The FSEC Solar Thermal System Test Laboratory (STL) is used for performing tests of systems when the collector can not be easily isolated from the rest of the solar system and must be tested as a unit.

In the cases where the collector can be tested separately, those components are evaluated and measured in our solar thermal collector testing area.

The STL provides an area for heat loss and heat exchanger testing. These are the first series of tests on a system. The system is then moved to the rooftop area where it is tested for performance. The plumbing and instrumentation is routed to the STL below where there is a chilled and a heated water loop. The system is stabilized to a required temperature, exposed for a length of time, and then purged at the specified temperature to determine the heat gain.

Operation, monitoring, and data acquisition for the STL are under computer control. The purges are initiated electronically with solenoid valves.

Heating and Chilling

Two 240V, 9.5 kW instantaneous heaters with microprocessor-based PID temperature controllers are used to maintain stable water temperatures for testing. A 12,000 Btu water/water copper, heat exchanger which is plumbed directly into the chilled water loop of our facilities' central energy plant is used for water chilling. The chilled water temperature is adjusted with an electric valve actuator which is controlled by a microprocessor-based PID temperature controller.

Meteorological Station

The STL has a weather station on the roof directly above the lab. This station monitors the wind, ambient temperature, infrared, and solar incidence (horizontal, tilt and indirect). The data from this station is collected and processed by a computer.

Solar irradiance is measured with Eppley Laboratory Precision Spectral Pyranometers (PSP) mounted horizontally on a test stand in the rooftop testing area and on the collector stand in the plane of the collector.

The diffuse sky radiation is measured by an Eppley PSP used with an Eppley Shadow Band Stand which shields the sensing element of the pyranometer from direct solar radiation with an anodized aluminum band approximately 25 inches in diameter and 3 inches wide. The device is adjustable for latitude and solar declination. The Eppley PSP is rated as a first class instrument by the World Meteorological Organization. It meets all the requirements of ASHRAE 93-86 and 96-80 (solar collector testing standards).

Infrared radiation is measured with a pyrgeometer, the Eppley Precision Infrared Radiometer (PIR). A pyrgeometer measures the exchange of radiation between a horizontal blackened surface (the detector) and the target viewed (the sky). The (PIR) is designed to measure (unidirectional) incoming or outgoing long-wave terrestrial radiation. The instrument allows isolation of the radiation from the target impinging on the detector by automatically compensation for the detector flux.

Wind velocity across the system is measured using a three cup anemometer mounted in the rooftop testing area. The anemometer rotates a photo chopper which converts the rotation rate into electrical pulses. The frequency of the output signal is proportional to the wind speed. The variable frequency signal is converted to a DC voltage by the signal conditioning equipment in the systems laboratory and digitized by the Data Acquisition System. Specifications on the wind velocity instrument exceeds the requirements of ASHRAE 93-86.

Ambient air temperature is measured using a platinum resistance thermometer (RTD) mounted in a shield which is constantly aspirated with an electronic fan. The shield prevents direct solar heating of the RTD while allowing the flow of ambient across the sensor.

Data acquisition and laboratory control

All instrumentation for the laboratory is controlled by a Pentium processor based system using a National Instruments SCXI chassis, modules and DAQ boards. The process is automated using National Instruments "LAbView" graphical programming language. Temperatures are measured using platinum resistance temperature thermometers and type T thermocouples. Flow measurements are taken with turbine flow meters mounted in the fluid line. Flow is also calculated using two 2,000 lb. scales with digital weight indicators having an accuracy of 1:10,000. Flow is controlled using two positive displacement gear pumps with 1 H.P. motors and digital motor speed controllers.

Safety

The computer monitors the laboratory for several alert conditions. Devices are in place to detect overheating, flooding and over-pressurization. The system is designed to safely shut down if any of these conditions are detected protecting both the laboratory and any equipment currently under test.

Exposure and Pressure Testing

Systems are subjected to outdoor exposure in a fenced security area on site. Pressure testing and system check-in and inspection is performed in our high-bay area.

Calibration

All of the instruments in the laboratory are calibrated on a routine basis as recommended by the equipment manufacturer to maintain accuracy or as required by ASHRAE 93-86 or 96-80. In case of a conflict between the two recommendations the shorter time period will be used. In no case will the period between calibrations exceed one year.

Procedures

For detailed information on the procedures followed in our system and collector testing program please see FSEC's Testing & Certification site.

 

Solar Simulator

The FSEC high bay laboratory is equipped with a large-area solar simulator which simulates natural sunlight indoors for testing purposes. An 80,000 cfm fan also simulates wind at controlled speeds. This provides FSEC with the ability to perform repetitive tests under identical conditions for comparative purposes. The photograph at right shows the simulator, top left, being used to test a solar pool heating collector in FSEC's high bay laboratory.

The FSEC simulator can be used for a variety of testing, research, and calibration purposes. The simulator is available on a contractual basis to parties requiring specialized equipment testing. Calibration of radiation measurement equipment can also be performed using the simulator. The major advantage of testing equipment with the simulator is the ability to adjust the projected radiation as well as avoid delays caused by outdoor inclement weather conditions.

