On 24 November, the fifth Solar Heat Switzerland (Solarwärme Schweiz) conference organised by the solar industry association Swissolar, the building services association suissetec and the Federal Office of Energy was held in Lucerne, Switzerland. As 2017 funding for solar heat incentives remains in doubt in several cantons and the priorities of the country´s energy policy haven’t been announced yet, the market outlook for solar thermal has not been very encouraging. But there seems to be a ray of hope in the form of low-temperature collectors for borehole regeneration and solar district heating. Click here to download the German-language presentations from the conference.
Seasonal storage is a key component in the transformation of today’s energy industry. Besides storing energy in summer for heating in winter, it can also be used to save waste heat from the industry and to increase the electricity production from biomass CHP plants. Experiences gathered with the technology during case studies were summarised as part of the study Seasonal thermal energy storage – Report on state of the art and necessary further R+D, which was published by Task 45, Large Scale Solar Heating and Cooling Systems, of the IEA SHC programme. Together with the Guidelines for Materials & Construction on the two most common storage types, borehole (see the chart) and water pit, it provides a good overview of the current advancements in this field (all three documents attached). Additional research into the design of seasonal storage will be carried out in follow-up Task 55, Towards the Integration of Large SHC Systems into District Heating and Cooling (DHC) Network. Interested stakeholders have been invited to join the kick-off meeting of Task 55 in Graz, Austria, between 19 and 21 October (see contact details below).
“Large-scale solar thermal systems in the GW range – an insignificant niche market or the future for solar thermal?” was the official title of a panel discussion at the Gleisdorf Solar conference in Austria in early May. The most important question was: What will be next for the planned 350 MWth solar district heating system called Big Solar in the Austrian city of Graz? “The challenge was to adapt the Danish district heating solutions to Austrian conditions,” emphasised the project’s initiator, Christian Holter (right), Managing Director of S.O.L.I.D. Meanwhile, Christian Stadler (left), Managing Director of one of Arcon-Sunmark’s subsidiaries, Arcon-Sunmark Germany & Austria, represented the company that has stated his own interest in realising Big Solar.
Tanks with high storage capacity and reduced losses are key to an increased solar heat share in households. Austrian research institute AEE INTEC has recently inaugurated a pilot research facility which promises exactly that: greater storage capacity than water and almost zero energy losses even in seasonal mode. The heart of the test facility are two low-pressure vessels filled with 750 kg of zeolite beads or spheres each. “Our first measurements since the beginning of October were very promising,” confirms Wim van Helden, head of the research project at AEE INTEC. “We reached a storage density of 180 kWh/m³, which has never been achieved before in a device of this size.” The research is part of an EU-funded project called COMTES – Combined Development of Compact Thermal Energy Storage Technologies and was co-financed by the Austrian Climate and Energy Fund. Theresia Vogel (second from left), Managing Director of said fund, joined the official starting ceremony on 11 November 2015.
In their position paper published in August 2015, the scientists of IEA SHC Task 42 (Compact Thermal Energy Storage) summed up the key results of their work between 2009 and 2015. Operating agent Matthias Rommel sees huge potential for latent heat and sorption materials in the long run – in seasonal solar heat storage for small and medium applications, as well as in the building sector. So-called smart grids will also require more heat storage units when devices such as heat pumps and co-generation plants are based on electricity grid requirements. Rommel views the definition of measurement standards for PCM materials as one of the task’s big achievements, which will help in material development. Furthermore, a research group from German research institute ZAE Bayern has performed a first cost estimate of compact heat storage technologies.
German company Consolar offers a heating system called SOLAERA, which combines a heat pump with a specially designed solar collector and a heat storage space using the latent heat released when water freezes to ice (see photo). The solar heat pump system with 18 m² of collector area, a 300 litre ice storage space and a 1,000 litre buffer tank provides enough energy to heat a well-insulated building in Germany. In a field test by a local environment group, Lokale Agenda 21, it achieved a Seasonal Performance Factor (SPF) of 5.6, putting performance even above prior simulations. The SPF describes the ratio of delivered heat to electricity consumed over the entire year. Consolar sold about 160 solar heat pump systems in total, mostly in Germany but also in Denmark, the UK, Switzerland, Belgium, France and Italy. The systems there achieved SPFs between 3.5 and 6, depending on collector field size, maximum flow temperature and heat demand.
IEA-SHC Task 42, entitled Compact Thermal Energy Storage, has entered into its final year and will end in December 2015. In February 2015, 44 scientists met for the 13th Experts Task Meeting in Vienna, Austria, to discuss the characterisation and development of materials for latent heat storage systems. This included phase change materials (PCM) like paraffin and thermo-chemical materials (TCM), such as sodium hydroxide solutions or zeolites. During the three-day meeting, the task members also visited the cogeneration plant Simmering in Vienna. The photo shows them in front of two pressurised water tanks with a total volume of 11,000 m3. The tanks are charged and discharged with 145 GWh annually and are operated to decouple heat energy production from demand in the district heating network of Vienna.
The Ramakrishna Mission Student’s Home in the city of Chennai, the capital of Tamil Nadu state on India’s southeast coast, is a combined residential high school and polytechnic college. It caters for around 700 orphan and poor students by providing free education, food and accommodation each year. The kitchen, which is supplied by Liquefied Petroleum Gas (LPG), has witnessed a sudden increase in costs because reductions in subsidies have led to rising energy prices. Hence, the mission’s management decided on a solar concentrating system in order to reduce LPG demand for cooking. The dish concentrator was installed three months ago.
Construction has begun on another large-scale installation: This time, the new number one solar thermal plant in the world will be in Vojens, a small town in southern Denmark, near the city of Kolding. The customer is Vojens District, which signed a contract with Danish collector manufacturer Arcon Solar this May about delivering and installing a 37 MWth collector field (52,491 m²). The 4,166 collectors will all be produced in Arcon´s factory in Aalborg. At present, the seasonal pit heat storage with 203,000 m³ is underway: Vojens District is uploading pictures once a month and the ones from August show the lining of the huge water-filled basin with high-density polyethylene foil (see photo). The currently largest solar thermal plant, a 26 MWth installation with 61,700 m³ of seasonal storage, is located in the Danish town of Dronninglund.