battery gas emission calculation

Battery Gas Evolution & Accumulation & Minimum Ventilation Calculation

I. OBJECTIVE, METHOD and STUDY CASE

1.3. Study Case

The Batteries will be located on Electrical Equipment Building (EEB)The EEB is 2 (two) levels building, layout and dimension as follows:

Level Room Description Length, L (m)Width, W

(m)Height, H

(m)Level 1 Transformer Room 23 5.5 5Level 1 MV Switchroom 23 4.5 5Level 2 Main Switchroom 11.5 10 5Level 2 Emergency Switchroom 6 10 5

Note:- EEB level 1 and level 2 share the same HVAC unit area, the total HVAC area ventilation are combined

LEVEL 1 - EEB

LEVEL 2 -EEB

1.1. Calculation objective

- Determine maximum expected quantities of flammable gas evolution under the most adverse charging conditions for electrical battery systems- Determine minimum time for gas accumulation to 50% LEL at zero ventilation, in order to ascertain hazardous area requirements- Determine minimum ventilation requirements to meet IEE requirements for rooms containing batteries and confirm compliance

1.2. Calculation method

Empirical formulae and manufacturer's recommendationsVentilation calculation as per IEE 1992 Section 14.16

23m4.

5m5.

5m

10m

TRANSFORMER ROOM

MV SWITCHROOM

5.5m 6m 11.5m23m

10m

MAIN SWITCHROOMEMERGENCY

SWITCHROOMEE

BH

VA

C U

NIT

Section-1page 1 of 2

The UPS Batteries data as follow:

Tag No DescriptionC10 Rating

(Ah)C3 Rating

(Ah)

Battery Type(Vendor

Data)

Bat-01A Switchgear Supply - 110 VDC Battery Bank A 275 204 2V275Bat-01B Switchgear Supply - 110 VDC Battery Bank B 275 204 2V275Bat-02A GTG-01 - 120 VDC Battery Bank A 200 148 2V200Bat-02B GTG-02 - 120 VDC Battery Bank B 200 148 2V200Bat-02C GTG-03 - 120 VDC Battery Bank C 200 148 2V200Bat-03A Main UPS (230 VAC) - Battery Bank A 400 297 2V400Bat-03B Main UPS (230 VAC) - Battery Bank B 400 297 2V400Bat-04A EDG-01 - 24 VDC Battery Bank 200 148 2V200Bat-05A Nav Aids - Battery Bank 320 269 2V320

Note:- Batteries data is based on PowerSafe V (VRLA Batteries) Vendor data on Appendix-2- C1 and C3 rating is taken from battery data at EOD = 1.8 VDC, 20

0C

- Boost Charge will not be apply to VRLA batteries, to maintain it's lifetime- Battery Maximum Charging current is limmited up to 0.3 of it's C10 rating in Ampere (note: normal operation is about 0.1 of C10)

- HVAC temperature is maintain and assummed to be 20 0C

EEB Level 2 - Emergency SwitchroomEEB Level 2 - Emergency Switchroom

BatteryLocation

EEB Level 1 - MV SwitchroomEEB Level 1 - MV SwitchroomEEB Level 1 - MV SwitchroomEEB Level 1 - MV SwitchroomEEB Level 1 - MV Switchroom

EEB Level 2 - Main SwitchroomEEB Level 2 - Main Switchroom

Section-1page 2 of 2


2.1. Battery Type and Installation

Batteries are of the sealed valve regulated lead acid (VRLA) type. They are to be installed on racks or within individual enclosures andsuitably ventilated to comply with the requirements in the IEE Recommendations for Electrical and Electronic Equipmenton Mobile and Fixed Offshore Installations, 1992 (to be denoted IEE(1992) herein).

2.2. Battery Capacities

Battery capacities for UPS and DC power suply system are based on typical Vendor data in Appendix-2.The maximum number of cells in series is based on the maximum tolerable output voltage and the recommended floating voltage.

2.3. Minimum Ventilation Requirements

The following equation derived from clause 14.16(1) of IEE (1192) is used to calculate the minimum ventilation requirements

Minimum Ventilation,

Where, n is the number of cells in series per battery systemI is the battery charging current (A)

The total ventilation requirement for a room containing more than one charger and battery system is determined by summation ofthe individual ventilation requirements of all battery systems in the room.

The ventilation of the switchroom is based on the fresh air make-up of the total area serviced by the HVAC system as contaminatedair is being recirculated with fresh air throughout the whole area, not just the switchroom.

