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Solar electricity that is produced from photovoltaic solar systems has the potential to deliver clean sustainable energy. Positive steps are being undertaken to minimise greenhouse gas emissions in Australia and photovoltaic solar systems are contributing towards sustainability. The current amount of installed photovoltaic solar systems cannot address the global warming issues in whole, however renewable energy production is contributing towards minimising carbon emissions. One of the main concerns for the residential householders is the economic issue on the use of photovoltaic solar systems. This paper examines life cycle cost effectiveness in using photovoltaic solar systems with capacities ranging from 1.5 kW to 5 kW in relation to the number of occupants and consumption for residential dwellings over a 25-year period. Eight major cities in Australia, including Sydney, Canberra, Melbourne, Brisbane, Hobart, Adelaide, Darwin and Perth, are investigated. Life cycle cost comparisons among different types of electricity grid connected systems, including a gross-feed-in-tariff (GFIT) scheme, a net-feed-in-tariff (NFIT) scheme and a buy-back scheme, are also explored. It is found that all major cities can receive life cycle cost saving in installing photovoltaic solar systems in their residential dwellings. The life cycle cost saving is between $273 and $53,021 and the percentage of cost saving is between 0.35% and 123.83% in a 15-year period. It appears that the GFIT and NFIT schemes offer better benefits than the buy-back scheme in installing photovoltaic solar systems. It is also found that the higher the capacity of the photovoltaic solar systems, the higher the life cycle cost saving can be received. This paper contributes to prove the cost effectiveness of using photovoltaic solar systems with the example from Australian residential dwellings. [ABSTRACT FROM AUTHOR]

Rapid urbanization and rising living standards in China have significantly increased building energy consumption, creating environmental pressures that necessitate the implementation of effective long-term energy-saving policies and plans. High-quality energy assessment plays a crucial role in developing these strategies. However, accurately assessing energy consumption on a national scale can be challenging due to the complex nature of energy systems and numerous potential influencing factors. This study aims to explore the internal interaction mechanism among energy-related factors from a macro perspective to improve the accuracy of energy consumption assessment. A national-level Integrated Dynamic Energy Assessment (IDEA) model is developed to reveal the potential linear and non-linear relationships in the macro energy system through system dynamics and the least squares method, and meanwhile to quantify the life cycle energy consumption of urban residential buildings in China from 2000 to 2020 accordingly. Results show 1) the five energy-related subsystems (population, economy, building, energy, and environment) achieved significant growth at least twice. 2) there are strong connections among them, as evidenced by multivariate linear and non-linear regression equations; 3) life cycle energy consumption of buildings has increased significantly over the last 20 years from 192.86 M tce to 1131.07 M tee, and the largest contributor is operational energy (45%), followed by embodied energy (33%) and mobile energy (22%) in 2020. 4) The discrepancies in end-uses of the operational energy indicate marked changes in occupants' energy-use behaviours in recent years. This study provides not only a more precise interactive system for evaluating national-level energy consumption, but also detailed life cycle energy consumption and internal interconnection relationships that can assist China's energy policymaking and serve as a reference for other nations. [ABSTRACT FROM AUTHOR]