Abstract
Using passive methods in façade design for controlling heating and cooling needs is an important prerequisite for constructing cost-effective nearly zero-energy buildings. Optimal control of solar heat gains reduces the cooling demand and the size of the active cooling systems. However, applying such methods increases the impact of internal heat gains on the heat balance of the buildings, and accordingly also the dimensions of cooling systems. Therefore, a good model of internal heat gains is needed for a reliable and optimal sizing of the cooling sources. This paper aims to bring understanding to developing internal heat gains models for sizing the cooling systems. For this purpose, several weekly internal heat gain profiles were selected from a large set of tenant-based electricity use measured in 4 office buildings in Tallinn. The selection was based on maximum daily or weekly peak loads of an office space per floor area. The selected profiles and the schedule of EN 16798-1 were used to dimension ideal coolers in the zones of a generic floor model with landscaped offices developed in IDA-ICE 4.8. The model had variable window sizes and thermal mass of the building materials. Finally, the internal heat gains models resulting in the largest cooling capacity were identified. We found that utilizing thermal mass can reduce the cooling system size by up to 7% on average and the models with big windows and light structure need the largest cooling systems. The cooling loads obtained with the profile of EN 16798-1 did not significantly differ from the average of other profiles’ results. This paper focused mainly on the zonal dimensioning of cooling systems, therefore a more in-depth analysis of the different occupancy patterns as well as developing models for dimensioning the cooling system at the building level, is needed.
Highlights
Zero or net-zero energy buildings are increasingly getting attention in recent years
The experimental data used in this study were aggregated from four office buildings located in Tallinn, Estonia, from early 2017 to March 2020 [19]
The analysis results are from simulations for a 4month period from the 1st of June to the end of September, by using the schedules and profiles described in the previous sections
Summary
Zero or net-zero energy buildings are increasingly getting attention in recent years. In order to reduce heat gains for efficient cooling design, some passive solutions can be used, e.g. controlling heat gain from the sun using shadings, applying natural ventilation, passive façade design, etc [2]. Implementing such methods will reduce the total cooling demand of the building while it increases the impact of internal heat gains on cooling system size [3]. In a warm climate for an old building without external wall insulations, Coşkun et al in [4] indicate a share of internal heat gains in total cooling load as low as around 1%, while the share of electricity use for equipment usage can be up to 60% of the total electricity use [4]. By reducing the internal heat gains from lighting (using efficient LED lights), equipment and small power consumers, majorly laptops and monitors in office buildings, a 60% reduction in cooling loads can be achieved in certain building systems [3]
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