2.4. Hydrogen Gas Accumulation

The H2 gas accumulation calculation determines the amount of time required for the batteries to produce enough H2 to reach 50% of

the gas lower explosive limit in the absence of ventilation system and at maximum charge rate.The result is determined from typical H2 gas evolution manufacturer data for VRLA type batteries and typical C3 Ah value from manufacturer data

The calculation includes the summated hydrogen evolution from all batteries within each room

II. CALCULATION BASIS

100011 InQs

=

Section-2Page 1 of 1


The following example calculations show how the minimum ventilation requirements and hydrogen gas evolution value inthe calculation sheets are derived.The battery capacity requirement is based on study case in section 1.3

3.1. Electrical Equipment Building Ventilation Requirements

The Electrical Equipment Building contains five battery systems, 2 units 110 VDC Supply Battery System for Switchgear (Bat-01A and Bat-01B), 3 units 120 VDC GTG Back-up LO Pump Battery System (Bat-02A, Bat-02B and Bat-02C), 2 units 230 VAC Main UPSBattery System (Bat-03A and Bat-03B), 24 VDC Battery System for Diesel Generator and Nav Aids (Bat-04A and Bat-05A)The ventilation requirements of the electrical equipment building are determined by summation of the ventilation requirements of the individual battery systems

3.1.1. Example Calculation

- Main UPS 230 VAC Battery Bank Ventilation Requirement (Tag No. Bat-03A)Assuming a float DC voltage (between the rectifier and inverter of the UPS) of

Vndc = VDC

And a nominal float voltageVf = VDC / cell

The maximum number of cells in series required per battery isnmax = Vndc / Vf = cells per battery

From preliminary Vendor data on section 1.3, UPS batteries require a C10 Ah capacity ofC10 = Ah

It is assumed the maximum charging current is limited to 0.3 of C10 battery capacity in Ampere.

(assumption is to demonstrate high charging current, in normal condition VRLA batteries will not be boost charge to maintain it's lifetime,and normally will use 0.1 of C10 which will take 10hours to reach 80% recharge. See battery catalogue in appendix-2)

Taking the value of C10 as per vendor data in section 1.3, the maximum UPS batteries charge current is thenImax = x 400 = 120 A

The minimum ventilation requirements for the main UPS-A battery, given the maximum charge current and themaximum number of cells is

= m3/hr

3.1.2. Calculations Table Summary for Battery Bank Ventilation RequirementAssumming:Vf = VDC / cellImax = x C10 battery capacity in AmpereVndc = assumed as listed in table bellow

141.247.92

12.67515.93

38.2838.2838.28

141.24

121.5 54 82.5

Vndc(V DC)

nmax(cells/batt)

Q(m3/hr)49.0149.01

Imax(A)

6096

120120

6060

54 82.560

107585858

26.4 1212

107

130130242242

121.5130

Bat-04ABat-05A

200200400400200320

Bat-02BBat-02CBat-03ABat-03B

Tag No

Bat-01ABat-01BBat-02A

275275200

2.28

Description

Switchgear Supply - 110V DC Battery Bank ASwitchgear Supply - 110V DC Battery Bank BGTG-01 - 120V DC Battery Bank A

0.3

242

2.28

III. Calculations

26.4

107

400

0.3

141.24

C10 Rating(Ah)

EDG-01 - 24V DC Battery Bank

TotalNav Aids - Battery Bank

GTG-02 - 120V DC Battery Bank BGTG-03 - 120V DC Battery Bank C Main UPS (230V AC) - Battery Bank AMain UPS (230V AC) - Battery Bank B

100011 maxmax InQUPS

=


3.1.3. Total Electrical Equipment Building Ventilation Requirements

The total Electrical Equipment Building ventilation requirements ( QT-EEB ) are,

Q T-EEB = Q01A + Q01B + Q02A + Q02B + Q02C + Q03A + Q03B + Q04A + Q04B = m3/hr

The design Elect. Equip. Building service area ventilation rate (refer to HVAC calculation in Appendix-1) is

Q A = Q R-LEV1 + Q R-LEV2 = m3/hr

Therefore the design ventilation rate of the room is times the required minimum ventilation rate due to the batteries system

The ratio of Minimum Ventilation / Room Ventilation is

3.2. Electrical Equipment Building Hydrogen Gas Accumulation

The Electrical Equipment Building is sub-divided into 2 levels, 4 section rooms, which is Transformer Room and MV Switchroomon Level-1, and Main Switchroom and Emergency Switchroom on Level-2.The hydrogen gas contributions of each batteries system are calculated individually and then summed based on it's locationto determine the total gas accumulation for each room.

