impact_model.rb

Copyright © 2010 Brighter Planet. See LICENSE for details. Contact Brighter Planet for dual-license arrangements.

 

      		
    

    

      
        

          
        

        
Meeting carbon model



This model is used by Brighter Planet’s carbon emission web service to estimate the greenhouse gas emissions of a meeting (e.g. a conference).



Timeframe and date



The model estimates the emissions that occur during a particular timeframe. To do this it needs to know the meeting’s date. For example, if the timeframe is January 2010, a meeting that occurred on January 11 2010 will have emissions but a meeting that occurred on Febraury 1 2010 will not.



Calculations



The final estimate is the result of the calculations detailed below. These calculations are performed in reverse order, starting with the last calculation listed and finishing with the emission calculation. Each calculation is named according to the value it returns.



Methods



To accomodate varying client input, each calculation may have one or more methods. These are listed under each calculation in order from most to least preferred. Each method is named according to the values it requires. If any of these values is not available the method will be ignored. If all the methods for a calculation are ignored, the calculation will not return a value. “Default” methods do not require any values, and so a calculation with a default method will always return a value.



Standard compliance



Each method lists any established calculation standards with which it complies. When compliance with a standard is requested, all methods that do not comply with that standard are ignored. This means that any values a particular method requires will have been calculated using a compliant method, because those are the only methods available. If any value did not have a compliant method in its calculation then it would be undefined, and the current method would have been ignored.



Collaboration



Contributions to this carbon model are actively encouraged and warmly welcomed. This library includes a comprehensive test suite to ensure that your changes do not cause regressions. All changes should include test coverage for new functionality. Please see sniff, our emitter testing framework, for more information.

      		
      
        
require 'conversions'

module BrighterPlanet
  module Meeting
    module ImpactModel
      def self.included(base)
        base.decide :impact, :with => :characteristics do

      		
    

    

      
        

          
        

        
Emission calculation



Returns the emission estimate (kg CO2e). This is the total emission produced by the meeting venue.

      		
      
        
          committee :carbon do

      		
    

    

      
        

          
        

        
Emission from duration, area, and emission factor

      		
      
        
            quorum 'from duration, area, and emission factor', :needs => [:duration, :area, :emission_factor],

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Multiplies area (square m) by duration (seconds) and the emission factor (kg CO2e / square m hour) to give kg CO2e.

      		
      
        
                characteristics[:duration] / 3600.0 * characteristics[:area] * characteristics[:emission_factor]
            end
            

      		
    

    

      
        

          
        

        
Default emission

      		
      
        
            quorum 'default' do

      		
    

    

      
        

          
        

        
Displays an error if the previous method fails.

      		
      
        
              raise "The emission committee's default quorum should never be called"
            end
          end
          

      		
    

    

      
        

          
        

        
Emission factor calculation



Returns the emission factor (*lbs CO2e / square m hour).

      		
      
        
          committee :emission_factor do

      		
    

    

      
        

          
        

        
Emission factor from fuel intensities and eGRID

      		
      
        
            quorum 'from fuel intensities and eGRID', :needs => [:natural_gas_intensity, :fuel_oil_intensity, :electricity_intensity, :district_heat_intensity, :egrid_subregion, :egrid_region],

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Calculates an energy-based emission factor for natural gas by dividing its co2 emission factor (kg / cubic m) by its energy content (MJ / cubic m) to give kg CO2 / MJ

      		
      
        
                natural_gas = Fuel.find_by_name "Pipeline Natural Gas"
                natural_gas_energy_ef = natural_gas.co2_emission_factor / natural_gas.energy_content
                

      		
    

    

      
        

          
        

        
Calculates an energy-based emission factor for fuel oil by dividing its co2 emission factor (kg / l) by its energy content (MJ / l) to give kg CO2 / MJ

      		
      
        
                fuel_oil = Fuel.find_by_name "Distillate Fuel Oil No. 2"
                fuel_oil_energy_ef = fuel_oil.co2_emission_factor / fuel_oil.energy_content
                

      		
    

    

      
        

          
        

        
Calculates an energy-based emission factor for district heat by dividing the energy-based natural gas emission factor by 0.817 and the energy-based fuel oil emission factor by 0.846 (to account for boiler inefficiencies), averaging the two, and dividing by 0.95 (to account for transmission losses) to give kg CO2 / MJ

      		
      
