Final Project for Photovoltaic Cell class

A Proposal for Solar Grant

(Cost Estimation for Providing Electricity for 100 Village Houses in Tanzania)

Jonathan Kenneth Rhyne

Younes Sina

Huidong Zang

Sabina Nwamaka Ude

Mary Diane Waddle

PROPOSAL FOR SOLAR GRANT

To produce electricity from the sun for domestic use requires a careful

selection of materials to ensure reliability, dependability and affordability. Many

factors need to be considered when choosing the right solar components to provide

uninterrupted power. These factors include: the right choice of PV panels with good

efficiency and low cost, knowledge of the sun insolation of the area in question and

the best tilt to capture this energy, amount of batteries needed for back-up during

cloudy days when the sun rays are blocked, the right inverters and controllers to

work with your system, site selection to avoid shading, cost of labor for initial

installation and subsequent maintenance, etc. Consideration of these factors entails

careful calculations and wise selection of the appropriate type and number of

components for optimum power production.

1. INTRODUCTION

1.1. Photovoltaic cells

Photovoltaic (PV) power systems convert sunlight directly into electricity. A

residential PV power system enables a homeowner to generate some or all of their

daily electrical energy demand on their own roof, exchanging daytime excess power

for future energy needs (i.e. nighttime usage). The house remains connected to the

electric utility at all times, so any power needed above what the solar system can

produce is simply drawn from the utility. PV systems can also include battery backup

or uninterruptible power supply (UPS) capability to operate selected circuits in the

residence for hours or days during a utility outage. Photovoltaic power offers a proven

and reliable source of electrical power for remote, small-scale facilities. PV systems turn

sunlight directly into electricity for use. Since there are typically no moving parts in PV

systems, they require minimal maintenance. While often more expensive than other

renewable technologies, the modularity of PV systems and the broad availability of the solar

resource, sunlight, often make PV the most technically and economically feasible power

generation option for small installations in remote areas. The initial investment in a PV

system typically accounts for most of its lifetime acquisition, operation and maintenance

costs. The cost of a PV system rises in direct proportion to the total size of the loads.

1.2. Location

Due to energy losses when transporting electricity over distances, especially at the low

voltages typical of small PV projects, PV systems should be located within a reasonable

distance of the point of energy use. Fortunately, PV modules can be placed anywhere the

sun shines, including the roof of a building. Care must be taken to secure the modules in

areas of high winds to prevent loss or damage. PV modules are very sensitive to shading.

The shading of 5% to 10% of the surface area of a module can lead to a drop in power

output of 30% to 50% or more.

1.3. Operation and Maintenance (O&M)

The minimal O&M requirements of a PV system make this technology well suited for isolated

locations and rural applications where assistance may be infrequently available. Preventive

maintenance, such as routine system cleaning and inspection, are always recommended.

The most common maintenance required for typical PV systems is the periodic addition of

distilled water to the batteries when flooded batteries are used. More expensive systems,

using sealed batteries, can run for extended periods (months) without user intervention.

When PV systems are used and managed by community organizations or system owners,

there is a critical ongoing need for training and/or assistance in system maintenance and

troubleshooting. Sometimes the malfunctioning of a small fuse can be the reason for a

system failure. In this case, a routine inspection by an experienced technician could reveal

what caused the original problem that burned the fuse.

1.4. Environmental Impacts

A PV system produces negligible pollutants during normal operation. The main

environmental impact associated with PV systems comes from the failure to properly

dispose of batteries used in conjunction with the arrays.

1.5. Costs

The cost of a standalone PV system varies greatly depending on local market conditions and

the quality of the equipment used. While the PV modules themselves may cost about

US$7.00 per Watt, the total upfront investment cost of a PV system, including batteries,

inverter, installation, etc., typically is about US$20.00 per Watt installed. Costs per installed

Watt depend on system size, the installation site and component quality. Smaller systems

(less than 1 kW) tend to be at the higher end of the cost range. O&M costs for small-scale

PV systems are generally low, at less than 1% of initial investment costs annually. If poor

quality BOS components are used, these may fail and lead to higher costs to diagnose the

problem and replace the faulty components.

