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This is an Ignite Style presentation (five minute max presentations with slides that automatically advance every 15 seconds) that was a part of the 2014 Solar Symposium Innovation Showcase. Jon Hillis, Vice President, Prospect Solar Combining Solar with Green Roofs: Find out how Green Roof Integrated PV in urban areas like DC can take advantage of the symbiotic relationship between solar panels and green roof plants, alleviate competition for roof space, and address energy concerns and storm water drainage issues that are prevalent in larger cities.
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Using Solar Energy to Generate Wealth
in Lower Income Communities…
…Solar Garden Roof Systems in the District of
Columbia
CONFIDENTAL; This communication, along with any documents, files or attachments, contains privileged and confidential information. It is meant only for parties authorized by Prospect Solar and Prospect Waterproofing. If you are not an intended recipient, you are hereby notified that dissemination, distribution or copying of any information in or attached to this communication is strictly prohibited. If you have received this in error, please notify the sender immediately and destroy the original communication and its attachments without reading, printing or saving in any manner.
District of Columbia has installed over 2 million square feet of green roofing.
1st among US cities when compared to available roof space.
Additional 2 million square by 2018. Grants and other funding available for
green roof installations.
Green Roofing In DC
30% Federal ITC, SREC market, and new legislation regarding property tax and community solar, make DC an excellent solar market.
Sustainable DC plan includes 20% of renewable energy by 2023, 2.5% coming from solar.
Potential for 19% of electricity generated from rooftop solar PV systems in DC.
Competition for roof space between green roofing and solar.
Solar in DC
Green roof is integrated with solar. Solar racking system is integral with the
drainage/retention layer of the green roofing.
What is a Solar Garden Roof?
Solar installed over green roofing Solar Garden Roof
Solar over green roofing Uses penetrating racking system which is more expensive
(about $0.35/Watt). Reduced life span of roof system compared to ballasted
racking system. Solar panels receive minimal benefit from the micro-climate
the plants create at the roof level.
Solar Garden Roof Soil ballasts the water retention/racking system without
penetrations. Hot rubberized asphalt roof membrane is utilized with life
span 2-3 times that of conventional roofing. Creates a cooler surrounding micro-climate. Modules
operate up to 10% more efficiently.
Installation sequence…
1. Remove insulation and inspect/repair and install HDPE root barrier.2. Reinstall insulation.3. Install moisture retention mat and air layer.4. Install water retention and PV racking modules.
5. Install system filter fabric.6. Install soil and gravel drainage.7. Install plants.
Meet the goals of the Renewable Portfolio Standard.
Increase low-income resident ownership of solar. Majority of low-income residents in DC are not in
living situations where they can own solar at their premises.
Storm water retention requirements creates competition for rooftop space.
Why a Solar Garden Roof? Why Green Roofing? Issues in DC…
Renewable portfolio standard and Solar Renewable Energy Credits (SRECs) market.
Stormwater Retention Credit Trading Program (SRCs) through DDOE.
Community Renewable Energy Act (CREA). Property Assessed Clean Energy (PACE).
DC policy as model for urban areas…
Solar Garden Roof systems installed on…Multi-family dwellingsNon-profit organizationsUniversities and institutionsOffice buildingsGovernment buildings
Opportunities created by policy…
SRECsSRCsPACEThird party ownership and Power Purchase
Agreements (PPAs)
…can be financed using…
…to provide solar ownership for low-income residents through the Community Renewable Energy Act or
Community Solar.
Roof area Solar capacity Energy production Unit cost for green roof components ($/SF) Unit cost for solar ($/watt) Value of SRECs generated Value of SRCs generated Grants available Financing costs Date of installation – SREC pricing will vary
Design variables for financial evaluation…
Roof condition and existing warranty Structural capacity of existing roof deck Wind uplift Shading and orientation for solar array(s) Potential future use of roof area Storm water retention capacity created Financing capacity created
Other design considerations…
Sample project…
System details…
Roof area – 10,000 SF Solar capacity – 51,740 watts Energy production – 63,438 kWh/year Unit cost for green roof components - $20.00/SF Unit cost for solar ($/watt) - $2.80/watt Grants available - $0 Interest rate – 5% Amount to finance - $344,872 Date of installation – 1/01/15 SRC value - $2.27 per SRC (1 SRC/SF/Year estimated to be
generated) Owner is for-profit commercial property
Project parameters…
Estimated project economics…
Net cash flow after 25 years does not take into account energy production after year 25.
$2.27 price per SRC is very speculative as the market is new.
Analysis provided is for a for-profit commercial property owner.
Additional savings if racking system and soil are included in the cost basis to determine federal tax credit.
DDOE/AWS Green Roof Rebate program considerations.
Other considerations…
Solar Garden Roofs should be considered on new development projects in DC.
Should be considered on re-roofing projects as well. Installation of a Solar Garden Roof after completion
of the green roofing greatly increases cost. These retrofits can be cost prohibitive. These systems, funded through SRECs, SRCs, and
PACE, provide an excellent method to bring community solar to low-income residents in the District of Columbia.
Summary
Thank you!
