Wet s the Difference or How Evaporative Cooling Helped Save Big Bucks, the Planet, and My Marriage In my 30+ year career as an energy expert with a well known California utility company, whose name I will not mention, but whose initials are the same as in the words Poodles, Geese and Eagles, it seems that evaporative cooling has always been in the forefront, if not in the back of my mind. In this paper, I would like to take a brief journey into the recent past, the rapidly warming present, and the hellishly hotter future with - evaporative cooling. If you live in the Bay Area, or any number of other freakish coastal communities where the summer temperatures sometimes approach 90⁰ for minutes at a time, you will probably find this dissertation boring (not Jana) and of no consequence in your fabulous existence, so STOP READING NOW. If, however, like me, you are a denizen of the hot interior valley, you understand only too well why your location in any number of inland towns and villages regularly receives enough solar radiation and heat so that: The best parking place is determined by shade instead of distance Hot water now comes out of both taps. Cows regularly give evaporated milk Not only can you fry an egg on the sidewalk, you can cook hash browns to go with it Fellow summer heat victims, this paper is for you. Almost No Escaping the Heat My family came to the San Joaquin Valley in the 1890s when things like electricity, piped natural gas, automobiles, and personal happiness were not readily available or hadn t been invented yet. As you could probably guess, the internet was in its infancy so most people relied on talking to each other and reading books to learn stuff. I remember talking to my grandmother, who was born in 1890, about her experiences growing up in Fresno. She talked about how they would often sleep outside on screened-in sleeping porches during the summer to try to get cool. Another popular method to beat the heat was to leave town.
Will and Anna Riding escaping the valley heat in 1910. It was the first trip by a couple from Fresno to San Francisco on a motorcycle. She wore divided skirts, in order to straddle the bike. This, of course, scandalized the neighbors. My grandmother was a telephone operator and worked nights, so her mom would take bed sheets or blankets soaked in water and hang them inside of the porch screens, to help her sleep during the day. When electricity came to their block, electric fans would pull the night air through the moist cloth to cool the room. The only insulated structures in those days were the commercial ice houses. In order to keep winter-cut lake ice frozen through the summer, they packed the walls with redwood shavings or sawdust. If the average homeowner did anything to insulate his home from the heat, it was generally to grow vines on trellises that would both shade and provide cooling to the house through - you guessed it evaporation!
The Riding clan utilizing the latest in residential cooling technology, Fresno, July, 1904. Notice the highly reflective B.S. clothing (before sunscreen). They also used evaporation to keep their food from spoiling. The old-timers, which in those days meant 49ers and other settlers, used to build a big open shelved rack and cover it with burlap bags. At the top and bottom of the box they set a pan of water with the ends of the burlap in the water. By osmosis the burlap would get wet, and when a breeze came up you could cool food through - you guessed it evaporation! This system freed folks from having to consume food quickly before it spoiled. Food and water-borne sickness was a common occurance but with the new food cooler, foodstuffs could last for a week or so. Before food cooling, canned, salted, dried and pickled fare was generally thought to constitute real food, while beer and wine was consumed liberally, which picked the people and helped them not to notice the nasty food, but I digress
This was one of the first built-in refrigerators, circa 1900, Fresno, CA. Evaporative cooling technology was also utilized early on to cool automobiles. Car air conditioning was an aftermarket, add-on product for cars that first appeared in the 1930 s. Not really air conditioning as we think of it today, these car coolers were installed on the passenger side window and used balsa-wood shavings in a pad within a cylindrical unit. They had a reservoir that held about a gallon of water, which soaked the shavings and, when air was forced through the unit, the water would evaporate providing a cooling effect through - you guessed it evaporation! The cool air would
blow through a vent at right angles on the main unit into the passenger's compartment which would provide cooling for about 100 to 150 miles. It would only work when the car was in forward motion, and stopped working altogether when the car wasn t moving forward. It was very effective in reducing summertime idling, but back seat passengers sometimes got an earful of water droplets. That concept, albeit slightly more refined, became the evaporative coolers that to this day provide a low-cost alternative to refrigerated air conditioning.
