Accuracy suitable for any requirement
All-weather construction
Unattended operation
Virtually maintenance-free
Wide range of mounting configurations
Ideal for BSRN stations
Sun Trackers
System Configurations
Solar radiation is normally measured using a pyranometer
that sees the whole hemisphere above it and responds to
radiation from both sun and sky, the ‘global’ solar radiation.
However, it is often necessary to accurately measure the
‘direct’ radiation coming only from the sun.
A pyrheliometer has a 5 ° view, slightly larger than the sun
and its aureole, and does not see the rest of the sky. To
make measurements it must point precisely at the sun and
this is achieved using an automatic two-axis sun tracker. A
shading assembly blocks the direct solar radiation from
reaching a pyranometer mounted on the tracker so that the
‘diffuse’ solar radiation from the sky can be measured.
The sun tracker provides a stable mounting for the pyrheliometer
and moves horizontally (azimuth) and vertically (zenith) to
follow the solar arc. Stepping motors controlled by a micro-
processor drive through belts or gears to provide movement
with the desired torque and accuracy. An on-board programme
requires accurate longitude, latitude, altitude, date, and time
information for the measurement site. It then calculates the
current position of the sun and points the pyrheliometer and
shading assembly towards it.
Sun trackers are widely used in networks of solar monitoring
stations that measure direct, diffuse and global radiation,
for inputs to weather forecasting and climate models. Other
applications include atmospheric chemistry research,
pollution forecasting and materials testing.
With growing interest in renewable energy good quality
solar radiation data is becoming increasingly important,
particularly the direct component, with regard to photovoltaic
systems and thermal energy solar collectors. Activities
include research and development, production quality
control, determination of optimal power plant locations,
monitoring the efficiency of installed systems and predicting
the output under various sky conditions.
The Baseline Surface Radiation
Network (BSRN)
Solar, atmospheric and terrestrial radiation drive almost
every dynamic process on the Earth’s surface and above, from
ocean current circulation to weather, climate and life itself.
Small changes can have large and long-lasting effects that are
difficult to predict. Accurate data regarding the radiation at
the Earth’s surface is fundamental to under-standing its
climate system, global warming and global
BSRN comprises a global network of solar monitoring
using the best equipment and practices currently available
and is a key part of the World Climate Research Programme.
BSRN is linked to other international climate projects such
Kipp & Zonen sun trackers and radiometers are widely used
in all of the above programmes and we can supply complete
BSRN compatible solar monitoring systems.
Choice of Sun Tracker
2AP has been in production for many years and is used around
the world as the basis of top quality solar monitoring stations
for research and in networks, such as BSRN. The high power
and rugged design enables operation in extreme conditions,
from deserts to Antarctica.
However, not every customer needs these capabilities and for
some users 2AP is over-specified. Our SOLYS 2 provides BSRN
level performance and is easier to install and operate than
any other tracker on the market. It is very efficient and ideal
for operation using solar energy power sources.
Sun Tracker
Shading Ball Assembly
Pyranometer (shaded)
direct solar radiation
global solar radiation
diffuse solar radiation
Data Logger
Typical Solar Monitoring System
Sun Tracker sun sensor recommended
Shading Ball Assembly
with temperature sensor
Pyranometer, ventilated,
with temperature sensor
(shaded), ventilated,
with temperature sensor
direct solar radiation
global solar radiation
diffuse solar radiation
(shaded), ventilated
downwards infrared radiation
Basic BSRN Station
Data Logger
SOLYS 2 is an advance over conventional automatic sun trackers. It
does not require a computer and software for installation. The
integrated GPS receiver automatically configures location and time
data. Multi-colour LEDs indicate the operating status and an Ethernet
port allows for software upgrades, testing and fault diagnosis. The
high-efficiency belt drive system requires no maintenance.
The tough and distinctive cast aluminium housing has a matching
tripod stand with levelling feet. A side plate with mountings for a
Kipp & Zonen pyrheliometer is included as standard and a second
side plate can be fitted, with a range of mounting kits for an
additional pyrheliometer or other instruments. Two top mount-
ing plates are available for convenient horizontal mounting of
one, or up to three, Kipp & Zonen radiometers. The shading ball
assembly accessory includes the large top mounting plate and a
second side plate and allows SOLYS 2 to be configured as a
complete solar monitoring station.
SOLYS 2 does not suffer from internal clock drift because time
is updated by the GPS receiver. A sun sensor is available for
active tracking where the stability of the support platform
cannot be guaranteed.
