Evaluation of buildings’ suitability as thermal energy storage in a district heating system
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Sustainable energy systems (MPSES), MSc
Publicerad
2013
Författare
Elebo, Joi
Petersson, David
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
When there are peaks in the power demand for district heating, back-up boiler plants using fossil fuels are often used in order to satisfy the demand. These plants are less efficient and less environmental friendly than base load plants. In an effort to reduce the need for back-up boilers, a share of the buildings in the network could be used as thermal energy storage. By moving the time of their heat deliveries peaks could be avoided, resulting in a more even load supplied by base load plants. The question is to what extent buildings are suitable of withstanding adjustments in heat delivery. This thesis examines the possibilities of using buildings as thermal energy storage, by analysing measurements performed by Göteborg Energi in several buildings in 2010-2011. During these measurements tests were carried out in which the input signal from the outdoor temperature, which controls the heat supply to the radiators, was adjusted. Test cycles were designed in order to alternate between periods of charge and discharge of heat and carried out at different times of the day to avoid variations caused by the users and weather. This resulted in a pattern of eight cycles per week. Test buildings are evaluated by the following parameters: how the indoor temperature (measured in two apartments per building) and heat supply change during test cycles; the size of these variations compared to natural variations; for how long the heat deliveries can be reduced and how different outdoor temperatures affect building behaviour. Initial results showed that the indoor temperature was rather stable during regular heating, but alternated according to the test cycles when they were used. During testing, temperature changes during the discharge period were less than 1°C and often less than 0.5°C. Some differences between the buildings could be found, but since there were such variations between apartments within the buildings, not all of them were certain. Larger change of the control signal in the test often showed larger temperature variation, but not entirely proportional. The temperature change may have been impacted by variations in outdoor temperature, but the variations between different results may also have different causes. The temperature variations caused by the tests were found to be in the same level of magnitude as the natural variations in the apartments. That indicated a possible decrease in power of about 10 W/m2 for a normal-to-discharge test period and 17-21 W/m2 for a charge-to-discharge test period.
Beskrivning
Ämne/nyckelord
Building Futures , Energi , Samhällsbyggnadsteknik , Building Futures , Energy , Civil Engineering