Energy is all around us, in every aspect of our daily lives, affecting much if not all of our expenditures. Yet, sadly, most Americans have a very poor understanding of how energy is intertwined in our lives, and therefore how it can be saved, or recaptured when lost. A better understanding of how energy is transformed would help most of us to save or recapture it, instead of loosing it.
To help understand the ins and outs of energy, let's study a concept used in elementary school called Energy Chains. Perhaps you have heard of the Food Chain. It is a small part of total Energy Chains. To understand energy chains, we must first understand that the same energy can change forms, like from sunlight, to corn, to ethanol, to powering your engine, and finally to heat. However, energy can never be created or destroyed. In 1638, Galileo publish the law of consrevation of energy, stating that the total amount of energy in any isolated system always remains constant, it can change forms but never be created nor distroyed. Actually we have now discovered that matter can be changed into energy in what we call Atonic Energy. That is the source of the suns energy. But for our study of energy, we will say that Sunlight is the only real source of energy to the earth, is at the top of the energy chain, and heat, at low temperature is at the bottom. Almost all energy ends up as lost heat.
Heat at Different Temperatures
So you say, what do you mean by low temperature heat; that sounds like a misnomer. As an example, let's look at the energy lost from your car's engine. Unfortunately, most (about two thirds) of the energy from that expensive gasoline is not used to move your car. After the engine extracts what power it can for turning the wheels, the rest of the energy is lost as heat. That heat is carried away by the engine coolant at 190 degrees. That is pretty useful heat. That lost heat could be, as a matter of fact usually is, used in your heater to heat the inside of your car. If not used there, the heat is transferred to the air passing through the radiator coming out at perhaps 150 degrees. That is still pretty useful energy to heat something like your home, if there were something to be heated. But soon it mixes with the rest of the air in the countryside raising the temperature by say 1/10 of a degree. At that point it is effectively lost. It will probably be lost to outer space in the next clear night (If we don't have too many greenhouse gasses in the air).
Let's get back to the Energy Chain. That sunlight, why is it so useful? This multifaceted, radiant, form of energy is used by chlorophyll to produce energy in wood, and of course the energy in all the food we eat. Energy from the sun thousands of years ago, stored in wood and vegetation and buried in the ground, are today's fossil fuels. Energy from our crops is used to fuel us, to make Ethanol, and many other uses. Sunlight is also be used to evaporate water from our oceans and lakes. This evaporation, like boiling, absorbs huge amounts of energy. This energy, stored in the clouds, can produce thunderstorms, tornados and hurricanes. But a very valuable outcome of that energy is that much water is lifted high up in the mountains, giving it the potential (Potential Energy) to drive electric generating turbines in hydroelectric dams as it comes down (the Water Cycle). So what are today's practical, usable sources of energy?
Use of Fossil fuels
Fossil fuels including, crude oil, natural gas (including propane), and coal are our major source of energy today, though that will probably have to change soon. These fuels of oil can be burned directly in the engines of our cars, trains, or airplanes. Unfortunately, these engines typically lose two-thirds of their original energy as heat and chemical gases. We can also burn all three of these fuels in our thermoelectric power plants to produce electricity. These plants make somewhat better use the energy by returning as much as half the energy as electric power. Also, because these plants are firmly located in one location, previsions can occasionally be made to reuse some of the waste heat to, for instance, to heat homes in a nearby city, or produce ethanol. These plants often burn natural gas because it is so clean. This practice uses vast amounts of this vital resource to save industry a few bucks on air cleaners. It should be saved for use in home heating systems, which are so small that it would be impractical to clean the stack gases all of them. Also, crude oil and natural gas, considering the exponential growth in demand, will probably become very expensive in the near future. Finally these fuels and coal produce green house gases. Therefore fossil fuels, as convenient and inexpensive as they are now, do not fit very well into long range planning. It would probably be much wiser to be saving oil and even natural gas to be used only in air travel, since aircraft will probably never successfully use batteries or wires to fly electrically.
We have seen that energy cannot be created nor destroyed; but it can change form. Almost inevitably it ends up as low temperature heat. There is a device that could salvage some of the heat by bringing its temperature back up again. It is called a heat pump. It extracts heat from a large supply of air or water by lowering the temperature of the air or water a bit and substantially raising the temperature of the air on the output side of the pump. These devices require energy to operate, but you get more heat energy out than you take in, because of the energy they are extracting on the input side. These are great to heat your home or other buildings. The same device is used to cool you home in the summer (Air Conditioning). You just reverse it. There is no other way to make an area cooler except to pump the heat out. You cannot destroy energy, only pump it away. So the only way to make your refrigerator cool, or air conditioner work is to use a heat pump to extract the heat from inside and dump that heat somewhere. That is why a room air conditioner must sit in a window, so it can dump the heat outside. Central air conditioners always have a unit outside. Your refrigerator dumps the heat out the back. No you cannot cool you house by opening the frig door, because more heat is pumped out the back of the frig.
I have not yet discussed electricity since it really is not a source of energy, but a means of transferring energy. It does not occur in nature as a usable source, and there is really no way to store large amounts of it effectively. It is also rather hard to transport between continents. On the other hand, electricity is definitely the most versatile form from which to receive energy. It can be used to produce heat, light and mechanical energy, all at very highly efficient conversion rates. Electric motors are usually well over 90 % efficient. Electrical heaters are usually at 100 %. Farther, the waste energy from electrical operations is almost always heat, helping to heat the home if that is needed. So, electrical energy is truly an incredible way to receive energy.
