Calculation sheet

Project vv

Project Consultant vvv

Client vv

Contractor vv

Subject Proposal for Energy Recovery Wheel with life cycle cost analysis

Location vv

Design By vv

Energy Recovery Wheel (ERW) calculation

Air flow data for energy recovery wheel

Out door air dry bulb temperature 32 ⁰C

Out door air RH 80 %

Toilet exhaust air temperature 25 ⁰C

Toilet exhaust air RH 50 %

Block 06

Enerdy recovery wheel 01 l/s Pa

Toilet exhaust air flow rate / external static pressure 3175 335

Supply air flow rate / external static pressure 5467 300

Enerdy recovery wheel 02

Toilet exhaust air flow rate / external static pressure 2740 365

Supply air flow rate / external static pressure 6338 300

Data from the selection sheet

Without ERW With ERW

Power of AHU riser 01 OA fan 5.50 kW Power S/A fan of ERW 01 8.96 kW

Power of AHU riser 02 OA fan 7.50 kW Power E/A fan of ERW 01 5.69 kW

Toilet exhaust riser 01 4.00 kW Power S/A fan of ERW 02 4.89 kW

Toilet exhaust riser 02 4.00 kW Power E/A fan of ERW 02 10.96 kW

Power Rotor drive motor ERW 01 0.18 kW

Toilet Toilet exhaust

Out door Supply

T1=DBT= 25 ⁰CRH1 = 50 %

T3=DBT= 32 ⁰C

T2=DBTRH2

T4=DBTRH4Q4

Calculation sheet

Power Rotor drive motor ERW 02 0.18 kW

ERW No 01 thermal energy saving 116 kWh

ERW No 02 thermal energy saving 100 kWh

Assumptions/ conditions:

1. Energy savings of individual equipments due to ERW are not considered

2. COP of the chiller (from the employer's requirement of the tendeder document) 5 COP = refrigerent effect in kW / input in kW

3. Thermal load saving due to ERW is equal to the thermal load saving of chillers

4. Electricity cost due to maximum demand is not considered

5. Electricity charge Unit charge Fixed charge

14.55 kW/kWh 3000 LKR/month

6. Working hours : 8 working hours per day

: 20 working days per month

: 12 months per year

7. Sensible effectiveness (εsensible) 0.7 for the calculation according to the AHRI guide line

8. Latent effectiveness (εsensible) 0.7 for the calculation according to the AHRI guide line

9. Air density, Specific heat (Cp) & humidity (from Data generated from the software developed by S.A.Klein and F.L.Alvarado.)

TemperatureDensity

Specific

Heat

t   ρ  cp

( o C) (kg/m 3 ) (kJ/(kg K)) ρ (kg/m3)

cp (kJ/(kg

K))

w (from

psychrome

tric chart)

20 1.204 1.007 t1 1.278 1.1564 0.0244

25 1.184 1.007 t3 1.184 1.007 0.0099

30 1.164 1.007

35 1.145 1.007

10. hfg 2501000 J/kg

11. Depreciation Allowance for Plant & Machinery (x) 30% Budget Highlights 2015 by SJMS ASSOCIATES

12. Descount rate (r) 10%

13. Electric differential escalation (z) 10%

Calculation sheet

Calculations

Calculation according to AHRI standard

ERW 01 ERW 02

Mass flow rate entering exhaust air me 3.76 3.27 kg/s

Mass flow rate supply air ms 3.76 3.27 kg/s

ERW 01 ERW 02

Sensible energy recovered (kW) Qsensible = ε sensible x m min x Cp (t1-t3) 21.30 18.56

Latent energy recovered (kW) Qlatent = ε latent x m min x hfg (w1-w3) 95.43 83.13

Total energy recovered (kW) Qtotal= Qsensible + Qlatent 116.73 101.69

- When recovered energy is considered, there is a little difference between product selection data and results of the calculation done according to the

AHRI guideline V -2011. Because actual effectivenesses of the product vary from 0.7.

- Technical data (power consumptions and pressure drops) for fans, and energy recovery wheels are taken from a manufacture's data of a ERWs system

(DRI ecofresh ERW) which fulfil our requirement.

