R/carbon-intensity.r

In jkeirstead/decctools: Get Energy Data from the UK Dept of Energy and Climate Change

#' Gets mix of fuel sources in UK electricity
#'
#' Gets the mix of fuel sources used to generate UK grid electricity
#' between specified dates.  Valid dates are yyyy-mm-dd and must be
#' between 2009-01-01 and the current day; the start must come before
#' the end date.
#'
#' @source The underlying data come from BM Reports,
#' \url{http://www.bmreports.com/bsp/bsp_home.htm}, and are used under
#' license from Elexon (see disclaimer below). However the BM Reports
#' website is hard to use and so this function uses archived Elexon
#' data compiled by the charity Renewable Energy Foundation and
#' available at no cost at \url{http://www.ref.org.uk/fuel/}.
#'
#' ELEXON does not and shall not be deemed to warrant or guarantee or
#' make any representation (whether expressly or impliedly) as to the
#' title, completeness, accuracy, reliability, freeness from error,
#' method of preparation, merchantability or fitness for the purpose
#' or for any particular purpose (whether or not any such purpose has
#' been notified to ELEXON) of the Licensed Data and/or any use of or
#' dealing with it.  ELEXON shall have no liability or responsibility
#' whatsoever or howsoever arising (whether directly or indirectly) as
#' a result of or in connection therewith, including in respect of
#' each and all loss of profits, loss of revenue, loss of goodwill,
#' loss of contracts, loss of business or production, indirect loss,
#' economic or consequential loss, claims, demands, proceedings,
#' actions, losses, liabilities, damages, costs, charges and expenses
#' (whether or not any of the foregoing are foreseeable)
#'
#' @param start the start date for retrieving data.
#' @param end the end date for retrieving data
#' @return a data frame with a datetime stamp and average power
#' generated by fuel type in MW
#' @examples
#' # These require a working internet connection
#' start <- "2010-01-01"
#' end <- "2010-01-03"
#'
#' # Gets data for 1-3 January 2010
#' data <- get_grid_mix(start, end) 
#' 
#' @export
#' @import stringr XML RCurl
get_grid_mix <- function(start, end) {

    ## Check if we have a working internet connection
    base_url <- "http://www.ref.org.uk/fuel/tablebysp.php?valdate="
    
    if (!url.exists(base_url)) {
        warning("The website containing the data you've requested is currently down.  Please try again later.")
        return(NULL)
    }

    ## Coerce strings to proper dates
    start <- as.Date(start)
    end <- as.Date(end)
    
    ## Validate inputs
    first_date <- as.Date("2009-01-01")
    last_date <- get_last_date()
    template <- "Invalid %s date.  Must be between %s and %s."
    if (start < as.Date("2009-01-01") | start > last_date) {
        stop(sprintf(template, "start", first_date, last_date))
    }
    
    if (end < as.Date("2009-01-01") | start > last_date) {
        stop(sprintf(template, "end", first_date, last_date))
    }

    if (end < start) stop("End date before start date.  Try again.")

    ## Create a sequence of dates
    dates <- seq(start, end, by="day")

    ## Load the data from the REF website
    tmp <- list(length(dates))
    columns <- c("character","numeric", rep("FormattedNumber", 14))
    
    for (i in 1:length(dates)) {
        url <- paste(base_url, dates[i], sep="")
        table <- suppressWarnings(readHTMLTable(url, colClasses=columns)[[2]])
        tmp[[i]] <- table
    }
    data <- do.call("rbind", tmp)
    
    ## Tidy things up
    names(data) <- str_trim(names(data))

    ## Convert date format into something more sensible
    data <- mutate(data, datetime=as.POSIXct((data$SP-1)*30*60, origin=data$SD))

    ## Rearrange
    data <- data[,c(17, 3:15)]
    return(data)
}


#' Calculates the carbon intensity of electricity generation
#'
#' Calculates the carbon intensity of electricity generation in the UK
#' between specified dates.
#'
#' @seealso \code{\link{get_grid_mix}} and
#' \code{\link{carbon_intensities}} for data sources
#' @param start the start date for retrieving data.
#' @param end the end date for retrieving data
#' @return a data frame with a datetime stamp and average carbon
#' intensity of electricity measured in kg CO2/kWh
#' @examples
#' # These require a working internet connection
#' start <- "2010-01-01"
#' end <- "2010-01-03"
#' # Gets grid carbon for 1-3 January 2010
#' carbon <- get_grid_carbon(start, end) 
#' 
#' @export
#' @import reshape2 
#' @importFrom plyr mutate ddply summarize
get_grid_carbon <- function(start, end) {

  ## Get the grid mix data for this period
  data <- get_grid_mix(start, end)

  ## Need the grid mix data to proceed
  if (is.null(data)) return(NULL)
  
  ## Merge with carbon intensities data for each fuel type
  carbon_intensities <- NULL # R CRAN check hack
  data(carbon_intensities, envir=environment())
  data.m <- melt(data, id="datetime")
  data.m <- merge(data.m, get("carbon_intensities"), by.x="variable", by.y="fuel")

  ## Calculate the total emissions in kg CO2
  ## cif = g CO2/kWh so value must be converted from MW in a half-hour period to kWh
  tmp <- mutate(data.m, emissions=(data.m$value*0.5)*1000*data.m$cif/1000)

  ## Now sum back up for a single time period
  tmp2 <- ddply(tmp, c("datetime"), summarize,
                demand=sum(get("value")*0.5*1000), total_em=sum(get("emissions")))
  result <- summarize(tmp2, datetime=tmp2$datetime, cif=tmp2$total_em/tmp2$demand)
  return(result)
}
  

#' Gets the most recent date for available data
#'
#' Gets the date of the last update to the REF fuels mix database.
#'
#' @return a Date object.  If the REF website is unavailable, it will
#' return today's date on the assumption that once it's back up, it
#' will be up-to-date.
#' @import lubridate RCurl
get_last_date <- function() {
  
    base_url <- "http://www.ref.org.uk/fuel/tablebysp.php"

    if (!url.exists(base_url)) {
        return(Sys.Date())
    }
    
    columns <- c("character","numeric", rep("FormattedNumber", 14)) 
    table <- suppressWarnings(readHTMLTable(base_url, colClasses=columns)[[2]])
    last_date <- as.Date(as.character(tail(table$SD, 1)))

    ## If the table isn't showing the data for some reason (which does
    ## happen), revert to the last day of the previous month
    if (length(last_date)==0) {
        tmp <- Sys.Date()
        day(tmp) <- 1
        day(tmp) <- day(tmp)-1
        last_date <- tmp
    }
      
    return(last_date)
}