At the bottom, you can see the flows to Residential, Commercial, and Industrial. Notice how the three are dwarfed by that big arrow on the top right labeled ''Conversion Losses." What exactly is conversion losses? Take this explanation from the report:
Energy Consumption by Sector
Note. Electrical System Energy Losses. Electrical system energy losses are calculated as the difference between total primary consumption by the electric power sector—see Table 2.1f—and the total energy content of electricity retail sales—see Tables 8.9 and A6.Most of these losses occur at steam-electric power plants (conventional and nuclear) in the conversion of heat energy into mechanical energy to turn electric generators. The loss is a thermodynamically necessary feature of the steam-electric cycle. Part of the energy input-to-output losses is a result of imputing fossil energy equivalent inputs for hydroelectric, solar, and wind energy sources, since there is no generally accepted practice for measuring those thermal conversion rates.
In addition to conversion losses, other losses include power plant use of electricity, transmission and distribution of electricity from power plants to end-use consumers (also called "line losses"), and unaccounted for electricity. Total losses are allocated to the end-use sectors in proportion to each sector's share of total electricity sales. Overall, approximately 67 percent of total energy input is lost in conversion; of electricity generated, approximately 5 percent is lost in plant use and 9 percent is lost in transmission and distribution. (2005 Annual Energy Review, Page 102)
The conversion losses are almost equal to all the coal and natural gas used to generate electricity. That is a huge amount of waste! Go ahead, open it up and take a good look at that energy flow diagram. Now there's your Global Warming problem.
So technically, we can switch to nuclear and renewable energy, provided we can get a grip on the conversion losses. That is not going to happen any time soon, but at the very least, any improvement in the efficiency of power generation and transmission will result in either less coal used, or an increase in the amount of electricity we can generate for the coal that has been consumed. That means that older less efficient, polluting plants can be retired with much more efficient, cleaner and smaller power plants. The current coal process itself is so inefficient that it is in our best interest that the process be improved. Think about it. Two of every three tons of coal are wasted. If we must use steam turbines to generate electricity, then why not use nuclear since conversion losses in nuclear power plants do not contribute to global warming.
There is lots of talk about 'alternative energy.' Looking at the graph above, I would think the nation could drastically reduce its demand for oil and coal if we can reduce the amount of energy that is lost in the conversion process. How hard is it to improve efficiency? It can be easier than you think. Part of the problem is that it really has not been addressed in the past because the fuel was so cheap that it was much cheaper to just burn more coal than to improve efficiency. This resulted in no real serious effort to improve the process.
Since the current system is SO INEFFICIENT, it is possible to find all sorts of small ways to improve it. Luckily, the research on how to do this has already been done:
Advanced coal-fired, power-generation technologies can achieve significant reductions in CO2 emissions while providing a reliable, efficient supply of electricity. Significant improvements in reducing CO2 and other emissions have been demonstrated via efficiency improvements and cofiring of coal and biomass.
Achieving the efficiency improvements and reducing emissions must be accomplished in a cost-effective manner. While current power plant efficiencies are about 33%, increasing efficiencies ultimately to 60% or more will reduce CO2 emissions by more than 50% per unit of electricity. Future development of CO2 sequestration could reduce carbon emissions to near-zero levels. - US Climate Change Technology Program (Links to PDF Document)
Part of improving the efficiency of power generation will require new power plants. Other improvements can be applied to the existing infrastructure, such as making use of the waste heat that normally goes right up the stack as exhaust gas. In many cases heat exchangers or 'waste heat' boilers can reclaim some of that energy.
Some factories, like paper mills, are installing the technology to take advantage of the waste heat generated in their production processes to generate electricity as a side product, which in turn is used to power the plant.
A new power plant is very expensive, so that the improved efficiency must cover the cost of building the plant. Luckily, research is being done to improve the efficiency of power generation. This program is called Vision 21, the Ultimate Power Plant Concept.
Vision 21 is a futuristic energy concept unlike any power plant that exists today.
Under development by the Department of Energy's Office of Fossil Energy, the concept envisions a virtually pollution-free energy plant. Unlike today's single purpose power plants that produce only electricity, a Vision 21 plant would produce multiple products - perhaps electricity in combination with liquid fuels and chemicals or hydrogen or industrial process heat. It also would not be restricted to a single fuel type; instead, it could process a wide variety of fuels such as coal, natural gas, biomass, petroleum coke (from oil refineries), and municipal waste. It would generate electricity at unprecedented efficiencies, and coupled with carbon sequestration technologies, it would emit little if any greenhouse gases into the atmosphere.
TECHNOLOGY GOALS - Efficiencies
- Coal-fueled: >60% HHV
- Gas-Fueled: >75%
- Combined Heat & Power: 75-80% thermal Emissions
- Air/Wastes: Zero
- CO2: Zero (with sequestration) - DOE
We can think about Being Green or we can Be Greener!High Effeciency Engines and Turbines - DOE (PDF)
Electricity Flow, 2005