SOLAR ACCESS

The sun, along with water, is the primary fuel for your permaculture farm, and the more you can get, the more energy you’ll have to do and grow things. That’s why it’s important to determine how much sun the prospective site actually receives throughout the year.

Here, you’ll want to look at two criteria:

  • Site’s aspect
  • Sun’s movement across the site through the year

By assessing these two parameters you’ll know how much sunlight or shade you’ll be getting. That way you can decide what’s acceptable and what’s not according to your needs.

First, you need to determine the aspect of the slope, not every possible one but rather the general average slope orientation of the property, in case you get more complex terrains. You can do this from the comfort of your own home by using Google Earth.

Following this, you’ll have to make observations on the site itself with a smartphone app, as only in this way can you directly see the path of the sun across the sky.

    SITE ASPECT

     

    PART A: PLOT CONTOURS ONTO GOOGLE EARTH

    STEP 1. Locate the property on the Contour Map Creator website

    • Open the http://contourmapcreator.urgr8.ch/ website and zoom in on the property.

      Note: Don’t zoom in too much as you’re trying to get the overall picture of the topography surrounding the property as well.

    STEP 2. Draw a sampling area

    • Mark a rectangle by adding two pins onto the maps.

    STEP 3. Get a contour map

    • Adjust the plot options, use level interval of 5m/15ft

    • Click ‘Get Data’, use the sampling tab.

    STEP 4. Import contour into Google Earth

    • Scroll down and press ‘Download KML file’.

    • Once the file is downloaded, open it in Google Earth.

    PART B: ASSESS THE SLOPE ASPECT

    STEP 1. Locate the property on Google Earth

    • Launch the Google Earth application and zoom in on the property.

    • Enable the newly imported ‘Contours’ kml file in the sidebar under the places bar.

    • Zoom in to start getting the general shape of the terrain visible.

    STEP 2. Draw a line across the terrain

    • Click ‘Add Path’ tool on the Google Earth toolbar and draw a straight line perpendicular to the contour lines.

    Note: You want to get a general sense of the slope aspect in this phase, so don’t worry if you can’t get your straight line to be perpendicular to all contour lines. You are after an average slope aspect. In the on-site assessment phase, you’ll find out the exact details of the slope orientation.

    STEP 3. Assess the slope aspect

    • Make sure that Google Earth compass is set to the default position – north facing up.

    • Determine the orientation of the straight line relative to the north.

    • In the example below the slope aspect is towards the east.

    SUN’S MOVEMENT ACROSS THE SITE THROUGHOUT THE YEAR

     

    STEP 1. Locate the property on Google Earth

    Note: These apps use your phone’s GPS and compass to display an accurate representation of the sun’s path through the sky in your location.
    Both apps have 3D augmented-reality camera overlays as well as integrations with Google Maps.

     

    STEP 2. Run the application

    • Open the application and switch to 3D View.

    STEP 3. Check the sun’s movement across the site throughout the year

    • Point your phone towards the sun and look at the plotted sun’s path across the sky.
    • Where does the sun rise and where does it set, are there any obstacles?
    • Pay special attention to the Summer- and Winter Solstices, you’ll also be able to see the sun’s path during these events plotted on the screen.

    Type #1 Risk Assessment:

    Solar access is a priority for any permaculture farm. Variety of microclimates is good but the overall site aspect should allow favorable solar access, generally southern aspects (Northern Hemisphere) and northern aspects (Southern Hemisphere). The second best is SW, SI (NH) or NW, NI (SH), the third best E, fourth W. A northern aspect for Northern Hemisphere and southern for Northern Hemisphere are not preferred and present a type #1 error risk.

    In addition, access to the sun shouldn’t be obstructed by landscape or infrastructure features in any significant way that takes away hours of solar radiation. This is especially important during winter days. Lost hours of sun exposure cannot be substituted by anything so if there is a significant obstruction that leads to decreased solar exposure then avoid the site altogether.

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