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CHP in the E3 GHG Model Proposed Changes for Stage 2. April 1, 2008. Process Notes. Presentation describes the E3 proposed approach for including CHP in Stage 2 Hoping for consensus on reference case cost, performance, and penetration inputs

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CHP in the E3 GHG Model Proposed Changes for Stage 2

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CHP in the E3 GHG ModelProposed Changes for Stage 2

April 1, 2008

Process Notes

  • Presentation describes the E3 proposed approach for including CHP in Stage 2

  • Hoping for consensus on reference case cost, performance, and penetration inputs

  • Sensitivity analysis can be done by users and inputs can be changed to evaluate alternative cases

  • All parties will have the opportunity to comment


  • CHP in E3 Stage 1 Model

  • Key CHP issues

    • CHP regulatory status under AB32

    • Data availability

    • Thermal/electric split

    • On-site/grid export split

  • E3 Proposed Stage 2 model changes

    • Existing CHP

    • Adding new CHP

    • Reference case cost & performance assumptions

  • EPUC/CAC proposed assumptions

CHP in Stage 1 Model

  • Stage 1 model contains the CHP units that are in the WECC databases

  • Stage 1 model does not specify CHP generation as a separate category

  • Stage 1 model does not have a way to add new CHP generation

  • Parties requested E3 to add CHP as separate category

  • E3 requested help from parties in identifying CHP units in the WECC databases

CHP Regulatory Status under AB32

  • CARB’s GHG inventory treats CHP as a separate category from non-CHP generation

  • However, CARB considers part of CHP emissions to be included in CA’s “electricity sector” - i.e. all those that are not associated with “useful thermal output”

  • Currently, CARB considers emissions associated with “useful thermal output” to be point source emissions, not electricity sector emissions, so separately regulated

  • CARB reviewing approach to CHP regulation and reporting - status could change

Data Availability

  • Major data shortcomings for CA CHP

    • No single source that has capacity, generation, and emissions for all CA CHP

    • Different capacity size cutoffs for different databases

    • Little reliable data for small (<1 MW) CHP

    • WECC databases don’t identify CHP units

    • Difficult to match EIA Form 920 list to WECC names

    • Unclear if WECC CHP heat rates are net or gross

  • E3 model makes assumptions about existing CHP based on best available data

Thermal/Electric Split

  • Emissions for thermal and electric regulated separately under current scheme

  • CARB inventory split based on EIA Form 920 (generation & fuel use) and predecessor data

  • EIA methodology changed ca. 2003, changing the split significantly

    • CARB emissions % electric 1990-2003: 63%

    • CARB emissions % electric 2004: 78%

  • What is a reasonable thermal / electric split?

On-Site/Grid Export Split

  • EIA and CARB do not distinguish on-site (i.e. behind the meter) from grid export generation

  • CEC estimates on-site non-PV generation in load forecast, data reliability and overlap with EIA/CARB data uncertain

  • Plexos does not model on-site generation

  • What is reasonable assumption for on-site/grid export split for existing CHP fleet?

Proposed Changes in Stage 2 Model

  • Add CHP as new generation option

  • Account for CHP generation and emissions separately from non-CHP generation

  • Provide user controls for cost, performance, and penetration assumptions for user cases

  • Provide user controls for thermal/electric and on-site/on-grid splits for user cases

  • Separate treatment of existing and new CHP

Existing CHP in Stage 2 Model

  • On-site CHP: generation already embedded in load forecast so no adjustment is necessary

  • On-grid CHP: many CHP units are not identified in WECC database, so CHP fleet generation is underestimated in the Plexos model

  • This is corrected by adjusting CHP fleet generation and emissions to hit expected values based on historical data

    • Existing CHP generation and emissions in Plexos summarized, then adjusted in E3 calculator to expected value

    • Non-CHP generation decremented by the same amount in E3 calculator

CHP Data for 2003 & 2004

CA CHP Capacity by Unit Size

Source: EEA database, 2006 data

Existing CHP Expected Values

  • Units < 5 MW (380 MW, 30% c.f.) generation estimated at 1000 GWh, assumed all on-site

  • CEC self-gen ~ 11,000 GWh, so ~ 10,000 GWh from units > 5 MW and 1,000 GWh from units < 5 MW

  • 10-year average EIA total CHP generation and CARB emissions show no trend, so can use for expected CHP

    • generation: 44,000 GWh

    • emissions: 30 MMT

    • electric share of generation and emissions: 63%

  • Use CHP net heat rate implied in EIA data to be consistent with CARB’s present methodology; however, calculator will track thermal fuel use efficiency proposed by CAC/EPUC

Existing CHP Expected Values

Formulation of Existing CHP Adjustment

Col A

Col B

Col C

Col D =


Col E=

B+D= A

Col F=


New CHP in Stage 2 Model

  • Two categories of new CHP

    • > 5 MW nameplate = “Large” CHP (cogen)

    • < 5 MW nameplate = “Small” CHP (self-gen)

    • Division at 5 MW based on SGIP criteria

  • Characteristics of large CHP represented by 40 MW gas turbine

  • Characteristics of small CHP represented by 3 MW gas reciprocating engine

E3 Proposed2020 BAU Reference Case Assumptions

E3 Proposed2020 Aggressive Ref Case Assumptions

E3 ProposedNew CHP Cost and Performance Assumptions


EPUC/CAC Existing CHP Data

Thank YouAny Questions?

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