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In the US State of Nevada, energy and environmental engineering firm Solargenix Energy
is developing a significant solar power plant, one of the largest built worldwide in the last
15 years. The plant adds important capacity to state utilities’ obligation to increase power
generation from renewable sources. Using parabolic trough technology, the electricity
will be produced by a 72-megawatt (MW) Siemens steam turbine-generator.
Photos: Florian Sander
Sun and Steam Power the Nevada Desert
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The word ‘vast’ is perhaps inadequate to describe Nevada’s desert.
Its sheer scope, breadth and expanse are daunting. The mind can
play tricks when judging distance. What looks to be a mile or
so down the highway can suddenly turn into a 30-minute drive.
Of course, this being desert land the climate and landscape can be
extremely inhospitable. The southern region of Nevada, part of
the Mojave Desert, has both mountainous and flat or uneven bush
land, where away from the main towns you’d be hard pressed to
find a living soul. It is also hot, with minimal rainfall and maximum
sunshine every year.
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Twenty miles from the bright lights, big city attraction of ‘Fabulous’
Las Vegas is the quieter and more relaxed Boulder City. Originally
created in the 1930s as a home to the construction workers that
built the nearby Hoover Dam, Boulder is the city with the largest
geographical area in Nevada. Curiously, it is also the only city in
the state with no gaming.
In keeping with that tradition, exploiting the potential for solar
power generation on ideal terrain and climate is anything but a
gamble for the city. In fact, in these environmentally conscious
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times using Southern Nevada’s ample sunlight to provide electricity
for 40,000 local homes is a sound energy policy that allows utilities
to edge closer to legislative requirements for renewables.
Power by the Public Utility Commission of Nevada. The approval
allowed Solargenix to proceed with the development of its 64-MW
solar power plant.
RENEWABLE PORTFOLIO STANDARD
Put simply, the plant uses solar parabolic trough technology to reflect the sun’s heat onto oil-filled reception pipes running through
the mirror collectors. The synthetic oil is passed to heat exchangers
on the power island, which transfer the heat to generate steam for
the turbine.
In 1997, the State of Nevada adopted a Renewable Portfolio Standard that placed a mandate on the two utilities —Nevada Power and
Sierra Pacific Power—to use renewable energy to provide a minimum percentage of electricity consumption. A revision to that state
law in 2001 meant that this amount should increase by 2 percent
every two years. Each phase can be broken down as thus: 7 percent
in 2005, 9 percent in 2007, up to 15 percent by 2013. A further
amendment in 2005 saw the obligation rise to 3 percent every two
years culminating in a 20 percent share for renewable energy
generation by 2015. Investment in energy efficiency measures was
also added to that renewable portfolio standard.
A crucial part of the legislation expands the state’s commitment to
solar power so that the technology provides 5 percent of renewable
energy projects. The Nevada Solar One project currently under construction will go some way to supporting that ideal. In addition, the
US Department of Energy (DoE) has issued a report that identifies
suitable land and solar resources in Nevada that could produce
over 600,000 MW of electricity using concentrating solar technologies. Currently, Nevada’s power consumption is less than 3 percent
of this resource capacity. The DoE report also claims that the economic benefits far exceed the cost to develop this clean renewable
energy source.
ELDORADO VALLEY
On a 400-acre site in Boulder City’s Eldorado Valley—just off the
Route 93 highway linking Las Vegas and Phoenix — is a solar power
complex that, once complete will be the third largest in the world.
Solargenix Energy, Inc, a leading energy and environmental engineering company headquartered in North Carolina, is developing
Nevada Solar One. Earlier this year, the Spanish renewable energy
firm ACCIONA Energía S. A. purchased 55 percent of Solargenix.
It is the skill, engineering and solar know-how of Solargenix and
ACCIONA that drives the scheme, with more than a little help from
the prime mover of course — a Siemens SST-700DRH industrial
steam turbine-generator.
