By Aaron Meles, Vice President of Product, Mojave Energy Systems
Walk into any office, hospital or grocery store on a hot day and you will undoubtedly find it cool and comfortable. After more than a century of living with air conditioning (A/C) we simply take it for granted. After all, it usually works. So, in keeping with the adage, if it is not broken, don’t fix it, today’s cooling systems still operate on the same basic principles that the first A/C units were built on in 1902.
However, widespread A/C use has resulted in a significant negative impact on our planet. It is because of this that we now face the reality that the current approach is, in this sense, broken. Air conditioning alone is responsible for 3.9% of the total global greenhouse gas emissions. I’m part of a team that has been focused on solving the problem of how to maintain the comfort levels we are used to while lowering our climate impact, all without raising the cost of the equipment. We believe the answer is liquid desiccant air conditioning. It cools in essentially the same way yet gains significant energy savings by simultaneously lowering humidity.
AC for the 21st Century
For the majority of the 20th century, the primary objective of A/C was to reduce air temperature. This was accomplished by moving heat around. Traditional units have long relied on vapor compression (VC) to remove heat and humidity from indoor air through ducts and return cooled air inside. This approach made sense and worked very well for many decades because VC is an effective solution for changing air temperature in structures like those built in the 1900s that were less airtight and had plenty of indoor heat sources that minimized humidity issues. VC has never been a strong solution for controlling humidity, but until now, that wasn’t a concern.
Fast forward to today, where new building techniques, areas of development, and global warming have changed the A/C equation.
Ventilation codes have long been in place to improve the indoor air quality of more tightly built buildings and homes. Humidity has increasingly become a greater concern, as population centers have migrated, and sealed structures require more dew point control and less heat removal.
And consumers and businesses have begun to prioritize energy efficiency to achieve cost savings and offset additional impact on the planet. Look around your house, and you’ll likely find mostly LED light bulbs and perhaps just a few of the old incandescent bulbs. You may already have new energy-efficient windows. Both examples save money in the long-term and help to curb climate change. The fact is that buildings account for a large portion of greenhouse gas emissions, and 1,950 MtCO2eq come from HVAC globally every year. To put that into perspective, that’s more than what’s emitted by all forms of transportation in the U.S. annually.
Together these factors tilt the traditional A/C balance in the other direction, now leaning toward humidity rather than heat. But because we are still using A/C systems designed to handle more heat and less humidity, buildings now must use more energy to control humidity than to control temperature, which is expensive, inefficient, and doesn’t address our climate concerns.
Changing the Nature of Air Conditioning
It is time to update our A/C technology. The path to the future combines tried and true A/C elements, like heat pumps, with new technology, such as liquid desiccant, to reverse the heat versus humidity equation. While desiccants have been used in laboratories and other specialized applications in a solid phase for years (think of the silica gel packets that come in electronics packaging), this naturally occurring moisture suppressor can also be used in liquid form. It allows for not only the reduction of humidity but also the benefit of reuse, making it a continuous and highly effective process for meeting today’s cooling needs.
Liquid desiccant even solves the challenges of solid desiccant in A/C because it doesn’t need to reach high temperatures for regeneration. Liquid desiccant can use heat from a VC system to evaporate out 100% of the moisture it absorbs. Additionally, unlike the solid version, liquid desiccant allows for flexibility with flow rates and can have its concentration manipulated by the unit’s control system to dial in the perfect air conditions. This innovation eliminates the challenges of VC and improves solid desiccant alternatives to fully realize the full cost, efficiency, and productivity benefits.
Cooling systems that use liquid desiccant help the rest of the building to become more efficient and comfortable as well. When humidity levels are low, buildings can achieve greater efficiency by using chilled beams, increasing chiller temperatures, or running higher air temperatures.
By pairing traditional heat pumps that excel at reducing temperature, with liquid desiccant technology that can efficiently handle the humidity, the newest modern air conditioning systems can address the needs of contemporary buildings and support the health of our planet. Working to bring together the knowledge, value and solutions from the past with new ideas for the future, we can achieve a future where A/C continues to “just work” both to cool our buildings and to lessen its impact on our planet.
About the Author:
Aaron Meles, Vice President of Product, Mojave Energy Systems
Aaron is an engineering and product development leader with more than a decade of experience bringing clean energy and environmentally friendly commercial solutions to market. His technical and operational leadership has been applied to gas turbine combustion, distributed control systems for power generation, fuel cells, HVAC, and industrial equipment. Prior to joining Mojave Energy Systems, Aaron held engineering, manufacturing, and product development roles at a range of organizations dedicated to developing cleantech energy-efficient solutions designed to reduce the impact on climate. Aaron graduated summa cum laude with his B.S. in mechanical engineering from Rose-Hulman Institute of Technology and received his M.S.M.E. from the University of North Florida, where his research focused on direct methanol fuel cells for military applications.