Simulator Description and Specifications

General description
Solar Light Source Arc Lamp System 
Lamphead 
Service Cabinet Cooling/Gas System 
Electrical Power System
Control System
Optical Reflector Assembly 
Mounting Structure 
Specifications 

General Description 

The FSEC Large-Area Solar Simulator, manufactured by Vortek Industries Ltd of Vancouver B.C. is a precision test facility designed to simulate natural sunlight indoors. 

It has a test area of 4.5ft x 12ft. The solar beam can be rotated 90° about its beam axis to allow the long axis of the test area to horizontal or vertical. The solar beam can also be oriented from horizontal to 45° down. 

Solar irradiance is continuously adjustable over the range 10 - 1500 W/m2. The average value does not vary by more than ±5% over any consecutive 10 hour period and ±3% over any consecutive 10 minute period. Collimation of the irradiance is such that 90% of the energy at any point on the test plane falls within a +10° angle. 

The solar spectrum is not affected by lamp life or irradiance level. Ultraviolet filtering is supplied to modify the UV spectrum. A water IR filter is provided. Long wave (thermal) infrared radiation (3.5 - 50 m) is negligible (<10 W/m2) 

The uniformity of irradiance on the test plane is ±5% peak-to-average over the central 4’ x 6’ region, and better than ±10% over the entire test plane. The uniformity of irradiance is not affected by lamp life or irradiance level. 

The light source is a single Vortek arc lamp surrounded by an optical reflector assembly to produce a solar beam. The Lamphead/Reflector assembly is coupled by flexible cables to a remote Service Cabinet. 

Solar Light Source Arc Lamp System

The Arc Lamp System consists of a Lamphead connected by a flexible umbilical cable to a remote Service Cabinet. The Service Cabinet contains the subsystems required to operate and cool the Lamphead. Operation of the Lamp is fully automatic under command of a microcomputer-based control system. Safety interlocks and an external computer interface are supplied as standard hardware. The operator has full control of start-up, shut-down and irradiance. System operation is monitored continuously and status is displayed on an operator's console. (Please click on picture at left for expanded version.)

Lamphead

The Lamphead produces continuous optical radiation in an electric arc operating in high pressure argon gas. The arc is vortex stabilized within a single quartz tube. Rapidly swirling water on the inner surface of this tube efficiently removes excess heat and prevents deposition of electrode material. This patented internal cooling method guarantees reliable operation at high powers. 

Assemblies at each end of the Lamphead house user-replaceable water-cooled tungsten electrodes. 

Service Cabinet Cooling/Gas System

Deionized water and argon gas are recirculated, filtered and cooled in the cooling/gas system. A pump circulates deionized water through an internal water-water heat exchanger in a closed loop system for cooling the arc lamp. Argon gas is also recirculated in a sealed, closed system.  (Please click on picture at left for expanded version.)

Electrical Power System

The service cabinet houses a DC power supply, high voltage igniter and microcomputer-based controller. The DC power supply consists of a water-cooled 3-phase SCR bridge rectifier with overload protection. Lamp ignition is accomplished by impressing high voltage from an internal igniter. 

Control System

The internal control system supervises start/stop sequencing, current regulation, and fault monitoring along with providing an operator interface and servicing support. 

Optical Reflector Assembly

The Optical Reflector Assembly (“Reflector”) captures light from the arc lamp and beams it uniformly onto the Test Plane. The positions of the optical surfaces are designed using a Vortek proprietary optical analysis program to accurately produce a solar beam of the specified uniformity and irradiance. 

The Reflector is rigidly mounted to the Lamphead. Interior sections of the Reflector are machined from aluminum alloy and internally water cooled. Optical surfaces are polished and protected with damage-resistant reflective coatings. Exterior Reflector sections are constructed of air-cooled glass mirrors. 

Mounting Structure

The Lamphead/Optical Reflector Assembly is mounted on a frame to permit 90° rotation of the assembly about the axis of the solar beam, and tilt of the beam from horizontal to 45° down. 

 

Specifications

Warm-up: 2 minutes or less to full stable output from cold start; 30 seconds or less from standby mode. 

Target Area: 4.5ft x 12ft 

Orientation: Solar beam is rotatable 90o about its beam axis. Long axis of target area can be horizontal or inclined vertical 

Beam Direction: Horizontal to 45o down, limited by height of test bay Irradiance Variable 10 - 1500 W/m2 

Long-Wave IR: 10 W/m2 or less for all wavelengths greater than 3.5m 

Uniformity: ±10% peak-to-average over entire target; ±5% peak-to-average over the central 4’ x 6’ area. 

Stability: ±5% peak-to-average over any consecutive 10 hour period, ±3% peak-to-average over any consecutive 10 minute period. 

Divergence: 90% of energy received at the target plane within a 20o full angle 

Target Distance: 35 ft from arc lamp 

Light Source: One (1) Vortek high-pressure argon arc lamp (Model 200-200/350) 

Cooling: Water 

Monitoring and Control

Type: Microprocessor-based 

Function: Programmable control and operator interface for irradiance temporal profiles 

Safety: Automatic shutdown and indication 

Outputs: External computer interfaces are available.