POWER July 2013 - 16

Sodium-Sulfur Battery Pilot. In the U.S., also this May,
the California Energy Commission and Pacific Gas and Electric
Co. (PG&E) unveiled the Yerba Buena Battery Energy Storage
System Pilot Project, a system in east San Jose, Calif., that
charges a utility-scale sodium-sulfur battery (Figure 4) manufactured
by NGK Insulators when demand is low and then
sends reserved power to the grid when demand grows. " The
system has the potential to provide important services for balancing
energy supply and demand, [and] helping to support
greater integration of intermittent renewable generation, " the
commission said in a statement. The project has a 4-MW capacity
that can store more than 6 hours of energy. PG&E is
working with the Electric Power Research Institute to study
how sodium-sulfur battery energy storage can improve power
quality and reliability.
Undersea Pumped Storage. Norwegian research scientists
announced they would attempt to realize a concept of
storing electricity at the bottom of the sea using high water
pressure. The idea entails use of an underwater pumped hydroelectric
power plant. " Imagine opening a hatch in a submarine
under water. The water will flow into the submarine
with enormous force. It is precisely this energy potential
we want to utilize, " explains Rainer Schramm, inventor and
founder of the company Subhydro AS to Gemini.no. Schramm
is collaborating with Scandinavian research firm SINTEF on
the concept. " Many people have launched the idea of storing
energy by exploiting the pressure at the seabed, but we
are the first in the world to apply a specific patent-pending
technology to make this possible, " he adds.
Schramm's concept essentially converts mechanical energy using
a reversible pump turbine, as in a normal pumped storage
5. Storage under the sea. Norwegian researchers are working
to realize a concept that stores power using an undersea pumped
hydroelectric power plant. To use the water pressure on the sea
bed, mechanical energy is converted by a reversible pump turbine,
as in a normal pumped storage hydroelectric plant. Source: Knut
Gangåssæter/Doghouse
hydroelectric plant (Figure 5). " A pumped storage power plant is
a hydroelectric plant which can be 'charged' up again by pumping
the water back to the upper reservoir once it has passed through
a turbine. This type of power plant is used as a 'battery,' when
connected to the power grid, " the inventor explains. The plant's
turbine will be connected to a tank on the seabed at a depth of
400 to 800 meters. The turbine is fitted with a valve, which when
opened, allows water to flow in and start turning the turbine. The
turbine drives a generator to produce electricity. When the tanks
are full, the water is removed by running the turbine in reverse,
so that it functions as a pump.
" One can connect as many tanks as one wishes. In other
words, it is the number of water tanks that decides how long
the plant can generate electricity, before the energy storage
capacity is exhausted, " Schramm says, noting that calculations
indicate an electric storage efficiency of about 80% round trip.
A " normal-size " plant could produce about 300 MW for a period
of 7 to 8 hours.
E.ON Avoids Shuttering Ultramodern
German Combined Cycle Units Despite
Profit Concerns
German energy giant E.ON in late April narrowly averted idling
its Irsching 4 and 5 units in Bavaria, Germany-its most technologically
advanced gas-fired generating units that began
operations just three years ago at a cost of €400 million.
The 569-MW Irsching 4 (a 2011 POWER Top Plant) was the
world's first to feature a Siemens H-class turbine (Figure 6)
and boasts an efficiency of 60.4%. The 860-MW Irsching 5,
commissioned in 2010, has an efficiency of 59.7% and is a
multi-shaft plant with two steam turbines, each one with a
waste heat recovery boiler.
But E.ON had said the highly efficient combined cycle
units were unprofitable because, while Europe's wholesale
6. The 60-Hz H-Class. E.ON's Irsching 4 unit in Bavaria was the
test site of Siemens' advanced 50-Hz " H-class " SGT5-8000H gas turbine
until the end of 2009, when it was expanded into a combined
cycle gas turbine plant by adding a waste heat recovery boiler and a
steam turbine. The first of three 60-Hz versions (SGT6-8000H, shown
here) of the gas turbine was successfully started at Florida Power &
Light Co.'s $900 million Cape Canaveral Next Generation Clean Energy
Center in Port St. John, Fla., last November. Cape Canaveral began
commercial operations on April 24. The 274-MW turbine is also capable
of reaching efficiencies topping 60% in combined cycle operation, Siemens
says. Courtesy: Siemens Energy
Ventilation
Turbine
400-800 meters
16
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POWER July 2013

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