LOW CARBON HEATING FOR COMMERCIAL BUILDINGS USING GRID SUPPLIED ELECTRCITY DURING-OFF PEAK PERIODS

Transcription

1 LOW CARBON HEATING FOR COMMERCIAL BUILDINGS USING GRID SUPPLIED ELECTRCITY DURING-OFF PEAK PERIODS R. Hutcheson, P.Eng. LEED AP, CxA, S. Jorens B.Eng., D. Knapp, PhD., P.Phys., LEED AP Arborus Consulting

2 Design Approach to Achieving Affordable Low Carbon Heating Solutions and Reap the Significant Economic Benefits of a High Quality Indoor Environment

3 The issue at hand De-carbonizing building energy systems requires a switch from fossil fuels to clean/renewable energy sources Largely means, switch to electricity Heating buildings in northern climates requires a great deal of energy Need a solution that can be implemented at scale On-site generation and electricity storage too expensive for building heating

4 The Basis of our Model A practical solution, where it is not feasible to selfgenerate the energy required to heat the building Grid-connected, rather than Self-generated electricity Assumption that grid supplied electricity is cleaner than fossil fuel Ontario s electricity grid presents a low carbon energy solution

5 Ontario s Electricity Grid Mixed generation: hydroelectric, nuclear, natural gas combustion, renewables, bio-gas Base, dispatchable and variable generation; lowest cost to highest Renewables are variable sources of energy N-gas is a large carbon emitter, bio-gas much less Remaining considered zero emission at point of generation

6 Ontario s Electricity Grid Carbon Intensity varies according the mix of generators on-line and their respective carbon output. Off-peak load periods use less or no natural gas, depending on the amount of renewables on line.

7 Range of Carbon Intensities

8 The Building Model Two-story office building located in Ottawa, similar to the NECB Archetype, Small Office A very common building type & size Table 1 - Office Building Specifications O/A Design Temp C F Interior Temp 22 0 C 72 0 F Building Width 50m 164ft Building Depth 33.5m 110ft Total Floor Area 3321m 2 35,746ft 2 Radiant Water Delta T C 15 0 F Heated Floor Area m 2 25,000ft 2 Window to Wall Ratio 40% FIGURE 3 TWO-STORY OFFICE BUILDING (AS MODELED IN EQUEST)

9 Building Envelope Thermal Performance Code & Improved values align with NECB 2011 building envelope values for zone 6 and zone 8 respectively Overall Uvalues: 0.09BTU/hr-F-ft 2 / W/m 2 -C Heat Energy reduction from 883GJ to 692GJ 9.61T annual GHG Savings 21.7% Energy & GHG reduction from the high performance envelope

10 Occupant Comfort Implications Results in exterior wall surface temperatures closer to the space environment Reduces temperature radiation from the occupant and surrounding surfaces Greater occupant satisfaction Percent of People Expressing Discomfort due to Asymmetric Radiation. (ASHRAE, 2013, p. 9.14)

11 Heating System Benefit from the Envelope Design Suitable conditions for low water temperature heating Meeting heating needs & occupant comfort Low temperature water allows for the highest efficiency heating delivery Generation: condensing boilers Delivery: radiant slab

12 Heating System Benefit from the Envelope Design Hydronic heating has two modes of heat transfer; conduction & radiation Far more efficient than forced air convective systems Temperatures of water determines the type of radiator that can be used. Baseboard radiators require higher temperatures Radiant slab permits lower temperatures

13 Heating System Benefit from the Envelope Design

14 Condensing Boilers FIGURE 6: TEMPERATURE RANGE FOR CONDENSING BOILERS. (ASHRAE SYSTEMS AND EQUIPMENT )

15 Accumulated Results High Performance Envelope + Condensing Boiler Reduces delivered heating energy from 883GJ to 502GJ A 43% energy & GHG reduction tons CO 2 saved annually

16 Low Temperature Radiant Temperatures Occupant Comfort: Surface temperatures of the radiant slab important factor Influences the Mean Radiant Temperature Operative temperatures in the space are those that the occupant feels Combination of MRT & air temperatures

17 Low Temperature Radiant Temperatures Occupant Comfort: Warmer surfaces minimize the radiation losses by the human body More comfortable when temperatures in the occupied zone are close to body temperatures

18 Ventilation Ventilation is the most significant component of the building s heating requirements Minimize the ventilation to meet occupant demand Maximize the effectiveness of the ventilation delivered

19 Ventilation Dedicated Outdoor Air System (DOAS) Significantly reduces the volume of supply air compared to a standard mixed-air system (fan power) Superior modulation of ventilation air (conditioning of air)

20 DOAS + CO 2 Monitoring CO 2 is a good proxy for the number of occupants in the space Variable OA supply according # of occupants Allows you to shut off OA during unoccupied hours

