Various methods of storing energy are compared here. I have come to
realize that many people have no idea how much actual energy can be
stored in a battery, or in water raised up, or in a hot water tank,
or other methods of storing energy. So this presentation was composed!|
As an introductory comment, we will mention from the discussion below that a standard car battery can contain around 80 Ampere-hours of stored electricity, at around 12 volts, which totals around 1 kiloWatt-hour of electricity. It might seem like a lot, but you buy 1 kWh of electricity for around a dime! It actually costs you about 15 cents due to Delivery costs and assorted taxes, but the point here is that the spectacular claims of batteries and electric vehicles, are VERY exaggerated! We can show why gasoline is so popular by noting that a single gallon of gasoline contains about 40 kWh of chemical energy in it. So we might start by noting that a single gallon of gasoline might be compared to FORTY car batteries regarding gross chemical energy storage! Somewhat different than most people think!
For comparison purposes, we will consider an amount of energy equal to one million Btus or 300 kWh. This is about the amount of heat energy needed to heat a medium-sized home in a northern climate for one cold winter day, or for about ten days of electricity for a house (NOT heated with electricity!).
First, let's consider the "normal" ways of storing
energy (essentially all fossil-fuels):
The efficiency of converting chemical energy into heat are generally far higher than in converting it into mechanical energy. House furnaces were long considered to have around 80% efficiency if gas-fueled and 70% if oil-fueled. There are high-efficiency (condensing) furnaces which now have around 95% to 97% overall efficiencies.
Nearly half of the electricity cost is often delivery fees and taxes.
They also suffer from disadvantages in the inefficiencies of getting energy into and back out of the batteries. The process of charging batteries is not particularly efficient, the battery gradually loses charge over time, and then the process of discharge is not particularly efficient. This all results in only around half the electricity actually provided to a battery ever being available as useful output.
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The (alleged) Chevy Volt small vehicle has a battery pack which is supposed to have a maximum capacity rating of around 16 kWh. This is equal to around 50,000 Btus (not much when a single gallon of gasoline contains around 126,000 Btus of chemical energy in it!). It is also equal to about 16 standard lead-acid car batteries but without the thousand pounds of weight of them! GM seems to hope to get the cost of that battery-pack down to around $10,000 so they can sell the vehicle, but currently (2008) their batteries cost them much more than that! (In 2012, GM is selling Volts and they claim that a replacement battery-pack would be around $8,000, where GM will apparently be losing a lot of money on each of them! All electric vehicle manufacturers admit that batteries only can last a few years, and the battery-packs are worse about that, as individual batteries are not replacable in them. So when even one of the thousands of individual batteries within a battery-pack fails, the entire battery-pack must be replaced!)
Another highly publicized electric vehicle, the Tesla sports car uses around 2,300 small exotic batteries instead of the normal (heavy) lead-acid batteries. They admit that the batteries only last a few years and then the whole set has to be replaced, at an extreme cost. There is another experimental car that was shown to the Press where the battery-pack costs around $300,000!
Don't hold your breath regarding really high-capacity and high-efficiency battery-pack systems! Again, keep in mind that the FUTURE Chevy Volt only hopes to have a battery pack which contains around 50,000 Btus of chemical energy, where a single gallon of gasoline contains around 126,000 Btus in it. If really excellent battery-packs ever come to exist, they will certainly be immensely expensive and still need replacement every few years. But they are nice to dream about! The public also seems to totally ignore that batteries do NOT contain any of their own energy! They simply STORE (electrical) energy that was created somewhere else! And due to the inefficiencies of getting that electricity into and out of the batteries, as well as the inefficiencies of generating plants and the power-grid needed to get the electricity to a destination, there really are immense obstacles.
But for vehicles like golf carts and demo vehicles, where they only need to perform for a minimal distance at relatively low speeds, and for starting engines, batteries are great!
There is also the problem that all of the tanks generally only have around R-5 thermal insulation surrounding them, so they would each continuously be losing a lot of heat through their insulation because they were at such high temperature. Efficiency really drops if the energy needs to be stored for more than a few hours.
They have an additional problem in that initially heating up the water is often a very inefficient process. Whether using natural gas in a burner, or electricity, or even solar, there are always heat losses. But the thermal losses through surrounding insulation is really the most spectacular source of loss.
