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CHAPTER 06

Solar Home System

6.1 Introduction:

Solar photovoltaic’s is one of the most cost effective means to provide small amounts of electricity in

areas without a grid. Especially when people live in scattered homes, the costs of alternatives to provide

electricity are usually prohibitively high. Solar home systems (SHS) are small systems designed to meet

the electricity demand of a single household. A Solar home system always consists of one or more

photovoltaic (PV) modules, a battery, and a load consisting of lights, and one or more sockets for radio,

television or other appliances. A battery charge regulator is usually added to control charging and

discharging of the battery.

6.2 Background:

Early in 1999, about one million solar home systems were in use in the world, and this number is rapidly

growing. This is a strong indication that this technology provides desired services to rural households in

non-electrified areas. However, technical and non-technical problems often arise, which can hamper the

further wide-scale application of solar home systems in rural electrification.

Despite of large potential of solar system in Bangladesh, utilization of solar energy has been limited to

traditional uses such as crop and fish drying in the open sun. Solar PV are gaining acceptance for

providing electricity to households and small businesses in rural areas. In 1988, Bangladesh Atomic

Energy Commission (BAEC) installed several pilot PV systems. The first significant PV-based rural

electrification program was the Norshingdi project initiated with financial support from France. Three

Battery charging stations with a total capacity of 29.4kWp and a number [36] of standalone SHSs with a

total capacity of 32.58kWp were installed. REB owned the systems and the users paid a monthly fee for

the services. Since 1996, penetration of SHSs increased rapidly, mainly due to the efforts of GS, which

sells PV systems on credit to rural households through its extensive network. Several other NGOs such as

CMES and BRAC are also engaged in promoting PV technology. PV modules are generally imported,

while there are a few private companies manufacturing PV accessories [36].

According to a World Bank-funded market survey, there is an existing market size of 0.5 million

households for SHSs on a fee-for-service basis in the off grid areas of Bangladesh. This assessment is 93

based on current expenditure levels on fuel for lighting and battery charging being substituted by SHSs.

Also it has been observed that in most developing countries, households typically spend no more than 5%

of their income on lighting and use of small appliances. By this measure, about 4.8 million rural

Bangladeshi households could pay for a SHS. At present the national grid is serving only 50% of the

nearly 10,000 rural markets and commercial centers in the country, which are excellent market for

centralized solar photovoltaic plants. Currently private diesel gen set operators are serving in most of the

off-grid rural markets and it has been found that 82% of them are also interested in marketing SHSs in

surrounding areas if some sorts of favorable financing arrangements are available.

6.2.1 Progress with Solar Home System Installation

Table-6.1: Progress with solar home system installation [36].

Partner Organization Number of solar home system installed

Grameen Shakti 269,010

BRAC Foundation 53,103

RSF(Rural Services Foundation) 45,864

Srizony Bangladesh 11,933

UBOMUS(Upokulio Biddutayan O Mohila

Unnoyon Samity)

8,447

BRIDGE 6,210

COAST Trust 3,483

Integrated Development Foundation 4,305

Centre for Mass Education and Science 3,237

Shubashati 2,743

Hiful Fuzul Samaj Kallyan Sangstha 7,155

TMSS(Thengamara Mohila Sabuj Sangha) 2,240

PDBF(Palli Daridro Bimochon Foundation) 2,305

PMUK(Proshika Manobik Unnayan Kendra) 770

Other 388

Total 4,21,193

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Table-6.2: Division wise installation of solar home system [36].

Division Number of Solar Home System Installed

Barisal 64,734

Chittagong 86,195

Dhaka 99,655

Khulna 58,107

Rajshahi 59,280

Sylhet 53,222

Total 421,193

14%

21%

22%

17%

8%

6%

12%

BarisalChittagongDhakaKhulnaRajshahiRangpurSylhet

Fig. 6.1: Distribution of the SHSs (Solar Home System) in seven divisions in Bangladesh [39].

