116 lines
4.0 KiB
Ruby
116 lines
4.0 KiB
Ruby
#
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# Obtain energy prices from Entsoe (transparancy platform)
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# See https://transparency.entsoe.eu/content/static_content/Static%20content/web%20api/Guide.html
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#
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require 'open-uri'
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require 'nokogiri'
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class Entsoe
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URL = 'https://transparency.entsoe.eu'
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attr_accessor :no_grid_charge_months, :zone
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attr_reader :storage_cost
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def initialize(zone = "Amsterdam", storage_cost = 0.05, api_key = "c2287e07-0c26-4950-b430-22b7f75a8f2e")
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@api_key = api_key
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@kwh_prices = {}
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@storage_cost = storage_cost # how much does it cost to store 1 kwh in battery
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@no_grid_charge_months = [5,6,7] # months where we assume there is enough surplus from sun power
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@zone = zone
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end
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def price_at(formatted_hour)
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unless @kwh_prices.key?(formatted_hour)
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p "Fetching Entsoe tariffs for %s" % formatted_hour
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prices = query_day_ahead_prices(Date.parse(formatted_hour))
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@kwh_prices.merge!(hourly_format(prices))
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end
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@kwh_prices[formatted_hour]
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end
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def prices_at(date)
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hour_start = date.beginning_of_day.in_time_zone(@zone)
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day_end = hour_start.advance(days: 1)
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result = {}
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while(hour_start < day_end) do
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formatted_hour = hour_start.strftime("%F %H")
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result.merge!({ formatted_hour => price_at(formatted_hour)})
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hour_start = hour_start.advance(:hours => 1)
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end
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result
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end
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def high_low_hours(date)
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sorted_prices = prices_at(date).to_a.sort_by(&:last) # sort according to price
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highest_hour = sorted_prices.last[0]
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# Some months: do not charge; every hour that has cost > 0 is a high_hour
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if @no_grid_charge_months.include?(date.month)
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lowest_hour = "" # effectively no charging from grid
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high_hours = sorted_prices.select{|p| p[1] > 0}.to_h.keys
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else
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lowest_hour = sorted_prices.first[0]
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# calculate hours where rate > charge_rate + storage_cost (typically 0.05)
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charge_rate = sorted_prices.first[1] # assume we charge at lowest hour
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high_hours = sorted_prices.select{|p| p[1] > charge_rate + storage_cost}.to_h.keys
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# reset lowest_hour (effectively not charging), when price difference smaller than storage_cost
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highest_price = sorted_prices.last[1]
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lowest_hour = "" if (highest_price-charge_rate) < storage_cost
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end
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return lowest_hour,highest_hour,high_hours
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end
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def query_day_ahead_prices(date)
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start_date = date.beginning_of_day
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end_date = date.end_of_day.advance(hours: -1)
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# A44 - Document type => Price Document
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# NL = '10YNL----------L'
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domain = '10YNL----------L'
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url = URL + "/api?securityToken=%s&documentType=A44&in_Domain=%s&out_Domain=%s&periodStart=%s&periodEnd=%s" % [@api_key, domain, domain, start_date.strftime("%Y%m%d%H%M"), end_date.strftime("%Y%m%d%H00")]
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#p url
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base_request(date, url)
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end
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private
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def hourly_format(prices)
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# in memory hash @kwh_prices is in @zone timezone
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prices.to_a.map{|p| [p[0].in_time_zone(zone).strftime("%F %H"),p[1]]}.to_h
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end
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# get position and amount from XML snippet
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# <Point>
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# <position>1</position>
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# <price.amount>196.23</price.amount>
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# </Point>
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#
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# convert price to EUR per kwh, excluding VAT
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#
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def parse_point(xml)
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return xml.xpath(".//xmlns:position").text.to_i, (xml.xpath(".//xmlns:price.amount").text.to_f/1000).round(5)
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end
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def base_request(date, url)
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formatted_date = date.strftime("%F")
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doc = Nokogiri::XML(URI.open(url))
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prices = doc.xpath('.//xmlns:Point').map{|p| parse_point(p)}
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# get start_time (in UTC) from XML docment
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start_time = DateTime.parse(doc.xpath('.//xmlns:period.timeInterval//xmlns:start').text)
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#returns a hash with keys formatted "yyyy-mm-dd hr" and values price (per kwh)
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# <position> tag runs from 1-24. We need hours from 00-23, therefore substracting 1
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prices.map{|p| [start_time.advance(hours: (p[0]-1)), p[1]]}.to_h
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end
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end
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