Solar Power World heard about Green Roof Technology’s Sun-Root System, and we reached out to Ryan Miller, director of the company’s Baltimore office. He was kind enough to answer the Solar Power World 4 questions:
SPW: What is the concept behind the Sun-Root System?
Miller: As a green-roof company for more than 30 years, we have seen many innovations to modern green roof technology that makes it more marketable and affordable. When you sit down with clients, they want to know how much they are spending and what is their return. The payback of a green roof lies somewhere between 15 years to 25 years in most cases, and for many building owners that is not something that excites them. So we looked for ways to shorten this payback period while still meeting our goal of increasing the world’s green spaces.
This is where the idea of combining renewable energy and green roofs came into play. With rising energy costs and increasing federal and state incentives for solar panels, we now have a vehicle to show a client that you can make your money back in as little as three years. We can show them that you will save X amount on your energy bill and X amount on your up-front costs. We show them these numbers then say, “Oh yeah, let’s not forget about the green roof that reduces your stormwater footprint, increases your buildings efficiency and doubles or even triples the lifetime of your roof membrane.”
SPW: You have an unusual product in the Sun-Root System. Is it difficult to install?
Miller: The Sun-Root System is simple to install with some basic knowledge of green roofing. Because each Sun-Root module weighs less than 5 pounds, they are easy to handle and maneuver. Modules are placed on top of a protection fabric and then properly orientated. Once in place, a capillary fabric is laid on top of each module and covered with an engineered soil (i.e. the growing media) that provides the ballast for the entire system. Each Sun-Root module is connected to the next by a dual horizontal photovoltaic panel-racking bar. With the racking bars in place, the solar panels are mounted as you would for any traditional solar array. Once the modules are secured, you are ready to plant the vegetation, which is the icing on the cake.
SPW: How many installations do you have at this time and how many are in the pipeline?
RM: Currently in the United States, there is one project installed at the 5-Boro’s Building on Randall’s Island in New York. Four more larger scale projects are in the pipeline for 2013. Since the Sun-Root System’s development five years ago in Germany, it has been installed on over 150000 sq. ft. of roof space. We believe the U.S. market will generate more projects as the incentives and tax credits are greater. Germany also compares to Alaska in terms of sun exposure, so most of the United States has more sunlight to offer than Germany.
SPW: This solution you’ve come up with seems so logical — a natural fit, if you’ll excuse the pun. Why hasn’t anyone come up with something like this before?
RM: This idea of combining PVs with green roofs has been around since modern green-roof technology was developed 30 years ago in Germany. We have numerous pictures in our archives that demonstrate the myriad ways people have tried to integrate modules and green roofs. In the end, for more 25 years, PV racking arrays were simply installed above an extensive green roof with no integration.
Not until Optigrün AG put the time and money into R&D did a fully integrated solar green-roof materialize. The result was the Sun-Root System. It is the only solar green-roof system to integrate the mounting module directly into the drainage layer of the green roof. The module is engineered to promote evapotranspiration, in which the water stored in the green roof is released through evaporation, which cools the solar panels.
The final outcome is a solar green-roof system that supports healthy vegetation and strong enough to hold solar panels by using the weight of the green roof. The added benefit of a 10% increase in energy output, because we keep the panels cooler during the day, was just a bonus.
Check out this video explaining out the Sun-Root System works: