There has been a nagging question in the back of our minds for quite some time: how much energy can Solar Ivy save a building by providing shade?

Solar Ivy is designed to maximize solar gain on it’s photovoltaic leaves throughout the year.  This is done on every project by adjusting two of the system’s major parameters (leaf spacing and pitch) based on solar orientation.  Since Solar Ivy is designed to capture as much light as possible and will typically be attached to building surfaces, it follows that the system will shade any building surface it is attached to.

Solar Ivy Pitch Range

When reviewed as a shading system, Solar Ivy is closely aligned with some of the basic principals of passive solar design.  It allows a portion of the sun’s energy to hit a building’s envelope in the winter, and provides shade during the summer.  If a system like this is utilized over a window or a glass wall, the energy needed to heat and cool the adjacent interior space can be reduced.  Generally speaking, as the amount of South and West facing glass increases, more effective energy offsets can be achieved using passive solar design strategies (in sunny climates of course).

Some of the larger jobs we have discussed with potential clients involve utilizing Solar Ivy on high rise buildings with glass curtain wall facade systems.  As many readers already know, this type of construction tends to be on the energy intensive end of the spectrum.  One of the major causes of this is similar to the greenhouse effect: sunlight enters the building through it’s glass walls and heats up the building’s interior environment, which can not cool down because of the all glass enclosure (you can read more about this phenomenon here).  Because of this, most glass buildings require air conditioning systems which consume tremendous amounts of electricity providing comfortable interior spaces.

Projects like this bring the question to the fore: how much energy can Solar Ivy save a building by providing shade?  What are the shading offsets relative to the amount of solar power the PV system produces annually?   I set out to answer these questions in a course I enrolled in last semester atPAE: Introduction to Environmental Analysis (thanks and credit due to Professors Rashmi Sonal and Erik Verboon of Buro Happold Engineers).  The course focused on sustainable design methods, and specifically the use of energy modeling and simulation to analyze a building’s energy performance.

The Solar Ivy energy analysis was done in the environmental modeling softwareIES, an emerging industry standard for energy modeling in architecture.  This software takes a number of inputs like building construction and material types, HVAC system type, internal gains (heat from people, lights, computers, etc.), and solar heat gain among many others.  Using these inputs, the program runs an annual energy simulation based on average weather data and building configuration.  In other words, you tell the software how the building is made and used.  It uses historical weather data to simulate the energy needed to keep the building within a comfortable temperature range year round.  By changing a window size or adding a shading device, a designer can analyze how their changes affect the building’s annual energy performance in a simulated environment.

For the Solar Ivy shading analysis, an input model was constructed based on an ideal commercial client’s program: glass curtain wall construction for commercial or institutional use in a sunny climate.  This model was tested in two locations, New York and Dubai, and in each location, three leaf density scenarios were evaluated relative to a base case.

Low, Medium and High Leaf Densities

Solar Ivy Density Range

In every Solar Ivy test case, the building’s AC system required less energy to condition the interior space throughout the year.  The simulation also showed that the amount of electricity saved by shading was greater than the amount of electricity produced by Solar Ivy – usually by a factor of two or three.  This exciting finding has led us to an important conclusion: Shading Matters!

SMIT has the tools to incorporate this knowledge in the design process, which now includes the ability to project Solar Ivy’s total energy offsets for our clients.  Pleasecontact SMIT if you are developing a project that could utilize Solar Ivy as a shading screen, or if you have any questions about this work.

-Ben