DEARSUN: when thermal solar covers the building heat demand

Even in the sunniest regions of Europe, current solar heating systems for houses are not yet able to cover their overall heat demand all year round, based only on solar energy..  However, a new concept patented by Enersun, a very small company in the Var Department of France, seemed very unlikely to succeed at first.  It was difficult for a young company with a handful of employees to finance a research action requiring several hundred thousand Euros and that might need several years of work.  But Enersun has been able to benefit from a mechanism set up by the European Commission to support this type of initiative and has developed a new concept of solar heating system, able to supply the full year thermal load (space heating plus domestic hot water production) of a building without, to a large extend, any auxiliary heat source. The DEARSUN project labelled by the Capenergies competitiveness cluster started in October 2008.  The project partnership includes Honeywell, the world leader in automation and control solutions, and also several small and medium sized companies and research bodies.  CSTB forms the core of the group and is coordinator for this program that is planned for completion in September 2010.

Solar heating: on the path towards energy autonomy

Heating as conceived by Enersun is based on the principle of high temperature storage.  In other words, the objective is to use solar thermal energy to produce and store heat at temperatures of up to 150°C.  To achieve this objective, solar collectors withstanding this temperature and a heat transfer fluid with a boiling point greater than the maximum temperature reached in the installation were selected.  Then,  DEARSUN partners developed specific components capable of resisting these temperatures (tanks, etc.) and elaborated a control system which permanently optimizes the productions and the uses of the heat transfer fluid according to the user’s needs.  Dominique Caccavelli tells us “The first numerical simulations have already been performed on residential buildings.  The first observations show that autonomy levels of the order of 80 to 85% have already been achieved in Mediterranean areas, instead of the 30 to 40% normally observed with existing solutions."  This performance is close to full autonomy and also has the advantage that it avoids investments in auxiliary heating equipment.  A simple electrical resistance mounted in the tank is enough to complement energy when necessary!  "Although the system appears particularly relevant in sunny regions, the increasing number of low energy consumption buildings (with lower heating demand) makes the extension of the concept towards northern latitudes cost efficient, and accelerates progress towards energy independence."

Summer heat for winter

Research carried out for the DEARSUN project shows that heat stored over a cycle of several weeks can be generated and distributed in the context of a Mediterranean climate.  A special study will deal with the application of high temperature solar heating to schools, and will include a study on the feasibility of energy transfers between seasons.  Thus, calories (and energy) stored during the summer could be redistributed during the winter to satisfy a significant proportion of heating needs.