POWER September 2014 - 68

RENEWABLES
2. Big steam. Calpine's Sonoma 3 plant is one of 22 geothermal plants that make up The
Geysers field in California. Courtesy: Stepheng3/Wikipedia
difficult. Geothermal units require considerable
upfront capital and long lead times. The
U.S. geothermal market is developing slowly,
he said, because it is " driven by state policy
more than national policy. "
That distinguishes the U.S. from most of
the rest of the world, where electrical systems
are national and most often driven by
central government policies and mandates.
At the federal level in the U.S., said
Gawell, " the production tax credit was
the 'one big thing.' But now the tax credits
are gone for everything but solar, " so
state policies have become the key to the
future for geothermal projects. The legal
authority for federal corporate tax credits
for wind, geothermal, and biomass expired
last year, and Congress has been unable to
renew them.
The primacy of state policy for geotherfornia's
restructured energy supply market.
In the late 1990s, projects to deliver municipal
wastewater to recharge the aquifer at
The Geysers increased the project's capacity
from a low point of about 1,000 MW in
the early part of the century to some 1,500
MW currently.
Over the past nearly 40 years, the U.S.
Department of Energy has devoted substantial
sums to geothermal research and development,
several billions of dollars by the
estimates from various groups including
the congressional Government Accountability
Office. (For more about various geothermal
technologies, see the sidebar " Defining
Geothermal Technologies " .) U.S. geothermal
projects have increased in numbers and
overall capacity over the years, particularly
in the volcanic regions of the Western U.S.
The resources remain rich. The GEA recently
reported that the economics of geothermal
energy are positive, debunking some conventional
wisdom.
" Geothermal power is sometimes misconstrued
to be an expensive source of electricity, "
said the GEA's June 2014 report,
" Economic Costs and Benefits of Geothermal
Power. " " While it is true geothermal
plants require a significant amount of startup
capital and some government assistance
in the earliest phases of exploration, the
overall capital costs and operating costs of
geothermal power are significantly lower
than many other technologies. " Geothermal
plants, notes the GEA, have no fuel costs,
low operation and maintenance expenses,
feature a 30-year lifetime, and are able to
produce baseload power and follow load,
unlike solar and wind generation.
What's the Roadblock?
What accounts for the lagging U.S. performance
in developing new geothermal projects?
In an interview, Karl Gawell, the GEA's
executive director, told POWER that the
complexity of the U.S. power sector, which
is based on largely state-regulated markets
with many moving parts, makes development
Defining Geothermal Technologies
Three technologies characterize geothermal
projects. These are:
■ Dry Steam. These are the oldest and
simplest. They draw steam from the
earth at 150C or higher to turn steam
turbine generators.
■ Flash Steam. These plants move deep,
high-temperature, pressurized water
from underground into lower-pressure
tanks, where the water flashes into
steam to turn a turbine.
68
■ Binary Geothermal. These plants can use
water at much lower temperatures, as
low as about 60C, in a heat exchanger
with another fluid that has a much
lower boiling point than water. The secondary
fluid then flashes to a gaseous
state and can drive turbines.
Under development are technologies that
will use hydraulic fracturing of the geothermal
rock formations to extract greater
amounts of energy for power generation.
www.powermag.com
mal is playing out today in California. The
state has the greatest concentration of geothermal
power and considerable untapped
resources. Regulators and legislators in the
Golden State are considering how to deal
with a power supply system, run by the California
Independent System Operator and
driven by the state's long-standing preference
for wind and solar, that is discounting
diversity of generating technologies and the
need for reliability services. That translates
into a bias against geothermal.
" It's really complicated when you start
looking at the cost of firming variable resources, "
says the GEA's Gawell. Among
the complexities are California's aggressive
renewables portfolio standard (RPS) aiming
for 33% of generation coming from renewables,
the state's rapid retreat from coal (from
any source, anywhere), and the unexpectedly
early closure of the two-unit San Onofre nuclear
station.
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Too Much Solar?
Last January, the consulting firm Energy and
Environmental Economics (E3) completed a
study for the state's five largest electric utilities
(Los Angeles Department of Water and
Power, PG&E, Sacramento Municipal Utilities
District, San Diego Gas & Electric, and
Southern California Edison), " Investigating
a Higher Renewables Portfolio Standard in
California, " looking at the implications of a
50% RPS.
The E3 report found that too much generation
as a result of the penetration of solar
power in the state is likely to lead to " some
level of renewable resource curtailment " in
order to " avoid overgeneration and to manage
net load ramps. " The study found that the
highest-cost generating portfolio that would
meet the 50% level " is one that relies extensively
on rooftop solar photovoltaic systems. "
POWER | September 2014
http://www.powermag.com
POWER September 2014

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