The Emerging Energy Industry
Upgrading the old, developing the new
By Robert B. Aronson
Once the present financial problems start to settle down, one of the opportunities for the manufacturing community waiting in the wings is the growing "energy industry." Manufacturers may benefit in two ways. First, there can be an operating overhead savings by taking advantage of energysaving equipment such as machine tools that use less power, and monitoring in-plant energy use. The second, and stronger potential benefit, is the manufacture of upgraded and new products this new industry requires.
This work is trickling down the chain to a variety of suppliers, For example, the petroleum industry called on second-tier suppliers to resolve a key problem. In offshore well drilling, pipe strings extend miles below the surface. With millions invested in that string, the threaded pipe joints are exceptionally critical. To make these threads Emuge Corp. (West Boylston, MA) provided a series of thread mills and insert mills that are designed to solve problems of leaking pipe joints in the petroleum and natural-gas industries. Emuge is said to produce threads of the dimensions and finish that eliminate problems associated with machine tapping or lay-down threading methods.
Energy conservation is one of the key programs of the Department of Energy's Industrial Technology Program (Washington, DC). One of the DOE efforts looks for wasteful energy use in existing plants. Teams do energy audits of plants then make recommendations. "We have been able to realize an average energy use saving averaging 8–15% in each plant through this work," explains George Windholtz, project director.
"Some actions are simple, such as eliminating unnecessary, constantly idling, backup equipment," he says. "But if the problem is an inefficient 60-year-old boiler, changes may be more drastic. We also train company personnel in the use of relevant energy-monitoring software."
Other efforts work to improve industrial processes. One such project involves making titanium sheet by rolling instead of the traditional vacuum-melting process.
The process under development uses new, lower-cost titanium powder. It is roll compacted and directly fabricated into sheets that can be extruded or pressed-and-sintered to create various forms and parts. This process is said to have the potential to reduce the amount of energy required to make titanium parts from powders by up to 50%.
Solar and wind energy, classified as intermittent power, are potential sources of tremendous energy. But, the long-standing challenge is converting that energy into usable power.
Basically, a solar cell, or more formally, a photovoltaic (PV) device, delivers energy when a photon of solar energy strikes a semiconductor material and drives off an electron. This power source has been available for decades, but the cell's low generating capacity has kept them in the category of emergency, or backup power source. However, efforts to find alternatives to nonrenewable fuels have made solar cells a major focus of R&D.
Manufacturers are now offering solar power systems in three categories:
- Multimegawatt systems supplying large facilities or towns.
- Commercial systems that supplement grid power or are the only power source for a single building or plant.
- Single residual systems to power a single home or farm.
The solar power units come in three general configurations.
- Flat-Plate PV systems are the most commonly used designs at present. They can be stationary or mounted on a tracking device. A typical flat-plate module design has a metal, glass, or plastic substrate holding the encapsulated cells. The panel top has a transparent plastic or glass cover.
- The concentrator design "gathers" sunlight in a large focusing system that concentrates light on the cells, instead of letting the sun shine directly on a group of cells. This design is potentially the least costly of those being investigated, because it uses materials such as plastic lenses and metal housings to capture the solar energy, and uses fewer, and smaller, cells than flat-plate designs.
- A non-photocell version of the concentrator uses a large field of reflectors to direct sunlight to a tower-mounted boiler. Special fluids in the boiler function much like water in a conventional boiler. The boiler supplies a high-pressure fluid to drive generators. This design requires a large land area and would be most practical in installations used to supply large quantities of power such as for a city's power supply.
Among the main photocell types crystalline silicon cells have about 85% of the market. "They have a conversion efficiency of around 40%," explains Scott Stephens, of the Solar Energy Technologies Program (Washington, DC). "The downside is that the cells are relatively large and heavy.
"Most of the other contenders are thin-film designs and are based on a variety of materials," Stephens says. "Cadmium telluride thin-film cells look promising, and can be manufactured at a lower cost than silicon cells, but are not as efficient. Also of interest is the copper indium, gallium selenium cell. This design offers improved conversion efficiency and low cost production.
"Major areas of research are working to increase the efficiency of the devices, which is primarily done at the cell level.
"Researchers are also looking at more transparent glass and improving the contact between the cell and the buss bar, and more efficient heat sinks to lower the operating temperatures," Stephens concludes.
The technology for manufacturing glass used as the substrate for most solar cells is well established, although research continues to find better cell materials. Pilkington is a major manufacturer of the glass that ultimately becomes part of a solar cell. "We make glass with a transparent conductive oxide (TCO) coating. It is a specialized glass that not only protects the cell but provides a mechanism to conduct current between the cell and the buss," explains Stephen Weidner, VP of Pilkington North America, (Toledo, OH). "It acts as a flat transparent wire that pulls current out of the semiconductor material and is the first step in making the cell. We use a pyrolitic deposition process to apply the TCO coating which then goes to a cell manufacturer for further processing."
