Why do we have a NEWS page?
This blog is intended to provide educational resources as well as information about our green community, Clark Hill Woods, in New Boston, New Hampshire. We will, from time to time, post research and/or news articles that we think might be of interest to visitors, especially those of you who are as excited as we are about alternative energy technologies, new incentives/sustainability and energy-saving rating systems, etc., that could save hundreds or thousands of dollars for home buyers and homeowners while also helping significantly to slow climate change. Some of these technologies, incentives and/or rating systems may already be in place; others may be under development. Check back often to see what’s new!
We welcome feedback on these and all other posts on our blog.
Now’s the Time to Install Solar
Solar tax credits are due to be in place until 2016, but they could end well before then
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All of the houses at Cobb Hill CoHousing in Hartland, Vermont have solar hot water collectors on the roofs.
This summer is a great time to get a good deal on a solar water heating or solar-electric (photovoltaic) system for your home. While I argued a few months ago in this column that the 30% federal solar tax credit has some flaws–key among them being that it’s based on the dollar value rather than performance and that there’s no cap on the cost of the system (and credit you can earn)–these aren’t reasons not to take advantage of it.
While the solar tax credits are scheduled to be in place until 2016, I won’t be at all surprised to see them scaled back or eliminated well before then. If you haven’t noticed, the political pendulum is swinging, and incumbents who supported the stimulus funding are now being cast as reckless spenders and are losing primaries. I think we’ll see a growing focus on deficit control–and that could well include scaling back on incentives like the solar tax credits. The bottom line is that now’s the time to benefit from the solar tax credit.
For most homeowners, installing a solar water heating system will have a more rapid return on investment (ROI) than installing an electricity-generating photovoltaic (PV) system, so I’ll focus on the former. Most solar water heating systems for typical homes have two flat-plate solar collectors. Either water or an antifreeze solution is pumped through the collectors during the day and heat is transferred from the absorber plate to that fluid. A glass cover plate on the collector, insulation behind the absorber plate, and pipe insulation all help to improve efficiency and direct more heat into the circulating fluid.
While the collectors sit on your roof (or on a separate rack outside the house), there are also solar water heating components inside the house. Most systems have a separate solar hot water storage tank in the basement or utility room that serves as a preheater for the standard water heater. A heat exchanger in this tank transfers heat from the fluid circulating through the collectors into the storage tank. Rather than a preheater tank, some systems have a single tank containing both the heat exchanger from the solar collectors and a standard heating element.
Controls and a pump round out the system. The conventional approach is to have a differential thermostat that senses temperatures both in the collectors and storage tank, and then switches on the circulator pump when the collectors are warmer than the water in the storage tank. Some systems, however, now use a simpler control system: a separate PV module powers the circulating pump, operating only when the sun is shining.
Solar water heating systems vary a great deal in their cost, depending on the size, type of system, added features like digital monitoring, and challenges of the installation. The typical price range for a residential system is $5,000 to $8,000, installed. With new construction, costs can be lower, especially if a lot of identical systems are being installed on multiple tract homes.
To function efficiently, solar panels must be installed on a good site. The sun traverses the southern sky during the day, rising in the east and setting in the west, so the best site for solar is a south-facing roof. The pitch of the roof isn’t critical. A steeper pitch will be a little better in the winter (when the sun is lower in the sky), while a shallower pitch is better in the summer (when the sun is higher in the sky), but most standard roof pitches will work all right. There should be as few obstructions as possible, so cutting or pruning nearby trees is often an important part of a solar installation.
A properly sized and well-sited solar water heating system should satisfy most of your hot water needs during the summer months, but it may provide less than half in the winter, when there is less sunlight. To maximize the percent of hot water provided by the solar system, you should carry out appropriate water conservation efforts, such as installing low-flow showerheads and washing laundry in cold water.
Contact a local or regional solar installer for more information and to schedule a site visit. Be sure the contractor you pick is more interested in a quality, reasonably priced installation than on maximizing the tax credit. (Be aware of scams in which roofing or other costs unrelated to the solar system are added into the installation price so that Uncle Sam will pay you more–an indicator that the contractor’s motivations are misplaced.)
I invite you to share comments on this blog.
- Alex Wilson
ANSI Approves National Association of Home Builders’ (NAHB’s) Green Building Standard
March 17, 2009
By Martin Holladay (from GreenSource, The Magazine of Sustainable Design)
The National Association of Home Builders (NAHB) and the International Code Council (ICC) have successfully shepherded a residential green building standard through the American National Standards Institute (ANSI) approval process. Known as both the National Green Building Standard and ICC-700, the standard was approved in January 2009.
ICC-700 has four compliance levels: bronze, silver, gold, and emerald. The mandatory measures in the standard largely correspond to minimum code requirements. Beyond these measures, builders must accrue points by incorporating features in six areas: site development, water conservation, energy conservation, resource conservation, indoor air quality, and homeowner education. Houses over 4,000 ft2 will need more points for a given certification level than smaller houses.