Total thermal energy saving 218.42 kWh From the calculations done accrording to the AHRI guide lines

Electrical energy saving due to thermal energy saving (ES,ERW) 43.68 kWh ES,ERW = (Thermal energy saving / COP) x 1 hour

Total operating energy

Without an ERW system With an ERW system

E T = E0 + E FASF + E TEF E T,ERW = (E0 - ES,ERW) + E SAF + E EAF + E ERW

Where

E T : Total operating energy without an ERW system

E0 : Operating energy of all the equipment except fresh air supply fans and toilet exhaust fans

E FASF : Operating energy of Fresh air supply fans

E TEF : Operating energy of Toilet exhaust fans

E T,ERW : Total operating energy with an ERW system

E1 : Operating energy of all the equipment except supply fans and exhaust fans

E SAF : Operating energy of supply air fans

Calculation sheet

E EAF : Operating energy of exhaust air fans

E ERW : Operating energy recovery wheel

Total electrical energy saving per hour {ET - E T,ERW = E0 + E FASF + E TEF - [(E0 - ES,ERW) + E SAF + E EAF + E ERW]}

33.83 kWh

Total electrical energy saving per year 64,959.66 kWh

Total electrical energy cost saving per year 981,163.12 LKR/year

Life cycle cost analysis

Capital cost for the system without ERW = Cost for supply and installation of all the equipments except FASF & TEF + Supply and istallation cost of FASF &

TEF(without ERW) + supply and installation of ducting

Capital cost for the system with ERW = Cost for supply and installation of all the equipments except ERW complete with fans + Supply and istallation cost of

ERW complete with fans + supply and installation of ducting

In above two costs, first terms of right hand side are equal.

Therefore gross capital cost for the ERW = Supply and istallation cost of ERW complter with fans - Supply and istallation cost of FASF & TEF

Supply and installation cost for FASF & TEF - if there is no ERW + ducting ########## LKR

Supply and istallation cost for ERW complete with fans and ducting ########## LKR

Therefore gross capital cost for the ERW 842,720.63 LKR

Without

ERW

ERW 01 ERW 02

Fans operating cost per year

Supply fan operating cost 250,222.75 136,467.36 363,168.00

Exhaust fan operating cost 159,067.58 306,038.88 223,488.00

Motor of rotery wheel operating cost 5,028.48 5,028.48

Total electricity cost per year Operating cost per year due to ERW system

Maintenance cost per year 30,000.00 30,000.00

With ERW system

311,197.54

Calculation sheet

Des

crip

tio

n

Dis

cou

nte

d P

V

(a)

Dis

cou

nte

d r

esid

ual

valu

e

(b=P

V o

f a(

1-x

)^n

)

Mai

nte

nan

ce c

ost

(c=c

1(1

+r)^

n)

Dis

cou

nte

d P

V

(d=c

/(1

+r)^

n)

Elec

tric

ity

cost

( e=

q(1

+z)^

n)

Dis

cou

nte

d P

V

(f=e

/(1

+r)^

n)

Tota

l co

sts

(g=c

+e)

Dis

cou

nte

d P

V

(h

=d+f

)

Dis

cou

nte

d

cum

ula

tive

co

sts

(i)

An

nu

al S

avin

g d

ue

to

reco

very

(j)

Gro

ss s

avin

g

(k=j

-e)

Dis

cou

nte

d t

ota

l

savi

ng

(l=k

/(1

+r)^

n)

Dis

cou

nte

d

cum

ula

tive

sav

ing

(m)

0 Initial value 842,720.63 842,720.63 842,720.63 842,720.63 0.00 842,720.63

1 536,276.76 66,000.00 60,000.00 342,317.29 311,197.54 408,317.29 371,197.54 1,213,918.16 1,381,996.72 1,039,679.43 945,163.12 945,163.12 (267,521.72)

2 341,267.03 72,600.00 60,000.00 376,549.02 311,197.54 449,149.02 371,197.54 1,585,115.70 1,520,196.39 1,143,647.37 945,163.12 1,890,326.23 (646,477.57)

3 217,169.93 79,860.00 60,000.00 414,203.92 311,197.54 494,063.92 371,197.54 1,956,313.24 1,672,216.03 1,258,012.11 945,163.12 2,835,489.35 (1,096,346.04)

4 138,199.05 87,846.00 60,000.00 455,624.31 311,197.54 543,470.31 371,197.54 2,327,510.77 1,839,437.63 1,383,813.32 945,163.12 3,780,652.47 (1,591,340.74)

5 87,944.85 96,630.60 60,000.00 501,186.74 311,197.54 597,817.34 371,197.54 2,698,708.31 2,023,381.40 1,522,194.65 945,163.12 4,725,815.59 (2,115,052.13)

