Questions and Answers
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How can a Sunplate® be more efficient than an unglazed plastic solar collector when the fluid inlet temperature and the ambient air temperature are the same? Won’t the Sunplate® lose more energy in the process of transferring heat from the cover plate to the absorber?
Your thermal performance simulation shows that both Sunplates® and glazed flat plate collectors produce more heat than evacuated tube collectors under most normal operating conditions. But evacuated tube manufacturers claim their collectors produce much higher efficiencies than glazed flat plate collectors. Who is correct?
- The U.S. utility and PCT international filings met the one year filing deadline for claiming priority to the U.S. provisional application because 12 and 13 April, 2013 were not business days for the receiving office.
- Mauthner, Franz and Weiss, Werner. “Solar Heat Worldwide: Markets and Contribution to the Energy Supply 2011” (2013 Edition). International Energy Agency Solar Heating & Cooling Programme. Tables 1 and 2, pp. 9–10.
- A specific example, Almeco Solar’s Tinoxenergy blue sputter PVD coatings, incorporate an anti-reflective, clear hardcoat layer of fused quartz that is extremely hard and scratch-resistant. The selective material is a multilayer cermet structure. A diffusion barrier is applied to an adhesive layer between the selective coating and the absorber to prevent metal atoms from entering the absorber layer at high temperatures and changing the optical properties. Tinoxenergy has a published absorptance of 0.95 and emissivity of just 0.04. “Tinoxenergy” is a trademark of Almeco GmbH.
- 3M® Ultra Barrier Solar Film is an exemplary transparent barrier material designed to replace glass in flexible thin film solar PV panels. The product has just 3% reflectance, and its moisture barrier performance and weatherability have been subjected to extensive field testing. 3M® is a trademark of 3M.
- A view factor technically refers to the percentage of infrared energy leaving an emitting surface that strikes an absorbing surface. As a practical matter, increasing the view factor can accomplished by increasing the surface area of the emitting surface; for example, by creating ridges on the emitting surface. The view factor of the cover plate interior surface is also increased by conductive transverse frames in direct contact with the opaque cover, assuming these secondary surfaces are coated for high emissivity.
- Evacuated tube collectors are not affected by wind. Glazed flat plate collectors do not experience any meaningful loss in performance at a 3 m/s wind speed. While instantaneous efficiencies can negatively distort the real world performance of solar collectors over an extended period of time, 50°C (122°F) is a temperature often used to show “apples-to-apples” comparisons of medium temperature performance.
- Assuming standard test conditions of 1,000 W/m2 solar irradiance and 25°C (77°F) ambient air temperature.
- In reality, the “other 82–85%” of the incoming solar energy is only 70% or so, after taking into account the reflectance and infrared emissivity of the PV panels.