Optimization of Solar POwer Generation for Desert Climate Site Refinery

7/24/2019 Optimization of Solar POwer Generation for Desert Climate Site Refinery

1/56

Project R 4-1

Optimization of Solar Power Generation

for Desert Climate Site Refinery

PV-Greenhouse Project

Final Report (1998-2003)

Dr. A. Al-Ibrahim, PI KACST

Dr. Naif Al-Abbadi, CI KACST

Dr. Ibrahim Al-Helal, RI KSU

Eng. Mohammad Alghoul, RI PEC


2/56

SUMMARY

Agricultural efforts are normally carried in remote area where electricity

from national electric grid may not exist or grid extension is expensive.

Therefore, a stand-alone power supply is always in demand therein. Cooling

and pumping equipments dominate the demand for electricity in greenhouses.

The demand for electricity occurs during the times when solar radiation is

available and in abundance; such excellent harmony between demand and

supply elucidate the feasibility of using solar energy. Therefore, utilization of

solar energy for powering greenhouses in desert climate site refinery is

considered amongst the important applications of solar energy and carries great

significance and success. More importantly, Saudi Arabia is equipped with

several oil refinery sites that may find this application useful. The main

objective of this research project is to quantify the potential of using

photovoltaic (PV) system to power greenhouses. The greenhouse under

investigation is located at al-Muzahmyah research station of the King

Abdulaziz City for Science and Technology (KACST). The PV-greenhouse

system consisted of the 14.72 kW PV arrays, battery storage system, power

conditioning system, data measurement and collection system and 9x39 fiber

glass greenhouse. During the operation of the system the potential harmony

between the solar radiation availability and the demand for electricity was

studied and quantified to optimize the PV-greenhouse for desert climate site

refinery operation. Greenhouse was in full operation since July 2000. Data

Acquisition System (DAS) was in operation since Nov 2000. Five plantation

cycles were completed and the sixth one is in progress and expected to

complete by the end of February 2003. The performance of the PV subsystem,

battery subsystem and greenhouse cooling system were satisfactory.


3/56

TABLE OF CONTENTS

SUMMARY .......................................................................................................................

1. INTRODUCTION......................................................................................................... 1

2. OBJECTIVES ............................................................................................................... 3

3. LITRATURE REVIEW............................................................................................... 4

3.1THE PHOTOVOLTAIC INDUSTRY AND APPLICATIONS.................................................. 4

3.2GREENHOUSES ENVIRONMENT CONTROL.................................................................... 7

4. MATERIALS AND METHODS ................................................................................. 9

4.1POWER SYSTEM ......................................................................................................... 9

4.2

GREENHOUSE

SYSTEM

............................................................................................. 104.3CROP DESCRIPTION................................................................................................... 11

4.3MEASUREMENT AND DATA ACQUISITION SYSTEM .................................................. 12

5. RESULTS AND DISCUSSIONS............................................................................... 15

5.1PLANTATION CYCLES............................................................................................... 155.2GREENHOUSE ENVIRONMENT................................................................................... 20

5.2.1 Greenhouse Typical Operation........................................................................ 20

5.2.2 Fan-pad cooling system performance.............................................................. 22

5.2.3 Cooling Pads Clogging.................................................................................... 23

5.2.4 Greenhouse shading......................................................................................... 25

5.2.5 Cooling Fans Operation Optimization ............................................................ 26

5.2.6 Greenhouse Water Consumption..................................................................... 305.2.7 Greenhouse Heating ........................................................................................ 33

5.3PVSYSTEM PERFORMANCE ..................................................................................... 36

5.3.1 Daily Operation Profiles.................................................................................. 365.3.2 Six-days Operation Profiles............................................................................. 37

6. CONCLUSIONS ......................................................................................................... 49

REFERENCES................................................................................................................ 53

APPENDIX A Greenhouse System Specifications

APPENDIX B Solar Cell Module Specifications

APPENDIX C Measuring System Specifications


4/56

1

1.INTRODUCTION

The Kingdom of Saudi Arabia extends from Azimuth 50 to Azimuth 35

and from latitude 17 in the south to latitude 32 in the north. Because of its

geographical location and landscape, the Kingdom of Saudi Arabia is blessed

with the abundant availability of solar radiation. Statistically, solar radiation

values for several cities in the Kingdom are considered among the world

highest values. For example, the amount of monthly solar radiation incident on

a horizontal surface for Riyadh varied between 670 and 1000 W/m2, the lowest

value being in December and the highest observed value was during July

(Hummeida and Mohammad, 1993). It was also found that the ratio of the

actual to the maximum possible sunshine hours varied between 0.62 and 0.8.

Previous research to utilize solar energy to power several applications in

the remote areas of the Kingdom have shown great success. Communications,

cathodic protection, and heating are among the several examples. However, an

important application, linked to the natural security of the Kingdom, has not

been given great efforts by researchers. This application is agriculture. Similarto the other countries, agriculture is considered as the most important resource.

More importantly, demand for food in the Kingdom is immense and water is

scarce.

Agriculture efforts are normally carried in remote area where electricity

from electric utility companies may not exist or grid extension is expensive.

Therefore, a stand-alone power supply is always in demand.

Clean electricity can be produced via electronic system composed of

photovoltaic (PV) cells and other attached electronics. PV cells are clean solar-

electric converters, convert solar radiation to direct current given a known

operating voltage.


5/56

2

Once solar systems are utilized in agriculture applications, another

advantage is gained. That is, the demand for electricity occurs during the times

when solar radiation is available and in abundance; an excellent harmony

between demand and supply. For example, demand for electricity ingreenhouses during summertime is dominated by cooling and pumping

equipments. Hence, this demand occurs during daytime when solar radiation is

abundant. Figure 1 depicts this harmony.

The concept of utilizing photovoltaic system to power greenhouses

carries great significance and success. Therefore, it is the main objective of this

research project to build a greenhouse powered by PV system. The location ofthe project was selected to be in the research station of the king Abdulaziz City

for Science and Technology at al-Muzahmyah.

Greenhouse was in full operation since July 2000. And, Data Acquisition

System (DAS) was in operation since Nov 2000. Six plantation cycles had

finished. PV subsystem, Battery subsystem, greenhouse cooling and heating

performance are satisfactory.

Figure 1.1: The harmony between the electric demand and solar radiationavailability in greenhouses applications during summertime.

Lighting and Misc. Load

Cooling Load

So

lar

Radia

tion

00:00 12:00 24:0006:00 18:00

Energy

Time


6/56

3

2.OBJECTIVES

The project aimed to achieve the following objectives:

1. Quantify the operating efficiency of the new SANYO PVmodule designed to sustain harsh desert climate.

2. Quantify the potential harmony between the solarradiation availability and the demand for electricity.

3. Study the economic feasibility and practicality of a stand-alone photovoltaic powered greenhouse system.

4. Quantify the economics of implanting heating elements tothe PV-Greenhouse system.

5.Analyze system operation and exercise different operatingmodes of the system to optimize the system design.


