DESSEMINATION OF USE OF SOLAR ENERGY IN PAKISTAN

1. INTRODUCTION:

Pakistan is an energy deficient country, where a large fraction of the population still

does not have access to modern day energy services such as electricity. This is due to

very limited fossil fuel resources and poor economy, which restrains the import of fossil

fuels on a large scale. Due to rising demand and a failing power infrastructure severe

electricity shortages have occurred in Pakistan. This has led to widespread rolling

blackouts that have paralyzed industry and led to protests and rioting.

To overcome energy shortage, Pakistan needs to develop its indigenous energy

resources like hydropower, solar and wind. Pakistan lies in an area of one of the highest

solar insolation in the world. This vast potential can be exploited to produce electricity,

which could be provided to off-grid communities in the northern hilly areas and the

southern and western deserts.

The Climate and suitable weather conditions in Pakistan are ideal for Solar Energy use.

2. An Over View

As solar power does not make sense for all locations in the world. The initial cost of

installing solar panels or other sources of solar energy is high, and that is not easy for

most people to get around. No matter how much some people would like to get involved

in the movement to independent energy, it is cost prohibitive. To achieve the highest

level of efficiency, which is the entire point of going solar in the first place, you need the

proper amount of secure space to support the panels. Not only how much space is

available, but also the location is also relevant to whether or not you can maintain solar

energy. Some locations simply do not receive enough sunlight to produce substantial

energy.

Applications other than electricity production such as solar water heaters and solar

cookers also have vast applications. Solar energy can be harnessed to provide irrigation

by using solar water pumping station. All this will help in both reducing the import of

fossil fuels and dependency of people on fuel wood.

2.1 Development of Solar Technology

It has been known for many years that some substances give off electrons when light

strikes them and these electrons may be used to form a current. The development of

photovoltaic (PV) technology began in 1955 and came of age in the 1980's. PV

technology was initially regarded as "space age" because the use was limited to

satellites, but in 1980 the cost was reduced by two-thirds making PV modules more

affordable to the general public. PV technology is built on the solar cell. This small,

paper-thin disc is made of silicon, an inert crystalline material refined from sand.

Exposing the solar cell to sunlight causes electrons to jump from the positive to the

negative side of the cell. Thus generating direct current. Solar cells are assembled into

panels called modules. A solar panel will produce about 50 watts of power.

Photovoltaic (PV) panels are the simplest possible way to generate electricity beyond

the reach of power lines. They have no moving parts and last for decades with virtually

no maintenance. Solar power is no longer an expensive, experimental energy source.

Photovoltaic are now standard in many commercial, industrial, military, and consumer

applications, wherever modest amounts of power are needed beyond the power lines.

Solar-powered Water Systems are practical in flat terrain where the sun shines.

2.2 Factors of Significant Importance:

2.2.1 Experienced installers:

Ideally, PV water-pumping systems should be installed by professionals from the region,

although this is not always easy for remote areas. In addition, it is important that the

installer be easily located in case service should be required in the future (especially for

the pump). The provider and installer should be able to demonstrate their experience,

technical expertise, and integrity.

2.2.2 User acceptance:

Users should understand the abilities of solar energy systems, including their limitations,

advantages, expected maintenance requirements, and principles of operation.

Designers should involve users with general project design. This will allow them to

grasp the technology better as well as feel a sense of buy-in to the project and its

realistic outcome.

2.2.3 Security:

The nature and portability of solar water-pumping systems make them ideal for remote

and isolated applications, but they also become vulnerable to theft and vandalism. They

are best protected from theft if they are placed in areas that are not likely to be transited

and seen by the general public.

2.2.4 Environmental benefits:

Solar energy technology helps maintain clean air and water quality. An added plus is

that it pumps with little noise, unlike noisy diesel- or gasoline-powered pumps.

2.2.5 Batteries:

Batteries are a key part of PV systems in most applications, but are rarely used in

tand-alone solar pumping systems. Batteries add cost and complexity to the system. It

is far better to design a system where energy is stored in the form of additional pumped

water available at the distribution tank instead of in electrochemical form with batteries.

The only time batteries are commonly employed is for a household water pump with an

existing battery bank supplying energy to other household loads as well.