3.2.1 MV Switchroom - Electrical Equipment Building Level-1MV Switchroom contains five batteries system; 2 units of 110VDC supply system battery banks for switchgear supply (Bat-01A,and Bat-01B) and 3 units of GTG DC Back UP Lube Oil (Bat-02A, Bat-02B and Bat-02C).

- Example Calculation - 110 VDC Battery Bank A (Bat-01A)

From typical manufacturer's data in appendix-2, the rate of hydrogen gas emission (of VRLA batteries during float charge of 2.28V) isG = ml per cell per C3 Ah per month (based on vendor data in Appendix-2)

The maximum number of cells in series required per battery isnmax = cells per battery (from section 3.1.2)

The battery C3 Ah capacity for the 110VDC Supply system from typical manufacturer data in section 1.3 isC3 = Ah

The H2 gas evolution of the 110 VDC Supply system batteries is then

G01A = G x nmax x C3 = ml per month

= m3/day (assumed 1 month = 30 days)

- Calculation Table Summary for Hydrogen Gas Accumulation - MV Switchroom (EEB Level-1)Assumming:

G = ml per cell per C3 Ah per monthnmax = as calculated in section 3.1.2

The total MV Switchroom hydrogen gas accummulation are, GTot-MVSR = m3/day

Based on calculation on Appendix-1, the MV Switchroom has approximate volume as, VR-MVSW = m3

Assumming a lower explosive limit factor, ke (percentage by volume), the time taken to reach 50% lower explosive limit is

days

515.93

1823.4

3.53

28.29%

3.7

54

204

40759

0.00136

3.7


(Ah)nmax

(cells/batt)

Bat-01A Switchgear Supply - 110 VDC Battery Bank A 204 54Bat-01B Switchgear Supply - 110 VDC Battery Bank B 204 54Bat-02A GTG-01 - 120 VDC Battery Bank A 148 58

0.001060.00106Bat-02C GTG-03 - 120 VDC Battery Bank C 148 58

Bat-02B GTG-02 - 120 VDC Battery Bank B 148 58

G(m3/day)

0.001360.001360.00106

Total 0.0059

0.0059518

10050

5.0 =tot

ReLEL G

VkT


with ke = 4%then, the time taken to reach 50% lower explosive limit for MV Switchrom is

MV Switchroom = days or 4.81 years (assumming 1 year = 365 days)

3.2.2 Main Switchroom - Electrical Equipment Building Level-2Main Switchroom contains two batteries system; 2 units of 230 VAC Main UPS (Tag.No. Bat-03A and Bat-03B)Repeating the procedure in section 3.2.1

- Calculation Table Summary for Hydrogen Gas Accumulation - Main Switchroom (EEB Level-2)Assumming:


The total MV Switchroom hydrogen gas accummulation are, GTot-MainSR = m3/day

Based on calculation on Appendix-1, the MV Switchroom has approximate volume as, VR-MainSW = m3

with ke = 4%then, the time taken to reach 50% lower explosive limit for Main Switchrom is

Main Switchroom = days or 4.02 years (assumming 1 year = 365 days)

3.2.3 Emergency Switchroom - Electrical Equipment Building Level-2Emergency Switchroom contains two batteries system; 1 unit of DEG Battery Systems (Tag.No. Bat-04A) and 1 unit of Nav Aids Battery System (Tag. No. Bat-05A)Repeating the procedure in section 3.2.1

- Calculation Table Summary for Hydrogen Gas Accumulation - Emergency Switchroom (EEB Level-2)Assumming:


The total MV Switchroom hydrogen gas accummulation are, GTot-MainSR = m3/day

Based on calculation on Appendix-1, the MV Switchroom has approximate volume as, VR-MainSW = m3

with ke = 4%then, the time taken to reach 50% lower explosive limit for Emergency Switchrom is

Emerg. Switchroom = days or 26.5 years (assumming 1 year = 365 days)

Note:The H2 gas accumulation calculation results in section 3.2 are the amount of time required for the batteries to produceenough H2 to reach 50% of the gas lower explosive limit in the absence of ventilation system and at maximum charge rate

of 0.3 times C10 battery capacity in Ampere.

