SUN ANGLES - HARVESTING + VIEWS + DAYLIGHT

Light/Air/Water

Written by R. Kirk Johnson, AIA, LEED AP

The natural environment provides numerous opportunities to harness energy from sources such as the sun, earth, water, vegetation, or wind.  Effectively incorporating these same natural resource elements provide advantages for the built environment by enabling views, cooling, heating, refreshment, and a sense of place.  This is particularly the case with tapping resources from the sun as it provides buildings with the opportunity to generate power, provide shading, and harness daylighting into buildings from the sun.  This short article delineates three particular perspectives relating to the solar elements, by discussing sun power capture, direct sunlight restriction, and daylighting focus opportunities in sustainable design and construction.

CAPTURE

Harvesting energy resources from the sun occurs all throughout the natural environment with vegetation.  However, it has only been in the most recent decade, that the opportunity to effectually generate power from sunlight into our buildings has started to become much more commonplace and acceptable.  This simple concept, particularly with the advent of the LEED Rating System, has emerged to the forefront the feasibility and concepts of generating power from natural sources.

At a conceptual level, solar energy utilizes the installation of photovoltaic cells, panels, modules, and arrays that harness sunlight energy and converts it directly into electricity.  This power in turn is converted from direct current to alternating current power required in buildings and infrastructure.  The generated electricity can be connected directly to the utility power grid, independently stored in a self-contained battery array system, or a combination of the two methodologies.

Photovoltaics are currently available in several varieties such as crystalline, polycrystalline, or thin-film technologies that have been used in elements ranging from solar powered calculators to building integrated photovoltaic (BIPV) systems.  According to the U.S. Department of Energy (DOE) in their Renewable Energy Data Book dated September 2008, solar energy capacity has more than doubled between 2000 and 2007.  However, in spite of the accelerated growth, solar still represents a small percentage of overall U.S. electricity generation.

BIPV systems have become much more mainstream in sustainable construction as many more manufacturers are making additional products and the efficiencies of these products have residually increased.  This in turn provides greater product availability and costing for the technologies thus impacting implementation.  Currently, however, the efficiencies of photovoltaic systems, especially when compared to the economics involved have limited adoption of the systems into more buildings.  Large scale acceptance of these systems requires considerable more reductions in costing and sizeable increases in solar panel system efficiency.  Presently, these systems are comparatively inefficient as a high performance PV panel is approximately 18%-20% efficient.  Additionally, the payback without governmental or utility incentives is usually cost prohibitive to use in a large scale on building projects.

DESIGN OPPORTUNITIES

The essence of a building integrated photovoltaic system is to incorporate power generating devices into common building envelope elements.  These design opportunities can range from roof panels, to curtain wall panels, to vision glass, or shading devices.  It is really up to the design integrity of the individual projects.  A large majority of award winning sustainable design structures have incorporated building integrated photovoltaic systems at some level.  However, some possible opportunities for consideration in the integration of building integrated photovoltaic panels are listed below.

• Roofs
• Walls
• Curtain Wall
• Glazing
• Facades
• Building Sunscreen Systems
• Skylights
• Clerestories
• Covered Parking
• Roof Overhangs
• Trellis Systems
• Awnings
• Light Shelves
• Metal Roofing (clipped to roof)
• Ground Mounted
• Light Poles
• Fences and Screens
• Rain Water Collection Structures
• Signage
• Rainscreens
• Canopies and Shading Devices

The implementation of renewable photovoltaic systems will become much more paramount in the future as a considerable degree of attention is emerging in the next generation of energy codes and regulations, such as Standard 189 or ASHRAE 90.1-2010, which both have a stated goal of 25%-30% energy reduction goal from the 90.1-2004 version of the regulation.  They will continue to evolve as building code regulations begin to require net zero buildings shortly thereafter.  The 2030 Challenge mandates buildings be carbon neutral in 2030 and ASHRAE is currently working on the regulations to make the challenge doable by providing energy conservation regulations that can help meet the requirements in the year 2015.

RESTRICTION

Gleaning energy resources from the sun is definitely an added benefit in optimizing energy conservation practices.   However, the incorporation of solar activity in a building brings secondary concerns that must be addressed for occupants within a facility.  While concentrating solar rays directly to photovoltaic panels may be required for operational energy efficiencies, focusing the sun path directly inside of a building is typically undesirable.  Reducing glare from window systems and shading the sun rays from the interior of the building produce more pleasant spaces for occupants.