7/56

4

3.LITRATURE REVIEW

This section reviews the studies and efforts conducted by other

researchers in the photovoltaic industry and applications, as well as

greenhouses environment control.

3.1 The Photovoltaic Industry and Applications

Photovoltaic industry is growing rapidly as concern increases about

global warming and as a result of falling prices resulting from technological

breakthroughs.

For most of the eighties and early nineties the major markets for solar

panels were remote area power supplies and consumer products (watches, toys

and calculators). However in the mid nineties a major effort was launched to

develop building integrated solar panels for grid connected applications.

The PV sector is the second-fastest growing energy source in the world

after wind power. Sales of PV modules grew by 44% in 2000 and 30%-40% in

2001. Sales are expected to increase 30%-40% in 2002.

The PV cells market divides broadly into five sectors, namely Industrial

Systems, Mass Market Products, Rural (off-grid) Systems, Building-integrated

(on-grid) Systems, and Centralised (utility) Systems. According to the UK-based

Intersolar Group, the Home Systems sector will witness the strongest growth

in 2002.

Japan, the US and Germany, in declining order, lead the world in the

residential PV market. According to the New Energy and Industrial

Technology Development Organization, solar power systems in Japan currently

have a total power output of more than 300MW. The Japanese Ministry for the


8/56

5

Economy, Trade and Industry plans to promote at least 70,000 'Roof

Programmes' during the fiscal year 2002/2003.

The German Association for Solar Energy (Deutscher Fachverband

Solarenergie - DFS), believes that Germany - with a 54% market share - is the

European leader in producing solar collectors. Consumers in Germany can

obtain low-interest credits to finance solar panels for their roofs. By 2003,

Germany intends to have subsidised more than 100,000 private homes with

photovoltaic systems.

In the US, PV manufacturing capacity has increased by more than a

factor of seven since 1992, according to the Department of Energy. DoEprojections indicate a steady decline in average PV module manufacturing costs

to US$1.16 per peak watt at total manufacturing capacity of 865MW by 2005,

from US$2.73 per peak watt in 1999 (at a capacity of 99.3MW). For 2002, the

projections are costs between US$1.5-US$2.00 for total manufacturing capacity

of 300MW-350MW.

The cost of solar electric systems has come down over 90% in the lasttwo decades, making the economics more viable, according to California (US)-

based Strategies Unlimited, the leading photovoltaics market research firm. The

DoE says the average cost of electricity from PV cells has dropped from more

than US$1.00 per kWh in the 1980s to nearly US$0.20 per kWh today.

Major photovoltaic equipment manufacturers such as BP Solar (UK),

Siemens Solar (Germany), Kyocera (Japan), AstroPower (US) and Sharp

(Japan) have all announced plans to more than double their production

capacities over the coming years.

Also, photovoltaic solar cells are often used in remote locations to

provide a small negative voltage to the metal structure, such as bridges,


9/56

6

pipelines, buildings, tanks, wells and railway lines, which can protect metal

structures from corrosion. Photovoltaic system also used to power electric

fences that are widely used in farms to prevent stock or predators from

entering or leaving an enclosed field.

Solar cells are also used for lighting at remote area where the cost of

power is too high to consider using the grid. Such applications include security

lighting, navigation aids (e.g. buoys and beacons), illuminated road signs,

railway crossing signs and village lighting. Such systems usually consist of a PV

panel plus a storage battery, power conditioner and a low voltage, high

efficiency DC fluorescent lamp (reference). These systems are very popular inremote areas, and considered as one of the major applications of PV in

developing countries.

The cost of electric power to drive these systems and the high cost of

maintaining conventional power systems limited their use. PV power systems

has provided a cost-effective solution to this problem through the development

of remote area telecommunications repeater stations. These typically consist of

a receiver, a transmitter and a PV based power supply system. Thousands of

these systems have been installed around the world and they have an excellent

reputation for reliability and relatively low costs for operation and maintenance.

Similar principles apply to solar powered radios and television sets, emergency

telephones and monitoring systems. Remote monitoring systems may be used

for collecting weather data or other environmental information and for

transmitting it automatically via radio to the home base.


10/56

7

3.2 Greenhouses environment control

The greenhouse industry development represents a main strategic

objective of the Saudi government because it increases the income resources

and insures food security since huge consumption of vegetables is in demand.

As a result, the greenhouses production has flourished and large capitals have

been invested on it. The first reported greenhouse in Saudi Arabia was

established in 1980 located in Riyadh. The number of greenhouse projects for

the period from 1980 to 1997 was about 615 produced 294 thousand tons per

year (Ministry of Agriculture and water, 1998). About 30% of greenhouses are

located in Riyadh area (Ministry of Planning, 1998). Increase of greenhouses inSaudi Arabia can be attributed to the development of chemicals and

environmental control devices that provide a suitable environment for plant

growth and development. The common greenhouse crops in Saudi Arabia are

vegetable and flowers.

Greenhouses in Saudi Arabia require environmental modifications to

create a suitable environment for plants growth and production. Greenhouseshave environmental modifications that are essentially used for cooling,

ventilating and heating. Ventilation can remove excess heat, increase air mixing,

introduce the outside air with a higher CO2 concentration, and reduce

temperature stratification in the greenhouse (Aldrich and Bartok, 1992).

Fan ventilation system is commonly used to regulate humidity and

temperature in the greenhouse (Walker, 1965). During summer, ventilation

alone is not enough to maintain optimum interior temperatures. Therefore,

water evaporative cooling systems are used to reduce inside air temperature to

an acceptable level (Hellickson, 1987). For most of greenhouses located in

Riyadh area, cooling for summer, early winter and late spring (the period from


11/56

8

March to October) is commonly accomplished by fan and pad evaporative

cooling systems.

Generally, the cooling performance of the fan-pad evaporative cooling

system is affected by some factors such as air velocity through pad (face

velocity), pad thickness, pad wetting rate and climatic conditions (Wiersma and

Benham 1974; Al-Helal and Al-Tweejre, 2001). The American Society of

Agricultural Engineering (ASAE, 1994) recommended an air velocity of 1.25

m/s for the standard 100 mm thick Cel-dek pad. An optimum water

circulation rate of 2.4 l/(min.m2) of pad surface has been recommended by

Wiersma and Benham (1974) for efficient cooling and effective pad cleaningaction under most practical conditions.

High solar radiation intensity affects greenhouse operational cost

because it increases the greenhouse-cooling load. When the level of solar

radiation is high, the temperature inside greenhouse may become too high and

heat stress the crop. Shading is the major method of reducing solar load inside

the greenhouse because shading materials absorb some of the solar radiation

(Willits, 1992). During periods of high solar radiation, greenhouse shading is a

very important factor in reducing leaf and inside air temperatures .

