WO2020255154A1

WO2020255154A1 - Eeco2r (energy efficiency by carbon dioxide remover) system for centrally cooled building

Info

Publication number: WO2020255154A1
Application number: PCT/IN2020/000010
Authority: WO
Inventors: Swaminathan JAYASEELAN
Original assignee: Jayaseelan Swaminathan
Priority date: 2019-06-17
Filing date: 2020-03-10
Publication date: 2020-12-24

Abstract

The present invention system provides excellent energy efficiency in centrally air conditioned system by removing the carbon dioxide and volatile organic compounds which is existing in the used indoor cooled air. The invention is developing a process to take Cold Air from building and remove the Carbon Dioxide and return the cold air back to the building thereby reducing the amount of fresh air intake Once carbon dioxide and volatile organic compounds removed from the exaust cold air; it will mix into the hot fresh air inlet. This low temperature air will mix with the hot atmospheric air drawn from inlet again and gives fast cooling. This will reduce the energy consumption drastically. The current Building Cooling System brings in Hot Fresh Air after cooling and vent the Carbon Dioxide Rich Cold Air. The Indoor Air quality is maintained to international standards and at the same time the excess energy spent for cooling fresh air and condensing water from fresh air is considerably reduced. The energy spent is to draw the fresh air cool it, only to dilute the carbon dioxide generated inside the building mainly due to human breathing. By this invention, the indoor air is treated to maintain the quality and considerably reducing the intake of fresh air.

Description

EECO2R (Energy Efficiency by Carbon Dioxide Remover) system for Centrally Cooled Building

DESCRIPTION:

[0001] Energy Conservation in Centrally Cooled Building by specific removal of Carbon Dioxide & Volatile Organic Compounds by recycling the Indoor Air and reduce the humid fresh air inlet to the building. The building cooling system has an Air Handling unit which draws fresh air and vents the indoor air. While the cold air is vented simply, hot humid fresh air is cooled by chilled water to maintain the building temperature.

[0002] The new invention is to draw the cold air from the vent system, treat the same for removal of carbon dioxide and send it back to the building through the fresh air intake unit Using this method, the total amount of hot/humid air ingress to the building is brought to bare minimum and hence significant energy saving.

FIELD OF INVENTION:

[0003] The present invention belongs to the field of air conditioning power management technology, and more particularly removing carbon dioxide and volatile organic compounds present in tile indoor air and recycle the cold air by mixing with air intake of air conditioning system to reduce the overall energy consumption smartly.

The conventional central cooling system consists of three major components.

[0004] Chiller System - This system maintains a chilled water circuit for tile entire building. The warm water received from air handling units and fan coil units are chilled by a refrigerant chiller system and sent back for continuous circulation.

[0005] Air Handling Units - This unit serves the purpose of venting the carbon dioxide contaminated internal air and brings in the fresh air. The cold contaminated air is collected from various parts of the building and vented out while the fresh air is drawn from the atmosphere, cooled and sent to various parts of the building. The Chilled water is used to cool the fresh air.

[0006] Fan Coil Units - These are the smaller circulation units within the parts of buildings for local circulations. This unit draws air from the local room and mixes it with the portion of fresh air and cools it down to the required temperature as desired in the thermostat setting.

[0007] Loss of Energy- Areas

There are many areas the energy is lost in the conventional cooling system. The significant areas are briefed as below.

[0008] No Management - In most of the buildings, there is no optimization of the Cooling System in total with reference to the internal air quality as specified in international standards like ASHRAE / AEE The Cooling Systems are designed for maximum occupancy load and installed. They are not operated as per the actual load and hence operated mostly on full load. This leads to wastage of considerable energy

[0009] Cold Air Vent - The cold internal air already consumed lots of energy but vented out to dilute Carbon Dioxide. This is a wastage of Energy

[0010] Fresh Air Cooling - Since the buildings are designed with a higher factor of safety, lots of fresh air is drawn in and cooled with chilled water. This also consumes lots of energy during summer.

