Add demo solar forecast template (#21971)

Co-authored-by: Michael Geers <michael@geers.tv>

cmd/demo.yaml

@@ -262,6 +262,12 @@ tariffs:
   feedin:
     type: fixed
     price: 0.08 # EUR/kWh
+  solar:
+    type: template
+    template: demo-solar-forecast
+    kwp: 15.5
+    sunrise: 7
+    sunset: 17
   #co2:
   #  type: grünstromindex
   #  zip: 12349

templates/definition/tariff/demo-solar-forecast.yaml

@@ -0,0 +1,108 @@
+template: demo-solar-forecast
+products:
+  - description:
+      de: Demo PV Vorhersage
+      en: Demo PV Forecast
+requirements:
+  description:
+    de: Zu Demonstrationszwecken. Liefert optimale Solarproduktionskurve mit Spitze zur Mittagszeit.
+    en: For demonstration purposes. Provides optimal solar production curve peaking at noon.
+  evcc: ["skiptest"]
+group: solar
+params:
+  - name: kwp
+    type: float
+    unit: kWp
+    default: 4.5
+    description:
+      en: Maximum generator power
+      de: Maximale Generatorleistung
+  - name: sunrise
+    description:
+      de: Sonnenaufgang
+      en: Sunrise hour
+    type: int
+    unit: h
+    default: 6
+    help:
+      de: Stunde des Sonnenaufgangs (0-23)
+      en: Hour of sunrise (0-23)
+  - name: sunset
+    description:
+      de: Sonnenuntergang
+      en: Sunset hour
+    type: int
+    unit: h
+    default: 18
+    help:
+      de: Stunde des Sonnenuntergangs (0-23)
+      en: Hour of sunset (0-23)
+  - name: interval
+    default: 1h
+    advanced: true
+
+render: |
+  type: custom
+  tariff: solar
+  forecast:
+    source: js
+    script: |
+      // Generate realistic solar forecast with bell curve for next 72 hours
+      var now = new Date();
+      var start = new Date(now.getFullYear(), now.getMonth(), now.getDate(), 0, 0, 0);
+      var rates = [];
+      var peakPower = parseFloat({{ .kwp }});
+      var sunrise = parseInt({{ .sunrise }});
+      var sunset = parseInt({{ .sunset }});
+
+      // Calculate day parameters with inclusive hours
+      // Using modulo to handle midnight-spanning days elegantly
+      var dayLength = (sunset - sunrise + 1 + 24) % 24 || 24;
+
+      var is24HourDaylight = dayLength === 24;
+      var noon = (sunrise + dayLength / 2) % 24;
+
+      // Helper function to calculate position within daylight period
+      function getPositionInPeriod(hour) {
+        if (is24HourDaylight) {
+          // 24-hour daylight: distance from noon with wrap-around
+          var diff = Math.abs(hour - noon);
+          return Math.min(diff, 24 - diff);
+        } else {
+          // Regular day: hours from sunrise
+          return hour >= sunrise ? hour - sunrise : 24 - sunrise + hour;
+        }
+      }
+
+      // Generate hourly rates for 3 days
+      for (var day = 0; day < 3; day++) {
+        for (var hour = 0; hour < 24; hour++) {
+          var time = new Date(start.getTime() + (day * 24 + hour) * 3600000);
+          var solarValue = 0;
+
+          if (dayLength > 0) {
+            // Check if hour is within daylight period
+            var isDaylight = is24HourDaylight || (sunrise <= sunset
+              ? hour >= sunrise && hour <= sunset
+              : hour >= sunrise || hour <= sunset);
+
+            if (isDaylight) {
+              var position = getPositionInPeriod(hour);
+              var normalized = is24HourDaylight
+                ? position / 12
+                : (position - dayLength / 2) / (dayLength / 2);
+              var curve = 1 - normalized * normalized * (is24HourDaylight ? 0.89 : 1);
+              solarValue = peakPower * 1e3 * curve;
+            }
+          }
+
+          rates.push({
+            start: time.toISOString(),
+            end: new Date(time.getTime() + 3600000).toISOString(),
+            value: Math.round(Math.max(0, solarValue))
+          });
+        }
+      }
+
+      JSON.stringify(rates);
+  interval: {{ .interval }}