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Supermarket refrigeration consumes substantial amounts of energy. However due to the thermal capacity of the refrigerated goods, parts of the cooling capacity delivered can be shifted in time without deteriorating the food quality. In this paper we introduce a novel economic-optimizing MPC scheme that reduces operating costs by utilizing the thermal storage capabilities. In the study we specifically address advantages coming from daily variations in outdoor temperature and electricity prices but other aspects such as peak load reduction are also considered. An important contribution of this paper is also the formulation of a new cost function for our proposed power management system. This means the refrigeration system is enabled to contribute with ancillary services to the balancing power market. Since significant amounts of regulating power are needed for a higher penetration of intermittent renewable energy sources such as wind turbines, this feature will be in high demand in a future intelligent power grid (Smart Grid). Our perspective is seen from the refrigeration system but, as we demonstrate, the involvement in the balancing market can be economically beneficial for the system itself, while delivering crucial services to the Smart Grid. We simulate the system using models validated against data from real supermarkets as well as weather data and spot and regulating power prices from the Nordic power market.