Optimal operation of energy storage in buildings - Use of hot water systems
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The purpose of this study is to maximize the potential which lies in domestic hot water heaters. Today the temperature function in the hot water tank is constant throughout the day and the hot water demand is met by an electrical heater. Implementing a temperature which has the freedom to change in the tank, the energy demand can be met by both the energy stored in the hot water and the electrical heater. This means that if the electricity is expensive and the load on the mains are high, the hot water heater can shift load the electrical consumption from this time period to another by benefiting from the energy storage. This should result in a cost reduction since the consumption of electricity is moved to a time period with cheaper electricity. In addition, the consumption from the consumers can be altered if the electrical storage is properly used. The main challenges with hot water tanks are the unpredictability of future demands and time varying electricity prices. The consumer is free to benefit from desired amounts of hot water at any time of day. In addition, the future electricity prices are unknown. Despite these uncertainties the hot water tank should always be able to deliver sufficient and hot enough water. To optimize the hot water heater in a proposed optimal strategy was implemented for minimizing the electrical cost of heating water. The optimal operation was compared to other simple policies to see if they were better, worse or equally good strategies. From the result in the report the proposed strategy reduced the cost compared to all suggested policies. The highest savings were compared to having a constant temperature in the hot water tank. The electrical consumption was also proven to change if the policies were provided with the opportunity of benefiting from the energy stored in the water compared to only having electrical heating. This implies that one solution to shave the peak demands in the electricity is by utilising the energy stored in the hot water.