The first stone for Nevada Solar One was laid at a special ceremony
in February this year. This followed a long period of gaining planning permission and securing financing and tax incentives from
the Nevada Commission on Economic Development. In September
2005, Solargenix announced the approval of amendments to their
power purchase agreements with Nevada Power and Sierra Pacific
Capturing the sun via this process is known as concentrating solar
power (CSP). It uses curved (parabolic) mirrors to concentrate solar
radiation on a thermally efficient receiver running the length of
the trough. The receiver consists of a specially coated absorber tube
embedded in an evacuated glass envelope. Absorbed solar radiation warms up the heat transfer oil flowing through the tube to almost 400°C (752°F). The system also uses a tracker, so that the line
of the sun can be followed throughout the day. German company
Schott AG is the manufacturer of the receiver tube technology, and
for Nevada Solar One, Solargenix is using 19,300 of these units.
POWER ISLAND
For the power island, Solargenix awarded a contract to market-leading Siemens Power Generation in August 2005 for a high efficiency
direct reheat SST-PAC-700RH steam-turbine generator set. The contract has also included stand-alone Simatic S7 control systems and
installation and commissioning support plus staff training. The
72-MW SST-700 turbine has been manufactured at Siemens’ facility
in Finspong, Sweden. It is a dual-cased geared engine using one
high pressure (HP) and one low pressure (LP) module. The steam
turbine was delivered to site mid November, and the plant itself
should be commissioned in April 2007.
Steam is generated via the heat exchangers at 700°F/1,250 psia.
After passing through the HP turbine it is taken back into the steam
generator for reheating and bringing LP steam up to 700°F again.
This will further reduce the oil temperature back to the solar collectors and improve the overall cycle efficiency of the plant.
The reheated steam is now admitted into the LP turbine to further
generate power; it then enters a vacuum condenser where remaining steam is condensed to be pumped back into the steam generator again. This careful use of water is vitally important considering
the desert location and value of water sources. It has also been a
consideration for the plant’s cooling towers. But Solargenix is justifiably proud of the fact that the plant has no water discharge.
Supplementing the heat cycle is a small, natural-gas-fired auxiliary
boiler, which will be used at times when the sun’s radiation is not
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available, or during cleaning of the solar mirrors. The cycling capability of the plant is significant when dealing with likely variables
in steam temperature and pressure.
tion workers removed about three rattlesnakes a day. There were
also tarantulas and “hundreds” of black widow spiders presenting,
if not a danger, then at least a distraction to meticulously sort out.
The steam turbine is coupled to a generator, which produces electricity at 13.8 kilovolt (kV), 60 Hz. Power is then stepped up by a
transformer, to be distributed to the grid at 230 kV from the huge
switchyard. With a separate (and unconnected) combined-cycle
power plant adjacent to the solar plant this section of the desert is
a curious mixture of bush land and a sea of transmission towers.
IMPRESSIVE
WILDLIFE
Of course, working with this terrain has been another interesting
aspect of the project groundwork. With a rocky, uneven surface, not
to mention shrub and bush land, clearing 400 acres is a considerable task. And there have been other factors to take into account.
Despite the harsh environment, there is wildlife that adapts to its
surroundings and survives in the desert. On the road down to the
site it is not uncommon for roadrunners to dart across the tarmac.
But not all creatures great and small are particularly friendly. As
a Solargenix official confirms, during the ground clearance opera-
To give some idea of the scale of the plant, from the sites’ overall
area of 400 acres, 251 are taken up by the solar array system. At a
distance (and again we come to the sheer expanse of the Nevada
desert) the plant looks like a small, flat, white mass. When the site
draws closer its enormity is jaw-dropping; hundreds of huge CSP
troughs with crystal clear mirrors reflecting the desert with a burst
of deep blue and sandy brown colours. It is immensely impressive.
As is the steam turbine solution that Siemens has provided for what
was originally a tricky conundrum for the heat cycle of the Nevada
Solar One plant. Producing a quality, proven product at low investment and life-cycle cost and one that has been manufactured,
shipped and installed to meet customer commitments for on-time
delivery, power output and availability is further testimony to
Siemens’ solutions for every turbine application.
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Power in the Pipeline
Designed by Venezuela’s state-owned oil company as a part of a vast new natural gas
transportation system, a brand-new 300-km pipeline is being built to link the country’s western region with the existing gas infrastructure and the rich, but scattered, reserves from
producing wells in the central and eastern regions. As well as making this clean, low-cost
fuel available to many Venezuelans for the first time, the pipeline will enable gas to be
used to boost oil production from mature wells. As part of this complex US$520 million project, Siemens is supplying a total of ten gas turbine-powered compressor trains, which
will be installed by a Siemens-led consortium in compressor stations along the new pipeline.
