SOLAR HEATING PLANTS & LONG TERM HEAT STORAGE KEY-NOTE PAPER

Transcription

1 SOLAR HEATING PLANTS & LONG TERM HEAT STORAGE KEY-NOTE PAPER Per Alex Sørensen PlanEnergi, Jyllandsgade 1, DK-9620 Skørping, Denmark Phone: , Fax , Abstract - In the beginning of the 1990es solar heating plants with a maximum of up to 10 coverage of the total consumption had investment prices of 0,62-1,27 (price level 1995). In the project of Large Scale Solar Heating (1996) a series of suggestions for new solar heating plants demonstrated that the price might be reduced considerably. Since then some of these plants have become reality, showing investment prices between 0,60-0,90 for plants with a maximum of 18 coverage. New plants are appearing which show prices in the range from 0,46-0,70 (price level 2000) for plants covering a maximum of 50. So we see that a considerable fall in prices has occurred during the last ten years, provided the comparison is made among plants with the same solar fraction. There are hopes for further price reduction. A marketing breakthrough is yet to come, because so far there are no larger marketing areas in which solar heating can compete without being subsidised. Solar heating plants placed with oil heated block heating centrals in Austria and Germany, however, are very close. The same goes for solar heating plants placed with biomass heated district heating plants in Denmark. 1. INTRODUCTION In 1996 the APAS project of "Large-Scale Solar Heating" was developed for large solar plants and heat storages. In the project status was made concerning the development up to then in six European countries (Greece, Italy, Germany, Holland, Sweden and Denmark). At the same time a series of design studies was carried out for new plants, whose construction was planned for the last part of the '90es. The plants were compared with regard to the cost-benefit ratio (investment in ECU/yearly produced kwh). Since then, a number of the designed plants have been constructed. In this presentation an estimate will be made to whether the constructed plants have lead to the expected improvement of the cost-benefit ratio. Secondly the cost-benefit ratio for the most promising upcoming solar plants for the next 5 year period and the possibilities for the large scale implementation of large solar heating plants and seasonal heat storages will be assessed on that background. 2. LARGE-SCALE SOLAR HEATING In the project of Large-scale Solar Heating the plant types were divided into 1. systems with short-term storage (CSHPDS = central solar heating plant with diurnal storage) which cover app. 50 of annual demand for DHW or of the total demand. 2. and systems with long term storage (CSHPSS = central solar heating plant with seasonal storage). The cost-benefit ratio for the evaluated systems was the following for plants constructed in : Tab. 1. Systems with short term storage (CSHPDS), , Price level Ry, 89 (DK) Falkenberg, (S) Andersvænge, (DK) (DHW) Ravensburg, I, (D) Ravensburg, II, 93 (D) 137,

2 Tab. 2. Systems with long term storage (CSHPSS), Price level 1995 Lykovrissi, (GR)) Särö, 89 (S) PROMISING PLANTS CONSTRUCTED DURING THE PERIOD FROM Through the last part of the '90es, work has been continued with promising concepts for improvement of the cost-benefit ratio for large solar heating plants. In Sweden the most promising action in the period mentioned has been development of a solar collector constructed as roof modules. The modules were developed in co-operation with a firm specialised in supply of roof elements. The concept has been tested in Onsala. Fig. 2. Solar collectors on the roof of multi-family buildings. Neckarsulm. In Holland small individual solar collectors have been constructed as drain-back systems for some years. Now the drain-back technique is used in large plants, too. The latest example is the Brandaris project, where 760 solar collectors have been placed on the roof of an apartment block. The project was carried out in connection with a renovation of the building. Fig roof module collectors in Onsala. Photo: Jochen Dahm. In Germany a series of solar heat plants in connection with block heating centrals have been constructed. The plants have short time storage and the solar collectors are normally integrated in the roofs. Furthermore, in Germany, five solar heat plants have been built with long term heat storage. The storage types have been for example concrete tanks with inside steel lining, (Friedrichshaven) and a bore hole storage (Neckarsulm). Fig solar collectors in Brandaris. Drain-back system. Copyright Hans Pattist/Novem. Like Germany, Austria mainly uses roof integrated systems. The most promising project during the period mentioned has been solar heat collectors combined with biomass heated district heating. The largest of these plants is Eibiswald, which has been running since The size of that plant has made it possible to cut the construction costs by half compared with 200 plants.

