TurboPHASE: Cost-Effective and Efficient Peaking Power

Robert J. Kraft

Founder and CEO, PowerPHASE LLC

December 13, 2012

Background and market principles

When it comes to power, what does the world want and need? Everybody wants more power

that is cost-effective and efficient. Investors who build plants demand fairly predictable returns

and the world as a whole is pushing for cleaner power. Renewable energy has its place and fits

in with this methodology; however, the intermittent nature of solar and wind power causes an

even greater need for peaking generation. The cleanest form of reliable peaking power, besides

hydro in some locations, is from natural gas fired gas turbines.

The PowerPHASE LLC team has been involved with gas turbine development for three decades.

Bob Kraft, the founder of PowerPHASE, was a senior engineer in Pratt & Whitney’s turbine

division. Other team members have extensive OEM and GT end-user experience. Bob and some

of the other PowerPHASE team members previously founded and built Power Systems

Manufacturing in Jupiter Florida, where they developed new products for gas turbines that

offered customers a better value proposition – greater efficiency and lower emissions, at a

competitive cost. PSM grew from nothing to a 400 person company today and is a thriving

business competing head to head with the OEMs of the world.

Since 2010, PowerPHASE LLC has completed market analysis, product development and

intellectual property protection, and emerged in April of 2012 with its initial product offering.

The initial focus of the PowerPHASE LLC team was on creating an energy storage product. They

have developed efficient, power-dense, grid-scale modular compressed air storage packages

that the company believes will have international application wherever the many different

aspects of energy storage are appreciated. Unfortunately, while everybody understands how

much value storage can add to the grid, the power markets in the United States do not currently

enable a storage owner to earn a reasonable return on it. While working through the

development of these PowerPHASE storage products the team also discovered an application of

compressed air that is powerful, cost-effective, efficient, and immediately applicable to

thousands of gas turbines around the world.

Consequently, two main products have been developed as well as one hybrid system. The peak

power system, called TurboPHASE, is discussed in this paper. The hybrid air system,

TurboPHASE GSX (Grid Stability Control), which integrates a power regulation feature (energy

storage) with TurboPHASE is the subject of an additional paper that will be posted on the

PowerPHASE web site. A third technical paper on the, PowerPHASE product, named after the

company, will also be available on our web site.

TurboPHASE

TurboPHASE, a modular package, is the lowest capital cost way to add up to fifteen percent

more power to a combined cycle plant and twenty percent more to a peaking plant. The new

system is also very efficient, improving the heat rate in simple cycle and producing power from

ten to forty percent more efficiently than other simple cycle peaking options. The package

avoids using unproven and therefore risky technologies, which helps power plant investors be

comfortable with a new system, while at the same time offering owners a reasonable economic

return in several markets within the USA and globally.

TurboPHASE combines a highly efficient reciprocating engine—fueled with natural gas, diesel or

biodiesel—driving an intercooled compressor that takes its air flow output through a

recuperator for heating and then directly into the combustion section of the gas turbine. It

starts in seconds, runs indefinitely, and thanks to the much greater combustion efficiency of the

reciprocating engine, produces no efficiency penalty for the overall power plant facility.

The package was designed to be effective at any time, but especially on the hottest days when

peaking power is typically needed most. The most significant feature is that the package does

not take anything away from the gas turbine in simple or combined cycle, and there is therefore

no effect on base load combined cycle efficiency whether the TurboPHASE system is running or

not. On combined cycle plants, the incremental power boost that is produced from the

TurboPHASE system has a heat rate that is significantly better than even the best simple cycle

peaker plant. When the TurboPHASE system is running on simple cycle plants, the overall

efficiency of the plant is actually improved. On both simple and combined cycle plants, the

emissions are as clean as the power plant that the system is fitted to. So why would anyone

build a new peaking plant rather than boost the output of an existing plant efficiently with

TurboPHASE using significantly less capital?

Power when you need it most

TurboPHASE restores a portion of missing air flow that naturally diminishes in all gas turbines as

ambient temperatures increase, or at elevation. On constant speed single shaft gas turbines,

the compressor section pumps a constant volume of air; however, air becomes less dense with

increasing temperatures and altitude, which results in reduced air mass flowing through the

turbine section. Since the air flow is down, in order to maintain proper combustion the fuel flow

is also reduced proportionately, which in turn reduces power generation proportionately.