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6.3 Solar home system Types:

Solar home system are generally classified according to their function and operational requirements, their

component configuration and how the equipment is connected to other power sources and electrical

loads.shs systems can be designed to DC or AC power service, can operate interconnected with or

independent of the utility grid and can be connected with other energy sources and energy storage system.

Two principal classifications are grid connected and stand alone system.

6.3.1 Grid connected solar home system:

PV Grid connected systems are worldwide installed because it allows consumers to reduce energy

consumption from the electricity grid and feed the surplus energy back to the grid. The system may use

battery or not. The PV Grid connected system are used in buildings that are already hooked up to the

electrical grid. The PV system is connected is connected to the consumers breaker panel and if the power

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Solar PV System

Grid connected System Stand –alone System

generated is greater than the load, the power runs reverse through the meter and runs it backwards. this

system is also called utility-interactive PV system or net metering system.

Among the solar PV system in the world 75% is grid connected system. The trend is popular because

when system produces more power than the required, the excess power is feedback into the grid and such

solar PV home system can work as a retailer. When system doesn’t produce enough required power the

required power can be obtained from the grid.

6.3.1.1 Operating Principal:

The primary component in gird connected solar home system is the inverter or power controlling unit

(PCU). PCU converts the DC power produced by the PV array into ac power consistent with the voltage

and power quality requirements of the utility grid and automatically stop supplying power to the grid

when the utility grid is not energized. a bidirectional interface is made between the PV system ac output

circuits and the electric utility network, typically at an onsite distribution panel service entrance. This

allows AC power produced by the PV system to either supply on site electrical loads or back feed the grid

when the PV system output is greater than the onsite load demand. At night and during other periods

when electrical loads are greater the PV system output, the balance of power is required by the loads is

received from electric utility. This safety feature is required in all grid connected solar home system and

ensures that PV system will not operate and feed back into the utility grid when the grid is down for

service or repair.

6.3.2 Stand alone solar home system:

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Fig. 6.2: Stand alone solar home system

PV systems that are not connected to the utility grid are called remote or stand alone system. In

Bangladesh most solar home system are stand alone. These systems are sized large enough to meet all the

electrical needs of the house, rather than just a portion as the common grid connected system. To reduce

the size and thus cost of the system the home owner must be very efficient in electrical energy use.

Solar Stand alone PV systems are designed to operate without utility grid and are generally designed and

sized to supply certain DC and AC electrical loads. Stand alone systems may be powered by a PV array

only or may use utility power as a backup power source.

6.4 Typical components for a solar home system:

Typical components used in solar home systems are:-

1. Solar Module

2. Module support structure

3. Inverter90°22'16.8"E

4.

5. Charge controller

6. Battery bank

7. AC And DC loads

8. Balance of system

I. Array combiner box

II. Properly sized cabling

III. Fuses

IV. Switches

V. Circuit breakers

VI. Meters

6.4.1 Solar Modules:

Solar PV modules are the most reliable component of a solar home system. Standards have been

formulated (IEC 1215), and modules can be certified. For the certification, tests have to be passed

regarding: visual inspection, performance at Standard Test Conditions (STC), measurement of

temperature coefficient, measurement of nominal operating cell temperature (NOCT), performance at low

radiance, outdoor exposure, thermal cycling, humidity freeze, damp heat, and robustness of termination.

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In the design it should be noted that manufacturers have been known to supply modules with peak

wattage about 10% lower than the nameplate capacity. In addition, the temperature effect on modules can

be critical in some areas. In full sun, the module temperature can increase to 70C. Normally a quality

module has a temperature coefficient of about –2.5mV/ C/cell. At 70C a 36-cell module should be able to

charge the battery sufficiently. Because a protection diode is connected in series with the module in most

systems, the voltage drop across this diode should also be taken into account [48].

