12/21/2009 Home. Cool Home Home..Cool Home by Shirish M. Deshpande Energetic Consulting Pvt Ltd, India Shirish Deshpande Energy saved is profit earned. Energetic Consulting Pvt. Ltd., Thane Agenda Comfort : Facts Ancient Techniques Modern Solutions Case Study Way Forward 1
Sleeping over a point A couple sleeping in a bedroom at night will generate only about 300 watts of metabolic heat The heat load form will not show any other load A one- ton air conditioner removes more than 3000 watts of energy from the room Thus, in a 10 hour session, the compressor should work for a total of one hour only, and the monthly cooling energy bill should be less than Rs. 300 We know that it is much more; Why? In fact, we are paying the extra money to cool the structure, as a huge favour to our neighbours Shelter need Ever since we left the caves, buildings have been our bastions against the natural elements Every culture has evolved its architecture to suit the local environment In North America / Europe, buildings needs have to be heated to guard the occupants against the biting cold outside; thus the buildings are insulated to prevent cold drafts and heat loss In an Indian context, for more than 80% of the country, air-conditioning is cooling In Indian summers, our worry is how to keep the heat OUT Buildings are bare and have thermal mass; which adds to the cooling loads One gets less cooling at a much higher energy cost Energy is costly and unreliable 2
Comfort : Facts You feel comfortable when metabolic heat is dissipated at the same rate it is produced The human body needs to be maintained at a 36 ± 0.5 C regardless of prevailing ambient conditions Air movement is essential for comfort as it enhances heat transfer between air and the human body and accelerates cooling of the human body Air movement gives a feeling of freshness by lowering skin temperature, and the more varied the air currents in velocity and direction, the better the effect A draught is created when temperature of moving air is too low and / or the velocity is too high At comfort room temperature (23 to 26 C), acceptable air velocity range is 0.15 to 0.50 m/s The higher the space RH, the lower the amount of heat the human body will be able to transfer by means of perspiration/evaporation If indoor air temperature is high and RH is high (above 11.5 g vapour per kg dry air), the human body will feel uncomfortable Generally, RH for indoor comfort conditions should not exceed 70 % Energy Consumption in Homes 3
Typical Window Air-Conditioner Home Air-Conditioning : Issues Sleep is necessary for the body to regain the energy and in order to prepare our body for the next day, we would need lot of fresh air (Oxygen) The fresh air would bring in lot of heat and humidity; which would eventually increase load on air-conditioning system In order to control the increased loads, the window and split ACs do not have any fresh air intake, which results in bad Indoor Environmental Quality A new breed of window ACs would be required, which would allow fresh dehumidified air into the room at no extra cost 4
Ancient Methods In India thermal comfort meant avoiding heat stress Our master builders of yore evolved an elegant three pronged formula for thermal comfort: Raise barriers against sunlight Use mass to delay heat transmission Drain out the residual heat to flowing water and to the sky by radiation, mostly at night None of these processes need external energy Ancient Techniques Firstly the barriers comprised of trees, shaded verandas and carved stone screens The trees also kept the ground shaded, besides the walls They are, of course, the best air fresheners and evaporative coolers The builders of our heritage structures have used mass quite effectively The sun will take a lot longer to heat a massive heritage building wall than a thin modern building 5
Lotus Mahal at Humpi The 2 - storied Lotus Mahal which is designed in such a way; when the atmospheric temperature goes up the water in the tank starts circulating in the hollow place inside the wall keeping the Mahal cool The circulated water goes back to the overhead tank, gets cooled and starts re-circulating Our ancestors had acquired the knowledge to keep buildings thermally comfortable by using the building mass enough to absorb solar heat and place the building base in contact with a water body that would cool it by conduction and evaporation The key was to keep the structure below 34 C, the human skin temperature Radiant Cooling Another effective process used was cooling by radiation The exterior coating contained the mineral barites that contains barium sulphate which has an emissivity of 0.95 and absorptivity of 0.05 The sun occupies less than half a degree of the sky and heats for less than five hours daily and the radiant temperature of the rest of the hemisphere is minus 40 degrees during the day and still lower at nights The barite coated building would absorb only 5% of the sunlight and would radiate away 95% of heat. Thus the building remains cool without insulation or artificial cooling 6
Climate and Buildings Buildings would respond differently to the different climates Climate plays a very important role in deciding the building passive and active strategies To understand the built strategies, A simulation study was done for mainly 5 climatic zones (climate as defined in ECBC) Cities selected in the 5 different Climatic Zones and their geographical Location Climatic Zones Warm and Humid Composite Cold Temperate Hot and Dry Location Mumbai Delhi Dehradun Bangalore Ahmadabad Latitude 18º 53' N 28 4' N 30º 19' N 12 58'N 23 03' N Longitude 72º 50' E 77 2' E 77 2' E 77 38' E 72 40' E Altitude ((above MSL) 11 mts 216 mts 682 mts 921 mts 55 mts Case Study : Methodology A standard Block of 20 X 10 X 10 was considered Various design strategies like Orientation, Roof insulation, Wall insulation Window orientation and shading, Fenestration was Studied The percentage KWH increase,cost increase and payback period was compared 7
