Cities, which consist of assembly of different districts, are responsible for 60%-80% of global energy consumption and greenhouse gas emissions. In 2003, the World Bank estimated that the energy consumption of cities would quadruple before 2050 compared to the current situation due to the increasing population. Many studies focus on reducing the energy consumptions of individual buildings. Many renewable and energy saving technologies can be used and are investigated at that scale. A district is a combination of different types of buildings. However, the energy performance and load profiles may vary from a ‘single building’ scale to an urban scale. There exists a gap in the research on the energy performance between the single building scale and the urban scale. Energy performance, control strategies and management may change when our focus moves from a single building scale to a district.
This research focuses on the energy performance and GHG emission patterns in green neighborhoods. There are mainly four objectives of this research.
- Identify the similarities and differences related to energy performance and GHG emissions when comparing the individual building scale to the district scale.
- Elaborate a sustainability evaluation system of the energy-related aspects at the district level.
- Choosing different energy strategies which are most suitable for the current system.
- Develop a multi-objective optimization strategy and a decision-making methods to improve sustainability of energy solutions at the district level.
There are many studies in the energy performance and GHG emission pattern at the individual building scale. Models and tools used for accounting of the energy and emission flows in the individual buildings may be adapted to the urban scale considering the similarities between the building scale and the urban scale. Data from the simulation results of some previous projects like green building simulations, green building energy system audits or optimization results can be used in this research. Urban metabolism, energy planning and some accounting tools will be used in this part.
It is difficult to judge whether a district is sustainable because the sustainability includes many aspects. Indicators such as non- renewable energy consumption, GHG emissions and life-cycle costs can be used to evaluate the sustainability. At the same time, we cannot forget that thermal comfort and energy supply reliability should be ensured. The evaluation system should consider all these aspects. Many programs like LEED ND are now used to certify the sustainability of a district. What this project focuses on is the items related to energy. So this project will investigate the existing certification programs at the urban scale, relist the indicators and quantify them.
The objective 3 is about energy strategies. In this part, the project will choose some energy strategies like rooftop PV systems, wind turbine systems, DR strategies or some else. The project will analyze the current and future profiles of their energy efficiency, GHG emissions, limitations, working conditions, installation and maintenance costs.
After having established the evaluation system and providing some energy strategies, we can get the direction for choosing different energy strategies. The choosing procedure is a multi-objective optimization. According to the indicators shown in the evaluation system, we will pick up the objectives for optimization. It should be remembered that we cannot choose all the indicators in the evaluation system because that 1) some indicators cannot be quantified; 2) the calculation will take too much time if we consider too much indicators. The design variables may vary according to the energy strategies chosen. Simulations like CFD, energy performance or prediction will also be used.
Potential applications and industrial benefits
When building a new so-called sustainable district, people always ask the question that whether the energy performance is as good as the builder says. The complexity of judging the sustainability of the urban system makes the questions hard to answer. This project may provide a proper way to answer the question.
On the other hand, when building a new district or replanning an existed district, for the decision makers, it will always challengeable to choose among different energy technologies because each technology has its advantages and disadvantages. The optimization platform will give the decision makers a tool to make the most suitable and sustainable decisions.