R/fuel_correction.R

In gtfs2emis: Estimating Public Transport Emissions from General Transit Feed Specification (GTFS) Data

#' @title 
#' Correction factor equation
#'
#' @description 
#' Relations between emissions and fuel properties for diesel heavy-duty 
#' vehicles based on EMEP/EEA. Function based on values from the [EMEP/EEA air pollutant emission inventory guidebook 2019](https://www.eea.europa.eu/themes/air/air-pollution-sources-1/emep-eea-air-pollutant-emission-inventory-guidebook).
#' Estimates are given by the ratio between correction factor of improved fuel 
#' by the correction factor of base fuel.    
#' 
#' @param pollutant character. Pollutant classified in "CO", "VOC", "NOx" or 
#'        "PM10".
#' @param euro_stage character. EURO period of vehicle, classified in "PRE", "I", 
#'        "II", "III", "IV", "V" and "VI".
#' @param improved_fuel numeric. Numeric vector for characteristics of an 
#'        improved fuel, ordered by: den (Density at 15 degrees C), s (Sulphur 
#'        content in ppm), pah (Polycyclic aromatics content in \%), cn (Cetane 
#'        number), t95 (Back end distillation in degrees C). Default input uses
#'        c(den = 835, s = 40, pah = 5, cn = 53, t95 = 320).
#' 
#' @return numeric. A fuel correction factor.
#' 
#' @keywords internal
fuel_correction <- function(pollutant, euro_stage, improved_fuel = c(den = 835, s = 40, pah = 5, cn = 53, t95 = 320)){
  
  # checking----
  # pollutant
  checkmate::assert_vector(pollutant,any.missing = FALSE,min.len = 1,null.ok = FALSE)
  checkmate::assert_character(pollutant,any.missing = FALSE,min.len = 1)
  for(i in pollutant) checkmate::assert_choice(i,c("CO","VOC","NOx","PM10"),null.ok = FALSE)
  # euro_stage
  checkmate::assert_vector(euro_stage,any.missing = FALSE,min.len = 1,null.ok = FALSE)
  checkmate::assert_character(euro_stage,any.missing = FALSE,min.len = 1)
  for(i in euro_stage) checkmate::assert_choice(i,c("PRE", "I", "II", "III", "IV", "V", "VI"),null.ok = FALSE)
  # improved_fuel
  checkmate::assert_vector(improved_fuel,any.missing = FALSE,len = 5,null.ok = FALSE)
  checkmate::assert_numeric(improved_fuel,any.missing = FALSE,len = 5)
  for(i in names(improved_fuel)) checkmate::assert_choice(i,c("den","s","pah","cn","t95"),null.ok = FALSE)
  
  # relation between fuel properties and emissions
  
  fcorr_list <- list(
    "CO" = function(den, pah, cn, t95, s = 0)
    {2.24407 - 0.0011 * den + 0.00007 * pah - 0.00768 * cn - 0.00087 * t95},
    "VOC" = function(den, pah, cn, t95, s = 0)
    {1.61466 - 0.00123 * den + 0.00133 * pah - 0.00181 * cn - 0.00068 * t95},
    "NOx" = function(den, pah, cn, t95, s = 0)
    {-1.75444 + 0.00906 * den - 0.0163 * pah + 0.00493 * cn + 0.00266 * t95},
    "PM10" = function(den, pah, cn, t95, s = 0)
    {(0.06959 + 0.00006 * den + 0.00065 * pah - 0.00001 * cn) * (1 - 0.0086 * (450 - s)/100)}
  )
  
  #
  # base fuel -----
  #
  
  base_fuel <- data.table::data.table("veh_type"    =   c("PRE", "I", "II", "III", "IV", "V", "VI"),
                                      "base_fuel"    =  c(1996, 1996, 2000, 2005, 2005, 2005, 2005),
                                      "improved_fuel" = c(2005, 2005, 2005, 2005, 2005, 2005, 2005))
  
  #
  # diesel properties --------
  #
  
  diesel_fuel <- data.table::data.table("den" = c(840, 840),
                                        "s" = c(400, 300),
                                        "pah" = c(9, 7),
                                        "cn" = c(51, 53),
                                        "t95" = c(350, 330),
                                        "year" = c(1996, 2000))
  
  input_fuel <- data.table::as.data.table(t(improved_fuel))
  input_fuel[, year := 2005]
  diesel_fuel <- rbind(diesel_fuel, input_fuel)
  
  #
  # diesel fuel specifications ------
  #
  
  temp_year <- base_fuel[data.table::as.data.table(euro_stage),
                         on = c("veh_type" = "euro_stage")]
  temp_year[diesel_fuel, on = c("base_fuel" = "year"),
            paste0(c('den', 's', 'pah', 'cn', 't95'), "_base") := .(i.den, i.s, i.pah, i.cn, i.t95)]
  temp_year[diesel_fuel, on = c("improved_fuel" = "year"),
            paste0(c('den', 's', 'pah', 'cn', 't95'), "_imp") := .(i.den, i.s, i.pah, i.cn, i.t95)]
  
  lapply(seq_along(pollutant), function(i){ # i = 1
    temp_year[, (paste0(pollutant[i], "_base")) := 
                fcorr_list[pollutant[i]][[1]](den_base, pah_base, cn_base, t95_base, s_base)]
    temp_year[, (paste0(pollutant[i], "_imp")) := 
                fcorr_list[pollutant[i]][[1]](den_imp, pah_imp, cn_imp, t95_imp, s_imp)]
    temp_year[, (paste0("fcorr_", pollutant[i])) := 
                get(paste0(pollutant[i], "_imp")) / get(paste0(pollutant[i], "_base")) ]
    return(NULL)
  }) 
  
  fcorr <- temp_year[, .SD, .SDcols = (paste0("fcorr_", pollutant))]
  
  return(fcorr)
}