Energy-Control
System
™
Low water usage and fast power
production without the need
for an oversized condenser
White Paper | June 2016
Siemens Flex-Plants™ with Energy-Control offer the ability to start the gas turbines
at full ramp rate without the need for an oversized air cooled condenser (ACC).
During a fast plant start-up, steam is produced quickly. At initial operation, steam is
bypassed around the steam turbine until the bottoming cycle is warm and ready to
accept the full plant steam flow. In an air cooled plant, this steam is routed to the air
cooled condenser. The larger the amount of bypassed steam, the larger the air
cooled condenser needs to be. Siemens new Energy-Control technology modifies
the flow through the HRSG, creating less steam when desired and offering an
alternative solution to increasing ACC size for fast start – without negatively
impacting the normal operation of the plant.
Introduction
Energy-Control technology enables fast gas turbine starts in an air-cooled combined
cycle without increasing the size of the ACC. This is achieved by partially bypassing
the heating surfaces and modifying the pressure and the temperature in steam
generating parts. This results in reduced steam production and lower ACC heat load.
Less energy is extracted from the exhaust gas and more energy is disposed through
the stack.
Discussion
To achieve high power production quickly, Siemens Flex-Plants are designed for
unrestricted start-up of the gas turbine, enabling a combined cycle to produce
power as fast as a simple cycle. Unrestricted start-up means that temperature
changes occur very quickly, not only in the gas turbine, but everywhere downstream
as well. Conventional combined cycles are not designed for these transients, but
Siemens Flex-Plants include technology to manage this energy downstream and
protect the system components.
Subject to change without prior notice.
© Siemens Energy, Inc. 2016. All rights reserved.
siemens.com/powerplants
White paper | Energy Control System | June 2016
Plant Power Output – Flex-Plant vs. Conventional
+S
T
T
GT
GT
+S
100% GT
Flex-Plant
GT
The HRSG is designed to maximize heat transfer between
the gas turbine exhaust flow and the water in the steam cycle.
For Energy-Control, the HRSG is temporarily rerouting flow to
reduce heat transfer and produce less steam.
This is achieved by a combination of flow bypass and set point
changes which reduce HRSG heat absorption until the system
is ready to receive full steam flow.
PLANT POWER OUTPUT
Included in the Flex-Plant technology is a start-up sequence
where some of the early steam produced is bypassed around
the steam turbine and routed to the condenser. In an aircooled system, this higher steam flow can create the need
for a larger air-cooled condenser. To avoid using a larger
condenser, an option would have been to start the gas
turbines sequentially or operate at part load until the
bottoming cycle was ready to handle higher load. Now, with
the introduction of Siemens Energy-Control technology, gas
turbines can fast start without needing a larger ACC.
GT
GT
+S
T
Conventional
Conventional Plant Power
Flex-Plant w/ Energy-Control
TIME
Conclusion
Siemens is focused on providing innovative and competitive
solutions that help power plants meet the needs of the future.
Low water usage and fast power production without the need
for an oversized condenser makes Energy-Control a win/win
solution.
Energy-Control offers the benefit of fast plant start without
increasing the size of the ACC. This can result in a savings of
more than $5 million for a fast start 2x1 F-class plant.
The utilization of the combined cycle with Energy-Control
technology is the next step in our evolution of creating ecofriendly and integrated power generation.
Siemens Energy, Inc.
4400 Alafaya Trail
Orlando, FL 32826-2399
USA
Tel: 888-593-7876
The information in this document contains general descriptions
of the technical options available, which may not apply in all
cases. The required technical options should therefore be
specified in the contract.
Subject to change without prior notice.
© Siemens Energy, Inc. 2016. All rights reserved.
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