Solar radiation is the main source of energy input for greenhouses even

on cool winter days, temperatures can rise to excessively high values if the sky

is clear. Plants inside the greenhouse can absorb most of solar energy by the

process of transpiration. Therefore, transpiration from plants can is an

important cooling process as the energy needed to evaporate the water comes

from the air around the plants leaves.


12/56

9

4.MATERIALS AND METHODS

The system is designed to be a stand-alone and consists of solar cells

delivering 14.7 kW. The solar cells supply electric power to the load (electric fans &

cooling pump, and other electrical accessories) of the greenhouse (9m x 39m).

Vegetables were planted in the greenhouse and irrigated using a drip irrigation

system.

4.1 Power System

The solar cells adopted were of the type HIT (Heterojunction with

Intrinsic Thin layer). The HIT solar cell is a hybrid composed of a thin single

crystal wafer surrounded by layers of ultra-thin amorphous silicon. This

structure reduces energy loss and results in high conversion efficiency. The

modules containing the HIT solar cells are designed to be resistant to high-

temperature efficiency loss. Hence, it is very effective to place these modules in

high temperature locations like Saudi Arabia. Solar cell modules were

manufactured in Japan, and the other equipment of solar power generation was

purchased locally from the Kingdom. Tables 4.1 shows the PV power system

components and Figure 4.1 its configuration.

Table 4.1: PV System components

Component Description

PV array92 SANYO manufactured modules, 160 Watt capacity each.

Total of 14.72 kW

Inverter 15 kVA SunPower with 15 kWp MPPT and 120 V

Batteries 60 deep charged batteries. Total of 3000 Ah (350 kWh)


13/56

10

Sub-Array

box

&63A

MCB

Main

JunctionBox

Including

circuitbreakers

LoadDistribution

System

Manager

15kWpMMPTand

10kVA

DC/ACInverter

MCB

32x SANYO 160W

Array 1

120VDC

Battery Bank

3000Ah @ C120

350 kWh

2 3 41

Array 3

32x SANYO 160W

Sub-Arraybox

&63A

MCB

28x SANYO 160W

Array 2

2 3 41

Sub-Array

box&

63AMCB

Figure 4.1: Skeleton of PV system

4.2 Greenhouse System

The greenhouse is located at the research station of the King Abdulaziz

City for Science and Technology at Al-Muzahmyah, Saudi Arabia. Photo of the

39 m x 9.0 m Quonset greenhouse is shown in Figure 4.2 with its long

dimension or ridge a long a north-south line. The greenhouse constructed of

metal framing and fiberglass covering. The fan and pad evaporative cooling

system was used for cooling. Ventilation was achieved by two exhaust fans

located on the south-end of the greenhouse, and incoming air was forced

through 12 m2(2m 6m) of 10 cm thick cooling pads (Cel-dek, mounters) set

on the north end of the greenhouse. The rated ventilation rate for each of the

two fans was 36000 m3/hr. Fans and cooling water pump were powered by


14/56

11

photovoltaic system. Table 4.2 shows the greenhouse electrical load

distribution.

Table 4.2:Greenhouse Load Distribution

EquipmentRequired Power

(W)

Average Daily Duty

Cycle (hr)

Mean Daily Energy

Demand (Wh/day)

Two Air Fans (2 x 1.5 Hp) 2237 16 35792

Circulation Pump (0.75 Hp) 559 16 8944

Control (PC) 400 24 9600

Total 3196 -- 54336

4.3 Crop description

Two types of crop were used; Tomatoes (Red Gold) and Cucumbers

(Vegaro). Tomatoes were used during winter seasons and Cucumbers were

used during summer seasons. Seeds were planted in a nursery and grown fortwo to three weeks. Then, seedlings were transferred inside the greenhouse in

four double rows, each single row having 80 plants, and grown until the

completion of the growing season. Plants were irrigated two times a day during

winter and three times a day during summer using drip irrigation system.

Irrigation time was 10 minute. Nutrient solution was formed by dissolving

fertilizers in the irrigation water.

The nutrient solution consisted of Calcium Nitrate, Potassium Nitrate,

Magnesium Sulfate, Mono-ammonium Phosphate, Ammonium Phosphate,

Ammonium Nitrate, Iron Chelate, Borax, Manganese Chelate, Copper Chelate,

and Zinc Chelate. They were dissolved in fresh water. Calcium Nitrate and


15/56

12

Potassium Nitrate were dissolved in tank A, and the remaining components

were dissolved in tank B. Table 4.3 shows analytical results for cooling pad

water and irrigation water.

Table 4.3Analytical results for cooling pad water and irrigation water as analyzed by NaturalResources and Environment Research Institute at KACST.

Element Cooling Pad Water Irrigation waterDate 5/5/2002 15/5/2002 5/5/2002 15/5/2002

EC (ms/cm) 2.26 2.3 1.39 1.48PH 7.66 7.95 8.15 8.09Total Hardness (mg/l) 722 747 424 476TDS@ 105oC 1462 1553 821 947Ca++(ppm) 204 208 116 138

Na

+

(ppm) 218 245 137 143K+(ppm) 14 14 6 10Mg+(ppm) 52 55 33 32Cl-(ppm) 543 612 383 404CO3

-(ppm) ND ND 3 NDHCO3

-(ppm) 179 155 109 112SO4

-(ppm) 484.5 431.4 235 255.1SAR 3.5 3.9 2.9 2.8

ND = Not Detected

4.3 Measurement and Data Acquisition System

Data Acquisition System (DAS) was installed during November 2000 to

measure data such as the amount of solar radiation and the results were

statistically processed. Measurement items are as shown in Table 4.3. All data

were acquired in an instantaneous manner by a data logger and an IBM

compatible computer to collect data every 1 minute.

The DAS was powered by the PV solar system (including Battaries).

New sensors added and new setup was done in 4 November 2002, as shown in

figure 4.2 to improve the measurements and the analysis. The total

Measurement items are shown in Table 4.4.


