The latest innovations in renewable energy seek greater efficiency and lower costs
Until recently, breakthroughs in renewable electric energy technology debuted in relative obscurity. With high up-front costs and rates of return spanning decades, these technologies were deemed “alternative” or non-traditional, to be used only in cases of extreme environmental concern or high-end model projects. However, increased awareness about global warming, unprecedented prices per barrel for oil, generous utility rebates, the burgeoning popularity of Washington, D.C.-based United States Green Building Council's (USGBC) Leadership in Energy and Environmental Design (LEED) green building rating system, and mandated green practices through legislation at the federal level have converged to place renewable energy technology at the forefront of electrical construction in the residential, as well as — more remarkably — the commercial and industrial markets.
Signed into law December 19, the Energy Independence and Security Act sets increasing renewable electric energy provisions, essentially quintupling the use of renewable fuels by 2022. In Title IV, the law requires improved federal and commercial building energy efficiency, with green building standards for new federal buildings, as well as a zero net energy initiative to develop technologies, practices, and policies — with the goal of having all commercial buildings using no net energy by 2050. Furthermore, Title VI focuses on research and development (R&D) for alternative energy sources, such as installing and maintaining solar energy equipment and R&D to improve technologies to store solar power, as well as R&D for technologies to locate and develop other alternate energy sources.
Green design and construction has become an increasingly lucrative investment and a powerful selling tool. Growing worldwide and domestic use of renewable electric energy is expected to rival more traditional fossil fuel energy sources within the next decade. This demand has, for lack of a better word, fueled research and development efforts for more efficient, less expensive renewable energy production and storage, particularly in the solar- and wind-energy markets.
The global market for conventional solar photovoltaics (PV) is predicted to grow from $12.9 billion in 2007 to $32.3 billion by 2012, according to a technical market research report by BCC Research, Wellesley, Mass. The report, “Photovoltaics: Global Markets & Technologies,” estimates that multicrystalline silicon technology, which accounted for 89% of the market in 2007, will grow at an astounding rate of 285% through 2013. Through improvements in technology and materials along with its proven reliability, it is expected to remain the sustainable energy industry leader with 79% of the market.
“The market right now for solar worldwide is growing in the 15% to 20% range annually,” says George Douglas, spokesperson for Golden, Colo.-based National Renewable Energy Laboratories (NREL), the principal research laboratory for the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy. According to Douglas, the lab has a two-pronged goal for solar energy: to reduce the costs of solar energy, not just through commercial technologies but also through experimental technologies, so that the costs are on par with conventional ways of making electricity, and also to enable the manufacturing of super high-efficiency solar cells. Costs per watt can be lowered in two ways: by using super high-efficient cells or very low-efficient but cheap cells. The choice between the two depends on application. More efficient yet more expensive cells can be used for a smaller footprint that will have a high rate of return on investment. In instances where footprint isn't a consideration, less efficient cells, which are also less expensive, can be used to cover a large area, such as a flat roof.
Traditionally, silicon PV technology has consisted of modules and panels installed as a rooftop or standalone system. Recent innovations include flat-plate PV modules and panels fabricated in sheets resembling three-tab composite shingles, which are mounted on buildings or ground-supported frames. Other improvements to conventional solar panels include adding built-in wiring, grounding, and racking designed to provide maximum rooftop performance while minimizing installation costs for installers.
“The main thing you're going to see is modules getting larger,” says Tom Lane, CEO, Energy Conservation Services (ECS) Solar Energy Systems, Inc., Gainesville, Fla. Lane has been installing solar electric systems for residential and commercial applications since 1983, so he's experienced many changes with the solar cells not to mention the hardware used to install them. “We used to handle 50W and 80W modules, and then it was 160W to 200W modules. Now we're handling 200W to 300W modules.”
Other changes Lane has experienced are better inverters and mounting hardware, which cuts down his installation times. “Faster frames, faster racks, faster clipping, especially on flat roofs,” he lists. “Some flat roof systems go in without any penetrations.”
Other technologies entirely rethink traditional panels. Since mid-2007, Auburn Hills, Mich.-based Octillon Corp., an alternative energy technology incubator, has been researching silicon nanoparticles that could potentially convert glass windows into solar panels. The silicon nanoparticles are created through an electrochemical and ultrasound process that produces identically sized (1 to 4 nanometers in diameter) luminescent nanoparticles of silicon that provide varying wavelengths of photoluminescence with high quantum down-conversion efficiency of short wavelengths (50% to 60%). After thin films of silicon are deposited onto silicon subtrates by an electro spray system (capable of reliably depositing the nanoparticles onto glass surfaces), ultraviolet (UV) light is absorbed and converted into electrical current. With appropriate connections, the films act as nanosilicon PV solar cells that convert solar radiation to electrical energy.
