II What are the alternatives and what are their characteristics. Part 2 of three parts.
By S. Tom Bond, Retired Chemistry Professor & Resident Farmer, Lewis County, WV
Waste products are a huge, largely unrecognized, problem with burning hydrocarbons. Originally it was seen that coal could be shipped to the cities and electricity generated there more efficiently – trains hauling coal to the city would take less energy than is lost in long distance transmission lines.
But long ago the decision was made to leave the dirt of conversion of coal to electricity in the rural areas where coal is mined, rather than bringing it to the cities where it is used. Removal of dust from the gases going up the smokestack and later removal of some of the gases, was a huge success story at one time.
All hydrocarbons are the remains of plants that lived long ago. With solid and liquid hydrocarbons (coal and oil) these remains contain not only hydrogen and carbon, but other elements in the plants, primarily sulfur, phosphorus, nitrogen, which leave as gases, as well as silica sand and metals. In coal these last items become fly ash, which must be stored (forever) or used in a manufacturing process.
The principal advantage of oil in use is its liquid nature, which makes it easy to handle, and the absence of solid waste, like fly ash. However the sulfur, phosphorus and nitrogen are found in oil and go into the exhaust gases.
The huge advantage of natural gas is that atoms heavier than carbon are relatively rare. Pure methane, CH4 is a very light weight molecule, whereas phosphorus, sulfur and nitrogen compounds are much heavier; and compounds containing them sort out easily. So no sulfur, phosphorus or nitrogen oxides result from burning gas, but nitrogen oxides can result from any flame burning in air (which is 78% nitrogen) at high temperature. This absence of contaminants is one of the principal appeals of natural gas.
Clearly, coal, oil and natural gas are hydrocarbons. In gases form they are greenhouse gases and when burned become carbon dioxide and other greenhouse gases. A real problem for climate change.
Present day alternatives. Fission reactors. These are based on heavy elements like uranium and thorium. The fuel is abundant, with the supply adequate for 30,000 years at the present rate with the use of “breeder reactors.” High technology is involved, and frankly the public is “psyched-out,” as the expression goes, about radioactivity. That is no wonder, since their education about radioactivity is not derived from objective formal education, but largely from the media, on behalf of the hydrocarbon industry, which has fought nuclear tooth-and-nail because it is competition.
There is a waste disposal problem with fission, but it is concentrated, not dispersed over the landscape as is the waste from hydrocarbon use, and it can be kept together. The actual tonnage is small for the amount of energy obtained. However, the radiation is very long lasting, although it slowly decays over time. A depository must be found that is stable over a geological time span. Fission is considered unsafe for cities, a disadvantage for maximum usefulness (see below). It is considered suitable for some very large navy ships and for submarines, in part because so little fuel is needed that resupply takes place infrequently. Other navy ships require huge amounts of fuel, and special tankers are designed to go with them to the areas where they might need to fight. Nuclear ships do not have that disadvantage.
Nuclear power plants sometimes must be slowed when the water for cooling becomes too hot – not good for a warming climate world. After the Japanese experience, it is obvious they should not be placed on the ocean shore, even disregarding increasing sea levels.
A second alternative is using wind power. These generators are becoming familiar on mountain ridges and in the windy plains. Today’s wind turbines can approach 80% of the theoretical limits of the power that can be extracted from wind, and provide perhaps 3 megawatts of power.
Blades must be large, and the further up into the atmosphere the blades reach, the more power is available. Little windmills are less efficient. Very careful attention must be paid to aerodynamic design, and the generators are designed for long use and minimum maintenance. Nevertheless failure can be spectacular.
Since wind power occurs in remote places, extensive new connections are needed between populated areas and the places where it can be obtained. There are complaints about birds and bats which are attracted to them and killed. The output varies with wind speed, so other sources, or power storage, is needed for the low output times. The input energy cost is zero, which makes them attractive.
Another viable alternative is solar power. It also has variable output, according to time of day and clouds, so use for sole source of electricity requires batteries or some other storage. Solar is already the source of choice for small, remote needs, where an ordinary lead-acid (car) battery is sufficient for night or cloudy times. Things such as road signs, metering natural gas in transmission lines, electrical fences, and such are already best uses all over the world.
This article has a list of leading nations using of solar power, and also a map showing where solar energy is available. Solar power is a great hit in places with no distribution lines. In parts of Africa, it is important far beyond the size of the installed base. It provides recharges for cell phones, a little light at night, and radios. Also electric fences to protect villagers from wild animals. India is making great progress with solar in rural areas. In many places it is as cheap as conventional power now.
Energy radiated from the sun spans a considerable spectrum. The “trick” in engineering photocells is to get them to take up as much of the spectrum as possible. This is the basis of a lot of scientific work now, finding one or a combination of photocell materials which can harvest the maximum energy available. However room remains for improvement, the efficiency is now approaching 50%. The opportunity (and reward) for improvement is great. Once you have it installed, it is very cheap.
A great advantages of wind and solar are they do not take water for installation, and they do not use or produce contaminating chemicals on a huge scale. Capital cost is the entire cost, and negligible input energy cost.
Storage for night use and low input times is a problem with both wind and solar. Storage for large amounts of energy is almost non-existent. This is not a very large problem as long as sufficient other sources of energy are available, because they can be scaled up and down as wind and solar decrease and increase.
Pumped storage is the use of energy to pump water uphill to a lake, and then using the water to generate hydropower in “off hours.” It is very expensive and low efficiency. Several other kinds of storage have been explored: flywheels, compressed air, fuel cells, and other systems.
One of the greatest possibilities for the energy future is conservation. Insulation both for heating and cooling, more efficient light sources, more efficient transportation (both for personal use and for shipping), heat pumps, design improvements in computers (which use about 1/10 as much energy when turned off, but plugged in), more efficient irrigation, and building design.
Up to 75% of energy use in the United States would be saved with energy efficiency measures which would cost less than the energy saved, according to the Rocky Mountain Institute.
One of the most important factors in future use is to have power generation in cities where it is used. Remote power stations have a lot of waste energy which must be disposed of in the air or a river. Typically in the neighborhood of two-thirds of the energy in the coal is lost, with a similar thermal loss of nuclear plants. It could be used for space heating in houses and businesses and for some factory uses instead of being just dumped uselessly into the environment if the generating station was near the population using it.
Other energy economies are high speed trains, smart grids for electrical distribution, stopping lateral expansion of cities, more public transportation, and so on.
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