War of the Worlds – The Exploding Sun – Part 2

In my previous post we discussed the most common type of solar module utilized today, crystalline silicon panels, which are encapsulated in glass. Another type of rooftop power generation that produces electric energy is Concentrated Solar Power, or CSP. CSP uses lenses or mirrors to concentrate solar thermal energy onto a small area such as a tower. Typically, the mirrors are positioned on the roof to reflect sunlight to the tower mounted on the ground at one end of the building. The tower houses an engine (usually steam), to drive an electric generator.

CSP requires very clear skies to work most effectively, and steam generation requires a fair amount of water which can be an issue in hot, dry climates. Compared to PV, more maintenance may be necessary due to the moving parts in trackers and generators. But focusing the sun in this way also has several advantages.

First, less space is required for the collection units; so less land or rooftop space is required. The cost per watt for CSP is currently par with PV, but has the potential to be half that of PV. CSP steam generators produce AC power so they can integrate directly into existing infrastructure without power inverters. With natural gas back-up or molten salt heat storage systems, CSP has the potential to operate continuously in the event of extended periods of cloudiness or shading of part of the array. CSP is projected to have a larger share of solar power generation within 10 to 15 years due to its efficiencies and potential reduction in cost (and by extension – the ability to generate power more cost effectively) due to technological advancements.

War of the Worlds – The Exploding Sun – Part 1

 

The invasion Orson Wells described so vividly on the radio October 30, 1938, was only sensational because of its time and place in history. What did Wells know about future events that we don’t know? Maybe he foresaw last year’s supernova or exploding star (it was best seen between the big and little dippers September 7-9, 2011), or the growth of solar power generation (photovoltaics = PV) or the implosion of Solyndra. Maybe he foresaw the green movement (little “green” men).

Now that I’ve got your attention, what does this have to do with today’s topic? Other than to introduce a discussion on the power of the sun, not much. Over the next two posts I will discuss photovoltaics (PV), a.k.a. solar power, its history, and the types available.

The most common type of solar module utilized today, crystalline silicon panels, are encapsulated in glass. They make up about 95% of all PV systems installed. Monocrystalline cells invented by Bell Labs in 1954 were cut as wafers from specially grown cylindrical silicon crystals. They are still among the most efficient PV systems, but they have poor tolerance for low light, are fragile and, very expensive, and require very heavy frames for rooftop mounting.

Polycrystalline cells are made from multiple sources and are not as dependent on perfect crystal growth. They are less expensive than monocrystallines, extremely fragile, and less efficient at converting sunlight to electricity.

While some crystalline manufacturers claim higher levels, typical silicone-based PVs have power production between 12 and 18 watts per square foot and operate with 14-20% efficiency. High temperature and shade reduce their output.

Thin-film PV systems don’t use crystalline silicon, but very thin layers of materials such as amorphous silicon, a mixture of copper-indium-gallium-diselenide (CIGS), or cadmium telluride. They can be flexible or rigid and can be adhered to a roof covering or rigid material.

First generation thin-films are mounted on a glass substrate and are relatively inexpensive to produce, but they are about 50% less efficient than monocrystallines. A heavy support frame is required and there have been issues with longevity and durability.

Second generation thin-films are mounted on a flexible substrate. They also do not require crystalline silicon and are easier to manufacture than first generation thin-films at the same cost. There is no requirement for special framing or support structures because they are much lighter than other PV systems. These thin-films are rugged and can often be integrated with modern roofing membranes after they are installed.

Because thin-films are typically surface-mounted, heat gain is an issue and these systems can compromise the benefits of reflective roof systems. Thin-film systems have power production of 5 to 10 watts per square foot and operate with 6-12% efficiency. Compared to crystalline silicon systems, thin-films are more effective in low light situations and are less affected by high temperatures.

In the concluding post I will introduce another type of rooftop power generation that produces electricity from the sun: Concentrated Solar Power, or CSP.

Why Photovoltaic? Why Now?

Photovoltaic (PV) systems have been around for a while now, but the growth of rooftop PV installations has increased dramatically over the past few years. What is causing this surge?

There are many reasons PV systems make sense now and for the future. Energy costs will continue to escalate, and supply will continue to be chased by demand. Expanding the use of renewable energy sources such as PV can help meet some of the demand and relieve some of the cost pressures on electricity.

Rooftops are a good place to locate PV systems because they are typically little used and are free from obstructions that can hamper PV performance. Utilizing rooftops can also reduce land use, making it available for other purposes, or simply as green space.

PV is a clean, unobtrusive energy source, meaning that it does not pollute while it produces energy; eliminating the environmental issues associated with many other forms of electricity generation. The question arises as to whether the net benefits from PV electrical generation outweigh the monetary and environmental costs associated with production, installation, and disposal of a PV system. That analysis has not been done, but it could prove interesting.

Incentives from federal, state, and local governments and from utility companies can ease the financial burden of an investment in PV, plus encourage its introduction and the development of more cost competitive PV technologies. A good source of information on incentives is the Database of State Incentives for Renewables and Efficiency at www.dsireusa.org.

Increased use of PV can help reduce some dependence on foreign sources of fuel, leading to less potential for hardship due to supply disruptions.

 

While improving energy efficiency in buildings is essential (by way of reflective coatings, better insulation, high efficiency windows, day lighting, etc.), it cannot be the only component in pursuing Zero Net Energy Building design. Sources of renewable energy are necessary to supplement conventional sources.

Finally, as the cost of conventional energy sources goes up and availability goes down, the cost of solar electrical production is approaching parity with most conventional sources.

PV systems can be expected to last 20 years or more, so they should be paired with a roof system that doesn’t require much routine maintenance and has a similar lifetime.

Are You Ready for Solar? Integrating Single-Ply Roofing With Photovoltaic Arrays

The growth of rooftop photovoltaics (PV) has exploded over the past few years, aided by incentive programs, technological improvements, and the need for alternative sources of energy. Rooftops can be an excellent place to install PV because they are usually unused and unobstructed spaces. But utilizing a rooftop to locate PV is not without its risks – one of which is the potential to compromise the integrity of a critical component of the building envelope: the waterproof barrier that is the roofing system.

PV and roofing systems that have been effectively integrated will work in harmony to provide clean energy, savings in energy costs, and protect the building and its contents for many years. It is important for a building owner to be aware of all the elements to consider when selecting a roofing system to go under a rooftop PV system. Examples of some issues include foot traffic, roof access for repairs, access for fire fighters, access for HVAC service, excess heat impacts on the roof, weight, snow and seismic loads, fire ratings, wind, hail resistance, drainage, and building codes.

A poorly designed and improperly matched roof system is a candidate for failure, and can lead to damage to a building and its contents and possible premature removal of a PV system for repair and/or replacement of the roof.

The best single-ply roofing systems are those that are able to integrate with virtually any type of PV system and mounting method, and provide years of leak-free performance while the PV system is generating power. You can learn more about what it takes for a roofing system to be “solar-ready” by downloading our “solar-ready” roofing system flyer.

Painting Within the (Green) Lines

“Green,” “environmentally friendly,” “eco-friendly,” and “sustainable” are all buzz words that have become an integral part of the design community. Another used sometimes is “greenwashing.” Greenwashing is when almost any action or product, regardless of its impacts on living beings or the environment, is portrayed as green.

The American Institute of Architects is concerned with Greenwashing, so since January 1, 2009, new or on-going continuing education programs registered with the AIA that have “green,” “sustainable,” or similar words in the title must be pre-approved to be sure the program truly does cover green issues. To qualify for Sustainable Design (SD) credit, at least 75 percent of the program must cover SD issues. Duro-Last® has six programs registered for SD credit.

In response to the expansion of the green movement and the broad claims of environmental responsibility, the Federal Trade Commission recently updated its Guides for the Use of Environmental Marketing Claims, also known as the FTC Green Guides. Here are some general guidelines to follow based on the revised Guides:

Avoid blanket statements like “green,” environmentally friendly,” and “eco-friendly,” because these are difficult or impossible to substantiate. Deceptive statements like, “This product is environmentally preferable,” or the general reference “eco-friendly” should also be avoided because it is unlikely that a marketer can substantiate these claims.

Be careful to qualify claims such as:

“Recyclable” – The FTC follows a three-tiered analysis to evaluate this claim:

1. Substantial majority of consumers have access to recycling facilities

2. Significant percentage of consumers have access to recycling facilities (the statement should be qualified by, for example, adding the text (appropriate for Duro-Last’s recycling program): “when membrane is returned to Duro-Last following the Recycle Your Roof program guidelines.”)

3. Less than significant percentage of consumers have access to recycling facilities (the statement should be qualified with text such as: “this product is only recyclable in specified regions of the U.S.”)

“Free-of…” or “Contains no…” – These claims are often deceptive and have no bearing on a product’s overall environmental impact. Competitors of Duro-Last frequently make claims such as “PVC-Free” or “Chlorine-Free” in their negative marketing. In fact, there is no substantiation that products without PVC or chlorine are better or worse for humans or the environment generally.

