Dfr for Air-conditioning at Kp-4

8/18/2019 Dfr for Air-conditioning at Kp-4

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DETAILED FEASIBILITY REPORT

ON THE INSTALLATION OF

GEO-THERMAL HEAT SINK

SYSTEM AT

KNOWLEDGE PARK-IV.


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EXISTING STRUCTURE OF KNOWLEDGE PARK-IV BUILDING WITH B+G+4


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1

2

3

1

2

3

4 Heat Exchange thru Infiltration

Heat Gain from Human

Heat Gain from Electrical Equipments

2-External Heat Gain Heat Gain from Wall

Heat Gain from Window

Heat Gain from Area

Heat Gain from Lighting

DESIGN CONSIDERATIONS

There are several methods available to calculate the cooling load of a commercial building, such as :

1) Total Equivalent Temperature Difference/Time Average (TETD/TA)

2) Cooling Load Temperature Difference/Cooling Load Factor (CLTD/CLF)

3) Transfer Function Method (TFM)

4) Heat Balance (HB) & Radiant Time Series (RTS)

5) Manual J Method for Residential Applications & Manual N for Commercial Buildings: These methods are simplified

versions, jointly developed by Air conditioning contractors of America (ACCA) and the Air conditioning and

Refrigeration Institute (ARI).

These different methods may yield different results for the same input data. This is primarily due to the way; each

method handles the solar effect and building dynamics. But in true sense all the above approaches attempt to consider the

fundamental principle that heat flow rates are not instantaneously converted to loads and heat addition or extraction incident

upon the building do not immediately result in a change in temperature. Thermally heavy buildings can effectively delay the

cooling or heating load for several hours.

Most designers use the TETD and CLTD methods because these methods are simple to use, give component loads

and tend to predict load on conservative side.

For strictly manual cooling loads calculation method, the most practical to use is the CLTD/CLF method.

Here in the cooling load calculation for KNOWLEDGE PARK - IV, we have considered this same method.

1-Internal Heat Gain


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Q = U * A * (CLTD)

Q = HEAT GAINED IN BTU'S

DBT = DRY BULB TEMPERATURE.

U = Thermal transmittance for roof or wall or glass. See 1997 ASHRAE Fundamentals, Chapter 24 or 2001 ASHRAEFundamentals, chapter 25.

A = area of wall or glass calculated from building plans

CLTD = Cooling Load Temperature Difference for roof, wall or glass. Refer 1997 ASHRAE Fundamentals, Chapter 28,

tables 30, 31, 32, 33 and 34.

CLTD correlated = CLTD + (78-tr) + (tm-85)

Design Consideration:

INSIDE TEMPERATURE = 64.4 F or 18 °C

OUTSIDE TEMEPRATURE = 113 F or 45 °C

tr =64.4 F (room temperature)

tm = 88.7 F (mean temperature = (tr+to)/2))

DESIGN CONSIDERATIONS


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TOTAL BUILT-UP AREA = 4390.31 sqft

AIR-CONDITIONING REQUIRED IN THE TOTAL BUILT-UP AREA = 55,995 sqft

CAFETERIA IN TERRACE

OPEN AREA FOR OUTDOOR UNITS APPROX TONNAGE REQUIRED = 48.97

SECOND FLOOR APPROX TONNAGE REQUIRED = 89.77

THIRD FLOOR APPROX TONNAGE REQUIRED = 88.41



FIRST FLOOR APPROX TONNAGE REQUIRED = 85.04


BASEMENT APPROX TONNAGE REQUIRED = 64.78

GROUND FLOOR

PANEL ROOM

APPROX TONNAGE REQUIRED = 57.60



(excluding panel room)


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TOTAL ADDITIONAL AREA = 3110.7 sqft per floor (Approx.)

EXISTING STRUCTURE

ADDITIONAL AREA

HEAT LOAD FOR THIS ADDITIONAL AREA WILL DEPEND UPON INTERNAL SEATING PLAN (EITHER

CABINS OR OPEN AREA INCLUDING WORK STATIONS & CUBICLES)


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CONVENTIONAL HVAC SYSTEM

The Conventional HVAC system used for air conditioning system removes heat from inside

of the building and transfers it to the outside via the condenser to keep your inside

environment cool in the summer. This type of system typically pairs a chiller with a cooling

tower. Like the condenser used in our home’s central AC system, the chiller is a machine

that removes heat from the building. A piped water loop runs through the building, picking

up heat along the way, which is circulated though the chiller to be cooled —in a continuous

loop called the chilled water loop. The heat removed by the chiller is rejected to the

outside through a different piped water loop (called the condenser loop). This condenser

water loop runs through a cooling tower, which uses evaporative cooling to cool this piped

water—typically by 10 degrees Fahrenheit—which is circulated back to the chiller in a

continuous loop.