Pumping water up to a raised tank, to let it run down again to get power? It is a terrible idea, unless you have a rooftop swimming pool! A 500 gallon tank (4000 POUNDS) up one floor (8 feet) could represent 32,000 ft-lb of potential energy. 33,000 ft-lb/minute equals one horsepower. By the conversion factor just mentioned, this would be around 40 Btus of energy. You would need around 25,000 such tanks to store our million Btus! Using the conversion factor given above, we can see that this is also around 13 watt-hours or 0.013 kWh.
Therefore, if you had totally perfect equipment for conversion, that would be equal to ONE horsepower for ONE minute. Yes, it could probably light a single 60 watt light bulb for about 8 minutes or so, but that is not much considering all the trouble to reinforce the building!
The fact that some power companies (which happen to own mountains!) use this storage method is NOT due to it having very good storage capabilities or efficiency. They are simply faced with the fact that if they do NOT do such things, that nighttime-created electricity mostly disappears into heat and is totally wasted. So by using a system that has low efficiency is better than zero efficiency! There are so many sources and types of losses in this arrangement that it is really a terribly foolish idea, except for the fact that they cannot ever entirely stop making electricity, even when no one buys it! So this "pumped hydro storage" concept simply represents the least terrible of even worse alternatives!]
If any such 3000 PSI tank of hydrogen were in a vehicle, and that vehicle got into an accident, it would be VERY, VERY, VERY bad if the tank was damaged! There are thousands of industrial horror stories where a tank of 1500 PSI oxygen fell over and had its valve snap off and then the tank demonstrated Newton's action-reaction law in shooting off at aircraft velocities! Many have gone through concrete walls as though they were not even there, and some have been said to have flown nearly half a mile through the air. If the valve on an even higher pressure hydrogen tank were ever to snap off, a car accident could suddenly be far more dangerous.
IF you had the expensive equipment to Dissociate water into Hydrogen gas and then compress it to 3,000 PSI, the electricity just to Dissociate enough water for our 1 million Btus of Hydrogen would cost around $120 at current prices. More for the electricity to run the high-tech compressor, plus the cost of the tanks and high-pressure piping and a LOT of safety equipment! The current price of BUYING a tank of the lowest quality of industrial Hydrogen gas, one pound of it, is around $42. As we noted above, that tank contains around 60,000 Btus of energy, so our million Btus of BOUGHT Hydrogen would now be around (17 tanksful * $42/tank) $714. Not REMOTELY competitive with even the eight gallons of gasoline for around $25 now!
Such flywheels also have the effect of gyroscopic precession and the related effects. When a small aircraft makes a sudden lateral (side) turn, the gyroscopic effect of the spinning propeller often surprises a rookie pilot by forcing the nose of the aircraft upward or downward (depending on which way the propeller is spinning and which direction the turn was). The giant flywheel we are considering here is far more massive than an aircraft propeller and it would spin far faster, so those gyroscopic effects would be far more extreme. Depending on how the flywheel was oriented in a vehicle, a sudden left turn could cause the vehicle to instantly roll over on its roof! Not very practical!
A main distinction between wood and the fossil fuels is that wood contains the oxygen atoms of the original cellulose cells of the plants (called carbohydrates), while the coal, petroleum and natural gas had that oxygen slowly removed over millions of years to become nearly completely carbon and hydrogen (hydrocarbons) and they therefore contain a little higher energy content per pound.
Even better, wood is often available in many areas for free or nearly free!
There are variations on wood, which essentially have the same situation. It is possible to burn kernels of corn in a stove, or corn cobs, or even dried supplies of nearly any organic material. This Biomass is essentially also nearly all cellulose in composition, and therefore has roughly the same energy content as wood has.
You might note the links below where we have recently discovered that it is not actually necessary to "burn" organic materials to produce heat. An advanced version of the long-known composting process can allow bacteria to decompose those same materials, producing the same heat that burning/combustion does, and resulting in the very same water vapor and carbon dioxide as end products.
When the plants first grew, they absorbed a lot of solar energy in the photosynthesis process. There is Conservation of Energy, and that energy got converted into chemical energy of the molecules of the organic materials of the plant. When the plant eventually dies and decomposes, bacteria and other effects cause those complex carbohydrate molecules to break down, eventually into just water vapor and carbon dioxide, the same materials that the plant first used in photosynthesis. This decomposition completes what is called the Carbon Cycle. The point here being that very large amounts of heat is necessarily released during that decomposition. So when you cut your grass, and a few weeks later those cut grass clippings have disappeared, they have actually released very large amounts of heat in the process! It's just that no one has ever noticed that because the heat loss is spread out over the large area of your lawn and over the hundreds of hours of a few weeks! But when cut grass is bagged, those bags get HOT within a few hours! The same thing is true for autumn leaves and every other sort of organic material that NATURALLY decomposes.
