Composites & Renewable Energy

Aside from hydropower, renewable energy sources have not received mainstream attention until recent years. However, the growing realization that global warming is for real, and that the world's finite supply of fossil fuels may not last another hundred years, has begun to focus the world's attention on renewable energy. Adding urgency to this shift in focus, is the fact that near-term climate change may prove much more problematic to society than the ultimate depletion of fossil fuels.

A lot has been written about the use of composites in wind energy production. And for good reason. Composite materials make up a significant portion of the materials that are used in construction of wind turbines. Wind energy represents a rapidly expanding market segment for the composites industry Both 2005 and 2006 saw more than 25 percent growth in installed generation capacity. As of the end of 2006 the current global installed generation capacity was in excess of 70,000 megawatts, with some of the largest turbines exceeding 5MW. And rotor blades are approaching 200 feet in length. Turbine rotor blades, as well as most nacelles and spinners are made primarily from composites.  That, in turn, has created a very robust market for the composite materials that go into these components. Some resins and core materials have been in short supply as a result.

However, while explosive growth of composites in wind energy has been capturing the attention of the composites industry press (see 'Windmill Blade Production' CAI March 2006), other forms of renewable energy have been experiencing steady, if not rapid, growth in the application of composites. There are a variety of uses for composites in ethanol and bio-diesel production, as well as in the generation of methane and other combustible gases from biomass. In addition, composites have found a niche in hydrogen storage. Although hydrogen, as a fuel, is not necessarily produced from renewable energy sources, as fossil fuels become more costly as motor fuels, hydrogen as a fuel will, no doubt, become part of the renewable energy supply chain. Solar, geothermal, and hydroelectric power generation have also seen the limited application of composites, but will not be covered in this article.

The production of ethanol (aka Ethyl Alcohol, the very same substance that puts the buzz in adult beverages) for motor fuel has also grown at double digit rates in recent years as a result of both increasing gas prices and related tax incentives. President Bush recently announced a national initiative to greatly increase the production of ethanol as a means of reducing our nation's dependence on imported oil. Currently, in North America, most ethanol is produced from corn, although any crop that can produce sugar can be fermented to produce ethanol. In Brazil, where ethanol is well established as a motor fuel, Sugar Cane is the crop of choice for ethanol production.

The market pressures that current ethanol production has put on North America's edible corn crop as led to an intensive research effort to develop bin-processes that would convert non-edible (by humans) cellulose to ethanol. President Bush's 'Twenty in Ten Initiative', which intends to increase the use of alternative fuels to 35 billion gallons per year by 2017, has earmarked $385 million for six biorefineries that are projected to produce upwards of 130 million gallons of cellulosic ethanol per year within four years. Cellulosic ethanol can be produced from nonfood plant materials such as switchgrass, corn stover, grain crop straw, milt) stubble, switchgrass, wood chips, sawdust, and other feedstocks. The refining process for cellulosic ethanol is somewhat more complex than that of corn-based ethanol, but cellulosic ethanol yields more net energy and produces less greenhouse gas. Theoretically, this technology would enable the production of ethanol from almost any plant.

Although composites don't play as glamorous a role in ethanol production as they do in wind generation, there are significant applications for corrosion resistant composite components in ethanol production. And demand for those components will grow as new ethanol plants are built. Design Tanks, of Sioux Falls, SD has been filament winding and spin casting ranks and vessels for ethanol plants in die Mid-West, which is where the majority of ethanol plants are currently located. Tom Huegel, the President of Design Tanks, says that the primary application for composite tanks has been for the containment of acid solutions that are used for cleaning the processing and fermentation vessels and piping that are used in the ethanol production. In addition, ethanol plants typically reclaim and recycle the water that is used in the ethanol production process. The equipment that reprocesses that water often incorporates composite tanks and vessels. Design Tanks has built ranks, up to 14- ft. x 50-ft. in size, to contain recycled water at ethanol plants. Those ranks, which can hold upwards of 65,000 gallons, are typically filament wound with a Vinylester corrosion resin and incorporate a 10 mil synthetic fiber veil to provide a resin-rich inner surface to provide maximum chemical resistance. Design Tank has also developed proprietary fabrication equipment for centrifugally casting tanks up to 8 feet in diameter. In the centrifugal casting process the laminate is applied to the inside of a revolving mandrel, rather than to the outside of a mandrel as in filament winding. Centrifugal casting has the inherent advantage of creating resin rich, chemically resistant interior tank surfaces because centrifugal force forces the denser glass fibers against the exterior wall of the tank, while excess resin rises to the surface.