[0011] Humidity - During summer when humidity levels are high, energy is consumed in excess to condense the humidity in air handling units as well as fan coil units by using chilled water. Apart from wastage of energy for condensing humidity, the fresh air entering after getting cooled is still having high humidity resulting in discomfort.

[0012] Indoor temperature - When humidity is higher in indoor air, occupants will feel warmer and sultry. In such cases, it is the tendency of occupants to reduce the setpoint in thermostat to feel more comfortable. Reduction of every degree in setpoint consumes more energy but this is not really due to temperature but due to humidity.

[0013] CO₂ generation rates in a building

The CO₂ generation depends on the occupancy rate in the building.

CO₂ generated per person per day ~ 1 kg

During the design of the building, the occupancy rates arc assumed and the building is designed. Hence there is no specific graph that can be provided

During a Field Survey, the level of CO₂ will be measured and plotted for 24 hours to identify the exact generation rate

[0014] CO₂ removal design basis

Following calculation explain how the Fresh Air and Treated Air ratios are calculated. CO₂ balancing to maintain IAQ inside building with fresh air

CO₂ in inlet air 400 ppm

CO₂ inside building 900 ppm

CO₂ generation rate 200 ppm per hour (considered)

Consider Air volume l m³

Fresh Air requirement to dilute 28.5%

[0015] CO₂ balancing to maintain IAQ inside building with treated air

CO₂ in inlet air 40 ppm

CO₂ inside building 900 ppm.

CO₂ generation rate 200 ppm per hour (considered)

Consider Air volume l m³

Treated Air to recirculate 18.8%

Since the CO₂ generation is not uniform in the building across 24 hours, the requirement of Treated Air will dropdown.

[0016] EECO2R capacity sizing

Based on the sample calculation the capacity of EECO2R will be calculated for every building. Also, designs are varying from building to building. Certainly, large buildings are with only one AHU whereas some smaller building has more than one AHU. Sizing is done based on the overall building size and the capacities of AHUs. [0017] Energy Balance in EECO2R package

Since EECO2R is in continuous operation, the CO₂ inside the building may drop down even below atmospheric value. The aim of EECO2R is not to reduce the CO2 to a lower level but to maintain a specified level. Hence EECO2R will not be operated at 100% load at all times. By this way, the energy consumed by EECO2R will also be optimized and conserved.

Significance of the new invention

[0018] Significant Energy Saving - Compared to all available conventional methods, the invention does significant measurable energy saving and hence more attractive for any of the building owner to invest and implement

[0019] Lesser Cost - The cost of implementation of the invention is lesser when compared to conventional and available methods.

[0020] Shorter Pay Back - In all Energy-Saving Project, the PayBack is very important and key deciding factor. Due to a combination of the factors mentioned in (a) and (b) above, the PayBack is very shorter say 18 to 24 months. For larger building, the PayBack can be even 12 months. This is a very attractive proposal and even a Simple Pay Back is more than adequate and reduces tire risks of inflation, a market slow down, etc.

[0021] SUMMARY OF THE INVENTION:

The building cooling system has an Air Handling unit which draws fresh air and vents the indoor air. While the cold air is vented simply, hot humid fresh air is cooled by chilled water to maintain the building temperature. The new invention is to draw the cold air from the vent system, treat the same for removal of carbon dioxide and send it back to the building through the fresh air intake unit. Using this method, the total amount of hot/humid air ingress to the building is brought to bare minimum and hence significant energy saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure - 1: Conventional Central Cooling System

Legends: Floor (1), False roof (2), Living / working area (3), False roof area (4), Fan Coil Unit (5), Fresh Air Handling Unit (6), Fresh Air Fan (7), Vent Air Fan (8), Fresh Air Duct (9), Vent Air Duct (10), Chiller unit (1 1), Chilled Water Supply (12), Chilled Water Return (13), Terrace (14). The system consists of three major systems namely Chiller System, Fresh Air Handling System (FAHU) and Fan Coils System (FCU)

