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PV forecast: build the 10%/90% band on the P50 it is returned with, and use the Open-Meteo ensemble spread #5347

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Merged
springfall2008 merged 2 commits into from
Oct 2, 2026
Merged

PV forecast: build the 10%/90% band on the P50 it is returned with, and use the Open-Meteo ensemble spread #5347

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cc6f580
fix(solar): build the PV10/PV90 band on the P50 it is returned with, …
Oct 2, 2026
a2960a0
fix(solar): use a true median for the Open-Meteo ensemble ratios
Oct 2, 2026
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28 changes: 18 additions & 10 deletions apps/predbat/solar_model.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@

# Applied when no ensemble P10 data is available
_DEFAULT_P10_FALLBACK = 0.7
_DEFAULT_P90_FALLBACK = 1.3


def pvwatts_cell_temperature(poa_global, temp_air, wind_speed):
Expand Down Expand Up @@ -68,7 +69,7 @@ def _temperature_efficiency(gti, temp, wind):
return max(0.5, min(1.1, 1.0 - _TEMP_COEFF * (t_cell - _STC_TEMP_C)))


def gti_hourly_to_period_kwh(times, gti_values, temp_values, wind_values, kwp, system_loss, shading_factors=None, p10_instant=None, p10_fallback=_DEFAULT_P10_FALLBACK):
def gti_hourly_to_period_kwh(times, gti_values, temp_values, wind_values, kwp, system_loss, shading_factors=None, band_ratio=None, p10_fallback=_DEFAULT_P10_FALLBACK, p90_fallback=_DEFAULT_P90_FALLBACK):
"""Convert hourly GTI samples into per-hour PV energy for a single array.

Open-Meteo returns point-in-time irradiance (W/m2) at the start of each hour, so the
Expand All @@ -83,11 +84,13 @@ def gti_hourly_to_period_kwh(times, gti_values, temp_values, wind_values, kwp, s
kwp: array peak power in kW
system_loss: fractional system loss, e.g. 0.05 for 95% efficiency
shading_factors: optional list of 12 per-month multipliers
p10_instant: optional dict of timestamp string to raw P10 kW, before temperature derate
p10_fallback: multiplier applied to P50 when p10_instant has no entry
band_ratio: optional dict of timestamp string to (p10_ratio, p90_ratio), each relative to P50
p10_fallback: multiplier applied to P50 when band_ratio has no entry
p90_fallback: multiplier applied to P50 when band_ratio is given but has no entry

Returns:
dict of tz-aware UTC hour-start datetime to {"pv_estimate": kWh, "pv_estimate10": kWh}
dict of tz-aware UTC hour-start datetime to {"pv_estimate": kWh, "pv_estimate10": kWh},
plus "pv_estimate90": kWh when band_ratio is given
"""
instant_kw = {}
instant_stamps = []
Expand All @@ -102,15 +105,16 @@ def gti_hourly_to_period_kwh(times, gti_values, temp_values, wind_values, kwp, s
wind = wind_values[idx] if idx < len(wind_values) and wind_values[idx] is not None else _DEFAULT_WIND_MS
eta_temp = _temperature_efficiency(gti, temp, wind)
pv50_inst = dp4((gti / 1000.0) * kwp * eta_temp * (1.0 - system_loss))
raw_p10 = p10_instant.get(ts) if p10_instant else None
# p10_instant was computed without temperature derating; apply eta_temp now
pv10_inst = dp4(min(raw_p10 * eta_temp, pv50_inst) if raw_p10 is not None else pv50_inst * p10_fallback)
# The ratios scale the already derated P50, held to the side of it they belong on
p10_ratio, p90_ratio = band_ratio.get(ts, (p10_fallback, p90_fallback)) if band_ratio else (p10_fallback, p90_fallback)
pv10_inst = dp4(pv50_inst * min(max(p10_ratio, 0.0), 1.0))
pv90_inst = dp4(pv50_inst * max(p90_ratio, 1.0))
try:
stamp = datetime.strptime(ts, "%Y-%m-%dT%H:%M")
stamp = stamp.replace(tzinfo=pytz.utc)
except (ValueError, TypeError):
continue
instant_kw[stamp] = (pv50_inst, pv10_inst)
instant_kw[stamp] = (pv50_inst, pv10_inst, pv90_inst)
instant_stamps.append(stamp)

period_data = {}
Expand All @@ -119,16 +123,20 @@ def gti_hourly_to_period_kwh(times, gti_values, temp_values, wind_values, kwp, s
next_stamp = instant_stamps[i + 1]
if (next_stamp - stamp) != timedelta(hours=1):
continue
pv50_start, pv10_start = instant_kw[stamp]
pv50_end, pv10_end = instant_kw[next_stamp]
pv50_start, pv10_start, pv90_start = instant_kw[stamp]
pv50_end, pv10_end, pv90_end = instant_kw[next_stamp]
pv50 = dp4(0.5 * (pv50_start + pv50_end))
pv10 = dp4(0.5 * (pv10_start + pv10_end))
pv90 = dp4(0.5 * (pv90_start + pv90_end))

if shading_factors and len(shading_factors) == 12:
shading_month = shading_factors[stamp.month - 1]
pv50 = dp4(pv50 * shading_month)
pv10 = dp4(pv10 * shading_month)
pv90 = dp4(pv90 * shading_month)

period_data[stamp] = {"pv_estimate": pv50, "pv_estimate10": pv10}
if band_ratio is not None:
period_data[stamp]["pv_estimate90"] = pv90

return period_data
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