here comes the sun – applications of solar energyhere comes the sun – applications of solar...
TRANSCRIPT
Marc Rosenbaum, P.E. – South Mountain Company – West Tisbury, MA
Here Comes The Sun – Applications of Solar Energy
Learning objectives
1 – Participants will learn how to quantify the amount of sun reaching a surface 2 – Participants will learn how these energy flows compare with the loads of advanced buildings 3 – Participants will learn how to apply the sun’s energy to serve building loads 4 – Participants will have fun
Agenda
1 – Solar gain calculations with PVWatts 2 – Solar gain calculations with AVOTS 3 – Daylight factor calculations 4 – Case study
How much energy is in sunshine?
Introducing PVWatts http://www.nrel.gov/rredc/pvwatts/
PVWatts
PVWatts Output
Back to PVWatts – Pick the State
PV Watts – Pick the City
PV Watts Input Page
PV Watts Input Page
PVWatts
Solar insolation by orientation
-
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
BTU/ft2/month
South vertical
East vertical
North vertical
West vertical
Solar insolation by orientation
-
10,000
20,000
30,000
40,000
50,000
60,000
70,000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov
BTU/ft2/month
South 42 degree pitch
Horizontal
South vertical
East vertical
North vertical
West vertical
Calculate Monthly Solar Gain
Insolation x 317 x days/month = BTU/ft2/month
Calculate Window Solar Gain BTU/ft2/month x ft2 x SHGC x 0.85 x % unshaded = BTU/month
Compare to Heating Load
Solar Hot Water
Compare to DHW Load BTU/ft2/month x ft2 x efficiency = BTU/month
Solar Electricity
Solar Electricity
kWh/kW
Solar Electricity
Clear Day Hourly
Introducing AVOTS http://www.pge.com/mybusiness/edusafety/training/pec/toolbox/arch/calculators.shtml
Clear Day Hourly
Clear Day Solar Gain
Daylighting with Toplighting
Daylighting with Toplighting
Simple Calculation of Effective Aperture for overcast period daylighting from above Inputs: - Skylighting aperture (skylight area/skylit floor
area) - Glazing visible light transmission (VLT) - Well factor (WF) - Dirt/screen factor of 0.85
Effective aperture = Skylighting aperture x VLT x WF x 0.85
Well Factor
How much light that enters a skylight well gets into the space below First calculate Well Cavity Ratio (WCR): WCR = 5 x H x (W + L) / (W x L) Say a skylight is 4’ x 4’ and the well is 3’ deep - WCR = 7.5
Daylighting with Toplighting
A WCR of 7.5 with a reflectance of 0.80 has a Well Factor of 0.68
Case Study – West Tisbury Project
South Mountain Company Photos Derrill Bazzy
Case Study – West Tisbury Project
• 3,000 ft2 multipurpose building – gallery, shop, greenhouse, solar electricity
• Not heated, but high quality thermal envelope and very tight construction
Solar applications include solar electricity, solar greenhouse with remote thermal storage, daylighting
Solar Electricity
• Estate usage of 36,000 kWh/year and objective of net zero electricity
• Buildings are heated with propane; swimming pool converted from propane to a heat pump
• Objective of providing power when the grid is down led to a bi-modal system with SMA grid-tied and off-grid inverters with battery banks
• 35 kW of Sunpower panels mounted on the standing seam roof – expected annual output of ~ 45,000 kWh
Solar Electricity
Solar Thermal
• Solar greenhouse designed to keep plants at 50F or more through the winter without heating
• Glazing is double low-e argon Cardinal 180 • When greenhouse temperature is greater than thermal
storage temperature a blower turns on to transport heated air from the greenhouse to the basement level thermal storage
• Heat retrieval during cold night time conditions is via passive natural convection
Solar Thermal
• Clear day calculations on vertical and horizontal glazing to assess thermal storage need – final design has 300 five gallon water containers that store 125,000 BTU over a 10˚F rise – concrete in the basement adds significant additional storage
• Peak hourly net gain calculation to size the blower
Solar Thermal
Solar Thermal
Solar Thermal
Solar Thermal
Daylighting
• Both gallery and shop were designed with little sidewall glazing
• Toplighting via a continuous ridge skylight was chosen to daylight these spaces
• A Daylight Factor of 2% was the target • Glazing is triple low-e argon Cardinal 272 – VLT
is 56%
Daylighting
Daylighting
Daylighting
Daylighting
Daylighting
Thank you
http://www.energysmiths.com/ http://thrivingonlowcarbon.typepad.com/ http://www.southmountain.com/