Figure 1 shows this general trend and also shows what TurboPHASE does. TurboPHASE adds the

missing air mass and volume, which with the addition of more fuel, restores a portion of the

plant capacity. The amount of air injected is determined by considering the plant-specific limits,

including internal gas turbine limits, generator limits, transformer limits and transmission limits,

and determining the ambient range for which the extra power is desired. Depending on the

existing plant capabilities, approximately five to ten percent of inlet air can be injected. The

illustrations and examples hereafter will refer to five percent inlet air injection on a 7FA.04 gas

turbine in simple or combined cycle. Because the system is modular, it may be run at less than

full load on colder days, and still achieve a significant level of cost-effective and efficient power

boost.

Figure 1 TurboPHASE boosts power and stays within existing plant limitations.

What is TurboPHASE?

TurboPHASE is a retrofit package for simple cycle or combined cycle power plants that restores

power that is normally lost at elevated ambient temperatures or altitudes. The system takes

advantage of the fundamental characteristic that the gas turbine, generator, transformer and

electrical grid connection are designed for system planning, safety, maintenance cost, and

efficiency, to limits based on cold day conditions where the plant can produce its maximum

output. With air injection, the factor limiting the power that a gas turbine can produce is the

mechanical shaft torque produced on a cold day, typically zero degrees Fahrenheit. As

illustrated in Figure 1, the design electrical limits of the plant deteriorate with elevated ambient

temperatures; however gas turbine output falls off even more rapidly, leaving unused plant

capacity.

There are several current technologies that can be employed to restore the missing power to a

gas turbine; however, TurboPHASE is the only technology that boosts power using a separately

fueled system and does not involve any water injection at all. This is critical, as the only input

for the power boost is fuel, which allows this technology to be implemented cost- effectively on

combined cycle plants. When the TurboPHASE system is implemented on a combined cycle

plant, the result is the world’s most efficient gas turbine peaking plant: ten percent better than

the most efficient aero derivative engines, and forty percent better than E class engines. The

schematic at Figure 2 below illustrates how the Turbophase system is implemented on a

combined cycle plant.

Figure 2 TurboPHASE works on both simple and combined cycle plants

Why is TurboPHASE so efficient?

The heart of the TurboPHASE system is a reciprocating engine driving an intercooled

compressor, with typical fuel efficiency of thirty-eight to forty-four percent depending on

manufacturer and technology. The most advanced aero derivative gas turbines have fuel

efficiencies of thirty-nine to forty-one percent (LM6000 and LMS100 respectively at 95°F) in

simple cycle, while the fuel efficiency of the workhorse combined cycle F class engines is

approximately thirty-six percent in simple cycle. In addition, because of the intercooled

compression process, the work required to produce the additional flow is less than the gas

turbine has to do, on a per-pound basis. In summary, the engine driving the auxiliary

compressor is more efficient and it is driving a more efficient process. To illustrate this point,

the 7FA.04 engine on a 95°F day requires 164,665 kW of power to drive its compressor, which is

producing an inlet flow of 873 pounds of air per second at 211 psi, or 188 kW / (lb/sec) of

airflow produced. The 188 kW is taken from the gas turbine, which has a fuel efficiency of

36.5%, so it takes 1.76 MMBTU/hr to generate 1 lb/sec of airflow. Figure 3 shows the

compressor specific fuel consumption, (MMBTU/hr)/(lb/sec), for several different gas turbines

on a 95° F day. Figure 3 compares this with the PowerPHASE system.

Figure 3 Compressor specific fuel consumption comparison, integrated gas turbine vs

TurboPHASE1

PowerPHASE has evaluated several compressor lines from different manufacturers. For this

illustration a three-stage Cameron centrifugal compressor is used. It is a production compressor

that helps to keep the cost as low as possible. In addition, Cameron has nine hundred thirty

machines like this running in different types of processes, including the oil and gas fields, with

expected lives greater than thirty years. For pressure requirements higher than 200 psi, a

booster stage is added. The underlying compressor TurboPHASE uses for a 7FA.04 application

has characteristics that require 1,409 kW, consisting of 1,225 kW for the 200 psi compressor and

183 kW for the 240 psi booster, to pump 7.2 lbs/sec to 240 psi. On a 95°F day, the gas turbine

compressor discharge pressure is 211 psi. This pressure increases to 224 psi with the 5%

increased flow, and 240 psi is high enough to deliver and distribute the air into the gas turbine.

