Australian Solar Cooling Interest Group (ausscig) Conference

Transcription

1 D.M. Whaley, W.Y. Saman, A. Alemu, Barbara Hardy Institute, University of South Australia, Mawson Lakes, South Australia, Overview Introduction / Justification of research Solar thermal air conditioner prototype: Overview of system, System components. Preliminary Results: Moisture absorption, Cooling modes, Heating mode, Regenerator mode not in paper! Future Work: Evaluation of 12 month performance, Model validation. Conclusions 2

2 Introduction Air conditioning energy in residential sector increasing over last 2 decades. Average residential energy demand: Space heating & cooling: 41%, Domestic hot water: 30%. Residential buildings account for 20% Australia s GHG emissions: Space heating & cooling: 30-40% Number of houses and their size increasing Other Space heating / cooling Heating / cooling requirements increase, Peak electrical demand is escalating and adding to electricity costs. New housing trend: use RC AC Domestic hot water Monitored data shows 90% of summer peak demand linked to AC s. 3 What To Do? Use renewable / clean energy and low power appliances? Cooling not using vapour compression, e.g. evaporative Don t work in humid regions! Solar water heaters Well established technology, Numbers doubled between , now 7% of Australian homes, Oversized for Summer usage (cover Winter demand). Integrated approach? Combining these and other components, to provide: space and water heating, space cooling and dehumidification?? 4

3 System Overview HW tank Warm water Continuous gas booster Collector inlet water Regenerator Low conc. desiccant Hot water High conc. desiccant Warm air Dehumidified air Absorber Fresh air Direct Evap. Pad Continuous gas booster Return air Figure does not include: Water inlet and outlet of heat exchangers, Dampers, fans and pumps, Controller and other electronics, Gas supply. 5 System Components Solar water heater 5 * Flat plate collectors, 500L vented tank (2 HE coils). Absorber (HE) Regenerator (HE) Liquid desiccant Lithium Chloride Controller PCI-1710U, Feedback based on outside and indoor temperatures & relative humidity. 6

4 Absorber Indirect water and air to air heat exchanger, used for two modes: Direct and indirect cooling, Direct, indirect cooling and dehumidification. Water In (mist) High Conc. Desiccant Cooled + Dehumidified Air Outside Air Absorber Exhaust Air Low Conc. Desiccant Water Out Outside Air 7 Regenerator Indirect water to air heat exchanger, used for two modes: Heating, Regeneration (reconcentrate desiccant). Hot Water Out Low Conc. Desiccant Heated / Exhaust Air Regenerator High Conc. Desiccant Hot Water In Return / Outside Air 8

5 Test Arrangement 9 Preliminary Test Results: Test rig inside an open shed, Mawson Lakes Campus Dry Adelaide heat! Absorber modes: Moisture absorption, Cooling Mode. Direct and indirect cooling, Direct, indirect cooling and dehumidification. Regenerator modes: Heating, Regeneration. 10

6 Moisture Absorption Moisture absorption capacity Function of desiccant concentration, temperature and flow rate Equilibrium film air moisture (g/kg) If outside air has less 12 Moisture than the 10 equilibrium moisture... 8 Absorber acts as an Evaporator! Results for 2 Adelaide summer day conditions: Inlet Temp. ( C) Inlet Specific Humidity (g/kg) Outlet Temp. ( C) Desiccant temperature ( o C) Outlet Specific Humidity (g/kg) 11 Cooling Modes Direct + Indirect Cooling: Outside Air dry bulb temp. ( C) Outside air wet bulb temp. ( C) Indirect evaporator outlet air ( C) Direct evaporator outlet air temp. ( C) Direct evaporator saturation efficiency (%) Indirect evaporator effectiveness Direct and Indirect Cooling + Dehumidification (limited data): Temperature ( o C) Outside Dry Bulb Outside Wet Bulb Absorber Outlet Direct Evap Outlet 16:34 16:35 16:36 16:37 16:38 16:39 Local time 16:40 16:41 16:42 16:43 12

7 Heating Design for 60 C air temperature Test conditions: Ambient air temperature = 19.5 C, Hot water flow rate = 328L/h, Flow rate tripled at 13:30. Temperature ( C) Regen HW In Regen HW Out Regen AIR In Regen AIR Out 09:00 09:30 10:00 10:30 11:00 11:30 12:00 12:30 13:00 Local time 13:30 14:00 14:30 15:00 15:30 16:00 13 Regenerator (not in paper!) Tested over 4 days, where: Ambient air: C, Specific humidity: g/kg Maintain desiccant inlet concentration and flow rate, Vary hot water temperature. 41 End concentration (%) y = x R² = AVG HW in & ou t T ( C) 14

8 Summary & Conclusions Summary: Overview of a combined approach for solar water heating, space heating, cooling and dehumidification, Preliminary test results, for various modes. Conclusions: System can cool air to below wet bulb temp, using ordinary evaporative cooling, when used with indirect cooler and dehumidifier, Air moisture absorption and desiccant concentrating (regeneration) dependent on desiccant initial concentration and temperature. 15 Future Work Install prototype in Adelaide House for 12 month trial: Northern suburbs house: 4 bedroom, 168m 2, Automatic operating mode and zones. Evaluate performance for 12 month period. Compare to TRNSYS models developed. Test absorber to humid conditions e.g. specific humidity of 18+ g/kg Adjust controller Allow user controllability Zones, Control mode, 16

9 TRNSYS Model 17 Thank you Acknowledgement: The Department for Manufacturing, Innovation, Trade, Resources and Energy (Renewables SA) Barbara Hardy Institute members: Academic and professional staff, Technical (workshop) staff, Interns, and local and international students. Questions?