This paper presents an investigation on a novel enhanced direct flow evacuated tube solar collector system, which is used to charge a seasonal desiccant system for building heating and cooling. This type solar collector is designed as a novel fan coil heating pipe system to regenerate desiccants for dehydration process during summer. Proposed solar collector heating system is discussed and analysed within water and PCM storage tank on indoor tungsten halogen lighting and outside solar radiation. Numerical analysis and comparison of water and PCM tank system also is stated on the basis of properties of PCMs. Meanwhile, efficiency analysis method is utilised to evaluate the performance of this novel fan coil heating pipes system powered by solar collector integrated with PCM storage tank. The overall solar heating system efficiency is over 50% to transfer solar energy to heat desiccants on sunny days. However, it is about only 10% under mostly cloudy weather. For future work, appropriate phase change materials are required for storage tank due to their specific storage density. Also, heat transfer enhancement techniques (such as copper, aluminium, nickel, stainless steel and carbon fiber with various forms of fins or honeycomb) are required for internal PCM tank due to materials’ low thermal conductivities.