The Fuel Of the Future

Cost reduction is the key objective of the photovoltaics (PV) industry as it strives to position solar power as a low-cost choice for new energy capacity. Three years ago, silicon wafer prices were high and PV modules were in short supply. With crystalline silicon cells making up ~80% [1] of the PV energy capacity produced annually, fluctuations in supply and cost of polysilicon [2] in recent years created a window of opportunity for thin film technology innovation, driven by manufacturing equipment suppliers seeking new high-growth business opportunities and and by module manufacturers looking for ways to diversify and/or enter a fast-growing world PV market. Within a short period, many existing and new PV manufacturers began choosing thin-film silicon technology to reduce their strategic dependence on polysilicon and to capitalize on new innovations in thin film technologies promising an advantageous manufacturing cost.

Then the world PV market changed in 2009. Today, silicon wafers and PV modules are in more ample supply, and negotiating power has shifted back to the buyer, though the near term outlook for c-Si components is somewhat uncertain because of accelerating demand. With cost leadership now a matter of survival in a tight PV market, the competitiveness of thin-film technologies has been challenged. However, a new generation of thin-film silicon technology is poised to regain cost leadership within the industry. Key innovations are helping to drive down cost and increase efficiency and reliability to reinforce thin film's competitive advantages in end user markets.

The fundamental advantages of thin-film silicon have not changed. Thin-film silicon PV modules require far less silicon than traditional methods (less than 1/100th of a wafer thickness) and use widely available, comparatively inexpensive materials. Thin-film silicon technology is inherently suitable for achieving very low manufacturing cost because the entire manufacturing process from bare glass to a complete PV module requires significantly fewer manufacturing steps than conventional crystalline technologies. Another key positive factor is that thin-film silicon technology uses only environmentally friendly, non-toxic substances. Finally, thin-film silicon panels have an inherent advantage in real energy performance, due primarily to the fact that thin-film silicon has a temperature coefficient "penalty" that is almost 50% lower than most conventional crystalline. In hot climates, this advantage results in 5% to10% higher output per installed watt compared to crystalline silicon.

We recently announced that our Thin Fab manufacturing line design has improved productivity, reducing the expected cost of production to €0.50/Wp and at the same time, a 100% increase in the output capacity and a 50% reduction in the capex per Watt. Together with improved stabilized lab cell efficiency of 11.9% for our Micromorph technology and a 10% stabilized module efficiency, these achievements are the result of innovations in cell and module design, equipment and facilities, silicon and TCO depositions, laser tools, and materials. Each of these is discussed below.

Thin-film cell/module design innovation

The efficiency of Micromorph cells and modules is the result of a combination of interrelated design innovations that significantly lower manufacturing costs. Improved transparent conductive oxide glass-coating (TCO) increases the transmissivity of the front glass and also enhances light scattering, increasing light capture (Fig. 1). Thinner amorphous and microcrystalline silicon "absorber layers" increase stabilized efficiency while reducing material costs and increasing manufacturing throughput. Finally, a new highly reflective white lamination foil enhances light capture and efficiency by reflecting photons back into the absorber layers of the cell. Figure 2 illustrates the improvement in reflectance that is achieved by using a white lamination foil instead of a layer of white paint. The introduction of a white lamination foil also helped to accelerate manufacturing productivity, as previously two manufacturing steps (applying white paint, then adding a transparent lamination foil) were replaced by one simpler manufacturing step (applying a white lamination foil). The combined effect of all of these improvements is a dramatically lowered production cost, now estimated to be €0.50/W with the new equipment. Also, the capital expenditure for Watt-peak power (Wp) is significantly reduced, largely as a result of increased equipment productivity. Finally, these changes have improved module performance with the new design yielding an expected production average module efficiency of 10% (stabilized). This new efficiency standard for thin film silicon will result in additional cost savings for installed PV systems.

Figure 1. Transmittance of Oerlikon Solar's TCO on white glass compared with other TCO alternatives and glass types.

Figure 2. Comparison of white foil lamination to white paint.

Equipment and facility innovation

In addition to cell and module improvements, new advances in manufacturing equipment and manufacturing processes also play a critical role in reducing the cost of thin film silicon technology. Over the past year there has been significant progress in accelerating throughput and increasing expected reliability and yield for several key manufacturing tools used in the production of Micromorph thin film silicon panels.

