Energy efficiency

Since the 1980s, manufacturers of HVAC equipment have been making an effort to make the systems they manufacture more efficient. This was originally driven by rising energy costs, and has more recently been driven by increased awareness of environmental issues. In the US, the EPA has also imposed tighter restrictions. There are several methods for making HVAC systems more efficient.

[edit]Heating energy

Water heating is more efficient for heating buildings and was the standard many years ago. Today forced air systems can double for air conditioning and are more popular.

Some benefits of forced air systems, which are now widely used in churches, schools and high-end residences, are

• Better air conditioning effects
• Energy savings of up to 15-20%
• Even conditioning.^{[citation needed]}

A drawback is the installation cost, which can be slightly higher than traditional HVAC systems'.

Energy efficiency can be improved even more in central heating systems by introducing zoned heating. This allows a more granular application of heat, similar to non-central heating systems. Zones are controlled by multiple thermostats. In water heating systems the thermostats control zone valves, and in forced air systems they control zone dampers inside the vents which selectively block the flow of air. In this case, the control system is very critical to maintaining a proper temperature.

[edit]Geothermal heat pump

Geothermal heat pumps are similar to ordinary heat pumps, but instead of using heat found in outside air, they rely on the stable, even heat of the earth to provide heating, air conditioning and, in most cases, hot water. The heat extracted through a geothermal heat pump can come from any source, despite the temperature. However, the warmer the source of heat, the more energy efficient it will be.^[10] From Montana's −70 °F (−57 °C) temperature to the highest temperature ever recorded in the U.S.—134 °F (56.7 °C)in Death Valley, California, in 1913—many parts of the country experience seasonal temperature extremes. A few feet below the earth's surface, however, the ground remains at a relatively constant temperature. Although the temperatures vary according to latitude, at 6 feet (1.83 m) underground, temperatures only range from 45 to 75 °F (7.2 to 23.9 °C).

While they may be more costly to install than regular heat pumps, they can produce markedly lower energy bills—30 to 40 percent lower, according to estimates from the U.S. Environmental Protection Agency.

[edit]Ventilation energy recovery

Energy recovery systems sometimes utilize heat recovery ventilation or energy recovery ventilation systems that employ heat exchangers or enthalpy wheels to recover sensible or latent heat from exhausted air. This is done by transfer of energy to the incoming outside fresh air.

[edit]Air conditioning energy

The performance of vapor compression refrigeration cycles is limited by thermodynamics. These air conditioning and heat pumpdevices move heat rather than convert it from one form to another, so thermal efficiencies do not appropriately describe the performance of these devices. The Coefficient-of-Performance (COP) measures performance, but this dimensionless measure has not been adopted, but rather the Energy Efficiency Ratio (EER). EER is the Energy Efficiency Ratio based on a 35 °C (95 °F) outdoor temperature. To more accurately describe the performance of air conditioning equipment over a typical cooling season a modified version of the EER is used, the Seasonal Energy Efficiency Ratio (SEER), or in Europe the ESEER. SEER ratings are based on seasonal temperature averages instead of a constant 35 °C outdoor temperature. The current industry minimum SEER rating is 13 SEER.

Engineers have pointed out some areas where efficiency of the existing hardware could be improved. For example, the fan blades used to move the air are usually stamped from sheet metal, an economical method of manufacture, but as a result they are not aerodynamically efficient. A well-designed blade could reduce electrical power required to move the air by a third.^[11]

http://en.wikipedia.org/wiki/HVAC