Low Speed Vertical Axis Current Turbine for Electrification of Remote
Areas in Malaysia
ATEF SALEM MEFTAH SOUF ALJEN and ADI MAIMUN
Marine Technology Centre, Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
81310 Johor Bahru, Johor
MALAYSIA
Abstract: For Malaysia, rivers and ocean energy can be the best source of environment friendly water/marine
renewable energy. Generation of the electricity by burning of fossil fuels produces undesired greenhouse gases
and on the other hand the reserves of fossil fuels are being depleted and there is no accurate way to determine
how much remains. Fossil fuels are also known to have harmful effects on the environment. This paper
presents the development of an advanced novel small current turbine electric system for low speed flow stream
which is suitable for deployment in remote areas (rural areas and islands) in Malaysia. In this paper, analytical
computation based on a system of two current turbines of 2 kW output capacities at 1 m/s average current speed
is shown. Each turbine will produce daily energy of about 2.5 KWh which can supply electrical power for a
household with autonomy time of 2 days (battery storage) based on the national average. Higher electrical
power supply is possible with increase in number of turbines or increase in current speeds. This gives the
possibility of an optimised novel electrical power system consisting of small current turbines to be developed in
future. The specifications of the system components and its performance parameters can be estimated by using
a developed computer program.
Keywords: Renewable energy, LS-VACT, Electrification, Remote area, Computer program.
1 Introduction In parallel with Malaysia’s rapid economic
development and growing energy demand, more
alternative energy sources are needed to fulfil its
demand for energy [1, 2]. Due to, the rapid growth
of gas emissions which causes to the climate
change will make the country suffer from the
floods and other effects. Moreover, the Malaysian
fossil fuels reserve will be depleted soon [15] and
there is no accurate way to determine how much
remains [14]. In 2009, Malaysia formulated the
National Green Technology Policy [3] to promote
green technology usage for economic growth as
stated in [1]. Malaysia’s rivers and ocean can be the
best resource of green marine renewable energy. As
known the forms of these resources of marine
energy especially the ocean energy can be
categorized into tidal, wave, current, thermal
gradient and salinity gradient [4, 5]. Among them,
the marine currents present a relatively new and
almost unexploited source with a worldwide
diffusion of potentially highly-productive sites. So
in this area, there are two kinds of hydro-turbines;
vertical-axis and horizontal-axis turbines that can
be used as power generation devices as stated in
[6]. Horizontal-axis turbines are complex system
and suitable only for large size plants where high
installation and maintenance costs are balanced by
large energy produced. On the other hand, vertical-
axis turbines are relatively simple and represent a
promising technology to exploit marine currents
due to their small plants with reduced installation
and maintenance costs [7] and they are suitable for
deployment in remote areas[8, 9]. Current speed
and water depth are the important factors which the
marine current turbine more depending on [3].
From the literatures, at least 2 m/s (4 knots) is the
ideal marine current speed to make the turbine
work. In Malaysia’s sea and river areas, the average
current speed is about 1m/s (2.0 knots) as reported
by the Royal Malaysian Navy [3, 10]. The range of
current speeds is between 0.5 to 2.5 m/s. Due to the
low current speed, a big system of turbine is
required to harness the current energy. The problem
lies in that the blade length is limited to the
available water depth [3]. Previously, a Savonius
vertical-axis turbine has been proposed to harness
current energy [11]. But this type of turbine has
two main drawbacks which are low efficiency and
low tip speed ratio TSR (λ) which makes this rotor
Recent Advances in Renewable Energy Sources
ISBN: 978-1-61804-303-0 75
difficult to be integrated with a generator. So, a
Low Speed Vertical Axis Current Turbine (LS-
VACT) based on Savonius rotor (which can extract
the energy from low current speed [6, 12]) with the
novel modifications in having an arm to increase
the torque and self-adjusting blades to reduce the
drag [13], appears to be the suitable technology to
harness marine energy from the low speed current.
