A stand-alone solar lighting
system for electrodeless fluorescent lamp
Yuming Chen1，
Amy Wang2 and Weide Li2
1 Institute for Electric Light Sources, Fudan University, Shanghai
200433, China
2 Shanghai Hongyuan Lighting & Equipment
Company, Shanghai 201802 , China
Abstract:
A stand-alone solar lighting
system for electrodeless fluorescent lamp was introduced, which is a
combination of solar PV technology with electrodeless fluorescent
lamp. The design of the system and the requirements of the
components were discussed. With the proper design the whole system
can have long life and free maintenance, which can save the cost and
energy practically and realize the sustainable lighting.
Introduction
Rising electricity and oil
prices, together with increased environmental awareness have led to
increased global incentives for solar power system. The stand-alone
photovoltaic lighting system has draw much attention because of
energy-saving and convenience.? The electrodeless lamp combines the
fluorescent lamp technology with high frequency electromagnetic
induction, which make it has many advantages, such as long life and
high lumen maintenance. In order to reduce the power dissipation
during the transfer from battery to lamp, a dc ballast for lamp was
developed. The considerations for design a optimized solar PV
lighting system was discussed. The system contains solar cell panel,
battery, lamp, ballast and control system. The requirements of these
parts have been analyzed. We have found in our experiments in order
to realize energy-saving and environment-protecting the system must
be optimized. With the proper design the whole system can have long
life and free maintaince, which can save the cost and energy
pratically. In the future the stand-alone solar PV lighting system
can be widely used and realize the sustainable lighting.
Electrodeless fluorescent lamp
The
electrodeless fluorescent lamp is fundamentally different from the
traditional fluorescent lamps, which employ electrodes as? electron
source[1].? The operation frequency of electrodeless fluorescent
lamp can be designed in the range of hundreds of KHz to tens of MHz
which can be produced by a high frequency generator (ballast). And
the electrodeless fluorescent lamp have many advantages, such as
long life, high efficacy etc[2,3,4].? Here we introduce the
performance of a dimmable electrodeless fluorescent lamp – a
ring-type electrodeless fluorescent lamp, which employs IC chips in
the ballast .
The ring-type electrodeless fluorescent lamp
consists of three parts, the high frequency generator (ballast),
energizing coils and the discharge tube. The schematic construction
of the ring-type electrodeless fluorescent lamp is shown in Figure
1. The high frequency generator is responsible to generate high
frequency current (230 KHz at rated power in this design). When the
high frequency current flows through the energizing coils wrapping
around the ferrite cores, inductive electric field is produced to
sustain the gas discharge. The two energizing coils are positioned
in parallel with each other, and the turns of the coils are
determined by the power of the lamp specifications[5]. Discharge gas
is composed of Mercury and Argon as the buffer gas. The pressure of
Mercury is controlled by the main amalgam. Several assistant
amalgams are posited close to the ferrite core to help quick
ignition.
Figure 1. The schematic diagram of the lamp
The electrodeless lamp can have much longer life in the PV lighting system than other lamps because of its no electrode structure. The electrodeless fluorescent lamp can work more stable with the variation of input voltage. In order to improve the efficiency and reduce the cost, a DC ballast was designed for the lamp for the PV lighting system. The structure of the ballast was illustrated in Figure 2. The ballast can connect to the battery directly without adapter, which can reduce the electricity loss about 5%. The electrodeless fluorescent lamp is a good candidate for the solar lighting system.
Figure 2? The structure of the DC
ballast
Solar lighting system
A stand-alone solar
lighting system can mainly divide into 4 parts (see figure 3).The
solar cell is used to turn the sunlight into electricity; the
controller is the heart of the system, it can control the charge
between solar cell and battery and the drive of the battery to the
load, in addition many protection should provide.
Figure 3? The solar lighting system
Design the solar lighting system, first we should calculate the electricity consumption of the lamp per day:
----------------------------------------------------（1）
?---------------------------------------------（2）
Where He is the average radiation hours under standard intensity
which can derived for the local Solar Energy Daily Radiation
Ht（He=Ht×2。778/10000（h）），Kc is the angle factor, Cz is correction
factor for system decay, normally use 0.8, ηis the conversion
efficient of system , normally use 0.95, Uf is the floating voltage
of the battery，Nc is the longest rainy days.
The battery capacity
can also be obtained by following expression
---------------------------------------------（3）
Where A is safe factor , which in the range from 1.1 to 1.4, TO is temperature correction, usually above 0℃ use 1，above -10℃ use 1.1 and below -10℃ use1.2, CC is the depth of battery discharge .
Some considerations
The angle of the solar
cell is very important , the solar cell panel should just face south
which can get the largest electricity, and the elevation angle is
decided by the local latitude[6]. If the elevation angle is small it
will cause many problem, such as the dusty will deposit on the panel
surface which may destroy the whole panel from the hot spot. So in
the real applications the elevation angle of the solar panel should
above 30 degree.?
The controller is the heart of the system, in
order to ensure the life of the system, the controller must refine
the discharge/charge function to prolong the battery life[7,8]. The
controller should have following functions:
- anti-reverse charge
Anti-reverse charge is very important to the whole system, it can easily realize with Schottky Diode. A better design is using Mosfets, but the circuit is more complexity.
- Anti-over charge
The controller can limit the charge current after the battery reach the floating voltage, the surplus energy can leak with transistor switch.
- Anti-over discharge
The discharge should stop when the battery voltage drop to setting voltage, in order to ensure the life of the battery, the setting voltage should be a little bitter higher, for example the lead acid battery is 11V.
- Temperature compensate
The temperature can effect the performance of the battery obviously, if the environment temperature vary between large range the temperature compensate must applied, for example the single lead acid battery is -3~-7mV/℃，we usually use -4mV/℃。
Conclusion
The electrodeless fluorescent lamp
can have long life and good performance with DC ballast.? Combining
the solar lighting technology and electrodeless fluorescent lamp ,
the life of stand-alone solar lighting system can be ensured.
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