I-DEV0397: Deviation from the monitoring plan of the registered PDD :Change of monitoring frequency of parameters ‘heat rate’ and ‘combustion efficiency’

The monitoring plan, as detailed in Annex 4 to the PDD, stipulates as frequency for the heat rate measurements of the generator ‘semi annually, monthly if unstable’. The PP did not perform heat rate measurements during the first monitoring period (26 March 2009 – 31 August 2009).

The monitoring plan, as detailed in Annex 4 to the PDD, stipulates as frequency for the combustion efficiency measurements of the generator ‘semi annually, monthly if unstable’. The PP did not perform combustion efficiency measurements during the first monitoring period (26 March 2009 – 31 August 2009).

For the relevant monitoring period (26 March 2009 – 31 August 2009), the deviation does not require a request for revision, as it concerns the past.
It must be noted that the project participants are also proposing to revise the monitoring plan to reduce the required frequency for measuring the heat rate and combustion efficiency to less frequently than semi-annually. Given that acceptable justification for this is provided, DNV may submit a request for revision of the monitoring plan in parallel to this request for deviation.

Initial deviation request as submitted to the CDM Deviations panel on 8 February 2011:

As no heat rate values have been measured during first monitoring period, the PP decided to use in the ER calculations the heat rate value provided by the technology provider upon commissioning of the equipment. It is known that due to wear and tear of the combustion engines, the heat rate value tends to increase slowly with time. This has been confirmed by the PP during engine tests in August 2010, the reporting of which will be included in the first monitoring report. By using the lower, initial value (from the technology provider) in the ER calculations, the DOE confirms that the PP applies a conservative calculation approach, as the ‘primary calculation’ method (p 18 of PDD) implies a backward calculation departing from the amount of electricity which is generated.
The fact that no combustion efficiency data are available during the first monitoring period, does not impact the ER calculations, as it is actually not required in the formulas to calculate the emission reductions. However, as the parameter is mentioned in AM0010 (presumably for reasons of crosschecking the efficiency of the conversion of methane into carbondioxide), and accordingly mentioned in the PDD, the parameter is expected to be monitored. The fact that during this first monitoring period the combustion efficiency was not monitored is not deemed problematic by DNV, as the combustion engines were still new during the first monitoring period (4 engines were commissioned in April 2008 and 3 engines in July 2009), and as the site visit indicated that maintenance was properly implemented.
Moreover, it is known that there is a correlation between heat rate and combustion: when combustion efficiency decreases, heat rate values tend to increase. Hence, if there would have been a problem with the combustion efficiency, this would not have gone unnoticed during the heat rate measurements which took place in August 2010.

Answers to the questions raised on 9 March 2011 by the CDM Deviations panel
On 9 March 2011 various comments were received from the CDM Deviations panel. Below answers are provided to these questions. For easy reference, the reply text has the same structure as the questions received:

1- The DOE is requested to:

a) Specify the dates when the heat rate of the generator and the combustion efficiency of the engines have been measured from the start of the first monitoring period to the present day;

During the first monitoring period (26 March 2009 – 31 August 2009) no measurements for heat rate nor combustion efficiency were made. The heat rate has been subsequently tested in May and August 2010 (cf. attached files 1 and 2). The combustion efficiency was not measured to date as it is not required in the formulas to calculate the emission reductions.

b) Indicate the values obtained for the parameters heat rate and combustion efficiency during each of the measurements performed;

The average heat rate was 9 605kJ/kWh as determined during the May 2010 testing, and 10 000kJ/kWh as determined during the August 2010 testing. Detailed reports of both tests are attached. The increase in the heat rate from May 2010 to August 2010 is in line with the general expectation that the engines become less efficient with time. The measured values are higher than the heat rate of 9 358 kJ/kWh, the value which is used in the emission reduction calculations. This means that the emission reduction calculations were performed with a conservative heat rate value (=more efficient engine compared to reality).
The combustion efficiency was not measured to date as it is not required in the formulas to calculate the emission reductions.

c) Indicate since when the measurements of the aforesaid parameters have been performed in line with the monitoring frequency, as determined in the monitoring plan of the registered PDD and in the applied methodology.

