Cashing In on Rooftop Rays: Conducting Online Solar Site Assessments

Green Collar Career co-op students at the Exhibition Place solar array A national map of solar PV outputs across Canada

Ontario hot spots for solar PV

Summary In this grade 12 math exercise, student will be given a contextualized introduction to the Green Energy and Green Economy Act’s Feed-In Tariff program. Using web tools and the provided handouts, students will work in pairs (or individually, for a smaller group) to perform a solar site assessment on their homes. Students will use their collected data produce an Excel spreadsheet detailing the house’s solar potential and solar income, and present their findings along with a one-page recommendation report. Sample sheets have been attached for your reference (See Appendix) Estimated Activity Time: 4-5 hours Required equipment: One computer per pair of students, Internet access, MS Excel, MS Word, calculator, GCC Solar Site Data Sheet (see Activity Outline section), GCC Solar Site Calculations Sheet (see Activity Outline section) Curriculum Links COURSE

MCT4C - D. Applications of Geometry 2. Solving Problems Involving Geometry

ENG4C - Writing

OVERALL EXPECTATIONS By the end of this course, students will: 2. solve problems involving two-dimensional shapes and three-dimensional figures and arising from real-world applications;

SPECIFIC EXPECTATIONS By the end of this course, students will:

1. Developing and Organizing Content: generate, gather, and organize ideas and information to write for an intended purpose and audience;

1.1 identify the topic, purpose, and audience for a variety of writing tasks 1.3 locate and select information to effectively support ideas for writing, using a variety of strategies and print, electronic, and other resources, as appropriate 1.4 identify, sort, and order main ideas and supporting details for writing tasks, using a variety of strategies and selecting the organizational pattern best suited to the content and the purpose for writing

2.2 perform required conversions between the imperial system and the metric system using a variety of tools (e.g., tables, calculators, online conversion tools), as necessary within applications 2.3 solve problems involving the areas of rectangles, parallelograms, trapezoids, triangles, and circles, and of related composite shapes, in situations arising from real-world applications

     

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Background Information What is Solar PV? Photovoltaic Solar (or Solar PV) is a great way to generate clean, renewable electricity. A solar panel consists of individual cells made of silicon. When the sun hits the panel, the molecules in the silicon get excited, and travel through copper wiring to an inverter. The inverter converts the DC (direct current) energy from the solar panel cells to AC energy (alternating current), which is used to power our grid. With the passing of Ontario’s Green Energy and Green Economy Act, it is now easier than ever to get solar panels on rooftops. Part of the act includes the Feed-In Tariff Program, which allows companies, communities and homeowners to set up their own renewable energy projects, and sell the energy they produce back to the grid through a special 20-year deal with the province. This gives individual homeowners the power to produce electricity with the potential to bring in significant long-term financial benefits. Currently, the province is offering 80.2 cents per kWh of electricity produced for small solar PV installations (or 71.3 cents per kWh for mid-sized systems)- that’s almost double the previous rate! The Green Energy Act also promises new careers opportunities, and is expected to bring 50,000 new green jobs to Ontario over the next 3 years! (For more info on green jobs, visit www.greencollarcareers.ca) There are 3 main factors that determine the amount of energy you can generate from your solar PV installation (ie. your solar output) Orientation Sunlight is most concentrated at the equator. The sun passes from east to west directly above the equator line. Because we live in the Northern hemisphere, a solar array that faces True South (in the direction of the equator) will receive maximum exposure from the sun. (Conversely, if we lived in the Southern hemisphere, we would want our solar array to face True North, towards the      

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equator). Despite being far from the equator, Toronto can still produce quite a bit of solar energy because solar panels perform very well in cold climates! When assessing the solar potential of your roof, you must determine your roof’s orientation. The closer to True South the orientation is, the more solar energy your PV installation (or your solar array) will be able to generate. Generally speaking, True South, south-east or south-west are the most optimal orientations for a solar PV array in Toronto. Tilt It makes a big difference whether your roof is sloped at an angle or flat, since this determines exactly how much sunlight will reach your array. If it is sloped, you ideally want your roof slope to face south, and if it is flat, you will want to position your array at a good angle to maximize its sun exposure. Tilt refers to the angle at which a solar panel is positioned in relation to a horizontal surface. In Toronto, the best tilt angle of a solar system is about 30°. Tilt also determines how big your solar array can be. On a sloped roof, the panels can be laid flush against the rooftop, edge-to-edge. Typically for sloped roofs, you can assume a 1kw PV array will take up 88 square feet of roof space. On a flat roof where the panels have to be raised at a 30° angle, however, you will not be able to lay the panels edge-to-edge, as this would mean that one panel would be in the shadow of another. Because of this, the panels must be spread further apart on the roof to avoid shading. Typically for flat roofs arrays tilted at a 30° angle, you can assume a 1kw PV array will take up 130 square feet of roof space.