16/56

13

Table 4.4: Data Acquisition System Parameters

No Channel Unit

1 Ambient Temperature (C)

2 Wind Speed (m/s)

3 Wind Direction (Degs)

4 Horizontal Irradiance (W/m2)

5 Tilt Irradiance (W/m2)

6 Ambient Relative Humidity (%)

7 PV Temperature (C)

8 Battery Temperature (C)

9-14 Greenhouse Temperature 1,2,3,4,5,6 (C)

15-18 Greenhouse Relative Humidity 1,2,3,4 (%)

19-21 Greenhouse Solar Radiation 1,2,3 (W/m2)

22-23 Greenhouse Air Speed 1,2 (m/s)24 Water Flow (l/m)

25 Fan Speed 1 (rpm)

26 Fan Speed 2 (rpm)

27 PV Array 1 Current (A)



30 PV Array 1 Voltage (V)



33 PV Array Average Voltage (V)34 PV Array Power (kW)

35 Battery Current (A)

36 Battery Voltage (V)

37 Battery Power (kW)

38 Load 1 Current (A)



41 Load 1 Voltage (V)



44 Load Power (kW)

45 Fan 1 Power (W)

46 Fan 2 Power (W)

47 Pump Power (W)


17/56

14

Figure 4.2Location of sensors in the greenhouse

AS2

GRH4 GT4

GT6

GRH2 GT2

2m9.5m29.5m

AS1

34.5m

GRH1

ole

GT1

39.5m

GRH3 GT3

GSR1

GSR3

GSR2

GT5

FM

19.5m

FS1FS2

2.6m

2.4m

2.2m

1.5m

1m

0.75m

0.25m

0m

ole ole ole ole ole

CoolingPads

Fans

Location of Sensors in Muzahimiyah Greenhouse

ASFMFSGRHGSRGT

Air SpeedFlow MeterFan SpeedGreenhouse Relative HumidityGreenhouse Solar RadiationGreenhouse Temperature


18/56

15

5.RESULTS AND DISCUSSIONS

5.1 Plantation Cycles

Five plantation cycles (cucumber and tomato, alternatively) in the

greenhouse had been completed and the sixth is in progress and expected to be

completed by the end of March 2003. The first, and fourth plantation cycles

were satisfactory. However, tomato plants in the second cycle were infected

with several viruses that were transmitted from other infected greenhouses in

the farm. As a result, the plants were removed and discarded. Also, the total

production of the third plantation cycle was weakened because of insufficientcooling attained by the cooling system. The cooling system encountered

several power shutdowns primarily due to power delivery failure from the PV

subsystem. On the other hand, the fifth plantation cycle encountered a larger

damage due limited availability of water (for irrigation and cooling), from the

main supply.

The fourth plantation cycle started on late October 2001, and concluded

on the end of April 2002. Figure 5.1 shows the variations of the tomato yield

(kg) with time of the fourth plantation cyle during winter growing season of

2002, which totals 2620 kg. The figure shows that the maximum yield of about

600 kg was observed on Feb 4, 2002.

The fifth plntation cycle started on 20 May 2002, and concluded on 19

Aug 2002. Figure 5.2 shows the variations of the cucumber yiled (kg) with time

of the fith cycle during summer growing season, 2002. cycle. The total

cucumber yield during this cycle totled 663kg.


19/56

16

The sixth plantation cycle strted on 5 Nov 2002 ans still in progress.

Figure 5.3 shows the tomato grouth rate during the cycle till the date of this

report. The cycle is expected to end by mid April 2003.


20/56

17

0

100

200

300

400

500

600

Jan

3

Jan

4

Fe

b1

Fe

b2

Fe

b3

Fe

b4

Marc

h1

Marc

h2

Marc

h3

Marc

h4

Yie

ld(kg)

Fig 5.1: Variations of the tomato yield (kg) with time during the fourth plantation cycle (W


21/56

18

0

20

40

60

80

100

120

140

160

Jun3 Jun4 July1 July2 July3 July4 Aug1

Yield

(kg)

Fig 5.2: Variations of the Cucumber yield (kg) with time during the fifth plantation cycle (S


22/56

19

0

20

40

60

80

100120

140

160

180

200

Nov3 Nov4 Dec1 Dec2 Dec3 Dec4 Jan1 Jan2

(cm)

Height (cm)

Width(cm)

Fig 5.3: Varaitions of tomato growth during the sixth plantation cycle (winter, 20


23/56

20

5.2 Greenhouse Environment

This section describes the performance of the greenhouse cooling

systems and the major problems experenced during its operation. The

section starts with the explanation of a typical day operation. The section

will also include discussions of one of the major problems affected the

greenhouse operation which is the cooling pads clogging. Also, the effects

of shading on greenhouse environment will be discussed. In addition, the

efficiency of the fan and pad greenhouse evaporative cooling system will be

investigated.

In the effort to assess the cooling optimization, hence the power system

optimization, an experiment of operating the greenhouse cooling system

with different fan operation configuration will be discussed. As one of the

major factors affecting the greehouse economics beside power consumption

the water consumption in the greenhouse will also be discussed.

5.2.1 Greenhouse Typical Operation

Figure 5.4 shows the operation of the greenhouse during a typical day

(March 11, 2001). The figure shows temperatures and relative humiduity

for the air inside and outside the greenhouse, and fans power consumption.


24/56

21

Figure 5.4: Temperatures and relative humiduity for the air inside and outside the greconsumption on March 11, 2001.

11 March 2001

0

1

2

3

4

0:00 6:00 12:00 18:00 0:00

(kW)

0

10

20

3040

50

60

70

80

90

100

(%, degree C)


25/56

22

During this day, as the sun rises around 6:30 AM, greenhouse temperature

began to rise untill it reached 26oC around 7:45 AM, during which, the first fan

started to operate and consequently the second fan also. As the sun sets,

around 6:00 PM, the solar radiation intensity and ambient temperature droped,

and hence the temperature inside the greenhouse droped accordingly to below

25 oC causing the operation of the fans to stop for the rest of the day.

5.2.2 Fan-pad cooling system performance

Figure 5.5 shows the variation of cooling efficiency, as a function of time

for 2 August and 3 August. The efficiency on those two days varied from 64 to

80% and averaged 71%. Highest efficiency during those two days occurred in

the morning when ambient air temperature was lowest.

Results showed that even in the afternoon when it was hot, cooling system

achieved acceptable level of cooling. The good performance of the fan-pad

evaporative cooling system can be attributed to two factors. First, the hot and

dry climatic conditions are ideal for evaporative cooling. Second, new clean

pads increased the exhaust fans ability to remove excess heat from the

greenhouse.


26/56

23

Figure 5.5 Cooling pad efficiency as a function of time (2 and 3 August, 2001).

5.2.3 Cooling Pads Clogging

Due to high salts concentration in water used for cooling, cooling pads

were clogged several times and were periodically replaced shorter than

anticipated. The salt content of water used for cooling exceeded 1500 ppm

(part per million). As the water evaporates over the cooling pads, high

concentration of salts accumulates and remains over the cooling pads and

hence very little air passed through the pad. This means that the minimum

standard of one air change per minute was not meet in the greenhouse.

