August 2008 Archives

Global warming is real and it is linked to increasing levels of carbon dioxide (CO2). Spinning pollution (CO2) into formic acid and then to methanol will solve the problem of global warming through CO2 reduction and the problem depleting fossil fuels through the creation of methanol as an alternative automobile fuel. Methanol is not only a very valuable fuel but also an important starting material for production of many precious organic compounds. The CO2 levels can be mitigated by three methods: photochemical reduction, electrochemical reduction, and hydrogenation using a hydride source.

Production of hydrogen by splitting water into hydrogen and oxygen is a topic of intense research. Hydrogen is used in fuel cells for energy in automobiles instead of gasoline/ methanol/ ethanol. Hydrogen is an environmentally friendly fuel because hydrogen use in automobiles produces only water vapor as exhaust; that is, no pollution. However, storage and transportation of hydrogen is a concern. Studies are underway to prepare hydrogen storage materials and safe methods of hydrogen transportation.

Currently, hydrogen is produced by a steam reforming reaction utilizing methane and water with many catalytic operations. In this process hydrogen is generated along with carbon monoxide (CO) as an impurity; removal of CO from hydrogen gas requires use of expensive catalysts. Thus the best method to generate hydrogen is splitting water.

Different research groups (Nocera's group at MIT, Fujita's group at BNL, etc) are pursuing ways to produce hydrogen from water by understanding photosynthesis: Photo system I and Photo system II. In photo system II plants utilize an oxygen-evolving complex to produce hydrogen ions and electrons. In a decade or so production of hydrogen from water will be a reality, provided there is strong commitment from the federal government to encourage this research.

In conclusion, effective reduction of CO2 to methanol, splitting of water into hydrogen, tapping solar energy using viable photovoltaic cells, augmenting wind power by increasing the number of windmills, safe and effective generation of nuclear energy by nuclear reactors taking into account the efficient methods of recycling spent fuel will unravel our energy crisis and human survival.

--------- Dr. Varattur Dayal Reddy
The City University of New York

Now I want to consider how the "free" energy from the earth gets distributed within the house. For this to occur, the heat that has been absorbed by the water in the pipe while flowing through the earth must be transmitted to the air within a home.

There are two loops of pipe in this system: one loop external to the house and one loop internal to the house. The external loop transfers heat energy from the earth to the water in this pipe, while the internal loop (containing another fluid) helps transfer this energy to the air within the home. The internal loop has two distinct sections: one section interacts with the external loop and the other section interacts with an air handler.

As heated water returns from the outside loop, heat is transferred to the internal loop in the blue area (see diagram above from www.geoexchange.org). When this occurs, the fluid in the internal pipe expands. This expanded fluid is passed into the red area where it is compressed. Upon compression, the fluid releases heat to the surrounding air. A fan then distributes this heated air to the rest of the house via ductwork.

For cooling in the warmer months the process described above is reversed: the outside air is hotter than the earth and the red and blue portions of the diagram are interchanged. This is the basic process. Of course, work must be done to pump the fluids through the pipes, to compress the fluid in the internal loop, and to operate the fan to distribute the heated or cooled air to the house. It would be nice if this work could be performed by electric motors powered by a solar cell system of adequate capacity.

I have been house hunting for about a year now and given the rising costs of oil I have started to pay very close attention to my future home's heating system. Long Island, at least the area where I live, predominantly heats with oil. Of the available types of heating systems, I would prefer to have a natural gas furnace, but I would not choose a house solely for its mode of heating; school districts, lot size, house size, etc., play a large role.

One of the last houses I looked at seemed to offer me a nice opportunity: all the other parameters for choosing a home were fairly well satisfied but the oil burner was in pieces on the basement floor. Not only was the burner in pieces, it looked like an Industrial Revolution heirloom. Thus, the burner was not worth fixing -- it needed to be replaced. Well, I thought, if I have to spend thousands on a new burner, why not consider a different type of heating system. In a flash I had my answer: a geothermal heat pump. This, of course, has lead me to consider the impact of this choice from a variety of angles.

First, I want to consider the basics of a geothermal heat pump. Geothermal heat pumps are based on the empirical fact that the temperature of the Earth (as shallow as 4-6 feet) below the surface stays fairly constant year round. In the basic closed-loop model, a length of fluid-filled pipe (usually water or water plus a biodegradable antifreeze) is buried either vertically or horizontally in the ground near your house. The fluid in the pipe exchanges heat with the surrounding earth.
To see a schematic view of the horizontal variety click here: View image. In the image the pipe depth varies between 4 and 6 feet (image source: U.S. Department of Energy).

The only thermodynamics needed here is the everyday notion that heat energy flows naturally from hot objects to cool objects. In the summer, the ambient temperature inside a house is hotter than the temperature in the ground where we have buried our pipes. Thus, heat from the house is transferred to water in the pipes inside the house, i.e., the water in the pipes heats up and the air in the house cools down until they reach the same 'equilibrium' temperature. This water is then pumped outside where it will exchange heat with the cooler ground, i.e., the water will now cool down as the earth around the pipe heats up. This cooled down water now returns to the house to repeat the process. In the winter, the above process is reversed.

