Solar glass is the combination of solar and glass technologies. Glass windows coated with a low-emittance (low-E) coating block radiant heat transfer. This lowers the amount of heat that passes through a window. Depending on energy needs, different types of low-E coatings allow for high, moderate, or low solar gains. Solar glass is often used to lower energy costs.
Low-E coatings are nearly invisible, and made up of layers of metal or metallic oxide on a glass surface. The coating is transparent to visible light. In layered glazing, heat can be transferred between panes of glass, from warmer to cooler. Putting a low-E coated pane in the space between layers of glass helps block that heat. Window technologists in the past filled this gap with air or dry nitrogen.
Today, argon and krypton gas are used between panes, which has improved window performance. Both gases are nontoxic and nonreactive. Krypton is more expensive than argon, so some manufacturers combine the two gases to improve thermal performance at a reasonable cost. Double-glazed windows with an argon gas fill between panes of low-E-coated glass are called pyrolitic, or hard coated. This application is designed to reduce heat loss but allow sunlight in for warmth, or solar gain.
Solar glass with high solar gain is best suited to windows in cold climates. Low solar gain, or spectrally selective, low-E glazings are more beneficial for buildings and homes in warm climates. These products reduce heat loss in cold weather, yet also reduce heat gain in hot weather. Spectrally selective solar glass out-performs most tinted and reflective glazings. The level of visible light let in is high in proportion to the amount of heat reduction.
For climates that require both heating and cooling during different seasons, all levels of low-E coating can result in lower annual energy bills. Solar glass is practical for windows, doors, and skylights. Commercially, it is used for the top surfaces of thermal collectors and photovoltaic modules. The appearance of solar glass is colorless, but can be patterned for optimal solar energy transmission.
High-performance glass products are used across many industries. Recent advances in solar glass include laminated products that boost solar power. This concentrating solar power (CSP) reflectivity provides efficiency and durability.
Solar specialists are benefiting from advances in window technology. Communication between the two professions results in high-performance solar glass. The use of solar glass in architectural applications is key in today's energy-conscious economy.
