Ask the Expert
Steven Strong responded to viewer questions and comments about solar technology and the prospects for solar energy on May 1, 2007. Please note we are no longer accepting questions, but see our links and books section for additional information. You can also join the discussion.
Q: If I wanted to build an
energy-efficient, active and passive solar home, how would I get started?
A: First, you need to locate a piece of land that has good solar access. I am familiar with Highlands Ranch. The area has great solar potential. In addition, Colorado has a good solar access policy. Next, do you intend to retain an architect? If so, this is the most important decision you will make. You really want to seek out a qualified designer with demonstrated experience in solar residences. If not, you have a great deal of reading to do.
Once your design is complete, the next key decision is deciding upon a contractor. Like the designer, it is most important to select a contractor with demonstrated experience in high-efficiency construction and solar utilization.
Get references and visit with them. Good luck!
Q: What is the best (most effective
and least costly) solar power system currently available to the individual
homeowner? What is the average cost of this system? And can you give tips on
what to look for, as well as what to avoid in a system?
A: If you are looking for the least costly investment to help reduce your energy consumption, it is not solar but rather energy efficiency that you should invest in. A dollar invested in energy efficiency will displace more units of conventional energy and return more dollars per dollar invested than a dollar invested in solar. Further, after you have addressed the efficiency issues, funds that you invest in solar will contribute a proportionally larger contribution to your requirements because your loads will be that much smaller.
The easiest and most cost-effective solar system for an existing home is a solar water heating system. These systems are relatively easy to install, deliver a full 12 months of service per year, and are within the reach of most homeowners.
Q: Could we build a solar panel at
home with things around the house, or do we have to invest in solar cells?
A: If you are very handy, you might be able to build a solar thermal collector. While there are cases of folks building their own solar electric modules, I do not recommend it. The most costly component is the solar cells and, if they are not keep sealed against environmental influences (mainly moisture), their interconnects can corrode and the panel will no longer work. Unless you are looking at this effort as a "science project" without expectation of multi-decade longevity, you should buy your solar modules from a well-known manufacturer and look for a 25-year warranty.
Q: Having just lived through
another mostly sunless winter and early spring, I wonder how my corner of New
England can use emerging solar technology to any economic benefit? A local
friend who installed solar roof panels to reduce her utility bills and maybe
even sell back to the grid has not seen any appreciable change.
A: You may recall that the Lords' solar home visited on the NOVA program was in Maine and that they have produced a surplus of electricity every year since their home was completed in 1994. If the home has appropriate energy-efficiency measures, solar can make a major contribution. We are now routinely designing true "zero-energy" residences that receive all of their energy from renewable resources. Some even have sufficient surplus solar power to meet the owners' local transportation needs when plug-in hybrids become available—about 18 months from now.
Q: If we use solar energy, is it
sure that the atmospheric temperature will not increase and there will be no
damage to the Earth environment?
A: Using solar energy will not increase the atmospheric temperature. The sunlight will strike your roof whether you choose to put it to work or not. Actually, the converse is much more likely: The widespread use of solar energy will decrease the heating of our planet by displacing energy from thermal power plants, which discharge large amounts of waste heat to the environment—in fact, often many times the value of the usable energy they deliver.
Q: It is my understanding that it
would take about 10,000 square miles of solar arrays to create enough energy
for the entire country. How much would this cost if we used solar reflectors or
PV solar arrays, and why are we (the U.S.) not working towards this and
eventually phasing out polluting power plants? Think about economies of scale!
A: You are correct that mass production and economies of scale are critical to addressing our energy needs with renewable energy. The good news is that solar and wind power are now the fastest-growing sources of new electricity capacity on the planet. While the current overall contribution is admittedly modest, these systems are inherently modular and quite amenable to mass production. Reflector enhancement is a good technique in areas with a high percentage of direct-beam radiation (bright sun/few clouds).
However, solar energy alone will not solve all of our energy requirements. We will need to employ all the renewable technologies atop a foundation of aggressive energy efficiency.
As far as cost is concerned, the days of cheap energy are now behind us. If you don't want to take my word for it as a solar advocate, check the two-page, four-color informational pieces placed in the major U.S. news magazines by the CEO of Chevron. We need to decide as a society what kind of future we want while we still have the relative luxury of this consideration.
