How robust are the small scale technology certificates calculations for solar hot water systems derived from the trnsys calculations?

The Mandatory Renewable Energy Target concept (MRET) operating under the Large Scale Renewable Energy Target (LRET) and the Small Scale Renewable Energy Target Scheme (SRES), as from January 2011, aims at reducing the carbon footprint of Australia by harnessing the abundant renewable energy sources in the country. The method employed by the two schemes to attain the goal is through the creation of certificates based on the amount of electricity generated by renewable energy power sources or displaced by solar water heaters and heat pumps. The certificates earned under the SRES is the small scale technology certificates (STCs) and the approach used to evaluate the performance of solar water systems under this scheme is as given in the AS 4234 which uses the TRNSYS simulation program to determine the amount of STCS gained by these systems. The aim of this project was to determine the performance of the pumped instantaneous gas solar water heater and the thermosyphon gas solar water heater in zone 3 and 4 of Australia as per the AS 4234. The project involved the use of the TRNSYS 15 simulation program to calculate the amount of STCs gained by these two solar systems. The major inputs to the simulation namely the TRNSYS deck files were provided at the Clean Energy Regulator website. A sensitivity analysis was also carried out whereby the various input parameters of the two systems considered were varied by +/-10% and their impact on the amount of STCs gained were noted. The results of the study show that higher number of certificates would be produced in Zone 3 compared to Zone 4 of Australia. The study also shows that the thermsyphon gas system has a better performance than the pumped instantaneous gas system. The major parameters found to be sensitive in the STCs calculations are the area of the collector, the efficiency of the collector as well as the efficiency of the gas in the gas booster. Input parameters such as the heat loss of the tank and the start up capacity of the gas in the gas booster are also found to have considerable impact in the STCs calculations