Sabtu, 14 November 2009
Rabu, 21 Oktober 2009
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How Tidal Power Plants Work
There are three basic ways we can harnass tidal power .
By Mary Bellis, About.com
The power of the rise and fall of the sea level or tidal power, can be harnessed to generate electricity.
Tidal Power
Tidal power traditionally involves erecting a dam across the opening to a tidal basin. The dam includes a sluice that is opened to allow the tide to flow into the basin; the sluice is then closed, and as the sea level drops, traditional hydropower technologies can be used to generate electricity from the elevated water in the basin. Some researchers are also trying to extract energy directly from tidal flow streams.
The energy potential of tidal basins is large — the largest facility, the La Rance station in France, generates 240 megawatts of power. Currently, France is the only country that successfully uses this power source. French engineers have noted that if the use of tidal power on a global level was brought to high enough levels, the Earth would slow its rotation by 24 hours every 2,000 years.
Tidal energy systems can have environmental impacts on tidal basins because of reduced tidal flow and silt buildup.
3 Ways of Using the Tidal Power of the Ocean
There are three basic ways to tap the ocean for its energy. We can use the ocean's waves, we can use the ocean's high and low tides, or we can use temperature differences in the water.
1 Wave Energy
Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. In this simple example, (illustrated to the right) the wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator.
When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
This is only one type of wave-energy system. Others actually use the up and down motion of the wave to power a piston that moves up and down inside a cylinder. That piston can also turn a generator.
Most wave-energy systems are very small. But, they can be used to power a warning buoy or a small light house.
2 Tidal Energy
Another form of ocean energy is called tidal energy. When tides comes into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant.
In order for this to work well, you need large increases in tides. An increase of at least 16 feet between low tide to high tide is needed. There are only a few places where this tide change occurs around the earth. Some power plants are already operating using this idea. One plant in France makes enough energy from tides to power 240,000 homes.
3 Ocean Thermal Energy
The final ocean energy idea uses temperature differences in the ocean. If you ever went swimming in the ocean and dove deep below the surface, you would have noticed that the water gets colder the deeper you go. It's warmer on the surface because sunlight warms the water. But below the surface, the ocean gets very cold. That's why scuba divers wear wet suits when they dive down deep. Their wet suits trapped their body heat to keep them warm.
Power plants can be built that use this difference in temperature to make energy. A difference of at least 38 degrees Fahrenheit is needed between the warmer surface water and the colder deep ocean water.
Using this type of energy source is called Ocean Thermal Energy Conversion or OTEC. It is being used in both Japan and in Hawaii in some demonstration projects.
There are three basic ways we can harnass tidal power .
By Mary Bellis, About.com
The power of the rise and fall of the sea level or tidal power, can be harnessed to generate electricity.
Tidal Power
Tidal power traditionally involves erecting a dam across the opening to a tidal basin. The dam includes a sluice that is opened to allow the tide to flow into the basin; the sluice is then closed, and as the sea level drops, traditional hydropower technologies can be used to generate electricity from the elevated water in the basin. Some researchers are also trying to extract energy directly from tidal flow streams.
The energy potential of tidal basins is large — the largest facility, the La Rance station in France, generates 240 megawatts of power. Currently, France is the only country that successfully uses this power source. French engineers have noted that if the use of tidal power on a global level was brought to high enough levels, the Earth would slow its rotation by 24 hours every 2,000 years.
Tidal energy systems can have environmental impacts on tidal basins because of reduced tidal flow and silt buildup.
3 Ways of Using the Tidal Power of the Ocean
There are three basic ways to tap the ocean for its energy. We can use the ocean's waves, we can use the ocean's high and low tides, or we can use temperature differences in the water.
1 Wave Energy
Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. In this simple example, (illustrated to the right) the wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator.
When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
This is only one type of wave-energy system. Others actually use the up and down motion of the wave to power a piston that moves up and down inside a cylinder. That piston can also turn a generator.
Most wave-energy systems are very small. But, they can be used to power a warning buoy or a small light house.
2 Tidal Energy
Another form of ocean energy is called tidal energy. When tides comes into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant.
In order for this to work well, you need large increases in tides. An increase of at least 16 feet between low tide to high tide is needed. There are only a few places where this tide change occurs around the earth. Some power plants are already operating using this idea. One plant in France makes enough energy from tides to power 240,000 homes.
3 Ocean Thermal Energy
The final ocean energy idea uses temperature differences in the ocean. If you ever went swimming in the ocean and dove deep below the surface, you would have noticed that the water gets colder the deeper you go. It's warmer on the surface because sunlight warms the water. But below the surface, the ocean gets very cold. That's why scuba divers wear wet suits when they dive down deep. Their wet suits trapped their body heat to keep them warm.
Power plants can be built that use this difference in temperature to make energy. A difference of at least 38 degrees Fahrenheit is needed between the warmer surface water and the colder deep ocean water.