Silicon deposition. A new design for silicon-deposition PECVD tool, the KAI MT, was announced earlier in 2010. This tool builds on a well-proven design, including a high-frequency 40MHz Plasmabox reactor design that enables comparatively faster and uniform silicon deposition. The new design incorporates two significant changes that result in increased capacity and reduced footprint. First, the new design incorporates three deposition chambers per tool, with each deposition chamber capable of handling 10 modules at a time. The new configuration can be seen in Fig. 3a, where "PM" refers to deposition chambers. Previously, the KAI had just two deposition chambers per tool. This new design provides a 50% increased glass coating area and throughput, with no significant increase in equipment cost. Productivity is further enhanced by a modification in the silicon deposition itself, whereby both the a-Si top cell and the microcrystalline bottom cell are deposited in the same chamber, eliminating the need to expose the glass to atmosphere in between deposition processes and improving overall deposition speed and quality. Finally, the configuration of the deposition tools has been made significantly more compact by shifting the location of auxiliary equipment (e.g. vacuum pumps) to a mezzanine above the system, resulting in a 50% reduction in footprint.

Figure 3a and 3b. Layout of KAI MT vacuum deposition tool for Micromorph.

TCO deposition. A second example of significant equipment performance and production cost improvements is seen with the equipment used for deposition of transparent conducting oxide (TCO). This deposition is done in a low-pressure chemical vapor deposition (LPCVD) process and toolset. The integration of this TCO deposition tool into the thin film silicon manufacturing process allows for two key advantages over the use of pre-coated glass. First, on-site TCO deposition allows for the use of zinc oxide (ZnO) for the TCO layer, a material that yields a significantly higher performance than commercially-coated glass (which uses tin-oxide). Second, including the TCO deposition tool in the thin film silicon manufacturing line allows for optimization of the interface between the TCO and silicon absorber layers, resulting in enhanced light scattering, which results in increased light capture and higher module efficiency. Furthermore, the integration of TCO deposition into the thin film silicon manufacturing line allows manufacturers to use plain uncoated glass as a feedstock, resulting in a cost savings of €10 per panel or more compared with the cost of using pre-coated glass.

The most current version of our TCO deposition tool, incorporates several significant improvements. For example, optimized shields allow significantly stretched cleaning intervals. the deposition rate has been improved substantially' and the back transport of the glass has been changed for easier maintenance. As a result, the tool achieves higher uptime and throughput in the field.

Laser tool. The third example of "core" manufacturing equipment used in the production of thin-film silicon PV modules is the laser tool, used to sculpt the thin-film silicon and TCO layer stacks to form interconnected PV cells. Two key laser performance parameters that help to drive down production cost are the laser accuracy and the laser tool's processing speed / throughout. Improved laser accuracy results in a reduced "dead zone" between cells resulting from laser scribes. Figures 4a and 4b show the dramatic progress that has been made in this area to reduce the losses resulting from laser scribing processes in its most recent ThinFab design. The laser tools included in this manufacturing line are now capable of producing Micromorph modules with a dead zone of ~200μm, roughly half of the dead zone thickness that was typical for production just two years ago (and that is still typical for many thin-film module manufacturers today). The result is a reduction in the area loss within the module and higher module power. Furthermore, our newest laser tool (LSS) has doubled the number of laser heads, resulting in a 100% increase in throughput compared with previous generation tools, with increased reliability and uptime.

Figure 4. a) Comparison of laser design changes on dead zone width; and b) dead zone reduction track record. Source: Oerlikon Solar.

In sum, the changes outlined above to the "core" manufacturing equipment tools have resulted in substantially increased performance and productivity with 1) a more than 50% throughput increase, 2) a more than 50% module cost reduction, 3) a 100% increase in output capacity, and 4) overall fab line yields of ~97%.

Materials innovation

In thin-film silicon manufacturing, materials (e.g., glass, lamination foil, junction box, etc.) represent over 50% of the total cost of a thin-film silicon PV module. Reduction in the amount and price of key materials is a major factor in driving down the total cost of module production. Technology providers can greatly reduce the expected cost of module manufacturing by optimizing the design of the module itself, while aggressively working with suppliers of key materials to qualify several competing vendors of key materials for the modules. We have achieved a 50% reduction of material cost over the last three years, thanks in part to qualification of new suppliers and optimizing the minimum requirement specifications. In addition to the white lamination foil example described above, other significant material cost reductions have been achieved in the junction box, contacts, encapsulants, and the front glass.

Thin-film manufacturing equipment leaders are demonstrating tremendous potential to accelerate the pace of PV performance improvements and cost reductions, helping to position thin film silicon PV manufacturers to be competitive with other PV industry cost leaders, helping to make solar power economically viable.

Acknowledgments

Micromorph and Plasmabox are trademarks of Oerlikon Solar.