Therefore, this turbine will be used in the small
electric system to harness the energy from low
velocity stream. These small marine current electric
systems can make a significant contribution to our
nation’s energy needs. In rural areas and islands,
for consumers wanting to generate their own green
power, installing a small low speed marine current
turbine electric system can be an option to avoid
the high costs of extending utility power lines to
remote locations. Small LS-VACT electric system
is an electric generator that uses the energy of the
flow current to produce clean, emissions-free
power for individual homes in islands, fishing
farms, and small businesses near coastal areas.
With this simple and compact technology,
individuals can generate their own power and cut
their expenses on fuel to produce energy while
helping to protect the environment. Moreover,
these Off-grid (systems not connected to the utility
grid) stand-alone small turbine electric systems can
store power in batteries for on-demand use.
2 Small Electric System Components
2.1 System Overview The LS-VACT current energy converter is mounted
to the floating buoy which is moored to the seabed.
The buoyant is equipped with permanent magnet
synchronous generator (PMSG) and gearbox
(speed-up gear). The small electric system also
contains; batteries, controller and invertor. A
functional principal sketch of LS-VACT electric
system is shown in Figures 1 and 9.
In this stand-alone system as shown in Figure 2, the
LS-VACT converts the current flow energy to the
mechanical power. After that, the generator
converts the mechanical power to electrical power
for battery charge and for feeding the off grid
inverter. Inverter or a power conditioning unit
converts the power from direct current (DC)
to alternating current (AC). Both, generator and
battery as DC power sources must be capable of
supplying enough current for the intended power
demands of the load system.
The current turbine electric system is a
configuration involving multiple turbines. The
arrangement of the floating system is shown in
Figure 3.
Fig 3: Small Current Turbine- Floating System
In this paper, a small compact system consists of
two buoys, with a set of current turbine mounted on
AC
Load
LS-
VACT
Synchronous
Generator
Controller Inverter
Current
Energy
Mechanical
Power
Electric
Power
Battery DC
Load
Fig 2: A Diagram of Standalone Low Speed Vertical
Axis Marine Current Turbine Electric System
Fig 1: A Functional Principal Sketch of LS-VACT Electric
system
Charge
Controller
Battery
Bank
DC LOAD
AC LOAD
Inverter
Small
Low
Speed
Current
Turbine
Electric
System
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ISBN: 978-1-61804-303-0 76
each buoy is considered. Inside each buoy is
asynchronous generator fitted with speed-up
gearing. These buoys are attached to each other
together using frames and moored to the seabed
using either flexible or rigid moorings. This will
allow the study on how each turbine will interact
with the wake from adjacent turbine.
2.2 System Advantages and Electrification
Benefits The proposed current turbine–generator system is
an efficient and environmental friendly small low
speed vertical axis current turbine which can
extract the energy from low velocity stream. In
addition the turbine has novel modifications which
are arms to increase the torque to match it with
suitable generator and self-adjusting buckets
(blades) to reduce the drag to enhance the generator
output and hence the efficiency. Moreover, the
small system has a variable speed generator and
variable voltage charge controller to make the
system operate automatically and sufficiently and
to keep the batteries from overcharging.
Using such systems for electrification of remote
areas will have big benefits due to the impact of
rural electrification; such as quantified benefits in
cost saving and increased productivity [16]:
1. Electricity is used by the industrial and small
business
2. Electricity is used by the Household in Lighting,
cooking etc.
3. Electricity is used by the Agricultural in Water
pumping
Other benefits of the electrification of rural
areas which cannot be directly quantified are
improvements in; social equity, modernization,
dynamism, attitude changes, quality of life,
community services, participation and finally job
creations.
2.3 Marine Current Flow Marine Currents are generally driven by the effects
of the tides and to some extent by oceanic
circulations. The tides are driven by the interaction
of the gravity fields of the moon, the earth and the
sun whereas oceanic circulation is caused partly by
the earth’s rotation and partly by temperature
variations and salinity variations in the seas. Tidal
currents, being based on the motion of the earth,
moon and sun, are predictable far into the future,
unlike the weather dependent renewables such as
wind, wave or solar energy. There are several
characteristics of marine currents that make them
attractive as an energy source. Marine currents,
especially tidal currents, are largely predictable. As
an energy source they also offer a potentially high
degree of utilization, something which could have a
strong impact on the economic viability of any
renewable energy project [17]. Limited rated
velocity of each device gives smaller difference in
power production between spring and neap and
thus also a higher degree of utilization [18]. Hence
the predictable nature of the resource combined
with a limited power of each device could be
beneficial for management of power delivery in the
case of a large scale marine current turbine farm. In
some places the tide is phase shifted along the
coastline, which means that several marine current
turbine farms could be geographically located to
even out the aggregated output over the tidal cycle.
