Design and Performance of a Hybrid Ventilation System with Heat Recovery for Low Energy Buildings

A new hybrid ventilation system for low energy buildings has been investigated
theoretically using TRNSYS. The system is based on natural ventilation but utilizes
a fan during hours when the natural driving forces are not sufficient. Heat from the
exhaust air is recovered in an air-to-water heat exchanger. The heated water is
pumped to the incoming ventilation air where it is heat exchanged to preheat the
fresh air. Energy from solar collectors is used in combination with heat recovered
from the sewage system to heat the ventilation air and to preheat the cold water for
domestic use. Results from the TRNSYS simulations show that the bought annual
auxiliary energy need for the new hybrid ventilation system is lower than for a
conventional fan driven ventilation systems using air-to-air heat recovery units
combined with an identical solar collector and sewage heat recovery unit. Since the
new system is based on natural ventilation it is also more silent compared to
standard mechanical ventilation systems.