HYBRID SOLAR
AND WIND POWER: AN ESSENTIAL FOR INFORMATION
COMMUNICATION TECHNOLOGY
INFRASTRUCTURE
AND PEOPLE IN RURALCOMMUNITIES
I.A. Adejumobi1, S.G. Oyagbinrin2, F. G. Akinboro3 & M.B. Olajide4
1,2Electrical and
Electronics Engineering Department, University of Agriculture, Abeokuta, Nigera
3Department of
Physics, University of Agriculture, Abeokuta, Nigeria
4Electrical and
Electronics Engineering Department, Olabisi Onabanjo University, Ago-Iwoye,
Ogun State, Nigeria
ABSTRACT
One of the
primary needs for socio-economic
development in any nation in the world
is the provision of reliable
electricity supply
systems. This work
is a development of an
indigenous technology hybrid
Solar -Wind Power
system that
harnesses the renewable energies in Sun and
Wind to generate electricity.
Here, electric DC energies
produced from
photovoltaic and wind turbine systems
are transported to a DC disconnect energy Mix controller.
The controller
is bidirectional connected to a DC-AC
float charging-inverter system that provides charging current
to a heavy
duty storage bank of Battery and at the same time produces inverted AC power to AC loads. The 2002-
2009, 8years
wind velocity data for
Abeokuta and its environs
were collected. The two parameters
Wielbull
distribution
was used to simulate power in W/m2 densities
for the 8-years period. The step by step design of 1000W
solar power
supply system’s was done as a sample case. Load estimates of a typical rural
community and for rural
ICT
infrastructures were estimated. Simulation of wind power capacity in W/m2 in Abeokuta, Ogun State Nigerian
was done based
on the obtained wind
data. The results showed
that the average exploitable wind
power density
between 4W/m2 and 14.97W/m2is
realizable and that
development of hybrid wind-solar
system for off-
grid
communities
will go a long way to improve socio-economy lives of people.
Keywords: Socio –Economic
development, Nigeria, Hybrid system, Solar and Wind Power, Rural Communities
ICT
infrastructure,
Simulation
1. INTRODUCTION
One of the
primary needs for socio-economic
development in any nation in the world
is the provision of reliable
electricity
supply systems. In Nigeria, the low level of electricity generation in Nigeria
from conventional fossil fuel,
has been the
major constraint to rapid socio-economic
development especially in rural communities. Moreso, about
sixty-five
percent(65%) of 140million Nigeria populace
are rural dwellers with majority of them living far-off grid
areas [1].
These rural dwellers are mostly
farmers whose socio-economic
lives can only
be improved when
provisions are made to
preserve their wasting agricultural products and provide energy for
their household
equipment such
as refrigerator, fan, lighting etc. There is
also such a need to provide electricity for e-information
infrastructures
in our rural communities to service school, rural hospital, rural banking and
rural e-library. Hence,
there is the need
to develop an
indigenous technology to
harness the renewable
energies in Sun and
Wind to
generate
electricity.
1.1 Importance of Renewable energy
The global
search and the rise in the cost of conventional fossil fuel is making
supply-demand of electricity product
almost
impossible especially in some remote areas. Generators
which are often used
as an alternative to
conventional
power supply systems are known to be run only during certain hours of the day,
and the cost of fueling
them is
increasingly becoming difficult if
they are to be used
for commercial purposes. There
is a growing
awareness that
renewable energy such as photovoltaic system and Wind power have an important role to play in
order to
save the
situation. Figure 1 is the schematic layout of Solar-Wind Hybrid system
that can supply either dc
or ac energy
or both.
2. SOLAR ENERGY
Solar energy
is energy from the Sun. It is renewable, inexhaustible and environmental
pollution free. Nigeria, like
most other
countries is blessed
with large amount of sunshine all the year with
an average sun power
of
490W/m2/day [2]. Solar charged battery
systems provide power supply for complete 24hours a day irrespective of
bad weather.
Moreso, power failures or power fluctuations due to service part of repair as
the case may be is non-
existent.
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IJRRAS 9 (1) ● October 2011
2.1 Solar Systems
Adejumobi & al. ● Hybrid Solar and Wind Power
There are two
types of solar systems; those that convert solar energy
to D.C power,
and those that convert solar
energy to
heat.
2.2 Solar-generated Electricity – Photovoltaic
The
Solar-generated electricity is called Photovoltaic (or PV). Photovoltaics are
solar cells that convert sunlight to
D.C
electricity. These solar cells in PV module are made from semiconductor
materials. When light energy strikes
the cell,
electrons are emitted. The electrical conductor attached to the positive and
negative scales of the material
allow the
electrons to be captured in the form of a D.C current. The generated
electricity can be used to power a load
or can be stored in a battery
Photovoltaic
system is classified into two major types: the off-grid (stand alone) systems
and inter-tied system. The
off-grid (stand
alone) system are mostly
used where there is
no utility grid
service. It is very
economical in
providing
electricity at remote locations especially rural banking, hospital and ICT in
rural environments.
PV systems generally
can be much
cheaper than installing
power lines and
step-down transformers especially
to
remote areas.
Solar modules produce electricity
devoid of pollution,
without odour, combustion, noise and
vibration. Hence,
unwanted nuisance
is completely eliminated.
Also, unlike the other power
supply systems which
require
professional
training for installation expertise, there are no moving parts or special
repairs that require such expertise
[3].
2.3 Basic Components of Solar Power
The major components
include P.V modules, battery and
inverter. The most efficient
way to
determine the
capacities of
these components is to
estimate the load to be supplied.
The size of the battery bank
required will
depend on the
storage required, the maximum discharge rate, and the minimum temperature at
which the batteries
will be used
[4]. When designing a solar power system, all of these factors are to be taken
into consideration when
battery size
is to be chosen.
Lead-acid
batteries are the most common in P.V systems because their initial cost is
lower and also they are readily
available
nearly everywhere in the world.
Deep cycle
batteries are designed to be repeatedly discharged as much as 80 percent of
their capacity and so they are
a good choice
for power systems. Figure 2 is a
schematic diagram of a typical Photovoltaic System.
The
photovoltaic cell is also referred to as photocell or solar cell. The common
photocell is made of silicon, which is
one of the
most abundant elements on earth, being a primary constituent of sand. A Solar Module is made up of
several solar
cells designed in weather proof unit. The solar cell is a diode that allows
incident light to be absorbed
and
consequently converted to electricity. The assembling of several modules will
give rise to arrays of solar panels
whose forms
are electrically and physically connected together.
To determine the size of PV modules, the required energy
consumption must be
estimated. Therefore, the PV
module size in
Wp is calculated as[5]:
Daily energy Consumption
(1)
Isolation x efficiency
Where
Isolation is in KWh/m2/day and the
energy consumption is in watts or kilowatts.
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IJRRAS 9 (1) ● October 2011
2.5 Batteries and Batteries Sizes of the Solar
System
Adejumobi & al. ● Hybrid Solar and Wind Power
As mentioned
above, the batteries in use for
solar systems are the storage batteries, otherwise deep cycle motive
type. Various
storage are available for use in photovoltaic power system, The batteries are
meant to provide backups
and when the
radiance are low especially in the night hours and cloudy weather. The battery
to be used:
(a) must be able to
withstand several charge and discharge
cycle
(b) must be low
self-discharge rate
(c) must be able to operate
with the specified limits.
The battery
capacities are dependent on several factors which includes age and temperature.
Batteries are
rated in Ampere-hour (Ah) and the sizing depends on the required energy
consumption. If the average
value of the
battery is known, and the average energy consumption per hour is determined.
The battery capacity is
determined by
the equations 2a and 2b[3]
BC = 2*f*W/Vbatt
(2a)
Where BC –
Battery Capacity
f – Factor for
reserve
W – Daily
energy
Vbatt – System
DC voltage
The Ah rating
of the battery is calculated as[3]:
Daily energy Consumption (KW)
Battery rating in (Amp-hr) at a
specified voltage
2.6 Charging Electronics (Controllers)
(2b)
The need for
Charging Controllers is
very important so that overcharging of
the batteries can be prevented
and
controlled..
The controllers to be used required the following features[4]:
· Prevent
feedback from the batteries to PV modules
· It should have
also a connector for DC loads
· It should have
a work mode indicator.
2.7 Solar Inverters
The Solar
inverters are electrical device meant to
perform the operation of converting D.C from array or battery to
single or
three phase A.C signals. For P.V Solar Systems, the inverters are incorporated
with some inbuilt protective
devices. These
include[3]:
· Automatic
switch off if the array output is too high or too low.
· Automatic
re-start
· Protecting
scheme to take care of short circuit and overloading.