1.6. Viability

The PV option is most likely to be competitive when tens or hundreds of peak Watts are

required in remote or hard-to-reach areas. Depending on the situation, PV may also be

competitive when only a few kilowatts of energy are needed. In many rural areas, diesel or

gas generators and PV systems are the only viable alternatives. Unlike generator sets, PV

systems are quiet and do not generate pollution. With proper design, installation and

maintenance practices, PV systems can be more reliable and longer lasting than generators.

The modularity of PV systems enables systems to be well matched to the demand. When

there are multiple small sites requiring electrification, PV is best installed in the form of

independent systems sized to match each individual load.

PV systems are more likely to fail in areas that lack the commercial and technical

infrastructures needed to ensure long-term sustainability. This infrastructure includes PV

markets that are active enough to sustain the field over time, including suppliers of

warranted PV system components, installers and maintenance technicians.

2. SYSTEM DESIGN CONSIDERATIONS

2.1. Basic Principles for Designing a Quality PV System

1. We selected a packaged system that meets the owner's needs. Customer criteria

for a system may include reduction in monthly electricity bill, environmental benefits,

desire for backup power, initial budget constraints, etc. The size and orientation of

the PV array is adjusted to provide the required electrical power and energy. The off

grid system selected for the village guarantees the people of the village electricity

during the entire year including the rainy season.

2. We are ensured the roof area or other installation site is capable of handling the

desired system size.

3. We specified sunlight and weather resistant materials for all outdoor equipment.

4. We located the array to minimize shading from foliage, vent pipes, and adjacent

structures.

5. We designed the system in compliance with all applicable building and electrical

codes.

6. We designed the system with a minimum of electrical losses due to wiring, fuses,

switches, and inverters.

7. We properly housed and managed the batteries and inverter systems.

2.2. Basic Steps for Installing a PV System

1. We ensured the roof area or other installation site is capable of handling the

desired system size.

2. We realized that roof mounting is better than a solar field; therefore we verified

that the roof is capable of handling additional weight of PV system.

3. We properly sealed any roof penetrations with roofing industry approved sealing

methods.

4. We Installed equipment according to manufacturers' specifications, using

installation requirements and procedures from the manufacturers' specifications.

5. We properly grounded the system parts to reduce the threat of shock hazards and

induced surges.

2.3. Typical System Designs and Options

There are two general types of electrical designs for PV power systems for homes;

systems that interact with the utility power grid and have no battery backup

capability; and systems that interact and include battery backup as well. The village

has an off grid system with large battery banks so the people of the village have

electricity during nights as well as the rainy season.

2.4. Typical System Components

The village has typical system components as follows:

PV Array

A PV Array is made up of PV modules, which are environmentally sealed collections

of PV Cells- the devices that convert sunlight to electricity. Often sets of four or more

smaller modules are framed or attached together by struts in what is called a panel.

This panel is typically around 20-35 square feet in area for ease of handling on a

roof. This allows some assembly and wiring functions to be done on the ground if

called for by the installation instructions. The solar panel is consisted by series or

parallel connected solar cells. Thus, the work principle of the solar panel is same as

the principle of single solar cell which generates electricity by photovoltaic effect. The

photovoltaic effect refers to photons of light knocking electrons into a higher state of

energy to create electricity. Moreover, the materials presently used for photovoltaic

include mono-crystalline silicon, polycrystalline silicon, microcrystalline silicon,

cadmium telluride, and copper indium selenide/sulfide.i And the efficiency is around

10%-20%.

The PV array used for each home in this village is a roof mounted system.

The panels will be attached on the north side of each home flat against the roof. The

angle on the roof is 20°, so this places the panels at 20° above the horizon facing the

equator. The array on each house will be a total of 78 panels split between the two

sections of the roof leaving one side with a 4x10 panel grid and the other a 4x10 grid

that is lacking two panels at the top. The panel we chose was a 180W panel from

China with a 16% efficiency. The panels cost $283 dollars each. A detailed price

assessment will be discussed later.