Q: I have heard solar-power
satellites are really the best way to handle solar power. If true, why isn't
NASA working on those instead of trying to go to Mars?
A: I agree with you that we should certainly be paying more attention to the mounting problems here on Earth rather than spending money putting a man on Mars. The solar-power satellite concept may be intriguing on paper, but, when you understand the extremely high cost of boosting a pound of material into orbit, and the extremely high cost of supporting such a system once it is in place, you will appreciate how far-fetched the idea is. Then you can add the possibility that the microwave beam would drift from its receiver or possibly be used as a weapon. Attic roof insulation is far more practical.
Q: Hi Steven,
I'm 50 years old, have about 2400 sq. ft. of heating and cooling space in my home. I recently checked on going green with solar power and was told it would cost around $80,000. I'm on 100 percent disability, and that would cost me an arm and a leg I don't have. My electric rates run high here and that was one of the reasons I checked on this, plus it would mean that much more power I could save the world.
Do I have any hope of ever going
green? Are there any programs out there for the disabled or any programs our
government provides that would help me? I care enough that I'd even give tours
to go green, or I could become a model home for my area to show others how much
they could save and how important to our world this would be. Thanks for all
your great efforts and contributions across the world, Steven. Yours truly,
A: Charles, there are a number of programs available to help homeowners with their energy needs. These are available from the federal government, the state governments, and even from the local utilities. As mentioned earlier, the very best investments are in energy efficiency. The average American home has so much air leakage that, when it is all added up, it is the equivalent of leaving a window open all year. With the renewed focus on domestic issues of this Congress, we expect to see improved energy-program offerings from the federal level. Many states are already leading the way. To find out what support may be available in your area, you can check out www.dsireusa.org.
Q: If the average American wanted
to do a cost/benefit analysis of installing solar panels as a source of energy
for their home, how would they go about it?
A: First, tally up what your current energy requirements are (kiloWatt-hours of electricity, gallons of fuel oil, therms of natural gas) and how much they are now costing you. Then, get a whole-house energy audit—often available at little to no cost from your local utility. Rank-order the proposed efficiency upgrades and implement as many of them as you can. While the efficiency improvements are being completed, have your home surveyed to see what solar system(s) may be appropriate for your location, house type, orientation, available roof area, etc. The basic options are solar water heating, solar electricity, and solar space heating—the latter often being the most challenging to retrofit into an existing home. If you happen to have a heated swimming pool, install solar pool heating—don't even worry about payback.
Once you have your solar options defined and priced, get out your crystal ball and decide on how much the conventional energy you are now dependent upon will escalate over the 25-year life of the solar system you are considering. Next, check www.dsireusa.org to see what incentives may be available to help reduce your initial investment. Then, consider the additional value of taking some measure of control over your energy destiny while easing your family's environmental footprint.
Q: What is the best solar panel
available today? I'm only 10 years old, but I'm very concerned about the
environment. Thank you.
A: There are many high-quality solar thermal collectors and solar electric modules available on the market. The industry is currently in a period of rapid growth, and the products are rapidly becoming commodity offerings. That is to say that industry standards are helping shape a uniform standard of performance and longevity, which is now routinely backed up with 25-year warranties.
Q: For everyday people who would
like to help promote renewable energy through affordable stocks and other
investments, what are the best ways to start? Thanks.
A: While it may be difficult for the casual observer to find the right "pure play" in renewable energy, solar and wind stocks have done extremely well over the past few years as capital has poured into what is now becoming known as the "Clean Tech Sector."There are now a few mutual fund offerings in this area, which offer the upside opportunity coupled with professional management.
Q: Can you tell me how the new
concentrated photovoltaic sun-tracking solar systems compare with the
traditional flat-panel solar systems? I am told that the new concentrated solar
cells can now perform at 40 percent efficiency, as compared to 12 percent
efficiency for the traditional flat-panel cell, thus heralding a totally new
photovoltaic industry that will be much more efficient at producing power.
A: Concentrating solar systems are only of value in areas with a very high percentage of direct beam solar radiation (bright sun). With its abundant solar resources, the center of your country certainly qualifies. However, efficiency is not an end in itself. The tracking gear isn't free and, being mechanical, it surely requires a higher degree of looking after than the fixed, flat-plate alternative. Today's best silicon solar cells used in flat panels are now above 20 percent efficiency, and this is a moving target. What one should be looking at is the cost per kiloWatt-hour of delivered energy. With this in mind, I am placing my bets on mass-produced flat-plate PV modules.
