The term alternative energy is referred to the energy produced in an environmentally friendly way (different from conventional means, i.e., through fossil-fuel power plants, nuclear power plants and hydropower plants). Alternative energy considered in this dissertation is either renewable or with high energy conversion efficiency. There is a broad range of energy sources that can be classified as alternative energy such as solar, wind, hydrogen (fuel cell), biomass, and geothermal energy. Nevertheless, as mentioned in the previous section, at present the majority of the world electricity is still generated by fossil fuels, nuclear power and hydropower. However, due to the following problems/concerns for conventional energy 5 technologies, the renewable/alternative energy sources will play important roles in electricity generation. And, sooner or later, today’s alternatives will become tomorrow’s main sources for electricity.
- Conventional generation technologies are not environment friendly
- Conventional energy sources are not renewable
- The cost of using fossil and nuclear fuels will go higher and higher
- Hydropower sources are not enough and the sites are normally far away from Load centers.
- Political and social concerns on safety are pushing nuclear power away.
Advantages of Renewable powers:
1) Renewable energy resources are not only renewable, but also abundant. The total solar energy from sun in a day at the earth surface is about 1000 times more than the all fossil fuels consumption.
2) Fuel cell systems have high energy efficiency: The efficiency of low temperature proton exchange membrane (PEM) fuel cells is around 35-45%. High temperature solid oxide fuel cells (SOFC) can have efficiency as high as 65%. The overall efficiency of an SOFC based combined-cycle system can even reach 70%.
3) Renewable energy and fuel cell systems are environmentally friendly: From these systems, there is zero or low emission (of pollutant gases) that causes acid rain, urban smog and other health problems; and, therefore, there is no environmental cleanup or waste disposal cost associated with them.
4) Different renewable energy sources can complement each other: Though renewable energy resources are not evenly distributed throughout the world, every region has some kinds of renewable energy resources. At least, sunlight reaches every corner in the world. And different energy resources (such as solar and wind energy) can complement each other. This is important to improve energy security for a nation like the U.S. which is currently dependent on the foreign energy sources.
These renewable/alternative power generation systems normally have modular structure and can be installed close to load centers as distributed generation sources (except large wind and PV farms). Therefore, no high voltage transmission lines are needed for them to supply electricity. In general, due to the ever increasing energy consumption, the rising public awareness for environmental protection, the exhausting density of fossil-fuel, and the intensive political and social concerns upon the nuclear power safety, alternative (i.e., renewable and fuel cell based) power generation systems have attracted increased interest.