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Can your roof fit solar?

Can your roof fit solar?
Can your roof fit solar?
Columbia Press/CHK

A solarized roof system can help save money besides helping save the environment.

This is even fostering an upsurge in localized community-college green-jobs certificate programs.

In fact, according to the U.S. Department of Energy, 2013 was a record-breaking year for the solar power industry. The addition of 23,682 workers brings the total to 142,698 Americans employed in the solar industry.

While the figure is paltry compared to the number of unemployed, the number of solar installations will likely sky rocket due to climate change. Imagine the snowball effect of having less available hydroelectric power due to drought and divestment in dams.

Conserve Energy Future explains why solar energy is natural, clean energy. By reducing one's carbon footprint in half, one is helping reduce greenhouse gases, such as carbon dioxide pollution, while also hopefully saving on the utility bills.

A key question for initial consideration is "Do I have the space for it?"

Here is a short list of considerations for ordering or installing flat panel solar photovoltaic (PV) modular arrays: (Refer to the photos)

  1. Roof condition/structure. What is the condition of your roof? Do you already have a green roof where mixed purposes won't work (eg. water collection vs. solar panels). Can the roof support extra weight?
  2. Roof material. Certain roof materials can create obstacles for solar panel installations. These include: traditional tile, wooden shakes, thatched, rough cut stone, recycled rubber, copper
  3. Roof direction (shading) (rain shadow). Consult the solar radiation map or solar insolation chart for your area. Note that the data doesn't include the effects of local shade trees, building cover, or other possible reductions affecting efficient energy collection.
  4. Solar Photovoltaic (PV) Modules are flat plates packed full of (poly) crystalline silicon cells which conduct electricity when their electrons are excited by sunlight. For estimating the number of panels needed, figure that each panel generates 200 Watts apiece. (1 Kilowatt=1000 Watts)
  5. Number of Panels: For instance, the 4 KW-hour solar system, which would cover most small appliances, would require about 20 panels. This is obtained by dividing 4000 Watts by 200 Watts per panel. The formula: (4 KW x 1000 W/KW)/200 Watt/panel= 20 panels.
  6. Panel dimensions are approximately 40" wide by 60" long and generally weigh between 45-52 pounds. Smaller sized panels are easier to lift whenever necessary. For estimating the space required on the roof, 3.33 ft wide by 5 ft long= 17 square feet apiece.
  7. Measure the roof space needed on asbuilt plan drawings. The roof slope should be included in the area calculation. For instance, divide the horizontal length shown on the plan drawing by the cosine of the roof pitch angle to obtain the total slope length. (Check your measurements by climbing on the roof or taking floor measurements inside).
  8. Example: For a 4 KW solar system with 20 panels, the roof space required would be: 20 panels x 17 square feet/panel= 340 sf. However exactly where the panels will fit will vary according to roof type. They may fit along the south side of a gable roof, or have to be divided among portions of a dormer roof.
  9. Other options of course are available, such as ground mounted solar panel systems. In fact, these may be more flexible with regard to accessibility and maintenance, particularly if you intend to add-on slowly, build it yourself, or go off-grid with a back-up battery system.

This list of considerations is by no means conclusive, but it can guide you in the decision-making and consultation process of a significant energy-saving investment.

Although there are certainly challenges to solar PV array installs, such as comparing sales contracts and submitting designs to techno-regulatory agencies, there are quite a number of free, helpful, informational resources, some of which are included below.

Links to Resources:

1. http://www.conserve-energy-future.com/category/solar-energy

2. http://www.bls.gov/ooh/construction-and-extraction/solar-photovoltaic-installers.htm

3. http://www.pole-barn.info/roof-pitch.html

4. http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/

5. http://www.solarpanelsplus.com/products/solar-pv-panels/

6. http://energy.gov/energysaver/articles/estimating-appliance-and-home-electronic-energy-use

7. http://www.mountainbreezenews.com/index.php?nav=20110506/customizeit&typ=1

Can your roof fit solar?
Can your roof fit solar? Columbia Press/CHK

Can your roof fit solar?

