solar system pakistan
TRANSCRIPT
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.