Global economic development combined with climate change is expected to result in over a billion new consumers installing air conditioning in their homes and businesses in the coming decades. The International Energy Agency (IEA) has predicted that the energy demand for indoor cooling will be 300 percent above today’s level by 2050, making cooling by far the largest power consumption in the global building sector. However, these estimates were made prior to the COVID-19 pandemic. Our research shows that this projected increase will come much sooner if the expanded indoor fresh air requirements adopted to combat COVID-19 transmission persist after the pandemic.
In order to understand this impending boom in air conditioning, one must recognize the historically synonymous and problematic relationships between the terms “air conditioning”, “cooling” and “ventilation”. Air conditioning is not necessarily synonymous with cooling people and does not necessarily provide fresh air. In a typical “air-conditioned” building, more than 50 percent of the cooling has nothing to do with the air temperature, but with the temperature of the walls and other surfaces around you. Since most of us grow up with thermostats that only measure air temperature, these misconceptions have led to a reliance on air conditioning for comfort.
Central air conditioning has been the main mode of cooling and ventilating people indoors since the mid-20th century. The long-term expectation is that alternating current can offer buildings both thermal comfort and air quality at the same time. To avoid excessive heat loss, buildings have been designed with sealed envelopes that do not allow fresh air on demand, such as would be the case when opening windows in an office building. Air conditioning changed the way we design buildings, circulating conditioned air for efficiency at the expense of disease transmission.
If we continue to adhere to the current building cooling paradigm, the health of residents and the energy efficiency of a building will remain competing factors. This begs the question: How can we create a healthy indoor climate while avoiding an increase in energy consumption? Is there an alternative to alternating current that offers thermal comfort but does not need to cool large amounts of fresh air?
In an international collaboration of researchers from institutions in the USA, Canada, Europe and Singapore, we have developed a simple, inexpensive and scalable solution that makes people feel comfortable without regulating the room air temperature. Our technology is based on the concept of radiant heat transfer, in which the surfaces surrounding people are cooled or heated instead of cooling or heating the air. We all experience radiant heat transfer, even if we’ve seldom heard the term. Radiant heating is the feeling of the hot sun on our face on a cool spring day. Radiant heating is the direct warmth of a campfire that keeps us warm on a cool summer night. Radiant cooling is the same physics but in the opposite direction. Radiant heat always flows from warmer to cooler surfaces. Just as the campfire loses its warmth to our cool skin and we feel warm on a hot summer day, we can surround our bodies with cold surfaces and feel good. We lose our body heat to the cool surfaces around us.
During a first demonstration of our “Cold Tube” radiation system installed in Singapore, we made sure that people feel cool with 100 percent fresh air and 50 percent less energy and thus half the associated carbon emissions of a typical air conditioner. In our latest research, we show that this technology can be used in all major climates and would result in average energy savings of 10 to 45 percent, while significantly increasing ventilation in critical spaces such as public schools.
When we install radiant cooling surfaces in buildings, we separate the devices with which we ventilate the building from the devices with which we feel thermally comfortable. We can actually keep the windows open with a radiant cooling system, freeing ourselves from the trap of a historic air conditioning system in which contaminants circulate inside along with cold air. With radiant cooling, we can build truly sustainable and healthy buildings – during a pandemic and beyond.
This is also about education. In our own lives we may all be used to setting a thermostat that only controls room air temperature, but this is a legacy of the climate sector as it emerged in the early 20th century. For radiation systems to become widespread, people need to understand how they work and how they are controlled. Today, if you want to install a radiation thermostat in your home that can regulate the surface temperatures of your walls, ceilings, and floors, you must first find contractors who know how to install a radiation system and then get used to the thought of being comfortable do by changing the temperature of the surfaces, not the air.
A major technological change always requires a major cultural change that permeates several areas of society. In the case of the built environment, designers, craftsmen, property owners and building owners need to be on board. And if the government is seriously investing in infrastructure, we must take the opportunity together to rethink old paradigms and not invest in the status quo. Because if we want to fight and win against the climate emergency and keep people healthy indoors, it is time to consider more sustainable alternatives to air conditioning.
This is an opinion and analysis article.