Transportation is another sector that has increased its relative share of primary energy use. This sector has serious concerns as it is a significant source of CO2 emissions and other airborne pollutants, and it is almost totally based on oil as its energy source. An important aspect of future changes in transportation depends on what happens to the available oil resources, production and prices. At present, 95% of all energy for transportation comes from oil. (more…)

Global energy consumption in the last half century has increased very rapidly and is expected to continue to grow over the next 50 years. However, we expect to see significant differences between the last 50 years and the next. The past increase was stimulated by relatively “cheap” fossil fuels and increased rates of industrialization in North America, Europe, and Japan; yet while energy consumption in these countries continues to increase, additional factors are making the picture for the next 50 years more complex. These additional complicating factors include the very rapid increase fuel economy in energy use in China and India (countries representing about a third of the world’s population); the expected depletion of oil resources in the not-too-distant future; and the effect of human activities on global climate change. (more…)

Renewable energy generators are devices that convert energy from its original form in the renewable energy source into electricity. Renewable energy generators that are most likely to be found in hybrid energy systems include wind turbines and photovoltaic panels. Some hybrid energy systems use hydroelectric generators, biomass fueled generators, or fuel cells. It should be noted that many renewable energy generators include rotating electrical machines acting in the generating mode, which is also called a generator. It should be clear from the context what is meant. (more…)

The characteristics and components of a hybrid system depend greatly on the application. The most important consideration is whether the system is isolated or connected to a central utility grid.

Central Grid Connected Hybrid Systems

If the hybrid system is connected to a central utility grid, as in a DG application, then the design is simplified to a certain degree and the number of components may be reduced. This is because the voltage and frequency are set by the utility system and need not be controlled by the hybrid system. (more…)

There are numerous possible applications for hybrid power systems. The most common examples are (1) remote AC network, (2) distributed generation applications in a conventional utility network, and (3) isolated or special purpose electrical loads.

The classic example of the hybrid energy systems is the remote, diesel-powered AC network. The basic goal is to decrease the amount of fuel consumed by diesel generators and to decrease the number of hours that they operate. The first addition to ‘‘hybridize’’ the system is to add another type of generator, normally using a renewable source. (more…)

The term hybrid energy system refers to those applications in which multiple energy unit conversion devices are used together to supply an energy requirement. These systems are often used in isolated applications and normally include at least one renewable energy source in the configuration. Hybrid energy systems are used an alternative to more conventional systems, which typically are based on a single fossil fuel source. Hybrid energy systems may also be used as part of distributed generation application in conventional electricity grid. (more…)

In this new century, there is considerable pressure on the top six automakers to reduce their environmental and ecological footprint calculation. The automaker that wins the race to build and sell the superior car will shape consumer preferences, thereby boosting sales and profits. The winning firm will fashion a corporate strategy that drives automobile emissions to near zero while simultaneously providing high levels of performance, safety, and comfort. (more…)

Because transportation is such a large contributor to global warming, both globally and in the United States, climate and energy experts say finding clean alternatives to gasoline is also key to replacing fossil fuels and slowing global warming. Just as there is debate and competing research about which type of alternative transportation fuel should be developed to produce electricity, however, there is also competition among possible new transportation fuels. So far, in the United States, significant funding has been put into two transportation technologies—ethanol and hydrogen fuel cells. Many energy commentators say cars powered by electric batteries are the technology closest to mass production capability, however. (more…)

With ethanol’s future uncertain, many commentators see the transportation debate evolving into a war between two other technologies—hydrogen-powered fuel cells and battery powered electric vehicles. Some alternative fuel advocates are putting their support behind hydrogen, the most abundant element on Earth. Water, for example, is composed of hydrogen and oxygen molecules. Hydrogen can be produced from water by electrolysis, which separates the oxygen from the hydrogen. It can be used to power hydrogen fuel cells for vehicles (or to provide heat and electricity for buildings). Hydrogen fuel cells work by recombining hydrogen and oxygen—a process that produces electricity, heat, and water. Hydrogen-powered cars, therefore, could be an ideal transportation solution—nonpolluting, zero-emission vehicles that release only water, a natural and completely safe waste product. Also, fuel cells are highly efficient and powerful, and unlike typical batteries, fuel cells will never lose their charge as long as hydrogen fuel is supplied.

Hydrogen fuel cell technologies, however, must overcome many stubborn challenges before they can become a practical source of energy. Perhaps the biggest obstacle is cost; it currently takes more energy to make hydrogen than is produced, and production relies on expensive catalysts made from platinum, a scarce metal. And like biofuels, hydrogen is currently made using fossil fuels, so it is not emissions-free. In addition, liquid hydrogen fuel is highly flammable and must be stored at very low temperatures or under very high pressure, making transport and storage difficult. Switching vehicles to hydrogen fuel cell power also would require building a whole new infrastructure similar to the chain of gas stations that currently dot the landscape. Researchers are hoping to find answers to these problems by searching for other types of catalysts, studying other ways to improve production, and developing better hydrogen storage options.

Hydrogen researchers, however, have been promising breakthroughs since the 1990s with little progress to show for their efforts. Many observers are thus coming to the conclusion that the hydrogen fuel cell is a technology that will not be perfected in the near future. As physicist and climate expert Joe Romm explains, “Neither government policy nor business investment should be based on the assumption that these technologies will have a significant impact in the near or medium-term.” The Obama administration apparently agrees; it submitted a budget for 2010 that sharply cut back on government support for hydrogen projects. U.S. Energy Secretary Steven Chu explained the administration’s problems with hydrogen technology:

Right now, the way we get hydrogen primarily is from reforming [natural] gas. That’s not an ideal source of hydrogen. . . . The other problem is, if it’s for transportation, we don’t have a good storage mechanism yet. Compressed hydrogen is the best mechanism [but it requires] a large volume. We haven’t figured out how to store it with high density. What else? The fuel cells aren’t there yet, and the distribution infrastructure isn’t there yet. So . . . to get significant deployment, you need four significant technological breakthroughs. That makes it unlikely

Congress promptly reversed President Obama’s decision, however, restoring more than $200 million to 190 hydrogen projects around the country.

The product gas can be burned in boilers to generate heat and raise steam, in internal combustion engines to generate electricity and heat at small to medium scale (from a few kilowatts to a few megawatts), and in gas turbines to generate electricity (Brayton cycle) and heat at small to large scale. In large-scale systems using gas turbines, the exhaust gas from the gas turbine can be used to raise steam in a heat recovery steam generator to generate additional electricity using a steam turbine (Rankine cycle), resulting in combined cycle operation. (more…)