1. Novel Design of a Portable Heat Energy Storage Device Adopting a Phase Change Material for CHP and Solar Energy Applications K. TRAPANI BSc. Renewable Energy Final Year Dissertation Project Supervisor: Dr. Dean Millar

2. INTRODUCTION Concept: Extraction of waste heat from an automotive micro- CHP engine using a portable thermal storage device (Millar & Huang, 2009) Specific design of the portable thermal energy storage adopting phase change materials (PCMs)

3. Compact Light Modular Stackable High thermal energy storage Efficient heat transfer REQUIREMENTS OF THE DEVICE PORTABILITY FLEXIBLE THERMAL CAPACITY MAXIMISED PERFORMANCE

4. DEVICE DESIGN Modular unit: Mass = 15kg Dimensions = 20cm x 35cm x 18cm Model unit (1/5 th scale): Mass = 3kg Dimensions = 12cm x 35cm x 6cm ComponentMaterial PCMParaffin wax PipingCopper FinsAluminium Internal caseSteel InsulationReflective foam External casePlastic SOLIDWORKS DESIGN OF A 1/5 th SCALE MODEL

5. PCMs – materials which exhibit a phase change (from one state to another) PHASE CHANGE MATERIALS (PCMs) Enthalpy of System TEMPERATURE ENTHALPY SOLID LIQUID GAS PHASE CHANGE

6. PHASE TRANSITIONS SELECTION OF DEVICES PCM SOLID-LIQUID SOLID-SOLID SOLID-GAS GAS-LIQUID SOLID-LIQUID ORGANICSINORGANICS Not corrosive Low or no undercooling Chemically and thermally ostable Greater phase change oenthalpy Paraffin Wax Relatively high heat of fusion Stable heating and cooling cycle Economical and abundant

7. PROPERTIES OF THE DEVICES PCM WhereQ = Pt Governing equations: Q = mcϴ Q = mL Sensible heating Latent heating

8. SIMULATION Simulation software had to be modelled to account for the phase change material. Assumptions: Paraffin wax is homogenous and isotropic Heat is transferred only by conduction Simulation is time dependent Hence the paraffin waxs thermal properties had to be designed as a series of sensible heating stages. C s = 3412J/kgK for T<328K C sl = 98587J/kgK for 328K<T<330K C l = 4466J/kgK for T>330K Boundary conditions: Mass flow rate of heat transfer medium 0.108kg/s at 333.2K Fluid outlet subject to normal environmental conditions (293.2K and 101325Pa) Initial conditions: Same as normal environmental conditions Results (for a model scale device): Thermal heat capacity – 381.7kJ

9. TESTING OF 1/5 th SCALE PROTOTYPE CHARGING of Device:DISCHARGING of Device: Heat supplied thermal store = 595.8kJ η = 64.1% Heat retrieved from thermal store = 247.0kJ η = 64.7% Overall efficiency = 41.5%

10. The device is primarily designed to be integrated with a central domestic heating system. DEVICE INTEGRATION

11. The main heat sources for the device are: Micro – CHP (automotive vehicle engines) Surplus solar thermal heat APPLICATIONS FOR THE DEVICE Micro-CHPSolar Requires a portable heat transfer medium Integration with an automotive vehicle Stationary application Integration with the domestic central heating system Two primary heat sources: Exhaust gas Engine cooling process Yu, C., & Chau, K.T. (2009) Review on thermal energy storage with phase change. Renewable and Sustainable Energy Reviews, 13, 318 – 345. Retrieved from duaemanus.blogspot.com

12. OVERVIEW OF A MICRO-CHP INTEGRATED DEVICE Increase mass implies: a larger CAPEX greater operating costs enhanced revenue Scenarios Displacement of gas heating Displacement of electricity heating

13. Main application for device is in micro-CHP Economically device is currently not very feasible for displacing the heating load from a gas boiler Optimisation of the design (improving PCM to total device mass ratio) Simulation testing for practical maximum efficiency Consequent optimisation of the practical model Further development of device fittings is crucial to the installation of the device CONCLUSION

14. THANK YOU ANY QUESTIONS?