The TurboPHASE standard reciprocating engine is running at 92% load at this point and

consumes 14.8 MBTU/hr with 38.8% fuel efficiency. This results in a 1.68 specific fuel

consumption, which is lower than the 7FA.04. In other words, the TurboPHASE compressor uses

1 In this grouping the E class machines, the brown dots on the figure, typically have the lower compressor

discharge pressures and firing temperatures, and have slightly higher compressor specific fuel consumption. Even though the gas turbine compressor is pumping air into a lower pressure plenum in the E class engines, the compressor-specific fuel consumption is slightly elevated. This is driven primarily by the lower efficiencies associated with the E class gas turbine, typically around thirty-two percent, compared to the F class which is typically about thirty-six percent.

less fuel to deliver air to the combustor than the gas turbine itself. This, however, is just one

element of the efficiency improvement TurboPHASE adds to the gas turbine.

Engine Selection

As discussed above, a significant efficiency feature of the TurboPHASE system is the

reciprocating engine. Suitable reciprocating engines are available in several classes. For

TurboPHASE we have generally selected higher speed, lower efficiency engines as the optimum

choice. For the 7FA.04 application an engine with about 39% efficiency was chosen even though

engines with efficiencies around 44% are available. The higher speed engine has an exhaust

temperature of about 950°F compared to about 650°F for the more efficient engine. A

significant portion of this exhaust heat is used in a recuperator to allow matching the

temperature of the TurboPHASE injection air to the temperature of the gas turbine compressor

discharge air. A detailed analysis reveals that this results in a higher TurboPHASE system

efficiency compared to the lower exhaust temperature, high efficiency engine, as the GT does

not have to burn additional fuel to heat this supplemental air. The higher efficiency engines are

also significantly more expensive on a per horsepower basis. The combination of a less

expensive engine with exhaust energy available to heat the TurboPHASE air less expensively

than it can be done in the GT combustor is a significant source of the cost effectiveness of the

TurboPHASE system.

A property of a reciprocating engine that is significantly different from a gas turbine is that the

efficiency is relatively insensitive to back pressure of the exhaust. For example, on a typical

2,300 HP engine—like the one used in the 7FA.04 example—the back pressure allowed before

any significant power deterioration is 28” water, or 1 psi, while gas turbine performance is

measurably impacted with only a fraction of this back pressure. A simple cycle 7FA.04 gas

turbine with an increased back pressure from 4” to 28” would experience a 4.5% loss in power

and efficiency. It is the reciprocating engine’s high relative tolerance for back pressure that

enables an efficient and low cost recuperator to be employed to heat the compressed air. The

classes of reciprocating engine considered for TurboPHASE also typically hold their power rating

with elevations up to 3000’ and 100°F ambient temperatures. This is primarily driven by the

fact that they are turbocharged and the rpm of the turbocharger increases as the air becomes

less dense with elevated ambient temperature and increasing elevation. This results in a fixed

inlet mass flow rate and fixed power output. The combination of these reciprocating engine

characteristics allows the TurboPHASE system to deliver a constant air and power boost to the

gas turbine over a wide range of ambient temperatures and up to 3000’ elevation before the

engine power or efficiency begins to be affected.

Figure 4 shows a typical package layout for the TurboPHASE system (preliminary packaging

design and model provided by Cobey) where the ambient air enters the intercooled centrifugal

compressor and exits as heated pressurized air that goes to the gas turbine. The exhaust from

the engine is effectively cooled in the recuperator and then discharged.

Figure 4 TurboPHASE airflow

An important aspect of the TurboPHASE system is that it there is no “netting” effect for the

power boost—meaning that no energy is drawn from the gas turbine system to drive the

TurboPHASE system. Most gas turbine power augmentation systems that deliver significant

power increases, such as steam injection or inlet chilling, produce the same power boost from

the gas turbine. For a similar amount of injection or induced flow, however, they consume or

take away significant power, resulting in net power available to be delivered to the grid that is

lower than TurboPHASE, while at the same time significantly penalizing efficiency.

