Feasibility and Challenges of Adopting Solar Energy for Nearly Zero Energy Buildings: Lessons from Taiwan

Promoting and developing Zero Energy Buildings (ZEB) is crucial to achieving the goal of net-zero emissions. Zero Energy Buildings emphasize not only on buildings’ energy efficiency, but also on the transition of buildings’ energy consumption from nonrenewable energy to renewable energy. However, practically, since it is often impossible to achieve the “Zero” energy consumption in a strict sense, the concept of ZEB is implemented as Nearly Zero Energy Buildings (NZEB). Although adopting solar energy to achieve the goal of NZEB is currently one of the most feasible strategies, under what conditions the use solar energy for NZEB is technically feasible and how the building owners are motivated to invest in NZEB are still vague and challenging. As the solar power technology continues to advance and the environmental morality continues to rise in countries and societies, this study takes Taiwan as a case to study how feasible technically and behaviorally the NZEB is and what could be the main challenges.

Through extensive literature review and expert interviews, we analyze and establish the standards for defining the NZEB in Taiwan. Then we categorize the building types and residential energy consumption scenarios in Taiwan and investigate different approaches to installing solar photovoltaic systems. In sum, the two main approaches to installing solar photovoltaic systems are the roof floor installation and the roof trellis installation. The types of buildings to be studied are the terrace houses, the five-story apartments, and the eight-story apartments. To simulate the net energy consumption, firstly, Ladybug Tools is used to simulate the annual power generation of each solar photovoltaic installation in different climatic regions in Taiwan. Secondly, the formula for calculating the photovoltaic power generation is proposed according to the simulation results. Lastly, we analyze whether each installation approach can meet the specifications of NZEB under different energy consumption scenarios and evaluate, accordingly, the technical feasibility of achieving the goal of NZEB.

Based on the simulation, the roof trellis type is shown to generate the most power under the same construction area and to be the most feasible solar photovoltaic installation approach for the residential buildings to achieve NZEB.

We also analyze the economic feasibility of different NZEB scenarios using NPV and IRR methods. It is shown that, except for the eight-story apartments in the northern Taiwan’s climatic region, the simulated NZEB scenarios are economically feasible. Among them, the NPVs of the roof trellis type are lower than other schemes, the investment costs are expected to be recovered in about 13 to 17 years, and the IRR is about 5 to 7% for terrace houses and five-story apartments. To conclude, based on the current/modern solar photovoltaic technologies, NZEB can be well achieved for the residential buildings if the housing owners choose to invest.

Finally, whether the NZEB can be achieved depends on the house owners’ willingness to invest in NZEB, the main challenges of NZEB in Taiwan. We shall develop a consumer behavior model and form policy insights concerning NZEB.

Acknowledgment: Grant number 111-2124-M-002-006 and Grant number 110-2221-E-002-060