ENERGY EFFICIENT COOLING STRATEGIES
By Aurangzeb Soharwardi(published daily The NEWS 18 sep 2010)
The adverse impact of the rising global warming on human and other forms of life is eminent, which has resulted in an unknown fear for the future having environmental degradation and rising temperature. Industrial states of the world are being accused of atmospheric pollution through gas and heat emissions from their factories and the fleet of big vehicles they use, that spurs global warming. And now developing countries like China are adding to pollution by heavily relying on coal for power generation. Now not only coal, which is being used by developing countries as a source of energy, add to global warming, but also the many automobiles on roads contribute a great deal to pollution and slow change in climate. As regards Pakistan there were hints that the earthquake in the North-Western parts could be the outcome of climatic change. Even un-seasonal rains in Pakistan are being attributed to climatic changes. In Pakistan, we have only guesswork instead of thorough research , What is known is that the atmospheric pollution is widespread and centers in large cities like Karachi, Lahore, Gujranwala, Faisalabad are highly polluted by automobile fumes, tanneries and combustion . Rivers are polluted by industrial effluents dumped in them all over Pakistan. Even coastal waters around Karachi are polluted by industrial waste and chemicals dumped into the sea which poison the sea life as well. Cities have a high- density of carbon in the air from automobile fumes which is increasing day by day. Conversion of forests and fields in to residential and commercial areas is adding fuel to this blazing fire. In Pakistan, the normal temperature is rising rapidly, calling for a dire need of making efforts for cooling homes and buildings. For making cooling arrangements, Various cooling systems and techniques have been in use for centuries .During the ancient times, cooling effect used to be created by an articulate use of water and air in the construction . The best examples can be found in the Mughal architecture of the recent past, where palaces and forts were constructed to enhance the cooling effect near the rivers and canals with a complete internal hydrolic system . Mughals generally used a cooling system called ‘BAULI’, which can be witnessed in various palaces and gardens constructed by them, like the Babri mosque’s Tughluquid style integrated other indigenous design components and techniques, such as air cooling systems presented as Islamic architectural elements like arches, vaults and domes. In the Babri Masjid and other palaces and gardens the high ceiling, domes, and large grill windows all served as a passive environmental control system that brought down the temperature and also allowed in natural ventilation as well as daylight Cooling systems. Other civilizations all over the world also innovated their own customized cooling systems. Rising temperature has necessitated that modern homes and buildings should be designed to cater for the hot weather in Pakistan with a systematic and scientific town planning. Due to increasing temperature in the region , alternate arrangements for cooling are being made by using room coolers and particularly the air conditioners. Due to this energy consumption in Pakistan has increased considerably during the recent past with an annual load growth more than 15%, to about 17000 MW as peak demand for over 18 million consumers of Pakistan Electric Power CO. 60 million home appliances used by these consumers , out of which maximum numbers is of microwave ovens and air conditioners which add an excess load of 3500 MW in the demand graph, leading to a serious energy crises. The time has come when we have to seriously contemplate various modern techniques and methods of making cooling arrangements to reduce the consumption of electricity, which will be posing a precarious threat in the coming times. In Europe, USA and china, the emphasis on energy efficient construction designs and alternate sources for cooling is already being laid, witnessing quite appreciable progress. Some of the modern mechanical/electrical cooling systems being used are , CTI Certified Cross Flow Rectangular Cooling Tower , Cross Flow Closed Type Cooling Tower , Counter Flow Round Cooling Tower, Industrial Cooling Tower, Cross Flow Rectangular Cooling Tower, CTI Certified Cross Flow Rectangular Cooling Tower, Counter Flow Square Cooling Tower, Square Counter Flow Cooling Tower, Round Counter Flow Cooling Tower , Closed Cross Flow Cooling Tower , Stainless Steel Cross Flow Rectangular Cooling Tower . Another significant system HVAC (pronounced either “H-V-A-C” or “H-vak”) is an acronym that stands for the closely related functions of “Heating, Ventilating, and Air Conditioning”- the technology of indoor environmental comfort. HVAC system design is a major sub discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. Refrigeration is sometimes added to the field’s abbreviation as HVAC&R or HVACR, or ventilating is dropped as in HACR (such as the designation of HACR-rated circuit breakers). HVAC is particularly important in the design of medium to large industrial and office buildings such as skyscrapers and in marine environments such as aquariums, where safe and healthy building conditions are regulated with temperature and humidity, as well as “fresh air” from outdoors. It is mostly being used in multi storey buildings