For example, on a 2x1 combined cycle 7FA.04 plant with 5% TurboPHASE injection into each

engine, a 41 MW power boost will be realized: 36 MW is from the two gas turbines (18 MW

each), and 5 MW from the steam turbine. Applying steam injection or inlet chilling technology

to produce an 18 MW increase in gas turbine output, however, will reduce steam turbine power

by 21 MW and require 11 MW of electrical load, resulting in substantially lower net power

output and a significant heat rate penalty. Steam injection and inlet chilling are discussed in

more detail in the last section of this report, but in practice, application of any of the

technologies discussed above will be limited by some aspect of the gas turbine, whether

mechanical or electrical, which will limit how much additional power can be produced.

Consequently, the TurboPHASE system will result in over twice the level of power boost of

steam injection and 1.6 times that available from inlet chillers. The fact that TurboPHASE uses

fuel rather than plant electrical power or steam to add the missing air is a primary driver for cost

effectiveness and efficiency of the TurboPHASE system, as the entire power boost is power that

can be sold, effectively lowering the cost per kW of the TurboPHASE system.

The base load net power capacity of a nominally rated 7FA.04 gas turbine at 95°F is 153.5 MW.

With 5% TurboPHASE injection it achieves 171.5 MW; an increase of 18 MW, or 12%. Gas

turbine inlet flow on a 95°F day is 869 lb/sec, which produces a net output of 153.5 MW, or

0.18 MW/ lb / sec, a term General Electric calls “specific output” in their GER 3567H (available

on the web). The TurboPHASE 5% injection rate is 48.8 lb/sec, measured as 5% of inlet flow at

an ambient temperature of 59°F, or 5% of 976 lb/sec, which actually represents an increase of

5.6% compared to the airflow produced by the gas turbine alone on a 95°F day. Therefore, on a

95°F day, an increased airflow of 48.8 lbs/sec results in 18 MW net power, or 0.37 MW /

(lb/sec), or 2 times the specific output of the 7FA.04 on a 95°F day.

Why does TurboPHASE produce so much extra power? The reason is simple. At the 95°F

condition, while the gas turbine- generator is netting out 153.5 MW, the compressor section is

also consuming 164 MW, for a total of 321.5 MW, which all must be produced by the turbine

section, with an inlet flow of 869 lbs/sec, or a specific output of 0.37. Therefore an injection of

only 5% (effectively 5.6% compared to the GT flow on a 95°F day) results in a 12% power boost

from the gas turbine with no significant extra GT compressor load, since the extra air is provided

by a separately fueled compressor. Those skilled in the art will recognize that this is a somewhat

simplified explanation because of the increased pressure ratio effect, however it illustrates the

point that TurboPHASE generates twice the power on a percentage basis relative to the injection

rate.

The Practical Limits of Boost

Figure 5 is a diagram similar to one that can be found in the GER 3567H, the GE Gas Turbine

Performance Characteristics document. This curve, however, is data obtained from Thermoflow

GT PRO/Master for the 7FA.04, and points out how the exhaust flow, output and heat rate vary

with ambient temperature. At 120°F, the GT output is 134 MW. On a 59°F day the output is

178 MW and on a 0°F day, the output would be 224 MW. However, since the 7FA.04 is an

upgrade from the 7FA.03, the shaft torque limit is actually reached at 36°F which corresponds to

a 191 MW GT output and compressor work (because it is a cold end drive machine) of 189 MW,

for a total of 380 MW being torsionally transmitted from the turbine section through the

compressor shaft. 380 MW corresponds to the total power transmitted on a 0°F day on the very

common 7FA.03 base model (formerly designated as the 7241 or the 7FA+e). In other words, on

a 7FA.04, at temperatures below 36°F, the gas turbine output is limited, or “flat-rated”, at 191

MW. Since the gas turbine compressor is still trying to pump more air at these cooler

temperatures, the output is controlled by reducing the fuel/firing temperature and closing the

inlet guide vanes (reducing the flow). Because the firing temperature is dropping and the

compressor’s air flow is throttled by the inlet guide vanes, the heat rate is negatively impacted.

As discussed earlier, since the gas turbine compressor is normally running at constant speed

and volumetric flow, the flow and power are directly proportionate to the air density changes

with ambient temperature, which are linear. Consequently, the exhaust flow and output of the

gas turbine have an inversely linear proportionate relationship with ambient temperature. As

the temperature increases, the flow and power reduce and the gas turbine becomes less

efficient, so the heat rate increases. In figure 5, at 36°F, the flow is 5% higher than on a so-

called ISO day (59°F) and 17% higher than a 95°F day. TurboPHASE injection rates are typically

in the 5-10% range, which allows a wide ambient temperature range for full injection.