Additionally, less contact between air and water, and hence less cooling and

humidity. Clogging air channels reduced the fan-pad cooling system ability

to cool the plants during hot weather and caused the fans to draw more

0

10

20

30

40

50

60

70

80

90

00:30

03:30

06:30

09:30

12:30

15:30

18:30

21:30

00:30

03:30

06:30

09:30

12:30

15:30

18:30

21:30

Time (hr)

Efficiency,


27/56

24

power than anticipated. During most of the daytimes, the averages inside air

temperatures with clogged pads ranged between 30 and 51 oC, while the

inside relative humidity ranged between 8% and 30%. This adversely

affected plant growth, and caused wilting to plants in the second half of the

greenhouse especially when accompanied by high solar radiation levels (10

AM to 4 PM).

Table 1 summarizes the recorded inside and outside climatic conditions

for the three working periods; they are: period 1 (the whole month of Jun

representing the case with old pads and without shade), period 2 (started on

1 July and ended on 17 July representing the case with old pads and with

shade), and period 3 (started on 17 July and ended on 23 August

representing the case with new pads and with shade).

Table 5.1. Daily main values of climatic data for the three periods.

Period Temperature (oC) Relative humidity (%) Solar radiation (W/m2)Outside Inside Outside Inside Outside

1 33.7 32.5 11.6 32.0 5702 34.4 30.4 14.2 42.0 5503 35.2 27.0 15.0 46.9 500

Table 5.1 shows that replacing pads clearly improved the

greenhouse environment. Air temperature and relative humidity inside

the greenhouse during daytimes were improved, ranged from 28 to 32


28/56

25

oC, and from 39.3% to 44%, respectively. The fan-pad cooling

efficiency was found to be around 73%, with 8 oC to 17.3 oC

reductions in temperature.

Electricity consumption with new pads was found to be around 22% less

than that with old clogged pads. Results also showed that the rate of

increase in electricity consumption is non-linearly related to the increase in

ambient temperatures. With clogged pads, the two fans draw very high

powers to meet the cooling requirement of the greenhouse, however,

cooling load was always higher.

5.2.4 Greenhouse shading

Roof shading improved inside conditions during extreme hours, and

reduced the stress on plants by decreasing the solar gain over plant canopy.

During the period from 9:30 to 17:30, air temperatures inside the

greenhouse ranged from 28 and 32 oC, compared to 38 to 44.2 oC outside

the greenhouse. At night, inside air temperatures ranged from 21 to 25 oC,

while the outside temperature was between 28 to 38o

C. Relative humidity

inside the greenhouse during night was between 48 to 81%, and between

11.7 to 28% for the outside air. Moreover, during the daytime the relative


29/56

26

humidity ranged from 39.3 to 44% for the air inside the greenhouse, and

from 7.8 to 10% for the outside air.

5.2.5 Cooling Fans Operation Optimization

To assess the performance of the cooling system at different fan load

operation, a study of the greenhouse environment was performed during

typical summer days with one fan operating. The greenhouse temperature

will be discussed and compared with temperature when two fans are

runnung. Table 5.2 shows the greenhouse temperature during 4th and 6th

of August 2002. Figure 5.6 shows the effect of cooling fans on greenhouse

temperature during day time (7:30am6:00pm) in August 2002.

As shown in table 5.2 and Figure 5.6, the rate of ventilation was found

to be influential on the inside air temperature. At daytime, and with one fan

running, mean air temperature inside the greenhouse was around 33 oC.

Where as, it was 30 oC with two fans running. The mean maximum

greenhouse temperature was around 37 oC with one fan. Where as, it was

32o C with two fans. This indicates that using two fans reduced the mean

greenhouse temperature more than 3 oC, and the mean maximum

greenhouse temperature 5 oC.


30/56

27

At nighttime, the fans were switched off daily every night at 9:00 pm.

Mean, mean maximum, and mean minimum greenhouse temperature were

less than 27 oC on 4, and 5 August 2002. This indicates that no need to run

the fans during nighttime.


31/56

28

Table 5.2: Effect of fans on the greenhouse temperature in 4, 5 & 6 August2002 during daytime and nighttime.

(a) Two Fans

Day Time Night TimeoC 4-August (7:30-18:00) 4-August (18:00-23:59) - 5-August (00:00-5:00)

GT (mean) 30 23GT (mean minimum) 23 21GT (mean maximum) 32 25

AT (mean) 40 31AT (mean minimum) 30 28AT (mean maximum) 43 34

(b) One Fan

Day Time Night TimeoC 5-August (7:30-18:00) 5-August (18:00-23:59) - 6-August (00:00-5:00)

GT (mean) 33 23GT (mean minimum) 24 21GT (mean maximum) 37 25

AT (mean) 41 32AT (mean minimum) 32 29AT (mean maximum) 44 36


32/56

29

0.00

5.00

10.00

15.0020.00

25.00

30.00

35.00

40.00

45.00

Green house mean

temperature

Green house mean

maximum

Temperature

Mean ambient

temperature

Me

t

Temp

erature(C)

One Fan Two Fans

Fig 5.6: The effect of cooling fans on greenhouse temperature during day time (7:30am6:0


33/56

30

5.2.6 Greenhouse Water Consumption

Greenhouse water consumption for cooling system was found to be

influenced by airflow rate throug the cooling pads. Using two fans

increased the evaporation of water during cooling process. As shown in

figure 5.7 the averages daily consumption of water with one fan running was

2.89 m3. Where as, with two fans the daily average was 4.85 m3. On

average, the amount of water consumption with one fan was reduced by

almost 41%. This was because using one fan reduced the airflow rate

through the pads, thus reducing water evaporation rate. Under the

experimental conditions, this percentage saving gives an absolute value of

about 1.96 m3.

Table 5.3 shows the monthly average consumption of water for cooling

of the greenhouse and irrigation of the plants for several months. The daily

average consumption of water for irrigation was 2.33 m3 irrelevant to the

number of fans in operation.


34/56

31

Table 5.3 : Monthly average consumption of water for the cooling of thegreenhouse and irrigation of the plants for several months

DateCooling Water

(m3) Irrigation Water (m3)

Jun-02 4.6 2.4Jul-02 4.1 3.5

Aug-02 3.6 2.2Sep-02 3.6 0.0Oct-02 1.6 0.0Nov-02 0.7 0.4Dec-02 0.0 1.2Jan-03 0.0 1.3


35/56

32

0

1

2

3

4

5

Cooling (Two Fans) Cooling (One Fan) Irri

WaterConsumption(m3/day)

Fig 5.7: Daily average cooling water and irrigation consumption (m3/day) during Augus


36/56

33

5.2.7 Greenhouse Heating

During winter season the air temperature inside the greenhouse need to be

maintained within the adequate limits (15 oC during the night and 25 oC during

the day) for crop production. Therefore heating system was designed for

greenhouse by applying the steady-state energy balance. The design assumed

that incoming solar radiation (Qsr) and heater energy (Qh) to be equal to the

outgoing heat losses (Qloss) and the heat removed by ventilation (Qv) air

neglecting the rate of change of energy stored in the greenhouse and other

small fluxes. The design based on several factors including ambient and inside

greenhouse temperatures, greenhouse size, type of covering, and rate of air

infiltration. Weather data for Riyadh (Solar Village Site) from 1996-2000 was

used for this purpose. The system was installed late febreuary 2002. The

source of greenhouse heating was chosen to be Diesel fueled due to the

relatively high cost of electricity operated system.

