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Solar International Botswana (PTY) LTD.
Solar International Botswana (PTY) LTD. P.O. Box 149 - Gaborone
Corner Noko and Nakedi Road Broadhurst Industrial Plot 6384 Unit E Phone: 3182890 - Fax: 3182891 - Email: [email protected]
Light up your Farm and increase Farm Productivity
Options for Lighting Technologies
There are different ways in providing light. Maybe the best known method in rural areas is using the
light produced by flames. This may be an open fire from burning wood, a candle or a paraffin lamp.
All of these methods have in common that they generate heat, are smelly and form a health and fire
hazard. Because of these reasons people have switched to other methods of lighting. Where there is
access to the Botswana Power Corporation power
lines, electric power is conveniently and
economically used for lighting and powering
electrical appliances. Where BPC coverage is
lacking, electricity may be generated using diesel or
petrol generators. An alternative way of generating
electricity is using Solar Panels.
Some of the advantages is using Solar Electric
Systems compared to other lighting systems are:
� bright and steady light
� it may run your radio and TV
� no monthly electricity bill
� safe, no fire hazards
� no noise and no pollution
� long lasting.
How does a Solar Electric System work?
The sun’s rays can produce energy. When the rays hit a surface this energy may be released in the
form of heat (thermal energy). Solar water heaters, solar cookers and solar dryers harvest this
energy. When special materials are used, electricity is generated when the sun hits the surface of
that material. Solar Panels use this material to convert light from the sun directly into electricity
using the photovoltaic (PV) process. The higher the intensity of the sunlight, the more power is
produced by the Solar Panel. Also a bigger Solar Panel catches more sunrays and therefore
produces more power. In its most basic form, a Solar Electric System consists of four different
components: a Solar Panel, a battery, a regulator (controller) and one or more lights or other
appliances. For 230V lights and appliances an inverter needs to be added to the system. The
function of the different components is briefly discussed below.
Solar PanelThe Solar Panel generates 12VDC electricity directly from sunlight. The Solar Panel is
characterized by its power output expressed in Wp. Sizes vary from 3Wp to 300Wp. Two or more
Solar Panels can be wired together to increase the power output of the system. The electricity
generated by the Solar Panel charges a battery during the day. The panel is normally mounted safely
on the roof or pole by using a carrying structure.
Published in “Farming Magazine” October 2004 Issue
page
Solar International Botswana (PTY) LTD. P.O. Box 149 - Gaborone
Corner Noko and Nakedi Road Broadhurst Industrial Plot 6384 Unit E Phone: 3182890 - Fax: 3182891 - Email: [email protected]
2
BatteryAfter the sun has set, the battery provides the electricity that is required. During cloudy days, the
electricity generated by the Solar Panel will be less than during sunny days. However, the battery
can usually store enough electricity to cover up for a few cloudy days, while still supplying
electricity. Most batteries are 12V. The capacity of a battery is expressed in Ah (Ampere-hour).
Batteries can be wired together to increase the Ah capacity. In Solar Electric Systems low
maintenance batteries may be used, that do not require topping up of the electrolyte.
RegulatorThe regulator (also called controller) controls the charging state of the battery. It ensures that
electricity from the Solar Panel does not overcharge the battery and it also ensures that the battery
charge is not drained too much. The regulator often contains an interface with the user by means of
small lights (LEDs) that indicate the state of charge of the battery and system status. Its operating
voltage and current rating characterize a regulator.
AppliancesIt is important to use energy efficient lights with a Solar Electric System. High efficient Compact
Fluorescent Lights (CFLs) are commonly used. Note that CFLs for 12VDC systems are more
expensive than those for 230VAC systems. For a 12VDC system all appliances such as TV and
radio must be rated at 12VDC.
InverterAn inverter changes 12VDC into 230VAC so that AC appliances can be used with the Solar
Electric System. The inverter is characterised by its power rating (Watts) and waveform (square,
modified square or sine wave).
What Appliances can be used?
All kinds of different appliances can be used
with a Solar Electric System such as: radio,
TV, computer, printer, electric fan, cash
register, sewing machine, electric tools (drill,
grinder, etc.), kitchen machines (mixer,
blender, etc.), cell phone charger, refrigerator,
water purifier, etc. Appliances that produce
heat such as electric iron, kettle, stove and
heater require a lot of power and should
normally not be used with a Solar Electric
System.
Apart from the applications discussed above, Solar Panels may also be used to power pumps for
livestock watering and irrigation and electric fences for animal management. Furthermore the
energy from the sun may be used for aeration of ponds for aquaculture and fishing. Also new
developments have shown that solar lanterns may play an important role in pest control.
page
Solar International Botswana (PTY) LTD. P.O. Box 149 - Gaborone
Corner Noko and Nakedi Road Broadhurst Industrial Plot 6384 Unit E Phone: 3182890 - Fax: 3182891 - Email: [email protected]
3
How long will the equipment last?
Solar Panels have a warranty on output between 15 and 25 years, depending on the type of panel
used (mono-crystalline, poly-crystalline or amorphous) and on the manufacturer. Batteries should
last three years or more but lifetime depends a lot on the type of battery and its usage. Most
regulators are solid state and should last for over ten years under normal use. It is very important
that the system is not undersized and that high quality components are used in the system since this
will enhance its lifetime.
How does it compare?
Solar Electric Systems are often a cheaper option than new electric lines for providing power to
remote locations. And because they require no fuel and have no moving parts, they are more
economic and convenient to operate and maintain than diesel or petrol generators. In some areas,
the distance from a power source at which Solar Electric Systems become more economical than
new transformers and electric lines is surprisingly short—often as little as a few hundred meters.
These systems are a highly reliable and low-maintenance option for farm lighting, electric fences,
and water pumps. Although current prices for solar panels make them too expensive for most crop
irrigation systems, Solar Electric Systems are economical for remote livestock water supply, pond
aeration, and small irrigation systems.
For more information on Solar Electric Systems contact:
Solar International Botswana (Pty) Ltd.
P.O. Box 149 Gaborone
Corner Noko and Nakedi Road
Plot 6384 Unit E, Broadhurst Industrial
Tel: 3182 890 Fax: 3182891
Email: [email protected]