Reinventing the Portable Air Conditioner - Part 1
If you’re like me you have a love-hate relationship with air conditioned buildings. Relief from sweaty furnace heat outside is great at first. Before long, though, I’m feeling cold and need to return outside to feel warm again. I ask myself “why do they keep this building so cold: it’s freezing inside and too hot outside. Surely they must be wasting energy!”
After a few days, constantly going from hot to cold to hot again, the sniffles start, often a prelude to headaches and ‘flu.
Sick building syndrome is not the imagination of a few hypochondriacs.
How did we get to this? Why are buildings in hot climates made to feel so cold?
Are there healthier, energy-efficient, alternatives?
Recently I attended a special conference "Comfort At The Extremes" held in Dubai. I learned much about the ways that ideas on comfort in buildings are changing.
Air conditioning first became common in the USA after the 1940s and the invention of the compact window air conditioner, later fully ducted air conditioned buildings, and eventually the portable air conditioner as well. Refrigeration machines that provide the cooling can be challenging to design, so engineering specialists formed the American Society for Heating, Refrigeration and Airconditioning Engineering, ASHRAE. Through the society publications, they shared their knowledge in the form of standards to enable engineers to easily design reliable air conditioning systems, greatly reducing the cost.
To simplify designs, engineers devised comfort scales, like this example: cold; cool; slightly cool; neither warm nor cool; slightly warm; warm; and hot. Then they asked lots of American office workers, mainly men dressed in suits, to “vote” on how they felt in buildings at different temperatures, knowing that everyone has a different subjective feeling of comfort and temperature. The scale is numbered -3 to 3 and engineers calculate the average “vote” as an indication of overall comfort. The conclusion: most office workers feel comfortable in air at 21 - 23°C, 60% humidity with moving at less than 0.3 m/sec.
To keep the building cool in hot weather, the air conditioning system has to provide colder, drier air that warms up as it absorbs heat and humidity from the building, people, all the machinery and lights, and outside air that leaks in through doorways and construction gaps. If you’re sitting next to one of the air conditioning vents, the chances are you will feel cold.
After all this effort, other countries simply copied the American standards. The rest of us ended up with buildings that were designed to keep average American businessmen comfortable.
Image of Singapore Marina Bay by Peter Nguyen (unsplash.com)
Since then, many engineers and building designers have worked to improve comfort and energy-efficiency. At the same time, the global climate is warming, mostly because we are all relying on burning fuels like coal and oil for energy. It’s that energy that enables seven billion or more people to live on earth with mostly enough food, water, shelter, transport and communications.
As the climate warms, more and more people feel the need for air conditioning.
Yet even now, cities can be 2-4°C warmer than surrounding land, just because of the heat exhausted by air conditioning systems. As they get hotter, cities consume even more energy for cooling. And it’s not just city office buildings. One of the main status symbols for people in hot climates is air conditioning at home. Air conditioners are cheap enough for middle classes, even in poor countries. At the rate we are going, by 2100, we will have 0.5°C additional global warming, just because of air conditioners. With scientists telling us that we have to eliminate emissions of gases like CO2 that cause global warming by the 2050s, the need to minimize energy consumption is becoming even more urgent than before.
Around the world, engineers know we have to become much smarter, and quickly!
Are there energy-efficient and healthy solutions that can keep everyone comfortable, even in the hottest climates? Yes! Air conditioning is being re-invented, and not just by Close Comfort. Engineers are coming up with ingenious ways to keep people comfortable with much less energy. In the next article, we will learn more about human comfort and how a little discomfort is actually healthier.
References: Wikipedia: Thermal Comfort. (2019). Retrieved from https://en.wikipedia.org/wiki/Thermal_comfort on April 23, 2019