Windmills are now being used extensively for electric power generation. These wind-powered turbines generate an estimated 94 GW worldwide, or about 1% of worldwide power need.
The US reportedly is the world's leading producer of electricity from wind power and the fastest growing wind-power market. According to a DOE report, wind power could generate 20% of US electricity by 2030. As of 2008, the US had the capacity to deliver 22.06 GW by wind power, which is just about 1% of this country's electricity supply. As of January last year, the installed capacity in the US was 16,904 mW.
A large number of manufacturers are targeting the smaller wind power systems designed for individual locations, such as a farm or small village. For example, the design offered by Wind Turbine Industries Corp. (Prior Lake, MN) has a 31' (10-m) diameter rotor that drives a synchronous three-phase alternator operating from a tower, typically 80–120' (21–37-m) tall.
Most of these turbines operate in the Midwest where winds are stronger and more consistent than elsewhere in the nation. The unit needs a specific cut-in speed to function and operates best in 12–13 mph (20–21 kph) winds. At those speeds, the unit has the potential to deliver between 30,000–35,000 kWh annually.
On the other end of the size spectrum are larger companies such as GE Electric (Atlanta), which is North America's largest wind-turbine manufacturer. Their wind turbines are rated at 1.5–3.6 MW. GE's best-selling unit delivers 1.5-MW. At present, over 10,000 of these units are operating in 19 countries.
For the European market, GE offers a 2.5 MW wind turbine, which is designed for regions challenged by land constraints. It is GE's most advanced wind turbine technology, and uses a 100-m diameter rotor.
Siemens Energy, one of the world's largest wind-turbine manufacturer, currently offers 2.3 and 3.6 MW units. The SWT-2.3-93 is most used by utilities and other large developers. The SWT-2.3-93 version provides superior economy at sites with moderate wind speeds.
These turbines automatically start when the wind reaches about 3–5 m/sec. The output increases approximately linearly and reaches rated power with wind speeds of 13–14 m/sec. If wind speed exceeds 25 m/sec, the turbine is shut down by feathering the blades.
Coal currently supplies more than 30% of our nation's energy through steam-driven turbine generators. Although coal is plentiful world wide, burning it produces CO2 and ash.
Coal burning is blamed for much of the global-warming phenomena because of its effect on the atmosphere.
It is possible to remove most of the sulfur dioxide and particulate emissions from coal-burning power plants. But there are still problems to be addressed concerning CO2 and radionuclides. Technologies do exist to capture and store these materials, but high cost has limited their extensive use. Significant improvements have been made in fuel utilization, and some boiler designs now have an effiency greater than 90%.
Nuclear power plants have been in disfavor in the US for some time due to the early association with nuclear weapons, and the real dangers of failure. Its acceptance has however grown in most of the rest of the industrialized world. Now, because of concerns about nonrenewable energy sources, nuclear power may be getting a second chance in this country.
Under evaluation are five reactor designs. Currently two have received design certification approval by the US Nuclear Regulatory Commission. Other designs are being reviewed. This includes the Economic Simplified Boiling Water Reactor, the Evolutionary Power Reactor, and the Advanced Pressurized Water Reactor versions.
Nuclear plants have dramatically improved their reliability. The percentage of time that a plant is running at full capacity is more than 91% today, the highest such percentage of any generation source.
Because of a set of fuel reliability guidelines developed by The Electric Power Research institute, the number of US plants with fuel failures in 2008 is at a historical low.
Radioactive material storage and/or disposal, is another issue of public concern. Reportedly, most reactors can easily store all of the fuel used over the reactor's lifetime on their site.
A long-term geologic repository has been designated by the US government at Yucca Mountain, NV. If licensed for operation by the NRC, used nuclear fuel could be emplaced underground starting sometime beyond 2020.
Most of the auto industry is scrambling to develop cars that reduce their reliance on petroleum-based fuel. The two options that are being developed include improving the internal combustion engine to use less fuel and designing propulsion systems that depend partially or totally on batteries, electric motors and power electronics.
Energy-saving technologies for internal-combustion engines can take many forms. For example Dave Lancaster, of GM's Powertrain Engineering notes, "Reducing mass through material substitution reduces fuel consumption by reducing the energy required to propel a vehicle. We use lightweight components such as aluminum blocks in many applications, but to carry the ever-increasing structural loads as engine output rises you have to go to thicker sections, which decreases aluminum's weight advantage.