     

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DC-AC Inverters When calculating the actual amount of electricity your solar array will generate, we must also consider the derate factor. This refers to the loss rate in energy of converting direct current electricity (DC) to alternating current electricity (AC). Therefore, every solar PV installation must also include an inverter, which converts the DC electricity from your solar array to the AC electricity that is fed back to the Ontario grid (see diagram above). Calculating the derate factor is very complicated, as it involves many different variables, but it is generally safe to assume a loss rate of 20%. In other words, only 80% of the DC power your solar array produces will be available to sell to the grid.

Hmm…..   Does  the  energy  I  generate  from  my  solar  installation     provide  power  for  my  home?           Contrary  to  popular  belief,  your  solar  output  does  not  technically  provide  electricity  for   your  home-­‐  the  energy  goes  straight  out  to  the  grid,  and  separate  meter  tracks  electricity   from  the  grid  going  into  your  house.  This  is  to  ensure  that  your  home  energy  supply   remains  constant  and  reliable.     However,  the  electrons  you  produce  from  your  solar  installation  likely  won’t  go  far.  So   theoretically,  they  may  be  powering  your  neighbour’s  home  down  the  street,  or  they  may   even  make  a  “U-­‐turn”  and  come  right  back  into  your  home!          

     

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Activity Outline In this activity, you will use online tools to perform a solar assessment of your roof and estimate the amount of renewable energy it can produce. Using this data, you will calculate the potential solar income the roof can generate through the Ontario Green Energy Act’s Feed-in-Tariff Program, and create an Excel spreadsheet detailing your findings. Step by Step Instruction Provide spaces for students to plug in calculations as they go along and have them fill in DATA SHEET at end. Provide the CALCULATIONS SHEET for reference. Determine available roof space for solar PV array -­‐ Enter home address into Google maps (www.maps.google.com) and Bing maps (www.bing.com/maps) -­‐ Observe streetview, bird’s eye view etc. to assess shading issues, whether roof is flat, sloped etc -­‐ Go to www.roofray.com, click Get Solar Estimate, and type home address into address bar -­‐ Measure sq. footage of roof by clicking along edge of the roof and around obstructions or shaded areas (leave a little space along the roof edge for installer safety). Use the Start Over and Remove Last Point buttons as needed. Orientation -­‐ If the roof is sloped, adjust the red orientation line so that it is parallel to the north-south axis of the roof edge -­‐ If the roof is flat, leave orientation line as is (180 degrees) and change the Roof Pitch or Tilt slider to 0 -­‐

Record Area at bottom of roofray page. Available square footage for solar array A. ____________ sq. ft. Available roof space for solar array in metres B. ____________m

Determine solar system size and cost -­‐ Divide available sq. footage by 88 (sq. feet/kw for sloped roof) or 130 (sq. ft./kw for flat roof, 30° tilt) to get maximum system size in kw C. _______ kw system      

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-­‐ -­‐

Use Calculation sheet to determine the cost of your system. Remember to convert watts to kilowatts! System Cost D. $__________ Record Orientation in degrees (include direction: North, South, East, West) from roofray.com at the bottom of the page (you will need this for the next section) E. ___________degrees __

-­‐ Determine Solar Output and Solar Income -­‐ Go to PV watts V.1 website http://rredc.nrel.gov/solar/codes_algs/PVWATTS/version1/ *Alternately, try Googling “PV Watts Version 1” -­‐ Along the right-hand column, click CANADA and find ON-Toronto. Then go to the bottom and click “Start PV WATTS for International Sites” Plug in: DC RATING (ie. System size C.) DC TO AC DERATE FACTOR (.80) ARRAY TILT (30 degrees) and ARRAY AZIMUTH (ie. Orientation in degrees E.) Then click Calculate Record the annual AC energy output of your system (right-hand column) AC ENERGY (kwh) F. ____________ kWh (Use the derate factor to determine the original annual DC energy output of your system G. __________kWh) Calculate solar income after 20 years H. $___________ Calculate TOTAL income gain (minus capital costs) I. $________

     

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GCC Solar Site DATA SHEET Plug in your calculations from above. You will use this sheet to produce your Excel document sq. ft. A. Square Footage of Roof: B. Available roof space in metres:

m

C. Maximum Size of Solar Array (round to 1 decimal point):

kw system

D. System Cost:

$

Racking system cost (see Calculations Sheet): Total System Cost

$

E. Orientation:

degrees (north/east/south/west) kWh

F. AC Energy Output/year

$

G. DC Energy Output/year

kWh

H. Solar Income after 20 years

$

I. Capital Gain/Loss:

$

     

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GCC Solar Site CALCULATIONS SHEET This sheet provides handy conversions and figures to help you calculate your findings. 20% loss rate from DC electricity to AC DC to AC derate electricity factor System Size

RACKING system for flat roof (refer to system size)

88 sq. feet/kw (sloped roof or edge-toedge layout) or 130 sq. feet/kw (flat roof array with 30 degree tilt- factors in shadow from each angled panel) or 98 sq. feet/kw (flat roof array with 20 degree tilt- factors in shadow from each angled panel) $7.50/watt (for systems 10kw or smaller) $6.00/watt (for systems between 1050kw) $.802/kwh for systems 10kw or smaller or $.713/kwh for systems between 10-250kw $1300 per kw for systems 10kw or smaller or $1/watt for systems between 30-50kw

