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7/29/2019 Technical Design and Economic Assessment of Building Integrated PV Systems: A Case Study of a Solar Pumping S

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Technical Design and Economic Assessment of Building Integrated PV

Systems: A Case Study of a Solar Pumping System

for the ICT Building in M.U.S.T.

R. C. Pallugna, C.L.Y. Cabangbang, C.R.N. Bibiano, N.D. Caliao, PhD

Mindanao University of Science and Technology

ABSTRACT

In an effort to evaluate the comparison of renewable energy investment and the cost of the

electric utility after 25 years, a study for the economic merits of a solar PV integrated in buildings is

conducted for the Mindanao University of Science and Technology (MUST) specifically at ICT

building. The cost of the system and the price of the electric utility are also presented in the paper.

Solar photovoltaic (PV) integrated in the building could take part in a critical role as an alternative

way of energy and electricity demand.

Keywords: Solar Pump, PV system, Life CycleCost, Economic Comparison, System

Efficiency

1. Introduction

Two of the most important necessities to

human life in the modern cities are water and

electricity. Although water is free, energy is

needed to make it available for use. Mainly it is

electrical energy that is used to draw and

supply water. But, today, electricity is getting

expensive, and so the cost of water is also

getting higher. However, the Sun, through

solar PV technologies, can be used generate

electricity to supply water. Solar energy is

free, clean, and sufficient and solar PV

technologies are getting cheaper and more

available [1].

The Philippines, being a tropical country

has an abundant source of solar energy with

an average irradiance of 4.9 kilowatt-hours

per square meter per day [2].

This paper describes the process of

designing a solar PV water pumping system

for the Information and Communications

Technology (ICT) building of Mindanao

University of Science and Technology (MUST)

and of evaluating its economic merits in

comparison to the cost electric utility during

its life-span of 25 years. The PV system would

supply power to the existing water pump

during the day, and which would be supplied

by the utility at night or when solar power

cannot.

2. Methodology

The methodology of this research

involves data collection of both the energy

demand of the load and the available solar

energy of the site, the sizing and determining

the PV system output and the computation of

its net present value (NPV) to assess its

economic value.2.1 Data Collection: The data gathered

mainly involved water requirements and availablesolar energy.

2.11 Water Requirements:

Water User Information: ICT is a 4-storey

school building with 15 class rooms each with acapacity of 42 students each. It has also 12

computer rooms, one conference room, 4 offices,and 8 rest rooms. It is located at the eastern part of

MUST. Water from water utility flows to a 150,000

gallon underground storage tank and is thenpumped to 2x1000 gallon tanks at the top of the

building and from there, by gravity, flows to the 8

rest rooms, two, at each floor of the building [3].

Water Use Information: Pump starts andstops were timed and recorded from 7:00am to


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5:00 pm for the whole week during regular school

days. The data gathered are shown in table 1 and

the graph is shown in Figure 1. From these it was

computed that the average water requirements for

the ICT building is around 30,500 gallons per dayand with the highest at around 32,000 gallons per

day. These are based on the average pump hours

of 7.2 hours and longest pump hours of 7.5 hours

and the pump rate of 70.5 gallons per minute

respectively.

Table 1: Pump Hours per dayTime (*) Monday Tuesday Wednesday Thursday Friday Saturday

7:00-8:00 26 min 23 min 23 min 20 min 18 min 16 min










10 hrs 7.2 hrs 7.0 hrs 7.3 hrs 7.4 hrs 7.5 hrs 6.8 hrs

The values of the y-axis of Figure 1 are

minutes, the length of time the pump runs in one

hour. The graph shows that the highest

requirement is between 12:00 noon to 1:00 p.m.,

with the pump running for 60 minutes, or 1 hour.

0

10

20

30

40

50

60

70

Monday

Tuesday

Wednesday

Thursday

Friday

Saturday

Figure 1: Graph of Pump hours showing peak usage isbetween 12:00 Noon to 1:00 p.m.

A watt-hour meter was also used to

measure the energy consumed by the pump for 1

month, between December 15, 2010 to January 25,

2011. Figure 2 shows the pump consumes an

average of around 30 kilowatt-hours for 1 month.

Figure 2: Energy consumption of water pump

Pump Information: The pump used is a 5

horse power (4kw), 3-Phase, 220 volts, 60 Hz,centrifugal pump with a 70.5 gallons per minute

flow rate.

2.12 Available Solar Energy:

In the Philippines, solar energy resources,

known as INSOLATION or incident solar radiation,varies from 5.0 to 6.5 Kwh/m2/day during dry

season (March May) and 3.0 to 5.5 Kwh/m2/day

during wet season (November-January) [2]. In this

study the lowest available solar energy was used

so that the pump could still run at times when theenergy available is at its lowest.

2.2 Sizing of PV System Components

Sizing of PV system components includes

the number and size of array, sizing and choice of

inverter, wiring and switching system.

PV array sizing: The sizing of PV array

depends on the power requirement of the load and

the available solar energy. The power requirement

of the load (PR) was computed using the pumphours and measured using the kilowatt hour

meters. The available solar energy (Hd) is taken

from the data of the grid-connected PV-plant in the

city owned by CEPALCO.