3. SOLAR WATER PUMPING SYSTEM

Pumping water is a sensible and effective use of solar electric power. During the hot

months, when water requirements are highest, a solar pump will provide a reliable water

source for the farm. Wind power, by comparison, can be inconsistent, and may not be

available during the hottest months in many inland areas. Wind may be too unreliable

for water pumping when a relatively constant supply is required, as for stock watering. A

solar water pumping system is essentially an electrically driven pumping system.

Electricity, in this instance, is produced by the sunlight energizing photovoltaic (solar)

modules. The typical solar cell is a thin wafer of silicon that transforms light energy into

electrical energy. The cells are encapsulated in flat modules to protect them from the

weather. Any number of modules can be connected together to form an array. The array

is sized to meet pumping systems’ power requirements.

A solar pumping system is available for almost all applications where an electric pump

can be used. Because solar energy varies from one location to another, and over the

course of a day, system design is important. Adequate water storage ensures that water

is available whenever needed, and balances daily variations in water supply and

demand. Thus a small pump only running when the sun shines, plus water storage, can

provide the average requirement for water supply.

For the best electrical and mechanical performance, all components of the solar

pumping system must be carefully matched. Correct sizing of the pump, motor

and controlling devices, will allow the system to operate at the highest efficiency to

ensure economical water pumping.

3.1 Working of solar water pumping system

A solar-powered water system is made of two basic parts. The solar electric modules

are the power house. The electricity from the panels goes to the motor and pump, which

send the water through the pipe to where you want it. Many solar-powered water

systems pump the water into a large holding tank. This reserves storage supplies during

cloudy weather or at night.

Solar modules are usually installed on secure ground or pole mounting structures. For

more output, modules are installed on a tracker (a mounting structure that follows the

sun like a sunflower).

Solar electricity may be used directly or it may be stored in batteries for later use. The

batteries used for most systems are slightly different than ones used in cars. They are

called deep-cycle batteries and are designed to be rechargeable and to provide a

steady amount of power over a long period of time.

3.2 Applications for solar pumping

Solar pumps can be used almost anywhere electrically operated pumps are used.

However, the most cost effective applications of solar water pumps occur when either:

(a) there is a low power requirement;

(b) the area or application is remote and it is costly and time consuming to operate

and maintain diesel or petrol engines; or

(c) Where there is no reliable electricity supply readily available.

There are numerous applications where solar pumps can be used. The most common

are:

Livestock water supply.

Domestic and home water supply.

Irrigation—drip and spray jet.

Water transfer—e.g. pond to tank.

Pumping to assist control of water salinity.

3.3 Water requirements

This is usually estimated in litres per day of the water needs of both stock,

domestic use, and garden requirements. The following table will assist you in

making an estimate. It would be useful to the solar pump supplier if you could

also provide likely minimum/maximum demands.

Use Litres of water per day*

Beef cattle25–50/head

Dairy cows (in milk)50–70/head

Horses35–55/head

Sheep3.5–7/head

Lambs1.2–2.5/head

Domestic (kitchen,bathroom, toilet, laundry)

140–270/person

Garden sprinkler (10 litres/square meter togive good soaking)

About once per week as required

Note: Domestic consumption can increase by more than 50% when a house is connected to a septic system.

3.4 Design Aspects of solar pumping

When choosing a solar pump the following factors need to be considered:

• The amount of solar energy available in the location proposed.

• The total dynamic head of the system.

• The amount of water required.

• The quality of water to be pumped.

The sizing of the solar pumping system that suits your needs requires expert advice.

Reputable manufacturers and suppliers of solar water pumping systems can accurately

predict performances from various systems.

The amount of solar energy available will give an indication of the number of solar

modules needed to provide the power to pump the required quantity of

water at the calculated head.

The available energy and the amount of water pumped vary during any season. In order

to avoid over sizing ask the supplier of solar water pumping systems to predict

performance, so you can choose the system sized for your needs.

The size of the solar array is ultimately determined by the specific pump manufacturer

as the wattage output must be closely matched to the pump requirements. However, it

is a good idea to do a preliminary calculation to see approximately what the solar array

size might be, in order to estimate costs of the project.