Generally the
inverter to be used that would produce the quality output must have the following
features[3,4,5]:
· Overload protections
· Miniature
Circuit Breaker Trip Indicator(MCB)
· Low - battery
protection
· Constant and
trickle charging system
· Load status
indicator
3. WIND POWER
Wind Power is
energy extracted from the wind, passing through a machine known as the
windmill. Electrical energy
can be
generated from the wind energy. This is done by using the energy from wind to
run a windmill, which in turn
drives a
generator to produce electricity [6]. The windmill in this case is usually
called a wind turbine. This turbine
transforms the wind
energy to mechanical energy, which
in a generator is
converted to electrical power. An
integration of
wind generator, wind turbine, aero
generators is known
as a wind energy
conversion system
(WECS)[7]
3.1 Component of a wind energy project
Modern wind
energy systems consist of the following components[8]:
· A tower on
which the wind turbine is mounted;
· A rotor that
is turned by the wind;
· The nacelle
which houses the equipment, including the generator
that converts the mechanical energy in the
spinning rotor
into electricity.
133
3.2 Wind Turbine
A wind turbine
is a machine for converting the kinetic energy in wind into mechanical energy.
Wind turbines can be
separated into
two basic types based
on the axis about which
the turbine rotates. Turbines that rotate around a
horizontal
axis are more common. Vertical-axis turbines are less frequently used [8,9].
Wind turbines
can also be classified by the location in which they are used as Onshore,
Offshore, and aerial wind
turbines [9]
4.
LOAD ESTIMATE OF A TYPICAL COMMUNITY INCLUDING
INFORMATION
COMMUNICATION
TECHNOLOGY (ICT) SERVICES
In Nigeria,
official definition of rural areas is one with a population of less than
20,000 [14]. In this study, a rural
settlement
with a population of ten families has been considered. The electrical energy
demand for the domestic use
is estimated
as follows:
4.1 Lighting Circuit Assessment
Assume that
each household will use 6, 40 W bulbs, therefore power demand for lighting is =
6 * 40 * 10 = 2.4kW
4.1.1 Power Circuit Assessment
Assume
also that each household
has 1 television set and
1 radio set at power
ratings of 120W
and 20W
respectively.
Therefore,
Power for the
Television sets = 1 * 120 * 10 = 1.2kW
Power for
radio set
= 1* 20 * 10 =0.2kW
4.1.2 Power demand for water pumping
Assume that
the entire village will use 1.5hp pumping machine
Power demand =
1.5 * 0.746 = 1.119kW
Total power
demand = (2.4 + 1.2 + 0.2 + 1.119) kW
= 4.919kW
4.2 Information Communication Technology (ICT)
and the Rural Development
In the recent times, ICT
has been acknowledged
as a means of fighting
poverty and illiteracy
in developing
economics like
Nigeria, if we are to meet Millennium development (MDG) targets. The ICT is one
major key tool to
facilitate
e-service programmes, especially to those institutions such
as banks, hospitals and
schools in rural and
unreached
communities. When this is achieved, the socio-economic lives of rural citizens
will be improved.
To provide ICT
for Rural livelihoods, there is always the need to ascertain an enabling
environment. The enabling
environment has to
do with the national policies, laws,
physical infrastructure (roads, electricity e.t.c.) and others
like access to
education, access to banks, e.t.c., that need to be in place for people to use
ICT infrastructure. It should
be noted that without the availability of
continual supply of electric energy, ICT
provision to rural
communities
becomes almost
impossible.
4.2.1 Rural Hospitals and Banking
Among the
basic needs to actualize vision 2020 and MDGs are the provision of hospital and
Banking facilities to
rural
environments.
As said earlier,
one of the
major needs to
actualize functional and reliable rural banking and
hospital is the
availability
of a continuous and reliable power supply system. Hence, the use of
uninterrupted power source, solar
energy would
be advantageous to facilitate good rural banking, hospitals and ICT.
4.2.2 Energy Estimate For ICT facilities, Bank And
Hospital In Rural Areas
In order to
provide continuous electricity energy to the above mentioned facilities, the
need to embrace Solar Power
supply is
more emphasized here. Since
some of these rural communities suffer
conventional electricity supply
systems, the
supply of these communities with alternative solar energy will be of great
economic and technological
values.
Another advantage of using solar energy is that both D.C and A.C loads can be
supplied. The output from
the solar
panel arrays is D.C while from the inverting battery banks, A.C voltage output
is obtained.