Covering a total area about two-and-a-half times the size of Germany, Venezuela is located on the northern tropical Caribbean
coast of South America. The diversity and sheer beauty of its landscape so impressed the fifteenth century explorer Christopher
Columbus that he called it the Tierra de Gracia — Land of Grace —
which has become the country’s unofficial name. In contrast to its
soaring mountains, the world’s highest waterfall, tropical forests
and silver-sandy beaches which make Venezuela a magnet for
tourists, the country’s burgeoning economy is based principally
on the oil and gas industry.
BIG OIL
With proven oil reserves of around 76 billion barrels, Venezuela is
ranked as one of the world’s largest producers. However, a number
of the largest fields have been exploited for decades, with some of
the oldest wells in continuous operation for almost 100 years, and
production levels are now falling rapidly. Natural gas, co-produced
with oil from existing wells as well as from more recent finds both
onshore and offshore, is also currently being produced at an annual
rate of nearly 30 billion cubic meters, a large proportion of which is
being re-injected into fast-depleting oil reservoirs to increase their
production. In combination, this vital industrial sector accounts for
some eighty percent of the country’s export revenues and about a
third of its total earnings.
resource to its full extent. Today, as the price of oil continues to
rocket, the country’s economy is booming with real growth in GDP
approaching 10 percent, allowing previously shelved government
plans for expansion to be reactivated.
In 2004 the state-owned oil company Petroleós de Venezuela S. A.
(PdVSA) awarded contracts to three local companies for the first
stage in the construction of a huge new undertaking, the 300-km
Interconnexion Centro Occidente (ICO) pipeline, known as the ICO
project. This complex infrastructure project, due for completion
in 2007, will connect gas-producing wells in the eastern and central
regions with existing wells and new gas transmission systems in
western Venezuela, partly to boost oil production and also to bring
natural gas to consumers in that part of the country for the first
time. A 106-km pipeline providing a connection between natural gas
fields in Falcon state and the PdVSA Paraguana refinery complex,
one of the largest in the world, has already been completed and will
soon be delivering between 10 and 100 million cubic meters of gas
per day, increasing progressively until it reaches 100 to 300 million
cubic meters of gas per day.
GOING FOR GROWTH
Although the country has enormous reserves of natural gas, a lack
of adequate infrastructure, such as a national grid-system for
PICKING THE PATH
One of the largest and most challenging pipeline projects ever undertaken by PdVSA, the ICO system for the bulk transnational
transportation of natural gas, was originally planned nearly 20 years
ago. The giant new line now under construction will comprise 230
km of 30-inch (762 mm) diameter and a further 70 km of 36-inch
diameter (914 mm) pipe. The pipe is formed from special high-
the transportation of bulk supplies of natural gas or an established
country-wide distribution network serving urban and rural consumers, has meant that Venezuela has been unable to exploit this
tensile steel capable of withstanding internal pressures of more
than 4,600 bar, reducing both wall thickness and the number of
welds, and is being used for the first time in Venezuela. Buried at a
depth of about 1.2 meters in a 20-meter wide corridor, the line will
snake its way across the coastal plain, avoiding the most mountainous terrain, following a precisely planned path selected as the most
favorable from no less than 14 other routes originally surveyed in
the late ‘80s. Although designed to pass close to towns and centers
of population to provide these widely scattered communities with
gas supplies for the first time, the route of the ICO pipeline also cuts
through some of Venezuela’s most environmentally sensitive
and internationally important areas, which are home to rare plant
species, unique wildlife and archaeological sites. In consequence,
consent for construction has only been granted by the Venezuelan
government after the most rigorous scientific and ecological studies, covering the project’s impact on every aspect of local environments, with continuous inspections and environmental audits on
every centimeter of the route as work progresses.
As well as routing the pipeline unavoidably through a number of
archaeological sites revealing pre-Colombian discoveries currently
being studied by experts from around the world, the construction
crews have to contend with engineering a total of eighteen separate
river-crossings, many of which are in tropical rainforest environ-
ments. Using conventional technologies, taking even large-diameter pipelines across rivers does not present a significant problem.
