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The Cutting Edge of Cool

A Reader Asks The Green Guide:

I just joined your site hoping to get helpful information as I design a major remodel of my home. I googled environmentally friendly air conditioning and got back bits of info on a new system called Eco Chill made by Thermax. Upon looking further, it appears that this is only for industrial or large buildings. Upon reviewing the Green Guide, it was a review of the standard same old stuff, but nothing as cutting edge as eco chill. Would you please look into this and inform me of the cutting edge? Please also refer me to a manufacturer that I can contact.

Thank you very much,

Dr. Jeanette Ryan

The Green Guide Responds:

Vapor Absorption

The ECO-Chill cooler mentioned in your letter uses vapor absorption technology, developed over a century ago and superceded by compression technology (used in air conditioning or "AC") when electric power came into dominance. Now, this technology may be resurrected since it does not use CFCs and can run off heat produced by other appliances. According to Abdi Zaltash, a research scientist at Oak Ridge National Labortory, which had developed prototype vapor absorption systems, the only commercially available residential unit in the US, called a high-efficiency gas-fired absorption chiller, is produced by the Italian company Robur (www.robur.com, for American distributors call 812-424-1800 and ask for the sales manager, Rick Halbig). Unfortunatley, the Robur chiller has not been certified by EnergyStar. EnergyStar-certified machines are your best option when looking for reliable, energy efficient AC and we recommend you look for this label on any AC unit you purchase.

The primary difference between the vapor absorption and conventional AC is that AC systems use electricity to compress refrigerant vapors, where vapor absorption systems use heat created from a combustible fuel. Vapor absorption uses a solutions of water and either ammonia or lithium bromide, so no fluorocarbon refrigerants are used. However, vapor absorption cooling systems cannot use electricity and must run on fuel, which means operating them will add carbon dioxide in the atmosphere.

The widest use of this technology can be found in countries with greater access to fossil fuel than cheap electricity. For example, in Japan, Korea and China vapor absorption accounts for as much as 50% of the commercial cooling market, compared to 5% in the US. Vapor absorption is one of several thermally-activated technologies that make up a new generation of heating and cooling methods, but home applications are still under development. The DOE has set a goal to develop an Ammonia-Water Absorption Heat Pump home appliance that would run on natural gas, propane or exhaust heat from another appliance and cost $2,500. As of this year, the project is still under development. We update our information continuously and will keep our readers posted.

Choosing Cooling Systems

When choosing an environmentally friendly home cooling system, energy efficiency and ozone depletion are central concerns. Department of Energy regulations require manufacturers to increase the energy efficiency of air conditioners by 30% beginning 2006. Over the next several years we are sure to see a number of major innovations in home cooling technology. This puts consumers in awkward position of having more eco-friendly AC choices than ever before, with knowledge that over the next two years the situation will improve even more dramatically.

Energy Efficiency

An air conditioner's rating is based on how much heat (measured in British Thermal Units (BTUs)) is removed per hour. Ratings are also based on tons. One ton equals 12,000 BTUs per hour.

A room air conditioner's Energy-Efficiency Ratio (EER) tells you the BTUs removed per hour for each watt of energy used. A central air conditioner's efficiency is measured the same way, but is referred to as the Seasonal Energy-Efficiency Ratio (SEER).

Today the minimal SEER is 9.7 for single-package systems and 10 for split systems. The 2006 standards for both are 13.

According to Energy Star, cooling accounts for nearly half the energy used by the average home during the summer.

Ozone Depletion

Conventional refrigerants are carbofluorocarbons (CFCs) that deplete the ozone layer. Today there are a number of less-harmful-CFC and non-carbofluorocarbon refrigerants.

Cooling Options

The most efficient and environmentally friendly option is to not use AC. There are a number of low impact strategies for keeping your house cool. Since the discomfort of a hot day is often the result of the house absorbing heat, keep the heat out and keep the house ventilated.

No AC

• Fans use 90% less electricity than AC.

• Shades help keep heat out of the house: keep them closed during the day and open at night.

• A ventilated attic lowers the temperature in the house.

• Open windows allow for cross ventilation.

• Trees on the west side of the house can provide shade, cooling the structure.

Room AC

• Cooling units are more efficient when located in a shady area of the house.

• Cool only the space that needs cooling.

• Keep doors and windows closed.

• Close all duct vents.

Central AC

Central AC is generally more efficient than room AC, though the cost of installation is substantially more

• Reduce the cooling load on the AC while it is running:

—Keep the shades drawn on the east and west sides of the house.

—Don't run a dehumidifier.

—Don't run the dishwasher, clothes dryer or other heat producing appliances.

—Keep the cooled space sealed off from un-cooled space.

—Run bath and kitchen fans sparingly.

• Set thermostat at 78 degrees Fahrenheit or higher. According to the DOE, "Each degree setting below 78°F will increase your energy consumption by approximately 8%."

• Keep the indoor and outdoor coils clean.

• Check the refrigerant charge.

Efficient Central AC Models

Bryant Quantum Plus Air
The Quantum model 598b has a rating of up to 16.5 SEER and uses the chlorine-free refrigerant Puron (the tradename for R-410A). Though R-410A is non-ozone depleting, it remains a significant greenhouse gas, according to Buildng Green.

Carrier WeatherMaker
The WeatherMaker line have SEER ratings up to 18.0 and uses the chlorine-free refrigerant Puron.

Elite Series
The Elite series two-speed model has a SEER of 19.2 SEER and uses chlorine-free refrigerant Puron.

Trane XL19i
Trane's 2.5-ton XL19i achieves a SEER rating of up to 19.5 when coupled with an optional air-handler. The XL19i uses the older R-22 refrigerant, which will be no longer be produced as of 2010. The manufacturer's limited warranty covers compressor, coil, and internal functional parts for 10 years.

Evaporative Coolers

If you live in a hot, dry climate the evaporative cooler or the "swamp cooler." is a smart alternative to AC. They cost 50% less (though installation is the same) and use approximately 75% less energy. They do require more maintenance and do not function well in humid climates. An evaporative cooler contains a fan and a water-wetted pad. The fan draws air from the outside through the wet pad, making it about 20 degree F. colder but more humid. Where an AC system cools the air inside and returns it to the house, the evaporative blows cold air into the house forcing the warmer outside through vents or open windows.

A recent development in EC technology is a two stage system that pre-cools air before it passes through the wet pad. Reportedly as effective as AC, the system also costs about the same as AC.

Geothermal

Perhaps the most efficient and environmentally friendly alternative to AC is a geothermal heat pump, which will heat in the winter and cool in the summer using 50% less energy than conventional furnace and AC systems. (See "Is Geothermal the Way to Go?")