So our problem is now one of upgrading our methods of converting the known usable sources of energy into electricity more efficiently. At the same time, we must be conserving special sources such as oil for applications that may never be able to use electricity such as aircraft. At the same time, we ought not to be producing green house gases. That is a very tall order.
Why are hybrid cars so much more efficient? There exists a common misconception that engines run most efficiently at the middle of their power range--not so. Most engines reach peak thermal efficiency near full power. Thus a 4 cylinder engine gets better mileage in a given car than a 6 or 8 cylinder, since it is being operated close its peak power. However, no one wants to drive a car that, at 60 mph, won't accelerate, or pull a hill, or buck a headwind, so we put in larger engines. With the hybrid, we put in a small engine coupled to a generator. The engine only runs at near full power, its most efficient range. The electric power from the generator drives the wheels and keeps a large battery charged. When the battery is charged, the engine shuts down. When you are driving fast against a wind, the small engine is running most of the time. When you drive in the city, the engine doesn't have to run often, or maybe on short runs not at all, saving the expense of warming up the engine. Now that electricity has become less expensive than gasoline, we should be plugging these hybrids in at night. But there is another aspect of hybrids that is the topping on the cake. Standard cars use a lot of energy speeding up just to have the light turn red and lose all that energy as heat in their brakes. Now the electric motors that drive the wheels in a hybrid can also be generators. So when the hybrid driver applies his brakes to slow down for a light, he actually gets a charge for his battery. When the brake is depressed, a controller changes the motor to a generator thus dragging the car speed down. The normal brakes are still there. So the energy recaptured during braking can be used to speed him up again. The same applies when driving up and down steep hills.
Managing Energy Losses
Here are some ideas that will help you make better decisions when considering how to save energy in you home. If you are heating, you want all the energy in the house to stay there. The energy from all the electric power used in your house ends up in your house, as heat. In light bulbs 90% of the energy go out as heat immediately and the other 10% becomes heat when it hits the walls. All energy going into electronic devices comes out as heat. Water heaters, stoves, driers all produce heat directly.
The problem then is to keep it there. Consider you home as a container trying to hold the heat in your insulated walls. Now, what I am about to say, only holds if you are heating your home. If you are cooling, a whole different set of rules apply. First of all, no amount of turning off lights or other appliances will help at all. All the power that goes in ends up as heat anyway, and turning of lights only means the heater will run more. So in areas of the country where they are heating, changing the date of daylight saving time probably made no difference at all. So where can you save? Good insulation in you walls (we all know that). So, where else can heat escape? Most hot water leaves you home still heated, so cutting down on use of hot water could save energy. If you have a heat pump, waste water would be a great source of warmer water. That would make a very efficient heat pump. Your clothes dryer uses huge amounts of energy and we usually vent it outside. A simple heat exchanger could salvage much of that heat. By the way, if you are wondering, the energy in the light and sound that leaves your home through windows, etc, is virtually negligible. Again all this only hold true if you are heating.
What about when you are air conditioning? The whole story changes; now you don't want that heat. Though it doesn't cost as much to pump it out as it did to put it there, there are still costs. So now turning off lights and appliances really helps. It costs to get it in and it costs to get it out. People put out heat too. After all, if we eat 2500 calories a day most of that turns into heat (I have heard, 1- 300 watts while we are at rest).
Have you ever noticed that sometimes you must turn on the AC in your car or home when it is still quite pleasant outside. That is because of all the waste heat in the house. So, since the air outside is cooler than inside, much cooling could be accomplished by better ventilation. Problem is, since you will need just as big an air conditioner when it get really hot, the extra expense of bigger ductwork and air cleaning equipment is added initial cost. We must start considering long term saving brought about by a bit higher initial cost, not to mention overall energy savings. As energy costs skyrocket, these will become a better long-term options.
So what sources do fit into our future plans? Converting sun energy directly into electricity is a super great idea, except that the only known methods are not very efficient, only a small percent of the sunlight is converted to electricity. So, development of better methods to convert sunlight into electricity should be a major assignment. For heating your home, passive solar heat (Windows) lets most of the suns energy in as heat, providing a great home heating source. Wind generators are fairly efficient now, but still it require huge fields of them to produce only small amounts of energy, so they probability will never be the answer.
Arguably the most promising technology available today is nuclear power. Through a severe misunderstanding of the technology, and an unfortunate accident, public sentiment has gone away from this important source of power. This, the only real non-solar power, has the best supply of fuel for future use of all major sources. With well-regulated design and operation, this source could safely power the world for years to come. Also, with wider use of present day nuclear power technology (the fission reactor), hopefully the public would regain confidence in nuclear power. Then, perhaps we would also make better progress towards controlling the other form of nuclear power, fusion; the source of the suns power. This completely clean nuclear process uses hydrogen from water to produce gigantic amounts of energy from a few drops of water. The problem is, the only known way to start the process is a dirty nuclear explosion. Then after that, there is no know way to contain the huge energy release. Still, most scientists feel that this will be our major, if not only, source of energy with in 100 to 150 years. We should be working on it now.
Future electrical power plants must be state of the art nuclear and coal fired plants.
Natural gas should be saved for home heating. Ground transportation should look toward electricity, or more efficient power plants such as the hybrid. We should be saving oil for use in Air travel of the future.