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analysis of the influences of solar radiation and façade glazing ...

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1.2 Background <strong>and</strong> literature review 17<br />

used in both sensitivity studies <strong>of</strong> dynamic systems <strong>and</strong> in building optimization problems<br />

with a large number <strong>of</strong> combination tests.<br />

Building structures <strong>and</strong> environments are modeled by a system <strong>of</strong> differential algebraic<br />

equations. Required smoothness assumptions that can be applied in <strong>the</strong> solution <strong>of</strong> <strong>the</strong>se<br />

types <strong>of</strong> equation sets have been proposed by Wetter (Wetter, 2005). A new multi-zone<br />

building energy simulation program called BuildOpt, which differs from o<strong>the</strong>r s<strong>of</strong>tware<br />

because <strong>of</strong> <strong>the</strong> inclusion <strong>of</strong> various smoothing algorithms, was presented. The numerical<br />

experiments indicated a reduction in <strong>the</strong> computation time <strong>and</strong> a high precision <strong>of</strong><br />

smoothing techniques proposed by <strong>the</strong> author.<br />

Multi-objective genetic algorithm (MOGA) was used by Wright (Wright, et al., 2002) to<br />

estimate <strong>the</strong> optimum pay-<strong>of</strong>f characteristic between daily energy costs <strong>and</strong> <strong>the</strong> quality <strong>of</strong><br />

<strong>the</strong> <strong>the</strong>rmal environment in <strong>the</strong> building. An example <strong>of</strong> a single zone HVAC system<br />

composed <strong>of</strong> cooling <strong>and</strong> heating coils, a regenerative heat exchanger <strong>and</strong> a supply fan was<br />

used to show <strong>the</strong> benefits <strong>of</strong> <strong>the</strong> multi-criterion optimization genetic algorithm. Estimates<br />

indicated that MOGA search methods can be successfully used in <strong>the</strong> <strong>the</strong>rmal design <strong>of</strong><br />

buildings in respect to occupant comfort.<br />

Genetic algorithms were used by Xu <strong>and</strong> Wang (Xu, et al., 2007) in <strong>the</strong> <strong>the</strong>rmal modelling<br />

<strong>of</strong> <strong>the</strong> building envelope. They developed a method to optimize <strong>the</strong> parameters <strong>of</strong> <strong>the</strong><br />

simplified dynamic model based on frequency domain regression. Validation <strong>of</strong> <strong>the</strong><br />

optimization method <strong>and</strong> its effectiveness were conducted by comparing <strong>the</strong> predictions<br />

with <strong>the</strong> results from <strong>the</strong> <strong>the</strong>oretical model. It was found that <strong>the</strong> frequency domain<br />

<strong>analysis</strong> greatly simplified <strong>the</strong> search for optimal parameters.<br />

Earth-contact heat transfers in built environments were investigated by Davies <strong>and</strong><br />

colleagues (Davies, et al., 2001). They improved <strong>the</strong> efficiency <strong>of</strong> <strong>the</strong> numerical technique<br />

by adopting some elements from <strong>the</strong> response factor method. The results <strong>of</strong> calculations<br />

based on <strong>the</strong> new model showed a dramatic decrease in <strong>the</strong> computing time <strong>of</strong> <strong>the</strong><br />

simulations compared to <strong>the</strong> traditional finite volume technique in keeping with accuracy<br />

<strong>and</strong> flexibility.<br />

The accuracy <strong>of</strong> <strong>the</strong> building energy simulations strongly depends on <strong>the</strong> estimate <strong>of</strong> <strong>solar</strong><br />

irradiance on external facades. Loutzenhiser, along with co-workers (Loutzenhiser, et al.,<br />

2007), validated short-wave <strong>radiation</strong> in <strong>solar</strong> gain models applied in energy simulation<br />

s<strong>of</strong>tware. In <strong>the</strong> experiment, a database <strong>of</strong> <strong>solar</strong> <strong>radiation</strong> from two 25-day measurements<br />

performed on <strong>the</strong> EMPA campus located in Duebendorf (Switzerl<strong>and</strong>) was used.<br />

Calculations were made using four building energy simulation programs: EnergyPlus,<br />

DOE-2.1e, ESP-r <strong>and</strong> TRNSYS-TUD <strong>and</strong> seven <strong>solar</strong> <strong>radiation</strong> models. Using <strong>the</strong> mean<br />

absolute differences method, it verified that <strong>the</strong> uncertainties <strong>of</strong> <strong>the</strong> models are as follows:<br />

14.9 % for <strong>the</strong> isotropic sky, 9.1 % for <strong>the</strong> Hay–Davies, 9.4 % for <strong>the</strong> Reindl, 7.6 % for <strong>the</strong><br />

Muneer, 13.2 % for <strong>the</strong> Klucher, 9.0 % for <strong>the</strong> modified Perez <strong>and</strong> 7.9 % for Perez.

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