References

1. D. Cullen, "A Solar Cell Primer for the PCB Industry: Manufacturing Methods, Like Screen-printed Paste, are Giving Way to Photolithography," June, 2009, www.entrepreneur.com/tradejournals/article/201852199.html.

2. J. W. Pichel, M.Yang, "2005 Solar Year-end Review and 2006 Solar Industry Forecast," January 11, 2006; http://renewableenergyworld.com/rea/news/print/article/2006/01/2005-solar-year-end-review-2006-solar-industry-forecast-41508.

Chris O'Brien received his AB and BE degrees from Dartmouth College, and his MBA from Stanford U. and is Head of Market Development, Oerlikon Solar, Trübbach, Switzerland. Chris is based in Washington, DC - 700 12th Street NW, Suite 700, Washington, DC 20005; ph.: 205-558-5177; email chris.obrien@oerlikon.com.

Global warming and the effect of carbon dioxide emissions on the environment is of growing concern to countries worldwide, so much so that the EU has pledged that by 2020 one fifth of the region's energy will come from renewable energy sources. In response to this, many countries have introduced targets to reduce energy use. 

In the UK, for example, this comes in the form of the Carbon Reduction Commitment Energy Efficiency Scheme which was introduced in April 2010, and requires companies to reduce carbon emissions by 20% by 2020 and 80% by 2050.

As well as this, the European Union has launched the Emissions Trading Scheme, which calls for large emitters of CO² to monitor and annually report their CO² emissions. Through the initiative, the ETS pledges to cut CO² emissions by 34% below 1990 levels by 2020.

There is undoubtedly increasing pressure on organisations and countries to become greener. One of the biggest contributors to CO² emissions is the electric utility industry, accounting for a quarter of all carbon dioxide emissions worldwide, the largest share amongst all industries. For this reason, utilities are faced with the added pressure of curbing both their own and their customers' energy use. One way this can be achieved is through the successful implementation of smart grid infrastructures.

Smart grids deliver a series of benefits to utilities which can help in the reduction of carbon emissions, including the capability of managing distribution grids more effectively in order to create fewer emissions. What is more, the technology enables utilities to integrate renewable energies, such as wind, water and solar, into the grid. This means that sources of power from high carbon emitting energy sources, such as fossil fuels, can more effectively be substituted with renewable energies in an effort to reduce emissions, and consequently help meet EU targets.

However, despite the many benefits of the smart grid, a recent study conducted by Oracle Utilities, titled 'The EMEA Smart Grid Rollout', found that, while over a third of utilities across the region have made progress towards the adoption of smart grids and smart meters, the vast majority of utilities do not realise the full capabilities it delivers.

Addressing the lack of awareness

This lack of understanding around the technology is evident in utilities' awareness of the use of renewable energy within the smart grid. The study found that only 6% of utilities questioned across Europe, the Middle East and Africa (EMEA) consider increasing their level of renewable generation as a top priority over the next five years. What is perhaps more surprising is that some utilities surveyed across the region, including utilities from France, Greece and the UK, do not consider it to be one of their top three priorities.

One country that does place significant importance on the capabilities of integrating renewable energy sources into the smart grid however, is Turkey, with 100% of Turkish utilities surveyed considering it as their top priority over the next five years.

This can be attributed to the prediction that energy use within Turkey is expected to double over the coming decade, with the demand for electricity likely to increase even faster. Furthermore, Turkey aims to increase its renewable energy resources in electricity by 30% by 2023 to meet the increasing demands placed on its grid. With this in mind, it is hardly surprising that the country's utilities place so much importance on the benefits the smart grid brings in regards to renewable energy.

While many countries may not currently consider the smart grid's capabilities to integrate renewable energy into the grid as one of their top priorities, what is promising, as found in the report, is that two thirds of utilities surveyed do have plans to evolve their grids in order to support the technology and the subsequent level of renewable generation.

In fact, four fifths of German utilities surveyed have already started, or have plans to evolve their systems so that they are capable of supporting the smart grid. This is not only good news for utilities across Germany, but also for those across Europe. According to DENA, the German Energy Agency and adviser to the German government, Germany is faced with a unique problem in that it is currently producing too much solar power during the summer months. Feeding too much solar power into the grid could cause instability within the current infrastructure and lead to further problems. However, the implementation of smart grids can help tackle this problem. Smart grids enable the power gathered from the solar source to be retained in energy storage systems which can then feed into the grid during periods of peak demand, or when other renewable energy sources are low.

Furthermore, the smart grid can play an important role as countries across the EU formally draw up plans to link their clean energy projects around the North Sea in the form of a giant universal grid, being labelled as a 'supergrid'.

