I-SEM Daily Briefing — 27 May 2026

Price Profile #

Std dev €28.7/MWh · Median €128.74/MWh · Periods above €150: 15 of 48 (31%)

The wind drought of May 25–26 broke — partially — and the day produced the second-highest morning peak of the entire series at €227.22 at 07:30. Only May 18’s €255 was higher.

Periods 1–2 (€196, €164 at 23:00–23:30 with wind at 42–44%) are Tuesday May 26’s evening peak spilling into Wednesday’s file — the familiar SEM day boundary artifact. The “real” Wednesday begins at 00:00 with €154 and falls cleanly into the overnight floor: €124–141 from 01:00 to 06:30, wind holding 26–34%.

The morning ramp is the structural feature. €141 at 06:00 → €227 at 07:30: +€86 in 90 minutes — the steepest ramp of the run. Three consecutive periods cleared above €200 (07:00–08:00). By 10:00 the morning peak had collapsed to €133. Midday belly held €113–117 from 12:30 to 15:30 (with the floor at €113.56 at 15:30), and the evening built a contained second peak — €114 at 16:00 → €154 at 20:00 — holding €151–154 across 19:00 to 21:00 before fading.

15 of 48 periods cleared above €150; 3 above €200 (all in the morning).

Price vs Wind #

Mean wind: 32.3% · Range: 19.3%–46.5%

A V-into-morning-peak wind shape. Wind started at 42–44% overnight (the Tuesday spillover) and dropped sharply into the morning ramp: 30% at 06:00, 27% at 06:30, 24% at 07:00, 21% at 08:00, 19% at 08:30 — the day’s minimum, sitting right inside the morning peak window. By midday wind had recovered to 30–35%, and held 36–46% through the evening.

This is the inverse of May 28’s wind shape (where wind held high through the evening and dropped only modestly through the morning). May 27 had a sharp morning shortfall and a steady evening — the optimiser will pick morning discharge for the third time in three days.

The mean wind today (32%) is higher than May 26’s 6.6%, but the morning peak (€227) is higher than May 26’s morning peak (€212). This is the wind-shape lesson reinforced: a higher mean with a sharper shortfall produces a higher peak. Mean wind is a poor predictor of peak price. The half-hour with the lowest wind during high demand is what matters.

Week in Context #

The morning-discharge pattern is now established. May 26, 27, and 28 will all be morning-discharge days. Combined with May 5 and May 18, that’s 5 of 24 days in the series where the morning peak outpriced the evening peak — and all 5 share the same wind signature: low wind in the morning peak demand window.

Price Duration Curve #

Periods above €150: 15 (31% of day) · Above €200: 3 (6% of day)

The curve has a sharp top spike (3 periods €203–227 — the morning cluster) followed by a smooth gentle slope through the upper-mid range and a moderate cheap tail. The visual signature: most of the day clears in the €115–155 band, with a sharp 3-period excursion at the top.

This is the “morning-spike” archetype — distinct from May 6’s twin-peak PDC or May 18’s broad scarcity plateau. The morning spike is short, sharp, and the rest of the day is unremarkable. A BESS that captures those three periods does well; everything else is filler.

Price Spread #

Captured spread: €98/MWh · Charge: €114/MWh (14:30) · Discharge: €213/MWh (07:00)

BESS Dispatch Signal #

Simulated 1MW/2MWh battery, one optimal DAM cycle. Gross before network charges and capacity costs.

€133 gross — tied with May 23 as the run’s seventh-best day. Third consecutive morning-discharge day.

The optimiser’s choice was clean. Morning block (07:00–08:30 at €212.65 avg) beats evening block (19:00–20:30 at €153.12 avg) by €60/MWh on the discharge side. Charge sits in the deep midday trough (13:30–15:00 at €114 avg). Captured spread €98, ROI 58.1% on the €229 charge cost.

The 24-day BESS series moves to €2,459 cumulative, mean €102/day. Top 5 days (May 18, 24, 17, 15, 27/23) sum to €781 — 32% of cumulative from 21% of days. Morning-discharge days are now over-represented in the top tier — May 18, May 27 alone are 2 of the top 5.

Commentary #

The wind drought broke, but only halfway. Mean wind 32% (up from May 26’s 6.6%) — but the timing of the wind was punishing: from 42% in the Tuesday spillover, dropping to 19% by 08:30 inside the morning peak demand window. The merit order climbed into peakers and produced the second-highest morning peak of the series at €227.22, with 3 periods clearing above €200.

The structural read is now obvious from repetition: for the third consecutive day, the morning peak outpriced the evening peak. May 26 (6.6% mean wind, €212 morning), May 27 (32% mean wind, €227 morning), May 28 (preview: 39% mean wind, €175 morning). The common signature isn’t mean wind level — it’s the wind decline rate going into the morning demand surge. When overnight wind ≥30% drops to ≤25% by 07:30, the morning peak wins. When it doesn’t, the evening peak wins.

For storage, €133 gross — third morning-discharge day in a row. The 24-day cumulative sits at €2,459, mean €102/day. The top 5 BESS days now include two morning-discharge events (May 18, May 27), supporting a structural hypothesis worth flagging: the morning shortfall produces higher peaks than the evening shortfall, on equivalent wind conditions. Why? Because the morning peak demand is climbing into the wind shortfall; the evening demand is more often flat or declining. Demand acceleration into a wind shortfall is the recipe for the highest single-period prints.