Some traditional approaches to reducing building cooling loading by shading can be implemented simply from strategically orienting the building to an optimal direction.  The simple concept of providing buildings, trees, facades, or other components to provide additional shading and shelter has been proven throughout centuries as an effective manner of implementing energy conservation components.  Additional measures of filtering sunlight include the use of external sunscreens, internal light shelves, internal sunscreens, fritted glass, and similar methods of restricting glare.

The climate in the North Texas region requires considerable more cooling days than heating days.  A well-balanced occupied interior environment utilizes views direct to the exterior that are filtered from harsh direct sunlight and residually reduce cooling levels within the building.  Exploring options to provide an appropriate balance with light, air, and view determine the success of the interior design environment.  Restricting the direct sunlight provides many positive attributes within the built environment.

DAYLIGHTING FOCUS

Perhaps one of the most apparent opportunities to harness sunlight besides the generation of electricity is the harvesting of the sunlight for interior lighting purposes.  The use of daylighting in buildings has historically been incorporated in designs throughout the centuries, yet today we have the added benefit of providing additional sophistication with available technological controls to further enhance the interior built environment.  As a result, buildings should consider ways to passively and actively incorporate daylighting strategies deep into the interior core providing better spaces for occupants.  A side benefit of this strategy is a significantly reduced lighting power density level and reduced energy consumption levels.

Some passive building strategies to increasing interior daylighting within buildings include increasing vertical floor-to-floor heights, infusing more glazing system into the building, providing light wells, incorporating courtyards, including skylights or other toplighting strategies, and minimizing the exterior wall to core depth ratio.  Some active systems can be provided simply by adding photocell sensors to the exterior perimeter zones, switching the perimeter zone lighting areas to synchronize with the daylighting strategies, providing occupancy sensors, and providing time based technological sensor controls.

By incorporating daylighting strategies into buildings and tying this to technological controls, significant energy conservation gains may be made.  Projects pursuing LEED Certification will also receive the added benefit of synergistic credits effecting energy optimization, daylighting, and views.

LIFE CYCLE ANALYSIS

Employing all three strategies of power generation, sunlight restriction, and daylight harvesting should be looked at from first time costing metric, return on investment, and life cycle costing perspectives.  A long term life cycle approach has been considered as a compliance alternative for future LEED credits.  The overall costing exercise should include investigating various financial incentives provided by utility companies and governmental agencies, particularly with the usage of solar and energy improvement technologies.

Given the fact that the next generation of energy conservation standards is designed to be approximately 30% more efficient than preceding versions and that employing these three readily available sunlight strategies assist in meeting these mandates, it is recommended that buildings develop specific energy reduction goals at the earliest outset of a project.  This enables greater clarity and opportunity for projects and provides a benchmark to meet.  We must begin to look deeper into these areas and explore options that positively influence energy reduction opportunities rather than attempting to solely measure the outcome of inefficient buildings made independent of proactive analysis.  Additionally, manufacturing research and design must develop greater efficiencies in panel technologies to impact widespread adoption.

FINANCIAL INCENTIVES

Various financial incentives or rebates are available for those projects that implement building integrated photovoltaic systems or additional energy improvement measures.  These incentives are provided by utility companies and governmental programs at federal or state levels.

GOVERNMENTAL INCENTIVES

• MACRS (Modified Accelerated Cost-Recovery System + Bonus)
• Federal Stimulus Act of 2008 (26 USC:168(K))
• The American Recovery + Reinvestment Act of 2009
• Federal Energy Policy Act of 2005 + Energy Improvement & Extension Act of 2008
• Corporate Tax Credit (26 USC & 48) American Recovery + Reinvestment Act of 2009
• Renewable Energy Grants- American Recovery Reinvestment Act of 2009

UTILITY INCENTIVES

• Oncor Utility Delivery- Solar Photovoltaic Incentive Program

SUN ANGLES

Incorporating sunlight power harvesting, opening view corridors within the building to the exterior environment, and introducing daylight strategies into facilities optimize energy conservation opportunities and potential LEED Certification levels.  As sustainable design and construction accelerates, these opportunities should be explored as design options for buildings.