© SAES Getters / Arup

Solar active louvres using shape-memory alloys

Actuators that tilt louvres in response to external conditions make it possible to protect a building from the sun during hot days and allow benefit from solar radiation on cold days. The actuators are usually hydraulic, pneumatic or motor-based systems and so require power to be operated. This research explores new ways to operate external louvres in façades without using energy or any electronic systems. Actuators fabricated with shape-memory alloys (SMA) have the potential to provide a lightweight, solid-state alternative.

The SMA ‘remembers’ its original, cold-forged shape and it returns to its pre-deformed shape when it is heated. The three main types of shape-memory alloys are: copper-zinc-aluminium-nickel alloy; copper-aluminium-nickel alloy; and nickel-titanium (NiTi) alloy.  In this work we used an NiTi alloy.

This project enabled us to produce an actuator prototype for tilting horizontal aluminium louvres.

Working with SAES Getters, our team investigated three possible solutions for the actuator and developed a prototype.

We found the most promising actuator solution to be a series of small springs stacked in several levels, rather than options which used a single spring or a wire.

An actuator with an SMA wire would require too much wire and be too complex.

The actuator works faster with several small springs than with one bigger spring.

A series of smaller springs uses less SMA material (NiTi alloy) than does one large spring.

Through this research, Arup developed innovative solar shading devices that can automatically adjust to external conditions without using energy or electronic systems.

Our findings can be used to improve building performance: shaded buildings need less energy for heating and cooling, and the temperature inside will be more stable as well.

This research also opens up other opportunities, as actuators made with SMAs have applications in industries including healthcare and aerospace.  Our findings can also be used to develop other cutting-edge SMA devices such as mass dampers, bearing supports and mechanical valves.

Today, a typical building façade has more glazing than ever as architects, developers and users want natural light and views to the outside. At the same time, regulations and certification programmes are setting more restrictive solar protection requirements to reduce energy consumption.   Actuated louvres offer a means of addressing these contradictory drivers.

Actuated louvres operated by shape-memory alloys are cost-effective, low-maintenance systems that help reduce building energy demand without themselves using any supplied energy in their operation.