One criticism of renewable power has always been that due to unpredictable weather patterns it is unreliable. However, with a supergrid in place, Germany could distribute the excess solar power it generates to members of the supergrid who are not generating enough solar power during the summer months, while during the winter months, when solar energy is low, it could source its renewable energy from wind turbines off the Scottish coast.

It is clear to see that the smart grid provides many benefits in regards to renewable energy, yet 'The EMEA Smart Grid Rollout' found that only half of utilities surveyed across the region have a system in place to educate their customers on the environmental benefits of the technology. For utilities to get the most out of the technology in order to reduce their own and their customers' carbon emissions, utilities must increase their knowledge of the benefits of the grid and smart meters, which they can then pass on to their customers. The Netherlands, Sweden and the UK are already well on the way to doing this with 100% of utilities surveyed, from the respective countries, having in place a communications programme to educate their customers about the environmental benefits of the smart grid.

However, in order to successfully implement a smart grid infrastructure and reap the full benefits of the capabilities available, utilities must take it upon themselves to leverage the tools that enable them to extract intelligence and manage data created by smart meters. One such software application is meter data management (MDM), a key component of the smart grid platform. MDM allows utilities to manage the vast quantity of data gathered from smart meter deployments helping turn the data into actionable intelligence, enabling utilities to improve service by accurately responding to the demands placed on the grid. For instance, MDM allows utilities to see when power is in peak demand, meaning they can feed more energy from renewable sources into the grid to meet customer demand.

Another technological innovation that can enable utilities to manage data volumes more efficiently is a customer information system (CIS), which is an enterprise-wide software application that allows companies to manage every aspect of their relationship with a customer. The system helps turn customer satisfaction into customer loyalty. Therefore, an effective CIS could play a crucial role in allowing utilities to educate their customers on the environmental benefits of the smart grid.

Furthermore, an intelligent CIS delivers additional benefits, especially when supported by a smart grid infrastructure. For instance, it can enable better forecasting and management of the energy demands placed on the grid. Moreover, the solution is able to provide optimisation capabilities that can determine the best mix of energy and resources required to handle changing voltage requirements within certain areas. Consequently, a CIS could not only play an important role in educating customers of the renewable benefits of the smart grid, but it also enables utilities to provide the best mix of energy needed to satisfy the demands placed on the grid.

Smartening up

As pressure grows on various organisations and countries around the world it is increasingly important that utilities begin to realise the full benefits of the smart grid, especially its capabilities to integrate renewable sources. Similarly, as alternative sources of energy begin to run low, it will be crucial for utilities to have in place a system that enables them to input renewable energy into the grid. 

Smart grids will be critical in helping utilities meet the various regulatory demands placed on them in an effort to reduce carbon emissions and integrate renewable sources, as well as helping them cope with the increasing power demands of growing populations and improved infrastructures across the globe. Renewable energy can play a crucial role in helping utilities meet these demands, and the smart grid can play a vital role in making it a reality.

Bastian Fischer is vice president and general manager of Oracle Utilities, EMEA

The news became political fodder in a US mid-term election year and has been highlighted as an example of the nation's failings. With US jobs at stake people are worried, and for good reason.

That's one way to look at it. Another is that China's rise offers a new and crucial opportunity. Paired, the countries can float a tremendous clean energy market that could buoy the industry worldwide – or sink it if they fail.

'Imagine a small canoe, barely above the waterline with two sumo wrestlers, China and the US, in it – one at each end,' says Elton Sherwin, senior managing director at California-based Ridgewood Capital and author of the book Addicted to Energy.

The rest of the canoe, he says, is packed full of people from all of the other countries. The two sumo wrestlers account for 42% of the world's energy demand, are the world's biggest coal consumers and the largest importers of oil. Both have aggressive goals to integrate renewable energy into their supply mix and they lead the way in wind power development. Last year China installed 13.8 GW of wind power, the US added 10 GW.

A recent criss-crossing of the globe by industry leaders and government officials from both nations demonstrates a heightened understanding of their paired potential and they have been meeting to investiagte joint green energy opportunities. China brings to the table its cheap manufacturing capability and the US its high tech know-how.

'We can't view this as one against the other. Over the past 12 months, partnerships and collaborations and deals from the manufacturing side all the way up to the development and installation side have really taken off. It makes a lot of sense. We are working together on the government side and private sector side to grow the pie and make it beneficial and profitable for businesses in the US and China,' said Foley & Lardner partner Jeffery Atkin.

