After a life-long career in designing air-conditioning systems, Ben Bronsema (78) has developed a zero-energy airco by using the building itself as a climate engine.
Bronsema is responsible for the inner climate of large buildings such as the new Schiphol terminal, the VROM tower in The Hague en the Mees Pierson office in Rotterdam. A mechanical engineer by training, the gap between architects and installation engineers always bothered him. After his working life, he aspired to bring these disciplines closer together. Now at the ripe age of 78, he is about to defend his PhD thesis Earth, Wind & Fire – natural airconditioning in which the building itself provides the energy for air treatment.
In Bronsema’s design, sun and wind provide the energy for the air circulation, and falling water moisturises or dries the air and heats or cools it. To achieve this, Bronsema developed three climate-controlling elements that work together: a climate cascade with falling water, a ventec roof that makes use of the wind to create suction and a solar chimney that converts solar radiation into an upward draft.
Three step system
Exploring the system top-down, the curved Ventec roof handles air intake on the windward side of the building, and expulsion of used air in the centre of the roof. This layout ensures there will be no shortcut contamination from exhaust to inlet. The curved roof makes use of the Venturi-effect. This means that passing winds will create an under pressure that will extract used air from the building. The 360 degrees intake uses wind pressure and a pressure room to power the airflow through the building. From this intake, the air flows into the climate cascade.
The Climate Cascade is a shaft where water of 13 degrees Celsius falls down, pulling the incoming air downwards. In the summer, the hot air will be cooled (from 28 to 19 degrees for example) and dried. The falling cold water will dry the air because excess humidity will condense on the cold-water droplets. In the winter, cold air will be warmed up in the climate cascade, typically from -10 to plus 6.5 degrees Celsius, after which it will be heated further by an auxiliary heating unit which uses heat from the underground heat storage or, if the sun shines, directly from the solar chimney.
After the air has served the living- or workspaces, the Solar Chimney, an architectural provision at the South side that harvests solar heat to create an upward draft, will draw it out. Besides powering the air suction, the solar chimney, or solar façade, also produces heat, which will be harvested by heat exchangers and stored in underground aquifers for use in the winter.
Reducing step by step
According to calculations for the refurbishment of a four-storey office building, the subsequent steps will reduce the climate system’s energy use, and even make the building energy producing. If the office uses 120 kWh/m2 per year, which is about standard, the Climate Cascade will reduce it to 101 kWh/m2. The solar chimney brings it further down to 85 kWh/m2, the heat and cold storage reduces the energy use to 54 kWh/m2 and a Ventec roof covered with photovoltaics will make the building energy-producing with a modest plus 5.6 kWh/m2.
Not bad, especially considering that Bronsema originally didn’t aim so much for energy reduction as for integrating architecture with interior climate control. He may achieve that as well with next year’s competition for master students in Architecture from Delft and Eindhoven. Their mission will be to revitalise existing office buildings according to Bronsema’s passive airconditioning system while exploring the variety in form.
Although Bronsema has developed his idea into ready-to-use calculation models, and he has demonstrated the functionality of scaled prototypes, the first full-scale application has yet to be built. Bronsema tells he is currently working with the large contractor BAM to locate a suitable office building that may be renovated along his principles of Earth, Wind and Fire, or rather, sun, wind and water.Ing. Benjamin Bronsema, Earth, Wind & Fire – Natuurlijke Airconditioning, 7 June 2013, PhD supervisor Prof. Peter Luscuere (Architecture).
Video: Bronsema explains the principles of his natural airconditioning – NewEnergy TV for De Vernufteling
Radio: Bronsema explains the principles of his natural airconditioning in Labyrinth radio, 12 May 2013
Self-sufficient cabin, Delta 3 March 2010
Klimaatcascade, De Ingenieur Maart 2011