This past July was the hottest recorded month in human history. Heat waves smashed temperature records worldwide and even brought summer temperatures to Chile and Argentina during the Southern Hemisphere’s winter. It’s more than just a matter of sweaty discomfort. Severe heat is the deadliest of all weather events; in the U.S. alone, it kills more people each year than floods, tornadoes and hurricanes combined. As climate change worsens, access to artificially cooled spaces is rapidly becoming a health necessity—and an issue of basic human rights.
Yet standard air-conditioning systems have ensnared us in a negative feedback loop: the hotter it is, the more people crank the AC—and the more energy is used (and greenhouse gases are emitted) as a result. “We’re in a vicious cycle,” says Nicole Miranda, an engineer researching sustainable cooling at the University of Oxford. And “it’s not only a vicious cycle, but it’s an accelerating one.” Cooling is the fastest-growing single source of energy use in buildings, according to 2018 data from the International Energy Agency (IEA). Following a business-as-usual scenario, the IEA projects that worldwide annual energy demand from cooling will more than triple by 2050. That’s an increase of more than 4,000 terawatt-hours, which is about how much energy the entire U.S. uses in a year.
It’s becoming increasingly clear that humans cannot outrun climate change with the same air-conditioning technology we’ve been using for nearly a century. Breaking the cycle requires new innovations that will help bring cooler air to more people with less environmental impact.
One well-known problem with current AC systems is their reliance on refrigerant chemicals, many of which are potent greenhouse gases. Some projects aim to replace these substances with less-harmful coolants—but even if they do, the refrigerants make up only a fraction of air-conditioning’s climate toll. About 80 percent of a standard AC unit’s climate-warming emissions currently come from the energy used to power it, says Nihar Shah, director of the Global Cooling Efficiency Program at Lawrence Berkeley National Laboratory. A lot of recent work has gone into boosting the energy efficiency of compressors and heat exchangers, which are parts of standard AC designs, Shah explains. Yet more ambitious projects aim to reduce the amount of work those components must do in the first place.
Standard air conditioners cool and dehumidify simultaneously through a relatively inefficient mechanism: to condense water from the air, they cool the air well beyond the comfort range, according to Shah. Therefore, many newer designs separate the dehumidification and cooling processes, thus avoiding the need for subcooling.
For example, some older air conditioning designs old ones eliminate humidity from the air. with a desiccant. Materials (similar to silica gel in packaging you might find in a bag of jerky or pill bottle). The dry air can then be cooled to a more comfortable temperature. This process may require additional energy as the desiccant needs to be "charged" with heat. But some companies, including Somerville, Massachusetts-based startup Transaera, recycle the heat generated during the cooling process to recharge the desiccant. Transaera says the system it is developing could use 35% less energy than an average standard air conditioner.
Efficiency gains still possible greater when combined with dehumidification and evaporation. Cooling, which completely eliminates the energy-intensive process of vapor compression. In vapor compression, the way traditional air conditioning systems work, a refrigerant goes through a cycle in which it condenses and expands differently, allowing it to absorb heat from inside and release it outside. In contrast, evaporative cooling is a simpler process. Sweat cools our skin in the same way: when water changes from liquid to gaseous, it absorbs heat. Swamp coolers, do-it-yourself devices that use a fan to blow air over the ice, work the same way. And in dry climates, people have used evaporative cooling for thousands of years. For example, in ancient Iran, people devised yakhchāls (large cone-shaped clay structures with solar chimneys) that used air circulation and evaporation from adjacent water to lower temperatures enough to produce and store ice in winter and summer.
But this strategy also increases humidity, so, being a refrigeration system, it tends to only work when the weather is hot and dry; When the humidity exceeds a certain level, the comfort gain from a lower temperature is cancelled. To address this problem, research groups, including the cSNAP team at Harvard University, have developed air conditioners that use a hydrophobic barrier to perform evaporative cooling while retaining moisture. As an added bonus, refrigerants (which are often many times more potent greenhouse gases than carbon dioxide) are not involved. “We hope to provide an air conditioner that is 75 percent more energy efficient,” says Jonathan Grinham, assistant professor of architecture at Harvard and one of the principal designers of cSNAP.
