Environmental Controls Lecture 11 Passive Heating Photovoltaics and

Environmental Controls Lecture 11 Passive Heating Photovoltaics and Active Solar Panels

Passive Heating

Passive Solar Heating Zoning: Solar Gain varies throughout the day Configure building in accordance thermal patterns and usage needs

Passive Solar Heating Three major types:

Thermal Mass Creates time lag for indoor air temperature changes and reduces temperature swings Note: Temperature swings ≥ 13ºF are not acceptable L: p. 154, F 7. 6 c&d

Thermal Mass & Insulation decreases temperature swings

Direct Gain System Heat gain occurs directly in living space Mass moderates the “greenhouse effect” L: p. 154 Fig. 7. 6 a&b

Direct Gain Sizing Guidelines Glazing area L: p. 156 T 7. 7 a

Direct Gain Sizing Guidelines Thermal Mass L: p. 157, T 7. 7 B

Direct Gain—Sizing Example Design a direct gain system with night insulation for Salt Lake City for a 40’ x 20’ (800 sf) house. H L

Direct Gain—Sizing Example Find glazing area Salt Lake City 800 sf x 26%=208 sf L: p. 156 T 7. 7 a

Direct Gain—Sizing Example Find thermal mass area 208 sf x 3=624 sf 6” thick Revise mass location to suit design conditions L: p. 157, T 7. 7 B

Direct Gain—Sizing Example Design a direct gain system with night insulation for Salt Lake City for a 40’ x 20’ (800 sf) house. If glazing is 8’ tall, how long is the window? 208 sf/8’=26’ long 8’ 26’ Note: verify solar aperture and adjust dimensions accordingly

Thermal Storage Wall Commonly known as a “Trombe Wall” Space between glazing and wall is not habitable L: p. 159, F 7. 9 a&b

Trombe Wall Provides only a limited view to outdoors Sante Fe, NM

Trombe Wall Sizing Guidelines Glazing area L: p. 156, T 7. 7 a

Trombe Wall Sizing Guidelines Wall Thickness L: p. 163, T 7. 10

Sun Spaces Sun spaces come in three configurations L: p. 164, F 7. 12 a

Sun Spaces Sloped glazing presents shading and space problems L: p. 161, F 7. 14 a-c

Sun Spaces Sun heat gain space separated from living space by thermal mass and operable partitions L: pp. 164, F. 7. 12 b&c

Sun Space Overheating Venting and insulation may be needed to prevent overheating Upper and lower outside vents: each should 5% of glazing area Upper and lower “common wall” inside vents should be ≥ 10% of glazing area L: p. 167, F 7. 14 ab

Sun Space Sizing Guidelines Glazing area Note: convert sloped glazing to the vertical equivalent L: p. 156 T 7. 7 a

Sun Space Mass Sizing Guidelines Wall Thickness L: p. 168, T 7. 14

Solar Performance

Solar Savings Fraction Amount of reduction of non-solar energy usage when solar design is used SSF=(Ewo-Ew)/Ewo =(70 -25)/70 =0. 64 or 64%

Determining the SSF — Load Collector Ratio Method Solar aperture (Ap): projection of glazing area projected onto a vertical plane H

Determining the SSF — Load Collector Ratio Method Building Load Coefficient: steady state heating load of non-solar components for one day/ºF BLC= 24 x UAnon-solar

Determining the SSF — Load Collector Ratio Method Using the earlier Direct Gain example Mass/Glazing Ratio=3 Night Insulation 6” thick “DG-B 3” S: p. 1633, T. H. 1 D

Determining the SSF — Load Collector Ratio Method Determine Load Collector Ratio BLC= 10400 Btu/ºF-day Ap= 208 sf LCR =BLC/Ap =10400/208 =50 (calculated separately)

Determining the SSF — Load Collector Ratio Method Determine Solar Savings Fraction (SSF) DG-B 3 LCR =50 SSF=34% S: p. 1656, T. H. 3

Photovoltaics and Solar Panels

Photovoltaics Produce high grade energy (electricity) NREL PV Testing Facility, Golden, CO

Photovoltaics Can be integrated into numerous building products Entrance canopy, Thoreau Center for the Environment, San Francisco, CA Roof shingles, NREL Testing Facility, Golden, Co

Solar Panels Produce low grade energy (warm/hot water) Flat Plate Solar Panel, Salt Lake City, UT