"In gasoline engines, we have been rolling out direct injection across our engine portfolio where fuel is metered directly into each cylinder at around 3000 psi instead of port-fuel injection that puts fuel into the intake port," says Lancaster. "This allows higher compression ratios with resulting improvements in power and greater fuel economy. Because better atomization leads to greater vaporization, it is not necessary to enrich the fuel mixture when starting."
As little as 10 mm3 or less of fuel are injected per cycle, which is very difficult to meter, but now possible, thanks to microprocessor control and improved injector technology. In addition, the fuel shot can be delivered in separate pulses. This allows greater combustion control and increased fuel economy.
Aside from acceleration and towing operations, most passenger cars use less than 25% of an engine's power at cruising speed. At freeway speeds, less than 25 hp (18.6-kW) is needed to keep many cars moving, although on a hot day, air conditioning loads can add to that significantly. Gasoline engines running at these power levels are usually highly throttled, which means that considerable energy is lost pumping gases through the engine. One way to reduce this loss is Active Fuel Management (AFM) technology in which an engine automatically runs on half of its cylinders at light load. The lifters on some cylinders of a pushrod V-configuration engine are deactivated. Because only half the cylinders are active, intake manifold pressure rises, and the energy to pump gas through the engine is reduced.
In GM's V8 engines with AFM, performance on EPA tests show a 5.5%–7.5% reduction in fuel consumption. Under some conditions, improvements of as much as 12% are possible.
Biofuels is another research area. According to some estimates, sustainable biofuels made from non-grain sources could offset future vehicle energy demand 35% by 2030. This fuel would be made from organic materials such as woody biomass, agricultural waste, and nonfood crops grown specifically for biofuels use.
GM has several projects in this area and its researchers believe biofuels, specifically E85 ethanol, is the most significant near-term solution to offset rising vehicle energy demands and reduce greenhouse gas emissions. E85 is comprised of 85% ethanol and 15% gasoline.
Hydrogen is another example of an alternate energy source that will help reduce reliance on petroleum fuel. According to Lancaster, "Although hydrogen can be used as fuel in a conventional engine, there are issues with engine knock and reduced power that lead us to the conclusion that the fuel cell is the best technology for using hydrogen fuel. We are fully committed to hydrogen fuel cells as a long-term vision and a key part of our efforts to bring about the electrification of the vehicle and significantly reduce our reliance on petroleum." One of the misconceptions about hydrogen, is the public's perception that hydrogen is unsafe, or 'the Hindenburg Effect.' However, hydrogen, like petroleum, can be safely controlled. "We are committed to have a fuel cell propulsion system by 2010 that will be competitive at high volumes. The real focus when it comes to fuel cells is the development of a hydrogen infrastructure," says Lancaster.
The main goal for battery development is drive power for vehicles. Early attempts at electrically powered vehicles used lead-acid batteries. Because of the weight and recharge restrictions, they were only practical for short travel distances, and low-power applications such as golf carts.
Vehicle drive batteries have a different set of tasks. They are built for moving the vehicle down the road. They require high power, high energy, and long life, and are expected to power three stages of vehicle development.
A basic hybrid gas-electric system combines a battery-powered electric motor and an internal combustion engine. For example, GM's Flex Propulsion System has a 53-kW direct engine-mounted generator and a four-cylinder 1-L engine. The gasoline engine kicks in when the battery needs to be recharged or when the vehicle needs additional power for accelerating. When cruising, the gasoline engine is dormant. The vehicle's batteries are not designed to be replaced. They are recharged by the engine and regenerative braking. Dozens of basic hybrid vehicles are currently on the road.
The plug-in hybrid vehicle, in which the battery power is the main power source, has an internal combustion engine as reserve for when the battery is recharging. The two differences between the plug-in and basic hybrid are a larger battery pack and the ability to recharge batteries with common household electricity. Newer charging systems allow quick recharging at special sites or the user's home with special outlets.
The totally electric vehicle would have no backup power source and rely completely on rechargeable batteries. Because of their limited range (e.g., Chevrolet Volt, 40 miles) establishing a recharging network is a major challenge for this concept.
Presently the US is most strongly involved in the hybrid-design phase with a number of these cars now on the road. The most commonly used battery for today's hybrids is the nickel-metal hydride. Many other designs are under development, but the lithium ion is currently thought to be the most practical. It holds twice as much energy as a lead battery, has a longer life cycle, and requires no maintenance.
"Lithium-ion is a family of materials, each with a different chemistry and manufacturing requirements, and is the basis of the most promising of the available battery designs," according to Mike Andrew, HEV Battery Systems, Johnson Controls Inc. (Milwaukee). "It offers a high level of electric activity, is lightweight and delivers a high voltage. Another plus is that it can deliver the same amount of energy over a wide range of discharge rates.
This article was first published in the February 2009 edition of Manufacturing Engineering magazine.