Fuel and CO 2 Emissions Savings Calculation Methodology for Combined Heat and Power

Transcription

1 Fuel and CO 2 Emissions Savings Calculation Methodology for Combined Heat and Power Bruce Hedman ICF International IDEA 2012 Annual Conference, July 2, 2012

2 Advantages of CHP The simultaneous production of useful thermal and electrical energy in CHP systems leads to increased fuel efficiency. CHP units can be strategically located at the point of energy use. Therefore, avoiding the transmission and distribution losses associated with electricity purchased via the grid from central stations. The increase in overall fuel use efficiency generally translates to reductions in CO 2 emissions.

3 CHP is a Clean, Efficient Method of Providing Energy Services Source: EPA CHP Partnership

4 CHP s Increased Efficiency Generally Results in Lower Emissions Source: EPA CHP Partnership

5 How do I Calculate the Energy and CO 2 Savings of my CHP Project? CHP energy savings benefits are found in the aggregate reduction of overall fuel consumption compare the energy use and emissions of the CHP project to the energy use and emissions of supplying those same energy services with separate heat and power. Key factors in quantifying CHP savings: What is the energy use and emissions from displaced thermal energy? What is the energy use and emissions from avoided grid electricity?

6 What is the Recommended CHP Partnership Approach? Simple, straightforward approach to estimating the energy and CO 2 emissions benefits of CHP Based on readily available information Incorporates regional characteristics Focused on the savings of a specific project Not applicable to calculating carbon footprint or estimating corporate inventories

7 Calculating Fuel and CO 2 Emissions Savings from CHP Calculating Fuel Savings F S = (F T + F G ) F CHP Where: F S = total fuel savings F T = avoided fuel use from on-site thermal production F G = avoided fuel use from purchased grid electricity F CHP = fuel use by the CHP system. Calculating CO 2 Savings C S = (C T + C G ) C CHP Where: C S = total CO 2 savings C T = avoided CO 2 emissions from on-site thermal production C G = avoided CO 2 emissions from purchased grid electricity C CHP = CO 2 emissions from the CHP system

8 Fuel and Emissions Avoided at the Site Result from displacement of the energy otherwise used to provide heating or cooling services at the site. Savings calculated based on useful thermal output of CHP system and efficiency characteristics of avoided thermal equipment Where F T = CHP T / η T F T = avoided thermal fuel savings, MMBtu CHP T = CHP system useful thermal output, MMBtu η T = avoided thermal equipment efficiency, %

9 Fuel Use and Emissions Avoided at the Central Station Power Plant Fuel use from avoided central station generation F G = E G HR G Where F G = fuel use from avoided grid electricity, Btu (kj) E G = total grid generation avoided, kwh HR G = central station heat rate, Btu/kWh CO 2 emissions from avoided central station generation C G = E G EF G Where C G = CO 2 emissions from avoided grid electricity, lb (kg) E G = total grid generation avoided, MWh EF G = central station emission factor, CO 2 lb/mwh

10 How Much Electricity is Avoided at the Power Plant? Some of the electricity that is transmitted over power lines is lost due to resistance, referred to as transmission losses Avoiding 1 MWh of purchased electricity onsite means more than 1 MWh of electricity no longer needs to be generated at the central station power plant Typically, annual transmission losses are 7% to 10% E G = CHP E / (1 L T&D ) Where E G = grid generation avoided, kwh CHP E = CHP system electricity output, kwh L T&D = transmission and distribution losses, % Power Plant Transmission & Distribution Onsite CHP System Equivalent Energy

11 What are the Characteristics of Avoided Grid Electricity? Geographic factors what level of regional aggregation most accurately estimates the power supply in my area? Utility company, state, ISO, NERC region Heat rate and emissions factors what are the fuel and emissions factors for electricity avoided at the grid? Where do I get the data?

