CLEAN AIR AND THE RECOUPAERATOR

Transcription

1 A STIRLING TECHNOLOGY WHITE PAPER CLEAN AIR AND THE RECOUPAERATOR PROBLEM OVERALL AIR QUALITY EFFECTS According to the U.S. Environmental Protection Agency (EPA), indoor air, on average, has a pollution concentration two to five times higher than the air outside. Some instances have found this number to be almost 100 times the levels found outside. 1 Chemicals, dust, pollen, mold, smoke, and radon gas are among the most common indoor pollutants, but computers, home electronics, and gas appliances can also contribute greatly to this problem. 2 Pollutants have a significant impact on people s health; lung tissue in particular is easily damaged by impurities in the air. Poor air quality can affect the lungs and cause or contribute to respiratory ailments such as asthma, allergies, chronic bronchitis, lung cancer and respiratory infections. In addition, it can cause headaches, dry eyes, nasal congestion, nausea, fatigue, and a general decline in overall health. These aliments are a large contributor to the increasing number of absences from school and work. 3 CAUSES The Canadian Lung Association explains that two of the most common ailments, allergies and asthma, revolve around airborne stimuli. Inhaling substances such as mold, smoke, and pet dander, is one of the primary causes of allergic reactions. Inhalant allergens and respiratory viral infections are the most important inducers of airway inflammation and asthma cases. An increase in the number of people experiencing allergy and asthma symptoms is very likely due to increased indoor and outdoor pollutants. The Lung Association goes on to explain that health effects may show up after years of exposure or prolonged periods of exposure. Some of these effects can be severely debilitating or fatal and can include respiratory diseases, heart disease, and cancer. It is prudent to try to improve the indoor air quality in your home even if symptoms are not noticeable. 4 Many common household items contribute to the extensive amounts of particulates in a house. These particulates are unobservable to the human eye, but are a major contributor to allergic reactions. In some causes these reactions may be severe. Chemical Vapors Chemical vapors are emitted from many common household items and new construction materials such as: carpet, furniture, paint, common cleaners, and adhesives. Dizziness, headaches, allergic reactions, and respiratory troubles are often associated with the inhalation of these vapors. Combustion Gases Malfunctioning or back-drafting furnaces or water heaters White Paper: Clean Air and the RecoupAerator, 1/27/04, , page 1

2 can emit carbon dioxide and carbon monoxide to the interior of the home. In addition, unvented gas ranges, dryers, space heaters can also expel harmful gases. The most common effects from these appliances are dizziness and headaches. If carbon monoxide levels increase to unsafe levels, carbon monoxide poisoning can occur and lead to severe illness or even death. Mold and Fungus Mold and fungus growth occurs in areas of the home where there is excessive moisture: around window frames, inside ductwork, and inside walls. Mold and fungus, especially Aspergillus, can cause severe respiratory illness and allergic reactions. Radon A naturally occurring radioactive gas that seeps into a home from the ground that surrounds it. In a super-tight home, radon can quickly build up to dangerous levels. Radon is a naturally occurring radioactive gas, which results from the radioactive decay of Uranium through its daughter, radium. Radon also decays by releasing an alpha particle continuing a chain of decays, eventually ending with the stable isotope of Lead. Since Radon is the only member of the decay sequence that is a gas and is therefore highly mobile, it has the potential to increase exposure of human lung tissue to radiation. The health significance of the Radon decay sequence to Lead is that it occurs in a very short period of time and can deposit potentially ionizing radiation in lung tissue. Average outdoor levels are generally 0.25 pci/1 and acceptable indoor levels are to be at or below 4 pci/1. 5 Radon poisoning can cause severe illness and premature death. Smoke Cigarette smoke is a dangerous health hazard. Smoke contains over 3,000 chemicals, at least 50 of which are known, identified carcinogens. Smoke also contains tar, nicotine, and carbon monoxide. Second-hand smoke inhalation causes increased risk of lung infections and lung diseases such as pneumonia, bronchitis, asthma, emphysema, and cancer, as well as ear infections, sinus problems, heart disease, strokes, nose, eye and throat irritation, nausea, dizziness, and headache. Smoke also stains clothing, furniture, and walls and creates an unpleasant smell that can linger for months and years. 6 Household and Pet Odors Cooking, cigarette smoke, pets, and laundry can all contribute to unwanted odors. While household odors are not necessarily dangerous, at high concentrations they can induce sensory and respiratory irritation. Irritation can occur when the odor is first detectable. The irritancy or toxicity increases when the concentration of the odor increases. Examples of irritating odors include ammonia, chlorine, and formaldehyde (e.g., from building products), as well as acrolein, acetaldehyde, and organic acids found in cigarettes.. 7 The RecoupAerator Solution The RecoupAerator system works by introducing fresh, filtered air into a building and removing the old air. These air cleaners eliminate stale air from bathrooms, kitchens, and laundry rooms and supply fresh air to bedrooms and high-use areas. The heat (or coolness) of the air being exhausted is transferred to the fresh air coming into the home so that indoor temperatures are maintained no matter how cold or hot the outside air is. Additionally, these energy-efficient systems also maintain humidity levels. The RecoupAerator can be incorporated into existing ductwork. RecoupAerators recover about 96 percent of the heat as well as about 30 to 40 percent of indoor moisture. Their patented rotary random matrix polymer White Paper: Clean Air and the RecoupAerator, 1/27/04, , page 2