        
                district_heat_ef = (((natural_gas_energy_ef / 0.817) + (fuel_oil_energy_ef / 0.846)) / 2) / 0.95 # kg / MJ
                

      		
    

    

      
        

          
        

        
Calculates an electricity emission factor by dividing the eGRID subregion electricity emission factor by 1 – the eGRID region loss factor (to account for transmission and distribution losses) to give kg CO2 / kWh

      		
      
        
                electricity_ef = characteristics[:egrid_subregion].electricity_emission_factor / (1 - characteristics[:egrid_region].loss_factor)
                

      		
    

    

      
        

          
        

        
Multiplies natural gas intensity (cubic m / room-night) by the volume-based natural gas emission factor (kg CO2 / room-night), fuel oil intensity (l / room-night) by the volume-based fuel oil emission factor (kg CO2 / l), electricity intensity (kWh / room-night) by the electricity emission factor (kg CO2 / kWh), and district heat intensity (MJ / room-night) by the energy-based district heat emission factor (kg CO2 / MJ), and adds these together to give kg CO2 / room-night.

      		
      
        
                (characteristics[:natural_gas_intensity] * natural_gas.co2_emission_factor) +
                (characteristics[:fuel_oil_intensity] * fuel_oil.co2_emission_factor) +
                (characteristics[:district_heat_intensity] * district_heat_ef) +
                (characteristics[:electricity_intensity] * electricity_ef)
            end
          end
          

      		
    

    

      
        

          
        

        
Natural gas intensity calculation



Returns the meeting venue’s natural gas intensity (cubic m / square m hour).

      		
      
        
          committee :natural_gas_intensity do # returns cubic metres per square metre hour

      		
    

    

      
        

          
        

        
From census division

      		
      
        
            quorum 'from census division', :needs => :census_division, 

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the census division meeting building natural gas intensity (cubic m / square m hour).

      		
      
        
                characteristics[:census_division].meeting_building_natural_gas_intensity
            end
            

      		
    

    

      
        

          
        

        
Default natural gas intensity

      		
      
        
            quorum 'default',

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do

      		
    

    

      
        

          
        

        
Uses the U.S. average natural gas intensity (cubic m / square m hour).

      		
      
        
                CensusDivision.fallback.meeting_building_natural_gas_intensity
            end
          end
          

      		
    

    

      
        

          
        

        
Fuel oil intensity calculation



Returns the meeting venue’s fuel oil intensity (l / square m hour).

      		
      
        
          committee :fuel_oil_intensity do

      		
    

    

      
        

          
        

        
Fuel oil intensity from census division

      		
      
        
            quorum 'from census division', :needs => :census_division,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the census division meeting building fuel oil intensity (l / square m hour).

      		
      
        
                characteristics[:census_division].meeting_building_fuel_oil_intensity
            end
            

      		
    

    

      
        

          
        

        
Default fuel oil intensity

      		
      
        
            quorum 'default',

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do

      		
    

    

      
        

          
        

        
Uses the U.S. average fuel oil intensity (l / square m hour).

      		
      
        
                CensusDivision.fallback.meeting_building_fuel_oil_intensity
            end
          end
          

      		
    

    

      
        

          
        

        
Electricity intensity calculation



Returns the meeting venue’s electricity intensity (kWh / square m hour).

      		
      
        
          committee :electricity_intensity do

      		
    

    

      
        

          
        

        
Electricity intensity from census division and eGRID region

      		
      
        
            quorum 'from eGRID region and census division', :needs => [:egrid_region, :census_division],

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
    

  • Looks up the census division meeting building electricity intensity (kWh / square m hour)
    • 

  • Looks up the eGRID region loss factor
    • 

  • Divides the electricity intensity by 1 – the loss factor to account for electricity transmission and distribution losses
    • 


      		
      
        
                characteristics[:census_division].meeting_building_electricity_intensity / (1 - characteristics[:egrid_region].loss_factor)
            end
            

      		
    

    

      
        

          
        

        
Electricity intensity from eGRID region

      		
      
        
            quorum 'from eGRID region', :needs => :egrid_region,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
    

  • Uses the U.S. average meeting building electricity intensity (kWh / square m hour)
    • 

  • Looks up the eGRID region loss factor
    • 

  • Divides the electricity intensity by (1 – the loss factor) to account for electricity transmission and distribution losses
    • 


      		
      
        
                CensusDivision.fallback.meeting_building_electricity_intensity / (1 - characteristics[:egrid_region].loss_factor)
            end
          end
          

      		
    

    

      
        

          
        

        
District heat intensity calculation



Returns the meeting venue’s district heat intensity (MJ / square m hour)

      		
      
        
          committee :district_heat_intensity do

      		
    

    

      
        

          
        

        
District heat intensity from census division

      		
      
        
            quorum 'from census division', :needs => :census_division,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the census division meeting building district heat intensity.