This has for instance been shown to be the case
around the British Isles [18, 19].
Malaysia sea areas have an average current
speed of only 1m/s (2.0 knots) [3, 10]. This is about
half of the speeds for turbines that have been
designed and developed in other countries. Current
speed and water depth are the important factors to
be considered for application of marine current
turbines. The study on ocean based energy sources
in Malaysia is still in the beginning stages and in
the literature only few researches and studies were
found and most of them are limited studies and
assessment studies [3].
2.4 The Specifications of the Current
Turbine-generator System The main characteristics of the Low Speed Current
Turbine-Generator System are presented in the
following Table 1 below and a functional
dimensional principal sketch of the self-adjusting
and fixed blades or buckets of LS-VACT is shown
in Figure 4 and 5 respectively.
Fig 4: Schematic representations of self-adjusting blades
or buckets [13]
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Table 1: Specifications of the turbine-generator system Parameter Dimension Remarks
Turbine Principal Particulars
Turbine Diameter (DP) (m) 1
Bucket Diameter (d) (m) 0.35
Swept area (AS ) (m2) 0.525
Arm Length (Rotational
radius) (R) (m)
0.5 R = DP / 2
See fig 4.
Arm Length ( ) (m) 0.15 = R – d
Arm Length (lever) (r) (m) 0.325 r = R – d/2
Turbine Height 1.5
Number of Blades 4
Generator Specifications [21]
Rated Power Output (KW) 2
Rated Rotation (RPM) 180
Rated Voltage (V) DC 115
Rated Current (A) 17.4
Efficiency >85%
Required Torque 106.103
Starting Torque (Nm) 0.3
Weight (kg) 57
Fig 5: A functional and dimensional principal sketch of
the fiexed blades LS-VACT
3 Analytical Computation The turbine parameters and mechanical power were
computed using MATLAB M-File programming
using theory for primary turbine design and
estimations and by matching it with suitable
synchronous generator.
3.1 Determination of Turbine Dimensions
Determination of the LS-VACT dimensions is
based on the targeted generator size for private use
in remote areas with low speed current. However,
to feed a rural area which require a larger capacity
of electrical power, a group of generators of say, 2
KW each and attached to arrays of LS-VACT
turbines is a possible solution. As mentioned
earlier, one disadvantage of Vertical Axis Current
turbine type is that of having low TSR. Thus, it is
difficult to match it with the targeted generator due
to significant loss of torque after the gearbox (in
order to gain rotational speed). To solve this
problem an arm is added to the LS-VACT to
increase the torque and the following steps are used
to determine the arm length:
3.1.1 Input Data
1. Electrical generator:
PG = 2000 w, n2 = 180 rpm, TGreq. = 106.103 Nm,
Starting torque = 0.3 Nm
2. Environment:
U∞= 0.5 to 2.5 m/s, Water depth > 2.5 m and
ρ(Ocean) = 1025 kg/m3 and ρ(River) = 1000 kg/m
3
3. Gearing: speed-up gearing.
Gear ratio (K) = n2/n1 = 18.85 (max)
4. Turbine bucket diameter (d) = 0.35 m, bucket
height (H) = 1.5 m and total diameter (DP) = 1 m
3.1.2 Calculation procedure:
The arm of the turbine can be obtained by
following the steps below:
- Swept area of turbine, AS = d * H (1)
- Force acting on blade, F = Pressure*AS (2)
- Pressure = 0.5 * ρ * U2∞ (3)
- Gear ratio K = (nG / nT) or (n2 / n1) (4)
- The required torque of the turbine can be
obtained from the gear ratio relationship,
Treq. = K*TGreq. (5)
- The Arm is equal to: r = Treq./ F (6)
- Hence, T = Treq.- turbine torque (7)
- From the angular velocity, the turbine RPM is,
n1 = 30* ω / π (8)
From ω = 2 * π * n1 / 60 (9)
- The turbine power (P) = T * ω (10)
- Assuming that the Blade tip speed (u) = current
speed (Speed of incoming flow (U∞)) → u = R* ω
and u = U∞ so, R = U∞ / ω (11)
3.2 Matching the Turbine with the
Generator
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The arm and geometry of the LS-VACT turbine is
calculated based on the data of conventional
Savonius design modified by adding arms that
connect the two blades/buckets with rotor for
increasing the torque which leads to enhancing the
required generator torque after gearing
(transmission) and so improving the possibility to
produce power from the generator even with low
current speed. A Speed-up gearbox specification
used in this paper is shown in Table 2.
Table 2: Speed-up gearbox specification [22]
Type GK37
Input power (KW) 0.18 - 3
Transmission ratio 5.36 -106.38
Allowable torque (N.m) 200
Weight (kg) 11
4 Results and Discussion
4.1 Computation of Analytical Results The results of the turbine analytical design are
shown in the Table 3 below and Figure 6 shows the
mechanical power curve of the turbine. The torque
produced after gearing and generator outputs are
presented in Table 4 below:
Table 3: Analytical computation results for LS-VACT:
U∞
(m/s) r (m) RPM
T
(Nm) P (w)
Daily average
mechanical
energy (KWh)
0.5 0.325 9.549 21.86 21.86 524.64
1 0.325 19.099 87.45 174.89 4197.36
1.5 0.325 28.648 196.75 590.26 14166.24
2 0.325 38.197 349.78 1399.1 33578.4
2.5 0.325 47.746 546.53 2732.7 65584.8
Table 4: The 2KW -180 RPM generator output
Turbine
Torque
(N.m)
Gear
ratio
Torque
after
gearing
(N.m)
Output
(Watt)
Daily
average
energy
(Wh)
21.86 18.85 0.812 13.01 312.15
87.45 9.43 6.495 104.07 2497.63
196.75 6.28 21.920 351.20 8428.80
349.78 5.36 45.680 731.89 17565.46
546.53 5.36 71.375 1143.58 27445.97
Fig 6: Output curve of the turbine
4.2 System Output Energy The consumption of the loads and nominal power
are very important factors that play a major role in
stand-alone power system. The estimated
consumption of electricity for the Malaysian
household is approximately 2,200 kWh of energy
annually. In comparison with USA, a typical home
uses approximately 10,000 KWh of electricity per
year (about 830 KWh per month). Home energy
usage based on averages in two areas of the capital
of Malaysia is shown in Figure 7. As an
assumption, a rural household will consume about
75% of the estimated consumption of electricity for
the typical Malaysian household. A typical power
consumption reference for rural household and a
fish farm are shown in Table 5:
0
500
1000
1500
2000
2500
3000
3500
0 1 2 3
Tu
rbin
e M
ech
anic
al P
ow
er (
Wat
t)
Current Speed (m/s)
Power as function of current speed
Power (W)
Fig 7: Household energy consumption breakdown % [20]
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Table 5:Power Consumption Reference
Appliance
Load
power
(W)
Quantity
(pcs)
Daily
Working
Time (h)
Daily Energy Consumption
(Wh)
Power Consumption Reference for one Fish Farm
LED
Lamps 7 4 12 350
Laptop 90 1 12 1100
Fan 50 1 24 1300
Satellite
Receiver 25 1 18 500
LCD TV 70 1 18 1400
Rice
Cooker 500 1 0.5 250
Water
pump and
vacuum
1500 1 10 15000
Other 10 1 10 100
Total 1500 14 20000
Power Consumption Reference for one rural household
Led Lamp 7 4 12 350
Laptop 90 1 6 450
Desktop 120 1 6 750
Fan 50 2 12 1200
Satellite
Receiver 25 1 8 500
LCD TV 70 1 8 600
Rice
Cooker 500 1 1 500
Other 10 1 10 100
Total 775 10 4450
4.2.1 The Energy Produced by the System
The system energy is estimated based on:
Input Power:
P = 0.5 * ρ* AS* U3∞ (Watt) (11)
Operational Calculation:
Pm = T * ω (Watt) (12)
Output or Electrical Power:
Pe = T * ω * η (η=85%) (13)
Considering an average of 1 m/s current speed,
the daily average energy for one turbine is 2.5
KWh and the daily average energy for two turbines
is 5 KWh. The summary of energy produced by the
system is shown in Table 6 below:
Table 6: Average energy produced by the system
Description One
turbine
Two
turbines
Daily Average Output (W) = 104 208
Daily average output (KWh) = 2.5 5
Monthly average output (KWh) = 74.88 149.76
Annual average output (KWh) = 911.04 1822.08
At 1m/s of average current speed and working with
2 turbines would be sufficient to provide 5 KWh of
power for a rural house-hold. However, for a fish
farm that requires 20 KWh per day would need 8
turbines or a higher average current speed of 1.65
m/s.