However, official planning restrictions imposed by the Venezuelan
government to protect the delicate environmental balance in these
sensitive locations, prohibit any form of damage to all riverbank
environments, requiring the design and use by the contractors of
special-purpose systems, equipment and machines. The route also
crosses the Morrocoy National Park, necessitating a major detour
in order to follow an existing ‘service corridor’ through the park,
used as the least-damaging transit route for power lines and a water pipeline.
PERFORMING UNDER PRESSURE
Representing one of the largest contract awards made by the stateowned company in recent years, the three compressor stations
along the ICO pipeline will house a total of ten compressor trains
supplied and installed by Siemens. These comprise STC-SV compressors supplied from the Duisburg plant, powered by 13.4-megawatt (MW) SGT-400 gas turbines built at the Lincoln factory in
the UK. Six of the compressor trains are being supplied as high pressure units and four as low pressure trains, with all equipment
Photos: Siemens, Illustration: Maike Hamacher
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shipped to site via the Siemens facility in
Houston, Texas, where the compressor
trains were assembled and specially packaged for operation in a tropical environment. Three units are being installed at the
Morón compressor station, four at Los Morros and a further three at Altagracia. The entire turnkey contract is being carried out by
a local consortium headed by Siemens S.A,
partnered by Caracas-based Jantesa, which
has responsibility for engineering and procurement, with Confurca headquartered in
Ciudad Ojeda undertaking civil works. Siemens will also provide
full maintenance services for the turbocompressors over a fouryear contract period. The compressor stations will be monitored and
controlled remotely through an optical fiber data-communications
network being supplied by Siemens S.A. The stations will be linked
to the primary control room at Anaco and with a secondary control system in Caracas.
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”We are able to improve the standard of
living for literally thousands of people,
providing new facilities to towns and
villages, to scattered farms, communities and even to isolated dwellings.”
IMPROVING LIVES
Although Venezuela’s investment in the ICO pipeline is intended to
boost the national economy through increased oil and gas production, the vast, long-distance construction project is also aimed at
providing major social improvements for the
widely scattered, mainly rural communities affected by the project. In line with the government’s demand that no less than ten percent of the
entire project value must be returned to the communities involved, PdVSA is not only ensuring that
gas will become available as a low-cost fuel for a
large number of people for the very first time, but
is undertaking a far-reaching social initiative affecting communities along the whole length of the
pipeline. “This is the nicest and most exciting part
of this project,” says PdVSA Project Manager
Richard Tahan. “We are now able to improve the
Richard Tahan, Project Manager, PdVSA
lifestyle and raise the standard of living for literally thousands of
people, providing new facilities in areas ranging from entire towns
and villages, to scattered farms, communities and even isolated
dwellings.”
FISHING, FARMING AND FAMILIES
Richard explained that the initiative is being split into four sectors.
“The first will involve building and repairing roads, building new
local medical centers, improving existing schools and re-housing
widely separated and outlying families who currently live within
2.5 km on either side of the pipeline, in modern new housing.” He
pointed out that the pipeline project involves installing electrical
power, drilling wells for water for hydro-testing operations and
installing the Siemens data-communications network. “Because all
these utilities are already being installed along the route of the
pipeline, it is quite easy for us to provide modern facilities for people in the vicinity. They will not only be supplied with drinking
water and mains electricity, but will also have full access to telephones and a broadband connection to the internet,” said Richard.
The second sector will include the development of the fishing
industry in the coastal area of Rio Seco, with the provision of fresh
drinking water and mains electricity, but also including the construction of refrigerated storage and ice-making facilities to support
the local shrimping industry. The third and fourth sectors will cover the modernization and expansion of locally-based agriculture in
both the Altagracia and Los Morros areas. In addition to increasing
production and efficiency, additional investment in the agricultural
and farming industry will provide future employment for local people currently employed on the construction of the ICO pipeline.
WIN-WIN FOR SIEMENS
The Anaco project represents not just a major contract win for
Siemens, but marks a significant step forward in the further development of the company’s oil and gas business in Latin America.
The ability to demonstrate successful implementation of both industrial gas turbines and latest-generation gas compression
solutions under a turnkey contract in a tropical environment is
providing a benchmark against which competing products and
suppliers are measured and a win-win solution for Siemens and
customers alike.