2AP has proven performance in the harshest climates. High
power motors and precision gear drives have the torque to
break ice and to operate in high winds. The optional cold
weather cover and internal heaters enable operation down to
-50 °C. After setup using the supplied Win2AP software and a PC
(not included) operation is stand-alone with only occasional
checks of the internal clock required. Two small side plates are
included as standard, but no instrument mountings.
An active tracking sun sensor is available to correct for clock drift
or movement of the support platform. The large side mounting
plate takes the sun sensor and a Kipp & Zonen pyrheliometer (or
two pyrheliometers). The optional shading ball assembly
includes two side plates and a rear mounting plate for up to three
ventilated Kipp & Zonen radiometers. Adapters are available for
unventilated radiometers.
A unique feature of the 2AP is the positioning capability. The
Win2AP software can be used to configure a sequence of
pre-programmed movements to point at a series of targets.
The cost-effective and simple sun tracking solution.
Fully Automatic
Integrated GPS Receiver
Easy to Install
BSRN Level Performance
Both AC and DC Power Inputs
Very Low Maintenance
The high-end market leader for all conditions.
Highest Accuracy Available
Highest Load and Torque Available
BSRN Level Performance
AC and DC Power Versions
Operates in Extreme Climates
Positioning Capability
Operating temperature range -20 °C to +50 °C (DC power)
-40 °C to +50 °C (AC power)
0 °C to +50 °C
-20 °C to +50 °C with optional cold cover
-50 °C to +50 °C with optional cold cover and optional heater
Payload (balanced) 20 kg 65 kg
Angular velocity up to 5°/s up to 1.8°/s
Weight 23 kg (sun tracker), 5 kg (tripod stand) 30 kg
Dimensions (WxDxH) 50 x 34 x 38 cm (excluding tripod stand) 42 x 26 x 38 cm
Angular acceleration
Conditions & Dimensions
Supply voltage
up to 3.6°/s²
18 to 30 VDC and
90 to 264 VAC, 50 / 60 Hz
up to 3.6°/s²
Power sun tracker 21 W (reduces to 13 W at night) 50 W
Power heater 100 W (heater is standard, AC only) 100 W (heater is optional)
24 VDC only, or
115 / 230 VAC
(selectable), 50 / 60 Hz
Side mounting plate For fitting to zenith axis shaft on opposite side
to standard side plate / pyrheliometer mounting
Large side mounting plate for zenith axis
including mountings for two pyrheliometers
Pointing accuracy < 0.1° passive tracking
< 0.02° active tracking
(with optional sun sensor)
< 0.1° passive tracking
< 0.02° active tracking
(with optional sun sensor)
Torque > 20 Nm (at maximum load and angular velocity) *
> 23 Nm
(when sun tracking) *
> 40 Nm
(at maximum load and angular velocity)
> 40 Nm (when sun tracking)
Large top mounting plate 3 positions for Kipp & Zonen radiometers
(with or without ventilation units)
Shading ball assembly Includes large top mounting plate, second side
mounting plate, 2 shading balls on adjustable rods
Includes rear mounting plate for 3 Kipp & Zonen ventilated radiometers,
two large side mounting plates, 3 shading balls on rods
Small top mounting plate 1 position for a Kipp & Zonen radiometer
(with or without ventilation unit)
Transmission Inverted tooth belts Worm and bevel gear
Sun sensor kit For active sun tracking For active sun tracking
Adapter kit Not needed
Radiometer mounting kits
Note: The performance specifications quoted are worst-case and/or maximum values
For absolute cavities, pyrheliometers, PGS-100 sun photometer and other instruments
For unventilated radiometers
Location, time/date info & setup Automatic by integrated GPS Manual by Win2AP software and PC (not included)
Mounting base Tripod stand included Flat base plate (optional heavy duty tripod stand and height extension tube)
Zenith axis fittings One side plate / pyrheliometer mounting kit standard Two small side plates standard, no mounting kit
Heater for low temperature operation Standard (AC power only) Optional (must be used with cold cover)
Communication Ethernet and web interface RS 232 and Win2AP software for PC (not included)
Indicators Power, internal temperature and status N/A
Ethernet and web interface By Win2AP software and PCPositioning mode
Maintenance No scheduled maintenance required Annual inspection and grease gears
Specifications 2APSOLYS 2
* The standard torque setting is ideal for all normal measurement applications, but it is adjustable in firmware. Torque can be reduced to save power, or increased
to a maximum of 30 Nm when sun tracking.