The term 'Biomass' is often used in reference to renewable energy production. Biomass Energy or `Bioenergy' is energy that is derived from the decomposition of organic material. While biomass energy can be produced and consumed directly (as in using a wood fire for produced in nature every year by the decomposition of organic matter, both plant and animal. Although the natural gas that is commercially produced and sold in the US is 95 percent Methane, biogas has not, until recently, been viewed as a valuable energy source. Interestingly, the harnessing of biogas as a source of energy has been gaining a lot of attention for reasons that have nothing to do with its value as a fuel. Methane is a potent greenhouse gas that remains in the atmosphere for up to15 years. It is over 21 times more effective than carbon dioxide at trapping heat in the atmosphere. The capture and combustion of naturally occurring methane has been identified as a means to mitigate global warming. Federal, state and local governments have been passing laws and regulations to control this source of atmospheric pollution.

Although there are two general types of biological decomposition that can take place, aerobic (in the presence of oxygen) and anaerobic (in the absence of oxygen), the products of their decomposition will be very different. Aerobic decomposition produces carbon dioxide, ammonia, and other gases, along with a large amount of heat. Unless the heat is harnessed for useful purposes, the end product is not energy but fertilizer. Anaerobic decomposition, on the other hand, produces methane and hydrogen gas that can he used as fuel, and much less heat. The bi-product is a Fertilizer that is richer in nitrogen than fertilizer produced aerobic decomposition.

Anaerobic decomposition is a two-phase process that involves specific bacteria that feed on specific organic materials. In phase one, acid loving bacteria dismantle complex organic molecules into glycerol, peptides, alcohol, and simple sugars. When these compounds have been produced in sufficient quantities, phase two begins. A second type of bacteria then converts the first phase compounds into methane, carbon dioxide and other trace gasses. These methane producing bacteria are particularly sensitive to environmental conditions, such as temperature and humidity. If conditions are not favorable methane production can slow or halt.

One of four major sources of naturally occurring methane is animal manure. Avatar Alternative Energy is a California based company that has been developing technologies which offer a renewable source of energy while supporting sustainable farming practices through the development of small, scalable and economical anaerobic digester systems. On-farm digesters for converting manure to energy is not new technology. However, in the past these installations have typically involved large, permanent, site engineered, concrete structures.

Conventional wisdom has been that it required a 500 head herd of cattle to justify the cost of such an installation. Since the vast majority of farms engineered, continuous flow system that has the capability to manage animal waste odor and storage, while at the same time converting the waste into both useable energy and safe high value plant nutrients (fertilizer). Optional features to the digester/energy generation system can process effluents using biofilters, wetlands, and hydroponic growing systems to create additional marketable products for the farmer. The digester is modular in design and molded almost entirely from composites. Each unit accommodates the daily output of manure from 80 head of dairy cattle and can be scaled to address manure management issues for farms with 80 — 200 head of cattle.

These systems, which could be installed on virtually any farm that raises livestock, offer other benefits to society beyond those that have already been mentioned. Odor control is an important benefit in areas where urban sprawl is encroaching on agricultural areas. Farms with manure digesters can co-exist next to residential areas with little conflict. The ability to manage and recycle nutrients safely and effectively is also an important benefit. Digesters produce two high nutrient-content hi-products; one high in Nitrogen (N), and the other high in Phosphorus (P), that can be stored and used separately to provide maximum benefit as fertilizer. More importantly, in many areas of the country, such as the Chesapeake Bay watershed, uncontrolled nutrient runoff from Farms is a major source of water pollution.