Evaporative cooling is the same cooling process our body uses, i.e., as perspiration

evaporates, it pulls heat away from our body. Just like the perspiration on our skin, the

evaporated water carries heat and is lost to the atmosphere. This lost water must be addedback into the system, or "made up."


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VRF SYSTEM (VARIABLE REFRIGERENT FLOW SYSTEM)

A split system air-conditioner or heat pump incorporating a single refrigerant circuit, with

one or more outdoor units, at least one variable speed compressor or an alternative

compressor combination for varying the capacity of the system by three or more steps,

multiple indoor fan coil units, each of which is individually metered and individuallycontrolled by a proprietary control device and common communications network. The

system shall be capable of operating either as an air conditioner or a heat pump. Variable

refrigerant flow implies three or more steps of control on common, inter-connecting

piping. One outdoor unit can serve multiple indoor units connected by refrigerant piping.

The systems use R-410A refrigerant, which is applicable for LEED. The combination of the

more efficient refrigerant, variable refrigerant volume, inverter driven compressor, and DC

fan and compressor motors provide high coefficients of performance (COP), even at low

temperatures.

VRFs are typically installed with an Air conditioner inverter which adds a DC inverter to the

compressor in order to support variable motor speed and thus variable refrigerant flow

rather than simply on/off operation. By operating at varying speeds, VRF units work only at

the needed rate allowing for substantial energy savings at partial-load conditions. Heat

recovery VRF technology allows individual indoor units to heat or cool as required, while

the compressor load benefits from the internal heat recovery. Energy savings of up to 55%

are predicted over comparable unitary equipment. This also results in greater control of

the building's interior temperature by the building's occupants.

https://en.wikipedia.org/wiki/Air_conditioner_inverterhttps://en.wikipedia.org/wiki/Inverter_compressorhttps://en.wikipedia.org/wiki/Refrigeranthttps://en.wikipedia.org/wiki/Gas_compressorhttps://en.wikipedia.org/wiki/Gas_compressorhttps://en.wikipedia.org/wiki/Refrigeranthttps://en.wikipedia.org/wiki/Inverter_compressorhttps://en.wikipedia.org/wiki/Air_conditioner_inverter


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BASICALLY, THERE ARE TWO TYPES OF VRF SYSTEMS:

1. AIR SOURCED VRF SYSTEM (AS INSTALLED AT CHI-IV OFFICE OF NPCL)

2. WATER SOURCED VRF SYSTEM

AIR SOURCED VRF SYSTEM -

Air Sourced VRF systems provide heating and cooling by exchanging energy with theambient air, extracting energy from the air (outside atmosphere) in the heating

mode and rejecting energy to the air (outside atmosphere) in the cooling mode.


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SEVERAL VENDORS ARE PRESENT IN THE MARKET WHICH ARE PROFICIENT IN THE

AIR SOURCED VRF TECHNOLOGY LIKE:

1. MITSUBISHI

2. LG ( VRF UNITS INSTALLED AT CHI-IV ARE LG MAKE)

3. DAIKIN

4. TOSHIBA

5. CARRIER

6. TRANE

OUT OF THESE, WE HAVE EARLIER RAISED OUR ENQUIRIES TO:

1. MITSUBISHI

2. LG

3. DAIKIN

WATER SOURCED VRF SYSTEM -

Water-source VRF is similar to air-source VRF on the refrigeration side. Multiple

indoor units can be connected to a compressor module where each module houses

a single inverter driven compressor. The primary difference is the fact that the

compressor module absorbs and rejects heat from or to a water-source heat sink

instead of an air-source heat sink.

Water sourced VRF systems will provide heat recovery between modules connected

to a common hydronic loop. System then absorb or reject heat, from or to the

building hydronic loop.


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VENDORS PRESENT IN THE MARKET WHICH ARE PROFICIENT IN THE WATER SOURCED VRF

TECHNOLOGY LIKE:

1. MITSUBISHI

2. DAIKIN

3. LG

We have not yet raised our formal enquiries for Water Sourced VRF system but asked for

tentative price schedule for water source VRF.

*Water Sourced VRF are 1.5-2 times costlier than Air-Sourced VRF system.


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WHY VRF NOT TRADITIONAL HVAC SYSTEM?

1. ENERGY EFFICIENCY. VRF systems use less energy for several reasons. The system is

designed to provide exactly the amount of cooling needed for the current conditions,

which means it runs less frequently and at a lower capacity. The VRF system is also

designed to capture heat from the cooling process and reuse it in other areas that may

need heating.

