FOR SOLAR-TRACKING AND

PC-BASED POSITIONING OPERATIONS

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

Introduction

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.

Applications

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

dimming.

BSRN comprises a global network of solar monitoring

stations

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

as WMO-GAW, ARM, GEWEX and GCOS.

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

Pyrheliometer

Pyranometer

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

Pyrheliometer,

with temperature sensor

Pyranometer, ventilated,

with temperature sensor

Pyranometer

(shaded), ventilated,

with temperature sensor

direct solar radiation

global solar radiation

diﬀuse solar radiation

Pyrgeometer

(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)

N/A

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)

N/A

Features

Transmission Inverted tooth belts Worm and bevel gear

Options

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.