NET- ZERO ENERGY BUILDINGS Alan Fung, Getu Hailu, Raghad Kamel, Navid Ekrami, Peter Dash Ryerson University 20/05/2014 1
BIPV/T + ASHP - TECHNOLOGIES FOR NEAR INTRODUCTION AND Residential sector in Canada consumes energy mostly for space heating (63%) and domestic hot water (17%). Air source peat pump usage is constrained in Canada due to the reduction in performance in very cold conditions. In wintertime, ambient air temperature falls much below freezing. This performance can be further enhanced by having low grade thermal energy fed into the ASHP. The PV/T system collects energy at low temperature and may not work efficiently in direct heating. This energy could be used as a source to the heat pump in winter. The combined solar assisted heat-pump system appears to be a suitable alternative, which not only saves building space but also reduces the reliance on utilities electricity supply. 20/05/2014 2
OBJECTIVES Design and build a test hut facility at the Toronto & Region Conservation Authority (TRCA) Kortright Center. Select appropriate equipment such as ASHP using numerical simulations, thermal storage system (i.e., water tank, ventilated concrete slab, etc. Compare different BIPV/T designs. Develop optimal control strategies for BIPV/T systems. Evaluate the associated cost with the deployment of BIPV/T systems. Fig. 1 Schematic of a BIPV/T system 20/05/2014 3
BIPV/T + ASHP - TECHNOLOGIES FOR NEAR AND Modeling TRNSYS modeling of BIPV/T+ASHP Analytical modeling to evaluate design parameters that influence the production of electricity and recovery of thermal energy for BIPV/T system GHG emissions reduction that could be achieved by a roof integrated BIPV/T system at the TRCA s Kortright Centre Fig. 2 Archetype House at the Kortright Centre for Conservation 20/05/2014 4
BIPV/T+ASHP COP EVALUATION AND COMPARISON The COP of the ASHP was evaluated for three separate scenarios, By supplying the ambient air directly the ASHP, By coupling the ASHP to the wall integrated BIPV/T system only, By coupling the ASHP to the roof integrated BIPV/T system only. TRNSYS was used to evaluate the performance of an ASHP coupled with a BIPV/T system The Archetype Twin House A was used for evaluation. 20/05/2014 5
Temperature of Air Entering Heat Pump ( 0 C) BIPV/T + ASHP - TECHNOLOGIES FOR NEAR AND BIPV/T+ASHP COP EVALUATION AND COMPARISON 20 15 10 5 Roof BIPVT Wall BIPVT No PV 0-5 -10-15 -20-25 272 273 274 275 276 277 278 279 280 Time of Year (hours) Fig. 3 Temperature of the air entering the ASHP (left) and COP of the heat pump for the three different configurations (right). January 12. A fan with 750W power consumption was assumed to circulate air. 20/05/2014 6
BIPV/T + ASHP - TECHNOLOGIES FOR NEAR AND BIPV/T+ASHP COP EVALUATION AND COMPARISON 6 6 Wall BIPVT No PV Roof BIPVT No PV 5 5 4 COP COP 4 3 3 2 2 1 1 0 0 0 200 400 600 800 1000 1200 1400 Time of Year (hours) 1600 1800 2000 0 200 400 600 800 1000 1200 1400 Time of Year (hours) 1600 1800 2000 Fig. 4 COP of the heat pump when coupled with the roof integrated BIPV/T system (left) and with the wall integrated BIPV/T system (right) for the months of January 1 to March 31. A fan with 750W power consumption was assumed to circulate air. 20/05/2014 7
CFD Modeling Objective Develop correlations that facilitate the design of BIPV/T systems such as heat transfer coefficients Nusselt number correlations Validate results PV assembly Measured velocity and temp Insulation QradPV QradINS hwind Adiabatic Measured radiation hpv hins hinside Air flow No viscous stress, zero gauge pressure Qradamb Fig. 5 Schematic of the studied BIPV/T system. Q radam b: surface to ambient radiation, Qrad PV : surface to surface radiation (from PV), Qrad INS : surface to surface radiation (from INS), INS: Insulation. h PV : convective heat transfer coefficient on the PV side, h INS : convective heat transfer coefficient on the insulation side, h inside : natural convection 20/05/2014 8