Meanwhile, Florida-based Blue Frontier is testing an air conditioning system commercial with both desiccant systems . (in this case liquid saline solution) as well as evaporative cooling. This design dries the air and then splits it into two adjacent streams, says company CEO Daniel Betts. The air in a flow is cooled directly through the reintroduction of moisture and evaporation. The other airflow is kept dry and cool by passing through a thin aluminum wall which sucks the cold (but not the humidity) from the first airflow. The liquid drying salt then passes through a heat pump system to be recharged. To maximize efficiency, the heat pump can be used at night, when there is less load on the electricity grid, and the desiccant can be stored for use during the hottest part of the day. Based on the company's field tests, "we're seeing a 50 to 90 percent reduction in energy use," says Betts.
But Blue Frontier, cSNAP and Transaera have not yet moved from the testing phase to commercialization. All three groups believe commercial release is expected within at least a few years. And even then, there will be obstacles that could prevent the new systems from replacing traditional air conditioning. This includes relatively higher manufacturing and installation costs, industry inertia, and policies that encourage cost-effective over efficient systems.
Even with the best technology available, efficiency improvements alone may not be enough to offset the widely anticipated increase in air conditioning use. Based on the best model, the IEA predicts that global cooling will require 50 percent more energy over the next 25 years than today due to rising demand, Shah says. Simply replacing all existing air conditioners with a better model and turning it off won't work. Instead, a truly cooler future will have to resort to other passive strategies that rely on urban planning and building design to minimize cooling needs. Shah and Miranda say it is extremely important to incorporate green space and water into urban landscapes by shading windows, positioning new buildings to take advantage of natural air circulation, and modernizing buildings with better insulation and reflective panels that can dissipate heat in the space.
Read Also : Why was India named India and not Bharat?
White Clover Markets
This past July was the hottest recorded month in human history. Heat waves smashed temperature records worldwide and even brought summer temperatures to Chile and Argentina during the Southern Hemisphere’s winter. It’s more than just a matter of sweaty discomfort. Severe heat is the deadliest of all weather events; in the U.S. alone, it kills more people each year than floods, tornadoes and hurricanes combined. As climate change worsens, access to artificially cooled spaces is rapidly becoming a health necessity—and an issue of basic human rights.
Yet standard air-conditioning systems have ensnared us in a negative feedback loop: the hotter it is, the more people crank the AC—and the more energy is used (and greenhouse gases are emitted) as a result. “We’re in a vicious cycle,” says Nicole Miranda, an engineer researching sustainable cooling at the University of Oxford. And “it’s not only a vicious cycle, but it’s an accelerating one.” Cooling is the fastest-growing single source of energy use in buildings, according to 2018 data from the International Energy Agency (IEA). Following a business-as-usual scenario, the IEA projects that worldwide annual energy demand from cooling will more than triple by 2050. That’s an increase of more than 4,000 terawatt-hours, which is about how much energy the entire U.S. uses in a year.
It’s becoming increasingly clear that humans cannot outrun climate change with the same air-conditioning technology we’ve been using for nearly a century. Breaking the cycle requires new innovations that will help bring cooler air to more people with less environmental impact.
One well-known problem with current AC systems is their reliance on refrigerant chemicals, many of which are potent greenhouse gases. Some projects aim to replace these substances with less-harmful coolants—but even if they do, the refrigerants make up only a fraction of air-conditioning’s climate toll. About 80 percent of a standard AC unit’s climate-warming emissions currently come from the energy used to power it, says Nihar Shah, director of the Global Cooling Efficiency Program at Lawrence Berkeley National Laboratory. A lot of recent work has gone into boosting the energy efficiency of compressors and heat exchangers, which are parts of standard AC designs, Shah explains. Yet more ambitious projects aim to reduce the amount of work those components must do in the first place.
