||Feasibility of demand response by phase changing materials for cooling application
||Nielsen, Anders Østergaard
||Elmegaard, Brian (Thermal Energy Systems, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||Purpose: This report covers a feasibility study of electricity demand response for cooling applications by energy storage through phase changing materials. Three different solution proposals are investigated for
supermarket applications. Furthermore the effect on energy composition in terms of wind energy percentages and production during off peak hours is investigated.
Method: Storage ability is achieved by three different technologies; ice bank, PCM embedded in display cases and ice slurry. The three different PCM storage solutions are modeled in EES. The saving potential is found by
comparing yearly running costs for the solution proposals against a reference system. The running costs are based on electricity prices for West Denmark in 2009, Danish energy taxes in 2010 and a Danish weather reference year. The optimal operation pattern is determined by a dynamic programming model. The dynamic programming model is implemented in Matlab. The model optimizes operation pattern based on both electricity price and operating conditions in terms of condensing temperature. The performance evaluation of the solution proposals are based primarily on their saving potential and the thereby given acceptable investment. Wind energy percentages are found for every hour of the year to determine the average wind percentages for the different solutions. The best performing solution proposal is tested under three different futuristic scenarios with regards to wind production and taxation.
Results and conclusions: It is found that the cooling plant COP is of great importance for the feasibility of a demand response solution. Conclusions on saving potential are based on assuming COP predictions of the solutions to be correct within 1%. The actual precision of the COP model is expected to be in the range of 15%. It is found possible to achieve savings on running costs through demand response. The savings are partly due to reductions in energy use and partly due to lower average electricity price. The PCM display case solution is found unable to reduce running costs. Both the ice bank solution and the
ice slurry solution are found capable of reducing energy costs. The ice bank solution results in the largest
annual saving (9,600 kr. or 5.2%). The savings are found insufficient to justify the price difference between the reference solution and the ice bank solution. The optimal storage size is found to be around 5 hours of max production for all the solution proposals. This storage level support storage throughout the day, but not from day to day. All the solutions increase the degree of wind energy used by the cooling system. The increase is highest for the ice bank solution (5.5%) and smallest for the ice slurry (4.1%). It is found that modifying the electricity
tax system can make the ice bank solution cost-efficient.
||DTU Mechanical Engineering : Kgs.Lyngby
Creation date: 2011-06-24
Update date: 2011-06-27