Emily Theokritoff
OPTIMISING THE DESIGN OF A HYBRID
SYSTEM IN RURAL TANZANIA
School of Engineering
Supervisor: Dr Stan Shire
Associate Professor of
Sustainable Energy Systems
Comparative study: Solar vs. Wind
What is a hybrid system?
Introduction
In September 2014, four Warwick students,
members of Engineers Without Borders,
travelled to Northern Tanzania to build a
hybrid system combining solar panels and a
wind-turbine. This system was built in
addition to the wind-turbine that had been
built by a previous group last year. Alongside, a
training program about the functioning of the
system and maintenance was taught to the
local co-operative. The hybrid system
provides electricity to the Secondary School of
Kemgesi, a rural off-grid village. The system
brings lighting to the girls’ dormitory, the
homework classroom and staff offices. They
now also have plugs to charge mobile phones
and laptops that we donated.
An energy system that utilises two or more energy
production methods, in this case and most
frequently solar and wind power, two renewable
energies.
Benefits:
• Peak operating times for wind and solar systems
occur mostly at different times of the day and year
so they are more likely to produce power when you
need it
Methodology
• Enhanced reliability of the system
Alongside the training program, a Hugh Piggott 1kW
wind-turbine was built. The blades were craved, coils
were winded for the stator, the rotors were set in resin,
the frame was welded, etc. Building the system with the
locals prepared them for future maintenance guaranteeing long-term benefits of the scheme. Testing days
provided data of the efficiencies of the components.
• A battery bank is available when neither wind or
solar systems are producing. The storage capacity is
sized to supply electric load between one and
three days
• Capturing energy that is freely available in the
wind and sun reduces impact on the environment
Findings
A wind-meter was installed in 2011, 500 meters
away from the actual site of the system. The
two years of data showed that the average daily
speed was 3.5 - 4m/s so we anticipate that one
wind turbine gives from 850 to 1000 kWh per
year, assuming 2kWh per day.
However, it is difficult to measure real
wind speed and one of our priorities in the
future is to implement remote monitoring. It is
challenging since there is no internet and very
poor phone network signal in the area.
Characteristics of one of the
4 polycrystalline solar panels
Module size (mm)
Weight (kg)
1005x670x35
9
Nominal power (W)
100
Max-Power Voltage (V)
18
Max-Power Current (A)
6
Monthly energy production at different
mean speeds of one wind-turbine
Turbine diameter (mm)
3000
Power rating (W)
800
Mean 3 m/s
34 kWh
Mean 4 m/s
85 kWh
Component of the system
Monthly production
Cost of purchase
Cost of kWh/month
2 kW wind-turbines
170 kWh/month
£ 4000
£ 23
400 W solar panels
120 kWh/month
£ 466
£4
Conclusion
9:30
15:30
Measurements of the solar output during different
times of the day, no remarkable variations
When testing the system and it was difficult to
analyse the actual efficiency and output of all of
the different technologies feeding into the battery
bank. Nevertheless, due to the irregularity of the
wind and the constant presence of the sun, I came
to the conclusion that solar was much more
advantageous in this region. In addition, the cost
of construction, installation and maintenance is
much more beneficial. One question that remains
unanswered is the actual life-span of these
technologies. The wind-turbine’s life span can go
up to 20 years if maintenance is performed
regularly but due to its moving parts and its
exposition to weather hazards this can be greatly
reduced. The solar panels have a 25 year warranty
on power output and performance but only time
will tell how they will resist.