Conversions 1 foot 1 metre 1 foot 1 kw

0.3048 metres 1000 mm 12 inches 1000 watts

System cost Solar Income

     

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EXCEL SHEET Produce an excel spreadsheet to show your parents whether a solar PV installation would be a good investment for your house. The spreadsheet should record all the findings from your data sheet, complete with formulas. The spreadsheet should also include: 1. A graph or chart of the average monthly AC energy output in kWhs. Record monthly energy outputs from PV Watts and convert the data into a graph or chart (*if you are doing the bonus question, compare monthly outputs of a tilted 20-degree solar array vs. a tilted 30degree solar array) 2. Cumulative solar income over 20 year contract period (Year 1 – Year 20) Make the spreadsheet as easy-to-read and aesthetically pleasing as possible. (Use colours and photos!) RECOMMENDATION REPORT Write a formal one-page report on your findings. Based on your calculations, would a solar installation on your roof be a good investment? Why or why not? What would be the potential earnings? How long would it take for the system to start making money? What are some factors that make your house a good/bad site for solar? *Note: Although considerable effort has been made to supply real data and accurate numbers in this exercise, the data collected from this process should only be considered as an approximation. For an accurate assessment of your home or business, please contact a professional solar installer or visit ourpower.ca, a not-for-profit community solar consultant. For More Information: Green Collar Careers - A youth-oriented website on the range of career options available in the new green economy. http://www.greencollarcareers.ca Our Power - A not-for-profit information hub on rooftop solar and community power http://www.ourpower.ca Green Energy Act Alliance - More information on the GEA http://www.greenenergyact.ca/

     

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  Appendix A. Sample Data Sheet

Cashing In on Rooftop Rays: Conducting Online Solar Site Assessments Address: 201 Crawford Ave, Toronto ON Note: Students conducting a site assessment on the same house may still end up with slightly different results, depending on the roof area determined by roofray.com (see accompanying document) GCC Solar Site DATA SHEET Plug in your calculations. You will use this sheet to produce your Excel document A. Square Footage of Roof: 300 B. Available Roof Space in metres: 91.44 C. Maximum Size of Solar Array (round to 1 decimal point): D. System Cost: ** G. Orientation: H. AC Energy Output/year (kWh) I. DC Energy Output/year (kWh) Annual Solar Income (see Calculations Sheet) J. Solar Income after 20 years K. Capital Gain/Loss:

3.4 $32,640

kw system

165.3 degrees South 3866 4639.2 $3100.53 $62,010.64 $29,370.64

** Houses with a flat roof will have an added Racking System cost (see Calculations Sheet)

 

 

GCC Solar Site CALCULATIONS SHEET This sheet provides handy conversions and figures to help you calculate your findings. DC to AC derate factor 20% loss rate from DC electricity to AC electricity System Size

System cost Solar Income RACKING system for flat roof (refer to system size) Conversions 1 foot 1 metre 1 foot 1 kw

 

88 sq. feet/kw (sloped roof or edge-to-edge layout) or 130 sq. feet/kw (flat roof array with 30 degree tilt- factors in shadow from each angled panel) or 98 sq. feet/kw (flat roof array with 20 degree tilt- factors in shadow from each angled panel) $7.50/watt (for systems 10kw or smaller) $6.00/watt (for systems between 10-50kw) $.802/kwh for systems 10kw or smaller or $.713/kwh for systems between 10-250kw $1300 per kw for systems 10kw or smaller or $1/watt for systems between 30-50kw

0.3048 metres 1000 mm 12 inches 1000 watts

SAMPLE EXCEL SHEET

APPENDIX B. SAMPLE EXCEL SHEET Cashing In on Rooftop Rays: Conducting Online Solar Site Assessments

Address: 201 Crawford Ave, Toronto ON A. Square Footage of Roof: B. Available Roof Space in metres: C. Maximum Size of Solar Array (round to 1 decimal point) in kw

D. System Cost:

300 91.44 3.4

$25,568

G. Orientation: H. AC Energy Output/year (kWh) I. DC Energy Output/year (kWh) Annual Solar Income (see Calculations Sheet) J. Solar Income after 20 years

165.3 degrees South 3866 4639.2 $3,100.53 $62,010.64

Cumulative solar income over 20 year contract period Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Cumulative Income Gain/Loss $3,100.53 ($22,467.65) $6,201.06 ($19,367.12) $9,301.59 ($16,266.59) $12,402.12 ($13,166.06) $15,502.65 ($10,065.53) $18,603.18 ($6,965.00) $21,703.71 ($3,864.47) $24,804.24 ($763.94) $27,904.77 $2,336.59 $31,005.30 $5,437.12 $34,105.83 $8,537.65 $37,206.36 $11,638.18 $40,306.89 $14,738.71 $43,407.42 $17,839.24 $46,507.95 $20,939.77 $49,608.48 $24,040.30 $52,709.01 $27,140.83 $55,809.54 $30,241.36 $58,910.07 $33,341.89 $62,010.60 $36,442.42

Average Monthly AC Energy Output of Solar Installation (kWh)