Winter Performance Update
The 2025-26 winter tested our prototype installation thoroughly. The coldest panel reading was -14.8 C on 21 January 2026, with outside air at -23.2 C. The panel can sit a few degrees above ambient at night if there is any residual radiation, or drop below ambient due to black-body radiation to a clear sky. The drainback system handled all of this without intervention. On cold nights, the collector stood empty and dry. No freeze risk whatsoever. On clear winter days, even with ambient temperatures well below zero, the system ran and contributed useful heat.
Data from the test rig
All figures drawn from the RS485 sensor logs on the test rig near Prague, from 18.5 m2 of collector aperture. Data runs from 1 December 2025 to 14 March 2026 (102 days).
| Month | kWh collected |
|---|---|
| December 2025 | 269 |
| January 2026 | 257 |
| February 2026 | 333 |
| March 2026 (to 14th) | 473 |
| Total | 1,332 |
The pump ran on 51 of the 102 days. The highest tank temperature reached was 56.2 C. That gives 72 kWh per m2 of collector over the winter period, with March already showing strong spring gains.