Introduction to Skylighting in equest Quick Energy Simulation Tool

Transcription

1 Introduction to Skylighting in equest Quick Energy Simulation Tool an energydesignresources.com Skylighting Design Tutorial

2 Why Consider Skylights? 2 Inexpensive method of bringing daylight into the core of low rise buildings Reliable form of energy savings SCE study found actual energy savings 98% of predicted savings (3% of systems failed) Aesthetically pleasing Link to productivity and sales increases In general, people like daylight

3 Some of the largest retailers use skylights 3 WalMart has over 1,500 skylit stores Building 250 more per year Dimming fluorescent on photocontrols Cost-effective

4 Skylights can be main source of light 4 Primary source of light in this school library Note troffers in ceiling are turned off

5 Oak Ridge High School 5 Skylights balance light from windows

6 Sacramento Municipal Utility District 6 Skylights with splayed light well

7 Skylighting design principles 7 Provide enough skylight area to provide sufficient light for most day-time hours while not providing too much area to cause excessive heat gains and losses Skylights spaced close enough together to provide reasonable uniformity Just like electric lighting design Energy savings accrue only if electric lighting turned off! Thus the need for automatic daylighting controls

8 equest has the answers to 8 How much skylight area should I install? How much energy savings do I get from using a high performance skylight? Which type of lighting controls yield the most energy savings? What is the HVAC impact of skylighting? With and without photocontrols Will peak loads increase or decrease?

9 Design it right the first time! 9

10 Download equest 10 equest is a free whole building energy simulation tool Detailed simulation model with easy to use graphical interface Available from energydesignresources.com equest is listed under software This tutorial steps you through a skylighting simulation

11 equest start-up screen 11 Start-up screen choices

12 Start-up Options 12 Two primary choices Simulate a new or pre-existing building model Multiple pages of inputs Create a weather file for the SkyCalc skylighting spreadsheet One page of inputs

13 Generating weather files for SkyCalc3 13 SkyCalc3 also available at Simple skylighting spreadsheet Not the subject of this tutorial Select climate file, energy code, and roof U-factor to generate a SkyCalc Weather file

14 Start equest Schematic Design Wizard 14 Select Create a New Project Via the Wizard Design Overview Location Building Type Area Utility rates Heating and cooling? Select Daylighting Controls to Yes

15 Building Footprint 15 Select floor to floor & floor to ceiling height Plenum and suspended ceiling assumed if Flr-to- Flr > Flr-to-Ceil NOTE: Unless Flr-to- Flr height exceeds Flrto-Clg height by > 1.0 ft., no separate above ceiling zone will be modeled

16 Skylight Components 16 skylight glazing Dome-depth skylight frame curb Light Well light well depth ceiling roof deck

17 Rule of Thumb for Spacing Skylights 17 Daylit zone around skylights is 35 degree angle from edge of skylight opening Or 70% of ceiling height (skylight edges spaced no more than 1.4 x ceiling height) Daylit area reduced by partitions H 35 < 0.7 x Gap 35 Gap H x 0.7 > 0.7 x Gap Permanent partition DAYLIT AREA

18 Adjust no. of skylights 18 For uniform daylighting, skylights should be spaced no further than 1.4 times the ceiling height For our 20 ft. ceiling height, skylights should be a minimum of 28 ft. apart from edge-to-edge. Using typical 4 ft x 8 ft skylights, this results in a minimum requirement of 4 skylights or an SRR of 2.5% for our case. If space below has partitions or shelving, space skylights closer together for full daylighting In this example we choose 8 skylights or 5% SRR

19 Adjust no. of skylights 19 To adjust skylight spacing, change the % Coverage or Skylight Dimensions In this example, 4 ft x 8 ft skylights and 5% coverage result in 8 skylights Decrease skylight size or increase % coverage to increase number of skylights or vice-versa. NOTE: If Core / Perimeter zoning pattern is used, % coverage refers to zone area not floor area.

20 Select Glazing Type 20 Category defines frame and shape (Dome vs. Flat) Frames are ordered in terms of their conductivity Metal most conductive (low R-value) Wood or vinyl least conductive (high R-value)

21 Select Skylight Properties 21 Type defines glazing visible transmittance, solar gain and clarity Ordered by visible transmittance Clear highest Grey lowest Clear skylights: Clear, bronze, grey Diffusing skylights: Clear (crystal), White, all acrylic/fiberglass

22 Select Skylight Properties 22 Choose if your skylights are diffusing or dome shaped. Different skylight types default to diffusing or domed, based on typical skylight configurations

23 Define Light Well 23 The default light well depth = plenum depth Choose inside reflectivity If no plenum, the default size is 1 ft which accounts for depth of a generic curb, and roof deck.