Using this type of energy source is called Ocean Thermal Energy Conversion or OTEC. It is being used in both Japan and in Hawaii in some demonstration projects.
Watermelon Juice May Be Next "Green" Fuel
John Roach
for National Geographic News
August 28, 2009
Watermelon, the quintessential summer fruit, may soon be helping to fuel your car as well as your picnic guests.
According to a new U.S. government study, juice from unwanted watermelons could be a promising new source for making the biofuel ethanol.
Up to a fifth of all watermelons grown each year have odd shapes or scarred rinds that turn off consumers, said study co-author Wayne Fish, a chemist with the Agricultural Research Service in Lane, Oklahoma.
Instead of picking the fruit, farmers leave these reject melons on the vine.
"If you figure a field of watermelon may yield somewhere between 60 and 100 tons per acre of watermelon, a fifth of that can be substantial," Fish said.
When he and colleagues were experimenting with extracting antioxidant compounds from watermelon juice, they realized the waste stream of sugary fluids could be a source of ethanol.
(Compare the costs and benefits of different biofuels.)
Mobile Homebrew
The researchers brewed several experimental batches of the fruity fuel in the lab and optimized the process to produce about 23 gallons (87 liters) of ethanol from an acre's worth of the unused fruit.
"For average-size growers that have 300 to 1,000 acres [121 to 405 hectares], they may just keep the ethanol themselves and use it in their own production," Fish said.
Larger farms could even produce enough fuel to sell.
(Related: "Alcohol, Feces, Carcasses Fuel 'Green' Vehicles in Sweden.")
However, it doesn't make economic sense to haul the unwanted watermelons to a processing facility. Rather, Fish envisions mobile breweries that go from farm to farm.
"In terms of the actual process that goes on, it is no different than making homebrew," he said, except on a larger scale and with a few special laboratory tweaks.
Watermelon Beer?
When brewing the watermelon biofuel, the researchers were focused on its energy potential, not flavor. But they couldn't resist sampling the brew.
"It's not going to kill you, for goodness sake," Fish said.
Their process tended to produce fusel oils, which give alcohols an "off" flavor.
"Don't expect to see any watermelon beer at your local tavern anytime soon," Fish said, "at least as produced at Lane, Oklahoma."
Findings published August 26 in the journal Biotechnology for Biofuels.
John Roach
for National Geographic News
August 28, 2009
Watermelon, the quintessential summer fruit, may soon be helping to fuel your car as well as your picnic guests.
According to a new U.S. government study, juice from unwanted watermelons could be a promising new source for making the biofuel ethanol.
Up to a fifth of all watermelons grown each year have odd shapes or scarred rinds that turn off consumers, said study co-author Wayne Fish, a chemist with the Agricultural Research Service in Lane, Oklahoma.
Instead of picking the fruit, farmers leave these reject melons on the vine.
"If you figure a field of watermelon may yield somewhere between 60 and 100 tons per acre of watermelon, a fifth of that can be substantial," Fish said.
When he and colleagues were experimenting with extracting antioxidant compounds from watermelon juice, they realized the waste stream of sugary fluids could be a source of ethanol.
(Compare the costs and benefits of different biofuels.)
Mobile Homebrew
The researchers brewed several experimental batches of the fruity fuel in the lab and optimized the process to produce about 23 gallons (87 liters) of ethanol from an acre's worth of the unused fruit.
"For average-size growers that have 300 to 1,000 acres [121 to 405 hectares], they may just keep the ethanol themselves and use it in their own production," Fish said.
Larger farms could even produce enough fuel to sell.
(Related: "Alcohol, Feces, Carcasses Fuel 'Green' Vehicles in Sweden.")
However, it doesn't make economic sense to haul the unwanted watermelons to a processing facility. Rather, Fish envisions mobile breweries that go from farm to farm.
"In terms of the actual process that goes on, it is no different than making homebrew," he said, except on a larger scale and with a few special laboratory tweaks.
Watermelon Beer?
When brewing the watermelon biofuel, the researchers were focused on its energy potential, not flavor. But they couldn't resist sampling the brew.
"It's not going to kill you, for goodness sake," Fish said.
Their process tended to produce fusel oils, which give alcohols an "off" flavor.
"Don't expect to see any watermelon beer at your local tavern anytime soon," Fish said, "at least as produced at Lane, Oklahoma."
Findings published August 26 in the journal Biotechnology for Biofuels.