The power needed to move water is = Flow rate x PressureOr = Flow rate x Head x g x fluid gravity

The formula for sizing pump power requirement is:

Watts = (Required flow in GPM) x (TDH in feet) x .188 (U.S. Units) Efficiency of Pump (%)

Watts = (Required flow in LPM) x (TDH in meters) x .163 (Metric Units) Efficiency of Pump (%)

(The numeric value of the constant comes from combining water density x gravity ‘g’ x flow rate unit conversions )

3.5 Size of System

i. Small Systems:

2 GPM (600 GPD)

Up to 100 ft. TDH

Small systems could be generally accomplished with a diaphragm pump. These pumps

are not extremely expensive, and the solar array may be in the area of 100 to 300 watts.

ii. Medium Systems:

4 to 8 GPM (1200 to 2400 GPD)

Up to 100 ft. TDH

The pumps for these medium – sized systems are more expensive than a small system

and will often take a helical rotor positive displacement pump or a centrifugal pump.

The array might be between 200 and 600 watts.

iii. Large Systems:

over 8 GPM (over 2400 GPD)

Up to 200 ft. TDH

Systems over 8 GPM at most lifts and systems over 4 GPM at lifts over 100 feet could

be considered large systems. These would take the more expensive helical or

centrifugal pumps, and could require arrays approaching 2000 watts.

Lifts exceeding 200 to 250 feet become extremely costly, if even practical, with anything

but the smallest of flows. Flows exceeding 16 GPM (5000 GPD) with any appreciable

head are generally not feasible, with today’s solar pumping technology (except for some

of the very new, very expensive systems). Options would be to install multiple wells and

pumps, and/or go to standard AC pumps with inverter/controllers such as the Universal

Pump Controller.

3.6 Power required for water pumping

The amount of power that is required for a solar water pumping system depends on the

quantity of water to be pumped, the rate at which it is to be pumped and the total head

at which the system must operate.

Total head consists of two parts:

(i) The static head (the height through which the water must be lifted), and

(ii) The dynamic head (the pressure increase caused by friction through the pipe work

and expressed as an equivalent height in meter).

The static head can be easily determined by measurement. The dynamic head depends

on a flow rate (which must be based on the maximum pump performance in peak

sunlight intensity), pipe sizes and pipe material. The smaller the pipe and the greater

the flow rate, the higher the pressure required to force water through the pipe.

3.7 TYPES OF SOLAR PUMPING SYSTEMS

Water can be pumped from the shallow and deep aquifers using wind pumps, solar

pumps and diesel and gasoline pumps. A comparison of water pumping technologies is

given in table 1.1.

Table 1.1 Comparison of Water Pumping Technologies

Pump Type Advantage Disadvantage

Wind-Pump Unattended operation.

Easy maintenance.

Long life.

Water storage require for low

wind periods.

High system design.

Solar –Pump Unattended operation.

Low maintenance.

Long life.

High capital cost.

Water storage require for

cloudy periods.

Skill persons require.

Hydraulic-Pump Unattended operation.

Easy maintenance.

Long life.

Require specific site

condition.

Diesel &

Gasoline -Pump

Quick & easy install.

Low capital cost.

Widely used.

Short life.

Noise & fume pollution.

High maintenance cost.

Electric – Pump Quick & easy install.

Low maintenance

Long life

High capital cost.

High running cost.

Although solar water pumps have been developed from some fairly sophisticated

“hi-tech” components, they are relatively simple, uncomplicated packages of equipment.

Solar water pumping systems consist of three basic components:

1) Power source (photovoltaic solar modules)

2) Motor/pump (or motor/compressor) assembly

3) Power controllers for matching the changing electrical output of the array to suit

the Motor /pump.

A typical layout of solar pumping system is shown in figure 1.

Figure 1. Typical layout of solar pumping system

3.8 The Pump

Pump options and the system configuration are described below;

i. Submersible Pumps

This is often with electronic load controllers. The pump will be submerged while the load

controller is above ground. The advantages of this configuration are that it is easy to

install, often with lay-flat flexible pipe work and the motor pump set is submerged away

from potential damage.

ii. Multistage centrifugal pumps

The centrifugal pump will start at low torque and can be matched with the solar array

without electronic controllers. The pumps are not as an efficient as positive

displacement pumps using cheap electronic load controllers. Suitable for smaller heads.

