Putting Plants to Work

Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels for decades. But plants are the real experts: They’ve been using sunlight as an energy source for billions of years.

Ceils in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide, and water into¹ sugars and starches, stored energy that the plants can use. This conversion process is called photosynthesis. Unfortunately, unless you’re a plant, it’s difficult and expensive to convert sunlight into storable energy. That’s why scientists are taking a closer look at exactly how plants do it.

Some scientists are trying to get plants, or biological cells that act like plants, to work as miniature photosynthetic power stations. For example, Mafia Ghirardi of the National Renewable Energy Laboratory in Golden, Colo.², is working with green algae³. She’s trying to trick them into producing hydrogen⁴ instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficiently, the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity.

The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthesis, plants normally make sugars or starches. “But under certain conditions, a lot of algae are able to use the sunlight energy not to store starch, but to make hydrogen,” Ghirardi says. For example, algae will produce hydrogen in an air free environment. It’s the oxygen in the air that prevents algae from making hydrogen most of the time.

Working in an air free environment, however, is difficult. It’s not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate from the environment that the algae grow in, they will make hydrogen instead of sugars, even when air is present.

Unfortunately, removing the sulfate also makes the algae’s cells work very slowly, and not much hydrogen is produced. Still, the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work, they may be able to speed the cells" activity and produce larger quantities of hydrogen.

The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says, and they can grow almost anywhere: “You can grow them in a reactor, in a pond. You can grow them in the ocean. There’s a lot of flexibility in how you can use these organisms.”

 

词汇:

panel /5pAnl/ n.嵌板，发热板，仪器板  

starch /stB:tF/ n. 淀粉

miniature /5minjEtFE/ adj.口巧．微型的

sulfate /5sQlfeit/ n. 硫酸盐，硫酸酯

carbon dioxide 二氧化碳  

photosynthesis /7fEutEu5sinWEsis/ n. 光合作用

algae /5AldVi:/ n. 水藻，海藻  

 

注释:    

1. convert … into…：将……转换为 ……     

2. Colo.：Colorado，（美国科罗拉多州）的缩写形式  

3. Green algae: 绿藻       

4.trick them into producing hydrogen: 想方设法使它们产生氢。 trick作为动词，有 “欺骗、哄骗 ”的意思，但是在这里的意思是 “设法”或“采取措施 ”。

What does the writer say about plants concerning solar energy?

A:Plants are "the real experts in producing solar energy. B:Plants have been used to produce solar energy. C:Plants have been using solar energy for billions of years. D:Plants have been a source of solar energy.

Passage 5
The energy which the sun radiates goes in every direction, and only a minute part of it falls on the earth. Even so, it represents power of about 5,000,000 horsepower (马力)per square mile per day; the sun gives us as much energy every minute as mankind utilizes in a year. At present, we use this energy in directly, and it is our final source of power. Coal represents the chemical action of the sun on green plants thousands of years ago. Water power results from the rain formed by vapor which comes from the evaporation of power. Coal represents the rain formed by vapor which comes from the evaporation of water under the sunshine. Even windmills operate because of air currents set in motion by the different heating affects of the sun in different places. Some day, through chemistry or some type of solar engine, we shall harness this great source of energy more directly. Already a scientist has worked out an engine, surprisingly efficient, in with the sun’ s rays are concentrated through mirrors on a tube of water to create steam.

Which of the following statements is NOT true（）

A:Even windmill' s action depends on the sun. B:The sun produces enormous energy for man to make use of. C:Some day man will be able to utilize 100 % of the solar energy that gets to the earth. D:The sun produces different heating effects in different places.

