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Materials Minimization: Overcoming the Challenge

Photovoltaic solar appears to be the perfect technology for generating massive amounts of clean, renewable energy. So why aren’t PV-based power plants popping up wherever the sun shines?


By Rob Lamkin



Clean, efficient and essentially limitless, the energy from the sun appears well suited to fulfill the world’s energy needs. So why do we continue to build and depend on plants powered by fossil fuels?

The main reason utility-scale solar has been slow to take hold comes down to cost. We in the industry must be able to compete head-to-head with fossil-fuel-based power plants that are being built at about US$1 per watt. This is the first challenge facing us as the new decade dawns. As we drive toward this cost goal, however, we must keep in mind yet a second challenge: Scalability. Once solar power plants arrive at the same cost point as fossil fuel plants, demand for solar will soar. We must be prepared to massive scaledelivering not kilowatts, nor megawatts, but hundreds of gigawatts.

There are many ways to approach the challenges of cost and scalability, but I believe the best solution is through the ‘smart’ design of our systems. That is, we need to design our solar energy systems using a materials minimization philosophy and by focusing on materials that are inexpensive and abundant.   


Why Materials Minimization Matters


There are many reasons for the higher cost of solar PV plants, including the costs of labor, energy, taxes, and materials. Out of all the factors that contribute to the final price tag, the one most within our control to reduce is the amount of materials. Granted, we cannot control the cost of raw materials, but we can, through smart design, reduce the quantities we use and we can choose materials that cost less. Materials minimization is key to meeting the cost challenge.

Many of today’s solar technologies rely on large amounts of raw materials in their designs, making it difficult for the resulting plants to compete with fossil fuel plants on the basis of cost.  For example, consider steel and aluminum. Steel is used extensively in system elements such as support structures, tubes and towers. Solar mirrors, support structures and heat sinks all depend on aluminum. A generic PV tracking plant requires well over 1,000 pounds of materials per kilowattmost of that being steel and aluminum. PV thin-film systems require even more materials, topping 1,800 pounds per kilowatt, with well over 1,200 pounds of steel and aluminum.

So why do the sheer amounts of materials in a system matter? If we set aside the variables of labor, time and energy that go into producing and installing the equipment, the lowest cost of a solar energy system is the cost of the system’s raw materials. The cost of a given technology cannot fall below this. It makes sense to look for ways to “lower the floor” by minimizing all materials use.

It may be tempting to ignore the task of materials minimization right now given that prices of materials have been falling. However, when large amounts of materials are involved, a small shift in price can have a big effectand material prices are anything but stable. For instance, in 2008, increased worldwide demand sent steel prices soaring, before the more recent economic turmoil sent them spiraling downward. According to a recent statement from the Organisation for Economic Co-Operation and Development (OECD) Steel Committee, the world steel market is slowly recovering, with average steel prices still down 35% in Asia, 44% in North America, and 52% in the EU compared from their mid-2008 highs. OECD also warns of a growing imbalance between capacity and demand, which may lead to a slump in prices, under-used capacity, and plant closures. However, when the economy improves, this diminished capacity may lead to higher prices. Aluminum has a similar story: mid-2008 prices stood at about US$1.20 a pound, compared to October 2009 prices of US$0.84 per pound.

All this volatilitysoaring prices, slumping pricesmakes it difficult to plan for the future. Right now, some raw materials may be relatively inexpensive, but there’s no guarantee that, as the world’s financial condition improves and countries and companies return to building and expanding, that those prices will remain low. Minimizing materials wherever possible will help mitigate the inevitable results of price fluctuations.  




Figure 1. Amount of raw materials in solar technologies. (Note that these values do not take into account the labor cost to install these components nor does it differentiate between grades of glass or other precision materials.) (Source: Cool Earth Solar)


Innovation and Substitution


As we work on minimizing our material usage, we can take a page from the solar community’s efforts in the area of solar cells. Solar cells are the most expensive components of most PV systems, with silicon being the primary raw material. Of all the materials used in traditional PV systems, silicon is one of the more expensive: New Energy Finance reported a spot price of more than US$25 per pound as of end of 2009. Thin-film PV and concentrating PV system designs look to drive down the costs associated with solar cell material by using less of it. Thin-film PV does this by depositing very thin layers of light-absorbing material onto a lightweight substrate, such as aluminum foil. CPV minimizes use of solar cell material by employing lenses or reflectors to concentrate sunlight onto highly efficient solar cells (such as multi-junction cells); shrinking the amount of traditional solar cell area needed to produce electricity, often hundreds of times over.