2. QUIET OPERATION. In a VRF system, the noisier condensing unit is typically outside, and

the indoor air handlers are smaller and quieter than a traditional split system.

3. HEAT AND COOL SIMULTANEOUSLY (ZONING). The VRF system captures residual heat

absorbed from the air during the cooling process, and redirects that heat to other parts of

the building that need heat.

VRF systems have a unique ability to extract heat out of areas requiring cooling and put it

into zones requiring heating. Recent modelling of a typical medium sized commercial office

building indicated the requirement for simultaneous heating and cooling to be about 1-2 %of the system’s operation.

The need for this feature increases in colder climates & may form up to 10-15% of the

system’s operation. To some extent, differing preferences of occupants for warmer or

cooler workspaces can also result in a demand for simultaneous heating and cooling, which

is normally frowned upon, but can be economically catered for with the VRF system.

Hence, it is possible to create zones where cooling or heating is required at same time and

no cooling or heating when there is no occupancy in a single floor.

The VRF zoning systems by the company permit an indoor unit to be serviced while other

indoor units within the same piping system are still in operation, and the simple controls

networks provide diagnostic information, making maintenance simpler

4. CONSISTENT COMFORT. The VRF system’s compressor can detect the precise

requirements of each zone, and send the precise amount of refrigerant needed to do the

job. As a result, each area of your space is consistently comfortable with well-controlled

humidity and no hot or cold spots.

5. LESS DOWNTIME. Since the VRF system is designed to run only when needed and under

partial-load conditions, there is less wear and tear on the parts. That means fewer

breakdowns. Also, if something goes wrong with one air handler, often the others areunaffected. That means your whole space won’t be without air conditioning all at once.

6. REQUIRES LESS SPACE. Since the air handlers are smaller and VRF systems don’t usually

require ducts, they don’t require as much wall and ceiling space for the equipment. That

means you get to keep those gorgeous high ceilings in your apartment. Ductwork is limited

or not required at all, and the two-pipe system is extremely flexible. Mitsubishi Electric VRF


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zoning systems require only a 3-inch opening in the exterior of a building for the refrigerant

lines and wiring to run through, connecting the indoor units to the outdoor units.

7. MODERN CONTROLS. For residences, you can take advantage of mobile control

technology that lets you adjust temperature settings for each zone from your mobile

device. For commercial settings, the VRF system’s built-in controls may allow you to skip

purchasing expensive building management software.

GEO-THERMAL HEAT SINK SYSTEM -

Commercial buildings that are centrally air-conditioned use an air-cooled or water-cooled

heat exchanger to pump out heat inside the building into the atmosphere. The atmospheric

temperature conditions contribute to the efficiencies of the air-conditioning systems. If the

atmospheric temperatures are higher, efficiency of the air-conditioning system is lower and

vice versa.

Geothermal heat sink system uses the earth as heat sink instead of outside atmosphere in

conventional systems. The earth temperatures in most cases are much lower than theatmospheric temperatures. With the lower temperatures the efficiencies of the air-

conditioning systems are significantly higher.

Geothermal works because the ground beneath our feet is warmer then the outside air in

the winter and cooler in the summer. Inserting a series of small pipes into the ground

allows heat to be transferred to and from enclosed area. In this process heat is not created,

it is transported therefore no fuel is burned.

Summer Operation: The indoor heat pump takes the hot air from the office building and

removes the heat. This leaves behind cool air to be distributed through vents as air-

conditioning. The removed heat from the air is rejected into the earth through the ground

loop. In this case the water is warmer leaving the office area then when it returns since

heat is rejected into it.

Winter Operation: The underground pipes, called a ground loop, circulate water which

absorbs the heat from the earth and returns it to the indoor heat pump. The heat pump

extracts the heat from the liquid then distributes it throughout as warm air. With the heat

removed, the water is re-circulated to collect more heat from the ground. In this case the

loop water is warmer when it comes into the enclosed area than when it goes back into the

earth since the heat is being removed.

There are two primary types of loop systems available for use with geo-exchange /

geothermal systems. These are:


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1. CLOSED-LOOP SYSTEMS

HORIZONTAL

This type of installation is generally most cost-effective for residential installations,

particularly for new construction where sufficient land is available. It requires trenches at

least four feet deep. The most common layouts either use two pipes, one buried at six feet,and the other at four feet, or two pipes placed side-by-side at five feet in the ground in a

two-foot wide trench.