Standard air conditioners cool and dehumidify simultaneously through a relatively inefficient mechanism: to condense water from the air, they cool the air well beyond the comfort range, according to Shah. Therefore, many newer designs separate the dehumidification and cooling processes, thus avoiding the need for subcooling.
For example, some older air conditioning designs old ones eliminate humidity from the air. with a desiccant. Materials (similar to silica gel in packaging you might find in a bag of jerky or pill bottle). The dry air can then be cooled to a more comfortable temperature. This process may require additional energy as the desiccant needs to be "charged" with heat. But some companies, including Somerville, Massachusetts-based startup Transaera, recycle the heat generated during the cooling process to recharge the desiccant. Transaera says the system it is developing could use 35% less energy than an average standard air conditioner.
Efficiency gains still possible greater when combined with dehumidification and evaporation. Cooling, which completely eliminates the energy-intensive process of vapor compression. In vapor compression, the way traditional air conditioning systems work, a refrigerant goes through a cycle in which it condenses and expands differently, allowing it to absorb heat from inside and release it outside. In contrast, evaporative cooling is a simpler process. Sweat cools our skin in the same way: when water changes from liquid to gaseous, it absorbs heat. Swamp coolers, do-it-yourself devices that use a fan to blow air over the ice, work the same way. And in dry climates, people have used evaporative cooling for thousands of years. For example, in ancient Iran, people devised yakhchāls (large cone-shaped clay structures with solar chimneys) that used air circulation and evaporation from adjacent water to lower temperatures enough to produce and store ice in winter and summer.
But this strategy also increases humidity, so, being a refrigeration system, it tends to only work when the weather is hot and dry; When the humidity exceeds a certain level, the comfort gain from a lower temperature is cancelled. To address this problem, research groups, including the cSNAP team at Harvard University, have developed air conditioners that use a hydrophobic barrier to perform evaporative cooling while retaining moisture. As an added bonus, refrigerants (which are often many times more potent greenhouse gases than carbon dioxide) are not involved. “We hope to provide an air conditioner that is 75 percent more energy efficient,” says Jonathan Grinham, assistant professor of architecture at Harvard and one of the principal designers of cSNAP.
Meanwhile, Florida-based Blue Frontier is testing an air conditioning system commercial with both desiccant systems . (in this case liquid saline solution) as well as evaporative cooling. This design dries the air and then splits it into two adjacent streams, says company CEO Daniel Betts. The air in a flow is cooled directly through the reintroduction of moisture and evaporation. The other airflow is kept dry and cool by passing through a thin aluminum wall which sucks the cold (but not the humidity) from the first airflow. The liquid drying salt then passes through a heat pump system to be recharged. To maximize efficiency, the heat pump can be used at night, when there is less load on the electricity grid, and the desiccant can be stored for use during the hottest part of the day. Based on the company's field tests, "we're seeing a 50 to 90 percent reduction in energy use," says Betts.
But Blue Frontier, cSNAP and Transaera have not yet moved from the testing phase to commercialization. All three groups believe commercial release is expected within at least a few years. And even then, there will be obstacles that could prevent the new systems from replacing traditional air conditioning. This includes relatively higher manufacturing and installation costs, industry inertia, and policies that encourage cost-effective over efficient systems.
Even with the best technology available, efficiency improvements alone may not be enough to offset the widely anticipated increase in air conditioning use. Based on the best model, the IEA predicts that global cooling will require 50 percent more energy over the next 25 years than today due to rising demand, Shah says. Simply replacing all existing air conditioners with a better model and turning it off won't work. Instead, a truly cooler future will have to resort to other passive strategies that rely on urban planning and building design to minimize cooling needs. Shah and Miranda say it is extremely important to incorporate green space and water into urban landscapes by shading windows, positioning new buildings to take advantage of natural air circulation, and modernizing buildings with better insulation and reflective panels that can dissipate heat in the space.
Read Also : Why was India named India and not Bharat?