21 Conventional Mixed Air Systems Total air-flow requirements need to meet for sensible loads and the latent loads. The total airflow is approx. 20,000cfm. CONVENTIONAL MIXED AIR SYSTEM, SOURCE: HEATING IN COMMERCIAL BUILDINGS, GRUNDFOS

22 Dedicated Outdoor Air Systems Total air-flow is reduced due to the de-coupling of sensible loads and latent loads. The total airflow is approx. 2,700 cfm. DEDICATED OUTDOOR AIR SYSTEM, SOURCE: HEATING IN COMMERCIAL BUILDINGS, GRUNDFOS

23 Ventilation Effectiveness Refers to how much air is delivered to the breathing zone The effectiveness of the OA delivery system plays an valuable role reducing energy requirements Conventional mixed-air systems use ceiling supply of warm air 8C higher than space temperature. Has an effectiveness of 0.8 (ASHRAE )

24 Ventilation Effectiveness Low Temperature systems with DOAS that de-couple the latent & sensible loads allow for an air delivery equal to the space temperature Effectiveness Effectiveness 1.0 Effectiveness Cfm Total Maximum Outdoor Air Required Increases the effectiveness to 1.0 Reduces the OA requirement by 694 cfm

25 DOAS + Heat Recovery DOAS is ideal for recovery of latent and sensible energy from exhaust air ERV with 75% sensible & 72% latent effectiveness DOAS + H/R = 14.5% savings in energy & GHGs

26 Ventilation Results DOAS + Heat Recovery Reduces delivered heating energy from 502GJ to 374GJ A 14.4% energy & GHG reduction 6.4 tons CO 2 saved annually

27 Summary of Load Reduction Strategy Design Features Heating Energy GHG s (tons CO 2 e) Baseline Code Building U=0.588 W/m 2 -C 883 GJ High Performance Envelope U=0.517 W/m 2 -C 692 GJ Low Temperature Heating System 502 GJ DOAS + Heat Recovery 374 GJ Heating Energy During Off-Peak 103,900kWh

28 Fuel-Switching: Natural Gas to Off-Peak Electricity

29 Lowest GHG Intensive Utility Energy Supply Off Peak periods when generation is dominated by hydroelectric & nuclear Requires storage to meet energy needs for On- Peak periods Thermal storage

30 Thermal Storage Water and/or other mass, Phase-change Water: heated to supply temperature of radiant floor Required volume = 100m 3 Thermal mass ceramic bricks: heated to much higher temperatures Required volume = 8.3m 3

31 Thermal Storage Steffes electric thermal storage (ETS) technology MODEL 9180 (80kW Storage Module) Thermal Output (kw) ) Discharge Time (Hrs)

32 Thermal Control Strategies 7PM 7AM 9AM 4PM 7PM ELECTRIC HEATING ON OFF T day STORAGE TEMP T = -8.3 C (15 F) T night Thermal Energy Storage Storage Release Heating Slab Energy Release T day SLAB TEMP Energy Stored in Slab T night

33 Thermal Operating Complaints Predicted rate of unsolicited thermal operating complaints (ASHRAE, 2013, p. 9.13)

34 Summary of Energy & GHG Results

35 Real Economic Benefits In an owner-occupied building, the business owner receives a double benefit of energy savings and enhanced indoor environmental quality, yielding significant financial rewards from increased employee productivity

36 The Value of Productivity Accepted Ratio 100:10:1 Employees (100): Building Costs (10): Energy (1) Source: Yudelson, J. (2008). The Green Building Revolution. Washington: Island Press

37 Quick Calculations Salary Cost: 166 x $65,000 = $10,790,000 1% Productivity Gain = $107,900 annual economic benefit Premium on $7,149,200 construction = $214,475 Premium on annual energy cost = $ year Return on Investment = 630% (13% annual)

38 Conclusion GHG INTENSITY tons CO 2 Energy Savings Code Building Heated by Natural Gas CARBON REDUCTION DESIGN STAGES GHG Savings Energy Savings Energy Savings Optimized Ventilation Strategy Low Temperature Hydronic Heating High Performance Envelope IMPROVED OCCUPANT COMFORT IMPROVED OCCUPANT COMFORT EMPLOYEE SATISFACTION, WELL-BEING & PRODUCTIVITY GAINS Off-Peak Electricity Fuel Source IMPROVED OCCUPANT COMFORT Well designed buildings can save significant GHGs and improve the productivity, wellness and satisfaction of employees.

39 Conclusion We can meet Architecture 2030 goal for 2025 now!

40 In Closing Thank you for attending this session, we hope you found it valuable. Enjoy the rest of the conference R. Hutcheson, P.Eng. LEED AP, CxA, S. Jorens B.Eng., D. Knapp, PhD., P.Phys., LEED AP