Development and thermodynamic analysis of a novel heat pipe vacuum tube solar collector with sensible heat storage

A novel heat pipe vacuum tube solar collector has been developed and experimentally investigated for sensible heat storage in different climatic conditions. The solar collector has been introduced with a new header where heat transfer fluid (Therminol-55) gains heat directly in contact with the condenser section of heat pipe. This eliminates the application of thermal paste between condenser and manifold in existing systems. Thermal performance of the system has been evaluated with a heating load of 30 L of Therminol-55 in three consecutive months (March, April, and May) to check its maximum and average performance. Maximum temperature has been found as 145.8 degrees C, 153 degrees C, and 151.2 degrees C in March, April, and May respectively. Maximum energy efficiency has been observed as 44.7%, 24.3%, 23.4%, and maximum exergy efficiency has been observed as 3.1%, 3.3%, and 2.6% in March, April, and May respectively. Average energy efficiency for the whole duration of experiment has been determined as 12.1%, 8.3%, 8.4%, and average exergy efficiency has been determined as 2.1%, 1.9%, 1.8% in March, April, and May respectively. The results suggest utility of the developed solar collector for consistent use in daytime for medium temperature solar heating applications.