12 Emissions & Generation Resource Integrated Database (egrid) Globally recognized source of emissions data for electric power generated in the U.S. current edition is 2005 data Based on power plant specific data Plant identification and location Ownership Fuel use and heat rate Emissions (CO 2, CH 4, N 2 0, NO x, SO 2, Hg) Can be rolled into regional heat rates and emissions factors State, NERC region, egrid subregions

13 EPA egrid Sub-regions Recommended because: Sub-regions generally consist of one or a portion of a power control area, sectioning the grid into areas with similar emissions and resource mix Electric generating companies may purchase or export power to/from other generating companies State electricity generation may not serve all consumption within the state. Sub-regions may be partially isolated by transmission constraints

14 What Grid Power is Avoided by CHP Key factor in estimating the energy and CO 2 emissions savings from CHP Ultimate analysis would require time consuming dispatch modeling Options for estimating appropriate factors include: All-generation average (including nuclear and renewables) All-fossil average (weighted mix of fossil fuels) Non-baseload average (resource mix coincident with intermediate and peak demand) Average of a specific fuel type Estimate of marginal generation Projection of future installed generation

15 Recommended Approach to Avoided Grid Power Nuclear and renewable generation are likely must-run resources, and seasonal/daily variations in power supply and demand are generally met with changes in fossil generation CHP typically operates as intermediate ( hours) or base-load (>6500 hours) The egrid all fossil average heat rate and emissions factor are appropriate for baseload CHP The egrid non-baseload average heat rate and emissions factor are appropriate for non baseload CHP

16 Load Duration Curve Basic Dispatch Mix

17 Load Duration Curve

22 Impact of CHP

23 Impact of CHP

24 PJM Marginal CO 2 Emissions RFC Emissions (egrid data) All-Average: 1370 lb/mwh PJM CO 2 Emissions Rates of Marginal Units Versus Average CO 2 Emissions Rates Non-Baseload: 1879 lb/mwh Avg Fossil: 1963 lb/mwh

25 Example Calculation 5 MW Gas Turbine 5 MW natural gas-fired combustion turbine 8,497 hours per year (97% availability) Heat Rate = 12,590 HHV (27%) 42,485 MWh generated on-site 45,110 MWh avoided at power plant (5.8% T&D loss) Recoverable thermal energy is 5,000 Btu/kWh Displaces a natural gas-fired boiler (80% efficient) Located in Chicago (egrid sub-region is RFC West)

26 CHP Emissions Calculator - Input Document Document Introduction: Documentation: Emissions Calculator Emissions Calculator 1. CHP: Type of System 2. CHP: Electricity Generating Capacity (per unit) Normal size range for this technology is 1,000 to 40,000 kw 5 1 5,000 kw Submit Submit 3. CHP: How Many Identical Units (i.e., engines) Does This System Have? 4. CHP: How Many Hours per Year Does the CHP System Operate? 1 5 Submit As a number of hours per year OR As a percentage 5. CHP: Does the System Provide Heating or Cooling or Both? 8,497 0% 1 Submit 6. CHP: Fuel Fuel Type 1 View Biomass and Coal Fuel Characteristics Submit

27 CHP Emissions Calculator - Input 12. CHP: Electric Efficiency 1 I will enter an efficiency in one of the following blocks Enter Generating Efficiency as % OR Enter Generating Efficiency as Btu/kWh HHV OR Enter Generating Efficiency as Btu/kWh LHV Use default for this technology 27% (HHV) 12,590 Btu/kWh (HHV) 11,457 Btu/kWh (LHV) 14. CHP: NOx Emission Rate Use default emissions for this technology. I will enter a NOx rate in one Note: Default emissions are w ithout aftertreatment. Some areas may require addon controls and you w ill need to enter an emission rate based on your local of the following blocks 1 requirements. SCR can 2 reduce emissions by up to 90% Enter a NOx Rate as ppm (15% O 2 ) 25.0 ppm OR Enter a NOx Rate as gm/hp-hr - gm/hp-hr OR Enter a NOx Rate as lb/mmbtu lb NOx/MMBtu OR Enter a NOx Rate as lb/mwh lb NOx/MWh 15. Duct Burners: Does the System Incorporate Duct Burners? 1 2 Submit Use the Thermal Calculator to calculate my Power to Heat Ratio 16. Duct Burners: What is the Total Fuel Input Capacity of the Burners for Each CHP Unit? For reference, the Combustion Turbine has a heat input of 63. MMBtu/hr - MMBtu/hr Submit