[0023] Chiller System (11) : The purpose of this unit is to cool in the inside ambiance of the building and to maintain inside temperature at about 25 °C even when the outside temperature is about 45 °C. This unit provides Chilled water to the buildings to cool the fresh air in AHU and also cool the re-circulated air in FCUs. This Chilled water system receives warm water through chilled water return pipes (13) at about 15 °C from AHU and FCUs and Chill it to about 7 °C using a Refrigeration Compressor System and supplied through chilled water supply pipes (12). This system provides Chilled water in bulk quantity and it is circulated throughout the building as explained in Figure - 1.

[0024] Fresh Air Handling Units (6) : The purpose of this unit is to provide Fresh air into the building and vent the contaminated air inside the building. The contamination is mainly due to the emission of CO₂ by human breathing and the standards like ASHRAE defines the limit of CO₂ inside the building. During the operation of the building, CO₂ inside the building continues to increase inside the building and it is diluted by pumping in Fresh Air through Fresh Air Ducts (9) and venting the contained air through Vent Air Ducts (10).

[0025] This unit consists of two subunits one for drawing fresh air from the atmosphere and pump it into the building using Fresh Air Fan (7) and the other one extract air from building and vent to the atmosphere using Vent Air Fan (8). For both the purposes, there are independent fans doing the air pumping. In general, the cold air drawn from the building is simply vented out In the recent units, there is a heat wheel installed to draw some amount of chillness from the cold vent air but it does negligible energy saving.

[0026] In order to cool the Fresh Air, there is a cooling coil inside the Air Duct in which Chilled Water is circulated continuously using chilled water piping (12) & (13). During the hot summer period when there is higher humidity, the fresh air gets saturated while getting cooled and a lot of moisture is condensed and it is constantly drained out.

[0027] This condensation is an allied effect of air cooling and consumes lots of energy from Chilled Water. Also due to a layer of water over the cooling coil reduces the efficiency of cooling the fresh air. Most of the time, the Fresh air leaving FAHU to the building is warmer than designed levels, due to this condensation effect and also the air is saturated with humidity.

[0028] Fan Coil Unit (5) : This unit is installed in the False Ceiling area (4) of the building. The purpose of this unit is to do a closed circulation of air inside the living / operating area (3) of the building. The air is drawn from the open area inside the building and mixed with fresh air coming from FAHU, cooled using Chilled Water through chilled water piping (12) & (13) and then sent back to the living / operating area (3). The ratio of Fresh Air and Recirculated Air is fixed by means of a vane/damper in FCU at the time of installation and commissioning.

[0029] Normally during the operation, the ratio of mixing is not altered. Since the incoming Fresh Air from FAHU is already saturated, when it is mixed and cooled, the moisture is condensed again and drained ouL During summer, the condensation and dripping are even noticed in the living / operating area (3) by occupants. Also it results in water accumulation in False Ceiling Area (4) causing damages to False Ceiling.

[0030] Normally the thermostat set in the building wherein the required temperature is set by occupants, increases the air circulation rate in FCU more and more. This means more air needs to be cooled and sent back to the living / operating area. [0031] From the energy consumption point of view, the following ate the key parameters that consume more energy.

[0032] The humidity level: Normally when the humidity level is higher than 45% ~ 50%, the environment will be felt warmer. This means, if the humidity inside the building is 60%, then occupants will feel warmer than the set temperature. For example, if the temperature is set at 25 °C and humidity is 65%, occupants will feel the temperature as 28 °C.

[0033] This will develop the tendency by occupants to reduce the setpoint in thermostat to 20 °C to feel comfortable as 25 °C. This phenomenon can also be seen in an open atmosphere like the coastal area where the humidity is higher, people feel sultry and warmer than the actual temperature. Currently, even the websites provide information of“temperature” and“Real Feel" /“Feels Like" as two parameters.

