دانلود رایگان مقاله انگلیسی یک کنترل کننده سیستم تهویه بر اساس مدل های کاهش فشار و CO2 - الزویر 2018

abstract

In ventilation systems a considerable amount of energy is used for mass transport of conditioned air to provide the requested volume flows. Reducing volume flow while maintaining indoor air quality has leverage on energy efficiency and is commonly known as Demand Controlled Ventilation (DCV). Current implementations require Variable Air Volume (VAV) controllers to provide a defined volume flow to each room. The controllers measure the pressure difference and adjust the motor flap accordingly. This paper examines an approach that achieves DCV, but replaces the VAV-boxes with simple motor flaps. The missing pressure-drop measurements that allow calculating the volume flow are substituted by a model of the ventilation system. The authors develop a method for calculating the pressure drop in the ducts of a ventilation system that regards the topology and the components of the duct system. This model is coupled with a model for the CO2 concentration in the rooms for all conditioned rooms in order to derive the required air volume flow. Using this model, a linear controller is developed that operates the ventilation system. It is shown that the presented approach operates the ventilation more efficiently, while maintaining comfort constraints and saving installation costs. The modeling effort of the current approach is expected to be reduced with the introduction of the Building Information Model (BIM) into building operation.

7. Conclusion and outlook

The work presented in this paper is driven by the idea of replacing hardware and investment costs with advanced algorithms that can be implemented in software. A dynamic pressure drop model for the duct ventilation system and its components was developed together with a controller that increases energy efficiency by coupling supply pressure and room volume flows more tightly. The controller is capable of operating either VAV boxes or motor flaps, it only requires the additional flap characteristics, which have been identified using operation data.

With regard to cost savings an estimate has been made for a reference office building: the building was built in 2015 according to passive house standard, has optimized daylight usage as well as concrete core activation with a gross floor area of 3100 m2. The ventilation system uses a total of 100 VAV boxes of different sizes from size DN100 to the largest being 500 × 200 mm. Common market prices indicate investment cost saving from VAV controller to motor flap of 55%, which results in a total investment cost saving of about 11,000 EUR; other costs for operation and maintenance remain approximately the same. This defines the margin how much the additional controller software may cost per building; addition-ally the presented controller improves energy efficiency by another 5%, which can be significant, seeing that the ventilation system is one of the main energy consumers in a building.