Figure 5 7FA.04 GT performance characteristics

As described above, since a 5% airflow injection rate results in a 12% power increase, the

mechanical aspects of the gas turbine, not flow characteristics, actually limit how much injection

can be done. This must be checked for each different engine application as other engine models

may have additional limits. Figure 6, below shows 5% injection (5% of ISO GT compressor inlet

flow) and Figure 7 shows the resulting 12% power from the gas turbine. As may be seen, the

mechanical limits, primarily shaft torque, bound how much flow can be added. In this example,

at 67°F, the flow limits have significant margin where the mechanical limits are being reached.

Figure 6 5% Flow injection to 7FA.04GT – Flow limits

Figure 7 5% flow injection results in 12% power increase on the 7FA.04 GT - Mechanical limits

There are several other changes that occur in the gas turbine when air is injected into it, that

give the operator additional opportunities to benefit from TurboPHASE. The most significant

change for combined cycle applications is that the exhaust temperature drops while at the same

time the exhaust flow increases. This is a result of pushing more flow through the turbine,

resulting in an increased pressure ratio and therefore an increased temperature ratio. On the

7FA.04 at 95°F, 5% injection results in an exhaust temperature drop of 14°F. Since the firing

temperature is unchanged, the larger temperature ratio across the turbine results in a lower

exhaust temperature. These temperature and flow effects counterbalance each other for the

most part. Even though the exhaust temperature drops 14°F, because the flow is increased by

5%, the net output of the steam turbine only increases by 5 MW, or three percent. Notably,

however, depending on the heat recovery steam generator (HRSG) flow capacity and metal

temperature limits, duct burner capacity and steam turbine flow capacity, the increased exhaust

flow being at a 14°F lower temperature creates an opportunity to add 12,800 BTU/sec (~6%)

more duct burner capability to each gas turbine, likely at very little capital cost. If the air

injection rate can be increased to 10% for example, this would add 12% more duct burner

capacity.

Another fundamental principle that TurboPHASE takes advantage of is technological

advancements in the gas turbine itself. Since only clean air is injected, there are no negative

impacts to the durability of the turbine section, and the firing temperature can remain constant.

This is not true for steam injection, for example, where heat transfer coefficients are increased

when steam is injected, and the firing temperature may be reduced to avoid a reduction of

turbine component life. Therefore, the TurboPHASE system can take advantage of elevated

firing temperatures that are the primary drivers for combined cycle plant efficiency.

Table 1 below displays the output and heat rates of various engines in simple cycle and

combined cycle configuration with 5% TurboPHASE injection rates. For 10% injection rates, the

power output will be approximately double what is shown in the table. As may be seen, the

engines with higher firing temperatures receive greater benefit from TurboPHASE injection.

Table 1 Simple and combined cycle gas turbines with TurboPHASE (5% injection on a 95°F day)

Figure 8 summarizes data shown in table 1 and shows the relationship between specific output

and efficiency for E class and F class and aero derivative engines, in comparison to the

incremental TurboPHASE output as applied to F class combined cycle plants. It can be seen that

TurboPHASE delivers more power per pound of air flow through the gas turbine, at improved

efficiencies. This is why we say that adding TurboPHASE to a combined cycle gives the operator

the most cost-effective and efficient peaking power increment available in the market. To

illustrate the effect of TurboPHASE ‘s increased specific output, or power density, a 40 MW

TurboPHASE system fits in the parking lot of a compact 40 MW LM6000 peaking plant.

Figure 8 Efficiency and specific output comparison of simple cycle gas turbines and TurboPHASE

As the firing temperature and pressure ratio of gas turbines increase, which in general leads to

improved efficiency, the specific output, or the power derived from one pound per second of

compressor inlet airflow, also increases. Since the TurboPHASE unit production package works

on a variety of gas turbines, the same package on an E-class versus an F-class unit that is

producing more power with the same air, will cost significantly less on the F-class engine on a

dollar per kilowatt basis. This rationale holds true whether applied to a peaking or combined

cycle plant. Because the TurboPHASE system does not net out any significant energy from the

simple cycle or combined cycle configured plants, but makes additional power in the steam

turbine, the cost of incremental power on a $/kW basis is lower for the combined cycle plant.

