Radiant Heating & Geothermal

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Radiant Heating

In-wall radiant heating in a house under construction near Denver. | Photo courtesy of Warren Gretz, NREL.

In-wall radiant heating in a house under construction

Radiant heating systems supply heat directly to the floor or to panels in the wall or ceiling of a house. The systems depend largely on radiant heat transfer — the delivery of heat directly from the hot surface to the people and objects in the room via infrared radiation. Radiant heating is the effect you feel when you can feel the warmth of a hot stovetop element from across the room. When radiant heating is located in the floor, it is often called radiant floor heating or simply floor heating.

Radiant heating has a number of advantages. It is more efficient than baseboard heating and usually more efficient than forced-air heating because it eliminates duct losses. People with allergies often prefer radiant heat because it doesn’t distribute allergens like forced air systems can. Hydronic (liquid-based) systems use little electricity, a benefit for homes off the power grid or in areas with high electricity prices. Hydronic systems can use a wide variety of energy sources to heat the liquid, including standard gas- or oil-fired boilers, wood-fired boilers, solar water heaters, or a combination of these sources.

Despite its name, radiant floor heating depends heavily on convection, the natural circulation of heat within a room as air warmed by the floor rises. Radiant floor heating systems are significantly different from the radiant panels used in walls and ceilings. For this reason, the following sections discuss radiant floor heat and radiant panels separately.

Radiant Floor Heat

There are three types of radiant floor heat — radiant air floors (air is the heat-carrying medium), electric radiant floors, and hot water (hydronic) radiant floors. You can further categorize these types by installation. Those that make use of the large thermal mass of a concrete slab floor or lightweight concrete over a wooden subfloor are called “wet installations,” and those in which the installer “sandwiches” the radiant floor tubing between two layers of plywood or attaches the tubing under the finished floor or subfloor are called “dry installations.”

Geothermal Energy

Geothermal energy is right under our feet. The earth’s core is like an inner sun, heating the earth’s surface and warming the water and rocks beneath. This steaming water and rock can be used to generate heat and electricity. The uppermost six miles of the earth’s crust alone contains more energy than all the oil and gas reserves in the world. Geothermal resources are considered base load meaning they are available 24 hours a day, 365 days a year.

The United States leads the world in terms of installed geothermal electricity capacity and generation, with most of that power installed in California. While U.S. geothermal energy generation has remained relatively stable from 2000 to 2008, the past two years experienced more than 3 percent growth. The U.S. Department of Energy estimates that geothermal power plants can provide15,000 MWs of new capacity within the next decade.

How does it work?

The most common form of geothermal power plant, a flash steam plant, uses water at temperatures greater than 360°F (182°C) that is pumped under high pressure to electricity generation equipment at the surface.

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