Smart energy for smart buildings
By using kinetic, solar or thermal energy for switches, energy can be saved in buildings
Building energy insights
- The internet of things is finding its way into houses and apartments, office buildings, airports and hospitals.
- Radio-based lighting, heating and security systems as well as new types of services provide more comfort, more efficient and better building services and lower energy consumption.
- The energy supply for the sensors usually comes from batteries, which is not optimal for several reasons. Energy harvesting offers an attractive alternative.
- Learn how to use energy harvesting for powering systems within buildings.
- Review the three concepts of how energy harvesting sensors use power, and the benefit to building owners.
- Understand how to lower energy consumption.
The success of battery-powered wireless sensors and controllers is no coincidence, as they offer several advantages. Because they are independent of cables and sockets, they can be placed anywhere and moved flexibly between rooms.
But their energy is not available endlessly. If the battery is empty, private users need to change it right away and will need to always have backup batteries. For larger systems, facility managers must plan and carry out the procurement and replacement of batteries. Here — as in industrial applications — it is certainly a challenge to monitor the large number of batteries and replace them as a preventive measure or immediately if necessary.
Another aspect is environmental pollution: it is estimated that tens of trillions of internet of things radio sensors will be in operation in a few years. The same number of batteries requires 1 million tons of lithium — that’s the equivalent of 10 years of production. But even if the available lithium were sufficient, its depletion would cause considerable environmental pollution. And so far, there is no recycling process that can extract enough pure lithium to be reused in batteries. The same applies to other toxic heavy metals in batteries, such as mercury, lead, cadmium and nickel.
An alternative to batteries is the power supply via cable. However, especially in the case of retrofits and expansions, this means a lot of effort and high costs. Simple and just as flexible as battery-operated wireless sensors and controls, on the other hand, are those that use energy harvesting to generate their energy directly from the environment — from movement, light or temperature differences. This means that sensors and switches can operate maintenance-free, are self-powered and can be installed anywhere in the building.
Energy from movement
With kinetic energy harvesting, electricity is generated from kinetic energy. For example, pressing a switch can activate an electromechanical energy converter that generates enough energy from the press of a button to switch appliances or lights on and off, or to call up light scenes or control roller shutters.
This principle can be used to create switches that do not need to look different from conventional models — from simple on/off or up/down switches to sliding and rotary controls for controlling light intensity and color, heating or security systems. They are always ready for immediate use and anyone in the building can use them. This makes them easier to use than an app that has to be opened and activated on a smartphone or tablet.
The same method is also suitable for window contact sensors, which report when a window is open. Additionally, a water sensor uses a swellable material, which — when it expands — activates the electromechanical energy converter.
Energy from light
To generate energy from sunlight, small solar cells mounted on sensor modules convert the light into electrical energy. This enables sensors to be operated, e.g., for humidity, temperature, window contacts or presence sensors. The energy is stored internally, which ensures that the sensor’s energy supply is secured for up to four days, even without a new energy supply.
Energy from temperature
With a Peltier element and a DC/DC converter, energy can be generated from a temperature difference of just 2°C, which is sufficient to operate a wireless sensor. This method is ideal, for example, for self-powered heating valves that use the temperature difference between the heater and the environment to change the setting and communicate via radio with a solar-powered room controller.
Efficient building management
Such energy harvesting based wireless sensors fulfil typical tasks of building automation entirely maintenance-free and self-powered, such as status messages of doors and windows. In office blocks or public buildings such as railway stations or airports, they enable maintenance and repair work on lifts, heating and air conditioning systems or any other technical equipment to be carried out as required and thus more efficiently. For this purpose, they send certain status messages via an IoT gateway over the internet to the relevant service provider.
The use of a building can also be optimized in this way: presence and activity sensors can record how often a meeting room is used and by how many people. The same applies to sanitary facilities, so that they can be cleaned as required and consumables such as toilet paper, soap and towels can be refilled. This reduces effort and costs while at the same time increases user satisfaction. The facility manager in turn can be sure that the agreed services have been provided. Networked with IoT platforms from companies such as Microsoft, T-Systems and IBM, the sensors provide real-time data for the digitization of buildings and building services.