As a science teacher I can tell you that people find science scary. Perhaps you already knew that. They think it is something they “can’t do” or “don’t get.” They may say they do not have a scientific brain. I can also tell you that these are entirely untrue. Real world, personally accessible examples, instead of theoretical situations, help make the connection to the here and now. For instance, the title of this post “Inefficient Devices and the Laws of Thermodynamics” would probably be enough to scare off most readers. However, by thinking about your own home, this scientific concept comes to life.
In a recent post I alluded to the inefficiencies of converting electricity to heat when toasting bread. Both are types of energy (electrical and thermal). Since energy cannot be created or destroyed – the first law of thermodynamics, aka The Law of Conservation of Energy – you have to use some form of energy to generate heat for your toaster. Electricity is referred to as a secondary source of energy. It is not directly accessible in nature. In other words it has to be generated by another form of energy, say chemical energy in the form of coal. How does coal become electricity? One of the first posts from 2nd Green Revolution – Coal-Fired Electricity Generation – discussed many of the problems with using coal to generate electricity. Namely, only a third of the coal’s energy becomes electricity. The other two-thirds is lost as ambient heat. The process is the same for most electricity generation, except photovoltaic cells. As with nuclear power, natural gas, and oil-fired generators, thermal energy (heat) released from combustion, or nuclear reaction in the case of nuclear energy, boils water. The steam spins a turbine, which turns a generator. In turn, the generator spins magnets around a coil of metal, causing electrons to flow. Following the path, we see that chemical energy – natural gas, coal, or oil – transforms into thermal energy. From there the thermal energy is converted into mechanical energy – the movement of the turbine and generator, which causes the moving electrons to flow. Finally, the electricity – yet another type of energy – can be sent to homes so that it can be transformed into radiant or thermal energy. Here’s the problem . . . well, one of the problems. Every time there is a conversion or transformation of energy, there is a decrease in available energy – the 2nd Law of Thermodynamics. In other words, not all of the coal’s energy is converted into usable heat to toast your bread. In fact, a majority of it is unavailable. With each transformation, some of the coal’s original energy dissipates.
How many steps did the preceding scenario take? Is there a better way? One of the spectacular benefits of photovoltaic or wind power is that both reduce the numerous steps of energy conversion, thereby making more of the original energy available to the end-user. Using wind to spin the turbine directly cuts out the heated water and burning of nonrenewable resources. Furthermore, there is no byproduct or massive water requirement. Photovoltaic cells are similar in that they convert the sun’s radiant energy directly into electricity, without the need for turbines. Even better is solar thermal technology, which has been used for thousands of years. The heat from the sun’s rays can be transferred into water and used to heat one’s home, as water retains heat better than most any material. Consider a pot of water used to cook pasta. It stays warm for hours whereas the pot used to heat up sauce cools off quickly.
Keep an eye out for a follow up post on how these inefficiencies can impact your bottom line.
- Eric Wilson