[0034] In an enclosed atmosphere like centrally air-conditioned building, humidity plays an important parameter to establish the comfort level. And in general, the tendency of lowering set point in thermostat increases energy consumption since more chilled water is required.

[0035] CO₂ in Indoor Air: The CO₂ in atmospheric air is about 400 ppm. In a closed building, the CO₂ continues to increase by human breathing. Every human emits approximately 1 kg of CO₂ every day. This means the concentration of CO₂ increases inside the building continuously. The maximum limit of CO₂ permitted inside the building is about 1000 ppm by international standards like ASHRAE.

[0036] To bring down the level of CO₂, fresh air is pumped in and the contaminated air is vented out on a continuous basis. The volume of Fresh air that needs to be pumped in arrives at the design stage for the maximum occupancy level and FAHU continues to operate at design load. In practical a building is not occupied at design levels and it varies during a day, a week, etc. For example, in a commercial office building, the occupancy level is more in the day time and very less or nil in the night time and same way varies between weekday and weekend [0037] Hence the generation of COi inside the building is not constant and more in the day time and less in the night time. But the FAHU or Chiller is not optimized and operate continuously. This means when CO₂ inside the building is less, say 600 ppm and FAHU continues to operate at full load means, more energy is spent than what is required by both FAHU and Chiller.

[0038] The international organizations like Association of Energy Efficiency (AEE) specify that CO₂ concentration inside the building can be maintained even at the maximum level of 1000 ppm to bring down the energy consumption, but in practice, it does not adhere in almost all the buildings. Hence the wastage of energy is very high when more Fresh Air is pumped in than what is the minimum required.

[0039] Figure - 2: Fresh Air Handling Unit - Detailed

Legends: Vent air duct from Building (1), Fresh air duct to building (2), Silencer (3), Vent air fan (4), Fresh air fen (5), Damper (6), Bag filter (7), Heat wheel (8), Chilled water inlet (9), Chilled water outlet (10), Vent air to atmosphere (11), Vent air from atmosphere (12).

The drawing is a more detailed and appropriate representation of an FAHU.

Both the Fresh Air and Vent air units are combined in one enclosure in two independent chambers to avoid any mix-up. Fresh Air is drawn through a filter assembly to avoid any dust and solid particles. A Vane / Damper controls the flow of air by opening or closing.

[0040] The Fresh Air from atmosphere is drawn in, filtered using inlet filter (7) tol filter any solid dust particles and then passes through a cooling coil wherein Chilled Water is circulated continuously through inlet (9) and outlet (10). The condensed moisture is drained out continuously by a drain pipe. The cold air is then pushed inside the building by a Fresh Air Fan (5) and the fresh air passes through the Fresh Air duct (2) and reaches various FCU's in the building. Vent air collected from various parts of the building and sent to FAHU through the Vent Air Duct (1). The collected vent air is then pushed out to the atmosphere by Vent Air Fan (4). Dampers (6) control the flow of air. [0041] In the latest FAHUs, a heat wheel (8) is introduced in between tile fresh air and vent air chambers. When the wheel rotates slowly, it gets cooled by vent air and when the cold parts reach the fresh air section, the fen cools the fresh air. However practically it does not reduce the energy consumption to a large extent as the wheel rotates very slowly and at a higher airflow rate, most of the energy is lost in vent air. There are. silencers (3) attached to both ducts to dampen the sound due to high air velocity

[0042] During normal operation, the Fresh Air filter (7) gets choked frequently due to the dusty atmosphere, especially at higher humidity levels. It also breaks down frequently. In terms of Energy consumption, the highest energy consumed is during moisture condensation.

[0043] Figure - 3: Proposed EECO2R system in FAHU

Legends: Vent air duct from Building (1), Fresh air duct to building (2), Silencer (3), Vent air fan (4), Fresh air fan (5), Vent air draw of Duct / Pipe (6), EECO2R Package (7), Treated CO2 free air supply Duct / Pipe (8), Vent air to atmosphere (9), Fresh air from atmosphere (10), Fresh Air Handling Unit (FAHU) (1 1).