Temperature ( o C) Temperature ( o C) BIPV/T + ASHP - TECHNOLOGIES FOR NEAR AND CFD Modeling - Results 50 45 50 45 40 40 35 35 30 30 25 20 15 10 5 0 Exp PV Temp Exp - INS Temp Exp - Air Temp SIM - Air Temp SIM - Ins Temp SIM - PV Temp 0 1 2 3 25 20 15 10 5 0 Exp - PV Temp Exp - Ins Temp Exp - Air Temp SIM - Air Temp SIM - INS Temp SIM - PV Temp 0 1 2 3 PV Length (m) PV Length (m) Fig. 6 Temperature profiles for 2 m/s (left) and 1.5m/s (right) inlet velocity. PV: PV s backside, INS: insulation. SIM: CFD simulation, Exp: Experimentally measured 20/05/2014 9
GHG Emission Analysis The cost saving and GHG emission reduction are directly related to onsite electricity generation from PV/T system. Hourly time dependent GHG emission factor due to total electricity generation mix for the Province of Ontario was used. The monthly GHG emission reduction due to saving in electricity demand by the heat pump when it was linked with the PV/T array. the annual GHG emission due to electricity demand by ASHP could be reduced by 225 kg CO 2. Fig. 7 Monthly GHG emission due to electricity consumed by ASHP 20/05/2014 10
Energy and Operating Cost Saving The heat pump electricity consumption was reduced by 20.2%, from 6421 kwh to 5114 kwh, when combining PV/T systems with air source heat pump. It was found that seasonal COP could be increased from 2.74 to a maximum value of 3.45. Fig. 8 ASHP daily electricity consumption for heating season with and without PV/T system 20/05/2014 11
Fig. 9 Daily thermal energy generated from 25 PV/T panels and the heating demand of the Archetype Sustainable House 20/05/2014 12
The electricity cost is reduced when the electricity consumed by the heat pump is decreased. Hourly electricity consumed by the ASHP and ASHP+PV/T systems was calculated based on Time-Of-Use (TOU) price for Toronto. The annual cost of electricity needed to operate the heat pump in the house was $1024.5. The use of PV/T system and air source heat pump for heating purposes resulted in direct reduction in the annual electricity cost to $837.8, resulting in $24 average monthly saving in electricity bill in winter season (October to May). Fig. 10 Monthly electricity cost for the ASHP working alone and combined with PV/T system 20/05/2014 13
GHG emission credit Fig. 11 The credit of using the electricity generated from the PV/T array instead of the electricity from the local grid 20/05/2014 14
BIPV/T Testing Facility Roof integrated BIPV/T Wall integrated BIPV/T CFD modeling of BIPV/T systems Thermal storage Concrete slab Gravel bed Radiant heating Phase change materials Fig. 12 BIPV/T test hut 20/05/2014 15
BIPV/T + ASHP - TECHNOLOGIES FOR NEAR AND A complete BIPV/T systems with VC ASHP and thermal storage is being designed Roof BIPV/T 25 PV panels approximately 2x1m on the south facing side Inclined 35 Tasks Determination of electricity and heat generation Evaluation of ASHP COP improvement CFD modeling Evaluation of GHG emission reduction Fig. 13 Roof integrated BIPV/T 20/05/2014 16
Wall integrated BIPV/T 4 x8 wall integrated BIPV/T Forced air/bouncy driven CFD modeling Determination of electricity and heat generation Evaluation of ASHP COP improvement Evaluation of GHG emission reduction 20/05/2014 17
Thermal Energy Storages (TES) System Store thermal energy when available (day time) and using it when needed (night time) Analysis based on sunny hours (diurnal thermal energy storage system), the electricity consumption of the integrated heat pump with PV/T panels would be reduced by 52%, predicted seasonal COP of 5.98. Fig. 14 Section of the testing facility 20/05/2014 18
Adding a Thermal Energy Storages (TES) system: To store thermal energy when available (day time) and using it when needed (night time) Fig. 15 Thermal storage: ventilated concrete slab (above) and gravel bed (below) 20/05/2014 19
Multiple Configurations: Charging gravel bed with pipes Charging gravel bed w/o piping forced air through gravels Charging concrete under a conditioned (room) space Charging concrete under an unconditioned (garage) space Fig. 16 Thermal storage 20/05/2014 20
Example of a typical winter night using TES Demonstration of COP enhancement and electricity consumption reduction Assuming the VCS is charged in a sunny winter day Based on outdoor temperature of -11 C 20/05/2014 21
BIPV/T + ASHP - TECHNOLOGIES FOR NEAR PARTNERS: AND 20/05/2014 22