improved generator performance utilizing onsite hydrogen generation · pdf fileimproved...

IMPROVED GENERATOR PERFORMANCE UTILIZING ONSITE HYDROGEN GENERATION AND CONTROL

FPL RIVIERA POWER PLANT – CASE STUDY

INTRODUCTION The high thermal conductivity of

hydrogen has proven to be a key advantage in its use as a cooling fluid in electric power generators. It permits a reduction of nearly 20% in the amount of active material required in the construction of a generator of given output and for a given temperature rise of the windings. The density of hydrogen is also an advantage over that of air. Since hydrogen’s density is approximately one-fourteenth the density of air at a given temperature and pressure, the use of hydrogen reduces the rotational friction losses within a generator to a small fraction of the losses encountered when the generator is cooled by air.

Critical to the proper implementation of

a hydrogen gas supply system is the supply of a continuous stable flow of high purity hydrogen from a trusted source. The list of traditional sources of hydrogen includes delivered cylinders, tube trailers, and liquid tanks. Historically, the

alternative, onsite hydrogen generation systems have been deployed to very remote hard to reach locations. In recent years however, onsite hydrogen generation systems have been adopted by an increasing number of power plants as an alternative supply method. Power plant operators have also become more aware and attentive to the negative affects of low gas purity and poor pressure control in their generators. Many plants have begun to study the possibility of upgrading their passive hydrogen monitoring systems with system that provide both gas monitoring and active gas purity and pressure control. Furthermore, when a method of purity monitoring and active hydrogen control is coupled with the implementation of onsite hydrogen generation, advantages in lower hydrogen cost, improved plant operations, and increased safety can also be realized.

This paper will present a case study on

the recent pilot installation of onsite hydrogen generation and active control at an FPL power plant located in Riviera Beach, FL.

Proton Energy Systems, Inc., a subsidiary of Distributed Energy Systems Corp, designs, manufactures and installs HOGEN® hydrogen generation systems for industrial and government customers worldwide.

Since our founding in 1996, we have installed over 750 systems in 50 countries around the world.

[email protected] www.protonstableflow.com

Authored and presented at PowerGen International Conference, Orlando, FL Nov. 2006, By: John Speranza, Proton Energy Systems and Eric Else, Florida Power & Light

HOGEN, StableFlow, Proton Energy and the Proton symbol are registered trademarks of Proton Energy Systems, Inc. © 2006 Proton Energy Systems Inc., all rights reserved.

Florida Power & Light Power Plant, Riviera, FL USA

Proton Energy Systems, Inc. 10 Technology Dr. Wallingford, CT 06492 USA PH: 203.949.8697 FX: 203.949.8016

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Proton Energy Systems, Inc., 10 Technology Drive, Wallingford, CT 06492 PH: 203.949.8697 FX: 203.949.8016 [email protected] www.protonstableflow.com


CASE STUDY BACKGROUND

FPL is one of the largest and fastest growing utilities in the nation. The utility projects an average increase of more than 80,000 customers annually and has approximately 24,000 megawatts of generation as of 2005. Engineers at FPL’s Juno Beach headquarters initiated a technology evaluation program of an onsite hydrogen generation and control system designed to improve the overall efficiency of the electric power generating assets at the Riviera Power Plant.

FPL’s Riviera Plant was commissioned in 1946 with Unit 1, which provided what was then a much needed 40 megawatts to the Riviera Beach community. Unit 2 came on line with yet another 70 megawatts of capacity in 1953 and both units continued to operate until 1985, when they were retired. Riviera's two active generating units - 3 and 4 – came on line in 1962 and 1963 respectively and are capable of producing 580 megawatts of electricity. Both units burn either natural gas or fuel oil to produce electricity to supply approximately 136,360 customers.

PRE-EVALUATION OPERATIONS

Riviera Power Plant operations personnel maintained hydrogen within Unit 3’s casing by manually introducing hydrogen from cylinders once per shift. The hydrogen gas pressure varied between five or ten psig from the specified casing pressure. Hydrogen gas purity was consistently above 98% and a manual purge was initiated whenever the purity dropped below 97%.

The plant maintains 60-100 gas cylinders on site to provide purity purge gas when needed and refill the unit after an outage. Prior to installation, about fifteen cylinders per week were rotated through the storage facility and transported to the respective hydrogen manifolds for daily usage requirements. Hydrogen cylinder gas average costs for Florida range from $4/100cf to $8/100cf with the majority of hydrogen costs associated with the filling, transportation, and rental of the cylinders themselves.