EECO2R is the Energy Efficiency improvement package by means of removal of CO₂ and VOC in contaminated indoor air and this is an add-on package developed to be attached in FAHU. The cold Vent Air is drawn through a small duct or pipe (6) from the Vent Air duct (1) and passed through the EECO2R (7) and the CO₂ free air is then passed thorough a duct or pipe (8) and let into the Fresh Air duct (2). In this process, venting of cold Fresh Air is avoided and intake of Fresh Air is minimized to the lowest or even nullified. The EECO2R treated Fresh Air has almost ZERO ppm of CO₂ and hence the required treatment capacity in terms of airflow rate is 1/400 times of Fresh Air intake. All remaining items like Silencers (3), Fresh Air Fan (5), Vent Air Fan (4), Fresh Air inlet (10) and Vent Air outlet (9) are retained in FAHU (11) to take care of any emergency situation [0044] Figure - 4 Flow Diagram of EECO2R

Legends: Vent air duct from Building (1), Fresh air duct to building (2), Silencer (3), Vent air fan (4), Fresh air fan (5), Vent air draw of Duct / Pipe (6), EECO2R Package (7), Treated CO2 free air supply Duct / Pipe (8), CO2 Rich vent air (9).

Vent Air Pre-Processing Unit (1):

The air is drawn from the Vent Air Duct by modification in the vent air duct and drawn through a duct or pipe (6). Vent air is then compressed using an air compressor to a higher pressure. The pressure can vary from 4 bar(g) to 18 bar(g). The design of pressure depends on the capacity and physical size available at site near FAHU and the size of other systems. The capacity of Air compressor in m³/h depends on the size of the building and number of FAHUs. in the building.

[0045] Compressed air is then chilled in a Heat exchanger using chilled water from central chiller plant The design of heat exchanger shall be based on the operating parameters pressure and temperature. The incoming Vent Air passes through the first pre-processing stage wherein it is filtered for dust, contaminants, etc. and upgrading to a process parameter suitable for CO₂ filtration.

CQz / VOC Filtertion Unit (2) & (3)

[0046] The pre-processed air then passes through two one of the two filters (2) and (3) wherein CO₂ is filtered and the clean Treated Air comes out and then collected in the collection unit (4). The Treated Air is then passed through a conditioning and delivery unit (5) which converts the air physical conditions are changed to Indoor Air level and then passed through a duct or pipe (8) to the Fresh Air Duct.

[0047] The CO₂ removal/filtration unit is a self-regenerating type and is fitted with instruments to monitor the amount of CO₂ accumulated inside and after reaching the saturation limits, it will isolate automatically and purge out all the CO₂ to the atmosphere (7). Once the CO₂ is all let out and cleaned, it is ready for further CO₂ filtration. To cater to this regeneration process, there are two identical CO₂ filtration units (2) and (3) are provided so that the CO₂ removal process is always a continuous process. This means if Filter (2) is in operation Filter (3) will be regenerated and kept as standby and once Filter (2) is exhausted, they will be swaped.

[0048] Figure - S: Operational Procedure of EECO2R

Legends: Vent air duct from Building (1), Fresh air duct to building (2), Silencer (3), Vent air fan— Slow running (4), Fresh air fan - Switched off (5), Vent air draw of Duct / Pipe (6), EECO2R Package (7), Treated CO2 free air supply Duct / Pipe (8), Vent air to Damper closed (9), Fresh air from atmosphere minimum (10), Fresh Air Handling Unit (FAHU) (11), Fresh air damper minimum open (12).

The vent air fan (4) will be operated but at low speed to draw air from the building. But the outlet damper (9) shall be closed so that the vent air is automatically diverted to EECO2R. The Fresh Air Damper (13) is also closed fully or kept at minimum open for a small make up (10) if required. Fresh Air fan (S) shall be switched off. The Vent air from Vent Air Duct (1) is diverted through duct or pipe (6) shall pass through EECO2R (7) and Treated Air is pumped back through a duct or pipe (8) to Fresh Air Duct (2).