One such meeting, a panel discussion entitled 'US-China Private Sector Cooperation in Energy', brought together industry and government heavy hitters in early October at the Woodrow Wilson Center in Washington, D.C. Among the attendees was Jim Rogers, chief executive officer of Duke Energy, one of the US' largest electricity companies.

'I believe that China and the US are uniquely positioned to answer the environmental energy challenges for the globe,' he said at the forum. 'We are smart enough and have a clear enough vision to be able to cooperate and compete at the same time.'

While the two nations have many political and social differences, both face similar challenges in their power sectors. Both depend heavily on coal as a core energy resource; it accounts for 50% of the electricity mix in the US and 80% in China, which in turn makes the two countries the largest carbon dioxide emitters in the world. Also at the forum was US secretary of commerce Gary Locke, who said: 'If not addressed, this current energy mix will significantly impact our businesses, our environment, and our way of life in both countries.'

China's success in wind turbine manufacturing has some in the US concerned (Source: Sinovel)

The Great Grid of China

In addition to many similarities in energy supply, both countries are poised for enormous electricity transmission grid build-outs, which will be required to meet increasing energy demand through to 2050.

Rogers sees a 'daunting challenge' ahead for the US. The nation will need to spend an estimated $2.1 trillion to meet its electricity demand by 2030, with consumption set to grow at an estimated rate of 0.5%/year through to 2035.

Over the next 40 years almost all US power plants, with the exception of its hydroelectric sites, will have to be retired and replaced, said Rogers. This comes on top of the transmission and distribution overhaul needed for smart grid applications. 

Conversely, China will focus less on upgrading an outdated grid and more on building new facilities. It has 700 million rural inhabitants, 15 million of whom, it is anticipated, will flock to its cities every year. By 2025, China is expected to build 40 billion m² of floor space across 5 million buildings – the equivalent of two Chicagos every year, said Rogers.

Electricity consumption rises in line with higher average incomes through the increased use of energy-hungry devices such as refrigerators and air conditioning units. By 2030 an estimated $3.1 trillion will need to have been spent to keep up with China's burgeoning demand.

With such levels of growth predicted in China and the US entirely new power infrastructures in both are expected to be built in the next 40 years.

Big Problems, Big Solutions

With such daunting figures, it is an enormous challenge for the two countries to simultaneously meet new demand and achieve reductions in greenhouse gas emissions, but significant progress is afoot. 

China has a five-year plan for renewables to account for 15% of its energy mix on top of a 20% reduction in greenhouse gas emissions by 2020.

In just three years, the country became the world's largest producer of photovoltaic panels, according to Pricewaterhouse Coopers' (PwC) recently published document: 'US-China Cleantech Connection: Shaping a new commercial diplomacy'.

The US is also making hefty strides in cleantech development, an example being its solar industry, which by the end of the year is expected have seen a year-on-year doubling in size, despite ongoing global economic issues, according to trade group the Solar Energy Industries Association.

The president and CEO of SEIA, Rhone Resch, recently announced a target for the US to install 10 GW/year of solar by 2015. Simultaneously the US government began to approve the construction of large utility-scale solar plants on federal land. Construction work on several large projects is expected to be underway by the end of the year.

Bolstered by strong government commitment over the past two years, the US is shaping up to be the largest solar market in the world, with its potential serving to attract Chinese companies including Suntech Power Holdings. The company, the world's largest crystalline silicon PV module producer, said earlier this year it plans to construct its first manufacturing plant in the US, while Yingli Green Energy is also said to be considering building a facility in the country.

Can The Marriage Work?

However, not everyone in the US welcomes expansion of Chinese companies into the US clean tech market. One concern is that while China may excel at cheap manufacturing, there may be quality issues with its goods, a problem acknowledged in a recent report published by Greenpeace, the Global Wind Energy Council, and the Chinese Renewable Energy Industries Association.

Kumi Naidoo, executive director of Greenpeace International, said in the report '2010 China Wind Power Outlook' that China remains dependent on Europe and the US for key wind turbine design technology; that it lacks experience in operating and maintaining wind farms; and that its workers' skills are 'insufficient'.

'To face and address the long-term problems, China needs to learn constantly, create opportunities for international cooperation and communication,' he said. The country must also establish a 'cooperative mechanism of win-win and multilateral wins with wind power corporations and research institutes all over the world in order to learn other countries' strong points, compensate for [its]own weak points, and develop together'.

To date the Chinese solar industry has largely been driven by the production rather than the utilisation of its PV technology. Indeed in 2009, one third of the world's PV panels were produced in China, yet installations there accounted for less than 3% of the global total, according to PwC.