1. Roof condition/structure. What is the condition of your roof? Do you already have a green roof where mixed purposes won't work (eg. water collection vs. solar panels).  Can the roof support extra weight?

Image of a Shake Roof in Romania
Image of a Shake Roof in Romania from Wikipedia

Image of a Shake Roof in Romania

 

Check with building department on allowable load limitations

2. Roof material. Certain roof materials can create obstacles for solar panel installations. These include: traditional tile, wooden shakes, thatched, rough cut stone, recycled rubber, copper

Hours of Solar Shown on Radiation Map
Hours of Solar Shown on Radiation Map National Renewable Energy Lab

Hours of Solar Shown on Radiation Map

U.S. Department of Energy database has solar radiation maps - select annual, average, flat panel

3. Roof direction (shading) (rain shadow). Consult the solar radiation map or solar insolation chart for your area.  Note that the data doesn't include the effects of local shade trees, building cover, or other possible reductions affecting efficient energy collection.

Polycrystalline Solar PV Panel
Polycrystalline Solar PV Panel Savegreenmoney.com

Polycrystalline Solar PV Panel

Multicrystalline Solar PV Panel generates approximately 200 Watts

4. Solar Photovoltaic (PV) Modules are flat plates packed full of (poly) crystalline silicon cells which conduct electricity when their electrons are excited by sunlight. For estimating the number of panels needed, figure that each panel generates 200 Watts apiece.

(1 Kilowatt=1000 Watts)

Plan Ahead for Steep Roofs
Plan Ahead for Steep Roofs Solar Panels Plus

Plan Ahead for Steep Roofs

Calculate the number of  panels you might need to fit on your roof.

5. For instance, the 4 KW-hour solar system, which would cover most small appliances, would require about 20 panels. This is obtained by dividing 4000 Watts by 200 Watts per panel. 

The formula:
(4 KW x 1000 W/KW)/200 Watt/panel= 20 panels.

Polycrystalline PV Panels can be Weighty
Polycrystalline PV Panels can be Weighty Columbia Press/CHK

Polycrystalline PV Panels can be Weighty

Specifications for panel selection should include exact dimensions, weight, etc.

6. Panel dimensions are generally approx. 40" wide by 60" long and weigh between 45-52 pounds. Smaller sized panels are easier to lift when necessary.

For estimating the space required on the roof, 3.33 ft wide by 5 ft long= 17 square feet apiece.

 

Factor in Roof Pitch when sketching panel designs on roof
Factor in Roof Pitch when sketching panel designs on roof APB Pole Barns

Factor in Roof Pitch when sketching panel designs on roof

When working off as-built roof plans, remember to factor in roof pitch

7. Measure the roof space based on as-built plan drawings. The roof slope should be included in the area calculation. For instance, divide the horizontal length shown on the plan drawing by the cosine of the roof pitch angle to obtain the total slope length. (Check your measurements by climbing on the roof or taking floor measurements inside).

Off the grid system with PV panels and Water Heating Panels
Off the grid system with PV panels and Water Heating Panels Solar Panels Plus

Off the grid system with PV panels and Water Heating Panels

Be creative in considering where to fit all the panels

8. For a 4 KW solar system with 20 panels, the roof space required would be: 20 panels x 17 square feet/panel= 340 sf. However exactly where the panels will fit will vary according to roof type. They may fit along the south side of a gable roof, or have to be divided among portions of a dormer roof.

Ground mounted panel system allows add-on
Ground mounted panel system allows add-on Solar Panels Plus

Ground mounted panel system allows add-on

Ground mounted PV panels are accessible for maintenance

9. Of course other options are available, such as ground mounted solar panel systems. In fact, these may be more flexible with regard to accessibility and maintenance, particularly if you intend to add-on slowly, build it yourself, or go off-grid with a back-up battery system.