ICPC Performance Testing at Sandia
Prior to the start of the 1998 Sacramento demonstration, individual fourteen tube modules were tested on Sandia National Laboratory’s two-axis tracking (AZTRAK) platform. See Winston et al . These tests measured losses from the new ICPC collector operating at about 150C on a 35C summer day of only 120w/m2 of collector aperture.
1.2 Sacramento Demonstration
A 100 m2 336 Novel ICPC evacuated tube solar collector array has been in continuous operation at a demonstration project in Sacramento California since 1998. The evacuated collector tubes are based on a novel ICPC design that was developed by researchers at the University of Chicago and Colorado State University in 1993. The evacuated collector tubes were hand-fabricated from NEG Sun Tube components by a Chicago area manufacturer of glass vacuum products.
From 1998 through 2002 demonstration project ICPC solar collectors supplied heated pressurized 150C water to a double effect (2E) absorption chiller. The ICPC collector design operates as efficiently at 2E chiller temperatures (150C) as do more conventional collectors at much lower temperatures. This new collector made it possible to produce cooling with a 2E chiller using a collector field that is about half the size of that required for a single effect (1E) absorption chiller with the same cooling output. Data collection and analysis has continued to the present [5, 6, 7]
Fig. 1: 1998 Daily Collection Performance for Fig. 2: 1998 Daily Collection Performance for
Operation at 90 to 110C Collector to Ambient Operation at 110 to 130C Collector to Ambient
Temperature Differences. Temperature Differences.
As can be seen in Fig. 1 and 2, the nontracking ICPC evacuated solar collector array provided daily solar collection efficiencies (based on the total solar energy falling on the collector) approaching fifty percent and instantaneous collection efficiencies of
about 60 percent at the 140C to 160C collector operating temperature range. Daily chiller COPs of about 1.1 were achieved. The ICPC array has recently been operating at the lower temperatures to drive a single effect absorption chiller. The ICPC array has provided daily solar collection efficiencies approaching
fifty-five percent at the 80C to 100C collector operating temperature range.