Q: I'm planning to build a
three-unit home in Chicago. How much square footage of solar panels do we need
to provide power and heated water for three units? Each unit is for a small
family of four people. This is including a solar hot water system for each
unit. We have about 20' x 20' of space available in the roof (we
plan to do a rooftop garden also) and 24' x 20' in the garage roof.
A: As I mentioned previously, the best investments you can make are in energy efficiency. I consider energy efficiency investments as a fundamental prerequisite for successful solar utilization. With the available roof area you've described, I expect the best solar strategy will be domestic water heating for all units. This will deliver a full 12-month utilization and should be very cost effective against your conventional energy options. Remember, insulate before you insolate!
Q: Hi, I watched the program
"Saved By the Sun" tonight on PBS. I found it very interesting and
informative to watch. My question is: During the program they talked about the
new solar power panel grid that they are building outside of Las Vegas, but
mentioned that these solar power farms shut down at night because so does the
sun and that they cannot as of yet adequately store solar power. Yet on the
flip side, the program showed Germany and how they are leaps and bounds ahead
of North America with solar energy. How do they adequately store the solar
A: Day-to-night storage is not currently necessary to utilize renewable energy in conjunction with the power grid. Any surplus solar generation beyond your instantaneous load requirements can be exported to the grid where it simply displaces the use of conventional fuels. Studies have shown that the power grid can easily absorb 20 to 30 percent contribution from intermittent renewables and still do fine. Many have suggested even higher levels. As an example, Denmark is currently obtaining about 25 percent of its total electricity requirements from wind and is aiming even higher. Yes, low-cost storage for renewables will be very welcome. But we have a very long way to go before we need it.
Q: How do you handle snow, ice, and
winter weather on the solar panels? Thank you.
A: You needn't worry about snow and ice. The solar roofs on our north country homes are designed to shed snow as soon as the sun comes out after a storm. Check out the Lords' solar house in Maine featured on NOVA at their Web site: www.solarhouse.com.
Q: My goal is to design and build a
"grid-independent" home. There is much information available
surrounding the many ways to do this, but I'm wary of much of what is
available. Is there a trustworthy "clearinghouse" source that
contains info on solar, wind, geothermal, and other Earth-friendly methods of
providing energy for the individual homeowner?
Be advised that I recommend that you consider connecting with the utility if it is available. If you want autonomous carry-through when the power grid goes down, a back-up battery bank can be added to create a dual-mode system. Operating a residence on batteries 24/7 is expensive, requires considerable maintenance, and consumes at least 20 percent of your energy in losses during the round-trip charge/discharge cycle.
You might be interested to know that one of the best-known solar design firms (mine!) is located right in your hometown: www.solardesign.com.
Q: It's great to see interest in
solar growing and to see panels on at least some houses. But what about those
of us living in apartments? Any "intellectual ammunition" we can use
to motivate our building managers/landlords to go solar?
A: An economic case can now be made in many areas for using solar, but a key issue for owners/managers of apartment buildings is distribution of the energy. This could involve extensive rewiring of the building. For this reason, solar electricity is often employed to serve the so-called common loads in a multi-unit complex. My company is currently doing multi-unit residential projects powered by solar. As conventional energy costs continue to rise, I anticipate retrofitting will become more popular.
Q: Photovoltaic technology appears
to become more efficient and therefore more viable as an energy source every
year. Based on these advancements, do you believe that solar power will ever
fully replace our dependency on fossil fuels? How long might that take?
A: You are correct that solar is making dramatic advances in increased efficiency and lower costs. However, I'm sorry to say I don't anticipate that solar will—on its own—ever replace our current dependency on fossil fuels. There is simply no single substitute for what has been a 100-year bonanza of very low-cost, abundantly available oil and gas.
Hydrogen will not do this, nuclear will not do this, synthetic fuels will not do this, oil from tar sands will not do this, wind will not do this, imported liquefied natural gas will not do this. Nothing now identified or anticipated can or will serve as a direct replacement for our current world oil and gas consumption. "Business as usual" cannot continue on with just a simple substitute of technology. It will take every technology we have coupled with what I call aggressive/obsessive efficiency measures to begin to address the coming shortfall in world fossil fuel supplies as rapidly growing world demand exceeds available delivery capabilities, which are finite and now in decline.
