I-DEV0315: Deviation regarding the measurement of steam flow for the purposes of determining steam quantity discharged from the geothermal wells.

The Lihir Geothermal Power Project (LGPP) was registered on 29th May 2006, with the first monitoring period commencing 5th June 2006. The approved baseline and monitoring methodology used is ACM0002 version 04.

The current verification is going on for the 3rd monitoring period from 1st October 2007 to 31st August 2008. During the verification, this was observed that the steam meter installed on the steam line for 33MW turbines was failed. DOE raised the CAR for the same. This has been verified that the project proponent has commissioned the meter on 28th October 2009. Hence, the deviation for failure of steam meter is being requested for the period starting from 26th March 2008 to 27th October 2009.

The request for deviation covers the below mentioned procedures for the deviation period. The procedure relates for determining steam quantity discharged from the geothermal wells for the said period:

Monitoring the quantity of steam produced during year y (MS,y): due to a failure of the flow meter in one of the main supply lines.
For the above mentioned required change, the reason for the deviation and the proposed deviation method is outlined in detail below.

1. Quantity of steam produced during year y (MS,y)(Back-up Method)

The LGPP was developed in two stages. The ‘33MW’ (31.7MW net) plant comprising 3 x 11MWe steam turbine-generator sets was developed first, followed by the ‘22MW’ (21.1 MW) plant comprising an additional 2 x 11MWe steam turbine-generator sets.

Geothermal Steam for the LGPP is obtained from underground reservoirs accessed through steam wells located over the 2 km2 area of the Lihir basin. The wells, via connecting pipe, deliver steam to the main supply lines to the LGPP and the 6MW pilot geothermal plant (constructed prior to the LGPP and part of the baseline scenario). There are separate supply lines to the 6MW, 33MW and 22MW plants with crossovers between the lines used to balance steam supply in the system.

Reason for the Deviation

In accordance with the approved monitoring plan, steam flow to the LGPP is metered using flow meters installed on each of the 33MW (tag # PGS: S100_FTn_011_TOTn ) and 22MW (tag # PGS: S400_FTn_011_TOTn) main supply lines before the inlet to the power station. Total steam for the 55MW is then calculated as the sum of the two meter readings. The meters are located downstream of the crossovers between each of the supply lines, and therefore the individual flow meters record the total steam flow going to the 33MW, or 22MW plant, regardless of the wells that the steam is obtained from. Data is recorded on a continuous basis in the PI System , the mine’s event and data management platform.

On 26th March 2008 (half way through the 3rd monitoring period) the flow meter in the 33MW steam line failed and needs to be replaced. This requires a complete shutdown of the LGPP and steam gathering network for a period of approximately 7 days. As the LGPP is critical to the operation of the mine it is not possible to undertake such a long non-scheduled shutdown. The meter will therefore be replaced at the next scheduled shutdown in August 2009 .

The proposed deviation to the monitoring plan was therefore developed in order to accurately monitor the quantity of steam produced during year y (MS,y) in the absence of the 33MW flow meter readings.

Proposed Deviation

The steam that is delivered to the LGPP is consumed in the five turbines and the stage 1 and stage 2 steam jet ejectors (one each on each of the five turbines) which are used to draw non-condensable gases out of the steam. It is therefore possible to calculate the total steam consumed in the LGPP by calculating the steam consumed in the turbines and adding the steam drawn through the ejectors as follows:

• Turbine Steam Consumption: Turbine steam consumption is proportional to the output of the generator (power produced in MW). Based on the metered power output, and the turbine performance curves supplied by the turbine manufacturer at the time of purchase the steam consumption is therefore calculated using the following method:

The 24 hour average generation (MW) of each of the five turbines on each suitable day in a month is entered is obtained from the Daily Power Station report, and summed to get the total daily 24 hour generation for the LGPP. This value is entered into the monitoring spreadsheet.

The total daily 24 hour generation fluctuates throughout the month, and in order to be conservative, the maximum value for the month is identified, and taken as the daily 24 hour average generation (MW) for each day in that month and used to determine the corresponding total steam flow for that month. Selecting the maximum daily 24 hour generation, and using this for each day in the month ensures that the steam consumption is conservative and an overestimation of the amount of steam consumed in the month. As the standard operating procedures used at the LGPP are to control well steam flow via throttling at the wellhead based on power station demand, the maximum generation of the LGPP corresponds to maximum steam flow discharging from the wells at any time.

A suitable day is defined as a day where there is stable generation over the 24 hour period with the vent valves closed at the end of the 24 hour period (as indicated in the Power Station Daily Report) and wellhead valves in the same state as the previous day. Where one or more vent valves are open on the maximum generation day, additional steam (based on the maximum capacity of each vent valve and number of valves open) will be added to the calculated turbine steam consumption and applied for the entire month. Where there are no stable 24 hour generation periods (minimum and maximum within 10% of the daily average) for the month, the total steam flow is based on the total steam flow if all five vent valves were fully open for the month. This ensures the most conservative approach is always taken based on reliable data.

