The sun is an inexhaustible source of energy. Direct solar energy can be used for a variety of purposes, which are explained on the basis of a variety of measures.
Passive solar energy
With this technique, the built environment is given shape in such a manner that the design is based on the need for sun or shade. Examples include buildings in which large glass surfaces facing south can capture energy but which also create shade, minimising the need for air conditioning. In public spaces, too, taking the sun into consideration is becoming more and more important in connection with heat stress caused by the higher temperatures in summer. The Place de la Republique in Paris, discussed elsewhere in this publication, is an example of a public space designed with this in mind.
The advantage that PV panels offer is that they can be placed at decentralised locations, on roofs and walls. The drawbacks, however, are that their performance depends on the intensity of the insolation and the panels’ orientation and that the technology is currently relatively expensive. Prices have been dropping in recent years, though Siemer (2009) gives rates of €2600/kW-€3500/kW Erhorn-Kluttig et al., 2011.
PV panels come in different models. The performance and yield differ from one type to the next but are determined in all cases by the effective insolation. The effective insolation is based on orientation, angle and the presence of any obstructions.
Thermal solar collectors
These collectors are used for heating water. The hot water is stored and can be used for heating and preparing hot tap water and for heating the space.
Tests in practice Erhorn-Kluttig et al., 2011 show that thermal solar energy systems have been developed as far as possible. They work well and cost between €3,700 and €5,680. These prices include storage and a control system for a comprehensive package that covers approximately 60% of the heat required by a four-person household. Erhorn-Kluttig et al., 2011
Asphalt collectors involve a series of pipes built into a tarmac road, through which water runs that is heated by the sun. The lower yield compared with solar collectors is offset by the larger surface area. The need to transport the heat means that this system is limited to tarmac roads in towns and cities. An added benefit is that these collectors cool the roads during the summer, extending the useful life of the tarmac. In some countries, for example Switzerland, some of the heat captured with this system is used to keep the roads free of snow and ice in winter. Weijers et al., 2007
- Erhorn-Kluttig H., Jank R., Schrempf L., Dütz A., Rumpel F., Schrade J., Erhorn H., Beier C., Sager C. & Schmidt D.; Energetische Quartiersplanung – Methoden – Technologien – Praxisbeispiele; Fraunhofer IRB Verlag, Stuttgart, 2011
- Weijers E.P., Groot G.J. de; Energiewinning uit weginfrastructuur; ECN, 2007