      		
      
        
                characteristics[:census_division].meeting_building_district_heat_intensity
            end
            

      		
    

    

      
        

          
        

        
Default district heat intensity

      		
      
        
            quorum 'default',

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do

      		
    

    

      
        

          
        

        
Uses the U.S. average.

      		
      
        
                CensusDivision.fallback.meeting_building_district_heat_intensity
            end
          end
          

      		
    

    

      
        

          
        

        
eGRID region calculation



Returns the meeting venue’s eGRID region.

      		
      
        
          committee :egrid_region do

      		
    

    

      
        

          
        

        
eGRID region from eGRID subregion

      		
      
        
            quorum 'from eGRID subregion', :needs => :egrid_subregion,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the eGRID subregion eGRID region.

      		
      
        
              characteristics[:egrid_subregion].egrid_region
            end
          end
          

      		
    

    

      
        

          
        

        
eGRID subregion calculation



Returns the meeting venue’s eGRID subregion.

      		
      
        
          committee :egrid_subregion do

      		
    

    

      
        

          
        

        
eGRID subregion from zip code

      		
      
        
            quorum 'from zip code', :needs => :zip_code,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the zip code eGRID subregion.

      		
      
        
                characteristics[:zip_code].egrid_subregion
            end
            

      		
    

    

      
        

          
        

        
Default eGRID subregion

      		
      
        
            quorum 'default',

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do

      		
    

    

      
        

          
        

        
Uses an artificial eGRID subregion that represents the U.S. average.

      		
      
        
                EgridSubregion.find_by_abbreviation 'US'
            end
          end
          

      		
    

    

      
        

          
        

        
Census division calculation



Returns the meeting venue’s census division.

      		
      
        
          committee :census_division do

      		
    

    

      
        

          
        

        
Census division from state

      		
      
        
            quorum 'from state', :needs => :state,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the state census division.

      		
      
        
                characteristics[:state].census_division
            end
          end
          

      		
    

    

      
        

          
        

        
State calculation



Returns the meeting venue’s state.

      		
      
        
          committee :state do

      		
    

    

      
        

          
        

        
State from zip code

      		
      
        
            quorum 'from zip code', :needs => :zip_code,

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do |characteristics|

      		
    

    

      
        

          
        

        
Looks up the zip code state.

      		
      
        
                characteristics[:zip_code].state
            end
          end
          

      		
    

    

      
        

          
        

        
Zip code calculation



Returns the meeting venue’s zip code.



Zip code from client input



Complies: All



Uses the client-input zip code.

      		
      
        
          

      		
    

    

      
        

          
        

        
Area calculation



Returns the meeting venue’s area (square m).

      		
      
        
          committee :area do

      		
    

    

      
        

          
        

        
Area from client input



Complies: All



Uses the client-input area (square m).

      		
      
        
            

      		
    

    

      
        

          
        

        
Default area

      		
      
        
            quorum 'default',

      		
    

    

      
        

          
        

        
Complies: GHG Protocol Scope 3, ISO 14064-1, Climate Registry Protocol

      		
      
        
              :complies => [:ghg_protocol_scope_3, :iso, :tcr] do

      		
    

    

      
        

          
        

        
Uses a default area of 1,184.5 square m. This is the average size of meeting buildings in the EIA Commercial Building Energy Consumption Survey.

      		
      
        
                10_448.square_feet.to(:square_metres)
            end
          end
          

      		
    

    

      
        

          
        

        
Duration calculation



Returns the meeting’s duration (seconds). This is the number of seconds the meeting venue is in use. For example, a two-day conference that runs 8 hours each day would have a duration of 57600.

      		
      
        
          committee :duration do

      		
    

    

      
        

          
        

        
Duration from client input



Complies: All



Uses the client-input duration (seconds).

      		
      
        
            

      		
    

    

      
        

          
        

        
Default duration

      		
      
        
            quorum 'default' do

      		
    

    

      
        

          
        

        
Uses a default duration of 28800 seconds (8 hours).


      		
      
        
              28800.0
            end
          end
        end
      end
    end
  end
end