Better Solar Energy Systems: More Heat, More Light Solar photovoltaic（光伏的）thermal energy systems,or PVTs, generate both heat and electricity, but until now they haven’t been very good at the heat-generating part compared to a stand-alone solar thermal collector. That’s because they operate at low temperatures to cool crystalline（晶体的）silicon solar cells, which lets the silicon generate more electricity but isn’ta very efficient way to gather heat. That’s a problem of economics. Good solar hot-water systems can harvest much more energy than a solar-electric system at a substantially lower cost. And it’s also a space problem: photovoltaic cells can take up all the space on the roof, leaving little room for thermal applications. In a pair of studies, Joshua Pearce, an associate professor of materials science and engineering, has devised a solution in the form of a better PVT made with a different kind of silicon. His research collaborators are Kunal Girotra from Thin Silicon in California and Michael Pathak and Stephen Harrison from Queen’s University, Canada. Most solar panels are made with crystalline silicon, but you can also make solar cells out of amorphous（非晶体的）silicon, commonly known as thin-film silicon. They don’t create as much electricity, but they are lighter, flexible, and cheaper. And, because they require much less silicon,they have a greener footprint. Unfortunately, thin-film silicon solar cells are vulnerable to some bad-news physics in the form of the Staebler-Wronski effect. "That means that their efficiency drops when you expose them to light—pretty much the worst possible effect for a solar cell," Pearce explains,which is one of the reasons thin-film solar panels make up only a small fraction of the market. However, Pearce and his team found a way to engineer around the Staebler-Wronski effect by incorporating thin-film silicon in a new type of PVT. You don’t have to cool down thin-film silicon to make it work. In fact, Pearce’s group discovered that by heating it to solar-thermal operating temperatures, near the boiling point of water, they could make thicker cells that largely overcame the Staebler-Wronski effect. When they applied the thin-film silicon directly to a solar thermal energy collector, they also found that by baking the cell once a day, they boosted the solar cell’s electrical efficiency by over 10 percent. PVTs are not efficient in

A:creating electricity. B:cooling silicon solar cells. C:generating heat. D:powering solar thermal collectors.

Soot（煤烟灰）and Snow: a Hot Combination New reasearch from NASA scientists suggests emissions of black soot after the way sunlight reflects off snow. According to a computer simulation, black soot may be responsible for 25 percent of observed global warming over the past century. Soot in the higher latitudes（维度）of the Earth, where ice is more common, absorbs more of the sun’s energy and warmth than an icy, white background. Dark-colored black carbon, or soot, absorbs sunlight, while lighter colored ice reflects sunlight. Soot in areas with snow and ice may play an important role in climate change. Also, if snow and ice covered areas begin melting, the warming effect increase, as the soot becomes more concentrated on the snow surface."This provides a positive feedback, as glaciers and ice sheets melt, they tend to get even dirtier." said Dr. James Hansen, a researcher at NASA’s Goddard Institute for Space Studies, New York. Hansen found soot’s effect on snow albedo（反照率）, which may be contributing to trends toward early springs in the Northern Hemisphere, such as thinninbg Arctic sea ice and melting glaciers permafrost. Soot also is believed to play a role in changes in the atmosphere above the oceans and land. "Black carbon reduces the amount of energy reflected by snow back into space, thus heading the snow surface more than if there were no black carbon, " Hansen said. Soot’s increased absorption of solar energy is especially effecntive in warming the world’s climate." This forcing is unusually effective, causing twice as much global warming as a carbon-dioxide forcing of the same magnitude." Hansen noted. Hansen cautioned, although the role of soot in altering global climate is substantial, it does not alter the fact that greenhouse gases are the primary cause of climate warming during the past century. Such gases are expected to bi the largest climate forcing for the rest of the century. The researchers found that observed warming in the Northern Hermisphere was large in the winter and spring at middle and high latitudes. These observations were coherent with the researchers’ climate model situations, which showed some of the largest warming effects occurred when there were heavy snow cover and sufficient sunlight."This forcing" in Paragraph 5 refers to?

A:sun’s heating on snow surface． B:soot’s increased absorption of solar energy． C:carbon-dioxide’s warming effect． D:snow’s increased reflection of sunlight．

Central heating became popular only after the Civil War. Typically, coal-burning furnaces (火炉) fueled the early systems. Natural gas had developed into the leading fuel by 1960. Its acceptance resulted in part from its wide uses. Because it comes primarily from U.S. and Canadian fields, natural gas is also less vulnerable (脆弱的) than oil is to War. Oil remains the most important fuel in a few areas, such as New England.
Electric heating dominates most areas with mild winters and cheap electricity, including the South and the Northwest. It was made popular at least in the South by the low cost of adding electric heating to new houses built with air-conditioning. Bottled gas, which is somewhat more expensive than utility gas, is the fuel of choice in rural areas not served by utility pipelines. Wood is the leading heating fuel in just a few rural counties.
Home heating, which accounts for less than 7 percent of all energy consumed in the U.S., has had a commendable (值得赞扬的) efficiency record: from 1978 to 1997, the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent increase in the number of housing units and an increase in house size. The U.S. Department of Energy, however, forecasts that energy used in home heating will rise by 14 percent over the next two decades. That rise is small considering an expected 21 percent increase in the number of houses and the trend toward larger houses.
Natural gas and electricity will probably dominate the home heating market for the next two decades. Solar (太阳的) heating never became popular because of cost and limited winter sunlight in most areas; in 2000 only 47,000 homes relied on it.
Which of the following statements is NOT true, according to the article

