Overview
The document describes a new range of vacuum tube collectors with parabolic reflectors designed for efficient solar energy collection. These collectors are capable of withstanding frost temperatures as low as -18°C due to their high-grade vacuum insulation.

Specifications

• Model: Calpak 14 VTN
• Dimensions: 1610 mm (length) x 1600 mm (width) x 110 mm (height)
• Weight: 41 kg
• Gross Area: 2.50 m²
• Aperture Area: 2.27 m²
• Number of Tubes: 14
• Glass Cover Tube: 47 mm diameter, 1500 mm length, made of borosilicate glass
• Vacuum Pressure: < 0.005 Pa
• Absorber Material: Copper tubes with aluminum fins
• Absorption Coefficient: > 0.92
• Emission Coefficient: < 0.08
• Fluid Content: 3 liters
• Heat Transfer Medium: Water or Glycol brine
• Insulation Material: Fiber glass and expanded polyurethane
• Casing Material: Aluminum
• Maximum Temperature: 220°C
• Maximum Operating Pressure: 10 bar
• Pressure Tested: 15 bar
• Output for Germany (Würzburg): 525 kWh/m²/year
• Certification: EN 12975-2 / ISO 9806-1

Design Features
The collectors feature a parabolic reflector made of highly reflective aluminum, enhancing efficiency by concentrating solar radiation onto the tubes. The inner part of the vacuum tube contains a U-shaped copper tube with an aluminum fin for heating the system's water or brine.

Performance
The document includes an instantaneous efficiency curve for the Calpak 14 VTN collectors, indicating performance metrics under varying conditions.

Construction Layout
The layout includes outer and inner glass tubes, an aluminum fin, a U-form copper tube, and a vacuum space, all contributing to the collector's efficiency and durability.