What Is Evaporative Cooling, Really? Evaporative coolers, which are sometimes called swamp coolers (perhaps due to the musty smell associated with early coolers), or desert coolers (due to the area in which they are the most useful), are cooling devices that cool air in a very simple way yes, you guessed it again through the evaporation of water. Evaporative coolers can work wonderfully well, provided the outside air they are drawing in is dry and desert-like. For instance, in the United States, evaporative coolers are most useful in areas such as Denver, Albuquerque, El Paso, Phoenix, Tucson, and of course, Fresno. Actually anyone living in the 400 mile stretch of the great Central Valley of California from Redding to Bakersfield could benefit from evaporative cooling. On the other hand, as the humidity increases, the ability for evaporative coolers to cool the air effectively decreases. Residents of cities which are actually swampy, such as New Orleans, Mobile, or Biloxi would not get much use at all out of an evaporative cooler, and would probably not appreciate it s ability to add yet more humidity to their already saturated, sweat-soaked lives. (No offense intended.) Simply put, swamp coolers were not designed to work in swamp-like conditions. The Technical Part As you ve seen before, an evaporative cooler produces effective cooling by combining a natural process - water evaporation - with a simple, reliable air-moving system. Fresh outside air is pulled through moist pads where it is cooled by evaporation and circulated through a house or building by a large blower. As this happens, the temperature of the outside air can be lowered as much as 30 degrees. How Much Coolth Can A Cooler Cool? The temperature of air coming out of an evaporative cooler depends on the temperature and the humidity of the air going in.
Actual chart from the Arizona Almanac shows that an evaporative cooler can deliver comfortable air under a wide variety of typical summertime temperature and humidity ranges. (Your results may vary.) In addition to a reduction in sensible heat, which is heat that has the good sense to vacate your house, evaporative cooling offers an additional benefit by making the occupants of a room feel 4 to 6 degrees cooler than the actual temperatures shown on the chart. Technology Marches On But like all good, simple inventions, it was soon superseded by a more complex method called refrigeration. After WWII this new air conditioning became popular because of its ability to cool and de-humidify the air, and would work no matter what the outside humidity might be in Biloxi.
It also consumes roughly four times as much electricity as an evaporative cooler, and is more expensive to install and maintain. Air conditioners also require ozonedamaging refrigerants, and, most importantly for indoor air quality, they re-circulate the same stale air over and over again.. Air conditioning is a closed system, taking air from inside a house and recycling it. Normally, I m all for recycling, but VOC s? Puhleeze! Cool New Designs There are currently two main types of evaporative cooling systems in the marketplace, many with advanced electronics that maximize comfort. Direct Systems As their name implies, direct evaporative systems evaporate water directly. The cooler, slightly more humid air enters the building, sensibly cools the occupants and exits through openings such as doors, windows and specially designed exhaust vents. Direct systems require 100 percent outside air and will not cool all parts of a house if adequate exhaust openings are not provided. As shown on the Arizona Almanac chart (previous page), when outside temperatures
are above 100 degrees and the relative humidity is above about 30 percent, the cooling effect is substantially reduced. Keeping folks cool since the 1930 s These original-style direct evaporative coolers can be expected to reduce the ambient temperature by up to 20 degrees using aspen or "straw-type" pads. Clogging of the water distribution system and mineral buildup is a constant issue and can diminish the cooling effectiveness of the unit. Newer, more advanced evaporative coolers with 8 to 12 inch thick rigid media pads, and fresh water replenishment systems improve the cooling efficiency even more.
New vs. old technology pads. It must be true he is wearing a white lab coat.
However even the most advanced direct system can only be expected to offset air conditioning systems 65 to 70 % of the time during the summer with relative comfort. Direct evaporative coolers act as a humidifier because they add moisture to the air, and will often make the dry air more comfortable to breathe. Because the air is not recirculated through the building, there is no excess buildup of moisture. The fact that evaporative cooling adds some moisture to the air, which helps to keep wood furniture and fabrics from drying out, is seen as a benefit by most people. The moist pads through which the outside air flows are also fairly efficient air filters, trapping some dust and pollen. Since the pads are continually wetted, particles are flushed out and trapped in the bottom of the cooler. IEQ and my wife. Air quality can refer to the amount of pollutants in the outdoor air or the indoor air. This paper deals with indoor environmental quality, or IEQ. Outdoor air is generally accepted as being healthier (fewer pollutants per unit of air volume) than indoor air, although Central Valley cities do have some of the smoggiest and most particulateladen summer days in the U.S. (We re #1, we re #1!) Pollutants generated indoors come from out-gassing of building materials (VOCs), carpet adhesives, furniture and from the occupants themselves. In addition, other natural and artificial odors must be exhausted. Dust is a major source of particles, and each gram of dust also contains hundreds of thousands of fungal spores and also may contain pesticides and heavy metals.
