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| SCIENCE TRIBUNE | Thursday, May 17, 2001, Chandigarh, India |
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Solar ponds for energy collection
SCIENCE QUIZ
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Electrical energy conservation THE ever increasing demand for electrical power is causing depletion of scarce non-renewable energy sources such as coal, gas and fossil fuels etc. besides polluting the environment. There is now greater awareness to stop the indifferent use of these resources. As such conservation measures have to be adopted by: (1) The consumers — their bills are reduced as they save electricity and (2) The utilities — the need for new generation and consequently investment with a significant foreign exchange component is reduced. One watt saved at the point of consumption is more than 1.5 watts generated. While it costs approximately Rs 4 crore and 4-5 year to create 1 MW of new generation capacity with additional expenditure on transmission and distribution system, the same amount spent on energy conservation could provide 2-3 MW of avoidable generation capacity and yield result in 1-2 years. In India, the largest end users of electricity are:- Industrial motors = 38% Agricultural Pumps = 23% Lighting = 13-17% Domestic Appliances = 11% Some of the guidelines for the following sectors will reduce electricity bills by 15-20%. So, why not give them a try? Industrial Electric motors account for two-thirds of industrial electricity consumption; the value of the electricity that motors consume during their lifetime can be 200 times the original price. Ironically, poor specification of motors may come to your attention very soon, but of it’s right the first time it is likely that no one will ever notice. Proper motor specification in the design stage is thus very important. Use energy efficient motors, properly sized and placed as close to load as possible. For the same output and efficiency, since better and more active materials are used in energy efficient motors, they have less total losses, are more reliable, have longer life and are more environment friendly as less heat is generated. These motors thus pay for their critical cost in power saving. Every plant has its own pattern which would be revealed by the daily readings of Max. Demand. Carefully study the need to run motors/equipment in a staggered manner so as not to affect the process and at the same time keeping the Max. Demand. within limits. Use transformers with less no-load losses and operate them at high efficiency in the range of 75-80% of their rated capacity. Replace old transformers fitted with hot rolled steel cores as and when they fail. Seal leaks of water, steam compressed air and oil; replace missing insulation; worn out bearings; belts and gears; adjust burners; clean dirty lamps; choose proper lubricants and avoid excessive heating and cooling. Use of non-standard welding set should be avoided as it consumes more power than rated. Design factory building for better penetration of natural light and air. Install voltage stabilisers, where needed to check fluctuation and static condensers to improve P.F. Use electronic controllers like soft starters and variable voltage/frequency controllers. 20-25% energy savings are realised by resizing and modification of pumps and blowers. A 5°C decrease in evaporator temperature in an airconditioning unit increases the specific power consumption by 15%. Replacement of inefficient aluminium or fabricated steel fans by FRP fans with aerofoil design results in electricity savings in the range of 15-40%. In these days of specialisation, employ only skilled staff without which the modern complex industry cannot run successfully. Agricultural sector As per recent estimates there are more than 120 lakh electric pumps and about 60 lakh diesel pumps irrigating out lands in India consuming 6000 crores kwh of electricity and 600 crore of diesel oil every year. Therefore, consumption wise agricultural sector has a tremendous scope of saving. By replacing old high friction foot valves with ISI mark foot valves/reflex valves, using Rigid PVC pipes in suction and delivery lines of pumps sets, a saving of 30% can be achieved. Avoid sharp bends. Use high efficiency pumps. Proper alignment of pump and motors saves energy. The pump should be within 10 feet of water level. Keep delivery pipe as close to the ground as possible, preferably not more than 2 feet. Larger pipes save energy up to 10%. In addition a NGO — Insititute of Cooperative Management in Ahmedabad undertakes rectification of agricultural pumps which yield energy conservation by 20% to 50%. The main aspect of flat rate tariff gives the opportunity to the purchaser for buying the big sets and avoid switching off the power. Hence, metered supply is essential. To help farmers, subsidised rates may be charged instead of free electricity, which encourages its misuse and wastage. Provide shunt capacitors on the motor terminals to keep voltage conditions stable and avoid damage to the motor. Lighting * Use of 36 watts flourescent tube lights instead of 40 watts in large establishments would be cheaper and result in considerable saving in energy bills. Insist on Power Factor Corrected Flourescent tubes for all new installations. The old ballast has a power factor of 0.5 as against 0.95 of the type suggested above. * Use most efficient light sources. * Modern compact Fluorescent Lamps. (CFL) consume 80% less electricity than ordinary incandescent bulbs and last about 10 times longer. * A comparison of light output between the two types is as under:
CFL is costly in the initial stages but the cost difference is paid back in a very short period of time besides saving in replacement labour. Also the CFL work efficiently within the range of 170-250 volts which make it ideal for the prevailing conditions. * A dusty bulb emits 20% less light as compared to a clean one which lasts longer because there is less heat build-up inside the bulb. Make sure that it is cool before wiping it off with a damp cloth. * Turn off lights during lunch break and all lights other than required for security when the building is unoccupied. * Use work lighting only and reduced lighting in non-productive areas. This aspect is taken care of during initial design/installation. Paint with light colours. Commercial, Domestic sector In commercial sector lighting and HVAC (Heating, Ventilation, Air Conditioning and Cooling) from the bulk of electricity use. * During heating and air conditioning periods, make certain that all doors and windows are closed in conditioned areas and that sheds, blinds or drapes are closed during the cooling periods. Heaters if used should be turned off during non-occupancy periods. * Use sun control film on window glasses especially in airconditioned rooms. This will reduce thermal load of ACs and the cooling fans. Switch off the ACs half an hour before leaving the room. * It would be of interest to note the energy consumed monthly by electrical appliances in the average household from the following table so that one can plan actions accordingly:
* Buy a refrigerator with automatic de-frost system. Keep the freezer/frig full. There is less air to fall out when you open the door and food "stores" the cold so that the motor runs less. * While installing a new fridge it should tilt back slightly so that the door closes faster. Gasket should be leak proof. * Water Heater. By lowering the
setting of temperature on the thermostat by 10°F, you can save about
Rs 1000/- per annum on electricity bills.
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Solar ponds for energy collection TODAY, the rural populace owes much to the Sun than ever before. This is because, it lights their homes, pumps water and even brings the television images live for them. However, there is surely more to it than what meets the eye. Now, solar energy technology is also being actively considered in various applications like the refrigeration, water desalination, process heating, drying and importantly, for power generation. A relatively new technology known as the Solar Pond technology is gradually beginning to emerge. Ideally speaking, these types of ponds are effective systems for a large area energy collection and storage. The predominant constituent of a solar pond is a body of saline water, within which, the concentration of the dissolved salts increases with depth. This causes a relative increase in the water density as well. Further, as the water body captures the solar radiation, the water at the bottom gets heated. This way, the density gradient suppresses the convention current, following which, the heat is trapped at the base of the pond at high temperatures. The heat thus generated can be put to an effective use for a variety of end use applications, using the heat exchanger. This is the basic underlying technology of a solar pond, though a pond can be either shallow or deep. In principle, there are three different layers or regions in a solarpond. The top layer is the surface zone, also known as the upper convicting zone at an atmospheric temperature and with marginal salt content. In contrast, the bottom zone is quite hot, roughly between 70-85 degree celsius and quite salty as well. In fact, this zone is responsible for the collection and storage of solar energy in the form of heat. Due to this capability, it is also known as the storage zone or lower convective zone. Finally, acting as a barrier between the two zones, is an all important gradient zone or the non-convecting zone. In this particular zone, the salinity increases, as one goes down. This difference in the salinity between the two layers creates a salinity gradient. In this way, the stable gradient zone acts as a transparent insulator, which enables the sunlight to reach the bottom zone and get trapped there. Ultimately, it is this useful energy that is derived from the pond in the form of hot brine from the storage zone. Beyond doubt, there is no geographical constraint with adopting the solar pond technology anywhere, but locations with a large scale availability of cheap salt, water/sea water and importantly high solar radiation intensity surely make a hot choice to do so. It is for these reasons, Bhuj, a coastal location in Gujarat, today boasts of having the largest operating solar pond in the country. This 6000m2 pond is a successful operation and has been supplying the process heat to the Kutch dairy. This specific solar pond project was developed at a total outlay of approximately Rs 9 million, with the collaborative efforts of the Gujarat Energy Development Agency (GEDA), the Tata Energy Research Institute (TERI) and the Gujarat Dairy Development Corporation (GDDC). Of course, the design of a solar pond of this magnitude involves a fair amount of civil construction work as well, apart from incorporating the solar thermal technology principles. The Bhuj solar pond is about 100m long and 6m wide and has a depth of about 3.5m. To complement this facility, evaporation ponds (for recycling salt), a 225 m2 test solar pond and a salt mixing pond were also put in place. Moreover, a specially designed lining scheme comprising of an effective combination of the China clay and polyethylene films was used as a preventive measure, against any seepage of saline water. Following which, the pond was filled with water and about 400t of common salt was dissolved in it to make a dense brine. As stated above, the pond has been supplying the process that to the Kutch dairy, about, 80,000 litres. Of hot water at a temperature of about 70 degree celsius is being made available to this dairy on a daily basis. However, this is not the sole use of the solar pond technology, as there are numerous other applications possible as well. These include producing the hot air for industrial and space heating applications. This hot air can be subsequently used for drying the agriculture produce, fish and chemicals, as well as for seasoning of the timber. On the other hand, the solar pond based desalination system also offers a viable solution, for yielding the sweet water from the brackish/seawater. Also, the vapour absorption system is ideally suited for operating with the solar pond. Importantly, the thermal energy stored in a pond can be used for producing the electrical power.