“Contingent on the success of our ongoing research, we are optimistic that transparent cells based entirely on our nanomaterials will one day offer a cost-effective PV enhancement to conventional windows,” says Nicholas S. Cucinelli, president and CEO, Octillon.
One of the biggest drawbacks to traditional silicon solar technology is cost. In part, the expense comes from the price of silicon, which is an expensive commodity, particularly during times of short supply. In addition, silicon must be deposited on glass, so it's heavy yet fragile and expensive to ship as well as install because it has to be mounted. In addition, as much as 70% of the silicon is lost during the manufacturing process, so even the least expensive solar panels currently cost around $3 per watt of energy to produce. To compete with fossil fuels, such as coal, solar must reduce its cost to around $1 per watt.
“It could be 10 cents a kilowatt hour by 2020, which isn't as far away as it seems,” Douglas says. “It's less than 15 years to bring that cost down to where it's in reach of any electrical generation technology.”
However, it may take more time for residential applications to become more affordable. “Prices are dropping a little bit, but it's more affordable and more organized for large systems, for either power plants or for businesses,” Lane says. “The systems for homes aren't necessarily getting that much cheaper, but they are getting more efficient.”
According to Lane, it wasn't a technological innovation that brought solar costs for residential down. Allowing homes to connect to the electrical power infrastructure has made residential less expensive.
“That made systems a lot cheaper, when we were able to feed power straight back into the grid,” Lane says. “For one thing, it eliminated batteries, and the same system could produce more power. Now that you can grid connect, there's been an explosion of these systems.”
Thin is in
Many industry analysts believe that the future of solar energy is thin film, which, according to the BCC Research report, comprised a mere 10% of the market in 2007 but is expected to grow at a 45% rate through 2013 to make up 19% of the market by that time. In addition, the report cites that new technologies (such as nonstructured thin films and silicon and dye-sensitized solar cells), which accounted for less than 0.5% of the market in 2007, will grow by a rate of 34% to reach 19.2MW in 2008, and then exhibit 50% annual growth to achieve 145.7MW by 2013. The research firm credits constant research and development efforts on these new materials for the growth.
“We absolutely think thin film has two really great attributes,” Douglas says. “It uses a lot less of the extensive material in the solar cell, which is the semiconductor part of the solar cell, so it uses much less material. And that material can be applied in industrial techniques that are less labor intensive than silicon solar cells and can ramp up to fairly rapid manufacturing.”
Not everyone agrees that thin film is the future of solar technology. “I don't have much respect for thin film because of the power density,” Lane says. “They've not gotten the costs down to where it's competitive with single crystal or crystalline at the commercial or business level. Also, I don't see any companies backing it with a warranty of 25 years. So I don't think very much of it, and I don't think that it's a technology I would want to put on somebody's roof.”
Many of Lane's concerns may be addressed as thin film becomes more commercially viable. Manufacturing is the reason thin film doesn't compete with silicon right now, says Douglas. “People haven't quite got the manufacturing down at the level they should,” he says. “Also, the experience with silicon is by far greater so it has the lion's share of the market right now. But we expect thin films to grow faster than PV overall, so that it will take a larger and larger share of the market over time.”
As far as installation of thin film products, it won't differ much from PV except when deposited on flexible substrates. Thin films can be put directly on roofing shingles or sandwiched between pieces of glass that are used as architectural glass in the building. Roof penetration will depend on what type of product it is and how big the panels are and what type of roof.
“There are a lot more applications,” Douglas says. “But once it's installed, the rest of it downstream is the same. You're taking the DC power and somehow converting it into AC, and either feeding it back to the grid or into the house or building and back to the grid, so all of that wiring part is the same.”
Winds of change
Second only to hydroelectric power, wind power is one of the most important worldwide renewable sources of electric energy. Wind power has been experiencing strong growth for the last 15 years, and in coastal areas, where wind is the strongest, it can produce a considerable amount of primary energy with current generation costs closer to competitive levels than other sources of renewable energy. Worldwide installed wind power totaled more than 74,000MW in 2006.
For the residential or single-business markets, a single grid-tied turbine may be used. “In my part of the world, I always think of it in terms of farms and ranches,” Douglas says. “Just like a solar panel, this wind turbine can make the electricity meter spin backward when it's producing more power than is being used.”