Since current speeds vary, the use of batteries for
storing electrical energy is necessary. Based on the
power consumption from Table 6, the following
calculation for battery capacity required for
autonomy can be estimated;
Example 1: The small electric system of 8 current
turbines can supply daily 1 fish farm with energy of
20 KWh. The capacity (KWh) of a system with 8
batteries is;
Battery capacity = 8*250*12 (14)
= 24000 Wh → 24 KWh
This will give an autonomy time of 1.2 day.
Example 2: The small electric system of two
current turbines can supply energy daily for a
household for 5 KWh. The capacity (KWh) of a
system with 4 batteries is:
Battery capacity = 4*250*12 (15)
= 12000 Wh → 12 KWh
This will give an autonomy time of 2.4 days.
A set of 2, 2 kW current turbine electric system
(see Figure 8) will meet the needs of a house-hold
requiring 100 - 150 KWh per month in a location
with a 1 m/s annual average current speed.
Fig 8: LS-VACT Electric System Diagram
• Current speed
• 0.5 - 2.5 m/s
• RPM 10 - 48
• T= 25 - 550
• P = 21-2733
LS-VACT
• KG (η=70%)
• G. Ratio 5.36 -106.38
• T orque after gearing - 0.8 -75
Gear • 2 sets @ 2 KW
• P 15 - 1350 KW
• Daily Energy 0.5-65 KWh
Generator
•1 household (4
batteries)@ 1m/s
•1 Fish farm (8
batteries)@ 1.65
m/s
Load/
Battery
LS-VACT
Gear
Generator
Load
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ISBN: 978-1-61804-303-0 80
5 Conclusion The paper presents the development of a small-
current electric hydropower system which extracts
the energy from the kinetic energy of freely moving
low speed marine current and potentially can be
used for electrification of rural areas of Malaysia.
A system of a set of two current turbines of 2 kW
output capacities at 1 m/s average current speed is
proposed. Each turbine will produce daily energy
of about 2.5 KWh which can supply electrical
power for a household with autonomy time of 2
days (4 batteries storage). Higher electrical power
supply is possible with increase in number of
turbines or increase in current speeds. For a fish
farm, this would require either 8 turbines or
operating in an average current speed of 1.65 m/s
instead of 1 m/s.
In future, a simulation program will be
developed for predicting the performance of the
turbine and the system output. The simulated
results will be validated using laboratory and field
tests of a configuration involving arrays of turbines.
This will allow for possible increase in electrical
power supply and also investigating how each
turbine will interact with the wake from adjacent
turbines. The prediction tool will be developed
using Matlab-Simulink and will combine the
parameters of the low speed vertical current turbine
(LS-VACT), transmission system and generator in
order to determine the quality and the quantity of
the power output.
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3775800653813/2kw_low_rpm_vertical_ac_pmg
_alternator_permanent_magnetic_generator.html
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detail/Speed-up-Gearbox-for-Wind-
Turbine_60033905856.html
Fig 9: A Functional Principal Sketch of Off-Grid Marine Current Turbine Electric system
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ISBN: 978-1-61804-303-0 82