Some quarters have voiced concerns that this allows Chinese manufacturers to have less stringent quality standards. However, again according to PwC, as China finds a new balance and moves from largely being a solar technology producer into an adopter, an broad upturn in quality to Western standards is expected to follow.

A technologically-innovative and growing Chinese market is also expected to see more widespread applications in China itself, while welcoming the country into the global market will force it to raise the quality of the goods it manufactures.

The Chinese installation market remains wide open and therefore provides a huge opportunity for US companies that produce high quality products to seek to do business there.

In September 2009 US-based First Solar unveiled a memorandum of understanding with Chinese government officials to build a 2 GW solar power plant in the Mongolian desert. The development site, slated for completion in 2019, requires cutting edge technology and high quality components.

The growth of the clean technology sector in both countries is in part due to the state of the industry in the other, with companies from each becoming increasingly co-dependent. Bilateral trade and investment between China and the US has given and continues to give citizens from both countries greater access to high quality products and services, according to Locke.

An example of this is the growth in China's middle class, which has spurred demand for US products, helping US producers' order books and satisfying Chinese consumers, while lower-cost products from China which are being sold in the US mean a potential increase in the disposable incomes of US citizens. 'That is what a win-win relationship looks like,' said Locke.

Another major partnership opportunity between the US and China is the development of smart grid technology. The PwC report forecast that China could spend up to $100 billion over the next decade on smart grid development, which could result in the deployment of 300 million smart meters alone.

Not surprisingly, Intel Corporation recently consolidated its chip-making operation in Chengdu into a 2400-employee facility and is now the largest chip packaging and testing base in Asia.

To help US companies penetrate Chinese and other foreign markets, the Obama administration in March launched the National Export Initiative, which seeks to double exports from the United States over the next five years.

'I am confident that our efforts and a sustained focus on the National Export Initiative will allow the US, China and countries all around the world to reap the benefits of the emerging clean energy economy,' said Locke.

Entering the US market, however, is another story. Accessing this market can pose difficulties for international companies owing to a quagmire of local, state and federal regulations.

'The US is very complex compared with most other places in the world. It is more time consuming. That is a reason why foreign companies, the European companies, the Chinese companies, are joint venturing and partnering with local companies,' said Foley & Lardner's Atkin.

Drying biosolids to approximately 75 percent solids, beyond the 15 to 20 percent solids typical at wastewater treatment plants, was recognized as the best way to create a workable, pathogen-free biosolid that could be used as cover at the Toland Road Landfill in Santa Paula, with potential future use as fertilizer or fuel. A biosolids drying system was developed to meet the long-term disposal needs of Ventura County in an economical, environmentally responsible manner.

Mechanical biosolids dryers were chosen as the approach to minimize project footprint, provide pathogen reduction and create a marketable product. Although Ventura County cities individually produce biosolids output below that required of economical large-scale dryers, it was determined that a regional-scale dryer could amass biosolids to a greater economy of scale.

The growing quantity of landfill gas (LFG) at Toland Road Landfill was seen as a way to reduce costs for natural gas and electricity: primary dryer operating costs. LFG would fuel process heaters, which in turn would heat oil to indirectly dry the biosolids. The LFG would also be used as a fuel to generate electricity which would provide the dryers' electrical needs.

The biosolids drying and electrical generation technology would ideally be modular, allowing easy up- or downsizing, depending on the number of cities interested in contracting with VRSD and considering the increasing LFG output for electrical generation. The modular approach allows use of standard equipment models, instead of custom design/fabrication and the accompanying cost/operational problems.

A system of condensing, treating and using the reclaimed water extracted from the dryers' exhaust steam had to be developed. (This process typically occurs at wastewater treatment plants where high flow water spray is used to condense steam, with the resulting wastewater routed into the treatment plant's headworks; not possible at a landfill.) Microturbines were chosen as a modular, low-emission, simple-operation (no contract operator needed) approach to generating power.

A Self Generation Incentive Program (SGIP) grant from the local electric utility (Southern California Edison) helped finance the project. The SGIP is provided to promote self-generation of electricity. This project creates over 750 kW of load, which is completely offset with dedicated on-site microturbine power generation, which equates to nearly a $1 million grant.