So, with the solar pond technology
having been successfully demonstrated at Bhuj, more and more
initiatives should be forthcoming in this direction. This is because,
India virtually soaked in the sunshine and having large deposits of
salt along its large coastline, provides an ideal environment to adopt
such a technology on a large commercial scale. At a time, when the
renewable energy technologies are poised for a big leap forward
(capacity addition of around 12,000 MW planned), the facility at Bhuj
should also get its frontiers extending. PTI
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NEW PRODUCTS & DISCOVERIES New dimension in medicine A radiologist at the Royal Sussex Hospital, southern England, holds a 3-D pictures of diseased sections inside the human body. The breakthrough in medical imaging is seen as a major advance for surgeons who can see in holograms the precise size, shape and location of tumours — like the brain tumour in the picture — and can accurately apply radiation treatment to destroy them. A new laser camera has been developed which uses parallel sections taken on a body scanner and re-integrates them into a 3-D image. The topographic "slices" — in the form of 35 mm slides — are projected through a split laser beam on to one film that is advanced between each exposure by the same margin as the distance between the sections taken by the body scanner. The resulting "complete image" shows the surgeon the exact length, breadth and depth of the diseased area and can be viewed effectively when illuminated by any point source of white light. Primarily designed for medical applications, the system is now being evaluated by other scientific and engineering experts. As the sections need not be of a human body, the same technique could be applied to the inspection of interiors of machinery adn other sealed objects. The camera has also been used to create a three-dimensional picture of an exploding nebula for an astronomer. Reducing light pollution Scientists have developed an exterior lighting system which besides making street light more efficient, reduces light pollution in a variety of places. The system — Diamon Optic — is based on a novel and unsurpassed adjustable design. It has reflectors which are so designed that no light is emitted above the horizontal, thereby reducing light that pollutes the night sky and lessening strain on drivers’ eyes. Because fewer lighting installations are required to light a given area when the reflector system is used, there are commensurate savings in capital expenditure, installation and maintenance costs and energy making, a vital reduction of increasing importance in lessening global warming. The exceptional uniformity provided by the system manufactured by D.W. Windsor of UK can reduce by up to a third the number of lighting installations usually required to cover a given area with great cost saving benefits, a report in British Commercial News said. The system has been used in a number of places
around the world. These include places such as London’s underground railway
system, Singapore’s Esplanade Brigade and the world’s largest car park at
Kuala Lumpur International Airport. PTI |
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SCIENCE QUIZ 1. A researcher named Constantine Fahlberg was one day studying the oxidation of toluene sulfamide when some material boiled over and accidentally fell on his hand. He tasted it by chance and found it to be sweet. Which synthetic sweetener had he discovered? 2. Combined CEA + CABG is a surgery used when a patient is suffering from blockade in arteries of both brain and heart. What is the full name of this surgery? 3. We all know that materials in bulk (macroscopic systems) have positive heat capacity. But physicists have recently discovered that tiny metal clusters (microscopic systems) have regative heat capacity. What does it mean? 4. Dogs are used for tracing paths of thieves, for detecting explosives, and for other such purposes. This is possible due to their highly sensitive sense of smell. Human beings have about 5 million smell-sensitive cells in their noses. Do you know how many such cells does a dog have? 5. Evolving new, high-yielding species of trees is the need of the hour. What is this process called? 6. This vehicle, without having any wheels, can move on both land and water without any contact with these. What is this vehicle called that moves on a cushion of air produced by a propeller fixed on its lower surface? 7. When gunpowder is ignited, a number of gases are produced almost instantaneously, resulting in a violent explosion. It is therefore used in a variety of ammunition, in fireworks and in explosives meant for blasting operations. What does gunpowder consist of? 8. What is an instrument called which is used to detect sounds (for example, produced by a submarine or a whale) transmitted through water? 9. Do you know how many muscles, joints and nerve cells does an adult human body contain? 10. The 20,000th member of the Sun’s family, officially recognised by the International Astronomical Union, is the largest body between Neptune and Pluto. Can you name this latest member which has been dubbed after a Hindu god? Answers 1. Sachhrin |