Instead of letting that natural decomposition to occur spread out over a lawn, we Engineered a system that can capture the heat which is given off, which we call the HeatGreen 3a (or HG 3a). An acre of plant growth generally uses around 170 million Btus of solar energy per year. When those plants from that acre later decompose, they must necessarily RELEASE that same 170 million Btus, AS HEAT ENERGY! Since a medium-sized house in Chicago's climate generally requires only around 40 million Btus to heat for an entire winter, see the benefit? Just one acre of ANY sort of plant growth produces plenty of decaying material each year to be able to entirely heat most any house!
This approach essentially uses cut lawn grass and bags of leaves and bags of weeds and a wide variety of other organic materials as an Energy Storage system!
This method seems to have some advantages over combustion processes, such as extremely high efficiency, but still uses "fuel" source materials that have a good deal of chemical energy in compact space. In fact, even other organic materials, such as used motor oil and used automotive tires and food scraps work just as well as the source of energy. This is discussed below, near the end of this presentation.
Since these organic materials are going to naturally decompose anyway, this is an extremely GREEN approach to heating one's home, WITHOUT needing to burn any fossil-fuels at all!
First, yes, Ethanol actually has most of the benefits that are attributed to it. The most significant disadvantage regarding actual vehicles is that Ethanol has long been known to melt/destroy rubber seals like O-rings in automotive fuel systems. So nearly all older vehicles cannot use Ethanol or even the standard modern gasoline which contains maybe 10% Ethanol, without having damage.
But overall, this still sounds wonderful. In fact, if kept as a "hobby-level" fuel, it would be great. But that is not how it is promoted!
The primary reason why Ethanol has been promoted so heavily is because it is a product that is made from corn, and from the USA. Last year (2006), roughly 20% of all crops grown in the USA were grown as corn and then used up for producing Ethanol. Before Ethanol, that corn was used as food for people and for livestock, toward our National food supply. There are already great concerns that even that 20% reduction of available corn for food uses is endangering our food supply. As long as weather is good, we may be fine, but if there are any weather anomalies where crops are damaged or destroyed, there may be immediate food supply crises. With no obvious solution except to start importing food and corn!
That 20% of the entire National corn crop used to create Ethanol generates around 5 billion gallons of Ethanol (in a year). This might sound like a lot, but it is not when compared to our usage of gasoline. A simple way that we can see this is to note that there are presently 140 million drivers in the US, and the average driver drives 12,000 miles per year. For that mileage, the average driver buys a little over 600 gallons of gasoline per year (at an average of 20 miles per gallon of gasoline). So, between all those drivers, (multiplying) we see that about 84 billion gallons of gasoline are used up by private drivers each year. If we add in the many large trucks and the millions of smaller trucks, and railroads and airliners and taxis and all the rest, government figures show that roughly 200 billion gallons of gasoline or diesel are used each year in the USA.
The 5 billion gallons of Ethanol currently made from 1/5 of all the corn crop is therefore only about 1/40 of the actual consumption!
Could we rely on Ethanol much more than we already are? It is hard to see how! Unless we stop raising livestock (no steaks and no milk???) and eating corn products, we cannot give up many more percent of the corn crop to being used to make Ethanol. We are already about at the maximum that is possible.
But our government has already announced that around 33% of the entire grown crops on American land in 2007 will go toward creating Ethanol. The GOOD side of that coin is that the current 2.5% contribution toward our automotive consumption will likely rise to around 4%, still very little. The BAD side of that coin is that there will be even far less American crop that is actually for providing food! People in April 2007 are already noticing that food prices are already greatly increasing in the grocery stores, and they are already seeing that it is directly because of the strange compulsion our government currently has regarding making Ethanol no matter what the consequences!
(Update: The Bush government increased this usage of US corn to a mandatory 40% of every year's crop, further endangering the food supply if and when some drought or other problem occurs. In 2012, the severe drought reduced the corn crop, but Congress did not reduce the mandatory 40% of that reduced crop that must go toward producing Ethanol. Unbelievable!)