One thing to keep in mind is that the ground temperature stays constant because the earth is gigantic in comparison to the house being heated. In practice, this means that the ground where you have buried the pipes for the heat pump can absorb or emit a seemingly infinite amount of heat energy, with a very small change in temperature, compared with the very small volume of air in an ordinary home.

The idea of an object's life-cycle energy consumption has started to raise its, perhaps ugly, head in many discussions about alternatives to fossil-fuel energy. Such a viewpoint takes into account not only the carbon footprint of an object during its ordinary use, but also the footprint left during its production and its disposal.

On this note, conservation is easy to understand: producing and disposing of something like a light bulb do not come into play, I just use it less so the footprint is reduced in absolute terms. Efficiency is not so straightforward. If my compact fluorescent lights have a significantly increased footprint for their production and disposal this may be enough to outweigh any reduction in their footprint gained during their operation. How would I go about comparing the life-cycle footprint of two such products? This raises the specter of complexity, which underpins all our energy calculations.

Consider the production (i.e., growing) and transportation of food grain. In practice, grain requires energy for its production and for its transportation. This is only part of the story, however, as most of us do not buy wheat from the grocery store. There are further energy calculations to be done to get something like wheat into my house as a final food product. We ignore that portion here. A study by Chen and Kobayashi, A Study on Comparison of Life Cycle Energy Consumption and CO2 Emission in Grains Production--Transportation in Japan and Heilongjiang Province of China, reveal substantial differences in the energy costs for four types of grain between Japan and China. Here, energy complexity resides not in the product itself but in the mode of production and distribution. One might assume, or maybe not, that using 100 people to plant and grow a field of wheat would require less energy than farming the same area with a tractor. But do we really know this until we calculate the energy consumption of both methods (including C02 emissions)?

On the other side of the coin is complexity in the product itself. Consider the production of ethanol from corn. Patzek, from the University of California, Berkeley, reviewed the many components required in the production of ethanol from an energy consumption perspective. His analysis, found in Thermodynamics of the Corn-Ethanol Biofuel Cycle, suggest that:

it appears that if the corn-ethanol exergy (available free energy) is used to power a car engine, the minimum restoration work (energy needed to restore non-renewable resources consumed in production) is about 6 times the maximum useful work from the cycle. This ratio drops down to 2 if an ideal fuel cell is used to process the ethanol.

Although complex, 'whole picture' calculations such as the two mentioned above are certainly necessary in order to make truly 'green' decisions.

Would this be like Godzilla versus Mothra? Or maybe it is more like Ultraman pitted against Maxwell's demon? Who is who, though?

The notion of efficiency conjures up the image of a heat engine and the equation of Sadi Carnot. More recently, however, it makes me think of compact fluorescent lights like this one

The following quote from the ENERGY STAR website recalls my last entry:

If every American home replaced just one light bulb with an ENERGY STAR qualified bulb, we would save enough energy to light more than 3 million homes for a year, more than $600 million in annual energy costs, and prevent greenhouse gases equivalent to the emissions of more than 800,000 cars.

The point here is that many of the new technologies allow people to do the same thing as before (e.g., light a room) but to consume less energy to do it. In short, efficiency means accomplishing the same task as before but in a manner that transfers more of the input energy to useful output. Thus, it is not so much "efficiency versus conservation" as "efficiency with conservation" to achieve an even greater leap forward.

Let's consider a somewhat ridiculous scenario for a moment and assume that every residence in America has only one 100 W light bulb. To push this further, I will assume that every residence turns this one light bulb on for only one hour each day.

Pause for a moment and picture your current residence void of all electricity-consuming gadgets save for this one lonely bulb hanging from the ceiling. This is not the most representative picture of the developed world, is it? I continue.

I now would like to know how many electric generating stations would be needed to fulfill this imagined country's electricity needs.

Operating a 100 W bulb for one hour requires 0.1 kW-h of energy, which is delivered via the electric grid to each and every house. According to the U.S. Census Bureau there were 106,261,000 occupied regular residences in America in 2001. With each house having only one bulb, the energy needed to light the bulbs in all the houses is the amount of energy for one bulb multiplied by the number of homes: 0.1 kW-h X 106,261,000. This comes out to be about 11 million kW-h of energy per day, which is about 4 billion kW-h per year.

An energy demand of this size could be met by a 600 MW generating station. For comparison, the largest generating station running on fossil fuel in New York State has a capacity of 2324 MW.

On the flip side then, we would need one fewer generating stations in the US if each household reduced the use of one 100 W bulb by one hour. Now think of two bulbs, etc.

Granted, this is not the complete solution but think of the items in our houses that are always on: fridge, door bell, alarm clocks, televisions, computers, telephones,... As Billy Bragg sang, albeit not about the same topic, a little conservation by a large number of people would be a "great leap forward."

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