Tables 1,2 and 3 show typical estimated energy to power ICT, Banks and
hospitals in rural communities
5. RESULTS AND DISCUSSION
Adejumobi & al. ● Hybrid Solar and Wind Power
5.1 Choice of components for Solar Energy Power
Supply For 1000 Watt Load:
The choice of
1000W is a sample case and this can be extended to any required capacity.
To achieve a
solar power capacity of 1000watts the
capacities of Solar panel, Charging Controller, bank of battery
and
Inverter are determined. The values
cannot be picked abstractly and hence, their ratings and specification have
to be
determined through calculations in other for the system to perform to required
specifications. For this design
12 hours was
assumed for the duration of the operation and the calculations is done as
indicated below:
5.1.1 Solar Panel:
Total load =
1000W
Period of
operation or duration = 12 Hours
Then, Total
Watt-Hour = 1000×12= 12000w-hr
The period of
the solar panel exposed to the sun = 8 Hours (Averagely between 9am and 3pm)
Therefore
solar panel wattage = 1200 𝑊ℎ = 1,500𝑊.
8𝑊ℎ
Hence solar
panel of 1,500W will be needed for this design.
If solar panel
of 150W is to be use the number of
panels to arrange in parallel to achieve 1,5000 Watt will be:
No of panel =1500 𝑊 = 10
150 𝑊
This shows 10
of 150 Watt solar panel will be required for this design
5.1.2 Charging Controllers:
For this
design of 1000W solar power supply P=IV
Where
I is the expected charging current and
V is the
voltage of the battery and = 12 V
P is the power
supply rating= 1000W
Hence I =𝑃=1000 = 83𝐴𝑚𝑝𝑠.
𝑣
12
Since the
value 83.3 A Charging controllers is not readily available in the market then
1000A charging controller
will be
used.
5.1.3 Battery capacity:
Given that
the total load P= 1000W and
Operational
period = 12 Hours
Watt/hour
capacity = 12,000 W/h
To make the
chosen battery to last long it is assumed that only a quarter (¼) of the
battery capacity will be made
used of so
that it will not be over discharged
therefore hence the required batter capacity will be
12, 000 × 4 =
48,000 W/h
Now the choice
of battery hour depends on A-H rating of the storage battery. For example,
for 200AH, 12V battery
the number of batteries that will be needed is 48000 = 240 batteries.
Also for a 1500AH, 12V batteries the number
200
of batteries that will be needed is 48000 = 32 batteries. Hence, for this design
and to avoid too much weight and
1500
occupying
unnecessary space, 15000AH 12V battery should be used, Therefore the total
number of storage battery
required for
1000W solar power supply system = 32
5.1.4 Inverter
Since the
total load is 1000W it is advisable to size the required inverter to be 1500W as designed for solar
panel
ratings. Hence
1500W pure sign wave inverter is recommended in other to prolong the lifespan
of the inverter.
.
5.2 Wind Power Simulation:
The study area
of Abeokuta have been chosen as sample
case. Abeokuta is south-western Nigeria
on Latitude 70
09’N and
Longitude 3021’E. The eight years (2002-2009) wind speed data
were collected from the monitoring unit
of the Department of Agricultural Meteorology and
Water Resources (AGROMET),
University of Agriculture,
Abeokuta. From
the average monthly wind speed data collected, the annual average was
determined
With an
assumed Aero generator
Hub Height of 50m[7,16],
and by applying
expression 3 to
7, the annual mean
speed and the average wind powers for various years
were shown in Table 4. From this result,
an average power
output of
13.6.kW at a blade diameter of 300m2can be obtained from the study site using equation
7.
There is the
need for the provision of an alternative sustainable electric power supply
system to provide electricity to
rural and the
unreached communities. The importance of Information Communication Technology
for e-service to
rural
communities are inevitable in order to achieve the MDGs objective. Also there
is the need for rural banking
and hospitals
if the social and economic lives of rural citizens in Nigeria are to be
improved.
The provision
of hybrid solar -wind energy system to power ICT infrastructures, banking and
hospitals in rural and
the unreached
communities that are not connected to National Grid Power supply system is very
important so as to
maintain a
continuous electricity supply.
When
considering the cost and overall efficiency, it is advisable for all the
stakeholders who have concern for the
rural
community development to embrace solar and wind power.
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