6 55,964.90 106,293.66 60,000.00 551,305.42 311,197.54 657,599.08 371,197.54 3,069,905.84 2,225,719.54 1,674,414.12 945,163.12 5,670,978.70 (2,657,037.76)

7 35,614.03 116,923.03 60,000.00 606,435.96 311,197.54 723,358.99 371,197.54 3,441,103.38 2,448,291.49 1,841,855.53 945,163.12 6,616,141.82 (3,210,652.47)

8 22,663.47 128,615.33 60,000.00 667,079.56 311,197.54 795,694.88 371,197.54 3,812,300.92 2,693,120.64 2,026,041.08 945,163.12 7,561,304.94 (3,771,667.50)

9 14,422.21 141,476.86 60,000.00 733,787.51 311,197.54 875,264.37 371,197.54 4,183,498.45 2,962,432.70 2,228,645.19 945,163.12 8,506,468.06 (4,337,391.81)

10 9,177.77 155,624.55 60,000.00 807,166.26 311,197.54 962,790.81 371,197.54 4,554,695.99 3,258,675.97 2,451,509.71 945,163.12 9,451,631.17 (4,906,112.96)

11 5,840.40 171,187.00 60,000.00 887,882.89 311,197.54 1,059,069.89 371,197.54 4,925,893.52 3,584,543.57 2,696,660.68 945,163.12 10,396,794.29 (5,476,741.17)

12 3,716.62 188,305.70 60,000.00 976,671.18 311,197.54 1,164,976.88 371,197.54 5,297,091.06 3,942,997.93 2,966,326.75 945,163.12 11,341,957.41 (6,048,582.97)

13 2,365.12 207,136.27 60,000.00 1,074,338.30 311,197.54 1,281,474.57 371,197.54 5,668,288.60 4,337,297.72 3,262,959.42 945,163.12 12,287,120.52 (6,621,197.05)

14 1,505.08 227,849.90 60,000.00 1,181,772.13 311,197.54 1,409,622.03 371,197.54 6,039,486.13 4,771,027.49 3,589,255.37 945,163.12 13,232,283.64 (7,194,302.59)

15 Residual value 957.78 250,634.89 60,000.00 1,299,949.34 311,197.54 1,550,584.23 371,197.54 6,410,683.67 5,248,130.24 3,948,180.90 945,163.12 14,177,446.76 (7,767,720.87)

- The results shows a negative life cycle cost. That means we have a saving in the life cycle of the ERWs system.

- According to the below chart, pay back period is 2 years.

Saving

Tota

l co

st a

fter

eac

h y

ear

(p=i

-m-b

)

Year

Investment related costsAnnual recurring costs

(maintenance)Electricity Total costs

Calculation sheet

Energy recovery system for toilet exhaust and fresh air sypply system - comparison between Run-Around loop and Energy Recovery Wheel

(6,000,000.00)

(4,000,000.00)

(2,000,000.00)

0.00

2,000,000.00

4,000,000.00

6,000,000.00

8,000,000.00

10,000,000.00

12,000,000.00

14,000,000.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Cumulative cost, saving and cost after each year Vs years

Discounted cumulative costs(i)

Discounted cumulative saving (m) Total cost after each year(p=i-m-b)

Calculation sheet

Data availble

Air flow data for energy recovery system

Out door air dry bulb temperature (t1) 32.2 ⁰C

Out door air RH1 80 %

Toilet exhaust air temperature (t3) 25 ⁰C

Toilet exhaust air RH3 50 %

Energy recovery for riser 01 l/s Pa

Toilet exhaust air flow rate | external static pressure 3175 335

Supply air flow rate | external static pressure 5467 300

Energy recovery for riser 02

Toilet exhaust air flow rate | external static pressure 2740 365

Supply air flow rate | external static pressure 6338 300

Calculation sheet

Assumptions/ conditions:

1. Energy savings of individual equipments due to an energy recovery system are not considered

2. COP of the chiller (from the employer's requirement of the tender document) = 6.2 COP = refrigerent effect in kW / input in kW

3. Thermal load saving due to ERW is equal to the thermal load saving of chillers

4. Sensible effectiveness (εsensible) 0.6 from AHRI guide line V

5. Latent effectiveness (εsensible) 0.6 from AHRI guide line V

6. Air density, Specific heat (Cp) & humidity (from Data generated from the software developed by S.A.Klein and F.L.Alvarado.)