EQUIPMENT INSTALLATION

A Proton Exchange Membrane (PEM) onsite hydrogen generator manufactured by Proton Energy Systems was installed on Riviera’s Unit#3 September 14, 2006 along with a hydrogen gas monitoring and active control system. The onsite hydrogen generator is designed as a fully integrated hydrogen supply solution

that utilizes plant de-mineralized water and standard single phase 240 VAC power to generate Ultra-High Purity (UHP) hydrogen on demand as it is needed to maintain pressure, purity, and dew point within the electric power generator casing.

The hydrogen gas monitoring and control system that was installed is an innovative product that monitors the hydrogen within the generator casing and actively controls the purity, dew point, and pressure within operator preset values that represent the generator OEM specifications. The systems were easily installed and did not require a plant outage to integrate into the existing plant infrastructure. Figure 1 below depicts a typical general equipment arrangement within the plant.

Figures 2 and 3 below show the physical locations within the Riviera Power Plant where the onsite hydrogen generator and hydrogen monitoring and control system were installed.

Riviera’s Unit 3

Figure 1 – Typical Power Plant Arrangement

Figure 2 – Onsite Hydrogen Generator

Figure 3 – Hydrogen Control System

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EVALUATION TESTING

The proposed test plan for evaluating the hydrogen generation system and hydrogen control system is presented in Table 4 below. The test plan was designed to demonstrate the benefits of both systems in the power plant environment under actual generator operating conditions. A baseline was established by monitoring typical generator conditions under normal plant operations. The second testing period introduced a continuous supply of UHP hydrogen that was being generated from the onsite hydrogen generator. The electric power generator was then subjected to two sub-optimum operating conditions while the hydrogen control system monitored and actively controlled the hydrogen atmosphere within the generator casing TEST RESULTS

The initial baseline testing was conducted with the hydrogen monitoring and control system set up for continuous sampling with the control function turned off. The data that was collected over a one week period showed that the pressure within the generator casing was fluctuating as much as 5 psig. This fluctuation was the result of the “batch hydrogen feed” operation the plant was using to maintain hydrogen within the generator. Hydrogen purity was consistently greater than 98.5% during the monitoring period and hydrogen dew point was recorded to be between +16 and +24 degrees Fahrenheit. Figure 5A and 5B illustrate the results of the initial baseline testing. An initial gas sample was taken and sent to a laboratory for analysis by gas chromatography. The results of the analysis are presented in Table 5C.

The onsite hydrogen generator was put online and configured to supply a continuous flow of UHP hydrogen at the desired generator casing pressure in test period #2. Generator casing pressure was monitored and recorded. Figure 6A illustrates the improvement to pressure stability that was observed.


Table 4 – Evaluation Test Plan

Riviera Power Station Onsite Hydrogen Generation and StableFlow Hydrogen Control System Evaluation Test Plan

Period Description Mode of Operation

Hydro-gen

Supply Method

Data Logged by

PI and S/F Systems

1 Plant Baseline Monitoring Only

Batch Feed

Purity, Pressure, Dew point, Electrical load, Fuel Consump-tion, Blower differential pres-sure, Generator temps, Coolant temp in, Coolant temp out, Cool-ant flow

2 Introduce Onsite Hydrogen Supply

Monitoring and Control

Continu-ous Feed

3 Laboratory Gas Analysis Sample

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Introduce CO2 to Generator Casing to Lower Purity at Rated Casing Pressure

5 Introduce CO2 to Generator Casing to Lower Purity at Lower Casing Pressure

FPL - Riviera Plant Initial Monitoring

94.0

95.0

96.0

97.0

98.0

99.0

100.0

101.0

0 10 20 30 40 50 60 70 80 90

Data Pt (Hourly)

Pow

er G

ener

ator

H2

Purit

y (%

)

34.0

36.0

38.0

40.0

42.0

44.0

46.0

48.0

50.0

52.0

54.0

Pow

er G

ener

ator

H2

Pres

s. (p

sig)

H2 Purity H2 Pressure

FPL - Riviera Plant Initial Monitoring

0.0

5.0

10.0

15.0

20.0

25.0

0 10 20 30 40 50 60 70 80 90

Data Pt (Hourly)

H2

Dew

Poi

nt (°

F)

Dew Point

Figure 5a – Baseline Purity and Pressure

Figure 5b – Baseline Dew Point

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CO2 gas was used to lower the hydrogen purity in the

generator to 94% at 45 psig while being monitored and controlled for test period #4. The hydrogen purity was gradually improved during a ten day period as illustrated in Figure 6b below. The pressure within the generator casing remained stable and consistently within specification during the purity improvement period.