[0049] The delivery from EECO2R (7) will have some residual velocity so that it will reach the building as if it is pumped through Fresh Air fan (5). Since EECO2R has necessary standby for continuous operation and this would continuously operate and supply necessary treated Air to the building.

[0050] Figure - 6: Control Procedure of EECO2R

Legends: Vent air duct from Building (1), Fresh air duct to building (2), Silencer (3), Vent air fan - Slow running (4), Fresh air fan - Switched off (5), Vent air draw of Duct / Pipe (6), EECO2R Package (7), Treated CO2 free air supply Duct / Pipe (8), Vent air to Damper closed (9), Fresh air from atmosphere minimum (10), Fresh Air Handling Unit (FAHU) (1 1), Fresh air damper minimum open (12), CO2 meter (13), Humidity meter (14), Temperature meter (15). The Vent Air Duct (1) and / or (6) and Treated Air supply Duct / Pipe (8) are provided with instruments to measure the CO₂ concentration (13), Temperature (14), and Humidity (15). This would continuously monitor the values between inlet and outlet of EECO2R (7). The running and regeneration between the two identical CO2 removal units shall be decided automatically when the CO₂ concentration in the Treated Air reaches to the set value. EECO2R load also will come down automatically when the inlet CO₂ concentration in Vent Air is lower, especially during the lean time of building operation. The operating conditions of all other parts shall remain as per Figure - 5.

[0051] Figure - 7: Control and Automation of Building Cooling System

Legends: Floor (1), False roof (2), Living / working area (3), False roof area (4), Fan Coil Unit (5), Fresh Air Handling Unit (6), EECO2R package (7), Building air quality management system (8), Electrical energy meter (9), Air Quality Meters (CO2 / Temp / Humidity) (10), Chiller Unit (11), Chilled_, water supply (12), Chilled water return (13), Terrace (14).

There are currently Building Monitoring and Management Systems (BMS) provided in large buildings. They are predominantly information system about the lighting, FCUs, Chillers, and FAHUs whether running or switched off. Most of the buildings do not have any Air Quality Management System.

[0052] In the proposed system complete Automation is considered towards Building Cooling System, in other words, Air Quality Management System (AQMS) (8). The building will be manually surveyed for the CO₂ levels and critical locations shall be marked. At all critical locations, CO₂ / Humidity meters shall be provided. These meters shall have local display as well as data communication facility to AQMS.

[0053] Individual / Composite meters (10) shall be provided at appropriate locations to measure the parameters like CO₂ / VOC / Humidity / Temperature. SMART type Energy (9) meters shall be provided to the Chiller (11), FAHU (6), FCU (5), and EECO2R (7). These smart type of energy meters shall transmit the Energy consumed on an hourly basis to the AQMS (8). [0054] All the data shall be gathered by AQMS and the programs and control system shall be designed in such a way that the operation of every equipment shall be monitored and controlled automatically. The data collection, setting up of Energy Targets and Performance Indicators shall be similar to ISO 50001 : Energy Management System. This means there will be better automated Energy Management System as per ISO 50001.

[0055] Figure - 8: Piping, Instrumentation and process system

Legends: Air filter (1), Air compressor (2), Heat exchanger (3), Chilled water from central chiller unit (4) (5), CO2 filters (6) (7), Four way valve In and Out (8) (9), Vent valve (10), Electrical heater (1 1), Temperature controller (12), Electrical control (13), Flow switch (14), Control valve (15), Pressure reduction valve (16) (17), Vent (18), Fresh air duct (19)

The air is drawn from the Vent Air Duct by modification in the vent air duct. The incoming Vent Air passes through the first pre-processing stage wherein it is filtered (1) for dust, contaminants, etc. and upgrading to a process parameter suitable for CO₂ filtration Filtered Vent air is then compressed using an air compressor (2) to a higher pressure. The pressure can vary from 4 bar(g) to 18 bar(g). The design of pressure depends on the capacity and physical size of CO2 filters (6) & (7). The capacity of Air compressor in m³/h depends on the size of the building and number of FAHUs. in the building.

