Cashing In on Rooftop Rays: Conducting Online Solar Site Assessments

Transcription

1 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

2 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; 1. Developing and Organizing Content: generate, gather, and organize ideas and information to write for an intended purpose and audience; SPECIFIC EXPECTATIONS By the end of this course, students will: 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 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

3 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 ) 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 3

4 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. 4

5 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! 5

6 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 ( and Bing maps ( - Observe streetview, bird s eye view etc. to assess shading issues, whether roof is flat, sloped etc - Go to 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 6

7 - 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 *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. $ 7

8 GCC Solar Site DATA SHEET Plug in your calculations from above. You will use this sheet to produce your Excel document A. Square Footage of Roof: sq. ft. 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) F. AC Energy Output/year kwh G. DC Energy Output/year kwh H. Solar Income after 20 years $ I. Capital Gain/Loss: $ 8

9 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) 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 10-50kw) $.802/kwh for systems 10kw or smaller or $.713/kwh for systems between kw $1300 per kw for systems 10kw or smaller or $1/watt for systems between 30-50kw Conversions 1 foot metres 1 metre 1000 mm 1 foot 12 inches 1 kw 1000 watts 9

10 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 30- degree 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. Our Power - A not-for-profit information hub on rooftop solar and community power Green Energy Act Alliance - More information on the GEA 10

11 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: C. Maximum Size of Solar Array (round to 1 decimal point): 3.4 kw system D. System Cost: $32,640 ** G. Orientation: degrees South H. AC Energy Output/year (kwh) 3866 I. DC Energy Output/year (kwh) Annual Solar Income (see Calculations Sheet) $ J. Solar Income after 20 years $62, K. Capital Gain/Loss: $29, ** Houses with a flat roof will have an added Racking System cost (see Calculations Sheet)

12 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) 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 kw $1300 per kw for systems 10kw or smaller or $1/watt for systems between 30-50kw Conversions 1 foot metres 1 metre 1000 mm 1 foot 12 inches 1 kw 1000 watts

13 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: 300 B. Available Roof Space in metres: C. Maximum Size of Solar Array (round to 1 decimal point) in kw 3.4 D. System Cost: $25,568 G. Orientation: degrees South H. AC Energy Output/year (kwh) 3866 I. DC Energy Output/year (kwh) Annual Solar Income (see $3, Calculations Sheet) J. Solar Income after 20 years $62, Cumulative solar income over 20 year contract period Year Cumulative Income Gain/Loss 1 $3, ($22,467.65) 2 $6, ($19,367.12) 3 $9, ($16,266.59) 4 $12, ($13,166.06) 5 $15, ($10,065.53) 6 $18, ($6,965.00) 7 $21, ($3,864.47) 8 $24, ($763.94) 9 $27, $2, $31, $5, $34, $8, $37, $11, $40, $14, $43, $17, $46, $20, $49, $24, $52, $27, $55, $30, $58, $33, $62, $36, Average Monthly AC Energy Output of Solar Installation (kwh)