Older type set with AC motors operates at heads of 10-25m.

iii. Positive displacement helical pumps

Helical pumps have the best efficiency and the smallest PV panel for the same specs of

water delivery volume pressure and head. They have low rotational speed. The pump is

made up a metal helical rotor which rotates in a rubber casing. These are suitable for

bigger heads. A Mono solar pump will slow down when it is cloudy, but because it has

no minimum speed (unlike a centrifugal pump) it will keep delivering water.

iv. Submerged pump with surface mounted motor

The main advantage is the easy access to the motor for maintenance. The low

efficiency from power losses in the shaft bearings and the high cost of installation has

been disadvantages.  In general this configuration is largely being replaced by the

submersible motor and pump set.

v. Floating motor pump sets

The versatility of the floating unit set makes it ideal for irrigation pumping for canals and

open wells. The pump set is easily portable and there is a negligible chance of the

pump running dry. Most of these types use a single stage submersed centrifugal pump.

The most common type has a brushless dc motor. Often the solar array support

incorporates a handle or 'wheel barrow' type trolley to enable transportation.

vi. Surface suction pump sets

This type of pump set is also suitable for low head applications. It is not recommended

except where an operator will always be in attendance for maintenance and security of

exposed systems. Although the use of primary chambers and non-return valves can

prevent loss of prime, in practice self-start and priming problems are experienced.  It is

impossible to have suction heads of more than 8 meters. Less common types of solar

powered pumps include solar PV powered reciprocating piston (nodding donkey) pumps

and solar thermal pumps or thermo siphons pumps exits but are not commercially used.

3.9 Performance

Solar pumps are available to pump from anywhere in the range of up to 200m head and

with outputs of up to 250m³/day. Solar pumping technology continues to improve. In the

early 1980s the typical solar energy to hydraulic (pumped water) energy efficiency was

around 2% with the photovoltaic array being 6-8% efficient and the motor pumpset

typically 25% efficient. Today, an efficient solar pump might have an average daily solar

energy to hydraulic efficiency of more than 9% but lower efficiencies of 2 -3% are still

common. It is important to get the most efficient pump available as the difference in cost

between the poor pump and a very efficient pump is much less that the additional cost

required for a larger PV panel. Accurate sizing of the array is important in keeping costs

down.

A good sub-system (that is the motor, pump and any power conditioning) should have

an electrical to hydraulic efficiency of around 70% using positive displacement pumps.

With diaphragm pumps the efficiency will be around 45% and centrifugal pumps might

have an efficiency of 20%. 

3.10 Working Modes of Solar Pumps

i. Directly connecting the solar panel to the pump.

If the pump is directly power to the solar panel then water can only be pumped

when the sun is shining.

ii. Charging the battery with solar-panel and then using the battery to run the pump.

Charging the battery first and then using that to run.

3.11 Advantages of a Solar Pump

A revolution is taking place in how water is being pumped in remote locations beyond

the reach of electric power lines. Solar-electric, or Photovoltaic, power has proven to be

an ideal way to lift water for drinking, sanitation, stock tanks, and irrigation. Photovoltaic

pumps have been on the market since 1980 and are in use all over the world.

Solar-powered water pumps can be placed in or next to the pond or other source of

water and the water can be pumped where it is needed.

Solar water pumping is clean and efficient. Solar electric water pumping cuts down on

waste because it’s based on natural cycles. Your panels give the most pumping power

on the sunniest days---when you need the most water. Solar power is clean. You never

have to worry about polluting the groundwater or air with a gas-powered pump.

Solar-powered water systems take very little maintenance because they only have a

few moving parts. They have long life---usually 20 to 40 years. And solar water systems

never run out of fuel as long as the sun is shining.

3.12 Existing Experience:

PV systems have proven to be an excellent option in meeting water-pumping needs

when electrical grid service does not exist. Between 1994 and 2005, over 1,700 PV

water-pumping systems were installed throughout Mexico.

Now in Pakistan, people are coming forward and indulging themselves in this new

technology. In this regard, a farm owner, Mr. sadaqat Ali Mand of village Snopper

District, Gujranwala has installed a solar water pump on his agricultural land to irrigate

10 Acres. This solar pump system is working to the satisfaction of the owner.

The main features are as under:

Solar power tubewell installed

4 set of Polycrystalline Solar panels

Each set have 16 Modules of 1007 X 652mm

Power generation at source

Inverter installed Three Phase from D.C to A.C.

