Smart houses – energy savings and cost reductions with intelligent automation systems

Within the pilot on smart houses, the partners of the Green PE project have set up a demonstration system at a house in Växjö, Sweden. Integrated into everyday life in an ordinary private household, the pilot will demonstrate the advantages of power electronic (PE)-based solutions for the energy management in smart houses.

The new systems and infrastructure have been installed in addition to the standard equipment without interference and interruption of the power services. Installed on the roof, the demonstration pilot is using 20 photovoltaic (PV) panels with a rating power of 4.9 kW to generate DC power which can be used directly to run most of the electrical and electronic appliances in the house without any converter at all. This results in significant energy savings.
There are power feeds of AC 220 V and DC 350 V in the house:

  • all fixed lighting in the ceiling runs on DC
  • six wall sockets with DC 350 V are spread over the house (for TV, radio, chargers for e. g., computers and mobile phones)
  • DC/AC converter in case of a failure

In addition to increasing the energy efficiency, the use of a DC power system also allows a direct storage of the generated energy in connected batteries. Therefore, a system for energy storage in battery packs including AC/DC and DC/AC converters/inverters is installed together with a control and monitoring system.

In the diagram below, the local networks in the house are shown as one DC network and two separate AC networks where one of the AC local networks is fed only when the external AC grid is available. It also demonstrates how an external single phase AC power generator can be connected in case of longer term outage of grid feed.

Connection and monitoring of the different power subsystems © Rise Acreo AB

The next step for the Green PE partners participating in the pilot will be to test the complete system thoroughly and also to run some live tests where the AC grid feed is cut off and where the battery backup will be used for the continued household consumption. Furthermore, different test cases will be run at daytime as well as at nighttime and evaluated both from pure technical as well as from performance and usability aspects:

  • charging the battery
  • discharging the battery
  • optimising the use of DC in the house
  • minimising losses in converters
  • optimising safety
  • using the battery at power failure
  • saving energy and costs