A:Natural gas comes partly from Canadian fields. B:Bottled gas is more expensive than utility gas. C:Equipment for home heating has been considerably improved. D:Solar heating dominated America in 2000.

Home Heating
Central heating became popular only after the Civil War. Typically, coal-burning furnaces (火炉) fueled the early systems. Natural gas had developed into the leading fuel by 1960. Its acceptance resulted in part from its wide uses. Because it comes primarily from U.S. and Canadian fields, natural gas is also less vulnerable (脆弱的) than oil is to war. Oil remains the most important fuel in a few areas, such as New England.
Electric heating dominates most areas with mild winters and cheap electricity, including the South and the Northwest. It was made popular at least in the South by the Iow cost of adding electric heating to new houses built with air-conditioning. Bottled gas, which is somewhat more expensive than utility gas, is the fuel of choice in rural areas not served by utility pipelines. Wood is the leading heating fuel in just a few rural counties.
Home heating, which accounts for less than 7 percent of all energy consumed in the U.S., has had a commendable (值得赞扬的) efficiency record: from 1978 to 1997, the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent increase in the number of housing units and an increase in house size. The U. S. Department of Energy, however, forecasts that energy used in home heating will rise by 14 percent over the next two decades. That rise is small considering an expected 21 percent increase in the number of houses and the trend toward larger houses.
Natural gas and electricity will probably dominate the home heating market for the next two decades. Solar (太阳的) heating never became popular because of cost and limited winter sunlight in most areas; in 2000 only 47, 000 homes relied on it.
Which of the following statements is NOT true, according to the article

A:Natural gas comes partly from Canadian fields. B:Bottled gas is more expensive than utility gas. C:Equipment for home heating has been considerably improved. D:Solar heating dominated America in 2000.

{{B}}第二篇{{/B}}

Which of the following statements is NOT true, according to the article?

A:Natural gas comes partly from Canadian fields. B:Bottled gas is more expensive than utility gas. C:Equipment for home heating has been considerably improved. D:Solar heating dominated America in 2000.

第二篇 Home Heating Central heating became popular only after the Civil War. Typically, coal—burning furnaces(火炉)fueled the early systems．Natural gas had developed into the leading fuel by 1960.Its acceptance resulted in part from its wide uses．Because it comes primarily from U．S．and Canadian fields，natural gas is also less vulnerable(脆弱的)than oil is to War．Oil remains the most important fuel in a few areas．such as New England． Electric heating dominates most areas with mild winters and cheap electricity, including the South and the Northwest．It was made popular at least in the South by the low cost of adding electric heating to new houses built with air．conditioning．Bottled gas．which is somewhat more expensive than utility gas，is the fuel of choice in rural areas not served by utility pipelines．Wood is the leading heating fuel in just a few rural counties． Home heating，which accounts for less than 7 percent of a11 energy consumed in the U．S．，has had a commendable(值得赞扬的)efficiency record：from 1978 to 1997，the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent increase in the number of housing units and an increase in house size．The U．S．Department of Energy。however, forecasts mat energy used in home heating will rise by 14 percent over the next two decades．That rise is small considering an expected 2 1 percent increase in the number of houses and the trend toward larger houses． Natural gas and electricity will probably dominate the home heating market for the next two decades．Solar(太阳的)heating never became popular because of cost and limited winter sunlight in most areas；in 2000 only 47.000 homes relied on it． Which of the following statements is NOT true，according to the article?

A:Natural gas comes partly from Canadian fields． B:Bottled gas is more expensive than utility gas． C:Equipment for home heating has been considerably improved． D:Solar heating dominated America in 2000．