QA/QC: Real power produced by each of the five turbines is monitored continuously and recorded in the PI system. The data records are retrievable at any time. The data for 24 hour average generation (MW) has been submitted by the proponent that is collated and circulated in the Power Station Daily Report for review and checking by relevant LGPP senior staff. This is standard operating procedure for the LGPP irrespective of the CDM monitoring plan. The metered power generation data is the same data that is used to calculate the emission reductions (EGy, power plant) has been reported in the spreadsheet which is verified and found to be correct (Ref 4).

The energy meters were manufactured under an ISO9001 registered system and conform to IEC 947-1, IEC 1010-1. As stated in the PDD, they have an accuracy of within 1% and are maintained and regularly calibrated by the Process Plant Maintenance Department Instrumentation section. This has been verified from the calibration certificates of the energy meters submitted by the proponent during verification of 3rd monitoring period.

The turbine performance curves for the turbines submitted by the proponent are prepared based on standard performance testing as part of standard procurement practices for purchasing a turbine. The Turbine Manual supplied by the manufacturer includes graphs depicting expected performance under varying conditions of steam flow rate, inlet pressure, NCG content, exhaust pressure, and generator power factor. The turbine performance curves as given in the Turbine Manual have been verified and inserted in the steam flow excel sheet sheets by the proponent for reference (Ref-4) & (Ref-5). This has been found acceptable.

• Ejector steam flow: Ejector steam flow is dependent on the ejector inlet setting. To be conservative ejector flow rate is taken as constant irrespective of turbine output, and is based on flow rates recorded during the full load performance testing. These values are representative of the maximum flow that would be seen through the ejectors and were verified with the ejector full load performance test sheet. This is evidenced by the ejector flow trend data recorded in 2009 in the PI system (results attached in file 0279_LGPP_Ejector Steam Flow Supporting Data.xls) which shows that sample trend values are consistently lower than those recorded during full load performance testing. In addition, the values used are higher than the specified flow rate provided by the manufacturer as evidenced by the Ejector Data Sheet.pdf provided by the proponent. The stage 1 and 2 ejectors used for each of the 5 turbines are the same and the ejector flow rate is multiplied by five to get the total ejector flow rate for the 55MW plant. Using the maximum ejector steam flow rate accounts for any steam losses over the line, and is the approach adopted by LGL to determine total steam produced by the wells.

QA/QC: The results of the full load performance testing of ejectors have been provided by the proponent and were verified (Ref-1) & (Ref-2). Full load performance testing was undertaken immediately after the LGPP was commissioned when all instruments were calibrated and new. A constant value is used throughout the deviation period to ensure conservatism.

The method for determining the quantity of steam produced represents a deviation from the methodology ACM0002 version 04 used in the registered PDD for the current monitoring period.

Due to the failure of Venturi flow meter, the PP has replaced the faulty meter with a new flow meter. The replacement of meter was undertaken during the site shutdown in August 2009. The pressure tapping points for the meter were installed in September 2009 and DOE has verified that the new meter was commissioned on 28th October 2009.

The proposed deviation applies to the current monitoring period from 26th March 2008 (when the meter failed) until 31st August 2008. In addition, the project proponent wished to apply the deviation upto 27th October 2009 which is the part of 4th monitoring period as well because the meter was commissioned on 28th October 2009. Hence, the deviation is requested for the deviation period from 26th march 2008 until 27th October 2009.

The proposed deviation does not require a revision in monitoring plan or the changes from the project activity as described in the registered project design document. This has been verified that the flow meter in the 33MW steam line failed and needs to be replaced. The replacement of meter was undertaken during the site shutdown in August 2009 and the meter was commissioned on 28th October 2009. This confirms that the changes from the registered monitoring plan is not permanent (the proposed deviation to the monitoring plan was developed in order to accurately monitor the quantity of steam produced during year y (MS, y) in the absence of the 33MW flow meter readings for a particular period) and will not require a revision in monitoring plan or the changes from the project activity as described in the registered project design document.