Pump and motor Submersible designed for (3 inch Dia)

Depth of bore

Bore hole

Depth of water table

Rated head of pump

Delivery pipe size

Currently water being used for filling of two fish ponds.

March 2010

KYOCERA , Made in Japan

Total panels = 64(16x4)

7KW DC

7.5 KVA

5.5KW

80 ft

12 inches

35 ft

20 meters

4 inches

Size 440x320x7ft

Farmer intends to use water for crops in near future for cultivation of Rice crop as alternate irrigation source.

Cost (Includes Tubewell + solar pumping system and discharge box)

Discharge (measured on 05/05/2010)

Discharge (working 8 hrs per day)

Rs. 30 Lac

0.32 cfs (9.0lpd)

=68571 US Gallons/day=259200 litres/day=0.21 AF/day

4. Solar Hot Water (Solar Geysers)

Natural and Propane Gas prices have double and tripled over the last year. Electricity

rates are starting to go up. You may not be able to beat the high prices of gasoline, but

you can sure out-wit the gas and electrical companies.

Solar radiation is a free, clean and inexhaustible source of energy. In a split second the

sun radiates more energy than was converted and stored by plants in fossil fuel over

millions of years.

Using great new technology we can now convert solar radiation efficiently into a usable

from of energy that heat water which we can use in our homes, factories and offices.

The key is our new actuated glass tube.

In Pakistan, Thermal plants are using oil, natural gas, and coal account for about 70

percent of this capacity, with hydroelectricity (hydro) making up 28 percent and nuclear

2.5 percent. Pakistan's total power generating capacity has increased rapidly in recent

years. Pakistan often faces short fall of electricity in peak seasons. Rotating load

shedding are, however, still necessary in most areas.

This shortage will be met through alternate energy sources like solar, wind and

biomass. Solar Hot Water (Solar Geysers) is made up of vacuum tube, frame, storage

tank, silicon seal, and relational components as shown in figure – 2.

Figure -2 SOLAR WATER GEYSER

4.1 Prominent Features of Solar Geyser

Availability of free hot water 24 hrs a day.

Designed to heat water to 60oC, even in cold climates.

Save upto 80% of Domestic Gas bills in the winter season.

Environment friendly.

20 year life time expectancy.

Absolutely no maintenance.

Quick pay back period.

The following can be used as a guide to determine the capacities required by a typical

household;

Persons Litres Square Meters

2 People 100 2.0m sq panels

3 People 150 2.6m sq panels

4 People 200 2.9 m sq / 3.6m sq panels

6 People 280 2 x 2.0m sq panels

4.2 Working of Solar Geyser

Solar Geyser relies on warm water rising, a phenomenon known as natural convection,

to circulate water through the evacuated glass tube collector and to the tank. Hot water

storage tank is located above the absorber evacuated glass tubes as shown in fig.3.

As water in the absorber heats, it becomes lighter and naturally rises into the tank

above. Meanwhile, cooler water in the tank flows downwards into the absorber, thus

causing circulation throughout the system.

Figure -3 WORK PRINCIPLE OF SOLAR WATER GEYSER

In sunny days Solar Geyser can bring water to boiling point. The hot water system can

easily be automated with the natural gas boosted or electric geyser so hot water is

guaranteed regardless of sunlight levels.

Solar Geyser System is an alternative to gas or electricity boosted geysers in the some

areas of Pakistan. Averaged over a year, a correctly sized Solar Geyser System can

provide 80% to 100% of a household's hot water needs

Geyser can be used in temperatures as low as -10° C, although performance is reduced

in such extreme conditions but Good heat output is still achieved in mild sub-zero

conditions as long as there is sunlight.

Although the heat output of the solar collector is reduced on overcast days it will still be

able to provide heating. If it is a heavily clouded day or raining, then more gas or electric

boosting may be required to maintain water at the required temperature. This system

will be automated with the existing natural gas boosted geyser or electric geyser, so you

don't have to worry about running out of hot water on a rainy day.

4.3 Maintenance of the Solar Geyser

Under normal circumstances no maintenance of the system is required. Due to the

shape of the tubes regular rainfall and wind should keep the tubes clean. Should a tube

even be broken it should be replaced. This, however, is an inexpensive and easy job.

Any "handy" person can install a new tube.