where huge investment is involved, but for homes and small scale construction, some other options have to be evolved. Installing effective cooling systems is not only necessary for sky scrappers but also for small houses, Like in the villages people erect tents and make mud houses keeping into consideration the wind direction and proximity of water. Obviously, the easiest way , considered, to keep a home cool during the summer is to use an air conditioner to keep the temperature down, but there are other options that neither proliferate electricity demand nor raise the energy bill quite significantly. The best way to keep your home cool is to keep the heat out. The most common sources of internal heat gain are; appliances, electronic devices, and lighting. Be aware from where the heat is coming .For already constructed houses , first of all heat or energy audit is a must. For Locating Air Leaks first, make a list of obvious air leaks .The potential energy savings from reducing drafts in a home may range from 5% to 30% per year, and the home is generally much more comfortable afterward. Check for indoor air leaks, such as gaps along the baseboard or edge of the flooring and at junctures of the walls and ceiling. Check to see if air can flow through these places like Electrical outlets , Switch plates ,Window frames ,Baseboards ,Weather stripping around doors , Fireplace dampers ,Attic hatches ,Wall- or window-mounted air conditioners. Also look for gaps around pipes and wires, electrical outlets, foundation seals, and mail slots. Check to see if the caulking and weather stripping are applied properly, leaving no gaps or cracks, and are in good condition.. Heat loss through the ceiling and walls in your home could be very large if the insulation levels are less than the recommended minimum.. Inspect heating and cooling equipment annually, or as recommended by the manufacturer. If you have a forced-air furnace, check the filters and replace them as needed. Generally , change them about once every month or two, especially during periods of high usage. Have a professional check and clean your equipment once a year.. To augment the cooling effect by increasing the surface area, the housing may be provided with thin metal fins. On some stationary mechanical transmissions, it may be necessary to circulate the lubricating oil through pipes surrounded by cold water or to use a fan to blow air through pipes surrounded by the oil in the reservoir. On many electric motors, a fan is attached to the rotating element to create a current of cooling air through the housing. The main ways that heat enters the home in summer are through: Heat transfer from the external surfaces of the house that are warmed by the external air temperature and the sun. The sun shining through windows directly heating the home interior. Hot air infiltration through open windows, doors, air vents and gaps around doors and windows. Internal heat generated by the people inside and the appliances being used. It is possible to use ‘passive’ cooling techniques to reduce your home’s heat gain such as installing insulation, shading windows, caulking ,weather stripping, ensuring good garden and landscaping design, and using natural ventilation. Using these techniques can help to keep your home comfortably cool without the need for expensive air-conditioning. House design, layout, construction materials and other factors can all restrict your home’s ability to reduce heat gain sufficiently and as such, air-conditioning may be required. Air conditioners may offer tempting temporary relief from summer heat, but they’re a huge environmental hazard too. By reducing the amount of heat in your home, you will have to use less energy to cool it. You may be cooling your home, but the fossil fuels you’re burning in the process are only making your summers hotter. Insulations , are essential to keeping your home warm in cold climates, but they also help keep your home cool in hot weather. The attics of most homes absorb heat through the roof, and insulating the attic floor will keep this heat from radiating down into the house. Fiberglass insulation, at least R-30, is easy to install. The cost will be recouped quickly in lower energy bills throughout the year. Caulking and weather stripping doors and windows will also prevent warmer outside air from seeping into your home. The cost of these materials is very low and application is simple. Reflective Barriers: An important consideration in passive cooling is house color. Dark-colored home exteriors absorb 70% to 90% of the radiant energy from the sun that strikes the home’s surfaces. Some of this absorbed energy is transferred into your home by way of conduction, resulting in heat gain. In contrast, light-colored surfaces effectively reflect most of the heat away from your home. Another method for reflecting incoming heat is to install a radiant barrier. This foil-faced paper can be stapled to the roof rafters on the underside of your roof.. Shading is the simplest, most effective way to cool your home and reduce energy consumption. Up to 40% of the costs of cooling can be saved by shading techniques such as landscaping, and working the drapes and blinds. Vines provide shading and cooling, and are quick to grow. Trellises should be placed on the hottest side of the house, and blocked out at least 6″ from the wall to protect the wall and provide a buffer of cool air. Certain vines, such as deciduous clematis and wisteria, grow