In line with the applied methodology ACM 0002 version 04, registered PDD and approved revised monitoring plan (http://cdm.unfccc.int/Projects/DB/DNV-CUK1143246000.13/view) the steam quantity discharged from the geothermal wells should be measured with a venturi flow meter (or other equipment with at least the same accuracy) but on 26th March 2008, the flow meter in the 33MW steam line failed. To determine the steam quantity produced during year y, (MS, y), the proponent has used the back up procedure (the proposed deviation to the monitoring plan). As per the registered PDD and approved revised monitoring plan, the baseline emissions (BEy in tCO2) are the product of the baseline emissions factor (EFy in tCO2/MWh) times the electricity supplied, by the project activity, to the grid (EGy in MWh). Therefore, there is no impact of the back up procedure as explained above on baseline emission calculations.
Conservativeness of the proposed deviation:
As per the registered PDD (page 30), it was envisaged that steam vented as a component of mining operations was sufficient to power the 55MW (52.8MW net) capacity of the LGPP. Therefore, (PESy) was assumed to be zero. Project emissions from the combustion of fossil fuels related to the operation of the geothermal power plants in tons of CO2 (PEFFy) were also assumed to be zero. Thus project emissions (PEy) in the registered PDD were zero.

However, during the third monitoring period some of the steam used in the LGPP was sourced from well heads drilled specifically for power generation and as a result the non-condensable gases in this steam need to be counted as project emissions. This scenario was considered a possibility in the registered PDD and outlined on pages 19 and 30.

The well numbers (unique identification number) drilled specifically for power generation and the dates that they were commissioned are shown in the table below (Ref-6):

Well No - Date Commissioned
• 48 - 03 June 2007
• 49 - 18 March 2008
• 51 - 01 May 2008
• 53 - 07 May 2008
• 56 - 25 July 08

NOTE: WHEN INSERTING THE INFORMATION FOR THIS DEVIATION WE ENCOUNTERED DIFFICULTIES WITH THE FORMATTING OF ABOVE DATA SETS. PLEASE REFER TO (Ref-7) TABULAR REPRESENTATION OF THE ABOVE INFORMATION IN .PDF FILE.


Note: Well number 48 was originally drilled for mining operation purposes as verified during second verification period i.e. 01st October ‘06 to 30th September ‘07 (http://cdm.unfccc.int/Projects/DB/DNV-CUK1143246000.13/iProcess/SGS-UKL1191924815.58/view). However, due to poor performance of the well which resulted in a uncertainty as to its role in depressurization, Well 48 was conservatively reclassified as a well drilled to provide steam for power generation during the third monitoring period and the non-condensable gases in this steam quantified as project emissions


The impact of the proposed deviation on the following parameters compared to the direct metering approach for the period 1st October 2007 to 25th March 2008 (the dates of the third verification period when the steam flow meter was functional) are shown in the table below:

1. Quantity of steam measured (t/day)
2. Project emissions from the non-condensable gases in the steam sourced from well heads drilled specifically for power generation (PESy)
3. Emission reductions
As project emissions from the combustion of fossil fuels related to the operation of the geothermal power plants in tons of CO2 (PEFFy) are zero when the steam is sourced from well heads drilled specifically for power generation, project emissions PEy are equal to PESy.

Parameter/Emission - Direct Metering(Ref-4) / Proposed Deviation(Ref-5) / Variation (%)
• Steam (t/day) - 489,116.40 / 496,761.88 / 1.56%
• Project Emissions (PESy) - 2,155 / 2,293 / 6.40%
• Emission Reductions - 102,885 / 102,747 / 0.13%

NOTE: WHEN INSERTING THE INFORMATION FOR THIS DEVIATION WE ENCOUNTERED DIFFICULTIES WITH THE FORMATTING OF ABOVE DATA SETS. PLEASE REFER TO (Ref-7) TABULAR REPRESENTATION OF THE ABOVE INFORMATION IN .PDF FILE.



As the above comparison indicates the back-up method proposed in this deviation results in a higher quantity of steam measured, which in turn results in a higher estimate of project emissions and a more conservative estimate of emission reductions compared to the direct metering method.
The period 1st October 2007 to 25th March 2008 is the only period that the two methods can be compared as from 26th March 2008 to 31st August 2008 the steam meter failed and hence direct metering was not possible. During the first two verifications periods steam was sourced from wells drilled as a component of mining operations and thus project emissions (PESy) were zero.

Revision to the monitoring plan and relationship with this deviation:

During the third monitoring period some of the steam used in the LGPP was sourced from well heads drilled specifically for power generation and as a result the non-condensable gases in this steam need to be counted as project emissions. This scenario was considered a possibility in the registered PDD and outlined on pages 19 and 30. However, only limited detail is contained in the registered PDD on the approach to calculate project emissions from the non-condensable gases in the steam from wells drilled specifically for power generation. Hence, a revision to the monitoring plan is being submitted to the CDM Executive Board to provide a definite approach to this issue.

To calculate project emissions from the non-condensable gases in the steam from wells drilled specifically for power generation, the quantity of steam is required to be monitored. This will be undertaken in accordance with:

• This request for deviation for the period 1 October 2007 to 27 October 2009 only.
• The revised monitoring plan for all subsequent periods.