A suitable location for the production of renewable energy is determined by the availability of the primary energy supply. One characteristic of wind energy is that it is extremely location-bound. Therefore, it's more suited to remote areas and not necessarily convenient for a power infrastructure designed and built around areas of high consumption. Favorable wind conditions are often outside the areas of concentration of power consumption.
“A lot of times, ranches are at the end of power lines and so the power fades,” Douglas says. “They get ‘brown power.’ So this helps that. And if you're a rural electric association (REA) with customers doing this, then it can also delay — if not altogether eliminate — the need to build new generation, which can be an incredibly difficult thing to do.”
The current research for mid-size, land-based utility turbines is focused on efficiency in order to expand the territory in which you can put wind farms or wind parks. Expanded territory, according to Douglas, means more locations to choose from as well as being able to place the wind farms in more populated areas that don't necessarily have the strongest winds.
“The very windiest areas of the world tend to be underpopulated — mostly because they're very windy,” he says. “So if you can have wind turbines that are more efficient and thus the cost of energy is lower in lower wind-speed regimes, you can put the wind farms closer to where people live. This reduces the need to build expensive transmission across long distances.”
Recent breakthroughs in efficiency have been incremental and concentrated on the mechanical works of the turbines, such as gearless boxes, multiple generators, types of lubrication, blade design, better electronics, and better control systems. “It's like, 1% here, 2% there,” Douglas says. “A lot of the work is going on in this sort of interior to try and squeeze more efficiency out of the turbines.”
There is a fairly direct correlation between size and efficiency with wind turbines. “Bigger has been better for a long time,” says Douglas. “And as they learn to make the machines bigger, all the engineering problems have to do with scaling up.”
The average size for a land-based turbine is 1.5MW to 2MW, and off-shore wind turbines measure between 2MW to 3MW, although there have been 5MW machines built in Europe.
However, because land-based turbines are built in one place and erected in another, their size is limited by transportation difficulties, such as interstate bridge considerations and the size of the cranes used to erect the towers. “Transportation becomes difficult above a 2MW machine,” Douglas says.
To overcome this challenge, some companies are considering building the turbines on the site of the wind parks. “Although nobody's doing this yet, it might make some economic sense just to build the factory right there and bring the parts there, and then build the turbines onsite. Then, once you've got the wind farm up, take the factory apart and haul it away,” Douglas says.
The extended reach of the blades may also cause problems. There isn't much information known about the atmosphere in which the blades operate, which is between human activity on land and in the air. The blades of a 7MW turbine will spend half their time in this part of the atmosphere. In order to maintain efficiency and keep them in good repair, more has to be known about the potential turmoil of warm air meeting cold air there. With that information, manufacturers would be prevented from both underbuilding and overbuilding the machines. “You don't want to build more into the machine than you have to because it adds expense,” says Douglas. “You want to build a machine that's as inexpensive as you can and still be safe, effective, and productive.”
In addition, scientists are studying weather patterns at that height, which will enable them to use controls for the wind turbines to maximize efficiency. “One of the reasons we want to understand the weather there better is to make the machines just the right robustness. The other reason is to be able to operate the wind farms more efficiently,” Douglas says. “You don't want to risk the turbines, but at the same time you don't want to have them shut down when there's a really good resource coming through. So the better you can understand what the wind's doing, the better you can manage the turbines.”
The shore thing
Although there are some disadvantages to offshore wind parks — special paint to fight corrosion from salt, concerns about humidity, and added maintenance costs for crew travel — it's easier to build larger machines offshore. “You can float the materials,” Douglas says. “It's easy to build really big stuff on the ocean — super tankers, for example, or oil platforms.”
There are other distinct advantages to offshore wind parks. Upward of 70% of the U.S. population lives within 25 miles of the coastline, either the Great Lakes or the ocean, making transmission less of a problem. Stronger winds offshore may produce as much as 50% more electricity. But unlike shallow shores that are ideal for wind parks off the coast of some European countries, the United States' shores are in fairly deep water. In the future, however, wind turbines may be able to be placed on platforms similar to those used for oil rigging. Another way to overcome the obstacle of deep water is to anchor the base of the turbine with weights below the surface but not on the floor.
“All these are engineering problems that aren't terribly well thought-out yet,” Douglas says. “People are thinking about them, but nobody thinks there are any showstoppers. We need to think about these things so we can make the most efficient, safest machines possible.”