Heating of Spaces : Calento SLG

Calento SLG : Solar Air Heating of Spaces

The Calento SLG solar air collector was designed to provide warm air to the space even under the harshest Canadian climate. On cold, sunny winter days, the collector delivers warm, free solar-heated air into the building or process, thereby saving on gas or electricity, year after year.

How the Solar Collector Works

General Function in Recirculation
Function with outside air
Function with Additional Heating Source

Technical Data

Technical Sheet

Calento SLGSI Units [IP Units]
Technical Data
Solar air collector typeFlat-plate glazed, closed loop
Working fluidAir only
Main use and purposeSpace air heating
Peak solar efficiency, rated65 %
Maximum power output650 W/m2 [206 BTU/hr per ft2]
Maximal air throughflow per collector surface90 m3/h per m2 [5 cfm/ft2]
Pressure drop @ maximum throughflow400 Pa [1.6 in H2O]
Maximum temperature rise above ambient60 °C [108 °F]
Absorber panel
Panel materialAluminum alloy 99.8, Temper H18
Absorber thickness0.7 mm [0.028 in]
Available colors, selectiveblue, black
Absorbtivity in thermal spectrum95 %
Emissivity in thermal spectrum<3 %
Polycarbonate cover
Thickness40 mm [1.6 in]
Panel width500 mm [20 in]
Panel lengthnot limited
Panel structure7 walls, 6 cavities
Thermal resistance1.1 W/m2/°C [0.19 BTU/h/ft2/°F]
Light transmissivity65%
Standard colorclear
Mounted collector system, on site
Overall collector depth10 – 30 mm [4 – 12 in]
Weight per surface area, including framing5 kg/m2 [10 lbs/ft2]
Internal mount structureZee’s and hats, 18 ga. steel
Outer framingextruded aluminum
Maintenance requirementnone
Freeze protectionunnecessary
Overheating protectionunnecessary
Ratings & certifications
Solar Rating Certification Corp. certificate no.SRCC 10002148
Solar Keymark certificate no.011-7S3114 L
Test laboratoryFraunhofer ISE, Germany

Performance of the Solar Collector

More details


The SLG is a closed-loop collector. The air is typically drawn in from the bottom, led through the panel to collect the sun’s heat and delivered into the building space at a higher temperature. Even on a sunny, but cold (-20°C) winter day, the Calento SLG still will deliver warm above the space setpoint.

For engineers: Trigo Énergies’s first design objective is to offer a collector that delivers useful solar-heated in on the coldest (often the sunniest) days of winter. To achieve that, the SLG is covered by a 7-wall polycarbonate with a lowest thermal transmittance of 1.1 W/m2K while boasting a very respectable light transmittance of 65%.

The result is that on cold, -20°C sunny days, the collector can still deliver warm solar air back into the building or process. In summer, air remains still in the collector, ready for the next call for heat. The Calento SLG can also be fitted with an outside air intake and be used as an outside air preheater.

For architects: The outside cover of the Calento SLG is made of vertical, multi-wall polycarbonate panels that interlock into each other. The entire wall area covered with the Calento SLG ends up being an even and smooth vertical surface, with a silky, slightly translucid look. The inside of the collector, including heat panels and framing, comes standard with a dark blue color, originating from the physical vapor deposition solar-coating process.

The polycarbonate panels are co-extruded with a protective film to safeguard them against exposure to ultra-violet radiation, extending their life and performance with natural ageing. Framing is designed to allow the thermal expansion and retraction.

Installation Video (audio in French)

Project Photos