3 captures the heat and transfers it to the incoming air stream. The product includes a patented rotary heat exchange core, filters, fans, and a drive motor. The RecoupAerator has an air flow capacity of 197 feet 3 /minute and a 96 percent sensible thermal efficiency rate at full flow. ENERGY RECOVERY VENTILATOR (ERV) PRODUCT DESCRIPTION 8 Occupied buildings rely on outdoor ventilation to keep the concentration of indoor-generated pollutants at a low level and to maintain acceptable indoor air quality. However, ventilation requires a higher energy cost required to condition (heat, cool, humidify and/or dehumidify) the entering outdoor air. Rotary periodic heat and mass exchangers, another name for energy recovery ventilators, are used to reduce air-conditioning costs in ventilated buildings by recovering energy from the exhaust air stream and transferring it to the supply air stream. Energy recovery ventilators transfer sensible heat as the hot air stream passes though the porous matrix, picking up and storing heat and releasing it as the wheel rotates in to the cold air stream. In winter the ventilator transfers heat and moisture from the exhaust (indoor) air stream to the supply air stream coming from outdoors. Outdoor air is warmed to closeto-room temperature with heat that would otherwise be lost with the exhaust air. The fresh incoming air is automatically preheated or precooled depending on the season. This dramatically reduces the energy costs of ventilation. HEAT EXCHANGER 9 The energy recovery ventilator consists of a blower and a rotating heat exchanger core that is exposed cyclically to hot and cold air stream. Air flows can be adjusted from 60 to 200 CFM or 100 to 340 CMH. The porous heat transfer media is in the shape of a wheel that rotates between two counter-flow air streams. The wheel contains a random fiber matrix, which serves as the heat exchanger core. As can be seen in Figure 1, warm air flows through the heat exchanger, then through the fibrous heat exchange matrix. The thermal energy for this air stream is transferred to the matrix during half of the revolution. During the next half revolution, the cold air flows through the same passages and picks up thermal energy. The ventilators are sealed to prevent leakage of air between the two flow streams. This design transfers heat from incoming and outgoing air streams, eliminating much of the need to heat or cool air coming into a house and decreasing utility bills. At 60 CFM (100 CMH) the RecoupAerator has a consumption rate of only 34 watts. A mere 200 watts are used at the full air flow of 200 CFM (340 CMH). White Paper: Clean Air and the RecoupAerator, 1/27/04, , page 3

4 Figure 1: Energy Wheel HEAT EXCHANGE MATERIAL The heat transfer through an ERV is enhanced to over 90 percent through the use of porous material as a heat exchange media. Stirling s energy recovery ventilators are capable of recovering up to 96 percent of the energy in the exhaust air from the house and transferring it to the supply air entering a house. The RecoupAerator has a washable heat exchange matrix with a washable expanded aluminum pre-filter. This MERV 8 filter becomes more effective the more it is used. Minimum Efficiency Reporting Value (MERV) indicates a filter s ability to trap particles from the air we breathe. The acronym MERV indicates a filter s lowest level of performance during its useful life. In other words, MERV 8 filters will trap 95 percent of efficiency of the unit. For this reason, filters must be washed periodically. The unit traps particulates 5 microns or larger and is 75 percent effective at trapping particulates as small as 3 microns. Mold spores vary in size from 1 to 100 microns, but many of the most common are between 2 and 20 microns. 10 This means that the RecoupAerator is able to filter out a vast majority of airborne mold spores HUMIDITY CONTROL Use of an ERV is even more important in hot, humid climates where bringing in outdoor air can also mean bringing in moisture. Adding moisture cannot only make building occupants feel uncomfortable and require additional cooling, but it can actually damage building interiors and porous wall coverings, furnishings, and carpeting. Moisture encourages mold growth and dust mite activity. ERVs are capable of reducing the moisture content of the fresh incoming air. As a result, they can reduce the load on the air conditioning system during summer operation. Indoor humidity levels are prevented from becoming too dry or too humid by the partial transfer of White Paper: Clean Air and the RecoupAerator, 1/27/04, , page 4