For bronze certification, a home must be designed to use 15% less energy than a home that minimally complies with the 2006 International Energy Conservation Code (IECC). To reach the emerald level, a home must achieve a 65% reduction in projected energy use. In addition, all houses must include a mechanical ventilation system complying with ASHRAE Standard 62.2. Although energy compliance depends strongly on climate zone, most ICC-700 checklist points (including water-saving measures) apply nationwide. A few, however, are regionally specific, such as those related to termites, radon, and annual rainfall.
NAHB will continue to support builders who choose to rate homes using the less stringent 2005 Guidelines. For builders seeking a higher standard, the NAHB Research Center has established a process to certify projects under the new ICC-700. The first step is for builders to use NAHB’s free online scoring tool (www.nahbgreen.org/ScoringTool.aspx). “The scoring tool sets us apart from our competition,” explained NAHB division director Vladimir Kochkin. “It simplifies implementation.” Builders can use the tool to obtain a preliminary score for their design. If they decide to certify, they submit an application to a third-party verifier, who performs both a rough-in and final onsite inspection.
NAHB charges builders $500 per project for certification; the fee drops to $200 for NAHB members. In addition to the certification fee, builders will need to pay for verification by an independent party, including the cost of site visits.
Since the ICC-700 standard is brand new, it will take a while for energy consultants to determine whether the standard is more or less stringent than LEED for Homes. “My opinion right now, subject to confirmation from additional study, is that the basic ICC-700 standard house will be very close to a LEED for Homes certified house,” said Bion Howard, an energy consultant based in California. LEED takes a tougher line on certain divisive issues, however, such as certification of tropical woods. According to Carr, “Compared to LEED for Homes, I think builders will find that NAHB’s green building standard is more flexible and usually less expensive to meet,” both in added construction and certification costs.
When comparing the new standard with the old NAHB Guidelines, NAHB representatives are unequivocal. “The Standard is more stringent than the Guidelines,” said Carr. “The bar has been raised.” Kochkin expanded, saying, “The new bronze corresponds more or less to the silver level in the Guidelines.”
Opinions differ on whether having three rating systems for new single-family homes—the 2005 NAHB Guidelines, the ICC-700 standard, and LEED for Homes—is confusing to builders. Howard argues that the standard could serve to harmonize the various systems. “I think the standard provides an agreed-upon floor upon which guidelines with a higher environmental purpose can be based,” he said.
Brendan Owens, the vice president of LEED technical development at USGBC, sees no urgent need for harmonization between two systems trying to accomplish different things. “We try to create rating systems that are leadership standards. We are working to create a mechanism that recognizes high-performance green building,” he said. Owens did note that USGBC’s work with the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) on Standard 189, a code-ready commercial green building standard that may become a prerequisite for LEED, could provide a model for a link between NAHB’s new standard and LEED for Homes. No negotiations with NAHB are underway, however.
Although he calls NAHB’s standard “light green,” Howard is encouraged by a shift in NAHB’s approach to standard development. “Five years ago, I was seeing some disturbing patterns,” said Howard. “Whenever there was any talk of developing a new standard, NAHB tended to be the 800-pound gorilla that dragged its feet all the time.” With ICC-700, Howard said, “NAHB appears to have made a decision to put together a reasonable standard and push it through the ANSI process.”
This article originally appeared on BuildingGreen.com
EPA, Dept. of Energy Announce New Steps to Strengthen ENERGY STAR
March 19, 2010
The U.S. Environmental Protection Agency and the U.S. Department of Energy today outlined a series of steps to further strengthen the trusted ENERGY STAR® program. This action comes at a critical time for American consumers, many of whom struggle to keep up with their monthly energy bills. In addition to third-party testing already underway, EPA and DOE have launched a new two-step process to expand testing of ENERGY STAR qualified products. This week, DOE began testing of some of the most commonly used appliances, which account for more than 25% of a household’s energy bill, and both agencies are now developing a system to test all products that earn the ENERGY STAR label. The steps are part of an overall effort by the Obama Administration to improve the energy efficiency of homes and appliances to save families money.
“Energy efficiency is more important than ever to American families,” Gina McCarthy, EPA Assistant Administrator for Air and Radiation said. “As our economy gets back on its feet, ENERGY STAR is an easy way for consumers to save money and help fight climate change.”
“Consumers have long trusted the ENERGY STAR brand for products that will save them energy and save them money,” said Cathy Zoi, DOE Assistant Secretary for Energy Efficiency and Renewable Energy. “The steps we’re taking now will further strengthen and improve the program, building on the results that consumers have come to expect.”