[0056] Compressed air is then chilled in a Heat exchanger (3) using chilled water from central chiller plant (4) & (5). The design of heat exchanger (3) shall be based on the operating parameters pressure and temperature.. The compressed and chilled air can either be taken directly to next stage or it can be stored in a Air Vessel which depends on the capacity of EECO2R. This additional storage vessel is required only in case of sudden variation in vent air flow from the building as it can operate as intermediate surge vessel [0057] The pre-processed air then passes through one of the two filters (6) & (7) wherein CO₂ is filtered and the clean Treated Air comes out and then collected in the collection unit which can be a vessel or a small pipe chamber.

[0058] The CO₂ removal/filtration unit is a self-regenerating type and is fitted with instruments to monitor the amount of CO₂ accumulated inside and after reaching the saturation limits, it will isolate automatically and purge by depressurising out all the CO₂ / VOC to the atmosphere. Once the CO₂ is all let out and cleaned, it is ready for further CO₂ filtration. To cater to this regeneration process, there are two identical CO₂ filtration units (6) & (7) provided so that the CO₂ removal process is always a continuous process. The units (6) and (7) are identical. One in operation and other in re-generation and standby. The parallel operation of running / standby is through Four-Way Valve (8) & (9) at inlet and outlet. When (6) is in operation (7) will be in regeneration and standby. When (6) is getting exhausted (7) will come online by changing the Four-Way Valves’ (8) & (9) direction so that (6) will automatically go for regeneration. During Regeneration, first the vessel is depressurised to the atmosphere (18) through vent control valve (10) and then some of Treated CO₂ free air is recycled back after heating in an electrical heater (11) and then passed through the vessel under regeneration. The amount of heated air used for regeneration is controlled by flow meter (14) and a control valve (15) and the temperature of regeneration air is controlled by a temperature controller (12) which controls the electricity supply (13). This regeneration step is continued till the CO₂ level in the purge air is 0 ppm and then heater (11) is switched off and cold air is passed through the bed until the vessel becomes colder. After that the vent valve is closed and the vessel is pressurised and kept ready for running.

[0059] The treated clean air is at high pressure and need to be brought down to ambient level. This is carried out by a pressure reducing station consisting of two stage pressure reduction valves (16) and (17). After pressure reduction and bringing down to a level wherein the air can travel to the building, the treated air is let into Fresh Air Duct (19). DETAILED DESCRIPTION OF THE INVENTION:

[0060] Figure - 9 Invention Part ( CO₂ separation Unit- 6 & 7 of Figure 8) Legends: Diameter (1), Height (2), Compressed air inlet (3), Support for filter media (4), Activated carbon filter (5), Activated alumina (6), Molecular sieve (7), Media escape protection (8)

[0061] CO₂ filters consists of filtering media mainly working on surface adsorption principle. There are three components available for this purpose. The bottom portion consists of Activated Carbon (5) with the next layer being Activated Alumina (6) and the top layer will be Molecular Sieve (7). The purpose of Activated Carbon is to remove any Volatile Organic Compounds (VOC) and also adsorb/filter some of CO2 and moisture.

[0062] The purpose of Activated Alumina is to adsorbs/filter the moisture content to a large extent. This stage is essential to facilitate quicker CO₂ removal. The purpose of Molecular Sieve is to adsorb / filter CO₂ completely from the Air. At the outlet of V- 01 , the air shall be free of CO₂ and humidity.

