumption The Degree-days is calculated by: Where: GD annual Heating days i 1 GD i where GD Tb is the desired indoor temperature Tj is the temperature outside the hours j i 24 j 1;se T b T j T b T j 24 The Degree-days are calculated for an entire yearonde: For example, to Lisbon, for Tb = 20 º C, heating degree days are 1190 º C.day. Knowing the heating season is 6 months (180 days), the average daily GD (GDI) will be 6.6 º C. Class # T11: Energy in buildings Slide 11 of 53

12 HVAC project Methodology Project of Calculation l of Sistem of architecture thermal loads HVAC Thermal insulation Facades orientation Grazed surfaces Activ systems Thermal inercia Fresh air Comfort Occupancy Lighting and equipment Sanitary hot water Heating power Cooling power BMS Distribution System Terminal units Maintenance Manual Class # T11: Energy in buildings Slide 12 of 53

13 HVAC project Production of cold The most common equipment for the production of cold is the chiller, which consumes electricity and has COP = 3 to 5. It is a cycle refrigerator, which a cooling water flow on evaporator 10 C to 7 º C. The heat is dissipated in the condenser directly (aerocondensadores) or cooling tower (Water loop) Alternatively ti l there is the absorption chiller, which h uses heat and has a COP = 0.6 to 1.0 It applies in situations availability of heat (eg CHP). Class # T11: Energy in buildings Slide 13 of 53

14 HVAC project Cold storage It aims to take advantage of the electricity is cheaper at night The storage systems are generally of ice shelves, based on the significant enthalpy of freezing water, 333 kj / kg, which adds about 40 kj / kg, ranging from 10 º C temperature. Overnight the chiller charges the bank. During the day the bank building gets cold, with the chiller off. Energetically, the accumulation: Loses because it requires a lower temperature because of evaporation instead of a cool water flow to 7 º C, water has to freeze the bank and because there are heat gains through the surface. Wins because the chiller working at night requires a lower condensing temperature Class # T11: Energy in buildings Slide 14 of 53

15 HVAC project Heat production The most common equipment for the production of heat is the hot water boiler The boiler burns usually natural gas revenues the order of 90% to 95%. The water is heated in the boiler 60 Cto80ºC. Alternatively, heat can be produced by a heat pump, but only when water temperatures are lower. Class # T11: Energy in buildings Slide 15 of 53

16 HVAC project Distribution Systems The most common HVAC system basing on a network of four pipes (flow and return water flow and return hot and cold water) and air handling units, UTA. The UTA draws air from the air conditioned space, mixing it with air again. This mixture is filtered, cooled (heated and/or humidified) and blown into space. Excess air (vacuum lower than inflation) pressurizes the space air out through openings in doors. AR NOVO AR RECIRCULADO Filtro CHILLER Bateria arrefecimento ÁGUA GELADA A ÁGUA QUENTE Bateria aquecimento Chuveiros CALDEIRA Alternatively, cooling can be done by floor / ceiling radiant. Ventilador AR INSUFLADO ÁGUA Class # T11: Energy in buildings Slide 16 of 53

17 HVAC project Distribution systems (dedicated UTA) Class # T11: Energy in buildings Slide 17 of 53

18 Distribution Systems (UTA climaxes incorrectly 2 spaces) Class # T11: Energy in buildings Slide 18 of 53