24 Skylight properties by NFRC ratings 24 You can also specify the NFRC rated properties of the skylight by selecting Specify Properties under Category Specify: -U-factor -SHGC - Visible Transmittance

25 Skylight properties by Window 4/5 25 You can also specify a skylight designed in LBNL s Window software v. 4/5. See equest help for more details on this method

26 Photosensor 26 Define fraction (%) of lights controlled by photosensor See example on next slide Define your desired light level at the level of your working plane. Input height of working plane under Height Above Floor

27 Fraction of Lighting Controlled 27 Example: A 20 tall space (14 zones around skylights) Yellow Skylit areas Teal Area not sufficiently daylit Lighting in yellow areas are controlled, those in teal area are uncontrolled. 24 lights controlled 11 lights uncontrolled Fraction controlled 24/35 = 69% 14 ft 14 ft

28 Lighting Controls 28 Choose your lighting control type from choices given here Lighting controls determine the method of reducing the lighting in the space when sufficient daylighting is available.

29 Dimming and Switching Controls 29 For a dimming control, the Minimum Power and Minimum Light inputs determine the lowest level of light output and the corresponding power usage by the electric lights when sufficient daylight is present.

30 Dimming Controls % 10% min-light, 20% min-power Fraction Maximum Power 80% 60% 40% 20% 0% 0% 20% 40% 60% 80% 100% Daylight illuminance (fc) / Lighting setpoint(fc) When daylight is providing 90% or more design illuminance, electric lighting is dimmed to 10% of light output, while consuming 20% of rated power. 10% min-light 20% min-power

31 Switching Controls 31 For a switching control, the number of control steps determine the stages between on and off.

32 Switching Controls 32 Fraction of maximum power Daylight illuminance(fc) / Design illuminance (fc) Separate circuiting and separate setpoint required for each step 3 steps = 100% power, 66% power, 33% power and 0% power (off) 1-step 2-step 3-step

33 Lighting Load 33 Define lighting load in Watts per sq.ft. for every area type.

34 Skylight Parametric Analysis 34 This new feature helps you determine the optimum amount of skylights (SRR) for your building By parametrically increasing the amount of skylights, or Skylight to Roof area Ratio (SRR), this analysis feature helps you identify the SRR that will maximize savings.

35 Skylight Parametric Analysis 35 Click on Perform SRR Parametric Runs to start the parametric runs. The Parametric Runs screen lets you choose the number of parametric runs. 0% - represents 0 SRR or no skylights 100% - represents design SRR, or the number of skylights currently specified in your model Review results once all simulations are done

36 Skylight Parametric Analysis 36 Energy and Cost Savings Report The result output from the analysis is a graph that shows Total Annual Energy Savings, and Total Energy Cost Savings. With these graphs it is easy to spot the optimum SRR from maximum energy and cost savings Dashed lined in the graph represents design case (shown here at 5%)

37 Skylight Parametric Analysis Daylight Illuminance Report 37 Dark shaded values show lower than acceptable daylight levels Light shaded values show acceptable daylight levels This report shows the average daylight illuminance at the reference point for each hour of the day (columns) and each month of the year (rows)

38 Output Reports 38 With Parametric Analysis, results from up to ten cases can be compared on a single graph. However, to view energy use by end use, for any of the cases, you can use equest s Results Output Mode. To view output reports select View Results Output Mode

39 Output Reports 39 Graphic results of monthly electric and gas energy consumption Breakdown of energy use by end use, and month.

40 Comparing Output Reports Cooling energy use increases with skylights Electric Lighting energy use decreases with skylights With 5% Skylights Space Heating energy use increases with skylights 40 Note that the Y-axis gets rescaled for each run Without Skylights

41 Example 1 Conditioned Warehouse 41 For this example we will consider: An air conditioned warehouse 50 ft x 100 ft in plan and with 20ft ceilings 5% Medium white, double glazed, domed skylights (VT=0.5, U=1.14, SHGC=0.47) Lighting setpoint: 10 fc Lighting Power Density (LPD): 0.75 W/sf Space has racks: 15 height, 8 aisle width Lighting controls: 2 level + Off Location: Riverside, CA (CA Climate Zone 10) Utility rates: $0.12/kWh and $0.90/therm

42 Example 1 Conditioned Warehouse 42

43 Example 1 Conditioned Warehouse 43 Using the Skylight Parametric Analysis we will identify the optimum Skylight area to Roof area Ratio (SRR) We will also consider two other skylight choices: Clear prismatic, double glazed, domed acrylic skylights (VT=0.88, U=1.14, SHGC=0.78) Clear Low-E coating, double glazed, flat glass skylights (VT=0.44, U=0.43, SHGC=0.39) VT = visible light transmittance SHGC = solar heat gain coefficient U = conductive thermal transmittance, (1/R-value)

44 Example 1 Conditioned Warehouse Not enough daylight with only 1.3% skylights to turn off all lights resulting in very little savings. Energy Savings Report Maximum savings at 6.3% SRR After the peak, the thermal losses begin to offset lighting savings The energy savings parametric analysis shows that maximum savings are at 6.3% SRR. The designed case at 5% SRR is close to maximum View Output Reports to see which thermal loss, excessive solar gain or heat loss causes savings to decline 44

45 Example 1 Conditioned Warehouse Energy Cost Savings Report 45 The energy cost savings parametric analysis also shows the optimum SRR to be 6.3% as it gives the maximum savings ~ $2,000.