5 water vapor. In Stirling s case, moisture will be transferred mostly through evaporation within the transfer core, but also through condensation on the surface of the matrix material. The latent heat is transferred as the moisture condenses from the air stream with the higher humidity or as the moisture is picked up by the polymer matrix. The matrix then releases the moisture by evaporation as the porous matrix rotates into the air stream with lower humidity ratio. Thus, sensible and latent energy are transferred simultaneously. During winter, ERVs provide a continuous supply of warm, fresh air while simultaneously eliminating stale indoor air. During the cooling season, the reverse happens. The cool indoor air is exchanged with the warm incoming air, decreasing the temperature of the incoming air. Additionally, moisture from the outdoors is transferred into the exhaust air stream before it reaches the house. This reduces the load on the air conditioner, enabling it to control the humidity more effectively, which can reduce operating costs. PRESSURIZATION Pressure is a force, or weight, exerted on a surface per unit area, and is measured in Pascals (Pa). 1 Pa is equal to 14.7 pounds/in 2. The pressure exerted by a kilogram mass on a surface equals 9.8 Pa. The pressure exerted by the whole atmosphere on the Earth s surface is approximately 100,000 Pa. Usually, atmospheric pressure is quoted in millibars (mb). 1 mb is equal to 100 Pa, so standard atmospheric pressure is about 1000mb. Actual values of atmospheric pressure can vary from place to place and from hour to hour. 11 Air flows from regions of high pressure to regions of low pressure. In a highpressure system, air pressure is greater than in the surrounding areas. The pressure inside a house is usually lower than that of the atmosphere outside and can cause problems. Fluctuations in pressure can be initiated by simple acts such as shutting a bedroom door or turning on the dryer. These fluctuations create an even lower pressure inside a house in relation to the outside and can pull in unwanted moisture and pollutants, including carbon monoxide, for instance, from the garage; pesticides that seep in where the wall and floor join; and radon gas from below the home. The moisture being pulled into a house can cause problems that are not usually detected until a significant amount of damage has already occurred. Moisture collects on the inside of walls in homes and produces a perfect environment for mold growth. This mold growth generally goes undetected until a significant amount of damage has occurred. In addition to structural damage, the mold also produces tiny spores that flow into the house with the air, pushed in from the ambient outside pressure. As previously discussed, many health-related issues come from having mold and mold spores inside the home. The RecoupAerator alleviates these issues because it senses indoor pressure in relation to outdoor pressure and adjusts inside pressure to its ideal based on seasonal fluctuations. When used as part of a whole house system, the RecoupAerator is able to create this pressurization by bringing in more fresh air than it pulls out. With a whole-house systems approach, Stirling s products White Paper: Clean Air and the RecoupAerator, 1/27/04, , page 5

6 pressurize a home so that in the winter the inside pressure is balanced or slightly negative; in the summer, Stirling s products will pressurize the home so that the inside pressure is 3 to 5 Pa higher than the outside pressure. This pressure change is a small, virtually unnoticeable amount, but it is enough to prevent moisture, pollutants, and other harmful substances such as radon from being pulled into the home. This design also ensures that the RecoupAerator adjusts any variation of pressurization. Homes that use fresh-air ventilation and pressure-management techniques can maintain better air quality and reduce the possibility for molds and allergens to enter AmAirCare.com and 3 AmAirCare.com Burke, Grossman, Locke and Tran. Chemical and Radiation Environmental Risk Mangement at the Crossroads: Case Studies Department of Computing and Mathematics, Manchester Metropolitan University: ( 8 A.M. Druma and Alam, M.K. Numerical Model for Rotary Heat Exchanger with Porous Matrix. June Envirochex: 11 Department of Computing and Mathematics, Manchester Metropolitan University: ( 12 Tucson Electric: White Paper: Clean Air and the RecoupAerator, 1/27/04, , page 6