Alternative Energy Research – SOLARFebruary 16th, 2010
Flexible Solar Cell Research at Caltech may have promising future applications
PASADENA, Calif.—Using arrays of long, thin silicon wires embedded in a polymer substrate, a team of scientists from the California Institute of Technology (Caltech) has created a new type of flexible solar cell that enhances the absorption of sunlight and efficiently converts its photons into electrons. The solar cell does all this using only a fraction of the expensive semiconductor materials required by conventional solar cells.
“These solar cells have, for the first time, surpassed the conventional light-trapping limit for absorbing materials,” says Harry Atwater, Howard Hughes Professor, professor of applied physics and materials science, and director of Caltech’s Resnick Institute, which focuses on sustainability research.
The light-trapping limit of a material refers to how much sunlight it is able to absorb. The silicon-wire arrays absorb up to 96 percent of incident sunlight at a single wavelength and 85 percent of total collectible sunlight. “We’ve surpassed previous optical microstructures developed to trap light,” he says.
Atwater and his colleagues—including Nathan Lewis, the George L. Argyros Professor and professor of chemistry at Caltech, and graduate student Michael Kelzenberg—assessed the performance of these arrays in a paper appearing in the February 14 advance online edition of the journal Nature Materials.
Atwater notes that the solar cells’ enhanced absorption is “useful absorption.”
“Many materials can absorb light quite well but not generate electricity—like, for instance, black paint,” he explains. “What’s most important in a solar cell is whether that absorption leads to the creation of charge carriers.”
The silicon wire arrays created by Atwater and his colleagues are able to convert between 90 and 100 percent of the photons they absorb into electrons—in technical terms, the wires have a near-perfect internal quantum efficiency. “High absorption plus good conversion makes for a high-quality solar cell,” says Atwater. “It’s an important advance.”
The key to the success of these solar cells is their silicon wires, each of which, says Atwater, “is independently a high-efficiency, high-quality solar cell.” When brought together in an array, however, they’re even more effective, because they interact to increase the cell’s ability to absorb light.
“Light comes into each wire, and a portion is absorbed and another portion scatters. The collective scattering interactions between the wires make the array very absorbing,” he says.
This is a schematic diagram of the light-trapping elements used to optimize absorption within a polymer-embedded silicon wire array. [Credit: Caltech/Michael Kelzenberg]
This effect occurs despite the sparseness of the wires in the array—they cover only between 2 and 10 percent of the cell’s surface area.
“When we first considered silicon wire-array solar cells, we assumed that sunlight would be wasted on the space between wires,” explains Kelzenberg. “So our initial plan was to grow the wires as close together as possible. But when we started quantifying their absorption, we realized that more light could be absorbed than predicted by the wire-packing fraction alone. By developing light-trapping techniques for relatively sparse wire arrays, not only did we achieve suitable absorption, we also demonstrated effective optical concentration—an exciting prospect for further enhancing the efficiency of silicon-wire-array solar cells.”
Each wire measures between 30 and 100 microns in length and only 1 micron in diameter. “The entire thickness of the array is the length of the wire,” notes Atwater. “But in terms of area or volume, just 2 percent of it is silicon, and 98 percent is polymer.”
In other words, while these arrays have the thickness of a conventional crystalline solar cell, their volume is equivalent to that of a two-micron-thick film.
Since the silicon material is an expensive component of a conventional solar cell, a cell that requires just one-fiftieth of the amount of this semiconductor will be much cheaper to produce.
The composite nature of these solar cells, Atwater adds, means that they are also flexible. “Having these be complete flexible sheets of material ends up being important,” he says, “because flexible thin films can be manufactured in a roll-to-roll process, an inherently lower-cost process than one that involves brittle wafers, like those used to make conventional solar cells.”
Atwater, Lewis, and their colleagues had earlier demonstrated that it was possible to create these innovative solar cells. “They were visually striking,” says Atwater. “But it wasn’t until now that we could show that they are both highly efficient at carrier collection and highly absorbing.”
The next steps, Atwater says, are to increase the operating voltage and the overall size of the solar cell. “The structures we’ve made are square centimeters in size,” he explains. “We’re now scaling up to make cells that will be hundreds of square centimeters—the size of a normal cell.”
Atwater says that the team is already “on its way” to showing that large-area cells work just as well as these smaller versions.
In addition to Atwater, Lewis, and Kelzenberg, the all-Caltech coauthors on the Nature Materials paper, “Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications,” are postdoctoral scholars Shannon Boettcher and Joshua Spurgeon; undergraduate student Jan Petykiewicz; and graduate students Daniel Turner-Evans, Morgan Putnam, Emily Warren, and Ryan Briggs.
Their research was supported by BP and the Energy Frontier Research Center program of the Department of Energy, and made use of facilities supported by the Center for Science and Engineering of Materials, a National Science Foundation Materials Research Science and Engineering Center at Caltech. In addition, Boettcher received fellowship support from the Kavli Nanoscience Institute at Caltech.
Contact: Lori Oliwenstein (626) 395-3631 email@example.com