well in containers where open ground is unavailable. Trees, vines and shrubs can be used to shade your home and reduce your energy bills. Trees or shrubs can also be planted to shade air conditioning units, but they should not block the airflow. Take care to locate trees or large bushes where their roots will be clear of underground wires, sewer lines or septic tanks, or the house foundation. Plant trees or shrubs to shade air conditioning units, but not block the airflow. A unit operating in the shade uses less electricity. Deciduous trees planted on the south and west sides will keep your house cool in the summer and allow the sunlight to warm the house during the winter. Rock walls, paved areas and rock features should be kept to a minimum on south and west sides of the home, because they increase temperatures by radiating heat. Drapes and curtains made of light-colored fabrics reflect much of the sun’s rays and help reduce heat gain.. Two-layered drapes are most effective for both summer cooling and winter heating. Close south and west-facing curtains during the day for any window that gets direct sunlight. Exterior shade screens, also called “sun screens” “shade cloths” or “solar shields”, prevent sun from entering a window. These can be installed on windows exposed to direct sunlight. Shade screens are lightweight, durable and easy to install. Bamboo blinds can also be used as shade screens. Unlike insect screens, shade screens are specially made to block between 50 and 90 percent of the energy striking the outside of the window. The term “shading coefficient” describes the amount of heat that penetrates the screen: lower numbers mean less energy gets through. By removing Interior Heat Thermal Chimney, Opening the lowest windows on the side from where the breeze is coming , leaving interior doors open and opening the upstairs windows on the opposite side of the house, the warm air in the house will draw upwards and out the upper window, an effect called ‘thermal siphoning’. Install white window shades, drapes, or blinds to reflect heat away from the house. Close blinds, shades and draperies facing the sun (east-facing windows in the morning and west-facing windows in the afternoon) to keep the sun’s heat out and help fans or air conditioners cool more efficiently. Now if you have air conditioning, use it wisely. Don’t put lamps, televisions or other heat-generating appliances next to your air-conditioning thermostat, because the heat from these appliances will cause the air conditioner to run longer. The heat they produce will make your house warmer than it really is. Unless you absolutely need them, turn off incandescent lights and heat-generating appliances. Energy for lighting accounts for about 20% of your electric bill. Examine the wattage size of the light bulbs in your house. Energy savers are highly recommended to be used. Replace incandescent bulbs with compact fluorescent; they produce the same light but use a fifth the energy and heat. Try to avoid heat-generating activities, such as cooking, on hot days or during the hottest part of the day. If you are cooking, use your range fan to vent the hot air out of your house.. Paint your roof white , If you’ve got a flat roof, paint it with a specially formulated reflective paint or just paint it white. The reflective effect will help to keep the rooms under the flat roof much cooler. Humidity makes room air feel warmer, so reduce indoor humidity. Minimize mid-day washing and drying clothes, showering, and cooking. And when you must do these things, turn on ventilating fans to help extract warm, moist air. Avoid landscaping with lots of un shaded rock, cement, or asphalt on the south or west sides because it increases the temperature around the house and radiates heat to the house after the sun has set. If the attic isn’t already insulated or is under-insulated, insulate it now. If you live in a relatively dry climate, a bowl or tray of ice in front of a box fan can cool you as it evaporates. Change air filters monthly during the summer. Use a programmable thermostat using it at 26 degrees, with your air conditioner to adjust the setting at night. Lower the thermostat on your water heater; 115° is comfortable for most uses Consider installing a whole house fan or evaporative cooler (a “swamp cooler”) if appropriate for your climatic conditions. Attics trap fierce amounts of heat; a well-placed and -sized whole-house fan pulls air through open windows on the bottom floors and exhausts it through the roof, lowering the inside temperature and reducing energy use by as much as third compared with an air conditioner. An evaporative cooler pulls air over pads soaked in cold water and uses a quarter the energy of refrigerated air, but they’re useful only in low-humidity areas. Use a microwave oven instead of a conventional electric range or oven. . Turn off your computer and monitor when not in use. Plug home electronics, such as TVs and VCRs, into power strips, and turn power strips off when equipment is not in use.. A multipronged strategy encompassing, change in over all life style, effective environmental management, energy efficient construction and energy discipline has to be adopted in order to control abruptly increasing energy demand. The government , through its regulatory agencies and the consumers must collaborate to cater for this aspect other wise the country will be facing an unmanageable energy crises, along with environmental degradation.