28 CHP Emissions Calculator - Input 23. Displaced Thermal: Type of System: Displaced Thermal: What is the CO2 Emission Rate for this Fuel? (default completed for fuel in Item 23) Enter alternative value: lb CO2/MMBtu Submit 27. Displaced Thermal: Efficiency (usually a boiler) I will enter an efficiency Use default for this thermal technology Enter Generating Efficiency as % 80% 28. Displaced Thermal Production: NOx Emission Rate Submit I will enter the NOx rate NOx Rate Use default for NOx rate lb NOx/MMBtu Submit

29 CHP Emissions Calculator - Input 29. Displaced Electricity: Generation Profile Link to EPA's egrid (Emissions & Generation Resource Integrated Database) Displaced Electricity: Select U.S. Average or individual state or NERC region/subregion for EGRID Data Submit Displaced Electricity: Select Electric Grid Region for Transmission and Distribution (T&D) Losses Submit Link to EIA's Electric Grid Interconnection Map % Submit

30 CHP Emissions Calculator - Results CHP Results The results generated by the CHP Emissions Calculator are intended for eductional and outreach purposes only; it is not designed for use in developing emission inventories or preparing air permit applications. The results of this analysis have not been reviewed or endorsed by the EPA CHP Partnership. Annual Emissions Analysis CHP System Displaced Electricity Production Displaced Thermal Production Emissions/Fuel Reduction Percent Reduction NOx (tons/year) % SO2 (tons/year) % CO2 (tons/year) 31,273 46,197 15,575 30,499 49% Carbon (metric tons/year) 7,733 11,423 3,851 7,541 49% Fuel Consumption (MMBtu/year) 535, , , ,255 26% Number of Cars Removed 5,341 This CHP project will reduce emissions of Carbon Dioxide (CO2) by 30,499 tons per year This is equal to 7,541 metric tons of carbon equivalent (MTCE) per year This reduction is equal to removing the carbon emissions of 5,341 cars

31 CHP Emissions Calculator - Results Total Emissions for Conventional Production Total Emissions for CHP System tons of NOx tons of NOx tons of SO2.16 tons of SO2 61,772 tons of CO2 31,273 tons of CO2 42,485 MWh 452,830 MMBtu Electricity to Facility 535,043 MMBtu Fuel consumption Fuel Consumption 42,485 MWh Central Station No Cooling CHP Electricity Powerplant System to Facility 2,625 MWh Transmission Losses tons of NOx tons of NOx Thermal from CHP tons of SO2.16 tons of SO2 46,197 tons of CO2 31,273 tons of CO2 213,175 MMBtu 266,468 MMBtu Thermal to Fuel consumption Facility On-Site Thermal 213,175 MMBtu Production Thermal to Facility Absorption Chiller No Cooling tons of NOx.08 tons of SO2 15,575 tons of CO2

32 Example Calculation - 5 MW Gas Turbine RFC West Heat Rate and Emission Factors Central Station Mix Heat Rate, Btu/kWh CO2 Emissions, lbs/mwh All Generation 7,500 1,521 Non-Baseload 9,811 2,002 All Fossil 10,038 2,048

33 Example Calculation - 5 MW Gas Turbine Fuel and Emissions Savings Results Central Station Mix Fuel Savings, MMBtu/yr CO2 Savings, MMBtu/yr All Generation 69,749 18,599 Non-Baseload 174,001 29,452 All Fossil 184,255 30,499

34 Conclusions To quantify the fuel or CO 2 emissions savings of a CHP project, the fuel used and emissions released from the CHP system must be subtracted from the fuel used and emissions that would normally occur without the system (i.e., using conventional separate heat and power). To most accurately reflect the generation characteristics of avoided central station generation, the calculations should be based on: The heat rate and emissions factors from the EPA egrid subregion in which the CHP unit is located The all fossil average heat rate and emissions factor for baseload CHP (annual operating hours > 6500) The non-baseload average heat rate and emissions factor for non baseload CHP (annual operating hours < 6500)

35 Additional Information EPA CHP Partnership (CHPP) EPA CHPP Contact: Neeharika Naik-Dhungel Technical Support: Bruce Hedman ICF International