Energy Impacts

All meteorological simulations were conducted with a focus on summertime impacts of mitigation strategies. As a result, the analysis of winter-time impacts of mitigation strategies on energy (heating demand) are likely to be inaccurate. Specifically, we anticipate that MIST overestimates the wintertime air temperature reductions associated with mitigation strategies. The result is a corresponding overestimate of the winter-time heating penalty associated with mitigation strategies. Hence, this assumption leads to a conservative estimate of the annualized energy savings.

The energy models themselves were obtained from an analysis conducted by Lawrence Berkeley National Laboratory (LBNL): "Streamlined Energy-Savings Calculations for Heat-Island Reduction Strategies -Draft Final Report", by Hashem Akbari and Steven Konopacki, Heat Island Group, March 2003.

For each city in their analysis specific building prototypes were modeled using the DoE-2 building energy analysis software. Because building codes and insulation levels have evolved in time LBNL presents results for both "pre-1980" and "post-1980" buildings". By modifying both the building envelope definition and the "typical meteorological year" weather data LBNL was able to simulate both the direct and the indirect effects of increasing building albedo and vegetative cover. By combining results from meteorological simulations and building energy simulations LBNL developed estimates of how a particular mitigation strategy would impact energy consumption and peak power for Residential, Office, and Retail space on a per 1000 sq. ft roof area basis.

The LBNL modeling focused on buildings in a small set of cities. To apply these results across a wider range of cities they conducted classification analyses to relate energy impacts to CDD and HDD. They defined 11 CDD groups and 15 HDD groups to represent the impacts across different climates. Thus, the energy impacts can be estimated using either the CDD similarity or the HDD similarity approach. MIST uses results from these approaches to place bounds on the projected energy impacts.

 

Advanced users seeking more detailed information on this and other topics related to the scientific and modeling underpinnings of the MIST software tool should read the detailed model description document that can be downloaded from the MIST website.