German private health services provider MediClin, which runs 30 hospitals throughout its home country, estimates it will reduce by at least £11,300 a year the heating bills at the first of the facilities to be fitted with an energy management system based on wireless sensors which shut off radiators when windows are opened.
MediClin opted, consequently, for wireless sensor technology from Germany’s EnOcean. The selected system sees an EnOcean STM 250 window contact wirelessly connected to an Oventrop DynaTemp 100/16 router, in turn wired to each radiator valve so it automatically closes if the window is left open. The STM 250 is a solar-powered, “maintenance-free” magnetic contact wireless module, with an energy accumulator that enables it to operate for several days in complete darkness.
It monitors the presence of the magnet attached to its side, immediately signalling any change of status. EnOcean can now also offer window handles incorporating similar modules that draw their energy from the handle being turned, in turn controlling the radiator valve according to window position. At the first, Müritz clinic, one wireless receiver was centrally positioned to create the optimum connection to the 16 rooms initially fitted with the technology.
Installers used a wireless test set to determine the correct positioning of window contacts and receivers, with wireless repeaters added to ensure propagation over longer stretches or where obstacles like concrete walls were present. The hardware was linked to the clinic’s LAN network for central control. Finally, each window contact was linked to the adjoining radiator valve, with each sensor assigned its own 32 bit ID.
A subsequent full-scale comparison of two heating “sub-routes”, one with, and one without, the window contacts, demonstrated savings of some 800 kWh per room/annum, equating, MediClin says, to 100 litres of heating oil, £53 or 270 kg CO2. Across the 200 rooms at Müritz in which the system now features, EnOcean says the clinic should see overall annual savings of some £11,300, with anticipated ROI in under three years.
