The Energy Converter in this project converts heat energy directly to chemical energy in a cell, the heat energy exploited in this project is basically the heat from surrounding medium, wasted heat from running machines, radiant heat from the sun, or heat from other sources. The Energy Converter in this project composed of an array of over 2000 cells thermally connected together. Each cell is capable of converting heat energy directly to chemical energy, that is to say each cell is electrically charged to its full capacity by absorbing heat. Thus it converts heat energy to chemical energy and stores it for later use in a similar way as batteries do. That is to say I use heat energy directly to charge each cell (it depends on the user whether to use the stored energy in each cell immediately or later). Thus this Energy Converter can do two functions at the same time or at separate times: 1- It converts heat energy to chemical energy 2- It converts the stored chemical energy into electrical energy. The size of each cell can be as small as 2.5mm diameter, 5mm high (cylinder) or less, however when the contents in the cell are well prepared the capacity of each cell can reach 0.8V, 1mA (for many days). I have a couple of cells from the Energy Converter which I can use for demonstration. During its operation, it absorbs heat from the surrounding medium or from direct heat source, but surprisingly it remains exceeding cool throughout (temperature inside stays less than that of the surrounding)! The Energy Converter in this project should not be confused with Photoelectrochemical cells or Photovoltaics, this device differs from those in many ways.
In thermodynamics, there is an entity called entropy. It's a measure of chaos, where chaos means a dispersion of matter over space and energy over space. Entropy predicts in which directions physical, chemical or thermodynamical processes will proceed, for entropy has always to increase. This law of increase of entropy is known as the second law of thermodynamics. This is for example why you don't have perpetuum mobile, for such devices wouldn't allow for the increase in chaos.
However, there is a nice little caveat: The law of incraese of entropy can locally be circumvented, through compensation with extra energy! That's why creating stuff is hard work, while destroying stuff is easy.
From among the various forms of energy, thermal energy probably has the highest level of entropy. It's therefore called degraded energy, and which renders it usually impossible to convert it to another form of energy, like chemical energy, without having to add energy to the system, in order to overcome the reduction in entropy , .
There is however, a class of processes that convert thermal energy to other forms of energy: endothermic processes and they invariantly need indeed an extra influx of energy, to overcome the entropy penalty .
Examples of energy conversions
- Thermoelectricity: Temperature difference → Electricity
- Steam engine
- Internal combustion engine
- Geothermal energy
- Fuell cells
- Photovoltaics: Photoelectric effect → Electricity
- Melting ice
- Evaporating liquid water
- Sublimation of carbon dioxide (dry ice)
- Cracking of alkanes
- Thermal decomposition reactions
- Electrolytic decomposition of sodium chloride into sodium hydroxide and hydrogen chloride
- Dissolving ammonium chloride in water
- Nucleosynthesis of elements heavier than nickel in stellar cores
- High-energy neutrons can produce tritium from lithium-7 in an endothermic reaction, consuming 2.466 MeV. This was discovered when the 1954 Castle Bravo nuclear test produced an unexpectedly high yield
- Nuclear fusion of elements heavier than iron in supernovae
Examples of endothermic reactions and energy penalty
As mentioned before, it's no rocket science to convert heath to another form of energy, but the trouble is, that it costs energy somewhere along the way. Often, this penalty is expressed in the efficieny of the conversion.
Let's look at some examples:
Internal combustion engine
Solar pannels are notoriously inefficient. Most of the energy is converted to heath, and only a fraction is converted to electricity.
A steam engine is an example of an internal combustion engine, but let's have a closer look at it, just to see how the entropy trouble/energy compensation rears its ugly head:
- Start with coal: Chemical energy is stored in coal. This is a highly concentrated form of matter and energy, representing low local entropy
- Burn the coal: Coal is being burned and turned into heath. Energy and matter is being disperses. Chaos increases immensely, and entropy increases as well. This is an exotherm reaction: Energy is being freed
- Boil the water: The thermal energy from burning the coal, is used to heath and subsequently boil the water. This is terribly inefficiënt, for heathing some 1,000 liter of water, all in one tank, represents quit some order. This goes against the law of increasing entropy and therefore, is not very efficient. Most of the energy of the coal just dissipates as heath to the environment
- Move the pistons: Water expands into steam (a conversion we actually skipped here. Something with enthalpy maybe). The steam subsequently moves the piston. That's imposing a lot of order on a system, and some major losses occur here. As an example: I've heard that in motorcycles, there is about 50% energy loss during conversion of a moving gearbox to a moving rear wheel
- Move the whole train: To make the drama complete: The moving piston subsequently has to move a whole steam engine or train or whatever. That's again a terrible local decrease in entropy and therefore, a heavy penalty in efficiency.
The trick with a thermoelectric device, is that it deploys a difference in temperature, rather than just thermal energy. Again, the local increase in entropy has to be compensated. In this case, this is done because the temperature difference between the two locations decreases. Hence, chaos is increased. More specificially, the decrease in temperature difference represents more energy than the electrical energy that is generated.
Maybe my favourite example:
- A fridge creates a cool space (e.g., 8 degrees centigrade) in an environment that is warmer (e.g., 21 degrees centigrade)
- Creating a cool space in a warm environment, goes against the law of increased entropy
- Therefore, you need to plug the frigde in the electricity outlet
- Now, there is a nett increase in entropy: The decrease in entropy through the cool space, is more than compensated by the dissipation of electricy (which eventually, is converted through warmth through the radiator at the back of the fridge, and again: heath is degraded energy.
The trouble with the Energy Converter
From the description of the Energy Converter, there seems to be two conversions at work:
- The device stays cool: Just like the fridge, this represents a local decrease in entropy
- Conversion of thermal energy to chemical energy: Whatever this is, it definately represents a local decrease in entropy.
Both these processes go against the law of increased entropy. This begs the question:
- Where does the additional energy comes from, to compensate for the local decrease in entropy?
- How does the overall entropy increases? From what source?