AmberPrices.sh

#! /bin/bash

# Get electricity price data from Amber, and usage/generation/grid power from a Fronius inverter (site), and report.
#
# (c) Copyright 2020 Clifford Heath.
# Code is known to be incorrect. Free for use at your own risk.

# Per Amber interim API documentation:
# All timestamps in the data are market time (ie Brisbane time) and at period end,
# not start (so if it's 915am, the current period is the 930am one).
# These prices are GST inclusive, so divide by 1.1 if you need them exclusive.
# Usage:
# data.staticPrices.E1.totalfixedKWHPrice + data.staticPrices.E1.lossFactor * data.variablePricesAndRenewables.[period].wholesaleKWHPrice
# And the formula for Export to Grid prices is:
# data.staticPrices.B1.totalfixedKWHPrice - data.staticPrices.B1.lossFactor * data.variablePricesAndRenewables.[period].wholesaleKWHPrice
# Some aspects of the above formulae are uncertain. I'm checking the details with Amber.
#

# Fetch current pricing data from Amber. Substitute your postcode here.
amber_prices=`cat <<COMMAND
	curl -s -X POST https://api.amberelectric.com.au/prices/listprices -H 'Content-Type: application/json' -d '{ "postcode": "2087" }' || echo "{}"
COMMAND
`

# Fetch power flow data from a Fronius inverter. Substitute the DNS name or IP address of your inverter:
inverter=inverter
power_flow=`cat <<COMMAND
	curl -s 'http://$inverter/solar_api/v1/GetPowerFlowRealtimeData.fcgi' || echo '{}'
COMMAND
`

node <<JAVASCRIPT
	// Get price data from Amber:
	var prices = `eval $amber_prices`;
	if (prices === undefined			// Some sanity checking
	 || prices['data'] === undefined
	 || prices.data['staticPrices'] === undefined
	 || prices.data['variablePricesAndRenewables'] === undefined)
	{
		console.log("Failed to fetch price data");
		process.exit(1);
	}

	// Extract the main structures:
	var staticPrices = prices.data.staticPrices;
	var variablePricesAndRenewables = prices.data.variablePricesAndRenewables;

	// Find the variable price data for the current period:
	var now = new Date();	// NOT IMPLEMENTED: Fetch current market time, i.e. Brisbane time (no DST)
	var currentVariableDataIndex = variablePricesAndRenewables.findIndex(
			variablePricesAndRenewable => {
				// the period here is the END of the current half-hour
				var period = Date.parse(variablePricesAndRenewable.period);
				var is_current_period = (period-30*60*1000 <= now && period > now);
				return is_current_period;
			}
		);
	var	variablePricesAndRenewable = variablePricesAndRenewables[currentVariableDataIndex];

	var	totalfixedKWHPriceE1 = +staticPrices["E1"].totalfixedKWHPrice;
	var	totalfixedKWHPriceB1 = +staticPrices["B1"].totalfixedKWHPrice;	// Per JB, this isn't needed, it's a fudge
	var	wholesaleKWHPrice = +variablePricesAndRenewable.wholesaleKWHPrice;
	var	lossFactor = +staticPrices["E1"].lossFactor;	// The negative of this is copied into B1.
	var	period = new Date(Date.parse(variablePricesAndRenewable.period));

	// Check these two expressions with Amber:
	var	usage_rate = totalfixedKWHPriceE1 + lossFactor*wholesaleKWHPrice;
	var	export_rate = /* totalfixedKWHPriceB1 + */ lossFactor*wholesaleKWHPrice;

	// Report price data:
	var	period_representation = period.toLocaleTimeString();
	console.log("At " + now.toLocaleString() + " (time period ending " + period_representation + "):");
	console.log("\tGrid loss factor is " + Math.round((lossFactor-1)*1000)/10 + '%');
	console.log("\tTotal Fixed Price is " + Math.round(totalfixedKWHPriceE1*10)/10 + " c/kWhr");
	console.log("\tWholesale Price is " + Math.round(wholesaleKWHPrice*10)/10 + " c/kWhr");
	console.log("\tUsage costs " + Math.round(usage_rate*10)/10 + " c/kWhr");
	console.log("\tExport earns " + Math.round(export_rate*10)/10 + " c/kWhr");

	// Get generation&usagedata from the inverter:
	var power_flow = `eval $power_flow`;
	if (power_flow["Body"] === undefined)
	{
		console.log("Failed to fetch generation and usage data");
		process.exit(1);
	}
	var site_power = power_flow["Body"]["Data"]["Site"];
	var grid_power = +site_power["P_Grid"];		// +ve = import, -ve = export
	var load_power = +site_power["P_Load"];		// Usage
	var pv_power = +site_power["P_PV"];		// Generation

	console.log("\tUsing " + Math.round(-load_power) + "W, generating " + Math.round(pv_power) + "W");

	// Normalise the instantaneous usage rate to a daily cost in cents:
	var cents_per_day = (grid_power > 0 ? usage_rate : -export_rate) *grid_power*24/1000;
	console.log("Currently "
		+ (grid_power > 0 ? "buying " : "selling ")
		+ Math.round(Math.abs(grid_power)/100)/10 + "kW"
		+ " at $" + Math.round(cents_per_day)/100 + "/day"
	);
JAVASCRIPT