Energy from Heat: A Variety of Options

Nuclear energy from the heat of fission: Carnival of Nuclear Energy #53 Cool Hand Nuke...Check out the latest carnival of nuclear blog news and views.

New developments in nanoantennas to harvest solar infrared radiative heat...NewEnergyandFuel

Siemens combined cycle turbine technology achieves 60% efficiency...NextBigFuture Combining gas turbines with steam turbines allows the extraction of a larger amount of the heat energy potential contained in coal, gas, biomass . . . . and even nuclear fuels in advanced high temperature gas-cooled reactor designs.

If you add thermal electric technology to combined cycle technology -- to harvest as much waste heat as possible -- you could increase overall efficiency of energy from heat.

Most contemporary energy and power comes from the use of heat energy -- either energy of combustion or energy from nuclear fission. This will be the case for many decades more -- even with the growth of fuel cells, photovoltaics, and other alternative methods of power generation. Advanced biofuels and enhanced geothermal power will continue to utilise heat power and heat engines.

As technology improves, it is crucial for society to make the best use of any energy assets which may be available, rather than to follow the Obama energy starvation approach. Energy is the life's blood of advanced societies. Any persons or groups that are dedicated to the strangulation of energy sources, are enemies of the people who are part of those societies. This is true whether the society derives most of its power from heat, or whether it uses power from matter - antimatter reactors.

Recovering Waste Heat

One of the largest opportunities for improving energy efficiency is the recovery of waste heat for productive use and transduction to other useful forms of energy. The key is to match the recovery method with the application.

Key to making heat recuperation viable is understanding the nature of the energy involved. The temperature distribution of waste heat depends largely on the type of industry. For example, 95% of the waste heat in the electric power industry has a temperature below 150 Celsius...In contrast, 45% of the waste heat in the chemical industry can be up to 50 Celsius above this.

Plant operators usually look at thermal energy in terms of simple enthalpy - the heat content - and conclude that capturing heat of low temperature is not viable for powering other processes....Zhang and Akiyama, however, suggest that exergy - the ability of the waste heat to do useful work - should also be taken into consideration when planning an energy-saving strategy from the viewpoint of quality of energy.

They point out that high-temperature waste heat, with an adequately large exergy value exists in many manufacturing industries. For example, slag and exhaust gases from steelmaking reside at well over 1000 Celsius, representing a powerful energy source.

They explain that latent heat storage, chemical storage, and thermoelectric conversion could be used as effective ways of recovering waste heat, either individually or in combination. _energydaily

The ability to utilise marginal levels of heat -- whether industrial, solar, or geothermal -- will open up vast new worlds of energy generation. More clever transducers of heat to other forms of energy will multiply the available quantities of energy worldwide by a substantial factor.

Thermoelectrics Revolution

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Most of the energy from combustion processes such as an automobile's engine, is lost as heat. It seems a lot of waste to pump or dig fuels from the ground, only to lose most of the energy to the atmosphere as waste heat. Consequently, around the world engineers, scientists, and technologists are scrambling to find better ways to re-capture the huge mass of energy that is going missing every year.

Thermoelectrics is a growing and revolutionary method of redeeming waste heat to electricity -- analogous to photovoltaics except converting heat to electron flow rather than light. Brian Westenhaus brings us up to date on Nextreme Thermal, a company at the forefront of efficient thermoelectric conversion.

The thermoelectric field is gathering momentum and increasing efficiency. Many manufacturers are attending to this technology, as it requires no moving parts so the durability and miniaturization prospects look quite good.

For many heat producing power generation kits the excess heat is a nuisance, expensive to dispense with and money simply lost into things like rivers, the atmosphere and simply radiated away warming anything nearby which can be even more expense. From huge power installations generating electricity to automobiles thermoelectric on to microelectronics, thermoelectric conversion should find welcoming places. In the U.S. and Europe automakers from GM to BMW express enthusiasm for the technology to add to the electric output and reduce fuel requirements.

...The breakthrough product seems to be the Thermal Copper Pillar Bump (CPB) design that has applications in electronics where the technology can be used to cool and recover heat back into power. A highly desired goal is application in PC data centers where the operating costs for power to cool the electronics exceeds the power to process the data.