0.00022Bat-05A Nav Aids - Battery Bank 269 12 0.0004Bat-04A EDG-01 - 24 VDC Battery Bank 148 12

575

1467

nmax(cells/batt)

G(m3/day)

3.7


(Ah)

0.00392Total 0.00784

0.00784

Bat-03B Main UPS 230 VAC Battery Bank B 297 107

G(m3/day)

Bat-03A Main UPS 230 VAC Battery Bank A 297 107 0.00392

1756

3.7


(Ah)nmax

(cells/batt)

9677

Total 0.00062

0.00062300

10050

5.0 =tot

ReLEL G

VkT

10050

5.0 =tot

ReLEL G

VkT

10050

5.0 =tot

ReLEL G

VkT



(note 2, 3)

(note 2, 3)

(note 2, 3)

Notes:1. Electrical Equipment Building Level-1 and Level-2 share the same HVAC service area, hence the minimum ventilation

calculations are combined

2. The H2 gas accumulation calculation results are the amount of time required for the batteries to produce enough H2to reach 50% of the gas lower explosive limit in the absence of ventilation system and at maximum charge rates of0.3 times C10 battery capacity in Ampere.

3. 50% LEL is calculated by assumming a lower explosive limit of ke percentage by volume is 4%

Conclusions:

1. The VRLA Batteries does not require a separate battery room since the hydrogen accummulation will take long timeto reach 50% LEL even in the absence of ventilation system, i.e. hydrogen accummulation can be negligible

2. The ventilation requirements for rooms containing batteries confirm compliance to meet IEE requirements

Minimum Ventilation /Room Ventilation

( % ) ( years )

Time to reach 50% LEL

4.81

4.02

28.29%

28.29%

26.51

(note 1)

IV. CALCULATION SUMMARY

28.29%

Main Switchroom - Elect. Equipment Building, Level-2 (note 1)

Emergency Switchroom - Elect. Equipment Building, Level-2 (note 1)

ROOM NAME

MV Switchroom - Elect. Equipment Building, Level-1


APPENDIX - 1

HVAC Calculations

1. HVAC Service Volumes and Room Volumes

Table-1 HVAC Service Volumes Calculations (refer to section 1.3 for EEB layout)

Table-2 Electrical Room Volumes Calculation (for room containing batteries only)

2. Room Ventilation

Assuming:- The minimum of air changes per hour of electrical rooms: (data can get from HVAC philosophy)

Na = 6 air changes/hour- A minimum fresh air rate per air change of:

Kf = 15 % fresh air rate per air changeThe fresh air ventilation rate of each room and HVAC service area is given by

QR = VR x Na x Kf / 100 (Room Ventilation rate)and QA = VT x Na x Kf / 100 (Total HVAC Ventilation rate)

HVAC Notes: (refer to HVAC design philosophy)- All enclosed areas of the platform shall be adequately ventilated by the HVAC systems.- The HVAC systems shall be sized to suit the required number of air changes per hour as per standard- The minimum requirement for fresh air/make up air quantities introduced into HVAC systems shall be determined in accordance with ASHRAE Standard 62, Ventilation for Acceptable Indoor Air Quality.

Table 3. Room Ventilation Calculation

Note:1. EEB Level-1 and EEB Level-2 share the same HVAC Electrical Equipment Building area,

the total HVAC area ventilation are combined

Volume (VT) L x W x H (m3)

Room Description Length, L (m)Width, W

(m)Height, H

(m)633

EEB Level-1 (MV Switchroom) 23 4.5 5 518EEB Level-1 (Transformer Room) 23 5.5

EEB Level-2 (Main Switchroom) 11.5 10

5

Volume (VR) L x W x H (m3)

Total HVAC Service Volume Area for Elect. Equip. Building 2026

5 575EEB-Level-2 (Emergency Switchroom) 6 10 5 300

Room Description Length, L (m)Width, W

(m)Height, H

(m)5 518

EEB Level-2 (Main Switchroom) 11.5 10 5 575EEB Level-1 (MV Switchroom) 23 4.5

Room DescriptionRoom Ventilation,

QR (m3/hr)

Total HVAC Area Ventilation QA (m

3/hr)

300EEB Level-2 (Emergency Switchroom) 6 10 5

(note 1)EEB Level-2 (Main Switchroom) 517.50 1823.4 (note 1)EEB Level-1 (MV Switchroom) 466.20 1823.4

(note 1)EEB Level-2 (Emergency Switchroom) 270.00 1823.4

Appendix-1Page 1 of 1

APPENDIX - 2

1. Enersys PowerSafe V - Battery Data

2. Enersys PowerSafe V - Charging Current Note 3. Enersys PowerSafe V - Hydrogen Emissions

4. Enersys PowerSafe V - LEL factor ke

battery gas emission calculation

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