VERTICAL

Large commercial buildings and schools often use vertical systems because the land area

required for horizontal loops would be prohibitive. Vertical loops are also used where the

soil is too shallow for trenching, and they minimize the disturbance to existing landscaping.

For a vertical system, holes (approximately four inches in diameter) are drilled about 20

feet apart and 100 to 400 feet deep. Into these holes go two pipes that are connected at

the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal

pipe (i.e., manifold), placed in trenches, and connected to the heat pump in the building.


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2. OPEN-LOOP SYSTEM - (SYSTEM OFFERED BY GIBBS FOR KP-4)

Actually system is an open loop system but due to the upstream and downstream water

flow beneath aquifers, the system is converted in natural close loop system.


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Combining Two Technologies: Geothermal + VRF Zoning Systems-

Water-source VRF zoning systems combine the efficiency benefits of a geothermal system

with the sophistication of VRF zoning systems. This technology takes advantage of an

INVERTER-driven compressor, coupled with a closed geothermal loop, instead of utilizing

air as a heat exchange medium.


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WATER SOURCED VRF PAIRED WITH CONVENTIONAL COOLING TOWER SYSTEM -


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WATER SOURCED VRF PAIRED WITH GEO-THERMAL HEAT SINK SYSTEM –


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PROS & CONS OF WATER SOURCE VRF ZONING SYSTEM PAIRED WITH GEO-THERMAL SYSTEM:

PROS:

1. Upto 15-20% Energy savings compared to traditional HVAC (Chiller & Cooling

Tower). Energy saving as a result of lower Entering Cooling Water Temperature

(ECWT) in the water sourced VRF since ground offers a much lower temperature

compared to ambient environment.

2. System offered by M/s. GIBBS is not an actual closed loop system but converted into

a Natural Closed loop system using upstream & downstream water flow beneath

aquifers. Hence, does not require any make-up water upto Heat-Exchanger as

compared to traditional HVAC (Chiller & Cooling Towers)

3. Flexible installation - Installation is possible in tight spaces because the two-pipe

design of the VRF system requires less space than ducted systems. Moreover, both

injection field and production field are below ground. Hence, space above ground

can be used for other purposes.

4.

Application variety - Water-source VRF zoning condenser units can be connected to an array of indoor unit styles to accommodate the specific needs of the space. The

configuration of the below-ground loop system can be customized to accommodate

the building’s surroundings.

5. Clean energy source. Water-source VRF zoning systems use the clean and

sustainable energy stored in the earth to cool and heat buildings, a more

environmentally friendly and efficient source of energy than non-renewable fossil

fuels. Reduction in Carbon Footprints by 30%. The combined system can provide

upto 10 LEED points for Green building certification.

6. System efficiency. The INVERTER-driven compressor varies the speed of the motor’s

rotation, allowing it to precisely meet each zone’s load requirement while reducingoverall power consumption. Geothermal VRF zoning systems are also able to take

advantage of stable ground temperatures for even greater efficiencies.

CONS:

1. Earlier we were working on Air-Source VRF unit for whole Knowledge Park-IV building.

Geo-Thermal heat exchange system cannot work with Air-Source VRF system. If we want

to implement Geo-Thermal heat exchange system, we need move from Air-Source VRF

system to Water Source VRF system which is major issue for us. Initial cost of water source

VRF system approximately 2 times that of air source VRF system. Apart from this,

installation and commissioning cost of water source VRF system is 15-20% higher as itincludes additional Piping and Instrumentation job (water circuit).

2. Installing a geothermal system is expensive. The major disadvantage of geothermal

heat pumps is increased upfront initial costs, which are in average two to three times

higher than conventional systems. This really becomes a disadvantage if the system is

not installed properly. Thousands of heating and cooling systems are installed each year

that do not produce the intended energy savings due to improper installation

techniques. The costing will depend on the soil conditions, plot size, system


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configuration, site accessibility and the amount of digging and drilling required. Even so,

a geothermal system will cost about 40 percent more than a traditional HVAC system.

3. Almost 50-60% of the total project cost involves Ground Thermal Analysis, Modeling

and Sensitivity Analysis for the designing of primary and secondary loops. These

processes are done by highly accredited professionals. Hence, sizing, design and

installation require pro-expertise for the most efficient system. There are very few

installers involved in erection and commissioning of water sourced VRF system in

combination with Geo-thermal system with natural closed loop system.

4. Heavy drilling and digging is required on earth surface which is quite a tedious

job. However, vertical installations are typically much more expensive than

horizontal installations because of the cost of drilling several hundred feet

underground.

