T.Guru Aarat

T.Guru Aarat
....Coz we see all around

Blog Archive

Wednesday, 12 July 2017

Technolgy : Helping:: Harming Society

As we get ready to celebrate Earth Day next week, I can’t help but think about how technology both helps and harms our environment.
On the positive side, tech is helping cut down on the use of some resources. Reading newspapers and documents on screens means chopping down fewer trees for paper. Using email cuts down on the environmental cost not just of paper and envelopes but all the fuel it takes to get a letter from place to place. The ability to telecommute or participate in an online conference reduces fuel consumption and carbon emissions.
And, of course, it is technology that’s enabling electric cars and hybrids, and more efficient heating, lighting and cooling systems. Sensor technology enables us to have lights turn on only when needed and off a few seconds later.
We have a lot more electronic devices, but the good news is that they are getting increasingly efficient. Still, globally, our demand for electricity is growing at the rate of 2.4 percent a year. That doesn’t sound like much, but it compounds over time, which means a doubling of consumption between 2000 and 2030. Much of that growth is in developing nations. The U.S. Energy Information Administration projects annual U.S. consumption growth at only 0.8 percent between now and 2040 which is a much slower rate than we’ve experienced over the past 50 years. And much of that slowdown in growth has to do with more efficient technology.
Incandescent bulbs are rapidly on their way to extinction, which is a good thing. CFL bulbs are about 75 percent more efficient and LED bulbs — which are starting to come down in price but are still quite expensive — are even more efficient, generate almost no heat and last a lot longer, which means having to manufacture, ship — and screw in — fewer of them over time. The U.S. Department of Energy estimates that widespread use of LED lighting could save the “equivalent annual electrical output of 44 large electric power plants,” saving “more than $30 billion at today’s electricity prices.”
Other electronic devices, including audio systems and TVs, are also getting more energy-efficient, but collectively they still consume a lot of power. And just because something is more efficient than what it replaced, that doesn’t mean we should leave it on all the time. I used to think there was no need to turn off my solid-state audio system until I measured its energy use with a Kill A Watt EZ energy meter and discovered it was using a whopping 47 watts. My DVD player was sucking up 26 watts in idle mode and my digital video recorder, which had to run all the time so it could record shows, used 30 watts.
A few years ago the Energy Department estimated that, in the average home, 40 percent of all electricity used to power home electronics is consumed while the products are turned off. Some of this standby power, sometimes called “vampire power,” is sucked up by appliances such as TVs that sip energy so that they’ll work with a remote control and turn on almost instantly. The number of “always on” devices will skyrocket over time as more and more are connected to networks and always in “listening mode” for remote commands.
Industry efforts, government regulations and voluntary programs like the International Energy Agency’s “1-watt initiative” are helping to reduce standby power, but the rest of us can do our part by switching off devices that don’t need to be on and unplugging all those power bricks (like the ones that power our phones) that use small amounts of power even when they’re not in use. A simple trick is to connect them to a power strip that you can switch off when you’re not charging anything.

Finally — and I admit I’m often guilty of buying the latest versions of gadgets — we need to think about slowing down the replacement cycle. Every time we replace our cellphone or tablet it means that another one has to be manufactured and shipped to us, and our old one needs eventually to be recycled. All of that takes resources.

Monday, 12 December 2011

how does solar enegy work?

Solar photovoltaic cells (solar PV)

Solar photovoltaic cells are how we generate electricity directly from sunlight. The light shines on solar panels, which, via a lot of physics, turn the sunlight into a direct current.

Solar panels

This is the way solar PV and solar thermal collect solar energy. The panels themselves differ, but they are the same in principle, and they share many of the same properties.
The energy collected by solar panels is proportional to their surface area, so the bigger the better.
In terms of appearance, they tend to be quite flat, though thermal panels are generally thicker than solar photovoltaic panels.
This is because there is less of a mechanical aspect to photovoltaic panels, as everything is electronic.

Thursday, 1 December 2011

SOLAR ENERGY .................FOR A SAFE FUTURE

Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available renewable energy on earth. Only a minuscule fraction of the available solar energy is used.

Solar powered




electrical generation relies on heat engines and photovoltaics. Solar energy's uses are limited only by human ingenuity. A partial list of solar applications includes space heating and cooling through solar architecture, potable water via distillation and disinfection, daylighting, solar hot water, solar cooking, and high temperature process heat for industrial purposes.To harvest the solar energy, the most common way is to use solar panels.

Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.


About half the incoming solar energy reaches the Earth's surface.The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with a small part in the near-ultraviolet.

Earth's land surface, oceans and atmosphere absorb solar radiation, and this raises their temperature. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection. When the air reaches a high altitude, where the temperature is low, water vapor condenses into clouds, which rain onto the Earth's surface, completing the water cycle. The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones and anti-cyclones. Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C. By photosynthesis green plants convert solar energy into chemical energy, which produces food, wood and the biomass from which fossil fuels are derived.
The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year. In 2002, this was more energy in one hour than the world used in one year. Photosynthesis captures approximately 3,000 EJ per year in biomass. The amount of solar energy reaching the surface of the planet is so vast that in one year it is about twice as much as will ever be obtained from all of the Earth's non-renewable resources of coal, oil, natural gas, and mined uranium combined.

Solar energy can be harnessed in different levels around the world. Depending on a geographical location the closer to the equator the more "potential" solar energy is available