According to a 2009 National Renewable Energy Laboratory (NREL) report, “opportunities and Challenges for Development of a Mature Concentrating Photovoltaic Power Industry” some cost analyses predict that using high-efficiency concentrator cells can lead to very low costs for solar electricity. Bringing non-cell costs down, they conclude, can yield total systems costs in the desired US$1 per watt range.

For CPV, non-cell materials include those used in solar concentratorsmirrors, reflectors and other opticsas well as those used in heat management, tracking and support systems. The concentrators, in particular, are ripe for materials minimization schemes as they typically use the most resources in their efforts to capture and gather the diffuse sunlight. A concentrator design based on small amounts of a readily available, inexpensive material such as plastic, for instance, would help decrease the total amount of materials and the ultimate cost of the overall system.


Figure 2. Monthly price of aluminum from December 1999 through June 2009 (Source: Index Mundi http://www.indexmundi.com/commodities/?commodity =aluminum&months=120)


Meeting the Scalability Challenge


We also have to be prepared for success: Once utility-scale solar plants reach cost parity with fossil fuels, the advantage tips in our favor. All things being equal, given a choice between energy based on finite and ecologically problematic fossil fuels and energy based on “infinite” clean solar, there should be no contest as to which way the world will turn.

So what does success for solar mean? It means we will need to be prepared for a massive scaling up effort. Just how massive can be deduced from a quick examination of current and projected electricity needs. Today, the sun powers a miniscule amount of the energy used: less than 1% of the electricity used in the United States is from solar. According to the Energy Information Association (EIA), by 2030 the world demand for energy will be 31,800 terawatt-hours. An ambitious goal would be to supply half the world’s electricity from renewables, such as solar. That means we need to add nearly 7 terawatt-hours of renewable energy over the next 20 years. This coming decade is critical, if we are to meet this need to scale massively in what is, essentially, a very short period of time.

Here again, wise material selection and use is key to overcoming this challenge. In the previously mentioned “Opportunities and Challenges for Development of a Mature Concentrating Photovoltaic Power Industry” report, NREL noted that if concentrating PV technologies use non-cell materials that are also abundant and readily available, massive scalability then becomes possible. If the systems deployed depend on scarce materials, even in relatively small amounts, materials bottlenecks become a very real possibility. Thus, it’s important to choose abundant materials over those that are less soplastic over glass, for instance, or air over steelin designing our systems. Doing so will guarantee we won’t run into materials constraints once we commit ourselves to building enough utility-scale power plants to meet a meaningful share of the world’s electricity demands.

Once we decide to address this massive scaling-up challenge, it will be necessary to put terawatts into the field. Here too, careful materials minimization efforts can ease the plant construction and siting process. Systems that employ massive amounts of materials need substantial support structures. This requirement, in turn, leads to the need for extensive site preparations. Utility-scale PV system designs that forgo the use of heavy materials can avoid large foundations and footings, slashing siting costs and treading "light upon the land". Some solar technologies are moving in this direction with lightweight solar collectors supported by poles and wires. Any solar technology that minimizes the extensive renovation and destruction of the landscape will benefit from diminished costs and impacts on the environment.        


Figure 3. Solar contributed about 0.02% of the total electricity generated in the U.S. in 2008, while coal-fired plants provided about 50%. Renewable-energy power plants as a whole, excluding geothermal and hydro power plants, contributed about 2%. (Source: LLNL https://publicaffairs.llnl.gov/news/energy/energy.html)


Moving in the Right Direction


According to the recent Renewables Global Status Report: 2009 Update by the Renewable Energy Policy Network for the 21st Century (REN21), utility-scale solar PV power plants emerged in large numbers in 2008. By the end of 2008, an estimated 1,800 such plants existed worldwide, up from 1,000 at the end of 2007. Altogether, these plants totaled over 3 gigawatts, a tripling of existing capacity from 2007. Clearly, utility-scale PV is moving in the right direction, but we need to move faster, reducing our costs and putting more of our plants in the field more quickly. One way to do this is by building systems that make minimal use of materials and that opt for materials that are abundant.

If we do this, utility-scale solar PV will be in a good position to meet and beat the cost and scalability challenges. In doing so, we will be in the position of changing the fundamental economic equation of electrical energy and to offer consumers and utilities viable options for sourcing clean energy at costs comparable with that of fossil fuels.


Rob Lamkin is CEO at Cool Earth Solar (www.coolearthsolar.com). Lamkin has more than 20 years of experience in the energy industry. His career includes a variety of leadership positions, including those at Calpine Corporation, Mirant Corporation and the Northern California Power Agency. Under his direction, more than 10,000 megawatts of new power plant capacity were developed and over 6,000 megawatts were constructed and brought into commercial operation.



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