6.4.2 Module Support Structure: 23°45'14.6"N

The support structure for the PV-module(s) should be corrosion resistant (galvanized or stainless steel or

aluminum) and electrolytically compatible with materials used in the module frame, fasteners, nuts and

bolts. The design of the support structure should allow for proper orientation of the module, tilt and

expansion of the system’s capacity. Roof mounting may be preferable to ground or pole mounting since it

is less costly, and requires less wiring. The module support should be firmly attached to the roof beams

and not loosely attached to the roof tiles. The module should not be placed directly on the roof but 10-50

cm above the surface itself, to allow cooler and therefore more efficient operating conditions. If the

module is mounted on a pole, the pole should be set firmly in the ground and secured with guy wires to

increase rigidity. Pole mounted modules should be accessible for cleaning but high enough above the

ground to discourage tampering [48].

6.4.3 Inverter or DC to ac converter:

The use of DC/AC inverters in small solar home systems is rapidly growing. Hence it is a worthwhile

exercise to consider the advantages and disadvantages of using these devices and also for what purpose

they can be used.

Firstly, the most common applications of DC/AC-conversion can be listed:

Television many people in rural areas built up savings in order to buy a color television,

sometimes with a satellite dish.

Lighting in some rural areas standard 230Vac fluorescent lamps are used instead of the

special 12Vdc fluorescent lamps because they are widely available.

Fan in tropical areas a fan is often desired. This is a luxury item, which usually bought only

after a television set is obtained. This device consumes a lot of energy, so it can only be

incorporated in larger systems [48].

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Refrigerators the demand for refrigerators is growing, especially in areas where people have

already worked with solar energy for some time.

The use of a DC/AC-converter for these devices is theoretically rather useless. DC/AC-converters have an

efficiency of approximately 85%. Downwards AC/DC-transformation always has energy-losses also, in

the order of 90% efficiency. In total it means an unnecessary energy-loss of 100 %-( 90%×85%) = 23%.

At the present time there are many types of television sets, satellite receivers and fluorescent lamps

operating at 12Vdc. Solar energy is relatively expensive, so devices that are used in combination with a

SHS should be selected carefully.

6.4.4 Charge controller:

The charge and load controller prevents system overload or overcharging. For safe and reliable operation,

the controller design should include:

Low-voltages disconnect (LVD).

High voltages disconnect (HVD), which should be temperature-compensated if wide variations in

battery temperature are expected. Temperature compensation is especially important if sealed

lead-acid batteries are used.

System safeguards to protect against reverse polarity connections and lightning-induced surges or

over-voltage transients.

A case or cover that shuts out insects, moisture and extremes of temperature.

To enhance the maintainability and usability of the solar system, the controller should:

Indicate the battery charge level with a simple LED display or inexpensive analogue meter.

Three indicators are recommended: green for a fully charged battery, yellow for a low charge

level (pending disconnect), and red for a ‘dead’ or discharged battery.

Be capable of supporting added modules to increase the system’s capacity.

Be capable of supporting more and bigger terminal strips so that additional circuits and larger

wire sizes can be added as needed (this is necessary to ensure that new appliances are properly

installed) [48].

Have a fail-safe mechanism to shut down the system in the case of an emergency and to allow

the user to restart the unit.

Additional design considerations are:

Low quiescent current (own consumption).

A sturdy design to withstand the shocks and vibrations of transport.

A sufficiently high lifetime, preferably longer than 5 years.

Simple visual information on the casing should make the manual (almost) obsolete.

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The charge controller could be equipped with a boost charging function to increasing the lifetime of the

battery. Once every month or so, the battery is temporarily allowed to pass the high voltage disconnect

setting. The resulting gassing will lead to cleaning of the battery plates and reduces stratification of the

battery electrolyte.

Another optional feature in the design of an advanced battery charge regulator is pulse-width modulation

(PWM). To charge the battery fully, a constant voltage algorithm is applied when the battery is almost

full. This can be achieved with pulse width modulation.

6.4.5 Battery:

The most commonly used battery in solar home systems is a lead-acid battery of the type used in

automobiles, sized to operate for around three days. Automotive batteries are often used because they are

relatively inexpensive and available locally. Ideally, solar home systems should use deep-cycle lead-acid

batteries that have thicker plates and more electrolyte reserves than automotive batteries and allow for

deep discharge without seriously reducing the life of or damaging the battery. In a well-designed solar

home system, such batteries can last for more than five years [48].

