Heated glass towel warmers can outperform radiator-type warmers while increasing the aesthetic appeal.

An emerging technology promises to significantly increase design options for radiant heating applications where aesthetic attributes are important. This technology, which involves electrically heating a glass surface, has numerous advantages over traditional heating coils, gas flames, and radiator-style heating devices.

A pane of glass can be electrically heated when a transparent thin film conductor is applied to the glass. Coupled with interconnects and an electronic control circuit that regulates power, this technology radiates heat uniformly across the entire glass surface with precise temperature control.

Because this is an emerging science, only a handful of practical applications have been commercialized to date, but a number of application developments are underway for appliances, foodservice equipment, and the hospitality industry.

Engineered Glass Products is the first U.S. company to use transparent thin film conductors to create heated glass designs and products. While other methods may heat glass along strips of visible wiring, like those seen automotive rear window defrosters, this approach is intrusive upon the appearance of the glass. By contrast, the EGP technology is invisible, leaving the glass completely transparent and indistinguishable from ordinary unheated glass.

In this comparative test of a warming drawer application, infrared analysis shows that the version using heated glass provides a more uniform heat distribution (top) than a traditional heating element (below).

The advantages of a thin film conductor go far beyond the visual appeal it has over previous glass-heating methods. The new method is well-suited for food preparation and storage applications that have been largely dominated by heating coils and gas flames.

Heating coils are inefficient, and they provide heat only along narrow bands. Uneven heating leads to warm and cool spots throughout the object or area to be heated. Furthermore, the heat radiates off the coils in all directions, which can lead to a significant amount of wasted energy. Also, these coils are aesthetically unappealing if exposed. Therefore, they are generally covered up with extra material, which in turn adds size, weight, and cost to the heating apparatus.

Gas flames have similar drawbacks in terms of uneven heating since most heat is directed immediately above the flame. They also diminish temperature control. The minimum temperature of the flame is high, and the gas supply is often regulated by guesswork on the part of the user rather than precision measurements. Also, open flames present some obvious safety hazards.

Electrically heated glass maintains a steady and consistent temperature across the entire surface, and heat radiates off the glass in only one direction: toward the object or area to be heated. In addition, the technology provides the beauty and elegance of glass. The glass can also be colored or etched with designs in order to complement the appearance of a room or appliance.

Viking Range has introduced the this technology in the heated glass high shelf on its 36-in. -W Designer Series range (model D36HS24). The glass serves as an attractive, transparent shelf for reheating food or keeping it warm until served. The smooth glass surface is sanitary and easy to clean. The heat radiates evenly throughout the entire shelf so that the food — no matter what its size or shape — is never too close or too far from the heating element, as can happen with coil technology or gas flames. The heated glass elements used by Viking were designed by EGP and are marketed under the name Thermique Hot Glass Technology.

Similar applications are being developed for stores and restaurants. Heated glass is both visually attractive and sanitary, making it ideal for use with food in a public setting. For example, Hatco Corp., has designed a heated deli cabinet using electrically heated glass. Since the glass is perfectly transparent, deli items are in full view of the customers, but they remain hot and ready to serve. Keeping meat and other food items warm improves the taste while preventing spoilage. The technology is much more efficient and effective than heat lamps, and it is a definite improvement over microwaving cold items just before they are served.

The Thermique components that are now being incorporated into Viking and Hatco products are UL recognized and meet all Safety Glazing Code requirements. These components — the thin film conductor, bus bars, and interconnects — are applied to one surface of the glass during fabrication. The process leaves a 12 mm perimeter around the edge of the glass so it can be installed into ordinary framing materials.

An electronic controller regulates power flow to the heating components, and thus controls glass temperature. With a simple twist of the dial, the glass can assume any temperature from approximately 70 DegF to 350 DegF. An important feature of the controller is its automatic fault and glass breakage detection capability that will automatically shut down the heating circuit if there is a problem. In addition, the appliance should include a GFCI breaker to guard against ground faults and leakage currents.

The controller provides instantaneous response and very accurate control, even at very low power levels, which is critical particularly in food preparation and storage. In such environments, heated glass can also be used for warming plates, utensils, and other items.

Heated glass shelves, as in this Hatco deli cabinet, keeps displayed food products warm while improving visibility of the merchandise.

Electrically heated glass has a number of potential applications beyond appliances and foodservice equipment. For example, the material can also be employed in the design of towel warmers for both custom homes and hotels, replacing traditional radiator style units. The invisible thin film conductor involved in this design is even more efficient than traditional radiator-type towel warmers. These stylish towel warmers are comprised almost entirely of glass, yet the glass used in these applications is never too hot to touch, and it does not contribute noticeable amounts of heat to the room.

Electrically heated glass can also be incorporated into a double-pane Low-E architectural window unit. With the heating element applied only to the interior side, the window will radiate warmth into the room no matter what the temperature outside. This eliminates the heat loss, chills, drafts, and frost problems associated with ordinary glass in cold climates. In warm weather, heated glass prevents condensation, which helps prevent mold from growing on the window seal. Busick Insulated Glass, Denver, Colo., is the first distributor to integrate Thermique technology into its IG window product line.

As more product designers become aware of electrically heated glass, even more applications should arise that incorporate it.