Solar cells in practice
• Solar cells have been proven to be reliable for supplying power for installations and devices in remote
locations. It is recommended that solar cells are used when there is no mains supply is available. There
are also many possible areas of application for hobbies. For example, powering small electrical devices
such as radios, toys, watches, charging devices etc. and also for wider leisure time use, gardening and
camping activities.
•
Solar cells are available in different shapes (round, angular) and colours. These feature do not influence
the performance.
• Individual solar cells have a plus pole (top side) and a minus pole (the whole bottom) and can be con-
nected in any order (soldered).
• The solar cell is formed from silicon crystals. However, silicon is a very brittle material and breaks easily
at very low mechanical loads. Therefore it is very important to handle it with care.
• Single solar cells generate a nominal voltage of about 0.5 V. The power depends on the size of the cell.
• In order to increase the voltage and power, multiple solar cells are combined into solar panels. These are
most often assembled on a frame with a cover in order to facilitate mounting.
Construction of a solar installation
A solar installation consists in the main of the following
components:
1. Solar panel
2. Charge controller or return protective diode
3. Energy storage
4. Consumer
•
With sufficient illumination, the solar panel provides
electrical power. A charging controller recognises the ideal time for the operation of the solar panel and
controls the charging current for the energy storage (rechargeable battery) highly effective.
• In simple systems, only one return protective diode is normally included. A diode only allows the current
to travel in one direction. This prevents the stored energy from being discharged via the solar cell when
there is not sufficient illumination.
a) Power curve for solar cells (at </= 25°C)
•
If too much current is drawn, the voltage will break down (poor efficiency), if
too little current is drawn, the installation and the potential energy is not utilised
(poor efficiency).
• When there is no load, a solar cell provides a maximum voltage of approx.
0.55 V/DC that decreases with increasing load. The maximum power is
reached with a cell voltage of 0.45 V.
•
The ambient temperature has a significant influence on the performance. The
following values show the effect of a temperature rise exceeding 25°C per solar cell:
- Voltage decreases by approx. 2 mV/°C
-
Current decreases by approx. 25 μA/°C
-
Efficiency decreases by approx. 0.3%/°C
• The nominal data for a solar cell normally refers to an ambient temperature of </= 25°C and a solar
power of 1000 W/m2. This is reached in the summer when there is no cloud cover and the sun is
overhead. The solar panel should always be aligned at 90° to the sun, in order to achieve the maximum
energy generation.
Applications for solar cells
In order to use solar cells effectively in practice, the single cells are connected together to produce high-
performance solar panels. For this three different methods are used. In all of them, however, only the same
type of solar cells (same size, type and power) should be used.
a) Series connection (increased voltage)
In series connection, the cells are connected consecutively from plus pole to minus pole. This type of con-
nection makes it possible to increase the voltage. Each extra cell increases the voltage by approx. 0.45 V.
The current, however, remains at the value for a single solar cell.
b) Parallel connection (increased current)
In parallel connection, the cells are connected in parallel i.e. from plus pole to plus pole and minus pole to
minus pole. This type of connection makes it possible to increase the current. Each extra cell increases the
current. The voltage, however, remains at the single cell value.
c) Combination of series and parallel connection (increase in performance)
• The best and most effective kind of connection is a combination of series and parallel connection. In this,
several series-panels are connected together to further parallel panels. This has the advantage of both
methods: Increase in voltage and current = increase in power.
All modern solar panels use a combination of both these kinds of connection.
• In practice, solar panels are normally used in combination with an energy storage such as NiMH or
lead rechargeable batteries. Doing this balances the power fluctuations caused by changes in light
(clouds, bad weather, darkness etc.).
Operating Instructions
Solar Demo Set
Item No. 2315349
Intended use
The Demo Set allows experimental trials concerning the topic power generation by solar energy. It demon-
strates how solar cells function and their use and application in daily live. With sufficient illumination the set
generates a nonhazardous safe low-voltage. Touching the contacts during use is totally harmless.
For safety and approval purposes, you must not rebuild and/or modify this product. If you use the product
for purposes other than those described above, the product may be damaged. In addition, improper use can
result in other hazards. Read the instructions carefully and store them in a safe place. Make this product
available to third parties only together with its operating instructions.
This product complies with the statutory national and European requirements. All company names and prod-
uct names are trademarks of their respective owners. All rights reserved.
Delivery content
• Solar panel (max. 400 mA/0.45 V/DC)
• Solar motor with propeller
• Operating instructions
Up-to-date operating instructions
Download the latest operating instructions at www.conrad.com/downloads or scan the
QR code shown. Follow the instructions on the website.
Explanation of symbols
The symbol with the exclamation mark in the triangle is used to indicate important information in
these operating instructions. Always read this information carefully.
The arrow symbol indicates special information and advice on operation.
Safety instructions
Read the operating instructions carefully and especially observe the safety information.
If you do not follow the safety instructions and information on proper handling in this
manual, we assume no liability for any resulting personal injury or damage to property.
Such cases will invalidate the warranty/guarantee.
a) General information
• The device is not a toy. Keep it out of the reach of children and pets.
• Do not leave packaging material lying around carelessly. This may become dangerous playing
material for children.
•
Protect the appliance from extreme temperatures, strong jolts, flammable gases, steam and
solvents.
• Do not place the product under any mechanical stress.
• If it is no longer possible to operate the product safely, take it out of operation and protect it
from any accidental use. Safe operation can no longer be guaranteed if the product:
- is visibly damaged,
- is no longer working properly,
- has been stored for extended periods in poor ambient conditions or
- has been subjected to any serious transport-related stresses.
• Please handle the product carefully. Jolts, impacts or a fall even from a low height can dam-
age the product.
• Single solar cells can be easily broken by low mechanical loads. This will result in sharp and
pointed pieces. Therefore, be especially careful when children are around.
• When connecting multiple solar cells in series (construction of big panels) a voltage of > 75 V/DC
(direct current) can be generated! Above this voltage it is possible to get a fatal electric shock,
if you touch the electrical conductors.
• In commercial institutions, the accident prevention regulations of the Employer’s Liability
Insurance Association for Electrical Systems and Operating Materials are to be observed.
• Consult an expert when in doubt about the operation, safety or connection of the appliance.
•
Maintenance, modifications and repairs must only be completed by a technician or an au
-
thorised repair centre.
• If you have questions which remain unanswered by these operating instructions, contact our
technical support service or other technical personnel.
b) Connected devices
• Also observe the safety and operating instructions of any other devices which are connected
to the product.