The conference presentations will be visible on http://www.solar-district-heating.eu/Home.aspx in a few days.
The conference clearly showed that there are improvements during the last years on every part of the solar district heating systems. This includes especially reduction of the district heating temperatures, simplification of the overall systems, improved efficiency of solar collectors, reduction of price for solar collectors and especially large-scale storage systems. It is probably at the time to make an update of my old paper on 15 years going now to “25 years of experiences in large-scale solar heating”.
The Danish systems seem to be still leading and partly driving the developments. The presenter from the Danish District Heating Association, Birger Lauersen, did give his version, why this is the case. Basically it is due to the fact that district heating exist, that cooperative organisation of DH systems with for-non-profit economic model are the most important preconditions. High gas prices and low interest rates support, however also. I may add the first movers on the buyers, on the producers and the consultancy sides. However the findings from Denmark may not be valid in cities, which is also the case for Copenhagen, where solar must be produced on rooftops or in the outskirts. In Copenhagen this is certainly realistic due to the DH piping to a very large region around Copenhagen covering approx. 50 km diameter the resent years. There is enough space for solar between the cities. It will be interesting to see, if this happens. In the first term of energy transformation, bio energy seems to be the first choice. In the longer run, the demand for biomass for transport will probably set an end to this direction.
Example systems and projects where presented from all over Europe. Sweden seems to have stopped the developments, where Germany has its “Energiewende” that is driving developments. The southern countries are suffering from the economic crisis, even though the potentials are available.
An online tool for large scale solar heating with/without large storage by Solites, based on thousands of TRNSYS computations, was presented. The thousands of values from the computations are placed into a database and represented by multidimensional fit into approximations for lookup by the online tool – Hence no computations are “online” leading to fast results, but in the same time limits the number of combination of parameter, locations and system configurations. The tool is applicable for distributed and central systems. You find it at www.sdh-online.solites.de.
IP-Solar is an online monitoring system for distance control and monitoring of central solar systems with minimum sensors and configurations to keep costs down. Due to its web-appearance, the possibility of applying modern devices such as smart phones, tables etc. are at hand. The solution does provide failure diagnostics by approx. 160 predefined algorithms to ease surveillance of plants. Notification is supported. As an example, the overheating of the solar collectors would be notified as warning in a first temperature-range, advancing to a critical condition notification as the temperature rises. I feel that such tools will help the solar heating sector to spread. Supporting this cheap and simple support with a full-scale distance monitoring and support consultancy would give a full coverage of such services to new operators and hereby probably lead to further expansion.
Most important are the talks in the break giving insight into the actual projects, findings and issues at the different plants and by the different stakeholders. The new Marstal extension is one of the most important steps showing that the limit of size is not reached yet. The pit did again show price reduction due to size, now being approx. half of the price from the previous pit. It also shows new challenges with the new pit storage has a serious attach of corrosion on the inlet and outlet pipes, probably due to biological material that was carried into the pit under construction. This is new due to size and long construction period with an open pit. The answer is not found yet and the condition is very critical, a solution must be found to avoid similar situations.
Next solar district heating conference will take place in Germany in May 2014.
Posted by Fred Heller 
