Category Science

HOW IS THE WIND USED TO GENERATE ELECTRICITY?

The power of the wind can he used to generate electricity using huge wind turbines. The blades of a wind turbine drive a generator that produces electricity. Large groups of wind turbines, called wind farms, are built in areas where the wind blows fairly constantly. Flat, open areas of land and coastal areas are popular locations for wind farms. The electricity produced by these farms is fed into the electricity grid along with that coming from other sources.

Wind energy (or wind power) refers to the process of creating electricity using the wind, or air flows that occur naturally in the earth’s atmosphere. Modern wind turbines are used to capture kinetic energy from the wind and generate electricity.

When the wind blows past a wind turbine, its blades capture the wind’s kinetic energy and rotate, turning it into mechanical energy. This rotation turns an internal shaft connected to a gearbox, which increases the speed of rotation by a factor of 100. That spins a generator that produces electricity.

Typically standing at least 80 meters (262 feet) tall, tubular steel towers support a hub with three attached blades and a “nacelle,” which houses the shaft, gearbox, generator, and controls. Wind measurements are collected, which direct the turbine to rotate and face the strongest wind, and the angle or “pitch” of its blades is optimized to capture energy.

A typical modern turbine will start to generate electricity when wind speeds reach six to nine miles per hour (mph), known as the cut-in speed. Turbines will shut down if the wind is blowing too hard (roughly 55 miles an hour) to prevent equipment damage.

Over the course of a year, modern turbines can generate usable amounts of electricity over 90 percent of the time. For example, if the wind at a turbine reaches the cut-in speed of six to nine mph, the turbine will start generating electricity. As wind speeds increase so does electricity production.

Another common measure of wind energy production is called capacity factor. This measures the amount of electricity a wind turbine produces in a given time period (typically a year) relative to its maximum potential.

For example, suppose the maximum theoretical output of a two megawatt wind turbine in a year is 17,520 megawatt-hours (two times 8,760 hours, the number of hours in a year). However, the turbine may only produce 7,884 megawatt-hours over the course of the year because the wind wasn’t always blowing hard enough to generate the maximum amount of electricity the turbine was capable of producing. In this case, the turbine has a 45 percent (7,884 divided by 17,520) capacity factor. Remember—this does not mean the turbine only generated electricity 45 percent of the time. Modern wind farms often have capacity factors greater than 40 percent, which is close to some types of coal or natural gas power plants.

There are three main types of wind energy:

  • Utility-scale wind: Wind turbines that range in size from 100 kilowatts to several megawatts, where the electricity is delivered to the power grid and distributed to the end user by electric utilities or power system operators.
  • Distributed or “small” wind:  Single small wind turbines below 100 kilowatts that are used to directly power a home, farm or small business and are not connected to the grid.
  • Offshore wind: Wind turbines that are erected in large bodies of water, usually on the continental shelf. Offshore wind turbines are larger than land-based turbines and can generate more power.

picture Credit : Google

 

WHAT IS GEOTHERMAL ENERGY?

In volcanically active areas of the world, heat energy inside the earth is used for power. Geothermal power-plants use the heat produced by molten rocks to create hot water and steam. The steam powers turbines, while the hot water is piped to homes. Iceland and New Zealand are two countries where geothermal energy is used.

Geothermal energy comes from the heat within the earth. The word “geothermal” comes from the Greek words geo, meaning earth,” and therme, meaning “heat.” People around the world use geothermal energy to produce electricity, to heat buildings and greenhouses, and for other purposes.

The earth’s core lies almost 4,000 miles beneath the earth’s surface. The double-layered core is made up of very hot molten iron surrounding a solid iron center. Estimates of the temperature of the core range from 5,000 to 11,000 degrees Fahrenheit (F). Heat is continuously produced within the earth by the slow decay of radioactive particles that is natural in all rocks.

Surrounding the earth’s core is the mantle, thought to be partly rock and partly magma. The mantle is about 1,800 miles thick. The outermost layer of the earth, the insulating crust, is not one continuous sheet of rock, like the shell of an egg, but is broken into pieces called plates. These slabs of continents and ocean floor drift apart and push against each other at the rate of about one inch per year in a process called continental drift.

Magma (molten rock) may come quite close to the surface where the crust has been thinned, faulted, or fractured by plate tectonics. When this near-surface heat is transferred to water, a usable form of geothermal- energy is created.

Geothermal energy is called a renewable energy source because the water is replenished by rainfall, and the heat is continuously produced by the earth. Geothermal energy is heat derived within the sub-surface of the earth. Water and/or steam carry the geothermal energy to the Earth’s surface. Depending on its characteristics, geothermal energy can be used for heating and cooling purposes or be harnessed to generate clean electricity. However, for electricity, generation high or medium temperature resources are needed, which are usually located close to tectonically active regions.