The heater faced automatic start problem during Winter 2002/2003

making it difficult to judge well the effect of heating on greenhouse

environment, especially at night , when it was not possible to operate the heater

manually. The heater performed well during seconed half of January 2003

when the heater was operated manually. Most of the heating requirements for

greenhouses are required during night.


37/56

34

Table 5.4 showes the consumption of diesel during this month, ambient

temperature, and greenhouse temperature during night time. The table shows

that on average, heating system was capable of of maintaining the inside

temperatures at acceptable limits for plants growth. For example, on Jan 2nd

the greenhouse was maintained at an air temperature of 120C when the

ambient temperature at night was 3 0C. . Also, the Table shows that during 13

days out of 21 days of the sampling data , mean greenhouse temperatures

during night time were less than 150C, while during 8 days, the mean

greenhouse temperatures were equal or greater than 150C,. The table shows

that the average daily consumption of diesel used for heating the greenhouse

was 42 litters.


38/56

35

Table 5.4. The consumption of diesel during the month of Jan, 2003, ambienttemperature, and greenhouse temperature during night time where thegreenhouse heating are required.

Daily

Mean Ambient

Temperature

Mean Greenhouse

TemperatureDay Diesel Consumption (Litter) At night time At night time1 57 10 122 50 3 123 58 6 144 22 15 205 77 6 76 45 8 207 36 7 138 58 7 99 22 8 1910 28 7 811 36 8 912 27 6 1813 27 6 714 62 6 915 34 9 2016 27 16 1417 12 8 7

18 59 3 1519 28 5 1520 66 9 1021 54 15 26

verage 42 8 13


39/56

36

5.3 PV System Performance

PV system operated normally following its completion and

commencement of operation in July 2000. The PV arrays werecleaned on weekly bases. Furthermore, no rust or stain that would

significantly diminish the function has been observed on PV cells

since installation. The PV system operation parameters were recorded

every minute. These parameter includeed solar insolation, PV cell

temperature, PV arrays currentas and voltages, PV power and the

battary storage current and voltage. This section illustrates the PV

system hourly operation prfile for the day of March 11, 2001 and for

the day of June 21, 2002. Which is followed comparing the PV

system performance for conscutive 6 day during the diffenet season

of the yaer i.e. March, June, September, December 2001. The

comparison is shown in terms of accumulated daily powerand 6 days

accumulated power. The section concludes with the battary dicharge

test that was performed to test the ability of the battary storage

system to supply electrical power to the greenhouse in the occasion

of the nonavailablity of solar energy due to clouds or others causes.

5.3.1 Daily Operation Profiles

One minute data for the entire day of March 11, 2001 is shown in figure

5.8. During this clear March day, batteries approached full charge by 9:00 am,

and hence PV power were used directly to supply the greenhouse electrical


40/56

37

components. If no demand for electricity was required, then the PV system

would be disconected form the system. Battery life time was affected by this

deep charging because the batteries were designed to sustain this deep charge

and discharge process. Figure 5.9 shows the hourly averaged data for the day ofJune 21, 2002 . During this clear June day, batteries approached full charge by

11:00 AM. During day time tilt irradiance data was recognized from 6:00 am to

7:00 pm reaching its maximum value at 12:00pm. The electric load in the

greenhouse was dominated by the two fan motors and water pump for indoor

cooling. From 9:00am to 8:00pm, the fans and water pump were working

contineously.

Load power profile occasionally showed sharp peaks due to start-up

current that flows when the two fan-motors start to run. However, this flow of

sharp startup current did not hinder the overall operation because the inverter

was sized to have sufficiently large capacity compared to the load demand.

Moreover, the two fans were designed to start in a sequential order, 10 second

laps time, to allow lesser demand for start-up current.

5.3.2 Six-days Operation Profiles

To assess the continous operation of the accumulated daily power

delivered by the PV system, the power stored in the battary system and the

power consumed by the greenhouse load is shown in figure 5.10 and tables 5.5

to 5.8. Figure 5.10 shows the operational performance curve over a 6-day

period (March 11 through March 16, 2001). Negative battery power indicates

battary charging.


41/56

38

Although there were days like March 14th when the amount of solar

radition was very low, the data shows that operation continued smoothly from

the following day onward.

Power generation and consumption over the 6-day period for March

2001, June 2001, September 2001, and December 2001 are shown in Tables

5.5 to 5.8. In these tables, PV power refers to the amount of electricity

generated by solar cell arrays during that interval. In addition, battery power

refers to the amount of discharge from storage batteries (amount of charge is

negative) while load power refers to the total amount of electricity consumed

(e.g., greenhouse load, battery cabinet ventilation fan, DAS computer, andother loss).


42/56

39

11 March 2001

-1200

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

1200

0:00 6:00 12:00 18:00 0:00

(W/m2)

-15

-10

-5

0

5

10

15

(kW)

Figure 5.8: Data for the entire day of March 11, 2001


43/56

40

0

100

200

300

400

500

600

700

800

900

4 6 8 10 12 14 16 18 20 22 24

Time

(W/m^2)

-15

-10

-5

0

5

10

15

Figure 5.9: Data for the entire day of June 21, 2001


44/56

41

-20

0

20

40

60

80

3/11 3/12 3/13 3/14 3/15 3/16

(kWh)

-2000

0

2000

4000

6000

8000(Wh/m2)

PV

(kW

BAT

(kW

LOA

(kW

TILT

(Wh

Figure 5.10: Operation data for 6 days period (March 11-16, 2001)


45/56

42

Table 5.5: Power generation & consumption for 6 days (11-16 March, 2001)

Date

TiltIrradiance(KWh/m2)

PVPower(KWh)

Battery ChargePower *(KWh)

Load Power(KWh)

Mar. 11, 2001 6.961 51.69 -14.46 26.48Mar. 12, 2001 6.690 47.65 -5.95 27.71Mar. 13, 2001 4.338 49.77 -14.21 25.56Mar. 14, 2001 2.814 33.57 -4.35 19.38Mar. 15, 2001 6.888 47.46 -7.95 19.38Mar. 16, 2001 6.267 49.71 -9.90 27.32

Total 33.457 279.83 -56.83 153.08

* Negative battery power indicates charging

Aggregate power consumption over the 6 days period is:

Aggregate of power consumption = (Battery Charge)+(Load Power)

= 56.83 + 153.08 = 209.91 kWh

In comparison, the amount of power generated is 279.83 kWh which

exceeds the power consumption by 69.92 kWh (33.3%). This indicates that

sufficient power is being supplied. However, these results were obtained in

relatively cool season March. Whether the balance will be maintained under a

hot condition in which cooling fan motor is operated at night is a subject of

June and September data.


