Method and System for Improved-Efficiency Air-Conditioning

Abstract

The amount of supply air used by an HVAC system, and hence the amount of energy used for heating and cooling, while maintaining desirable air quality and composition, is reduced by removing unwanted gases, such as carbon dioxide, using scrubbers or other devices that separate these gases from the circulating air. Optionally, the air can be further improved with injection of concentrated oxygen. While in a normal HVAC system frequent replacement of the building air is performed, scrubbing of CO 2 and other unwanted gases, with or without additional oxygen, would achieve the same goal, but with less frequent air replacement and therefore lower thermal load on the HVAC system.

1 . A system for controlling temperature of air in an enclosed environment, comprising:
 an inlet configured to receive air from outside the enclosed environment;   an air handling unit connected to receive outside air through the inlet and circulated air from the enclosed environment and configured to affect the temperature of the received air;   an air circulation system configured to circulate air from the air handling unit to designated spaces in the enclosed environment and back to the air handling unit;   a gas scrubbing system configured to reduce the level of unwanted gases in the circulating air.   
     
     
         2 . The system of  claim 1 , further comprising a control system responsive to measurements of composition of the circulated air to control the gas scrubbing system to maintain a desired composition of the circulated air. 
     
     
         3 . The system of  claim 2 , wherein airflow through the inlet is such that the desired air composition is maintained with a lower amount of outside air than would be possible without the gas scrubbing system. 
     
     
         4 . The system of  claim 1 , wherein the unwanted gases includes carbon dioxide. 
     
     
         5 . The system of  claim 4 , wherein the unwanted gases further include at least one of volatile organic compounds, carbon monoxide, nitrous oxides and sulfur oxides. 
     
     
         6 . The system of  claim 1 , wherein the gas scrubbing system is connected to the air circulation system to intercept at least a portion of the circulating air prior to the circulating air reaching the air handling unit. 
     
     
         7 . The system of  claim 1 , wherein the gas scrubbing system is connected to the air the air circulation system to intercept at least a portion of the circulating air after the circulating air is processed by the air handling unit. 
     
     
         8 . The system of  claim 1 , wherein the gas scrubbing system includes a molecular sieve and the unwanted gas is reduced by adsorption of the unwanted gas onto the molecular sieve. 
     
     
         9 . The system of  claim 8 , wherein the molecular sieve is made of a form of zeolite. 
     
     
         10 . The system of  claim 8 , wherein the gas scrubbing system includes at least one additional adsorbent. 
     
     
         11 . The system of  claim 10 , wherein the additional absorbent includes at least one of activated charcoal, silica gel or porous alumina. 
     
     
         12 . The system of  claim 10 , wherein the additional adsorbent is placed in a bed that intercepts flow of circulating air. 
     
     
         13 . The system of  claim 10 , wherein the gas scrubbing system comprises a plurality of beds, wherein each bed intercepts flow of circulating air, and each bed includes an additional adsorbent. 
     
     
         14 . The system of  claim 1 , wherein the gas scrubbing system comprises a system for controlling a reversible chemical reaction. 
     
     
         15 . The system of  claim 14 , wherein the reversible chemical reaction is a sodium carbonate and sodium bicarbonate cycle. 
     
     
         16 . The system of  claim 14 , wherein the reversible chemical reaction is an amine-gas cycle. 
     
     
         17 . The system of  claim 1 , where the gas scrubbing system utilizes one or more bases. 
     
     
         18 . The system of  claim 17 , wherein the base is an alkaline hydroxide. 
     
     
         19 . The system of  claim 1 , wherein the gas scrubbing system is a temperature swing adsorption system. 
     
     
         20 . The system of  claim 1 , wherein the gas scrubbing system includes a purge cycle, wherein a purge gas is applied to the gas scrubbing system to release the unwanted gas from the gas scrubbing system. 
     
     
         21 . The system of  claim 20 , wherein the purge gas is heated by taking heat from a component of a heating, ventilation and air-conditioning system incorporating the air circulation system. 
     
     
         22 . The system of  claim 20 , further comprising a heating system configured to heat the purge gas. 
     
     
         23 . The system of  claim 22 , wherein the heating system uses solar energy. 
     
     
         24 . The system of  claim 1 , wherein the gas scrubbing system comprises an adsorbent, and the system further comprises a cooling system that cools the adsorbent, wherein the cooling system uses a chilled fluid provided by the air handling unit. 
     
     
         25 . The system of  claim 1 , wherein the gas scrubbing system is connected to the air circulation system such that a part of circulating air flows through the gas scrubbing system and another part of the circulating air bypasses the gas scrubbing system. 
     
     
         26 . The system of  claim 1 , further comprising an oxygen injection system that injects oxygen concentrated air into the circulating air. 
     
     
         27 . The system of  claim 26 , further comprising a control system responsive to measurements of oxygen level in the circulating air to control the oxygen injection system so as to maintain a desired level of oxygen in the circulating air. 
     
     
         28 . The system in  claim 26 , wherein the oxygen injection system comprises a pressure swing adsorption or vacuum swing adsorption system. 
     
     
         29 . A process for controlling temperature of air in an enclosed environment, comprising:
 receiving air from outside the enclosed environment and circulating air from the enclosed environment;   conditioning the received air so as to provide air at a desired temperature;   circulating the conditioned air into and from designated spaces in the enclosed environment;   scrubbing the circulated air from the enclosed environment to reduce unwanted gases in the circulated air;   recirculating the scrubbed air; and   exhausting a portion of the circulated air from the enclosed environment.   
     
     
         30 . The process of  claim 29 , wherein the scrubbed air is conditioned to the desired temperature prior to being recirculated. 
     
     
         31 . A control system for use with an HVAC system having a gas scrubbing system for removal of an unwanted gas from circulated air, the control system comprising:
 a sensor for determining an amount of the unwanted gas in the circulated air;   a controller that modifies a rate of exhaust of circulating air and intake of outside air so as to adjust overall air replacement according to the measured amount of unwanted gas in the circulated air.