Ethanol, biodiesel, and wind power hog
the attention when it comes to
alternative energy these days. But a new
report finds there is enormous untapped
potential for geothermal energy, in
particular around the Pacific Rim, and
anywhere else there's been volcanic
activity.
Unlike solar or wind power, heat from
the rocks is always on. A recent report
from the Massachusetts Institute of
Technology, MIT, concludes that the
geothermal option has been undervalued
as a way of meeting future energy needs.
Geothermal power is at work in Boise,
Idaho, on the western slope of the Rocky
Mountains. Around town, furnaces are
gobbling up fuel to heat buildings and
keep occupants warm. But 55 downtown
buildings share a hidden secret: cheap
heat from deep beneath the earth.
Geothermal engineer Kent Johnson says
most people have no idea that is where
the warmth is coming from. "It's
interesting talking to people that I
know work downtown. I'll say, 'Oh, you
work in one of our buildings that is one
of our geothermal customers.' They go,
'Oh, really?'"
Idaho's capital city is home to the
oldest geothermal central heating system
in the U.S. The first distribution line
dates back more than a century. Johnson
says that after languishing for years,
the geothermal service is drawing
renewed interest, in part because it's
up to 30 percent cheaper. "Primarily
it's because the price of natural gas
has risen so much in the last three to
four years," he observes, "but I also
think there's more interest in renewable
energy, too."
The government-funded report from MIT
concluded that non-polluting geothermal
plants should become a bigger part of
America's energy portfolio. At present,
there are just a few other American
cities with geothermal utilities. Reno,
Nevada, is one. Susanville, California,
is another. Klamath Falls, Oregon,
installed geothermal heating coils under
downtown sidewalks to melt snow and ice.
A member of the expert panel that wrote
the MIT report, geothermal consultant
Susan Petty, says cities now using
geothermal provide just a taste of
what's possible. She admits that it's a
viable alternative only where the heat
source is very shallow. She gestures
toward the color-coded maps that cover
the walls of her Seattle office. They
show where hot rocks lie close to the
surface. But, she adds, "there are some
easy-to-do incremental improvements to
current technology that could bring an
awful lot of this energy into being
economic."
The MIT panel backs a new approach to
mining heat from the earth that can work
pretty much anywhere by injecting
surface water deep underground. Then you
drill a separate well nearby to
recapture that water, which is now
boiling hot. Petty says the resulting
steam can spin a power turbine before
being re-injected to start the cycle
over again. "We'll be able to manage
this flow so we don't lose this water,"
she explains. "And that was a really big
breakthrough because a lot of the high
temperature bodies of rock in the U.S.
are in the western U.S., where it's
sometimes very arid and there's not a
lot of water available."
There are two basic categories of
geothermal power. There's drilling
really deep for super-heated water to
use to make electricity. That's Petty's
interest. Then there's direct use of
moderately hot water that might lie
beneath a city or a business property.
That's actually more widely accessible.
The Flora Company of Boise uses the hot
water under its land to heat its
greenhouse and fishponds. The owners
drilled a 200-meter well to tap a
geothermal aquifer. Head grower Jayson
Grazel shows off trays of bedding plants
in the toasty warm greenhouse complex.
"We have a leg up," he says. "It really
saves on the bottom dollar versus paying
for gas or extra heat from various
ways." He estimates that using
geothermal energy cuts the company's
heating bill by 75 percent.
The warm water circulates under the
floor of the greenhouses or runs through
growing tables. It keeps the geraniums,
pansies and poppies happy. And the
grower, too. "The beauty of it is that
it goes back to the earth. It comes out
[of the greenhouse] the same way it goes
in, just a few degrees cooler."
The recent MIT study on geothermal
potential proposed a public investment
of $800 million over the next 15 years
to jump-start this energy sector. But
President Bush's proposed 2008 federal
budget does not include money for the
suggested geothermal surveying and test
drilling or technology prototypes. Other
countries are taking the lead on mining
deep geothermal deposits. France is
taking advantage of European Union
subsidies. In Australia, private
investors are shouldering the risk. |
|
在谈到替代能源的时候，乙醇、生物柴油和风力都是引人注意的项目，但是美国麻省理工学院的一项新报告指出，地热是一种有待开发、潜力无穷的能源，特别是在太平洋周围以及其他可能有火山爆发的地区。
和太阳能或者风力不同的是，地热随时都可以取用。麻省理工学院最近的一份报告做出结论说，在应付未来的能源需要方面，地热的价值被估计过低。
座落在洛基山西坡的爱达荷州首府波塞，由于气候寒冷，家家户户冬天都要消耗不少燃料，以保持室内温暖。但是，波塞市区的55栋建筑物，其中包括一家新的旅馆，都有一个共同的秘密，那就是：它们的暖气来自地下，而且费用低廉。波塞市的地热工程师约翰逊说：“我觉得和一些在城里工作的人谈话很有意思，我会说：‘你做事的那栋大楼是我们地热公用事业公司的顾客。’他们会说：‘噢，是真的嘛？’他们完全没有想到。”
波塞是美国历史最久的地热中央暖气系统的所在地，早在一个多世纪以前，就铺下第一条供应暖气的线路。约翰逊说，在没没无闻了多年之后，地热又再度引起人们的兴趣，一部份原因是地热比其他能源便宜30%。他说：“主要的原因是在过去三四年当中，天然气的价格上涨很多，但是我认为人们对替代能源也更感到兴趣。”
美国只有少数城市的公用事业利用地热，包括内华达州的雷诺和加利福尼亚州的苏珊维尔。俄勒岗州的布拉玛兹瀑布市在市区的人行道下面装设了地热暖气管，用来融化地面上的冰雪。
麻省理工学院的这份由政府资助的报告得出结论说，美国的能源应该有更大一部份由没有任何污染的地热发电厂供应。撰写报告的专门小组成员、地热顾问佩蒂说，目前对地热加以利用的城市为将来可能的发展做了一个开端。
佩蒂说：“只有少数地方地热来源在地下很浅的地方。其它地方目前对地热的利用可能并不符合经济效益。但是现有的技术可以很容易的做进一步的改善，在符合经济效益的条件下大量开发地热能源。”
佩蒂在西雅图的办公室的墙上挂着一些地图，以不同的颜色标识出哪些地方的热岩最接近地面。麻省理工学院的小组对一个在任何地方都能够开发地热的新方法予以支持，这个方法是把地面的水灌入地下，然后在附近凿一个井，收回在地下热岩石之间加热沸腾的水。佩蒂说，这样产生的水蒸气可以推动发电机，水还可以再灌入地下，循环使用。
佩蒂说：“我们可以保持水的循环使用，不会浪费，这的确是一大突破。因为很多炙热的地下岩石是在美国西部，而那里时常由于干旱而缺水。”
地热的利用基本上分为两种，一种是把水灌入地下高温的岩石之间，水会变成蒸气，推动发电机，这也是佩蒂在研究的。另外一种是对一个城市或者一个商业场所下面流过的天然温水直接加以利用，这种方法的应用范围更为广泛。 |