This key renewable source covers a significant share of electricity demand in countries like Iceland, El Salvador, New Zealand, Kenya, and Philippines and more than 90% of heating demand in Iceland. The main advantages are that it is not depending on weather conditions and has very high capacity factors; for these reasons, geothermal power plants are capable of supplying baseload electricity, as well as providing ancillary services for short and long-term flexibility in some cases.

There are different geothermal technologies with distinct levels of maturity. Technologies for direct uses like district heating, geothermal heat pumps, greenhouses, and for other applications are widely used and can be considered mature. The technology for electricity generation from hydrothermal reservoirs with naturally high permeability is also mature and reliable, and has been operating since 1913. Many of the power plants in operation today are dry steam plants or flash plants (single, double and triple) harnessing temperatures of more than 180°C. However, medium temperature fields are more and more used for electricity generation or for combined heat and power thanks to the development of binary cycle technology, in which geothermal fluid is used via heat exchangers to heat a process fluid in a closed loop. Additionally, new technologies are being developed like Enhanced Geothermal Systems (EGS), which are in the demonstration stage.

To promote wider geothermal energy development, IRENA coordinates and facilitates the work of the Global Geothermal Alliance (GGA) – a platform for enhanced dialogue and knowledge sharing for coordinated action to increase the share of installed geothermal electricity and heat generation worldwide.

picture Credit : Google

 

HOW IS WATER USED FOR POWER?

Water is used to generate electricity in three ways. Hydroelectric power is one of the most commonly used forms of renewable energy, accounting for around 7% of the world’s electricity production. Specially-built dams feed falling water into turbines that drive electricity generators. A similar system controls the flow of water in tidal areas, with a barrier built across an estuary or river. Wave power can also be harnessed by using floating generators that transform wave movement into electricity.

People have used moving water to help them in their work throughout history, and modern people make great use of moving water to produce electricity. No doubt, Jack the Caveman stuck some sturdy leaves on a pole and put it in a moving stream. The water would spin the pole that crushed grain to make their delicious, low-fat prehistoric bran muffins.  For many centuries, water power was used to drive mills to grind grain into flour. People have used moving water to help them in their work throughout history, and modern people make great use of moving water to produce electricity.

Hydroelectric energy is produced by the force of falling water. The capacity to produce this energy is dependent on both the available flow and the height from which it falls. Building up behind a high dam, water accumulates potential energy. This is transformed into mechanical energy when the water rushes down the sluice and strikes the rotary blades of turbine. The turbine’s rotation spins electromagnets which generate current in stationary coils of wire. Finally, the current is put through a transformer where the voltage is increased for long distance transmission over power lines.

China has developed large hydroelectric facilities in the last decade and now leads the world in hydroelectricity usage. But, from north to south and from east to west, countries all over the world make use of hydroelectricity—the main ingredients are a large river and a drop in elevation (along with money, of course).

Although most energy in the United States is produced by fossil-fuel and nuclear power plants, hydroelectricity is still important to the Nation. Nowadays, huge power generators are placed inside dams. Water flowing through the dams spin turbine blades (made from metal instead of leaves). Power is produced and is sent to homes and businesses.

The theory is to build a dam on a large river that has a large drop in elevation (there are not many hydroelectric plants in Kansas or Florida). The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generators that carry electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam.

picture Credit : Google

 

What are the reasons cited for Sumatran Rhinos decline?

Extinct in Malaysia

The saddest news I heard last week: The Sumatran rhinoceros is now extinct in Malaysia.

Iman, the last female in Malaysia, at the Tabin Wildlife Reserve, in northeast Borneo, died in November 23, 2019. Another Sumatran rhino, Puntung was put to death in 2017. He had cancer. Tam, Malaysia’s last male rhino, died in May 2019. Fewer than 80 Sumatran rhinos are thought to exist in the wild, most on the nearby island of Sumatra. The rest are scattered across Kalimantan in Indonesia Borneo.

Christine Liew, Sabah State’s Minister of Tourism, Culture and Environment, said, “Iman was given the very best care and attention since her capture in March 2014 right up to the moment she passed. No one could have done more.” The saddest part is this. Once these rhinos roamed the jungles of Malaysia in large numbers. With habitat loss and killing of these animals for their horns, their numbers came down. Now, no Sumatran rhino is left in Malaysia.

Tam’s death is a wakeup call to find more animals in the wild, say experts coordinating WWF International’s Sumatran rhino efforts for the last two years.

This is Tam’s story. Forest officials noticed Tam wandering around an oil pam plantation in 2008. He was captured and transferred to the Tabin Wildlife Reserve in the state of Sabah. Efforts were made to mate him with two female rhinos – Puntung, captured in 2011, and Iman, captured in 2014. They were not successful.

