Not only does orientation and angle to the sun greatly effect a solar PV array’s power output potential, but temperature does as well. For every 1°C rise in PV panel temperature, there is a 0.3% – 0.5% drop in PV efficiency. Extended periods of heat build-up can also damage the PV cells, shortening their useful life.
As any good solar installer already knows, solar PV arrays should always be installed with proper orientation and alignment to the sun; when possible. Systems installed in this manner don’t have to worry about heat build up as they already have sufficient airflow around the panels keeping them as cool as possible. But sometimes, whether for aesthetic or regulatory reasons, PV systems end up installed virtually flush against a vertical building facade or horizontal on a roof surface. Either scenario being bad for both the array’s overall power output potential and its lifespan.
By keeping air circulating evenly around a solar panel’s PV cells, a lot of the heat can be dispersed and/or reused, bringing the combined PV/T efficiency to 50% or more. That’s the idea behind Conserval Engineering’s SolarWall panels which can either be installed as a standalone passive solar air heating system or used in conjunction with a PV array to provide passive cooling to the panels while using panel heat to supplement interior air conditioning.
From SolarWall’s website:
A photovoltaic thermal system, also known as a “total energy system” converts sunlight into electricity, collects the residual heat energy and delivers both heat and electricity in usable form. The concept of marrying PV cells with a SolarWall heater creates a PV/T system that can boost the overall efficiency of the combined system by three fold of more while reducing the return on investment (ROI) of the entire system itself.
SolarWall PV panels get placed over regular SolarWall collector panels and put on the roof or wall, just like any other PV installation. Each M2 of SolarWall has thousands of small perforations which allows fresh air to pass through, balancing the air flow behind each PV module, and cooling them in the process.
In the winter months, the excess heat from the PV modules is drawn through the collector into a space between the building and the SolarWall heater. This excess solar PV heat, which would normally be wasted, is instead used to warm the ventilation air be fore it enters the building’s heating and ventilation system, providing a reliable source of fresh, but pre-heated make up air. In warmer weather, although fresh air continues to cool the PV modules, special dampers ensure that only fresh ambient (not pre-heated) air gets into the HVAC system.
The SolarWall system can be used for a multitude of applications including commercial, residential, institutional, military and even agricultural applications where excess heat can be used to dry certain types of harvested crops.
The Good: A system that can passively supply supplemental heated air for interior spaces and act as a heat sink for solar PV installations; thereby increasing their efficiency. Doesn’t require water or liquids to function.
The Bad: Most PV array installations do not need such a system for cooling given the fact that there is already sufficient air flow around installations that are not set flush against a surface i.e.roof, facade, etc. Vertical applications are not able to fully harness the suns heat and sunlight for optimal heat/power generation. Only practical in colder climates.
The Bottom-Line: A simple and fairly effective system for buildings located in colder climates and that have aesthetic restrictions on their solar PV systems.
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