In the metropolises, it is unlikely to use merely solar and wind energy to pursue zero carbon building design. However, it would become possible if biofuel-driven trigeneration systems (BDTS) are adopted. It is thus essential to assess the application opportunity of BDTS in a holistic way. In this study, BDTS offered definite primary energy saving of up to 15% and carbon emissions reduction of at least 86% in different types of non-residential buildings as compared to the conventional systems. With 24/7 operation for the hotel and hospital buildings, the corresponding BDTS could even achieve zero carbon emissions. All the BDTS primed with compression-ignition internal combustion engine were not economically viable even in running cost due to the high local biodiesel price level. The BDTS primed with spark-ignition engine and fueled by biogas, however, would have economic merit when carbon price was considered for the conventional systems that fully utilize fossil fuels. Adoption of carbon tax and social cost could have the payback ceilings of 8 years and 2 years respectively for most of building types. Consequently, the results could reflect the application potential of BDTS for non-residential buildings, leading the pathway to carbon neutrality for sustainable sub-tropical cities.

The precise building performance assessment of residential housings in subtropical regions is usually more difficult than that for the commercial premises due to the much more complicated behavior of the occupants with regard to the change in indoor temperature. The conventional use of a fixed schedule for window opening, clothing insulation and cooling equipment operation cannot reflect the real situation when the occupants respond to the change in thermal comfort, thus affecting the appropriateness of the assessment results. To rectify the situation, a new modeling strategy in which the modification of the various operation schedules was based on the calculated thermal comfort (TC), was developed in this study. With this new TC-based strategy, the realistic building performances under different cooling provision scenarios applied to a high-rise residential building under the near extreme weather conditions were investigated and compared. It was found that sole provision of ventilation fans could not meet the zone thermal comfort by over 68% of the time, and air-conditioning was essential. The optimal use of ventilation fans for cooling could only help reduce the total cooling energy demand by less than 12% at best which could only be realistically evaluated by adopting the present strategy. Parametric studies were conducted which revealed that some design factors could offer opportunities for reducing the total cooling energy under the near extreme weather conditions.

Trigeneration is a strategic deployment to achieve the energy saving target in response to climate change mitigation. Appropriate choice of prime movers is paramount to make trigeneration feasible. It is common for trigeneration to be considered in district-wide application; however, there is little study on the effectiveness of various available prime movers in building-scale use. As such, diesel engine (DE), gas engine (GE), gas turbine with recuperator, and combined gas turbine cycle (CGTC) were involved as prime mover options for trigeneration in this study. Through year-round dynamic simulation, the energy and environmental performances of different trigeneration systems were thoroughly evaluated for a high-rise hotel building in subtropical climate. It was found that the DE-primed trigeneration would have the highest primary energy saving, while the CGTC-primed trigeneration would be the largest in carbon emissions cut. However, the GE-primed trigeneration system was deemed to be the best choice with both energy merit and system simplicity. It was also found that the part-load performance of prime mover and the required fuel type were closely associated to the annual energy and environmental performances.