For a typical small PV system the initial investment cost has to be kept low and the car batteries, truck

batteries, solar batteries can be recommended in this order. In practice of course the local availability of

batteries will also be a decisive factor. Therefore car or truck batteries are the best option in some

developing countries where no other batteries are available.

6.4.5.1 Temperature effect on capacity of the battery:

The nominal capacity is normally measured at 20C battery temperature and down to a certain fixed cut off

voltage of the battery. In cold climates the usable capacity may be significantly reduced, as low

temperatures will slow down the chemical reactions in the battery. This will result in a useable capacity at

for example minus 10C battery temperature of only 60% of the nominal value at 20C. The capacity is still

there if the battery is heated to 200C but at low temperature one cannot utilize the full amount. When

possible the battery should therefore be placed indoors or otherwise sheltered from low temperatures by

insulation or perhaps even placed in the ground if any other heat sources are not available. Seasonal

storage containers with phase change materials with water as the main storage component have been

shown to work well. The opposite effect on capacity in warm climates is not of the same order of

magnitude. In this case the battery should be placed in a way to avoid high temperatures. Already 10C

temperature increases above 200 C will double the corrosion velocity of the electrodes [48].

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6.5 System losses:

Before the system sizing can begin, an estimate is needed for the system losses. When the amount of

energy that the user needs is known, the size of the module can be calculated. Taking into account all

these factors, the battery size can be chosen. The first step is to define the different factors that contribute

to the systems’ energy-loss. All the available energy starts at the module, so we start with the loss-factors

there. PV-module output losses:

Orientation is not optimum: Mostly the module is mounted in a fixed position. For every

location on earth there is one direction and tilt angle that results in the highest annual electricity

generated, or for the highest amount generated during the darkest month, whichever of the two is

required. However, this is not critical. When the direction is within about 20 degrees of the

optimum direction and the tilt angle within 10 degrees of the optimum angle, the electricity

generated is less than 5% of the optimum [48].

Shading of the module: During part of the day the module is often shaded by a tree or a building.

Compared to a module in an open site, this means energy-loss. Furthermore, trees grow. So after a

couple of years a tree could start shading a part of the module.

Dust on the module: Modules need to be as clean as possible. Dust builds up on the surface of

the module especially in the dry season. Therefore, never install a module with an inclination

angle of less than about 15 degrees, to allow the rain to clean the panel. This dust causes energy

losses which can be as high as 5-10% [48] even in areas with frequent periods of rain.

Temperature effect on the module: As described in section 2.4.1, the temperature effect on the

module cannot be neglected. The higher the temperature, the lower the power output of the

module. Modules are tested at a standard temperature of 25C. When lit by sunlight in tropical

areas, the temperature can easily reach 70C. The power at the maximum PowerPoint of crystalline

silicon cells decreases by about 0.4 to 0.5 % per degree Celsius of temperature increase. Taking a

typical figure for the temperature of 60C, results in a reduction of power output by about 16%.

Amorphous silicon modules have a lower temperature coefficient of about 0.2 to 0.25 % per

degree Celsius of temperature increase. For the same temperature this results in only half the

output reduction: 8% at 60C.

Nameplate mismatch: Some manufacturers state an output power on the nameplate, which can

be 10% higher than the actual output power. This has to be taken into account.

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Other losses:

o Cable losses: When electrical energy is being transported via cables, energy loss is

unavoidable. By selecting a sufficiently large wire size, the losses can be reduced to less

than 5%.

o Semiconductor energy loss: Both the MOSFETs (metal-oxide semiconductor field-

effect transistor) as the blocking diodes convert a certain amount of energy into heat.