So when President Bush and NASCAR and politicians keep insisting that America can become "self-sufficient" by building and selling vehicles that can run on E-85 (85% Ethanol as compared to the common current 10%), they seem to be ignorant of where that Ethanol would come from! Sure, there is plenty of Ethanol for NASCAR races, but such things are actually misleading the American public into thinking that there is no problem, or that that technology has SOLVED the future energy supply problems! It is absolutely untrue, and what I would define as a lie, because the people promoting such statements KNOW that they are not true!
There is yet another tremendous disadvantage to using Ethanol! Virtually no one seems willing to admit that the PROCESSING of corn into Ethanol is VERY energy intensive! By any known method, it always takes MORE external fuel (which is invariably petroleum or natural gas based!) to make Ethanol than the end fuel contains! Making Ethanol is a losing proposition! (Have you ever heard anyone admit that fact?) So, the actual fact is that the production of Ethanol is not only using up 20% of the entire corn crop of all US farmers, but also requiring more additional imported oil and natural gas than it could ever replace!
Do such things ever make you wonder how competent our leaders are?
It also makes one wonder exactly when anyone is going to realize that this Ethanol adventure has been a really stupid idea! Our government has provided the (taxpayer) money to nearly entirely finance everything related to Ethanol, so businesses have had very little to lose. (Our politicians see that Brazil has accomplished getting most of their vehicles to run on Brazil-grown-sugar-cane Ethanol, but Brazil has far fewer vehicles than we do and they have very large croplands that are not needed for feeding cattle, so it works pretty well in that country. As to why politicians assume that it will work in the USA is pretty hard to fathom!)
This discussion has been meant to show that the several alternative ways of storing energy that companies seem to be aggressively promoting (like batteries) are fine if the needs are VERY small. As soon as you start considering significant amounts of energy, most get ridiculously expensive, and often impractical!
The point here is NOT that that particular idea has any useful merit in large scale energy storage, but just that MANY such concepts actually do exist, which someone should carefully examine. No one does, because they have always simply assumed that oil and gas and nuclear and coal would last forever!
Peak Power Rating vs. Average Power Rating|
You may drive a car which was advertised as having a 495 horsepower engine, and that may have even affected whether you bought that specific car. That engine rating can be called a PEAK POWER RATING, being the greatest amount of power that it is capable of producing. When creating that enormous amount of power, it is realistic to expect to get around one or two MPG gas mileage. But for AVERAGE driving on an Interstate Highway, your engine only produces around 40 horsepower, during which you may get 25 miles per gallon gas mileage. This AVERAGE situation is a far more accurate description of what YOU CAN ACTUALLY EXPECT, such as regarding gas mileage. Both situations are true, but they are extremely different. One is a situation which sounds very impressive, but which you will likely NEVER actually experience, except possibly rarely for a second or two at a stoplight! The other is a situation which you may experience every day of driving! IF you were only given ONE of the numbers, which would you consider more important to know?
Whenever electricity ratings are given for alternative energy devices, they seem to always be PEAK POWER RATINGS, meaning the greatest amount of electricity or power which can be created. That is entirely different than ratings for AVERAGE USAGE CONDITIONS, which would be realistic numbers of amounts of electricity or power which might NORMALLY be expected to be provided. The discussion and calculations included here will indicate that OFTEN the realistically expectable amounts of electricity or power is only around ONE-TENTH that of the PEAK POWER RATINGS. But no one bothers to mention this important fact! So advertising makes claims of spectacular performance numbers for photovoltaic solar-electric panels, and for solar roof panels, and for electric vehicles, and for Hybrid vehicles, and for windmill-electricity-generation, and even for FUTURE giant windmills and hydrogen as a fuel. They invariably state PEAK POWER RATINGS, like that 495 horsepower engine in the car, numbers that may be technically true but are extremely misleading.
(This 7% figure is for the most economical technology of solar cells, which is based on Cadmium Sulfide(CdS). There ARE higher efficient technologies which exist, such as those based on Gallium Arsinide(GaAs), but they are far more expensive and not within the price range of most people. There are even more expensive technologies that are based on silicon semiconductor technologies, which require a [metal] silicon ingot to be sliced so thin that sunlight can pass THROUGH it, which is extremely expensive to do! So higher efficiencies exist in solar cells, which are reported in media stories, but they are currently far too expensive for broad use. This all results in MOST commonly available solar cells being cadmium sulfide, and therefore around 7% efficient.)
So, if someone actually expected to get a usable 200 watts of electricity, they would certainly need at least 100 square feet of solar photovoltaic cells, which is a lot of money! And 200 watts for a few sunny hours is not very much electricity. No toasters or microwaves or televisions or computers! A few small lights and not much more.