46/56

43

Table 5.6: Power generation & consumption for 6 days (11-16 June, 2001)

Date


PV Power(KWh)


Load Power(KWh)

June. 11, 2001 6.567275 78.5446 -18.6046 43.10788June. 12, 2001 6.834935 81.74582 -21.1775 35.88441June. 13, 2001 6.848537 81.9085 -2.75937 43.04919June. 14, 2001 6.819213 81.55779 -19.0496 41.3766June. 15, 2001 6.715253 80.31443 -4.51376 44.09359June. 16, 2001 6.722479 80.40085 -23.6191 39.85085

Total 40.50769 484.472 -89.724 247.3625* Negative battery power indicates charging

According to June data:


= 89.724+ 247.3625 = 337.0865 kWh



sufficient power is being supplied. During these days batteries approached full

charge by 9:30 am one time, 10:30 am three times, and 11:30 am twice.

Table 5.7: Power generation & consumption for 6 days (11-16 Sep, 2001)

Date


PV Power(KWh)


Load Power(KWh)

Sep 11, 2001 6.905137 82.58544 -15.9672 40.7453Sep 12, 2001 7.203679 86.156 -11.1758 40.83458Sep 13, 2001 6.925274 82.82627 -11.7224 40.34646Sep 14, 2001 6.676439 79.85021 -7.60108 41.23146Sep 15, 2001 6.602306 78.96358 -5.81159 43.60006Sep 16, 2001 6.260965 74.88114 -3.16303 46.19723



47/56

44

According to September data:


= 55.4411+ 252.9551 = 308.4 kWh




charge by 10:30 am.

Table 5.8: Power generation & consumption for 6 days (11-16 Dec, 2001)

Date


PV Power(KWh)

Battery ChargePower * (KWh)

Load Power(KWh)

Dec 11, 2001 6.153731 73.59862 -16.6668 34.38141Dec 12, 2001 6.227577 74.48183 -14.8356 33.39027Dec 13, 2001 4.441464 53.11991 -8.96226 34.53351

Dec 14, 2001 4.980495 59.56672 -16.3693 33.30097Dec 15, 2001 3.620653 43.30301 -14.161 30.09223Dec 16, 2001 3.019826 36.11712 -23.468 15.04552


According to December data:


= 94.46+ 180.74 = 275.2 kWh


exceeds the power consumption by 65 kWh (23.6%). This indicates that


48/56

45


charge by 9:30 am.

Table 5.8, shows different six days of extremely minimum daily average tilt

irradiance values during sunshine duration of winter season.

According to 18 November 2002 data


= 8.84 + 9.30 = 18.14 kWh

In comparison, the amount of power generated is 21.06 kWh, which


sufficient power is being supplied even in the worst sunshine days (See table

5.8).

Table 5.9: Power generation & consumption for day of extremely minimum daily

average tilt irradiance values during of winter season 2002/2003.

Date Tilt Irrad

(KWh/m2)

PowerfromPV

(KWh)

Powerto

Battery

(KWh)

Powerto

Load

(KWh)

ExcessPV

Power

(KWh)

% of Excess PVPower to (Power toLoad + Power to

Battery)(%)

18/11/02 1.86 21.06 -8.84 9.30 2.92 16.1214/12/02 1.08 13.66 -4.22 6.70 2.73 24.9715/12/02 2.07 21.45 -13.18 7.78 0.50 2.3816/12/02 1.70 17.89 -10.25 6.71 0.92 5.4427/12/02 3.09 20.92 -10.19 9.03 1.70 8.8731/12/02 3.17 19.93 -9.61 8.71 1.61 8.78

14-16/12/02 4.84 52.99 -27.65 21.19 4.15 8.50* Negative battery power indicates charging


49/56

46

Table 5.10 shows the six extremely maximum daily average load power

values during the summer of 2001. In these days, it is clear that generated PV

power (KWh) is less than consumption power (KWh) for the entire sample.

Table 5.10: Power generation & consumption for extremely maximum daily average

load power values during the summer of 2001.

Date


PV Power(KWh)

Battery ChargePower * (KWh)

Load Power(KWh)

20/05/01 6.36773 76.15805 -59.7778 60.1062421/05/01 6.378059 76.28159 -56.1394 52.7672627/06/01 6.426936 76.86616 -52.9782 56.3817530/06/01 6.312202 75.49394 -49.7657 58.6357302/08/01 5.138935 61.46166 -34.7918 64.5965323/08/01 6.636386 79.37118 -46.1062 63.03397

Power generation and consumption over 6-days period for April, June,

September, October , November and December for the year 2002 are shown

in table 5.10. The data of the table indicated that sufficient power was

supplied to the greenhouse system.


50/56

47

Table 5.11: Power generation & consumption for one week data in April, June,

September , October, November and December 2002.

Date Powerfrom

PV

(KWh)

Powerto

Battery

(KWh)

Power toLoad

(KWh)

ExcessPV

Power

(KWh)

% of Excess PVPower to (Power to

Load + Power toBattery)

(%)

1-6/04/02 261 -76 128 57 28.118-23/06/02 400 -70 228 102 34.225-30/09/02 396 -77 219 99 33.413-20/10/02 460.8 -98 247.5 115.3 33.425-30/11/02 258.3 -66.3 137.9 54.2 26.613-20/12/02 222.7 -87.8 103.9 31 16.1

5.3.3 Battery Discharge Test

During the period from 10:02 am 25 June to 1:05 pm 29 June

2002 a battery discharge test was conducted to identify the discharge

load profile. The PV system was disconnected from supplying the

electrical load to the system and hence being fully dependant on

battery system to supply the load. The battery charge rate dropped

from 95% to 50% in about 100 hours continuous. Fig 5.11 shows the

state of charge of the battery system. From the test, it is concluded

that the battery storage system can provide the load with electricity

for four days (100 hours).


51/56

48

Variation of state of charge with Time

0

20

40

60

80

100

120

1 713

19

25

31

37

43

49

55

61

67

73

79

hours

stateofcharge%

Fig 5.11: Variation of state of charge with Time from 25 June to 29 Jun

.


52/56

49

6.CONCLUSIONS

The potential of using photovoltaic (PV) system to power greenhouses was

investigated in this research. The greenhouse under investigation is located at al-

Muzahmyah research station of the King Abdulaziz City for Science and

Technology (KACST). The potential harmony between the solar radiation

availability and the demand for electricity was quantified. Greenhouse was in full

operation since July 2000. Data Acquisition System (DAS) was in operation since

Nov 2000. Five plantation cycles were completed and the sixth one is in progress

and expected to complete by the end of February 2003. The performance of the

PV subsystem, battery subsystem and greenhouse cooling system were satisfactory.