These components are always included within a charge regulator. On a daily base they

can use about 10Wh. (Module MOSFET during the day, load MOSFET during the night).

o Charge regulator energy consumption: The charge regulator continuously draws a

small current of about 5 to 25 mA. With a quiescent current of 5mA (1.44Wh a day) in a

150Wh system losses will be 1% [48].

o Chemical/electrical energy conversion losses inside the battery: Conversion inside the

battery takes energy. This energy loss also depends on the age of the battery. The

electrical efficiency of a new battery can be 90%. During its lifetime it could reduce to

75%. Due to corrosion and increase in internal resistance in the battery, the capacity will

be reduced to nearly zero, while the electrical efficiency will stay at 75% (for example).

6.6 Sizing of the PV-module

The optimum size of a solar home system is directly related to its costs, household electricity

requirements and their willingness to pay. Generally, people want more electricity, but there is always a

tradeoff between what people want and what they are actually willing to pay. Unrealistic expectations

should be avoided. A 10 Watt-peak module, which is expected to run a refrigerator through a 150 VA

inverter, is certainly going to disappoint the owner. It is the responsibility of design engineers to make

realistic calculations of the number of hours that the lights and other appliances can be operated with a

certain module size. What module Wattage is required for a solar home system? This question can be

answered after taking the following three steps:

a) Determine the average daily electricity demand of the household;

b) Calculate the system losses (see previous paragraph);

c) Calculate the module Wattage.

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Household surveys can provide information about the current demand for energy services of the

households that intend to switch to solar home systems.

6.7 Home solar System Price Offered by Various Company in Bangladesh:

Price offered by various solar modules selling company are summarized below:

Table-6.3: Price of Home System Packages [49].

Load Material Description Quantity Backup Price(tk)

20W

Solar panel- 20 W

Battery- 13 Ah

Charge Controller

Energy Saver- 5 W

Cable & Accessories

1 pcs

1 pcs

1 pcs

2 pcs

As Required

4 hrs 12,500

40W

Solar panel- 40 W

Battery- 30 Ah

Charge Controller

Energy Saver- 7 W

Cable & Accessories

1 pcs

1 pcs

1 pcs

3 pcs

As Required

4 hrs 21,500

50W

Solar panel- 50 W

Battery- 55 Ah

Charge Controller

Energy Saver- 7 W

Cable & Accessories

1 pcs

1 pcs

1 pcs

4 pcs

As Required

4 hrs 24,500

85W

Solar panel- 85 W

Battery- 100 Ah

Charge Controller

Energy Saver- 7 W

Cable & Accessories

1 pcs

1 pcs

1 pcs

7 pcs

As Required

4 hrs 40,500

Solar panel- 100 W

Battery- 130 Ah

1 pcs

1 pcs

104

100W

Charge Controller

Energy Saver- 7 W

Cable & Accessories

1 pcs

8 pcs

As Required

4 hrs 47,500

Table-6.4: Price of Industrial and Commercial Packages [49].

Load Material Description Quantity Backup Price(tk)

100 Wp

Solar Panel- 100 WBattery- 80 AhCharge ControllerInverterCable & Accessories

1 pcs1 pcs1 pcs1pcsAs Required

4 hrs 42,750

200 Wp



4 hrs 82,500

300 Wp



4 hrs 1,25,250

400 Wp



4 hrs 1,67,000

500 Wp



4 hrs 2,08,750

600 Wp



4 hrs 2,50,500

Solar Panel- 700 WBattery- 120 Ah

1 pcs3 pcs

105

700 WpCharge ControllerInverterCable & Accessories

1 pcs1pcsAs Required

4 hrs 2,92,250

800 Wp



4 hrs 3,35,000

900 Wp



4 hrs 3,80,750

1000 Wp



4 hrs 3,96,000

1500 Wp



4 hrs 5,67,500

2000 Wp



4 hrs 7,55,500

2500 Wp



4 hrs 9,46,000

3000 Wp



4 hrs 11,34,700

4000 Wp



4 hrs 15,10,000

Solar Panel- 5000 WBattery- 130 Ah

1 pcs20 pcs

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5000 WpCharge ControllerInverterCable & Accessories

1 pcs1pcsAs Required

4 hrs 18,90,000

Table-6.5: Warranty for Different Equipments [49].

