Nocturnal Solar Cooling Energy Invention

BUFFALO, N.Y. - Oct. 23, 2015 - PRLog -- Solar cooling a building at night? At first this idea seems an inherent contradiction of conventional science. But have you ever enjoyed an evening outdoors on a deck watching the sun set and felt the air get cooler? It is not the air temperature that changed. What you are feeling is your body radiating heat to the night sky at a rate of 75 watts/m². This cooling effect applies to the entire surface of the earth as it loses heat to the cold sky. During the day, the incoming radiation from the sun is 10 times greater, which offsets the heat loss. But from sunset to sunrise, the radiation heat loss is one way – from earth to the sky.

John Hollick, P.Eng., of Conserval Engineering, with offices in Buffalo NY and Toronto Canada, has developed a nocturnal solar cooling system that can be attached to buildings and takes advantage of the radiant cooling effect as a renewable energy cooling source.

Hollick is the inventor of the SolarWall transpired collector, which was a landmark invention in solar air heating that has been used on thousands of buildings around the world since the 1990s. The recently patented “NightSolar” unit incorporates the same solar collector as a SolarWall system but in a reverse way. It removes thermal energy from the air to cool a building without the use of compressors or refrigeration systems. As the roof cools by as much as 10°C (18°F) below ambient, it can cool air passing through it by as much as 5°C (9°F). This cooling has the ability to reduce or even displace conventional air conditioning from sunset to sunrise.

As warm night air touches the cooler surface of the NightSolar transpired collector, outside air transfers its heat to the metal surface, which cools the air. The chilled air is then drawn in through perforations in the collector and enters the HVAC unit via an economizer cycle.

From a structural perspective, the NightSolar system consists of a single sheet of corrugated metal mounted 4 to 8 inches above an existing roof and it has the same appearance as a SolarWall system or a conventional metal roof.

The system works day and night in the summer, with the daytime solar heat collected in the same way as a conventional SolarWall system. During the daytime, the NightSolar system keeps the roof shaded and in the dark, and thereby reduces daytime heat gains and the solar heat can either be dissipated or used to heat water or industrial processes.

The technology is commercially available and recent field monitored installations are reporting impressive cooling savings on buildings using existing fans and economizers. Test systems at the National Solar Test Facility have confirmed the ability to cool air below ambient in accordance with ASHRAE Handbook. A demonstration project on telecom shelters in Turkey showed cooling savings of up to 50% and plans are underway to expand that project. Closer to home, the U.S. military has also installed pilot projects which are to be monitored.

In 2014 the SolarWall and John Hollick, were honoured by American Society of Mechanical Engineers (ASME) in New York City in a new exhibit as one of 80 of the best inventions, inventors and engineering feats of the past two centuries along with Thomas Edison, Henry Ford, Willis Carrier, George Westinghouse and the Panama Canal.

Hollick is not resting on his laurels as he has recently filed additional patents which use solar heat from his panels to drive solar chimney towers and produce electricity.