Where do they live?

Sumatran rhinos live in remote areas of tropical rainforests. The Leuser Ecosystem, which abounds in mountains and tropical rainforest, in Indonesia is home to several small, scattered populations of Sumatran rhinos. Since these are thick jungles, sightings of rhinos are rare. No one can say exactly how many exist. Forest officials count the rhinos through what they see in camera traps.

In 2015, Sumatran rhinos were declared extinct in the wild in Malaysia. Naturalists count these reasons for the population count of rhino diminishing in Malaysia and elsewhere.

Sumatran rhinos live in small herds, scattered across islands. A small population means the Sumatran rhino’s potential to reproduce is reduced. This puts the rhino at a higher risk for extinction.
The number of Sumatran rhinos everywhere has dropped an estimated 70% in the past twenty years. This is mostly due to poaching. Fewer than a hundred remain in Indonesia, in isolated pockets. Besides, Sumatran rhinos give birth about every three to five years. So their population remains small.

Efforts to save the species

In 2018, the world’s leading conservation NGOs including the National Geographical Society, decided to form a collaboration group called the Sumatran Rhino Rescue. The members would go out, find and safely capture as many wild rhinos as possible and bring them together for captive breeding. Officials at the WWF International said, “Tam’s death underscores how critically important the collaborative efforts driving the Sumatran Rhino Rescue project are. We’ve got to capture those remaining, isolated rhinos in Kalimantan and Sumatran and do our best to encourage them to make babies.”

The experts, however, were able to understand the kind of animal Sumatran rhinos are by monitoring Tam in captivity. This information should help biologists in their rhino breeding efforts in the future. “The work that the Borneo Rhino Alliance did with advanced reproductive techniques, especially harvesting eggs and attempting to create embryos, took us one step further towards understanding of the species’ biology,” said Susie Ellis, executive director of the International Rhino Foundation.

What can we do?

We must understand how precarious the survival of Sumatran rhinos is. Don’t we want this small rhinoceros to survive? The death of Tam represents roughly one percent of the Sumatran rhino population.

But there is good news. The coalition group, Sumatran Rhino Rescue has managed to capture a new female named Pahu. She has been transferred to a new breeding facility in Kelian, Indonesia. This effort was seen as extremely important and the rhino was given escort by the Indonesian police who helped to clear the mudslides on the way with bulldozers. As far as experts can tell, Pahu does seem to be reproductively healthy. She is doing well in her new home, and we can all keep our fingers crosses for her to have company soon. Pahu’s capture shows that there are other rhinos still roaming in Kalimantan’s forests and that in turn gives hope for the animal species future. Experts say that the world needs to be laser-focused on saving the remaining 80 Sumatran rhinos, using a combination of intensive protection and captive breeding, and working with local people to instill pride that the rhino is part of their biological heritage. “This is a battle we cannot afford to lose.”

 

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How does a digital clock turn on the oven?

When your clock radio starts playing music first thing in the morning, or the oven automatically comes on to cook a meal, the switch has probably been operated by a digital clock.

At the heart of the switch is a quartz crystal which vibrates at a fixed frequency when connected to a source of electrical power – battery or mains. The vibrations produce regular electrical pulses, which travels through circuits in a microchip to operate the digits on the clock.

The switch also has a memory, in the form of a microprocessor, which stores the time when the radio, oven or central heating system has to be turned on. The microprocessor constantly compares the stored time with the real time as measured by the clock.

When the turning on time comes, it sets off a low-voltage electronic signal. This signal is amplified by a transistor circuit and flows through a relay, an electronic device in which a small current causes a metal contact to move, switching on the main current.

 

Picture Credit : Google

Why racing cars have smooth tyres?

Car tyres are not just cushions for the wheels. They are there to give the car a good grip on slippery roads, and stop it sliding about when braking or cornering.

The tread pattern running all round the tyre has thin cuts (known as sipes) in the rubber to sponge up surface water, and zigzag channels to pump the water out behind as the car rolls forward. On a wet road, a tyre has to move more than 1 gallon (5 litres) of water a second to give an adequate grip.

On a perfectly dry road, the treads are not needed. A smooth tyre gives the greatest possible area of contact with the road. But if the smooth tyres are used in wet weather, the film of water on the road builds up in front of them and underneath them and actually lifts them and off the road surface – this is known as aquaplaning. When aquaplaning occurs, the driver loses control.

Most cars have to function in all weathers, so must have tyre treads, but racing cars make comparatively few outings a year. If the track is dry, they run on smooth tyres, called slicks, to get the best grip on the roads. The extra wide tyres and wheels give more grip that the average cars. In wet weather, however, the slicks have to be changed for treaded tyres.

 

Picture Credit : Google