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You are here: Home KREC Tech at Work Solar Heat Pipe Demonstration

Solar Heat Pipe Demonstration

The unit is now installed on UofL's Shelby Campus.

The unit has 32 sensors installed to monitor temperature and track overall performance during the seasons.

The Solar Heat Pipe Wall - a KREC-supported research project - is now a reality at UofL's Shelby Campus. The heat pipe augmented solar wall was developed by M. Keith Sharp, Associate Professor of Mechanical Engineering, J.B. Speed School of Engineering at the University of Louisville.

Nicholas E. Chmielewski, a recent graduate of the J.B. Speed School of Engineering, built the full-scale prototype unit and helped install it in a classroom in Burhans Hall as part of his Master's thesis. The prototype was built to fit within an existing window frame, which helped keep installation cost to a minimum. As part of the design, Nick installed 32 sensors at various points within the unit to provide real time operating data under actual solar conditions. A pyranometer, a device to measure global and diffuse radiation and sunlight duration, will monitor daily solar activity and help determine the heating efficiency of the solar wall as the angle and duration of sunlight changes with each season.

The solar wall design employs five individual heating units each consisting of an absorber plate clamped to a heat pipe. The heat pipes are mounted in the frame at a five degree angle and consist of an evaporator, adiabatic (working fluid) and condenser section. The adiabatic section of the heat pipe was installed in a layer of thermal insulation and then placed within a water tank which acts as a thermal mass.

An aluminum frame supports the absorbers, heat pipes and water tanks and the five heating units are enclosed within an aluminum sheet metal skin with a glazing on the front of the unit. The rear of the unit consists of a screen on the heated face which allows the thermal mass to slowly give off heat to the space.

The main characteristics (advantages) of heat pipes are:

  • A "thermal diode effect" in which heat is only transferred in one direction, allowing conductivity in one direction and insulation in the other direction.
  • No moving parts, no maintenance and very long operating lifetimes (70+ years depending on working fluid).
  • Exceptionally high conductivity (100 times that of copper) due to latent heat transfer.
  • Passive system requiring no power input.

Nick sees tremendous potential in renewable energy and highlights some important points in his Master's thesis. "More solar energy strikes the earth's surface in an hour than the amount of energy consumed by the world population in a year. Just 0.15% of the surface area of the United States in solar panels would produce all of the nation's energy demand. Potential wind energy in the United States is also in excess of our current demands [National Renewable Energy Laboratory]. Other renewable energy sources also show promising volumes of yet untapped availability."

Nick believes that the involvement of KPPC and the fact that the prototype was installed in a UofL classroom will increase awareness of the technology. "Display of operational performance data with the unit as well as promotion of the research by UofL and KPPC will also help promote interest and increase market demand for the technology."



Sunlight is tracked with a pyranometer, an instrument for measuring global and diffuse radiation and sunlight duration.
Image of pyranometer.
With the help of installers, Nick Chmielewski prepares the unit for mounting in the prefabricated window frame.
Image of unit preparation by installers.



After careful alignment and some minor adjustments, the solar wall is fitted into its frame.
Image of solar wall in the frame.
The solar wall in place. Aluminum panels were used to frame the unit.
Image of unit framed with panels.
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