Modelling of ammonia emissions from naturally ventilated livestock buildings: Part 2, air change modelling

This review shows the theoretical background for development of lumped ventilationmodels that can be integrated into models that aim to aid either design or operation of low emission naturally-ventilated buildings. The strength of lumped parameter modelling methods is that they have the potential to include effects of varying outdoor climate conditions, varying heat production from animals and the building design, which allow estimation of ventilation rate and indoor air temperature and humidity, with acceptable calculation times. With regard to design of low emission buildings, significant challenges still exist in reflecting the spatial distribution of ammonia emission surfaces and the influence of air velocity above these surfaces. In relation to operation of natural ventilation systems, it is obvious that lumped parameter methods have the potential to aid automatic control systems that aim to optimise the adjustment of automatically controlled openings for natural ventilation in a way that prevents over-ventilation and, thereby, minimises ammonia emission, without compromising indoor aerial conditions. It is also foreseen that lumped parameter methods have the potential to optimise opening adjustment and exhaust strategies in hybrid ventilation systems. In these contexts, ventilation is can be combined with a partial pit exhaust ventilation system which makes it possible to collect a significant fraction of the entire ammonia emission in a limited air stream. This may make it affordable to utilise air cleaning technologies in conjunction with naturally ventilated animal buildings.