The good news is that efficiency is relatively inexpensive, and the opportunities are virtually unlimited. We just have to get engaged in the process. As an example, the solar residences my firm designs require—on average—about 25 percent of the energy of a similar-sized home in the same climate and are more comfortable. Once the waste and excess are removed from the equation, renewables can make substantial contributions. Efficiency will always be the most attractive first option. The sooner our leaders understand this, the better chance we will have of defining policies appropriate for navigating the coming transition to the post-petroleum economy.
Q: Many discussions of solar
electricity generation address the issue of how to bring down the cost of solar
cells so that they are competitive with power from the grid. The new "thin
film" technologies are getting a lot of attention as promising a path
toward this low cost. What do you think the future holds for thin-film solar
cells? What fraction of the worldwide sales of solar cells do the experts say
will be thin-film technology in, say, five years? And how much cheaper are they
supposed to be, compared to silicon-based cells?
A: The main attraction of thin-film solar cells is that they require, on average, at least an order of magnitude less active materials in their manufacture. Since the active materials contain a good deal of the embodied energy investment, thin-film solar technology will be greatly benefited as conventional energy costs continue to escalate. However, the cost of the cells and modules is not the full story. You still have to install the system, and installation makes up about 30 percent of the overall system costs.
If it takes two to three times as many thin-film modules to deliver the same amount of power as their traditional crystalline silicon counterparts, then the cost of thin-film products will have to be low enough to offset this. Thin-film technologies are steadily gaining in efficiency—but so are the crystalline products. So you have a set of moving targets.
The wild card that does not get the attention I believe it deserves is the cost of conventional energy. Experts who study the individual technologies much closer than I do have predicted that thin-film products will steadily gain in market share. The other wild card is the enticing new technologies currently on or over the horizon. If you want an intriguing glimpse into the future, check out carbon nanotubes and quantum dots.
Q: I have been exploring the solar
option for my future back home in Pakistan. I know the cost is prohibitive, so
my question is if there is a market for used solar panels from the developed
countries that can be exported to developing nations, thus creating a reusable
markets. In short, do you think there exists such a marketplace for used solar
panels, and if not, what options do I have? Thank you.
A: Occasionally, there are used solar modules for sale, but not often and certainly not in the volume to make a market. One of the reasons why there are few used solar modules available is that no one wants to sell them if they are providing the service they were purchased to deliver. Today's solar electric modules routinely come with a 25-year warranty.
Having said this, I personally believe that the developed world have a moral obligation to transfer these renewable technologies to the developing countries as fast as we possibly can. The industrialized countries have now used up over half of the world's endowment of fossil fuels. One of the results of this is the development of renewable technologies.
For those who don't appreciate that we have used up the majority of (so-called) conventional energy resources and now owe to the rest of the world to help them transition to the next era, this can be reframed another way. The developing countries desire to achieve the same economic growth and prosperity the First World has enjoyed for the past 60 years. If our example is followed, this will require burning massive amounts of carbon-based energy that will stifle our air and cook our planet. It is therefore in our own best interest to transfer renewables to the developing world as fast as we possibly can.
The urgency comes as many developing countries are emerging from poverty, beginning to grow their economies and considering large investments in energy infrastructure. Simply put, in many cases, these investments are a one-time-only choice. Once the resources are invested in carbon-burning technologies, they can never be retrieved for investment in non-carbon-burning technologies. Since the industrial world is rapidly coming to the consensus that burning carbon is very bad for our future—that's everyone's future—we should then be taking steps to avoid it. One of the very best ways to do so is to help the developing countries leap-frog the slag heaps, open-pit mines, nuclear waste dumps, and wholesale pollution of land, air, and water that we have been conditioned to believe are simply part of the price for a higher standard of living and guide them into the next energy era. It would do us all a world of good.
Q: What are the most efficient
solar cells, and do you recommend installing this techology now or waiting
until the efficiencies improve?