Balance of system equipment (BOS)

BOS includes mounting systems and wiring systems used to integrate the solar

modules into the structural and electrical systems of the home. The wiring systems

include disconnects for the DC and AC sides of the inverter, ground-fault protection,

and overcurrent protection for the solar modules. Most systems include a combiner

board of some kind since most modules require fusing for each module source

circuit. Some inverters include this fusing and combining function within the inverter

enclosure.

DC-AC inverter

This is the device that takes the dc power from the PV array and converts it into

standard AC power used by the house appliances. It is a necessary component in

the system, because the solar panels and the batteries are DC source power, but the

load is AC mode. Basically, the inverter can be divided by two types, one is stand

along inverter and the other is grid tie inverter. The off grid inverter is used in isolated

solar power system. And the inverter has the following functions: Overload

protection, Sort circuit protection, the over-voltage protection, overheating protection.

We chose a 220V 50Hz 3kW inverter/charge controller from China. This unit has the

inverter and the charge controller built into one unit. Each unit costs $1,757. Every

house will have one active unit and another deactivated united on site for a

replacement after the 5 yr life of the active unit is exceeded. The peak load that each

house will experience throughout the day is 1.6kW which is within the limits of the

unit.

Metering

This includes meters to provide indication of system performance. Some meters can

indicate home energy usage.

Battery backup system components

Because all of the energy produced by the solar modules at any given time need to

be stored as chemical energy, thus a battery bank is installed to collect and store

excess energy to use when needed. The batteries used in solar applications are

usually specialized, deep-cycle lead acid batteries.

The battery backup system include of the following components:

1. Batteries and battery enclosures

2. Battery charge controller

3. Separate subpanels for critical load circuits

This by far is the most expensive section of the project. The batteries themselves are

cheap, $168, however the quantity needed to sustain each house through the rainy

season is tremendous, 862 batteries per house. This totals 86,200 batteries for the

village at a cost of 14.5 million dollars! This number could be tripled if the batteries

only last 3 yrs and the grant is to provide power for 10 yrs. Since we are only

discharging the batteries to their rated depth of discharge once a year, we are

hoping that the batteries will last longer than this.

Charge controller

A charge controller, charge regulator or battery regulator is one of the necessary

components in the solar power system. It limits the rate at which electric current is

added to or drawn from electric batteries. The most important factor of charge

controller is preventing the overcharging that may prevent against overvoltage, which

can reduce battery performance or lifespan, and may pose a safety risk. It may also

prevent completely draining ("deep discharging") a battery, or perform controlled

discharges, depending on the battery technology, to protect battery’s lifetime. The

terms "charge controller" or "charge regulator" may refer to either a stand-alone

device, or to control circuitry integrated within a battery pack, battery-powered

device, or battery recharger.

This photovoltaic system is designed as an off-grid system that will withstand

extreme temperature variations. This off-grid system is in Africa where its proximity

to the equator and height influences the intensity of the sun. The more intense the

sunlight, the more watts the solar panels will produce. This effect will increase the

voltage and will potentially damage the batteries. The batteries are of major

economic concern for an off-grid system and their importance is paramount. A

charge controller is used to regulate the charging voltage to the batteries.

Charge controllers use a three stage cycle as bulk, absorption, and float. The

graph below will illustrate the relationship between amps and voltage.

Fig1. Relationship between amps and voltage through the charging cycle

There are two multistage charge controllers used in PV systems; pulse width

controllers (PWM) and maximum power point tracking (MPPT). Pulse width

controllers maintain the constant voltage need, while the mppt match the battery

voltage to the output of the solar array. The controller’s primary purpose in a PV

system is to handle the maximum current produced by the solar array. The

considerations in selecting a controller are as follows:

High/Low voltage disconnect

Temperature Compensation

Low voltage warning

Voltage meters/reverse current protection

These considerations must be analyzed to insure the batteries and the PV system is

protected.