5. Most of the Water Source VRF units have factory installed stainless steel plate heat

exchangers. In order to protect these heat exchangers, it is recommended to use

closed geothermal water loops. Should open geothermal systems be used, an

intermediate heat exchanger should be installed to isolate VRF units from

contaminants in the water system. Open geothermal loops may contain minerals,

biological contaminants, corrosive agents, or other substances which can cause

scale, fouling or corrosion, that could degrade performance or shorten the life of the

heat exchanger and unit.

Hence, an intermediate heat exchanger will be necessary which will add up extra cost.

6. De-mineralized or RO water will be required as a makeup water for the primary

loop between Water Sourced VRF unit and intermediate heat exchanger. Since, we

are planning to construct Ion-Exchange plant for drinking water supply in the building

with capacity 300-400 LPH. Hence, we have to increase our plant capacity which will

again add up extra cost.


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7. There will be a huge piping and instrumentation job required at both sides (VRF outdoor units as well as Geo-thermal Exchanger side). Hence, a separatemaintenance team including a Mechanical Engineer & Fitter will be required in

each shift as there will be every time occupancy in the building (Central ControlRoom or Load Dispatch Centre) which will again add up extra cost. (Piping &Instrumentation drawing for such a system is shown below in the diagram)

8. One of the reasons to not consider Traditional HVAC system (Chiller & Cooling Tower)

and to consider Air-Sourced VRF system was low maintenance and minimal Piping &Instrumentation (PI) job. Though there will be less maintenance required in Geo-

Thermal system but the same is not true in case of water source VRF coupled with

Geo-Thermal system.

9. There are very less references available in India for Water source VRF system

coupled with Geo-Thermal system. Hence, operational issues or problems are not

known.

10. Almost 10-year payback period. This cost includes extra CAPEX* for installing water

source VRF + Geo-Thermal Heat Sink system. Return of Investment can be achieved

thru OPEX.

Extra CAPEX*

Cost of Air Source VRF system = Rs. X

Cost of Water Source VRF System = Rs. 2X

Cost of Geothermal System = Rs. Y

Total cost of Water Source VRF coupled with Geo-Thermal system = Rs. (2X+Y)

Complete ROI calculation is also available in the next attachment.


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11. Of course Geo-Thermal system is an efficient system leading to energy saving but on the

other hand Air-Source VRF system which is typically installed with an Air conditioner

inverter which adds a DC inverter to the compressor in order to support variable motor

speed and thus variable refrigerant flow rather than simply on/off operation. By operating

at varying speeds, VRF units work only at the needed rate allowing for substantial energy

savings at partial-load conditions. Heat recovery VRF technology allows individual indoor

units to heat or cool as required, while the compressor load benefits from the internal heatrecovery. Energy savings of up to 55% are predicted over comparable unitary equipment

in case of AIR Source VRF.

12. Geo-Thermal system can provide upto 10 LEED points under innovation category for Green

Building Certification. On the other hand, the Air-Sourced VRF systems use R-410A

refrigerant, which is applicable for LEED. The combination of the more efficient refrigerant,

variable refrigerant volume, inverter driven compressor, and DC fan and compressor motors

provide high coefficients of performance (COP), even at low temperatures.

13. While if we talk about only Water source VRF system and not Geo-Thermal system, we are

totally dependent on water for primary loop between VRF unit and intermediate heat

exchanger. If there occurs any sort of obstacle in the primary water circuit then whole Air-Conditioning system will be compromised. While, in case of Air-Source VRF there is no such

requirement of water circuit. Each unit can be separately taken OFFLINE for maintenance

without disturbing existing unit.

14. If we take the reference from recent visit to ISB, Mohali :

They have installed 3 nos. water cooled chillers each of 300 TR. At a time only 2 chillers are

working while 3rd is a standby.

a. Chiller 1 – 300 TR (Heat Exchange done thru Cooling Towers)

b. Chiller 2 – 300 TR (Heat Exchange done thru Cooling Towers)

c. Chiller 3 – 300 TR (Heat Exchange done thru Geo-Thermal Heat Sink System)

Looking at the benefits of only Geo-Thermal system, ISB management can easily dismantle

existing cooling towers and can sync their other 2 chillers with Geo-Thermal system but

they have not done yet.

Of course, M/s. GIBBS makes out a case that they were called for design, engineering,

supply, erection & commissioning of Geo-Thermal Heat Sink system at the very later stage

of the construction of ISB, Mohali project but the fact cannot be denied that ISB facility is

not fully dependent on Geo-Thermal Heat sink system.

Since, Geo-thermal heat sink system technology is new in India, ISB team doesn’t want to

take any sort of risk.

Dfr for Air-conditioning at Kp-4

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