Energy Efficiency through Thermal Energy Storage - Evaluation of the Possibilities for the Swedish Building Stock, Phase 1

As a first step in assessing the potential of thermal energy storage in Swedish buildings, the current situation of the Swedish building stock and different storage methods are discussed in this paper. Overall, many buildings are from the 1960’s or earlier having a relatively high energy demand, creating opportunities for large energy savings. The major means of heating are electricity for detached houses and district heating for multi dwelling houses and premises. Cooling needs are relatively low but steadily increasing, emphasizing the need to consider energy storage for both heat and cold. The thermal mass of a building is important for passive storage of thermal energy but this has not been considered much when constructing buildings in Sweden. Instead, common ways of storing thermal energy in Swedish buildings today is in water storage tanks or in the ground using boreholes, while latent thermal energy storage is still very uncommon.

Bättre utnyttjande av nya och befintliga förrådslokaler på SSAB Tunnplåt

The purpose of this assignment at SSAB Tunnplåt in Borlänge was mainly to investigate and describe the circumstances for the spare parts stored in storage facilities within the area of operation. Even new facilities which could serve as storage rooms and their opportunities for storing spare parts were an important part of the investigation. This because of the need for improved storing of spare parts. Furthermore, market offers where reviewed for storage of spare parts in more tailored designs. The work will culminate in proposals for improvement which is of importance for the development surrounding the storage and handling of spare parts. This is since the design and management of existing storage facilities is not perceived as satisfactory with regards to spare parts characteristics. Moreover, the amount of stock locations is too few in relation to the actual need. The approach used to achieve objectives of the work was an advanced mapping for collection of vital data. The mapping consisted of interviews with involved parties, both internal and external, for the most comprehensive picture of the problems as possible. In addition, a literature survey was conducted to identify possible options for the objectives of the work as well as a personal study of existing and new storage facilities. Furthermore, the market offers for improved conditions in storage rooms were examined. A clear picture of internal logistics and warehouse activities for spare parts at SSAB Tunnplåt has been obtained during this work. From this picture, it is concluded that work in and around storage facilities can be made more efficient. SSAB Tunnplåt should additionally make efforts in the storage facilities for better use of the available storage space. A number of proposals for improvement for each studied storage facility and spare parts management in general have been conducted. These proposals for improvement include presentations to improve the design of the studied storage facilities towards enabling more stock locations. The proposals also include additional equipment for handling spare parts, scrap handling, as well as expansions of the maintenance system which supports activities in the spare parts management.

Identifiering av parametrar till ackumulatortanken Solus1050 från consolar - en metodbeskrivning

This report describes the work done creating a computer model of a kombi tank from Consolar. The model was created with Presim/Trnsys and Fittrn and DF were used to identify the parameters. Measurements were carried out and were used to identify the values of the parameters in the model. The identifications were first done for every circuit separately. After that, all parameters are normally identified together using all the measurements. Finally the model should be compared with other measurements, preferable realistic ones. The two last steps have not yet been carried out, because of problems finding a good model for the domestic hot water circuit.The model of the domestic hot water circuit give relatively good results for low flows at 5 l/min, but is not good for higher flows. In the report suggestions for improving the model are given. However, there was not enough time to test this within the project as much time was spent trying to solve problems with the model crashing. Suggestions for improving the model for the domestic circuit are given in chapter 4.4. The improved equations that are to be used in the improved model are given by equation 4.18, 4.19 and 4.22.Also for the boiler circuit and the solar circuit there are improvements that can be done. The model presented here has a few shortcomings, but with some extra work, an improved model can be created. In the attachment (Bilaga 1) is a description of the used model and all the identified parameters.A qualitative assessment of the store was also performed based on the measurements and the modelling carried out. The following summary of this can be given: Hot Water PreparationThe principle for controlling the flow on the primary side seems to work well in order to achieve good stratification. Temperatures in the bottom of the store after a short use of hot water, at a coldwater temperature of 12°C, was around 28-30°C. This was almost independent of the temperature in the store and the DHW-flow.The measured UA-values of the heat exchangers are not very reliable, but indicates that the heat transfer rates are much better than for the Conus 500, and in the same range as for other stores tested at SERC.The function of the mixing valve is not perfect (see diagram 4.3, where Tout1 is the outlet hot water temperature, and Tdhwo and Tdhw1 is the inlet temperature to the hot and cold side of the valve respectively). The outlet temperature varies a lot with different temperatures in the storage and is going down from 61°C to 47°C before the cold port is fully closed. This gives a problem to find a suitable temperature setting and gives also a risk that the auxiliary heating is increased instead of the set temperature of the valve, when the hot water temperature is to low.Collector circuitThe UA-value of the collector heat exchanger is much higher than the value for Conus 500, and in the same range as the heat exchangers in other stores tested at SERC.Boiler circuitThe valve in the boiler circuit is used to supply water from the boiler at two different heights, depending on the temperature of the water. At temperatures from the boiler above 58.2°C, all the water is injected to the upper inlet. At temperatures below 53.9°C all the water is injected to the lower inlet. At 56°C the water flow is equally divided between the two inlets. Detailed studies of the behaviour at the upper inlet shows that better accuracy of the model would have been achieved using three double ports in the model instead of two. The shape of the upper inlet makes turbulence, that could be modelled using two different inlets. Heat lossesThe heat losses per m3 are much smaller for the Solus 1050, than for the Conus 500 Storage. However, they are higher than those for some good stores tested at SERC. The pipes that are penetrating the insulation give air leakage and cold bridges, which could be a major part of the losses from the storage. The identified losses from the bottom of the storage are exceptionally high, but have less importance for the heat losses, due to the lower temperatures in the bottom. High losses from the bottom can be caused by air leakage through the insulation at the pipe connections of the storage.

Rapport från/Report from IEA Task-14 mötet/meeting on solar heating system, Hameln Tyskland/Germany August 1992

Participation as observer at the meeting of Task 14 of IEA's Solar Heating and Cooling Projects held in Hameln, Germany has led to greater understanding of interesting developments underway in several countries. This will be of use during the development of small scale systems suitable for Swedish conditions. A summary of the work carried out by the working groups within Task 14 is given, with emphasis on the Domestic Hot Water group. Experiences of low-flow systems from several countries are related, and the conclusion is drawn that the maximum theoretical possible increase in performance of 20% has not been achieved due to poor heat exchangers and poor stratification in the storage tanks. Positive developments in connecting tubes and pumps is noted. Further participation as observer in Task 14 meetings is desired, and is looked on favourably by the members of the group. Another conclusion is that SERC should carry on with work on Swedish storage tanks, with emphasis on better stratification and heat exchangers, and possible modelling of system components. Finally a German Do-it-Vourself kit is described and judged in comparison with prefabricated models and Swedish Do-it-Yourself kits.