Since May 2010 the engine heat rate is being measured in line with the monitoring frequency as determined in the monitoring plan of the registered PDD.

2- The DOE has indicated that the initial heat rate value from the technology provider would be used for emission reductions calculations. However, the heat rate value was not provided in the deviation request form. In addition, there is a contradiction between the value provided in the registered PDD (page 18) and the value provided in the spread sheet (Appendix 1- Enclosure a, of the PDD). The DOE is requested to clarify the heat rate value that will be used for emission reduction calculations and how this value will lead to conservative emission reductions.

The PDD referenced a heat rate value of 14 000 kJ/kWh. This figure was based upon a worst case for a 0.5 MW engine (www.chpcentermw.org/pdfs/toolkit/rules_of_thumb.pdf, BTUs were converted into kJ). For reasons of conservativeness a lower figure of 9 358 kJ/kWh (meaning a more efficient engine) has been used in the spreadsheet calculations.
The origin of the value of 9 358 kJ/kWh is explained in attachments 3,4 and 5 to this deviation request. The approach basically interpolates an appropriate value (= at nominal power production) derived from heat rate certificates provided by the technology provider upon commissioning of the engines.

3- Since the applied methodology states that emission reductions shall be determined (ex post) by metering of the actual quantity of methane captured and used for electricity generation and that the methane destroyed by the project activity (MDprojecty) during a year shall be determined by monitoring the quantity of methane used to generate electricity, the DOE is requested to clarify:

a) How the indirect "primary calculation method" for estimation of emission reductions mentioned in the PDD (page 18) and in the deviation request, is in line with the applied methodology; and how this calculation will lead to conservative emissions reductions;

In the registered PDD two calculation methods were described: the “primary method” (PM) and the “quality assurance method” (QAM). The PM is intended to be used on a systematic basis, whereas the QAM is intended to be used to check and calibrate the outcome of the PM, the latter being an indirect method which is based on the electricity generated, and not on measuring the biogas flow nor the methane content in the flow. As the CDM project does not claim emission reductions from flaring, the rationale behind the PM is deemed valid and appropriate by the DOE. The fact that the PM can be cross checked by the QAM, is in the DOE’s opinion sufficient guarantee that the PM is in line with AM0010, provided that the result of the PM is conservative compared to the result of the QAM. The latter is the case for the first monitoring round. The outcome of this comparison is provided in attachment 6; a similar comparison will be provided by the PP in each subsequent monitoring report and the lower of the two values would be used.

b) How the "quality assurance method" indicated in the PDD (page 20) complies with the quality assurance purposes since it includes the methane quantity captured and sent to flares.

The QAM is suitable for crosschecking the result of the PM, as in the QAM the methane destroyed during flaring is subtracted (cf. cells D42 till D46 of emission reduction spreadsheet). The QAM calculated emission reductions without the flaring component, are the correct reference base for cross checking the PM calculated emission reductions.

4- While supporting its argumentation, the DOE is requested to provide credible evidence and/or references, particularly with regard to:

a) The heat rate value which, according to the DOE, tends to increase slowly over time due to wear and tear of the combustion engines.

In attachment 7 the relationship between time, engine efficiency and maintenance is substantiated. The technology provider confirms that the engine heat rate will slowly increase over time, relative to what it was initially when each engine was first installed. This is due to the normal wear and tear of the engines. After maintenance, efficiency will improve but not necessarily to the original newly installed level.

b) The correlation between heat rate and combustion, i.e. when combustion efficiency decreases, heat rate values tend to increase.

In attachment 7 the relationship between combustion efficiency and heat rate value, is substantiated as follows: Due to wear and tear the heat rate will slowly increase; the engine combustion efficiency will concomitantly gradually reduce.