[0063] In overall, across the height of vessel V-01, the concentration will continue to come down. Since the phenomena depend on the surface area available in all the three components, the bottom portion of every one of the three components will get exhausted first. Slowly the saturation keeps moving upwards and at some point of time, CO₂ will start coming out of V-01. Once it crosses a minimum level of 10 ppm, it is considered as V-01 is exhausted and will be taken for regeneration by changing the operation to V-02.

[0064] During the regeneration, the vessel V-01 is first depressurized by opening CV- 04 and vented to the atmosphere. During depressurization, there will be a high velocity developed and this will remove the VOC, CO2, and moisture considerably. After completion of depressurization, clean hot air at 60 °C from the treated Air Collection Unit will be passed from the top ofV-01 which will heat all the three filter media. [0065] This is done for a short time during which all the adsorbed/filtered CO₂, Moisture and VOC shall be removed and sent to the atmosphere. The regeneration process is complete when it is noticed thal it is no CO₂ in the vent air. After regeneration is complete, the cold treated air is passed through to cool the filter media. After cooling, the CV-04 is closed and V-01 is pressurized and kept ready for operation.

The key design parameters

[0066] The physical available area near the AHUs in the operating building. This area has to accommodate the complete package.

[0067] The operating pressure decides the size of V-01 / 02. Higher the pressure, smaller the vessel. Hence the pressure will be decided based on (a) above. Also higher the pressure better the filtration and lesser regeneration time. But higher the pressure, higher the risk of leakages and toughness in manufacturing. Also, the filter media needs to be stronger to work at higher pressure.

[0068] The surface area / m³ of all the 3 filter media is a having parameter as this decides the amount of CO₂ that can be filtered per hour per m³ of the filter media. Similarly, the porosity of the filter media will decide the ease of flow of air.

[0069] The temperature of the air at the inlet of V-01 is very important. Lower the temperature, better adsorption/filtration. However, two low temperature will result in condensation which is not desirable.

[0070] A higher temperature during regeneration reduces the time of removal of contaminants. However, it takes more time to cool. Optimal temperature is chosen for best energy performance as well as optimal regeneration cycle.

Claims

CLAIM: For the purpose of Energy Saving in a Central Cooling System in a building comprising Central Chilling / VAS / VRV system, wherein Energy is wasted mainly in Air Handling Units (AHU) due to fresh air cooling and condensing the moisture present in tire fresh air, the Cold vent / extract / outlet air polluted by CO2 / VOC shall be the inlet of EECO2R, the processed and treated outlet air of EECO2R, free of CO2 and Humidity shall be mixed suitably with the fresh air supply system with adjustment of damper and sensors to achieve the desired quality of Indoor Air for air conditioning support in order to maintain tire comfort of occupants by means of proper CO2 and humidity levels, specified as Indoor Air Quality in international standards, thereby operating EECO2R by various combination of key parameters arising due to size of the building, installation feasibilities,

1. Operating Pressure - This can vary from 3 bar(g) to 18 bar (g) - The reason is the design of the vessel based on the physical space availability near AHUs in the building.

2. Operating Temperature - The temperature can vary from 10 °C to 30 °C - Lower temperature shall be for smaller vessel at higher pressure. Some times for lower pressure also lower temperature can be considered. This depends on the overall capacity of EECO2R and also cost.

3. Activated Carbon quantity: The quantity depends on the rate of generation of VOC. VOCs are due to many causes like floor cleaners, air fresheners, perfumes, cooking fumes, paints, etc.

4. Activated Alumina quantity: This also depends on the humidity level in the building. The reasons could be higher floating population, cooking operations, laundry operations, internal fountains, etc.

5. Molecular Sieve quantity: This depends on the level of generation of CO₂ in the building due to human occupation, kitchens, etc., A commercial office building generates more CQz in the day time than night time and it is vice-versa for residential building.

6. The ratio of all 3 filter media: Based on the type of building, the ratio of the 3 media in (c), (d) and (e) above will be varying based on the available space, vessel size, operating pressure/temperature, type of building. Each component can vary from 0% to 100% depending on the actual building operating parameters.