Made with Renewable Energy or Materials – Statements like this should always be qualified if the entire product/system is not made with renewable energy or materials.

Carbon Offsets – Scientific evidence should support any claims regarding carbon offsets or emission.

The “green” approach to building design and construction will continue to spread, and it’s important for consumers to understand which green claims are “within the lines,” and which really should be washed away.

Yet Another Green Design Tool

Many are at least somewhat familiar with green design programs such as LEED® and Green Globes. The ENERGY STAR® Roof Products Program and the Cool Roof Ratings Council have been providing lists of qualified or rated products for years now, however, recently there have been some questions about another design guide and what it has to say about cool roofing.

The Advanced Energy Design Guides were developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). The guides are a series of publications designed to provide recommendations for achieving energy savings above and beyond the minimum code requirements of ANSI/ASHRAE/IESNA Standard 90.1-1999. They are intended for contractors and designers of small buildings and provide a simple approach to achieve energy savings without utilizing complex calculations or analysis.

The guides give general recommendations in the Building Envelope sections stating that cool or “solar reflective” roofs help reduce energy usage. They do not offer the specificity of LEED or Green Globes, rather they make general recommendations like “increase roof surface reflectance and emittance.”

They also provide useful charts and climate maps that indicate relative performance of various types of roofing products and areas of the country that may benefit most from cool roofing systems.

The Advanced Energy Design Guides are available as free downloads from www.ashrae.org/aedg. Highly reflective white membranes, such as what’s used in the Duro-Last® Cool Zone® roofing system offer a great opportunity for owners of small buildings to achieve real energy savings.

No News Is No News

Good news for home owners! The Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 extended the residential energy efficiency tax credits.

The bill allows a tax credit for up to 10% of the amount paid by the taxpayer for qualified nonbusiness energy efficiency improvements to a maximum lifetime limit of $500. If more than $500 of these tax credits were already taken between 2006 and 2010, there can be no further credits taken. This is a reduction from the $1,500 credit allowed in the original bill.

The credit applies to principal residential property placed in service between January 1, 2011 and December 31, 2011.

Among the qualifying improvements are windows and doors, metal and asphalt roofing, insulation, HVAC equipment, water heaters, geothermal heat pumps, and solar energy systems. All must be ENERGY STAR® qualified products. Unfortunately, single-ply membranes, such as the Duro-Last® Cool Zone® roofing system still do not qualify for the residential energy efficiency tax credit. However tax policy and incentive programs are constantly being revised. We’ll stay on top of things and report on changes when they occur.

Pilot Held Hostage by Rogue Roofing Manufacturer!

A year and a half ago the U.S. Green Building Council initiated a new program to allow for the testing of potential new LEED® credits. Titled “LEED Pilot Credit Library,” this collection of pilot credits allows project teams to test potential new credits and work with the USGBC to develop future LEED credits and categories.

Pilot Credit 2: PBT Source Reduction: Dioxins and Halogenated Organic Compounds has been greatly misunderstood and misrepresented by some roofing manufacturers. Some of them have used this credit as a negative promotional tool by misrepresenting the purpose and content of the credit. To receive a point for this credit, the submitter must do the necessary research and provide the results and documentation to USGBC. The research could either support or reject the intent of the credit.

In this credit, it is required that for each alternative product, the submitter must “…conduct and submit a multi-parameter alternative product analysis that includes at a minimum one (1) other product that serves the same function.” The study must also “…include at least 4 parameters (in addition to absence of halogenated materials) associated with the products manufacture or service life . . . used to assess suitability of the product selected.” So the research done must be very extensive and supported with empirical data.

Recent information shows that of the fifty or more submissions for this credit, all have been rejected. The main reason is that no supporting documentation or studies were done to suggest awarding a point either for or against the use of halogenated products (PVC being one). If a credit were to be awarded, it would be through the Innovation category of LEED, not for “non-use” of PVC. If it is determined that there is enough interest and data to consider adding a new credit category, then it would still be necessary to go through the typical public review process prior to being established.

The LEED process for approving new credits is extensive and (hopefully) transparent. By being armed with the facts and understanding how the process works, no one should be able to storm the flight deck and take over the plane.

PTOs: New to the Roofing Market?

Be careful what you read! Are PTOs a new competitor in the roofing market? No, it’s an acronym with some misplaced letters from the title of a poorly written magazine article. So much marketing misinformation gets presented as fact that it’s a wonder anyone can make an informed roofing decision. Following is some information that may help in assessing the credibility of statements made about roofing.