Fuse, wire and switches

The function of fuse is to protect the solar power system and the standard of

choosing fuse, wire and switches need to consider the value of current used in the

situation of maximum output. The wire chosen for this project was tin plated copper

wire that costs $0.805 per meter. We will require 5000m of wire for the complete

system in the village.

Other components

Utility switch

2.5. PV Installation

There are several ways to install a PV array at a residence. Often the most

convenient and appropriate place to put the PV array is on the roof of the building.

The PV array may be mounted above and parallel to the roof surface with a standoff

of several inches for cooling purposes. In this project we decided to install the PV

arrays on the roof of the houses to reduce the cost of wiring and also to reduce the

risk of damage from accidental human and animal interference. The batteries and

inverter/charge controller will be housed in a 25ftx25ftx8ft basement to the right of

each house shown in figures 2.5.1 and 2.5.2.

Figure 2.5.1 black square is the house, the red the basement, the blue lines are the distance between

houses, and the arrows say there are ten rows with ten columns.

Figure 2.5.2 gray is the walking space, the blue is the battery rows and the green is the inverter

There will be five rows of batteries that are that are 7 batteries high and 25 batteries

long. The inverter will be in the lower corner depicted by the green square. This

space also gives extra space for the spare inverters and panels.

3. Estimating System Output

PV systems produce power in proportion to the intensity of sunlight striking the solar

array surface. The intensity of light on a surface varies throughout a day, as well as

day to day, so the actual output of a solar power system can vary substantial. There

are other factors that affect the output of a solar power system. These factors are

standard test condition for modules, temperature, dirt and dust, mismatch and wiring

losses, and DC to AC conversion losses.

The first step in estimating the power required for the village was to calculate the

load each house has per day. This number was figured from the numbers below.

• Lights

– 25W*10lamps*12h/day = 3kWh/day

• Refrigerator

– 700kWh/yr*yr/365days = 1.91781kWh/day

• Television

– 125W*5h/day + 15W*19h/day = 0.91kWh/day

• Air Conditioner

– 750W*24h/day = 18kWh/day

• Computer

– 200W*5h/day + 10W*19h/day = 1.19kWh/day

• Washing Machine

– 0.25kWh/wk*wk/7days = 0.03572kWh/day

• Total = 25.05353kWh/day/house

So each house uses ~25kWh/day. Next we found the insolation for the latitude and

longitude of the village using the NASA surface meteorology and solar energy

website. This site is very useful and gives virtually every parameter needed to

perform any calculation and provides long term averages of 22 yrs for the data. The

data we used is selected in red below in figure 3.

Figure 3 solar insolation at 18° averaged for each month

The slope of the roof is 20°, so we took the data for 18° above the horizontal facing

the equator. We used the lowest insolation month to figure the number of panels.

The lowest month is June with a value of 4.55kWh/sq.m/day which is in winter. The

calculation was: 25.05353/(4.55*0.18*0.4) which gives 77 panels. The 0.18 is the

watt rating of the panel in kilowatts and the 0.4 is for total system efficiency. The total

be seen in table 3.

Table 3 the red numbers are the individual efficiencies used and the blue number is the total

Average PV System Component Efficiencies

PV array80-85%

Inverter80-90%

Wire97-98%

Disconnects, fuses98-99%

Total grid-tied PV system efficiency60-75%

New batteries (roundtrip efficiency)65-75%

Total off-grid PV system efficiency (AC)40-56%

The number of batteries was found by taking the total amount of charge required to

sustain the house for the 3 month rainy season. It was given that each house

receives 2 days of sunshine per week at random during the 3 months. Looking at the

calendar, it is likely that there will be a total of 9 days total sunshine in both the

months of Aug. and Sep. while Oct. will likely have 8. This results in a total of 26

days, the rest of the days will be discharging from the battery. The calculations for

this can be seen in figure 3.1 below.

Figure 3.1 excel calculations used to determine the system size

The 2nd row is the insolation per month, the 3rd is the excess kWh produced, the 4th

the sunny days in that month, and the 5th the total excess kWh produced during that

month. The numbers in the 6th row are the sum of the corresponding color numbers

above, the purple is the pre-spring months and the blue the post-spring ones. The

pink numbers in the 7th row are the total kWh discharged from the batteries for that

month and the total below them. The gray is the total kWh held in the 862 batteries

at 80% depth of discharge. It is slightly above the pink total discharged over the

spring months. The orange numbers in the last row are the kWh added back to the

batteries. The middle number is a sum of the other two which is greater than the pink

discharge total. This means that the batteries are fully recharged for the spring

months every year. It turns out that the panels needed to be increased to 78 in order

for this to happen. The batteries are fully discharged to 80% and recharged once a

year.

4. Cost calculations

4.1. Cost of components

The cost for each components and the shipping information is listed in follow. Fig.4.1

shows the cost breakdown of components.

4.1.1 .Controller and inverter (integrated system)

Company: Shanghai Jinxian Solar Tech Co. Ltd http://shayanjian.cn.alibaba.com/

Tel: +86 21 5227 4750 (Mr. Jianghong Sha)

Model: HT22030J7

Output: 220V 50Hz 3000W

Price $1757

Size after packing 1m*1m*2m

Due to the peak hour power needed in a single house 1655Wh

The total controller and inverter integrated system would be

2 unit per house/ one active and one replacement with 4 spares

The total cost for controller and inverter integrated system: $1757*204=$358,428

4.1.2. Solar wires

Company: Shanghai Yingqiang Electronic Co. Ltd

http://liyoch.cn.alibaba.com/

Tel: +86 21 5947 0669 (Mr. Yongchun Li)

Model: PV1-F TIN PLATED COPPER WIRE

Brand: Yongben

Price: $0.805/m

The length of wire is calculated based on the map in the assignment, assuming the

height of house is 4m. (5000m is needed)

So the total cost for wire is 5000m*0.805/m=$4025

4.1.3. Battery

Company: Shenzhen Haonaite Power Co. Ltd

http://detail.china.alibaba.com/company/detail/yhz9394.html

Model 12V200AH

Size: 522*238*218（mm）

Price: $158 plus $10 for box

# Batteries per house 862

The total cost $168*862*100= $14,481,600

4.1.4. Fuse and switches

Fuse-Company: Shenzhen Weilangte Electronic Co. Ltd

http://shenzhenweilangte.manufacturer.globalsources.com.cn/si/6008828299332/

Homepage.htm

Model: UDA/UDA-A

Max current: 10A; Max voltage: 250V

Size: 5mm*20mm

Price: $0.02

# fuses: 500 PCS

The total cost $0.02*500= $10

Switch-Company: Zhengtai electronic Co. Ltd.

http://www.chint.net/index.php

Model: NB1-63 220V 50Hz

Price: $3.5

# fuses: 300 PCS

The total cost $300*3.5= $1,050

4.1.5. Panels

Table4.1.5. shows some panel providers from different countries with deferent types,

models, dimension efficiency and price. The GOD Company from China is selected

as the panel provider for the village.

Panel Cost: $283x 7800=2,207,400

4.2. Transportation Cost

4.2.1 Shipping from Shanghai to Tanga

40 gp container: 12.01m*2.33*2.38m Price: $630

Company: Sinotrans Container Lines Co., LTD

Website: http://www.sinolines.com/

4.2.1.1. Panels

The size of panel after packing approx: 1.8m*0.9m*0.1m

# of panels 78*100=7800 pieces

So approx 300 panels per container

# of containers for panels: 7800/300=26

# cost for shipping panels = $630*26= $16,380

4.2.1.2. Controller and inverters

The size of container is 12.01m*2.33*2.38m

The size of controller and inverter is 1m*1m*2m

So each container can load 12 systems

# Containers = 204/12 =17 containers

Cost for controller and inverter is $630*17 = $10,710

4.2.1.3. Wires, Fuses and Switches

1 container is enough.

# Cost = $630

4.2.1.4. Batteries

According to the size of container and batteries

Each container can load 2400 batteries

So # container is 86200/2400= 36

Cost for shipping batteries

# 36*$630= $22680

Total cost for shipping

$16,380 + $10,710 + $630 + $22,680 + $1,060= $51,460

Fig.4.2. shows the cost breakdown for the shipping of the components.

4.2.2. Transportation cost by truck

Total cost: $516,600

• 1300 trips/2$ per mile/ 216 miles

Fig.4.2.2 shows the distance from the port to the village that is the basis of shipping

by truck.

Fig.4.2.2. Distance from the port to the villageFig.4.Fig.

i4.3. Site Preparation cost

4.3.1. Site Access Clearing

Labor: 10 men X 20 days X 8hrs X 5$ = $8,000

Tools: 10 saws X 20 days X 10$ = $2,000

Bulldozer: 30 days X 500$ = $15,000

4.3.2. Battery bank place

Hole creation for battery bank : 20 days X 500$ = $10,000

Basement : $500 per house X 100 homes = $50,000

4.3.3. Total site preparation cost Total cost = 60,000(basement)+15,000(bulldozer)+2000(chain saw)+8000( labor)=$185,000

Fig.4.3.3.1. shows the cost breakdown for site preparation.

Fig.4.3.3.2 shows a view of the region. The red line shows the road access to the village .

Fig.4.3.3.2. A view of the region(the red line shows the road access to the village)

4.4. Training cost

Training cost for labors - 9 people :$10,800

Engineer for training :$ 7,200

Labor for installing panels :$24,480

Fig.4.4. shows cost breakdown of training and installation

Labor training Engineers for training Instalation cost0

5000

10000

15000

20000

25000

10800

7200

24480

Fig.4.4. Cost breakdown of training and installation

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Fig.4.1 Component cost breakdown

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Fig.4.2. Cost breakdown for the shipping of the components

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Fig.4.3.3.1. Cost breakdown for the site preparation

4.5 .Total cost

Table 4.5.1 and 4.5.2 show a summary of the costs .

Table4.5.1. Cost of components

Table4.5.2. Cost for transportation, installation, training

Panels – $2,210,2307,800 panels

Controller/Inverter – $196,778112 units

Batteries – $14,616,00087,000 batteries(worst case/times # by 3)

Wire – $4055000m

Site Clearance – $25,000(minus lumber sales)

Battery storage – $110,000Hole & Material

ShippingTruck – $516,6001300 trips/2$ per mile/ 216 miles

Boat – $43,620$630 per container/ 69 containers

InstallationPanels – $24,480Engineer – $58,320

TrainingLaborors – $10,800Engineer – $7,200Cleaning – $146,000

Total – $17,965,433

Country

CompanyTypeModel

DimensionPower

Voltage (Vpm)

Efficiency

Price (RMB)

Lifetime (y)Max. VMax. I

USASharppolycry

stalND-

130UJF

662*1499*46m

m133W17.4V13.10%2560015

ChinaSuntec

hpolycry

stal

STP130D

-12/TEA

1482*676*35m

m13017.425100020

ChinaSuntec

hpolycry

stal

STP135D

-12/TEA

1482*676*35m

m13517.525100020

Solar world

Mono-crystall

ineSW230

1675*1001*34

mm23029.6$6002560015

ChinaLeixinpolycry

stal689*14

80140w36V13Y*14

0W=253.88A

ChinaJinnuo

Mono-crystall

ineKD-

M1801580*808*35180W36.314

14.5Y*180W258005.61A

ChinaGOD

Mono-crystall

ineGOD-180

1580*808*351803616

11Y*180=$28325

ChinaLeixinpolycry

stal200w*1

02000w

ChinaXinan

Mono-crystall

ineXA2301580*1060*5023046.4V254.96

XA2401580*1060*5024046.9V255.11

XA2501580*1060*5025047.2V255.3

ChinaXuhuipolycry

stalXH-

Sp2201640*992*5021028.98

14.87*210=312

4257.25

22029.613124257.55

23029.43124257.82

ChinaSULO

Mono-crystalline

sol180s-24d

1580*808*35

ChinaJieyupolycrystalTY-160

1581*808*40160W34.516

RMB888825700V4.46

Table4.1.5. Data about panels