Natural ventilation with heat recovery: a biomimetic concept

In temperate countries, heat recovery is often desirable through mechanical ventilation with heat recovery (MVHR). Drawbacks of MVHR include use of electric power and complex ducting, while alternative passive heat recovery systems in the form of roof or chimney-based solutions are limited to low rise buildings. This paper describes a biomimetic concept for natural ventilation with heat recovery (NVHR). The NVHR system mimics the process of water/mineral extraction from urine in the Loop of Henle (part of human kidney). Simulations on a facade-integrated Chamber successfully imitated the geometry and behaviour of the Loop of Henle (LoH). Using a space measuring 12 m2 in area and assuming two heat densities of 18.75 W/m2 (single occupancy) or 30 W/m2 (double occupancy), the maximum indoor temperatures achievable are up to 19.3 °C and 22.3 °C respectively. These come with mean relative ventilation rates of 0.92 air changes per hour (ACH) or 10.7 L·s−1 and 0.92 ACH (11.55 L·s−1), respectively, for the month of January. With active heating and single occupant, the LoH Chamber consumes between 65.7% and 72.1% of the annual heating energy required by a similar naturally ventilated space without heat recovery. The LoH Chamber could operate as stand-alone indoor cabinet, benefitting refurbishment of buildings and evading constraints of complicated ducting, external aesthetic or building age.