| Dear
EarthTalk: How are heating, cooling and electricity
produced by geothermal energy? I don’t understand
how it works.
-- Delano Stewart, Wyandanch, NY
| |
A
utility-grade geothermal energy plant in Iceland,
which derives 26.5 percent of its electricity needs
from the technology. Here in the U.S., where geothermal
is in its infancy, the Obama administration has set
aside $750 million for geothermal development, and
Congress has allocated $129 million to the Department
of Energy for various geothermal programs.
© Gretar Ivarsson |
The
term “geothermal” is derived from the Greek
words for Earth (geo) and heat (therme). In essence geothermal
energy is power harnessed from the Earth itself. Heat from
the Earth’s core, which averages about 6,650 degrees
Fahrenheit, emanates out toward the planet’s surface.
Heated springs and geysers up to three miles underground
can be accessed by special wells that bring the hot water
(or steam from it) up to the surface where it can be used
directly for heat or indirectly to generate electricity
by powering rotating turbines. Since the water under the
Earth’s surface is constantly replenished, and the
Earth’s core will continue to generate heat indefinitely,
geothermal power is ultimately clean and renewable.
Today
there are three main methods for harvesting utility-grade
geothermal energy: dry steam, flash steam and binary-cycle.
The dry steam process brings steam up directly from below
to drive turbines that power electricity generators. Flash
steam plants bring the hot water itself up from below; it
is then sprayed into a tank to create steam to drive the
turbines. These two methods are the most common, generating
hundreds of megawatts of electricity across the American
West, Europe and elsewhere. But expansion is limited as
these plants only work in tectonic regions where it is easier
to access ground heated water.
The
binary-cycle technology extracts close-to-the surface warm
(not necessarily hot) water and combines it with a second
(“binary”) fluid, like butane or pentane, which
has a low boiling point. This fluid is then pumped through
a heat exchanger, where it is vaporized and sent through
a turbine before being recycled back into the system. Binary-cycle
geothermal plants already pump out dozens of megawatts of
electricity in California, Nevada and Hawaii, among other
places.
But
geothermal isn’t just for utilities. Homeowners looking
to go green and lower their utility bills can install a
residential system, essentially a scaled-down version of
the binary-cycle system. A series of pipes is installed
underground. Water circulating in the loop is heated naturally
underground and then transferred to a heat exchanger which
concentrate the energy and releases it inside the home as
heat. In summer and in warmer climates, the process is reversed
to fill the home with geothermal-cooled air.
Geothermal
has its drawbacks. For homeowners, it may be hard to justify
the up-front expense of $7,500 or more to install a system,
though the IRS now offers tax credits for 30 percent of
the cost. At the utility level, geothermal plants are costly
to build and operate. And finding a suitable site requires
digging expensive test wells with no guarantee of hitting
a productive underground hot spot. Nevertheless, analysts
expect utility-grade geothermal capacity to nearly double
over the next just six years. The Obama administration has
set aside $750 million for geothermal development, and Congress
has also been generous, allocating $129 million to the Department
of Energy for various geothermal programs.
Geothermal
may be in its infancy in the U.S., but it is a big player
in Iceland, which derives 26.5 percent of its electricity
needs from geothermal, and in New Zealand, which gets 10
percent of its electricity likewise.
CONTACTS:
DOE
Consumer Energy Tax Incentives; Geothermal
Energy Association.
Dear
EarthTalk: Apparently boxed wine (instead of
bottled) is becoming all the rage for environmental reasons.
What are the eco-benefits of boxed wine over bottled?
-- Justin J., Los Angeles, CA
| |
There
are no bottles in these boxes of wine -- just wine
and the plastic pouch that holds it. Boxing instead
of bottling wine saves half the shipping weight (and
associated carbon emissions) and keeps the product
fresher longer.
© Bota Box |
With more and
more wineries offering organic varieties to lower their
eco-footprint, it’s no surprise that they’re
looking at the environmental impacts of their packaging
as well. The making of conventional glass bottles (and the
corks that cap them) uses significant quantities of natural
resources and generates considerable pollution. According
to the U.S. Environmental Protection Agency, the process
of manufacturing glass not only contributes its share of
greenhouse gas emissions but also generates nitrogen oxides,
sulfur dioxide and tiny particulates that can damage lung
tissue when breathed in.
Beyond manufacturing,
the transport of wine in glass bottles across the country
and around the world also takes its environmental toll.
According to wine writer Tyler Colman, upwards of 90 percent
of American wine is produced on the West Coast, but then
shipped to the East Coast where the majority of wine consumers
live. Trucking all these heavy glass bottles generates a
much larger carbon footprint, ounce-for-ounce than the transportation
of much lighter boxed wine. Almost half the weight of an
ordinary case of wine comes from the bottles; about 95 percent
of the weight of a case of boxed wine is the wine itself.
“A standard
wine bottle holds 750 milliliters of wine and generates
about 5.2 pounds of carbon-dioxide emissions when it travels
from a vineyard in California to a store in New York,”
reports Colman, who blogs at DrVino.com. “A 3-liter
box generates about half the emissions per 750 milliliters.”
He concludes that switching to wine in a box “for
the 97 percent of wines that are made to be consumed within
a year” would reduce greenhouse gas emissions by about
two million tons, or the equivalent of removing 400,000
cars from the roads.
According to
the Wine Group, the third largest wine company in the world
by volume and a big advocate for switching away from glass
bottles, there are other advantages to boxed wine (which
typically includes a plastic bag within a cardboard box).
The vacuum packaging of boxed wines allows the contents
to stay fresh for up to six weeks in the fridge once the
seal is broken and the first glass has been poured. The
Wine Group has launched the “Better Wines Better World”
website in an attempt to curry public favor for technologically
advanced, environmentally friendly and economically practical
boxed wines.
Still, despite
the benefits, boxed wine may still be a tough pill to swallow
for many wine connoisseurs still bent on tradition. “Even
those traditionalists who are coming around to the idea
that maybe screw caps are fine for some wines, balk at the
idea of a cellar full of cardboard boxes,” says wine
writer and vineyard owner Lee Asbell. “It is difficult
to imagine how wine service at fine-dining establishments
would handle such a change.” For now, boxed wine is
still the domain of cheaper brands. But that could all change
as more and more wine makers and drinkers take up the mantle
of saving the Earth.
CONTACTS:
Better
Wines Better World; DrVino. |