46 Example 1 Conditioned Warehouse 46 Clear Prismatic Low-e Clear Comparing the two other skylight types, we find that with a low-e glazing skylight, the max savings are reached at 6.3% as compared to 2.5% for clear prismatic. Furthermore, the max savings for both skylights are almost the same (~14,000 kwh)

47 Example 1 Conditioned Warehouse 47 RESULTS With this example, it is clear that same max savings can be achieved using a much cheaper skylight (clear prismatic vs low-e glass), and also by using a smaller area of the cheaper skylights (2.5%SRR) Other non-energy considerations may still motivate the selection of glass skylights These results are specific to the conditions defined for this particular case and the result will differ if any of them are changed. The equest tool allows you to consider what is important for your building in your climate Using equest s Skylight Parametric Analysis Tool it becomes possible to compare various scenarios over a broad range of skylight areas

48 Example 2 Retail Store 48 For a second example we will consider: An air conditioned retail store 100 ft x 100 ft in plan and with 20 ft ceilings, 5 ft wells 5% Medium white, double glazed, domed skylights (VT=0.5, U=1.14, SHGC=0.47) Fluorescent lighting Lighting setpoint: 60 fc, LPD: 2.18 W/sf Space has racks: 10 height, 10 aisle width Lighting controls: Dimming to 10% light output Location: Riverside, CA (CA Climate Zone 10) Utility rates: $0.12/kWh and $0.90/therm

49 Example 2 Retail Store 49

50 Example 2 Retail Store: Controls 50 We will consider choices for controls and determine the one with the most savings: Dimming 10% 2 level + Off Dimming min 10% light Two level + off switching 100% 100% 80% 80% Lighting Power 60% 40% Lighting Power 60% 40% 20% 20% 0% % Daylight Foot-Candles Daylight Foot-Candles

51 Example 2 Retail Store: Dimming 51 Energy Savings Report Maximum savings at 4.7% SRR The energy savings parametric analysis shows that maximum savings are at 4.7% SRR. At design case (6.3% SRR), adding more skylights increases heating and cooling loads more than additional lighting savings, total savings are reduced

52 Example 2 Retail Store: Energy Savings 52 Dimming Controls 2Level+Off Controls Comparing between the lighting control strategies, two level + off controls save ~6000 kwh more energy than dimming controls. Dimming max savings occurs at 4.7% SRR Max savings for 2 level switching occurs at 6.3% SRR

53 Example 2 Retail Store: Cost Savings 53 Dimming Controls 2Level+Off Controls Switching controls max savings is ~ $8,000/yr higher than dimming With dimming controls, max savings can be achieved at a lower SRR (4.6%), but at same SRR, switching controls still have greater savings. Designer may still choose dimming for non-energy reasons

54 Example 2 Retail Store 54 RESULTS Relative savings from different control strategies depends upon rest of the design including the SRR. equest s Skylight Parametric Analysis Tool allows to quickly evaluate this over a broad range of SRR s In this case with 6.3% SRR, 2 level switching saved more energy than dimming. Under full daylit conditions, fully dimmed system is consuming 20% power while switched system is off. Often retailers leave some lights on to show they are open. The likely switching control would leave x% of the lights on. Now which system saves more? You can answer this question using equest!

55 Daylighting resources 55 equest software and this tutorial SkyCalc skylighting design spreadsheet Skylighting Guidelines (100 pages) detailed skylighting design handbook Daylighting Guidelines Design Briefs (20 pages) Skylights with Suspended Ceilings Lighting Controls

56 Daylighting Resources: Savings By Design 56 California statewide nonresidential new construction energy efficiency program Administered by California investor owned utilities (SCE, PG&E SDG&E and SCG) Program features: Design assistance energy information and analysis tailored to the needs of your project Owner incentives help offset the initial costs of energy-efficient buildings Design team incentives reward designers who meet ambitious energy efficiency targets

57 Acknowledgements 57 This tutorial and skylighting upgrades to equest were funded by the California utility customers under the auspices of the California Public Utilities Commission Project management: Southern California Edison Diane McLean & Shelley Baumgardner Technical content: Heschong Mahone Group Jon McHugh & Mudit Saxena Technical content: JJ Hirsch Associates Jeff Hirsch, Paul Reeves, Scott Criswell & Marlin Addison