Greens on the Roof - by Doug Mohney

Views and Opinions on Green IT (Aug 5 2010)

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   If you didn't have enough to think about between putting solar panels or a "traditional" green roof of plants,  the latest Big Ideas are to actually grow vegetables and other edibles on top of buildings and to mix and match vegetation and solar panels for better power performance.

   Traditional green roofs use plants to soak up sunlight and water, reducing power costs for cooling and cutting down on stormwater runoff.   Sky Vegetables (www.skyvegetables.com) puts into place a full sustainable hydroponic farm on urban rooftops, touting such benefits as reduced utility and sewer costs (the whole wastewater thing again), insulation in the winter,  reduction of both greenhouse gases and fossil fuel use, and income through the sale of chemical free, locally grown produce.

   A Sky Vegetables setup includes a wind turbine and solar panels to generate power,  a composting section to decompose waste plant material (and expired supermarket produce) , and rainwater harvesters to provide water for the growing system.   Sky estimates its hydroponics system to grow plans use about five to 10 percent of the water of traditional agriculural systems; not having to move around all that water has energy benefits as well.

   Pitching to supermarkets and building owners with underutilized space in urban areas, Sky's concept is more resource-intensive and complicated than a traditional green roof  -- someone has to go to the roof to plant, monitor, and harvest -- but it offers the benefits of locally-grown produce (fresher,  less carbon) and a revenue stream. In colder climates, dumping waste heat into greenhouses is a common practice so it's not a stretch to see bytes aiding the growth of tasty bites.

   Over at Portland State University (PSU), researchers are looking at the mash-up of green roofs and solar panels.  Solar panels, like other types of electronics, operate more efficiently when cooler.  The combination of rainwater retention and non-black service offers a cooler microclimate for the solar panels while the solar panels offer shade to growing plant life. PSU is running a multi-year study for its "eco-roof" but initial results are promising, with solar panels delivering near-optimum power.   

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