The hydrogen gas pressure was lowered to 35 psig

for a one week period and internal generator temperatures were monitored and logged to determine if gas pressure has an affect on cooling efficiency for test period #5. Figure 7 below illustrates the affect pressure has on generator temperatures. As illustrated, the delta temperature of the stator coolant inlet and outlet was measurably higher when the generator pressure was lower. This condition becomes important when the plant is


Figure 5c – Results of Initial Gas Analysis

Hydrogen Pressure Hourly DataFPL - Riviera Plant, Initial Monitoring, Bottle Gas Batch Feed

and subsequent HOGEN / StableFlow Operations

35

37

39

41

43

45

47

49

51

53

55

0 20 40 60 80 100 120 140 160 180 200

Data Pt (Hourly)

Bat

ch F

eed

H2

Pres

sure

(psi

g)

35

37

39

41

43

45

47

49

51

53

55

HO

GEN

/Sta

bleF

low

N

orm

aliz

ed H

2 Pr

essu

re (p

sig)

Batch Feed H2 Pressure Normalized H2 Pressure

Initial MonitoringPressure (psig): Min = 40.6 Max = 45.5 Average = 43.6 St. Dev. = 1.04 OEM Target = 45 psig

HOGEN / StableFlow Operations Normalized (psig): Min = 44.6 Max = 45.8 Average = 45.3 St. Dev. = 0.27 OEM Target = 45 psig

Figure 6a – Pressure Stability Improvement

FPL 94% Purity Reduction

93.0

94.0

95.0

96.0

97.0

98.0

99.0

100.0

101.0

102.0

0 50 100 150 200 250 300 350 400

Data Pt (Hourly)

H2

Puri

ty (%

)

H2 Purity

Figure 6b – Purity Improvement Test


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at full load and cannot provide the maximum possible generating capacity of the generator due to temperature limitations.

Measurements were taken during both test periods #4

and #5 to determine if there are any measurable affects on generator efficiency due to operating the generator at lower than specified hydrogen gas purity. The measurements that were taken show possible improvements to fuel flow, but due to the many variables that affect fuel flow in a steam plant it is impossible to determine what percentage is related to purity improvements. The chart pictured in Figure 8 is based on data provided by the Original Equipment Manufacturer (OEM) to illustrate the effect hydrogen gas purity has on Riviera’s unit #3 and #4. The chart shows that there is a 280kW loss with a hydrogen gas purity of 94% within the generator casing. The annual impact to Riviera Plant, if they operated their generator at this suboptimum level, could be as much as 2480 MWh lost.

It is important to understand that every electric power generator model has a specific purity vs loss curve. The generator OEM should be consulted to understand how hydrogen gas purity affects the efficiency of the specific electric power generator under consideration.

SUMMARY The introduction of onsite hydrogen generation and

hydrogen control at FPL’s Riviera Plant has demonstrated of improvements to the overall operation of the plant. A power plant that chooses to utilize onsite hydrogen generation will own a source of hydrogen to provide cooling gas to its generators at a low cost. A typical electrolyzer will consume less than 20 gallons a day of de-mineralized water and consume approximately 17kWh of electricity for every 100 cubic feet of hydrogen produced.

Continuously monitoring the hydrogen gas within the generator casing and actively controlling the quality of that gas at the Riviera Plant has proven to be a valuable piece of plant hardware. The affects on generator efficiency and capacity are measurable in most cases. The product testing and evaluation at the plant is still ongoing and will continue throughout the year. Areas such as fuel conservation and emissions reduction are certainly areas that deserve a closer and more detailed investigation. The impact of these improvements to the plant and to FPL’s utility system can add up to significant economic returns on the capital investment of this innovative technology. ACKNOWLEDGEMENTS John Speranza is Vice President of Commercial Sales at Wallingford, Conn.-based Proton Energy Systems, Inc. Eric Else is an Engineer at FPL Headquarters, Juno Beach, FL. Special thanks to Ken Stenroos of FPL for sponsoring the evaluation at Riviera Power Plant. Ken is PGD Electrical Team Manager at FPL headquarters, Juno Beach, FL. Special thanks to the skilled and dedicated plant personnel of Riviera Power Plant for their support and assistance in evaluating onsite hydrogen generation and control. Special thanks to Bill Bailey and Angelo Morson for their efforts in supporting the testing conducted at Riviera Power Plant, collecting data, and generating support documentation for this report. Bill Bailey and Angelo Morson are Senior Product Development engineers employed by Proton Energy Systems, Inc.


Figure 8 – Hydrogen Purity vs Efficiency

FPL Plant Data - 45 Psi Vs 35 Psi Gross MW and Cooling Oil Temperature Delta

0

50

100

150

200

250

300

0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00

Gro

ss M

W

0

10

20

30

40

50

60

Sta

tor C

oolin

g O

il In

let (

°C) a

nd S

tato

r Coo

ling

Oil

Inle

t an

d O

utle

t Tem

p. D

elta

(°C

)35 Psig Gross MW 45 Psig Gross MW 35 Psig Temp Delta 45 Psig Temp Delta

Delta T @ High Pressure

Delta T @ Low Pressure

Figure 7 – Pressure vs Temperature

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