The required rated array power (PR) is

given by the formula [4]:

(1 )(1 )

STCR P

d p inv p c

IP E

H =

(1)

[1 ( )]P R P c r T T = (2)


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20(219 832 )

800c a t

NOCTT T K

= + (3)

Dt

O

HK

H= (4)

WherePE (30kwh/day) is the power

demand,STCI is the irradiance at standard

condition equal to 1kw/m2,dH is the monthly

average daily solar radiation on the horizontal

surface equal to 4.05 kwh/m2/day, p is the array

efficiency equal to 92.3%, R is the PV module

efficiency of 13.3%, P is the module temperaturecoefficient of -0.485,

cT is related to aT , rT is the

reference temperature of 25 degrees C, tK is the

clearness index,O

H is the monthly average daily

solar radiation on the horizontal surface,inv

is the

inverter efficiency equal to 85%, p is the dirt and

dust losses equal to 10%,c is the wire and

electrical component losses equal to 2%.

2

2(30 / )(1 / )

(4.05 / / )(0.923)(0.90)(0.98)R kwh day kw mP

kwh m day=

= 9099 Watts

The number of Modules (No) is given by

RO

STC

PN

P= =

9099

170= 54 modules

Each module occupies an area of 1.3

square meters and the whole the array occupies

73 square meters. The PV modules to be used areSHARP NE-170UC1 [5]

Table 2: PV module SHARP NE-170UC1 characteristicsB rand Tech- MaxP ower I V Temp NOCT Eff Area/ price

nology (Pstc) (A) (V) coeff . (deg C) (r)))) module (Php)

SHARP Poly-si 170 W 5 35.4 -0.485 47.5 13.3 1.3 23,600

The array configuration is dependent on

commercially available solar inverters. The

modules would be connected nine modules in

series and six modules in parallel. The nine

modules in series would give the system voltage of

9x34.5 =310.5 DC volts and a current of 6x5= 30A

DC.

The PV System would be mounted on the

roof at an inclination of 8.4 degrees due south,corresponding to the latitude of Cagayan de Oro

City, on portion of the roof above the machine

room, which has an area 84.3 square meters for

the array. The front side of ICT is oriented 8

degrees south-east, adjusted to an inclination of

8.4 degrees due south which makes it almostdirectly under the path of the sun. Below is a

perspective of the ICT building with a raisedportion on the rooftop as the proposed location for

mounting the PV modules:

Figure 3: Perspective view of the ICT building

Sizing the inverter: The nominal system

power is 56x170 = 9520 watts, which is the

product of the number of modules multiplied bythe power of each module. The array current is

equal to current per module times the number of

modules in parallel or 5x6 = 30 amperes.

The inverter would be AURORAPhotovoltaic Inverter model PVI-10.0-OUTD. This

is a 10KW, 220VAC, 3 Phase inverter [6].Magnetic Contactors or solid state relays of

the same rating with the inverter should be usedto switch the pump to or from the PV system or to

or from the utility

2.3. Economic Comparison

This is a comparison between the cost

of electricity from the utility in comparison

with the electricity generated from the PV

system to pump water. This is done by

comparing their present value for 25 years,

the life-span of the PV system


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The present value of all the monthly

energy savings, less its operation and

maintenance expenses, of the pump when

using solar energy is brought to the present

time and compared to the present value of the

entire project cost using the formula

(1 ) 1

(1 )

n

n

iP A

i i

+ =

+

where:

P= Present Value

A= Annuity

i= rate (10%)

n= number of years (25)

The results are shown in Table 3 and

Table 4. In this study, U.S. dollar to peso

conversion rate is 45.

Table 3: Balance of system Cost [2]Component Unit price Cost

USD Php

Inverter 4,780.00 430,200.00

contactors 140.0 12,600.00

Mountings(per watt) 1.00 450,000.00

Wirings, etc(per watt) 0.75 337,500.00Labor(per watt) 0.75 337,500.00

Permits(per watt) 0.25 112,500.00

BOS Cost 1,680,300.00

Module Cost 472.0 1,146,960.00

TOTAL COST 2,827,260.00

Table 4: Graph of the economic comparison of

utility versus PV generated energyEconomic Comparison

Annual Utility Cost (AUC) 109,500.00

Present Val of AUC (i=10%) 1,186,400.30

Total Project Cost 2,827,260.00

NPV (negative) (1,640,859.70)

3. Results and Conclusion

Although PV technologies are available

and their prices going down, but up until

today, based on the economic evaluation, the

net present value (NPV) is negative, which

means that at present it is still too expensive

to apply PV system for pumping applications

for the ICT building.

4. References:

[1] The Cost Of Installed Solar PhotovoltaicSystems Drops Significantly Over The Last

Decade, http://www.sciencedaily.com

/releases/2009/02/090219152130.htm

[2] C.D. Gozon, Buy Back Power on Grid

Connected Residential PV Undergrad Thesis,

MUST, 2011

[3] R.D. Galua, Proposed Four Storey School

Building Infrastructure Planning and

Development Office, Mindanao University of

Science and Technology

[4] Clean Energy Project Analysis: Basics of Solar

Energy, www.retscreen.net

[5] http://www.ecodirect.com/Sharp-NE-

170UC1-170-Watt-Solar-Panel-p/sharp-ne-170uc1.html

[6] Power-one, 10kW Aurora inverter,http://www.solacity.com

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