4.4 Solar Geysers expensive

No. In the long term, a Solar Geyser can save you up to 80% of your household's

electricity or gas expenses and over a 20 year period is considerably cheaper than

buying a straight electric or gas geyser due to the much lower running costs of a Solar

Geyser system.

4.5 Solar Geyser helps the environment

Using solar and other forms of renewable energy reduces reliance on fossil fuels for

energy production, thus directly reducing CO2 emissions. CO2 emissions contribute to

global warming, an environmental issue which is now of great concern. The average

household can reduce CO2 emissions by as much as 20% by installing a Solar Geyser

System.

5. Solar Street Lights

Solar powered lighting is a relatively simple concept. Solar street lighting system can

save energy, environment friendly, and is convenient to install. The basic unit for

producing energy is obviously the solar panel itself, which is the means by which the

energy given out by the sun is converted into electricity. We are all familiar with quite

large solar panels, for domestic or industrial use, but the technology has advanced to

such an extent that there are currently many different sizes and power outlets available

for use.

This wide variety means that one has to be careful to select an appropriate panel for

each specific necessity. In the context of solar powered street lights, the solar panels

employed need to be suitable for extreme weather conditions, capable of producing

energy even on cloudy days and able to withstand vandalism and attempts at. They

also need to be economical enough to use in large numbers. It is not uncommon today

for these factors to be met with such confidence that a 20 year warranty is offered on

the very best solar panels.

The solar panel itself will be connected to a solar controller – a battery charger which is

automatically topped up by the solar panel linked to a timer or photocell which ensures

that the solar powered street lights operate in the hours of darkness. Some specific

systems employ a further function whereby the light dims at specific times.

The batteries themselves need to be completely maintenance free and capable of

providing enough energy for a period of reserve power should there be some sort of

problem with the charger or a prolonged period of bad weather.

Schematic diagram of solar light system is shown in figure 4.

Figure. 4 Schematic Diagram of Solar Light

5.1 Models of Solar Street Lights

1) Sodium Vapor Lights:

The sodium street lights use sodium in excited state to discharge the light. These lights

comprise of the solar panels that absorb the solar energy during daytime, which is

converted into electricity and stored in the batteries. At nighttime the sodium lamps

consume electricity from rechargeable battery. There is no wiring required for these

lamps, there are no electricity bills to be paid, they are very safe and can light the

streets from 4 to 12 hours depending on the size of the solar panels and battery. The

sodium solar street lights can be used for lighting streets, public places, residential

areas, parks, plaza etc.

Sodium Vapor Light

2) Solar LED lights:

LED stands for light emitting diode. LED comprises of the chemical compound that

gives of the light when direct current (DC) from the battery passes through it. Solar

LEDs are available from number of companies in different sizes, shapes and styles. The

life of LED is usually very high extending up to 50,000 hours. The LEDs require very

little current hence the solar panels of smaller sizes are required for the solar lights with

LED lamps.

Solar LED light

3) Solar lights using induction technology:

In this technique the lamps used in the solar lights do not contain the filament or the

electrodes that tend to get damaged faster, thus ensuring very high life of the lamp. The

life of the lamp in solar street lights based on induction technology can be more than

10,0000 hours, which is almost 100 times the life of the incandescent lamps. These

results in lower maintenance and electrical costs and fewer disturbances caused to the

traffic on the road. Since these lights are based in induction technology, they generate

lesser heat, thus permitting the use of aluminum reflectors that increases the intensity of

the light produced by the lamp.

Induction Solar Light

6. Proposal For Introduction Of Solar Technology

WAPDA should launch a pilot project with respect to the following incorporations:

Solar water Geysers may be installed in all WAPDA Rest Houses, colonies and

offices as a primary source of hot water in a manner that existing gas geysers are

not made redundant and may be utilized during night and over cast conditions.

10 – 15 Nos. of Solar pumps for irrigation purpose may be installed in four

provinces of Pakistan including Gilgit Baltistan, AJK & Fata.

Solar street lights in all WAPDA colonies of major cities.

7. Monitoring Of Existing Solar Facilities / Projects

A team consisting of WAPDA personals may be formulated to monitor the existing

facilities/ projects already functioning in the country. They should prepare their

comprehensive recommendations/ proposals, keeping in view the present performance

of the current Solar projects.