Our current house as depicted on the Cartoon Network The concentration of pollutants inside a building may be two to five times higher than outside levels. Children, folks with compromised immune systems, and my wife are particularly vulnerable to such pollutants. When we first got married, she was allergic to cats and dogs, many yummy foods, and hot summers in the valley. In 1992 we built a house that had both air conditioning and direct evaporative cooling. She was pretty sure that the evap cooler would make her allergies worse but humored me in my insistence that we include one in our home plans. We started to use the evaporative cooler as often as we could, agreeing that when it got too hot or muggy, we would run the a/c. Coincidentally, when the a/c was on, her sinuses would start giving her trouble and invariably she would get a sinus infection. When we turned off the a/c and ran the evap cooler, she got better. I did some research and according to the U.S. EPA, a well recognized method of controlling indoor air pollutants is to circulate more outside air in the home.
Dust, Pollen, and Mold Oh My! Although direct evaporative coolers are not very efficient at cleaning tiny particles from the air, they do catch and wash down some dust and larger particles, and as we surmised, probably pollen and mold spores too. The newer rigid media is much more efficient at trapping airborne stuff - it holds on to the dust longer, and eventually washes it into the sump, also known as a viscous impingement filter, or the mechanical equivalent of my wife s nasal passages. According to the EPA again, particles larger than 8 to 10 microns in diameter are separated and retained by the upper respiratory tract. While evaporative media was not primarily designed to operate as a filter, the 12" rigid media will capture over 90% of particles 5-10 microns or larger. Fungus spores are usually from 10 to 30 microns, while common pollen grains are in the 20 to 40 micron range.
Indirect/Direct 2-Stage Systems Indirect/direct 2-stage evaporative coolers (IDEC) add a second stage of cooling which occurs before the evaporatively cooled air enters the dwelling. This process further lowers the temperature of the incoming air. IDECs utilize a unique heat exchanger to reduce air temperature without adding significant humidity to the airstream. These units typically have an effectiveness of 100 to 115 percent by cooling the air to a temperature slightly below the outdoor air wet-bulb temperature, a fairly technical term that I can explain later if you really want me to. Tests found that IDECs were capable of achieving energy savings of 80 percent or more, relative to an air conditioning during summer peak conditions. We tested that finding out in 2009 during the heat wave that routinely saw temperatures climb above 110⁰ for two full weeks. Believe me or not, our 2-stage
Mastercool IDEC never let the inside temperature get above 80⁰. Even my wife was impressed! As a point of reference, air conditioners (by design) will have a hard time keeping your house cool when the mercury climbs above 103⁰. Outdoor and indoor temperatures, Riding Ranch, July 2009. Not bad for a swamp cooler. Water Consumption and Water Quality Concerns about water consumption are common in any discussion of evaporative cooling. However, such concerns are generally misplaced, especially as they relate to the current advanced level of IDEC technology. Some cities and water agencies in the west have misguidedly begun to discourage evaporative cooling through education campaigns, and incentives for homeowners to remove evaporative cooling systems. THIS IS WRONG! Advanced 2-stage evaporative cooling systems have significantly reduced water consumption compared to the systems of just a few years ago, using intelligent water quality controls.
Experts have emphasized that the water consumption for an advanced residential evaporative cooling system could be more than offset by installing a low-flow showerhead in the home and that the amount of water consumed by an evaporative cooling system is less than the water that would be consumed by a power plant providing electricity for a compressor-based air conditioner. Conclusions So, in summary, we have been able to survive and even enjoy many scorching valley summers primarily relying on our indirect/direct 2-stage evaporative cooler. Its low energy use has helped us to reach zero-net electricity at the ranch, as part of our comprehensive plan utilizing conservation, energy efficiency, wind and solar technologies. Simple things that most anyone can achieve. My wife, originally the skeptic, has become the greatest advocate for this technology. She and I agree that the overall cooling effect is much more comfortable than air conditioning. Factor in the improved air quality, and tremendous energy savings, and I all I can say is... water you waiting for? Virginia and Bob riding out the valley heat in very little pain or discomfort.