Avatar produces its modular digesters in a plant in Burlington, Vermont. The assembled horizontally oriented unit is over 60 feet long and 6 feet in diameter, It is manufactured in 8 foot long bolt together sections that can be easily handled by existing on-farm equipment. Avatar molds the flanged sections on a collapsible rotating mandrel. Because the digestion process involves corrosive brine and hydrogen sulfide, a 50 mil corrosion resistant inner surface is created using a glass veil and vinylester resin. That is followed by four wraps of a bi-axel stitch mat and GP resin to create a 3/8ths wall thickness. In addition to the digester itself other components of the system are fabricated from a combination of PVC and composite. Avatar's CSO, Dr. Guy Roberts, hopes to see a manure digester on every manure producing farm. Federal regulations may mandate that outcome in the not too distant future. Needless to say, this would create a huge market for composites.

Biodiesel is the name given to a clean burning alternative fuel that is produced from renewable resources. Biodiesel has no fossil fuel derived content, but it can be blended in any ratio with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is easy to use, biodegradable, nontoxic, and essentially free of the sulfur and aromatic compounds that plague petroleum based diesel fuels. Biodiesel can be produced from any animal fat or plant oil such as soybean oil, through a refinery process called transesterification. This process is a reaction of the oil with an alcohol to remove the glycerin, which is a by-product of biodiesel production. Fuel-grade biodiesel must be produced to strict industry specifications (ASTIV1 D6751) in order to insure predictable performance. Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Biodiesel that meets ASTM D6751 and is legally registered with the Environmental Protection Agency is a legal motor fuel for sale and distribution. Raw vegetable oil cannot meet biodiesel fuel specifications, it is not registered with the EPA, and it is not a legal motor fuel. The term biodiesel refers to the pure fuel before blending with diesel fuel. Since the year 2000 production of biodiesel in the U.S. as grown from less than 2 million gallons per year to over 75 million gallons in 2005.. 

Producing biodiesel from oil or animal fat is a relatively straightforward process, as evidenced by the cottage industry that has sprung up around recycling spent cooking oil into diesel fuel. Essentially, when lye and methanol are added to heated vegetable Oil, two products settle out—glycerol and a diesel-like oil. The glycerol can be further separated into glycerin and methanol, in an era of recycled bio-diesel one can almost imagine the cravings for happy meals that will result from following diesel trucks too closely.

Because the production of biodiesel involves heat, along with either potassium hydroxide or sodium hydroxide, both corrosive substances, as well as other solvents and alcohol, there are numerous opportunities for composites in biodiesel refineries. Phil Hill of Biodiesel Technologies, in Collinsville, IL, one of the originators, and a supplier of farm-scale Biodiesel plants, believes that composites are the ideal material for the various tanks and columns that make up Biodiesel processing equipment.

The driving range of hydrogen fueled vehicles, usually powered by electricity generating fuel cells rather than combustion engines, depends on the vehicle design, and the amount and pressure of the stored hydrogen. Increasing either the size or pressure capacity of the storage tank will enable greater driving range. The current high cost of high-pressure compressed gas tanks has been essentially dictated by the cost of the carbon fiber that, because of weight and strength considerations, must be used as the tank's structural reinforcement. Thus, balancing physical size, weight, pressure rating, and cost has been a challenge in the construction of commercially viable compressed hydrogen tanks. Efforts are currently underway to identify lower-cost carbon fiber that can meet the required high pressure and safety specifications for hydrogen gas tanks without unduly compromising weight and volume requirements.

There is no doubt that fossil fuels will continue to become more costly in the coming years. That reality will continue to spur the development of renewable energy sources, which in turn will lead to many opportunities for composites molders. It is also worth rioting that the diminishing supply of fossil fuels will create some interesting challenges for the composites industry in regard to resin feed stocks. But that is a topic for another time.