Based upon the experience attained from operating this project and according

to the information and results obtained from the system, the following conclusions

can be drawn:

1. Power generation and consumption over 6-days period for April, June, and

September 2002, showed that the amount of power generation exceeded the

power consumption far more than 28%. This shows that sufficient power

is being supplied to the greenhouse.

2. Due to high salts concentration in water used for cooling, cooling pads were

clogged several times and were periodically replaced shorter than

anticipated. As the water evaporates over the cooling pads, high

concentration of salts accumulates and remains over the cooling pads. The

salt content of cooling water exceeded 1500 ppm (part per million), and

hence very little air passed through the pad. Additionally, less contact

between air and water, and hence less cooling. Clogging air channels

reduced the fan-pad cooling system ability to cool the plants during hot


53/56

50

weather and caused the fans to draw more power than anticipated. During

most of the daytimes, the averages inside air temperatures with clogged pads

ranged between 30 and 51oC, while the inside relative humidity ranged

between 8% and 30%. This adversely affected plant growth, and causedwilting to plants in the second half of the greenhouse especially when

accompanied by high solar radiation levels (10 AM to 4 PM).

3. Replacing pads clearly improved the greenhouse environment. Air

temperature and relative humidity inside the greenhouse during daytimes

were improved, ranged from 28 oC to 32 oC, and from 39.3% to 44%,

respectively. The fan-pad cooling efficiency was found to be around 73%,with 8 oC to 17.3oC reductions in temperature.

4. Electricity consumption with new pads was found to be around 22% less

than that with old clogged pads. Results also showed that the rate of

increase in electricity consumption is non-linearly related to the increase in

ambient temperatures. With clogged pads, the two fans draw very high

powers to meet the cooling requirement of the greenhouse, however,

cooling load was always higher.

5.The rate of air ventilation was found to be influential on the inside air

temperature. At daytime, and with one fan running, mean air temperature

inside the greenhouse was around 33 oC. Where as, it was 29 oC with two

fans running. The mean maximum greenhouse temperature was around 37

oC with one fan. Where as, it was 32 oC with two fans. This indicates that

using two fans reduce the mean greenhouse temperature more than 4 oC,

and the mean maximum greenhouse temperature more than 5 oC.

6. Greenhouse water consumption for cooling system was found to be

influenced by airflow rate. Using two fans increases the evaporation of


54/56

51

water during cooling process. The averages daily consumption of water with

one fan running was 2.89 m3. Where as, with two fans the daily average was

4.85 m3. The daily average consumption of water for irrigation was 2.33 m3

irrelevant to the number of fans in operation.

7.The introduction of greenhouse shading reduced the thermal stress on

plants. Also, Roof shading improved inside conditions during extreme

hours.

8. During extreme summer conditions, the greenhouse cooling system along

with shade and transpiring plants were capable of providing acceptable rang

of temperature and relative humidity inside the greenhouse. During theperiod from 9:30 to 17:30, air temperatures inside the greenhouse ranged

from 28 oC and 32 oC, compared to 38 oC to 44.2oC outside the greenhouse.

At night, inside air temperatures ranged from 21 oC to 25 oC, while the

outside temperature was between 28oC to 38 oC.

9. Heating system was capable of maintaining the inside temperatures at

acceptable limits for plants growth. For example, on Jan 2

nd

the greenhousewas maintained at an air temperature of 12 0C while the ambient

temperature was 3 0C. Most of the greenhouse heating demand occurs

during night times. The average daily consumption of diesel used for

heating the greenhouse was 42 litters.

Finally it can be concluded that the SANYO PV HIT type (Hetero junctionwith Intrinsic Thin-layer) solar cell (model HIP-G47B1 module) that was used to

power the R4-1 greenhouse showed satisfactory performance in the hot and dry

climate of al-Muzahemyah research station. Furthermore, all the other PV-power

system components showed good performance. In particular, the battery system


55/56

52

was able to supply sufficient electric power to meet the load requirement for over

than 100 hours while the PV field is disconnected.

In general, the R4-1 project operation proved that PV power is technically a

viable option for supplying electrical power to greenhouses in remote areas.


56/56

REFERENCES

Aldrich, R. A. and J. W. Bartok. 1992. Greenhouse engineering. Northeast regional agriculturalengineering service, Cooperative extension, Ithaca, NY.

Al-Helal, I. M. 2001. A survey Study of Cooling Pads Clogging Problem for Greenhouses andPoultry Buildings in Central Region of Saudi Arabia (In Arabic). Research Bulletin No. 105.Agricultural research center College of Agriculture King Saud University.

Al-Helal, I. M. and H. S. Al-Tweejre. 2001. Evaporative cooling for palm dates fiber pads andcross-flutted cellulose pads under arid conditions (In Arabic). Misr Journal of AgriculturalEngineering, Vol. 18 No. (2): 469-483.

American Society of Agricultural Engineers (ASAE). 1994. ASAE Engineering Practice 406.1,p.565-568. ASAE Standards 1994. ASAE, St. Joseph, MI. 49085

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). 1983.Evaporative air-cooling equipment, Chapter 4. Equipment Handbook. ASHRAE, Inc.,Atlanta. GA30329.

Hellickson, M. and J. N. Walker. 1983. Ventilation of agricultural structures. An ASAmonograph, No:6, published by ASAE, St. Josepp, MI. 49085.

Humaeida, M. A. and F. S. Mohammad. 1993. Meteorological data for envieronmental andagricultural design in Riyadh region. Research bulletin No. 29. Agricultural ResearchCenter, College of Agriculture, King Saud University.

Kittas, C., T. Bartzana and A. Jaffrin. 2001. Greenhouse evaporative cooling: measurement anddata analysis. Transactions of the ASAE, 44(3):683-689.

Ministry of Agriculture and Water. Agriculture Statistical Year Book. Vol. 12, Riyadh, Kingdomof Saudi Arabia, 1998.

Ministry of Planning. Statistical Year Book. Vol. 34, Riyadh, Kingdom of Saudi Arabia, 1998.

Montero, J. I., T. H. Short, R. B. Curry, and Bauerle, W. L. 1981. The influence of various waterevaporation systems in the greenhouse environment. ASAE. Paper No. 81-4027.

Renewable Energy Outlook: Vying For Market Share, World Markets Research Centre,2001,

http://www.worldmarketsanalysis.com/InFocus2002/articles/global_energy.html)

Walker, J., 1965. Predicting temperature in ventilated greenhouses. Transaction of the ASAE8(3): 445-448.

Date post:	21-Feb-2018
Category:	Documents
Upload:	restu-oktapiana
View:	215 times
Download:	0 times

Optimization of Solar POwer Generation for Desert Climate Site Refinery

Documents