Sabtu, 17 Oktober 2009
Kamis, 24 September 2009
NAHJUL BALAGHAH
KESABARAN NABI MUSA
Dalam Khutbah ke-159, Imam Ali menceritakan kepribadian Nabi Musa as. Beliau mengatakan, “Apabila kalian menghendaki,sebagai contoh kedua, saya akan menceritakan kepada kalian mengenai Musa Kalimullah (orang yang diajak bicara langsung oleh Allah), ketika beliau berkata,”Ya Tuhanku! Sesungguhnya aku sangat memerlukan suatu kebaikan yang engkau turunkan kepadaku.’(AL-Qashash-24). Demi Allah, ia hanya meminta kepada-Nya roti untuk disantap. Ia telah terbiasamakan tetumbuhan bumi sehingga hijau dedaunan dapat dilihat dari kulit halus perutnya, karena tipisnya daging yang membalutnya.”
Dalam riwayat lainnya disebutkan, “Padasuatu hari, Nabi Musa mengatakan kepada Allah,’Wahai Tuhanku, aku merasa lapar.’ Allah menjawab,Aku mengetahui rasa laparmu.’NabiMusa Berkata, ‘Berikanlaha aku makanan dari sisi-Mu.”
Diantara firman Allah yang diwahyukan kepada Nabi Musa berbunyi: “Wahai Musa, orang miskin adalah orang yang tidak mempunyai sesembahan seperti Aku. Orang sakit adalah orang yang tidak mempunyai dokter seperti Aku. Dan orang asing adalah orang yang tidak mempunyai penghiburseperti aku. Wahai Musa, senanglah dengan roti kering yang yang telah aku berikan kepada Anda.
Ketika dunia menghampiri Anda, katanlah,’Inna lillahi wa inna ilaihi rajiun (sesunggguhnya kita milik Allah dan hanya kepada-Nya kita akan kembali).’ Ketika dunia berhias untuk menggoda Anda, maka katankanlah,”Selamat bagi orang-orang yang berbuat kebajikan”. Wahai Musa, Janganlah merasa heran dengan (Harta kekayaan) yang telah Allah berikan kepada Fir’aun. Ia akan mendapatkan kesusahan melalui kehidupan dunianya
NAHJUL BALAGHAH
Dalam Khutbah ke-159, Imam Ali menceritakan kepribadian Nabi Musa as. Beliau mengatakan, “Apabila kalian menghendaki,sebagai contoh kedua, saya akan menceritakan kepada kalian mengenai Musa Kalimullah (orang yang diajak bicara langsung oleh Allah), ketika beliau berkata,”Ya Tuhanku! Sesungguhnya aku sangat memerlukan suatu kebaikan yang engkau turunkan kepadaku.’(AL-Qashash-24). Demi Allah, ia hanya meminta kepada-Nya roti untuk disantap. Ia telah terbiasamakan tetumbuhan bumi sehingga hijau dedaunan dapat dilihat dari kulit halus perutnya, karena tipisnya daging yang membalutnya.”
Dalam riwayat lainnya disebutkan, “Padasuatu hari, Nabi Musa mengatakan kepada Allah,’Wahai Tuhanku, aku merasa lapar.’ Allah menjawab,Aku mengetahui rasa laparmu.’NabiMusa Berkata, ‘Berikanlaha aku makanan dari sisi-Mu.”
Diantara firman Allah yang diwahyukan kepada Nabi Musa berbunyi: “Wahai Musa, orang miskin adalah orang yang tidak mempunyai sesembahan seperti Aku. Orang sakit adalah orang yang tidak mempunyai dokter seperti Aku. Dan orang asing adalah orang yang tidak mempunyai penghiburseperti aku. Wahai Musa, senanglah dengan roti kering yang yang telah aku berikan kepada Anda.
Ketika dunia menghampiri Anda, katanlah,’Inna lillahi wa inna ilaihi rajiun (sesunggguhnya kita milik Allah dan hanya kepada-Nya kita akan kembali).’ Ketika dunia berhias untuk menggoda Anda, maka katankanlah,”Selamat bagi orang-orang yang berbuat kebajikan”. Wahai Musa, Janganlah merasa heran dengan (Harta kekayaan) yang telah Allah berikan kepada Fir’aun. Ia akan mendapatkan kesusahan melalui kehidupan dunianya
NAHJUL BALAGHAH
Sirah
Hasan menuturkan :
Setelah Rasulullah S.A.W & Abu Bakar ra pergi meninggalkan goa, setiap orang yang bertemu dengan keduanya dan mengenalkan Abu Bakar selalu bertanya," Siapa yang bersamamu ini, hai Abu Bakar?". Adapun Abu Bakar selalu menjawab," Dia adalah penunjuk jalanku."
Sungguh Abu Bakar berkata benar.
Setelah Rasulullah S.A.W & Abu Bakar ra pergi meninggalkan goa, setiap orang yang bertemu dengan keduanya dan mengenalkan Abu Bakar selalu bertanya," Siapa yang bersamamu ini, hai Abu Bakar?". Adapun Abu Bakar selalu menjawab," Dia adalah penunjuk jalanku."
Sungguh Abu Bakar berkata benar.
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