How good have they managed to get? A temperature difference of 60ºC has been achieved across the 60 µm (0.06 mm) high Nextreme CPB by running an electrical current through it. The Nextreme CPB demonstrated maximum power pumping capabilities exceeding 150 W/cm2. When subjected to heat the Nextreme CPB has demonstrated the capability to generate up to 10 mW of power per bump.

150 W/cm2 . . . That seems like a lot of power from a differential of 60ºC. Things are coming along faster than I had expected. _NewEnergyandFuel

Here is another look at the growing field of thermoelectrics, from Brian Wang.

More efficient retrieval and use of waste heat amounts to an energy revolution in its own right. Consider it but one more important piece in the puzzle problem to provide abundant energy to the growing needs of the future.

Cross posted at Al Fin

JTEC: Johnson Thermoelectric Energy Conversion

This heat engine, based on the "Ericsson cycle", has been discussed on multiple websites yesterday and today, including Brian Wang's.

It is based on the "Ericsson Cycle", and incorporates aspects of heat engines and fuel cells. It has no moving parts, it does not burn fuels or depend on chemical reactions (other than simple oxidation and reduction of H2 gas), and it is not at all obvious to me how it can be made to work efficiently. Anyway, here is the company's spiel:

The JTEC is an all solid-state engine that operates on the Ericsson cycle. Equivalent to Carnot, the Ericsson cycle offers the maximum theoretical efficiency available from an engine operating between two temperatures. The JTEC system utilizes the electro-chemical potential of hydrogen pressure applied across a proton conductive membrane (PCM). The membrane and a pair of electrodes form a Membrane Electrode Assembly (MEA) similar to those used in fuel cells. On the high-pressure side of the MEA, hydrogen gas is oxidized resulting in the creation of protons and electrons. The pressure differential forces protons through the membrane causing the electrodes to conduct electrons through an external load. On the low-pressure side, the protons are reduced with the electrons to reform hydrogen gas. This process can also operate in reverse. If current is passed through the MEA a low-pressure gas can be "pumped" to a higher pressure.

The JTEC uses two membrane electrode assembly (MEA) stacks. One stack is coupled to a high temperature heat source and the other to a low temperature heat sink. Hydrogen circulates within the engine between the two MEA stacks via a counter flow regenerative heat exchanger. The engine does not require oxygen or a continuous fuel supply, only heat. Like a gas turbine engine, the low temperature MEA stack is the compressor stage and the high temperature MEA is the power stage. The MEA stacks will be designed for sufficient heat transfer with the heat source and sink to allow near constant temperature expansion and compression processes. This feature coupled with the use of a regenerative counter flow heat exchanger will allow the engine to approximate the Ericsson cycle.

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You can find an animation of the device in action at the link above. It is a bit of a puzzler for me at this point.

Lonnie Johnson, the inventor, was formerly an engineer at NASA's JPL, before he made millions from inventing a glorified water gun. Some of his other inventions are quite intriguing, so check out his websites.

To be honest, I am more excited about the nano-antenna and the nano-spray silicon particle PV windows, than I am about the JTEC. But if the inventor gets a working prototype with better than 1 or 2 % efficiencies, I may start to perk up.

Heat conversion is one of the best ways to utilise solar energy, and it is the only way to utilise geothermal energy. Solar and geothermal are the two most abundant sources of energy on this planet, so we had best learn to use them every way we can.

Saving Billions of Dollars by Using Waste Heat

Thermoelectric generating devices are currently only about 8% efficient. But even at those low efficiencies, they might be able to save billions of dollars worth of fossil fuel a year in the US.

Tritt said more than 60 percent of the energy that goes into an automotive combustion cycle is lost, primarily to waste heat through the exhaust or radiator system.

“Even at the current efficiencies of thermoelectric devices, 7 to 8 percent, more than 1.5 billion gallons of diesel could be saved each year in the U.S. if thermoelectric generators were used on the exhaust of heavy trucks. That translates into billions of dollars saved,” Tritt said.

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Waste heat is a huge potential resource, ripe for the plucking. Using either heat engines or thermoelectric devices--specially customised for the purpose--many billions of dollars in energy costs could easily be saved. We should also expect that the best uses for waste heat have yet to be discovered.