Rainer Becker, Dr.-Ing. Christof Wittwer

Fraunhofer Institute for Solar Energy Systems
Heidenhofstr. 2, 79110 Freiburg, Germany
Tel.: +49 (0) 761 / 45 88-54 09, Fax: +49 (0) 761 /45 88-94 09
rainer. becker@ise. fraunhofer. de, http://www. ise. fraunhofer. de

Within this paper the potentialities of using networked embedded systems will be discussed. New embedded hardware with network connectivity allows remote administration and software updates of solar thermal system controllers via internet. System self analysis helps to minimize breakdown times by sending email and SMS to request maintenance staff.

Basic Hardware and Software

Small computers with network capability (embedded systems) allow to get software updates via network, which is used to control and to monitor the behaviour of the components of a solar thermal system. The open source operating system Linux is a good choice for such purposes. Internet functionality is part of the system, it runs very stable and no license fees have to be paid. Today many consumer products are driven by Linux and so prices for ready-to-run embedded systems or processor boards decrease very fast. Ethernet is used for networking. It is standard and there is a non-proprietary protocol. It is cheap, reliable and there are gateways to many other network technologies. Network infrastructure needed for monitoring, visualisation and data acquisition (Fig. 1) is often already available or can be obtained cheaply.

Embcddcd-Linux-Compuier 1

Webportal. Service Provider. Data lagging

Embedded-!.inux-Computer 2

Monitoring Client

Internet

tome PC

Fig. 1: Network infrastructure for visualisation and monitoring purposes

Two embedded systems are running successfully in the Solarthermie2000 solar thermal system at the student hostel Vauban, Freiburg. The system has been updated with two compact units during the ConCheck project (Fig. 2, Fig 3, [1],[2],[3]), which are controlled by the embedded systems.

Control

Conventional controller hardware cannot easily be provided with software updates. In contrast to this controllers, software of embedded systems can be updated via Internet. Using simulation software (e. g. ColSim [4]) control algorithms are improved at Fraunhofer ISE in an iterative process. The embedded system can communicate with other components of the heating system (e. g. gas burner, apartment operating unit, …) by using its network connectivity. For example the pump for loading the storage of the solar thermal system at the student hostel Vauban, Freiburg, is controlled by Mbus communication. Control strategies can be optimised by using solar irradiation prognoses and current data from the Internet. The data can also be used for energy gain calculations to check whether the system works properly or not.