Smart valve
Issue 01-2016:
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PM DM GmbH presents the Smart Valve® radiator valve, which runs without batteries and produces the electricity it needs with a thermoelectric generator (TEG). The Smart Valve® won the Energy Harvester Award in Berlin while still in the development stage.
Representation of the radiator valve (PM DM design)
The TEG consists of series-contacted thermocouples and two different electric conductors. The newly developed valve uses the difference in temperature between the radiator and the room to generate electrical energy (energy harvesting).
The temperature difference is at least 15 °C at inlet temperatures of more than 40 °C and room temperatures around 20 °C. The chiplike TEG thus generates a voltage of approximately 1 V. Compressible heat conducting foils prevent air pockets and thereby reduce thermal resistance. The heat sink has the greatest influence on the generated TEG voltage, which is why an ingenious thermal design was developed, based on many simulations. The gearset requires five to ten times less energy to adjust the valve, compared to conventional designs.
Maximum efficiency
The valve currently achieves energy efficiency well above 80%. An electric doublelayer capacitor with few losses due to intrinsic leaks is used as the energy store. It can also easily handle the low charge currents. Integrated output stages are used for the motor drivers, since they have leakage currents of less than 100 nA. An ultra lowpower microcontroller provides the system’s intelligence and controls the drive, positioning, communication and power management functions. It consumes less than 3 µW of power in sleep mode. It is woken up cyclically by a timer and can measure all necessary operating parameters.
Sleep and awake phases
The capacitive sensor also requires only a fraction of the energy of earlier systems. All unnecessary components are systematically disconnected from the power supply, for example during the summer, when the TEG does not supply any energy. The system automatically wakes up when the heating period begins in the fall. The valve supports all common energy-efficient protocols, such as Bluetooth Low Energy, ZigBee and EnOcean.
Simplified representation of a TEG through the Seebeck effect
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