A: The most efficient solar cells for home use are now approaching 22 or 23 percent efficiency. However, efficiency is not the end of the story. Cost/kiloWatt-hour is far more important. I recommend installing solar as soon as you are able—but, in the interest of full disclosure, I am not the most objective source on this matter.
Q: If your roof is angled East/West
rather then North/South, what is the best way to mount solar panels?
A: Likely on the ground.
Q: Is it possible to run a
2,500-square-foot home on solar energy alone? For how how long can someone
store solar energy? If we were going to mass-produce solar panels, could we cut
the price of installing them in half, and is there enough silicon to produce
A: Yes, indeed. We are routinely designing solar residences in all climate zones that obtain all of their energy from renewables. Check out the Lords' residence that was featured on the NOVA show at www.solarhouse.com. We have already cut the price of installing solar in half several times over the last 25 years, and the industry will certainly do so again. But remember, we are dealing with moving targets. Conventional energy costs are only going to continue their upward spiral, so price parity is closer than most people may think.
As far as silicon supply, silicon is refined from sand, so we will never run out of the raw materials. Yes, the world industry needs to develop more refining capacity, but that is already in the works.
Q: I understand that solar
technology has developed rapidly in terms of collecting and transmitting
energy. Has there been a similar advance in environmentally safe storage
systems, i.e., batteries, etc.?
A: Yes, battery technology is making major strides. This is largely the result of pioneering efforts by Japanese automakers to accelerate hybrids into the world market. The demand for better batteries for hybrid-vehicle drives represents an enormous market with sufficient volume to motivate the best companies to compete hard to win the prize. The most exciting opportunities are envisioned where hybrid vehicles are connected to the utility grid with a two-way power connection so that their battery banks can help supply very valuable peak power and level the demand on the distribution network. With the high cost of peak power now well understood, and utilities and regulators looking at real-time pricing, the so-called "vehicle-to-grid" technology offers considerable promise and considerable opportunity.
Q: I heard that solar panels are
considered haz-mat when disposed of. Please discuss the environmental impact of
panels and other equipment, both in their manufacture and disposal, and how
that compares to other methods of energy production. Thanks!
A: The U.S. Environmental Protection Agency did a study a few years ago with the Department of Energy in which they ground up solar modules and tested the remaining materials. They found they could be disposed of in landfills at the end of their useful life if desired. The vast majority of solar modules are made from silicon with a glass cover plate. Both the silicon cells and the glass that protects them are made from quartzite, which is essentially beach sand—hardly considered "haz-mat." Yes, there are minute amounts of other materials involved in some processes—certain of which are not necessarily edible. However, solar remains the least-worst way to make electricity that I know of.
Q: I built a solar room. At the
time, the person living next door said they were going to cut down their giant
white pines. As of this writing, they have not. Is there anything I can do to
have them remove the trees?? Thanks.
A: Have you tried baking them a pie or having them over for tea or dinner? If this hasn't worked, perhaps you should offer to at least help with the effort. Or, better yet, offer to pay for a professional to take the trees down for your neighbor!
Steven Strong is founder and president of Solar Design Associates, Inc., an interdisciplinary group dedicated to the design of environmentally responsive buildings and the engineering and integration of the renewable-energy systems to power them, especially solar electricity.
Over the past 25 years, Strong has designed dozens of homes and buildings powered by renewable energy. In 1996, he worked with Olympic Village architects to power the 1996 Summer Games with solar electricity with what was the world's largest rooftop photovoltaic power system. In 2002, he designed and oversaw the installation of three solar energy systems at the White House, and he has recently completed the design of a new "solar skin" for the U.S. Mission to the United Nations in Geneva.
Strong has designed solar-powered, zero-energy residences in hot and cold climates, including the first 100-percent solar residence in central Massachusetts in 1980. He recently completed the first zero-energy, solar-powered academic facility and the first wind-powered college campus. Strong is also a consultant on green technology and renewable energy for the new Boston studio complex of WGBH, the producing station of NOVA.
Strong is the author of a number of books and technical papers on photovoltaics in buildings. In 1999, Time Magazine named him an environmental "Hero of the Planet," and in 2001, the American Solar Energy Society presented him with its Charles Greeley Abbot Award, the Society's highest honor, for outstanding achievement in the advancement of solar energy. Strong says his overriding passion for renewable energy flows from his conviction that it's our best hope for sustained health and future prosperity on the planet.
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