ρ (kg/m3)

cp (kJ/(kg

K))

w (from

psychrome

tric chart)

t1 1.175 1.005 0.0244

t3 1.184 1.005 0.0099

7. hfg 2501000 J/kg

8. Equal volume of supply air and toilet exhaust air are passed through the wheel. The balance fresh air is mixed in the mixing box after the wheel.

Calculations

ERW 01 ERW 02

Mass flow rate entering exhaust air me 3.73 3.24 kg/s

Mass flow rate supply air ms 3.73 3.24 kg/s

Run-Around

loop - 01 ERW 01

Run-Around

loop - 02 ERW - 02

Recovered sensible heat transfer rate(kW) Qsensible = ε sensible x m min x Cp (t1-t3) 16.20 16.20 14.08 14.08

Recovered latent heat transfer rate(kW) Qlatent = ε latent x m min x hfg (w1-w3) 0 81.17 0 70.59

Recovered total heat transfer rate (kW) Qtotal= Qsensible + Qlatent 16.20 97.37 14.08 84.67

Electrical power saving (kW) (Qtotal/COP) 2.61 15.70 2.27 13.66

Riser 01 Riser 02

t2 = t1-Qs/(m1Cp1) 27.88 27.88 ⁰C

Energy Recovery System -

01

Energy Recovery System -

02

Calculation sheet

t3 = t3+Qs/(m1Cp1) 29.32 29.32 ⁰C

Calculation for the pump power

Note: - For the estimation circulation liquid is considered as water

- t1,t2 and t3 data are provided for a coil selection software (developed by S & P Coil Product Ltd, England) to findout fluid flow rates, pressure drops etc.

Result sheet is attached (Annex).

- Consider the 32mm Copper tubing for water stream, and same pipe arrangement is considered for both loops

- Flow velocity- 1m/s, Friction Loss- 400Pa/m

- As per Carrier Pipe Design Manual

Qty Equalent

Length (m) -

le

Length (m) -

l (=Qty x le) Friction Loss

(Pa) - l x 400

Straight Pipe 1 30.00 30 12000

90 0 screwed elbows 6 0.70 4.2 1680

Globe Valves 6 11.58 69.48 27792

Non-return Valves 1 4.27 4.27 1708

Strainer 1 2.74 2.74 1096

T joints 3 2.13 6.39 2556

46832

Pipe/Fitting/Valve

Calculation sheet

Total Pump pressure drop without coils 46.83 kPa

Riser 01 Riser 02

Drop through coil 57.80 57.6 kPa From coil selection sheet ()

Total Pump pressure drop with coils 104.63 104.43 kPa

Safety Factor to pressure drop 1.05 1.05 kPa

Pump pressure drop with SF 109.86 109.65 kPa

Water flow rate 0.90 0.8 l/s From coil selection sheet ()

Required Power to pump (QxH/η) 0.15 0.13 kW : η = 65%

Fans static pressure

Run - around coil

Riser 01 Riser 02

S/A Fans static pressure (external static pressure+pressure drop through coil) 539.7 453.9 Pa

TEA Fans static pressure (external static pressure+pressure drop through coil) 573.1 517.9 Pa

Energy recovery wheel

Pressure drop through wheel 200 200 Pa

S/A Fans static pressure (external static pressure+pressure drop through wheel) 500 500 Pa

TEA Fans static pressure (external static pressure+pressure drop through wheel) 535 565 Pa

Power consumption with ERW

Note: fan efficiency ( η ) is considered as 65%

ERW 01 ERW 02

Power S/A fan (QxH/η) 4.21 4.88 kW

Power E/A fan (QxH/η) 2.61 2.38 kW

Power Rotor drive motor 0.18 0.18 kW Data sheet attached

Total 7.00 7.44 kW

Power consumption with run around loop

Loop 01 Loop 02

Power S/A fan (QxH/η) 4.54 4.43 kW

Calculation sheet

Power E/A fan (QxH/η) 2.80 2.18 kW

Power for pump 0.15 0.13 kW Data sheet attached

Total 7.49 6.74 kW

Power consumption without ERU

Riser 01 Riser 02

Power of AHU OA fan (QxH/η) 2.52 2.93 kW

Power of toilet exhaust fan (QxH/η) 1.64 1.54 kW

Total 4.16 4.46 kW

Run around

loop ERW

Riser 01 -0.72 12.87 kW

Riser 02 -0.01 10.68 kW

Power saving {Consumption without

ERU-(Consumption with ERU-Saving

due to ERU)}