Urban Simulators to Study Energy and Urban Heat Island Implications

Buildings consume 40% of total US primary energy and 72% of electricity, a large fraction of which is used for heating, ventilation and air conditioning (HVAC). Higher urban temperatures caused by the urban heat island (UHI) effect increase the building cooling load. Quantification of UHI causes and effects in urban areas can improve the existing building stock and planning for energy efficient communities.

While there have been significant advances in energy modeling of individual buildings, reviews of the literature highlight the need for improved understanding of how the interaction between buildings and their surroundings modifies the energy savings obtained through green engineering measures. TUF3D (Temperatures of Urban Facets in 3-D) is a model that simulates urban temperatures and associated heat fluxes for neighborhoods with different arrangements of unventilated buildings without windows. On the other hand the ASHRAE toolkit (a stand-alone building energy model) takes into account indoor heat sources, material properties and composition of the building envelope (e.g. windows, insulation), and HVAC equipment to simulate energy needs. However, the ASHRAE toolkit does not capture the interaction between buildings, and between a building and the urban weather.

The ASHRAE toolkit was coupled to TUF3D to create a realistic building-to-atmosphere urban simulator. In an application, effects of urban surface materials such as irrigated grass, artificial turf, concrete, and asphalt on building and community energy use were examined. Heat gain or loss due to conduction into the building, leakage or ventilation of indoor air, and shortwave transmission through windows were the primary sources of building cooling load.