The salespeople never present it this way! They say the 300 Btu/square foot/hour, sure, which they correctly say is around 100 watts of solar energy. They leave out those "details" which tend to ruin making a sale, and let the customer incorrectly believe that TWO square feet (duh, 2 * 100 = 200 watts, right?) is all they would need for the 200 watts of electricity. When the reality is around 100 square feet! How come it is not criminal to intentionally mislead customers so wildly?
It might be different if PV technology improved the current 7% conversion efficiency of solar to electricity. Or if such panels got a LOT less expensive and a lot more reliable and durable. But for a few hours of collecting 200 watts in any 24 hour day, it seems truly wasteful to invest thousands of dollars! Unless you simply want to be able to brag that you bought GREEN!
But the specific point of this Storage discussion is that the few hundred watt-hours of that PV electricity need to be stored for several hours until needed in the evening. Or worse, if the day is without any sun, maybe an entire day later. The electrical equipment and batteries usually sold cannot store enough energy to really use! Virtually all such people are faced with either conceding that they will NOT be able to be off-the-power-grid or they will have to go back (to the same dealer) to buy lots more expensive stuff!
YOU know lots of people who have mentioned wanting to go "off-the-grid", and they have been convinced by some PV salesperson or promotional literature that a few small solar panels is all they will need. No, it isn't, BY FAR!
Unless they install something like $100,000 of solar equipment, like that well-publicized house in the Northeast, where they actually often have enough electricity (but STILL have to sometimes buy conventional electricity), you are never going to hear such friends actually confirm that they accomplished that goal. Their lives may turn out to be more like Lincoln growing up in that log cabin with one wall missing, a very, very primitive existence!
We hate to see people get taken advantage of like that by salespeople, just because they do not understand subjects like those discussed here. We are providing this info so fewer people might get taken advantage of in a lop-sided conversation with such a salesperson. Unfortunately, that salesperson invariably gets a commission on whatever he/she sells, and so remarkably impressive claims are always made. And if a person only considered a noon situation on a perfectly sunny day and everything else was laboratory perfect, yes, such equipment CAN produce outputs that keep them from being sued! But not enough for "real life" situations where people actually NEED the electricity!
There are a few other methods of storing energy, such as phase-change salts and other exotic things, but they tend to be even worse than the ones described above, and also more expensive.
An entirely new concept has occurred to me in early 2007! This is a good one!
If you own a house in a temperate climate like Chicago, then you pay at least $1,500 every winter to heat it. Worse, you are spending that money to buy fossil-fuels, which are making the Global Warming problem worse. You buy around 80 million Btus worth of heat each winter.
In your good-sized yard, grass and weeds grow and trees have leaves, and you mow and rake and bag everything up to have it all taken away. Wherever that material goes, it will decompose, and in that process it will release heat energy. A LOT of heat energy! Farm studies have shown that each acre of land can produce around 95 to 125 pounds of organic matter (glucose) each summer day, and other studies have shown that an acre of grasslands and trees can produce around 17,000 pounds in an entire year. We know that each pound of [dry] organic matter contains and releases around 9,000 Btus of energy when it decomposes.
You can see that, if you leave that grass and those leaves on the one-acre yard, and they do not blow away, they necessarily give off more than 150 million Btus of heat energy during the months of decomposition. You have never noticed it because it is so slow and so spread out.
I have discovered a way to collect and use that heat to entirely heat your home. NO heating bills! NO fossil fuels used! Absolutely "carbon-neutral". It is a high-tech version of doing the Composting that farmers have done for centuries!
You can both contribute to saving the world and also save yourself a lot of money! You only need a few hundred dollars of common construction materials to build the things you need to accomplish this!
I have provided free complete directions on how you can make such systems. I actually have provided two different sets of instructions, one for a small version which is designed to eliminate the cost of heating domestic how water. Alternative GREEN Water Heater HeatGreen - A Simple and Non-Fossil-Fueled Water Heater, HG3a (biodecomposition) (March 2007).
The other is a larger version, which is designed to entirely heat your entire house, with NO cost for any bought fuel, no Global Warming consequences, and a new independence from utility companies! Alternative GREEN Furnace with no Fire HeatGreen - A Simple, Non-Fossil-Fueled Home Heating Furnace.
C Johnson, Theoretical Physicist, Physics Degree from Univ of Chicago