Roof To illustrate the effect of roof insulation, room with RCC roofing material was considered and this performance was compared with 1 polystyrene over deck insulation and was for 5 different climatic zones (east-west orientation) Roof Energy cost (kwh X Rs. 5) Roof Mumbai Decrease in cost on Load (Rs.) Increase in Cost (Rs.) Simple payback period (Years) Conc. Slab (kwh) 51925 0 0 0 Conc. With Insulation (KWh) 42245 9680 30000 3.10 Roof - Ahmedabad Conc. Slab (kwh) 57295 0 0 0 Conc. With Insulation (KWh) 44635 12660 30000 2.37 Roof- Delhi Conc. Slab (kwh) 51070 0 0 0 Conc. With Insulation (KWh) 39775 11295 30000 2.66 Roof - Dehradun Conc. Slab (kwh) 42065 0 0 0 Conc. With Insulation (KWh) 33365 8700 30000 3.45 Roof - Bangalore Conc. Slab (kwh) 40470 0 0 0 Conc. With Insulation (KWh) 32305 8165 30000 3.67 Conclusion: The concrete roof when added with extra 1 Polystyrene insulation it showed savings of 16 to 25% with average pay-back of 3 years 8
Walls 3 cases were compared - 9 thick brick wall, Brick wall with 1 polystyrene insulation and Solid concrete block wall Fenestration An opening of 9 6 X 5 9 was considered Simulation was done along with 3 different shading options, i.e. Normal w/o shade, With 0.6m chajja protection, With 0.6m chajja + 0.6 fins on both sides of opening 9
Shading Payback A simple payback period when compared for the North side window is less than 2 Years Annual Power Consumpti on in kwh Energy cost (kwh X Rs.5) Decrease in cost on Load (Rs.) Shading Type - Mumbai Chajja Length (R ft) Increase in Cost (Rs.) Simple payback period (Yrs.) Normal 10759 53795 0 0 0 0 2' Chajja 10283 51415 2380 20 2000 0.84 2' Chajja + 2' Fin 10050 50250 3545 40 4000 1.13 Shading Type Bangalore Normal 8960 44800 0 0 0 0 2' Chajja 8410 42050 2750 20 2000 0.73 2' Chajja + 2' Fin 8185 40925 3875 40 4000 1.03 Shading Type Ahmedabad Normal 12271 61355 0 0 0 0 2' Chajja 11921 59605 1750 20 2000 1.14 2' Chajja + 2' Fin 11700 58500 2855 40 4000 1.40 Shading Type Delhi Normal 11026 55130 0 0 0 0 2' Chajja 10649 53245 1885 20 2000 1.06 2' Chajja + 2' Fin 10433 52165 2965 40 4000 1.35 Shading Type Dehradun Normal 9058 45290 0 0 0 0 2' Chajja 8795 43975 1315 20 2000 1.52 2' Chajja + 2' Fin 8618 43090 2200 40 4000 1.82 Way Forward: Modern Technology In modern urban scenario, space is a constraint and providing more thermal mass would increase cost of construction and would make the technique commercially unviable One can create a Virtual Mass by incorporating a grid of welded iron pipes filled with water and connected to a tank which can later be used for hot water requirement Virtual River, being a cooling tower, circulating cool water through the grid This technique can take away the heat and would assist in maintaining envelope temperature below human skin temperature 10
Way Forward: Modern Technology Wall Section preferably on the service wall (west side) Floor section Way Forward : Waste Heat Recovery In the urban scenario, use of electrical geysers for bath hot water generation is common Typical geyser ratings are 3 kw On an average, hot water requirement per family would be around 100 liters per day In the high-rise buildings, terrace areas are not sufficient to install solar hot water systems If heat rejected at Condenser can be utilised for hot water generation, use of electrical geysers can be stopped A single 1 TR Window / split AC unit, operated over-night, would generate about 200 Liters of hot water at 40 deg C, free 11
Way Forward : Multi-tier tier Cooling Current Practice In a Window AC, the refrigerant evaporates at about 4ºC, the air circulates over the coil and goes to the room, it picks up the load and returns for re-cooling Proposed Practice A three tier cooling system has 3 - sets of evaporators High temperature system for direct structure cooling Medium temperature set for dry comfort cooling Low temperature unit for fresh air & dehumidification The energy efficiency of this system is much higher; since the average evaporation is at about 15ºC Energy bill could reduce by up to 30% for same tonnage Multi-tier tier Cooling 3 - TIER SYSTEM Space cooling air supply at 20 C Fresh/room air mix dehumidified at 10 C. to each occupant. More oxygen in the breathing zone. Floor cooling at 30 C IAQ is like a garden rather than a refrigerator 12
12/21/2009 Way Forward: Indoor Plants U Common Name Botanical Name Family Description Moth Orchid Phalaenopsis Orchidaceae A very good indoor plant. Hanging / pot plant. Available in vibrant color varieties. Unlike other plants, orchids take in co2 at night and release oxygen. Propagation through cutting, plantlets Preferred Environments / Placement. Bright light to filtered light is preferred. Bedrooms and other night occupancy rooms are recommended to keep orchids. Soil / Water requirements Generous amount of water with long gaps are recommended. Also tropical or high humidity climate is suited for growth. Benefits The plant reduces the Xylene (generated from computer screens) percentage to considerable extent. orchids are effective at removing acetone, an ingredient of plastic and formaldehyde, found in carpeting, pressed wood, paint and shelving. Preferred location bedroom, dinning (releasing Oxygen at night) Way Forward: Indoor / Balcony Plants 13
Way Forward Japan has already discarded business suits in offices and increased setpoint to 26 deg C Recently Switzerland have passed a law and it would be mandatory to maintain the room temperatures at or above 26 deg C in the summer Use variable Evaporating system in the window air-conditioners to maintain 15% FRESH AIR in the room at 30% lower costs When would we???????? 2 Scenarios Temp difference of 14 deg C Temp difference of 7 deg C 14
Credit I am thankful to my friend Mr. Surendra Shah for allowing me to use some of his data for this presentation purpose Thank You! 15