3 Tab 3. Systems with short term storage (CSHPDS), Fig roof-integrated collectors in Eibiswald. In Denmark the major development has taken place within large solar heating plants for district heating. Marstal District Heating is the largest example up till now (8038 constructed in 1996 and later expanded to 9043 in 1999). The solar collectors are placed on the ground, (normally on farm land). The solar collectors produce times the amount of kwh compared to energy crops per area unit. The latest example is that of Ærøskøbing District Heating, also in the island of Ærø solar collectors and 1100 m 3 storage (steel tank) covers 16 of the yearly demand for district heating. Supply fuels are straw (70) and oil. Onsala, 96 (S) Brandaris, ) 266? 3.46 (NL) Eibiswald, (AT) Marstal, 96 (DK) Ærøskøbing, 98 (DK) ) The solar collectors constitute only 15 of the costs. 4. UPCOMING PLANTS Follow-up plants are coming up in connection with the most promising plants from the period. In Kungälv, Sweden, a ground mounted solar heating plant of is being constructed. This plant halves the cost-benefit ratio in comparison with the latest district heating plant constructed in Sweden, Falkenberg (1989). The solar collectors of the plant have non-reflecting glass and a new and more effective and more environmentally friendly selective coating. In Germany the system in Neckarsulm will be extended to 6300 of solar collectors and a m 3 duct storage. Fig solar collectors at and around Ærøskøbing District Heating. The economic picture for solar collectors constructed looks like this: The Austrian assessment is that a plant similar to that of Eibiswald would cost 25 less. Likewise, price reductions are on their way in Denmark. The present Danish projects, however, employ larger percentage of coverage with unchanged investments instead of cheaper heating. Thus, in Nordby in Samsø, (the official Danish RE island) a wood chip heated district heat plant has been designed using 25 solar heat coverage. At Marstal District Heat an extension has been planned including new solar collectors in order for the coverage to increase up to 30 of the district heat production. The construction of a pit heat storage of m 3 is expected in connection with the Marstal plant. Finally St. Rise, also in the island of Ærø, has planned the construction of a wood pellet heated heating central with 4000 solar collectors and 4000 m 3 storage (steel tank), in

4 order to obtain a 50 solar heat coverage of the district heat production. Hereafter the picture looks like this in the beginning of the new millennium: Tab. 4. Systems production MWh Kungälv (S) Neckarsulm (D) Austria (Like Eibiswald) Nordby (DK) Marstal (DK) St. Rise (DK) In table 5 the difference between solar heating plants with short term storage and solar heat plants with long term storage is less obvious and the prices for a high percentage of solar heat coverage have been drastically reduced compared to the previous period. Furthermore the investment costs may be reduced for the extra heating plant when the storage volume reaches 50. That advantage has not been accounted for in the above table. The most feasible Danish solution at present will be a m2 plant with a solar fraction of 15. The cost benefit ratio will be 0,50. Price reductions of are expected within the next 5 years. 5. WHERE IS THE FENCE LOWEST A Danish saying warns you against jumping the fence where it is lowest. But what if it is impossible to cross that fence any other place? Then it might be wise to cross exactly where it is lowest. Suppose the European solar industry needs places where the fence may be crossed - markets that is, where solar heat plants are profitable with no subsidies - in order for the production to grow seriously. In order to get a feeling of where the fence is lowest, I shall compare the costs of solar heat with heat produced by oil or biomass (interest rate 6,20 year loans, which will result in an annuity of ). Tab. 5. Comparison of solar and fuel prices Country Type of plant Price for solar heat EUR/MWh Alternative fuel Oil Biomass Austria District heating/block heating Sweden District heating ,5 Denmark District heating biomass, 15 coverage Denmark District heating 30 coverage The price for heat produced in an oil heated boiler in Germany is EUR/MWh and from a gas heated boiler the price is EUR/MWh. 6. CONCLUSIONS Among the countries investigated it may be concluded that production prices in Austria and Denmark either are or will be so low for heat coming from district heating centrals and block heating centrals with solar heat that unsubsidised solar heating will be competitive with heat produced with oil. The Danish situation, however, is that district heating is produced as combined heat and power (CHP) or produced with biomass. Thus, the competing fuel for district heating plants is not oil. Therefore a further fall of for solar heat must be encountered before unsubsidised solar heat can compete with the existing district heat production. In Austria the oil heated block heat centrals will be able to establish solar heat provided the estimated price reduction of 25 becomes reality. Therefore, admitted, there is no large market for the solar heat manufacturers to go into without plant subsidies. However, a further price reduction of would open for markets in district heating centrals in Denmark and block heating centrals in Germany. Within a five year period a price reduction of 20 should be within reach, provided a sufficient number of projects is launched to create a high rate of stable sale for the existing manufacturers. For the solar collectors a 10 improvement of the efficiency is also realistic. Thus I foresee good possibilities for a breakthrough for large solar heating plants within the next 5 years.

5 ACKNOWLEDGEMENT Jan-Olof Dalenbäck, (Chalmer University of Technology), Boris Mahler (Steinbeis-Transferzentrum, Stuttgart), Helmut Seiwald (ITW, Universität Stuttgart), Peter Nuiten (w/e consultants), Alexander Thür (Arbeitsgemeinschaft ERNEUBARE ENERGIE) and Wolfgang Streicher (Graz University of Technology) have contributed to this paper. REFERENCES Dahm J (1999) Small District Heating Systemet, Doctorate thesis, Document D48:1999, Dept. of Building Services Engineering, Chalmers University of Technology, Göteborg, Sweden. Dalenbäck, J.O. (1996) Evaluation of Existing s, EU-APAS-project "Large Scale Solar Heating Systems", Steinbeis Transfer-Zentrum, Stuttgart, Germany. Guigas, M., Fisch, M.N. (1996) Integration of Large-Scale Solar Heating Systems, EU- APS-projekt "large Scale Solar Heating Systems", Steinbeis Transfer-Zentrum, Stuttgart, Germany. Marstal Fjernvarme (2000) Måleprogram for solvarmeanlæg hos Marstal Fjernvarme (Monitoring Program for Solar Heating at Marstal District Heating), Marstal, Denmark (in Danish). NOTES AMSTERDAM WORKSHOP (1999) European Large-Scale Solar Heating Network. CIT Energy Management, Göteborg, Sweden.