Sixty plus cumulative years of operational commercial solar trough installations and sophisticated destructive and wind tests have given IST an unequaled technological experience base and the RMT meets IST’s high standards for innovative and highly reliable concentrator designs. 

RMT system applications include:

• Water heating
• Industrial process heating
• Building heating and cooling
• Boiler make up water heating
• Steam generation

RMT projects should aim to have at least 1120 ft² of collector area (32 modules) with a peak output of about 180,000 Btu/h (52 kW_th). RMT concentrators are an ideal energy source for hot water powered single or two-stage absorption chillers from 10 to 200+ tons of capacity.

Specifications – IST Roof Mounted Trough (RMT) System

Reflective Module Size             120.75 in. x 45.2 in. (3067 mm x 1148 mm)

Gross Aperture Area                37.9 ft² (3.52 m²)

Net Aperture Area                   35 ft² (3.25 m²)

Concentrator Weight                55 lb (25 kg)

Materials of Construction          Aluminum

Reflective Surface                     Coated polished aluminum

Receiver
Solar energy focused and concentrated on a liquid-filled receiver dramatically reduces convection and conduction thermal loses. The receiver/absorber is a steel tube coated with a selective blackened nickel surface and surrounded by tough Pyrex^â glass.  IST treats the glass annulus with a sol-gel anti-reflective coating that increases light transmission to the absorber.

Steel Absorber Tube                                   1.0 inch (25.4 mm) OD

Selective Blackened Nickel Surface

Absorptance                                       0.96-0.98

Emittance (80^oC)                                0.15-0.25

Envelope Material                                        Borosilicate glass, 51 mm OD

Envelope Transmittance                               0.95-0.965

Maximum Operating Temperature                400^oF (204^oC)

Drive and Controls
Controlled by Honeywell Fluxline Control System, the collectors track the sun continuously during the day. A single drive motor in IST’s unique multi-row design can operate four rows of eight RMT modules, which eliminates many moving parts and increases reliability. The microprocessor monitors safety devices that measure sun, wind, fluid flow and system temperatures. System operating data can be recorded for local or remote computer access. The drive system stores the concentrator upside down in the “stow” position in high winds and at night to protect the reflective surface and the receivers

Flexible Hoses

Fully insulated flexible hoses deliver thermal heat transfer fluid to the receiver from the fixed field piping. The flexible hoses, of proven design and expected life in excess of 15 years, accommodate the tracking motion of the receiver.

 

IST RMT System at Fort Sam Houston, San Antonio, Texas

The RMT trough system at Fort Sam Houston, San Antonio, Texas came on line in June 2003. It provides solar thermal energy to a pressurized water district-heating loop that delivers heat for showers, building space heat and air-conditioning reheat to a number of buildings at the Army medical base.

The solar collector system is installed on the roof of Building 902. It consists of 129 RMT modules with a total net aperture area of 4,515 square feet. The collectors are arranged in nine parallel rows with either 14 or 15 modules in a row.  A total of six drive motors automatically track the collectors continually during the day. Two drive motors are controlled by each of the three local controllers. The local controllers communicate with a single master controller that regulates the operation of the entire system in response to weather conditions: sun and wind; and operational parameters: temperatures, flow and pressure.

The solar collector system delivers heat to the district-heating loop through a heat exchanger (see diagram). The large volume of water in the heating loop provides thermal storage so that solar energy is delivered for some time after the sun goes down.  

IST manufactured and installed the solar collectors as a subcontractor to Johnson Controls, Inc. The entire project was installed under a base-wide Energy Service Performance Contract (ESPC) with the US Army aimed at reducing fuel consumption and saving money for the federal government.