How long will TurboPHASE last and what will it cost to maintain?

Figure 9 shows the main components of the patent pending design. The reciprocating engine is

typically rated for a 72,000 hour life with periodic maintenance before requiring a major rebuild.

On the 7FA.04 application as discussed throughout this paper, the power input for one module

is about 1.4MW, which because of the multiplier effect of the TurboPHASE system generates

about 3 MW of electrical output on a 7FA.04 combined cycle plant, more than twice the power

output of the reciprocating engine. Therefore on a per kWh combined cycle unit output basis,

the maintenance cost of the reciprocating engine is roughly comparable to that of the combined

cycle unit itself.

Figure 9 TurboPHASE main components

The engines that have been selected for the TurboPHASE package are made by large, global

OEMs and come with traditional warranties and maintenance options. The power from the

engine is transmitted through a commercially available hydraulically damped coupling. A

standard gear box then steps the speed up to the appropriate compressor input speed. Both

the coupling and the gearbox are made by large OEMs and are rugged designs typically found in

the oil and gas industry. Once the power reaches the compressor, conventional bearing and

turbo compressor technology that has been employed for over twenty years and more than nine

hundred units takes over. Multi stage compression with intercooling between the stages is

enclosed in one simple, proven and rugged production package. Cobey has provided the

preliminary model of the TurboPHASE package. Cobey has considerable experience packaging

Cameron compressors as well as reciprocating engine driven processes in industrial settings

which will ensure a safe, economical and maintainable system. The cooling is accomplished

with plant supplied cooling water or an optional cooling system. For the 5% injection example

on the 7FA.04, a 3,000 gallons per minute closed loop cooling system with an exit temperature

of 85°F cooling water is required. If this cooling capacity is not available from existing plant

systems, a conventional wet cooling tower with a 30 MM BTU /hr heat load capacity is

commercially available and is estimated to add less than $10 / kW to the installed cost. These

types of compression systems typically run for more than thirty years and require very little

maintenance compared to gas turbines. The air exits the compressor and enters the

recuperator. The recuperator is similar to designs that are deployed globally. For example,

Figure 10 shows a similar heat exchanger used in a similar application made by a supplier that

has been in business since 1928 making heat exchangers for all types of industries including

power generation.

Figure 10 Typical Recuperator

After the exhaust is cooled, it enters an optional Selective Catalytic Reduction system (SCR) that

can be part of the recuperator section. An optional carbon monoxide oxidation catalyst can also

be housed just upstream of the heat exchanger section if needed. In many cases, the exhaust

from the TurboPHASE system can be piped back to the GT’s exhaust, where the existing exhaust

treatment system can be utilized. The recuperator section is expected to run for 25,000 hours

between major maintenance events. If the system develops an issue, high pressure air will

escape into the exhaust gas, which is a benign event that can be detected by loss of pressure on

the compressed air side. The recuperator coil section is designed to slide out from the top for

easy maintenance, cleaning and replacement if necessary. Two conventional valves used in the

power generation industry control the interface with the gas turbine. One valve is located at the

gas turbine end of the air delivery pipe and one is located at the TurboPHASE unit. The valves

are controlled by a very simple control system that interfaces with the reciprocating engine

controls and the compressor standard instrumentation and protection equipment. The control

logic and operation is very similar to steam injection and the capacity to implement the required

changes to the gas turbine’s control system already exists. In summary, the TurboPHASE system

is a new and unique technology that is made up of proven and rugged components that will last

the life of the gas turbine plant itself.

What are the alternatives to TurboPHASE for additional Peaking Power?

Figure 11below compares several alternative technological and business approaches, with the

application of TurboPHASE to a 7FA.04 2x1 combined cycle plant. These alternatives are

displayed in order of increasing incremental heat rate compared to TurboPHASE, which has a

45% thermal efficiency, or 7,566 BTU / kWh heat rate. The 7FA.04 2x1 combined cycle plant

with 5% TurboPHASE injection produces an additional 40.7MW with an incremental heat rate of

7,566 BTU / kWh and its cost per kW is estimated to be approximately half that of a large scale

OEM upgrade, such as is offered by the two major manufacturers of frame type machines. The

incremental heat rate can be significantly improved, almost to the same level as the combined

cycle plant heat rate that it is applied to, if the low temperature heat given off by the

TurboPHASE auxiliary engine and the intercooling heat is used in the condensate heat up

process in the HRSG at the plant. To accomplish this, the HSRG needs to be modified to

incorporate this low temperature heat.