PVC roofing is made from two basic components: fossil fuel and salt. Fossil fuel is converted to ethylene and rock salt goes through electrolysis to retrieve chlorine – one of the most abundant elements on earth. These components are combined to produce the vinyl chloride monomer which is used with other components to create PVC membrane.

Europe was early to adopt PVC roofing as a single-ply system of choice. Contrary to some claims, PVC roofing is being sold throughout Europe and in fact enjoys by far the largest market share of any of the thermoplastic single-plies.

ENERGY STAR®, the Cool Roof Rating Council, Green Globes, and the U.S. Green Building Council, among other organizations, have developed programs to help specifiers and consumers make informed roofing decisions. The USGBC developed the Leadership in Energy and Environmental Design (LEED®) Rating System several years ago. LEED aids in the design and construction of buildings that minimize negative impacts on occupants and the environment

PVC membranes offer a host of relevant benefits:

  • White PVC membranes are among the most reflective on the market. The Duro-Last Cool Zone® membrane’s Solar Reflectance Index (SRI) of over 110 exceeds LEED requirements for Sustainable Sites Credit 7.2.
  • Recyclability is also a key element of many green design programs, and unlike other roofing materials, there are well-established programs for recycling PVC roofing membrane, including one offered by Duro-Last.
  • Because of its chlorine component, PVC is inherently flame resistant, unlike many other roofing products with higher carbon content. This makes fire ratings easier to achieve, and means that PVC roofing in general is less likely to emit toxic gases than other materials in building fires.
  • PVC membranes are highly flexible and can be custom-prefabricated before reaching the rooftop for installation. This reduces rooftop labor by minimizing jobsite welding by contractors. In addition, seam integrity is more reliable than for stiffer membranes that are made from materials other than PVC.

So, when evaluating systems for your next commercial roofing project, you may want to ask yourself “Why go with the PTO?” Check the facts; don’t be misled by misinformation, and make an informed decision.

Flooded With Sunlight: Reducing Urban Heat Islands with Cool Roofing

U.S. Department of Energy Secretary Steven Chu is a big proponent of cool roofing. In his July 2010 announcement, Chu made it clear that he was going to push for the installation of cool roofing systems on all federal buildings to help reduce energy usage. Secretary Chu is well-informed about cool roofing because he was formerly the head of Lawrence Berkeley National Laboratories (LBNL), the entity that pioneered the study of Urban Heat Islands (UHIs).

Not only will cool roofing reduce building energy usage, it will also help mitigate the UHI effect. The UHI effect is the tendency for urban areas to be hotter than surrounding areas. LBNL found that the average temperature on a hot summer day will be seven degrees warmer in North American urban areas than surrounding rural areas. During an extended heat wave the difference can be even more pronounced. Studies have shown that there are three primary factors that cause the majority of the UHI effect.

Vegetation

The first factor is that urban areas have less vegetation than rural areas. Not only do trees and shrubs provide shade, but thriving vegetation keeps itself cool through a process called evapotranspiration. Similar to how the human body sweats to keep itself cool, vegetation releases moisture to stay cool. About 56%, or almost four degrees, of the seven degree difference is due to less vegetation in urban areas than rural.

Dark Pavement

Many might think that dark pavement would account for much of the UHI effect. While walking down a city street, one can feel the heat radiating up. But dark pavement accounts for only 6%, or less than one-half degree, of the seven degree difference.

Dark Roofing

Roofing takes up a lot of surface area in urban areas, but roofing is not often considered a source of urban heat because it is “out of sight, out of mind.” Yet dark roofing accounts for 38%, or almost three degrees, of the seven degree difference associated with UHIs.

Many cities have attempted to increase green space and vegetation through civic programs and building codes, but for every tree planted or park developed there is much more green space that succumbs to urban sprawl. Green space initiatives are at best a long term means of mitigating UHIs and can entail significant expense.

Paving products made from lighter colored materials are available, but implementing these measures is capital intensive and can take years to accomplish. And considering the relatively minor role that paving plays in UHIs, there are options that provide more bang for the buck.

Installation of cool roofing during initial construction or when re-roofing offers immediate benefits, not only toward mitigation of UHIs but to the building owner in the form of energy savings. A good roofing system is essential for protecting any building from the elements. Selecting and installing a cool roofing system is easy to accomplish, inexpensive relative to other UHI mitigation efforts, and provides benefits immediately.

Even in northern geographic areas where net energy savings may be minimal, cool roofing systems offer significant benefits that may be less tangible but are essential to the long term performance and durability of the roof, insulation and HVAC equipment.