1. Solar Panel 25 Years

2. Battery 1-3 Years

3. Charge Controller 1-3 Years

4. Inverter 1-3 Years

6 .8 Applications of Solar PV:

Solar PV systems have already made significant headway in Bangladesh. Recent pioneering attempts in

this field have generated enthusiasm, but they have also exposed some barriers. Table 6.6 indicates the

existing and potential applications of solar PV in rural Bangladesh [26].

Table-6.6: Existing and Potential Applications of Solar PV in Rural Bangladesh [26].

Type of application Description of applicationRural electrification Power supply to remote villages.

Battery-charging stations.Water pumping and treatment system

Pumping for drinking water.Pumping for irrigation.Water purification.

Health-care system Lighting in rural clinics.Vaccine refrigeration.Blood storage refrigeration

Communication Remote TV and radio receivers.Remote weather measuring.Mobile radios.

Agriculture Livestock watering.Irrigation pumping.

Transportation Road sign lighting.Railway crossing and signals.Runway lighting.Navigation buoys.

Security system Security lighting.Remote alarm system.

Income generation Battery-charging stations.107

Radio, TV, and video pay stations.Village industry power.Refrigeration services.Electrification of rural markets

6.9 Implementation of a Solar integrated DC home System:

A solar integrated DC home system was implemented in the lab using the 40Wp panel of CUET EEE lab,

in order to observe

The practical operation of a DC solar home system.

Measuring the max Useable output under current solar insolation (October, 2012).

Developing a solar home system for rural people in low cost, having all basic needs.

6.9.1 System components

1. Solar panel

108

Fig. 6.3: Solar panel used in experiment

Specification of the module

Solarex: made by Australia

STC@1000w-m2-AM 1.5-CELL T 250C

Model type: MS X40

Serial No: 231-776

Maximum System Operating Voltage: 600V

Minimum Bypass Diode IF: 5A

Series Fuse: 3A

AT 800 w-m2-AM 1.5 CELL

PMAX 40.6W

VOC 21.1V

ISC 2.53A

VPmax 17.2V

IPmax 2.37A

T 490C

PMAX 29.6W

IPmax 1.9A

2. Solar Charge controller

Specification:

Model: E 1212VA

Max : 10A /12 V

Made in Bangladesh

109

Fig. 6.4: Solar charge controller used in experiment

3. Battery and Switching Circuit:

Fig. 6.5: Battery and the circuit built for the DC SHS system

4. Loads:

I. LED light 3 Watt

II. CFL Bulb 10 Watt

110

III. DC Fan 10 watt

IV. DC socket (for other DC loads)

Full system model:

111

Fig. 6.6: Front view of the DC SHS

6.9.2 Operating principal:

In our model there are two inputs.

Direct from panel

From battery

During daylight the system can run using solar energy from panel. The battery will also be charged then.

At night time or in days of autonomy when the panel output is not sufficient enough the whole system can

be run using the battery. The output of the battery is 7.5 Ah and can run the whole system for 4 hours.

6.9.3 Cost breakdown:

Table 6.7: Cost of equipments used in the model

Component name Price (Taka)

Panel 40Wp×100 =4,000

Charge Controller 500

LED Bulb 140

CFL Bulb 265

DC Fan 650112

Holder 50 (25×2)

DC socket 20

Switch and wire 50

Battery 980

Total 6,655

*Solar panel and charge controller were used from CUET Electronics Lab

6.10 Conclusion:

Solar home system has a growing popularity both in developed and developing world.Although Grid

connected PV home system is yet to start in Bangladesh, people here are quenching the benefit from stand

alone home solar system. NGOs like Grameen sakti , BRAC and the Govt organizations are empowering

Bangladesh with Solar PV system. The DC solar home system we designed are very much suitable for

rural of grid electrification serving basic needs of a family within a minimum cost of 6655 taka .The

whole system can run up to 4 hours on battery backup while during day the it can run directly from panel,

making it a suitable product for poor rural people.

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