At full capacity, VRSD's Biosolids Drying and Renewable Power Generation Facility will:

• Dry 320 tons of biosolids daily
• Produce AB 939 recyclable material with multiple uses including alternative daily cover for the landfill, fertilizer or fuel
• Generate 3.25 MW of renewable/green power (1.5 MW for onsite demand and 2.25 MW for export)
• Reduce truck traffic up to 1 million miles a year by disposing of biosolids locally (compared to previous longer haul to Kern County) and decrease related greenhouse gas emissions by up to 1,800 tons annually
• Reduce the demand on existing conventional power generation facilities, thereby offsetting up to 15,000 tons of fossil-fuel-based carbon dioxide annually
• Provide Ventura County with a local biosolids management solution
• Serve as an innovative LFG-fueled regional biosolids drying system that can be replicated in other communities.

After four years of conceptualizing, designing, permitting, negotiating a power purchase contract, completing site work and equipment installation, the VRSD facility began operation in the fall of 2009.

The Setting

VRSD is an enterprise public agency organized in 1970 to serve the sanitation needs of more than 600,000 residents of Ventura County. Comprised of eight charter cities and eight special districts, VRSD provides solid waste management, wastewater treatment, water supply and related services to its customers. VRSD's operations are funded solely through revenue derived from services; the District receives no tax-based support of any kind. VRSD is overseen by a nine-member Board of Directors who represent the cities and special districts served and employs approximately 70 people.

Biosolids are the organic materials resulting from highly processed wastewater treatment operations. Ventura County currently produces about 8,000 tons a month. Prior to the start-up of VRSD's Biosolids Drying and Renewable Power Generation Facility in September 2009, approximately 90 percent of those biosolids were trucked out of the county for disposal.

Potential challenges to this practice arose several years ago, including restrictions limiting export options. The most significant of these was passage of Measure E in 2006 by voters in Kern County. Measure E sought to halt the importing and land application of biosolids in Kern County. The measure passed but was challenged in court by the City of Los Angeles (a major exporter of biosolids to the county). The city prevailed in 2007 and exporting continued; however, Kern County officials appealed the judgment in March 2008 and the issue remains in the courts as of the publication date of this article. Uncertainty as to the ultimate resolution of the issue was a major factor in VRSD's decision, together with its member cities, to seek a local, more reliable solution for the long term. Increasing transportation and environmental compliance costs added to the motivation.

Ultimately, the solution arrived at through cooperative effort involved proven, economical biosolids drying technology and renewable power generation, fueled by readily available and cost-effective landfill gas. This innovative idea promised:

• Local control
• Environmental soundness
• Multiple benefits
• Replicability elsewhere.

Project Overview

VRSD's Biosolids Drying and Renewable Power Generation Facility is located at the Toland Road Landfill in Santa Paula, Calif. Owned and operated by VRSD, the landfill handles up to 1,500 tons of municipal solid waste per day. The Biosolids Facility occupies a 2.7-acre site within the 343-acre landfill property.

The facility was designed and built at a cost of approximately $19 million, broken down as follows:

• Permits, engineering, project management ($1.0M)
• Site work ($7.0M)
• Dryers (2) ($5.4M)
• Trailers (11) ($0.5M)
• Microturbines (9) ($2.8M)
• Gas conveyance system ($2.0M).

The project was funded by a combination of cash, debt and the self-generated incentive power (SGIP) grant of approximately $1 million.

Biosolids contracts with Ventura County cities and sale of electricity to Southern California Edison (SCE) are funding operations and debt repayment. As of the date of this article, VRSD has negotiated 10-year contracts to accept biosolids from four Ventura County cities at a rate of $52 a ton, which is extremely competitive with costs associated with land disposal ($40 to $60/ton), composting ($45 to $65/ton) and other drying technologies ($75 to $100/ton). VRSD also negotiated a 10-year contract for energy sales to SCE at a rate of $0.10 per kilowatt hour.

Project Timeline

VRSD initiated a demonstration project in September 2005 to evaluate process technology and address potential environmental compliance issues. The District initiated meetings with landfill neighbors and community groups in 2006 and circulated a California Environmental Quality Act (CEQA) Mitigated Negative Declaration Document in June 2006. After receiving input from the public and addressing regulatory concerns, VRSD revised and recirculated the document in December 2006. A conditional use permit was issued by the Ventura County Board of Supervisors in January 2007 and final design and site work started. Construction was completed in July 2009 and the facility began initial operation soon thereafter.

Among the agencies responsible for environmental and regional regulatory compliance were the following:

• Ventura County Planning
• Ventura County Air Pollution Control District
• Ventura County Agricultural Commission
• Ventura County Environmental Health Division
• California Department of Public Health
• California Integrated Waste Management Board
• California Department of Fish and Game
• U.S. Army Corps of Engineers

Powered by Landfill Gas

Decaying refuse produces landfill gas (LFG) with high methane content. Prior to construction of the Biosolids Facility, VRSD extracted this gas and flared it to atmosphere, a common practice at landfills. Today, that gas is captured, treated, and used to fuel the biosolids dryers and run a system of nine microturbines. The latter generate electrical power to run the facility and export to the local grid. The dried biosolids are currently used as alternative daily cover (ADC) for the landfill; VRSD is exploring alternative use of the material as fertilizer and fuel.

Before it can be used by the biosolids dryers and the microturbines, LFG must be properly treated. To eliminate fouling and remove volatile organic compounds, liquid is removed from the gas through a dew point suppression system. Sulfur is also removed from the roughly 150 ppm sulfur gas using Sulfatreat media to comply with the regulatory limit of 60 parts per million. Siloxane is removed using carbon and Midas media. The gas is pressurized by blower and compressor units for use by the dryers (~10 psi) and microturbines (~100 psi).

Biosolids arrive via truck from local wastewater treatment plants and are deposited into a receiving hopper at the facility. From there, they are diverted into two storage hoppers (300 cu. yds. total), which hold approximately nine truckloads of material. For every four truckloads of wet biosolids delivered, the process yields one truckload of dried material.

The process, including storage, is under a vacuum routed to a carbon filtration system for odor control. Compressed LFG heats oil in two ultra-low-emission thermal fluid heaters to approximately 450 F for the indirect drying process. The heated oil circulates through rotors within the drum and the drum shell to bring the biosolids to the boiling point (pasteurization) for several hours to evaporate liquids. Typically, a load of biosolids remains in the dryer for three to four hours, depending on moisture content. Each of the two dryers has a capacity of approximately nine tons. After each batch is completed, the dried biosolids are conveyed into trailers and hauled to the landfill for use as ADC. The steam exhaust is piped to the condensation/treatment process described below.

VRSD chose to employ an indirect, complete mix batch technology. These dryers are built as a modular system, allowing addition of units as demand increases. They occupy a compact footprint and are flexible enough to handle biosolids of varying mixtures and liquid content. Direct-fired dryers, on the other hand, use significant quantities of air, which must be treated using bag houses and/or thermal oxidizers (RTOs) and are generally more sensitive to biosolids of varying moisture content. They also generally require more space, a custom-design, more complex operation and are more expensive. The dryer system selected by VRSD was designed and manufactured by Fenton Environmental Technologies.

A system of internal rotors moves the biosolids material through the dryer. Hot oil circulates within the rotors and also within the dryer shell. Steam from the process is condensed and the condensate (reclaimed water) is treated and used for dust control at the landfill. The exhaust from the drying process is filtered through a series of filters (biofilter, carbon and HEPA) to remove odor and ensure environmental compliance at discharge.

Steam exhaust from the biosolids dryers enters a condensation unit where it is condensed using cold water supplied from evaporative cooling towers. This is the only part of the entire process that does not make use of a recycled resource. As part of the permitting process, VRSD agreed to use potable water for the condensation process, as opposed to using the reclaimed water from the biosolids.

Treatment of the exhaust air consists of a biofilter system using a treated rock media, supplemented in a pre-biofilter process by the application of phosphoric acid to reduce ammonia content. Carbon and HEPA filters provide final polishing before the air is released.

The condensed steam, or reclaimed water, is treated with a polymer clarification process to remove fats, oils and greases (FOG) and sediment, which are trucked offsite for treatment and disposal. The reclaimed water is pumped to an irrigation system for use as daily dust control on the landfill.

Electric Power Generation

The facility currently uses a system of nine Ingersoll Rand 250 kW microturbines (expandable to 15). Depending on demand, the three microturbines dedicated to supplying power for the facility's 750 kW load cycle on and off automatically to match the varying load. The remaining six units exporting power to the grid run continuously. Approximately one-third of the 2.32 MW currently generated is used onsite; the remainder is transmitted to the SCE power grid.

• VRSD's Biosolids Drying and Renewable Power Generation Facility is SCADA controlled for remote operation and monitoring. While it runs 24/7, it does not require round-the-clock staffing beyond on-call personnel to respond to any alerts or shutdowns.
• With a current maximum processing capacity of 160 tons of biosolids per day, the facility design is expandable to double that amount.
• The nine microturbines currently generate 2.32 MW; VRSD designed the facility to accommodate an additional six units for a total power production capacity of 3.82 MW.
• The green, sustainable low-emission power complies with the scope of California's Renewables Portfolio Standard.

This regional biosolids drying solution is among the first of its kind in the nation. A compact, modular system, it can easily be replicated in other communities.