Based on Thermoflow data for the 7FA.04 2x1 CC plant, an OEM or equivalent upgrade from a

2x1 CC 7FA plant to the 7FA.04 will produce a total increase of 19.7 MW from the plant and will

improve the heat rate by 86 BTU / kWh (~1.3%). The heat rate and efficiency improvement is

accomplished primarily by raising firing temperature and/or improving component efficiencies.

This upgrade expected cost is significantly greater than TurboPHASE on any basis, but may be

more cost-effective for base load plants. Since the upgrade also utilizes a portion of the excess

gas turbine capability, the effective temperature range for 5% TurboPHASE flow increase goes

from 36°F to 120°F for the 7FA, to 67°F to 120°F for the 7FA.04. TurboPHASE is fully compatible

with the 7FA.04 upgrade as discussed earlier in the paper, as only the temperature range for full

flow operation is reduced. Similarly, if 10% injection were performed, the lower temperature

range would go up from 67°F to 95°F and the upper range would stay at 120°F.

Inlet fogger technology effectively adds 3.5 lb / sec of water to the inlet, which adds 16 MW of

output to the combined cycle plant at about the same efficiency as the combined cycle plant

itself. This is very efficient; however, the technology is inherently limited to producing a

relatively small MW increase, and most gas turbines are already equipped with foggers of some

sort. Care must also be taken to prevent damage to the compressor blades due to excessive

water droplet sizes and corrosion.

Duct burners are also effective at adding peaking capacity; however, a higher efficiency penalty

is attributed to this technology. Because of their low cost, duct burners are installed on most

combined cycle power plants when new. TurboPHASE also adds significant MW boost to the

plant, but because of its improved efficiency relative to duct burners, should be dispatched

more hours of the year in many applications, which should more than compensate for the

installed cost differential.

Building new simple cycle peaking plants, using high efficiency gas turbines such as the LMS 100,

is an option. However, not only is the capital cost of new build machines significantly higher

than TurboPHASE, but their heat rate is about 1,000 BTU / kWh higher and takes several times

as long to procure and get on-line, compared to a much more efficient power boost from

TurboPHASE, which can be installed at the plant in one week with a lead time of only 9-12

months.

Inlet chilling is the closest technology to TurboPHASE because it also adds air mass to the GT by

cooling the inlet air. However, the electrical load on the plant from inlet chillers not only adds

significant cost and complexity, it also has a significant negative impact on the efficiency of the

plant when it is operating. In addition, the inlet chiller’s large inlet “radiator”, which can

negatively affect the plant performance all of the time, may not be practical due to space

constraints. Inlet chilling energy storage options also exist, however, the device must be charged

well in advance, as opposed to TurboPHASE, which is operational in seconds with no prior

planning required.

Another option for peak power capacity would be to buy an existing E-Class peaker, however,

this is not adding capacity to the grid; it is simply changing ownership.

Steam injection of approximately 100 kpph per gas turbine on a 2X1 501 F combined cycle

configuration increases the turbines’ power by 18 MW each, similar to TurboPHASE, but at a

very low cost. Because it depletes steam flow from the steam turbine, however, the steam

turbine loses 21 MW, so that a net of only 15 MW is realized by the operator. The incremental

efficiency of the 15 MW from the steam injection is approximately 14,000 BTU / kWh, which is

very inefficient, and the process also consumes almost 400 gallons per minute of make-up water

for the two gas turbines, making this normally a very low dispatch technology. The availability

of make-up water will be problematic at some sites, while it adds operational costs, and all gas

turbines take a turbine life debit due to the increased heat transfer associated with water in the

gas stream.

Figure 11 Comparison of power, efficiency and relative cost of TurboPHASE to other peak power

options

Summary

The TurboPHASE system is a new technology that taps into the unused capacity that exists in the

gas turbine at simple or combined cycle plants as ambient temperatures and elevations

increase. The incremental power it produces is significant. The incremental efficiency of

TurboPHASE is better than that of a gas turbine in simple cycle, and when applied to combined

cycle plants, is a much more economical source of additional peaking power than any gas

turbine peaking plant that exists today. The system is relatively compact, pre-assembled and

tested prior to being shipped to the plant, which keeps the installation simple, predictable, quick

and the low cost.