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Electrical Power


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Electrical Power

In our every day lives we use electrical energy to do work for us. This electrical energy is provided either by our power company through the outlets in our wall, or we can buy stored electrical energy in the form of batteries. Different electrical appliances use electrical energy at different rates. As described in Sub-section 4.2, power is the rate at which work is done. The power rating of an appliance tells us the rate at which it uses electrical energy. For example, a 1500 watt hair dryer uses 1500 joules of electrical energy per second. The power companies charge us for the total amount of energy we use during a billing period. Most bills quote electrical energy consumption in kilowatt hours (kWh's). One kilowatt hour is defined as the amount of energy used by a one kilowatt appliance (i.e. one that uses 1000 joules per second) that is run for one hour. If you know the power rating of an appliance you can easily calculate how much it will cost you to run. For example, keeping a 60 watt light bulb on for a full day uses 60 watts x 24 hours = 1440 watt hours = 1.44 kilowatt hours of energy. At 9 cents per kilowatt hour this would cost just under 15 cents. Since kilowatt hour is a unit of energy, we can convert it to joules. We need to multiply the power by the time, so

\fbox{\parbox{4.5in}{\vspace*{7pt}1 kWh = 1000 joules/second $\times$\space 3600 seconds = 3,600,000 joules\vspace*{7pt}}}

Thus, if you pay approximately 9 cents for each kilowatt hour that you use, ten cents pays for almost four million joules of energy. If power companies quoted their rates in terms of joules, the costs would seem much more reasonable!

In any electrical appliance their is a simple relationship between the power output of a component, the potential difference across that component, and the current running through it. This is because charge times potential difference is energy, so (charge per unit time) times (potential difference) gives (energy per unit time). Thus, we have that:

\fbox{\parbox{4.5in}{\vspace*{7pt}power = (current)$\times$\space (voltage)\vspace*{7pt}}}

For example, in a nine volt battery, a current of 1 Ampère means that nine joules per second (i.e. 9 watts) of energy are being used. Conversely, if you are using a 60 watt light bulb plugged into a 110 volt wall socket, the current running through it is 60 watts/ 110 volts, or about half an Ampére. A 120 watt light bulb will run at twice that current.

Another Interesting Topic - Alternate Power - SOURCE

Make Your Own

Table of Contents:

Overview: On Making Your Own Electricity.

An overview of the efficiency of different methods of electrical energy generation and the key to comprehending just how much power you are making.


Bike: Pedal Power

DON'T plan to hook it up to a car generator. You just can't pedal fast enough. Here are several designs. We have built ten pedal power generators for use in the Ark Two shelter. You will see a picture of me actually pedaling one of them and lighting ten 12v florescent trouble lights. Nice trick. Good for exercise. But worse than the old galley ship oars for effort. And I don't know where you are going to get that many slaves. Still there are some applications for bike generators and key to their success are the low RPM generators that I discuss next.


Low RPM: How to make low RPM generators!

The difficulty with most generators is that you have to turn them too fast before they start generating power. These generators are neat because they put out power at low rpm and so will work with a bicycle, a low head water source, or lower wind power.


Lawnmower: Turn your lawnmower into a generator

Yep, turn your old gas lawnmower into a generator. This is also where you can use a car generator / alternator. Now if you can just find some gasoline to run the lawnmower.


Wind: If you have a good windy location.

We have built eight of these wind powered electrical generators. In fact at this writing we are still making the blades. Can't put them up, however, because the neighbors think the sound of the wind on the blades might be too noisy. Have gone to lots of other sites and looked at ones that others have built.


Waterpower: You should be so lucky

Same problem with waterpower today. We have designed systems for our two generation sites and would like to put them in the water - but the government won't let us. It is not just us - lots of people presently run into that problem, but anyway you can look at our system and we will discuss some aspects of water power. We are very fortunate to have two good water sources and although we can't use them today - things may be different when the time comes.


Motors: Running it backwards

Surprise! Surprise! Yep motors take electricity to run - BUT if you run them BACKWARDS, they put out electricity. The trick is to find something that will run them backwards. Wind or water can do it- for example.


Diesel: Lets not forget the big guys.

Probably the best we have got - if we can keep them running for parts and such - and can get or make fuel for them.


Batteries: Saving energy for future use.

Usually a key component with alternative energy systems is battery storage. Because the alternative energy systems often do not generate high volume it is usually essential to store energy generated during low usage periods for use during high usage periods.




Making Your Own Electricity
The Relative Efficiency
of Methods
What Watts?

One measure that you want to have clearly in your mind when you start considering electrical generating systems is that of watts. Just take a few minutes to this through if it is not something with which you are already familiar.

It is easiest to think in terms of light bulbs. A one hundred watt light bulb uses uses 100 watts of electricty per hour. A thousand watt generator would puts out a thousand watts in an hour and would therefore light 10 of these light bulbs. A four thousand (which is to say a 4K) generator would light 40 of them. Keep that in mind as you read through the following descriptions.

Alternative Sources of Electricity

There are numbers of ways of building your own electrical generators.

Let me explain briefly my concepts about power generation, in order of effiiciency.

a. The most efficient way to get electric power, is to buy it from the power company. Economies of scale make them by far the lowest cost source. The only reasons to have your own power generation are (1) you are too far from the grid (2) you need a back-up in case the grid is down (3) you are very dedicated to some other purpose such as survival, conservation, or innovation. These latter are definitely going to cost you money.

b. The second most efficient way to get electric power, for most people, will likely be to have a diesel or gasoline generator. A diesel combined with a battery storage unit can be relatively efficient in providing reliable power but it takes considerably more commitment than simply paying a bill to the electric company each month. The cost of putting in a substantial system for full off grid use will run between 20K and 40K. We have two diesel generators at the Ark. One is a 75KW and the other a 25KW. With the cost of diesel fuel and maintenace it costs about ten times as much to generate power with them as to buy it from the power company. Still they are main emergency mainstay. The 75KW will light about 750 (100 watt) light bulbs. Do the math. 75KW means 75,000 watts which divided by 100 watts per bulb gives us 750 bulbs which can be lit. In practice, we of course do lots of other things other than light bulbs. We run water and sewage pumps, big air fans, stoves and microwaves, and charge batteries, whenever we are running it.

c. The third most efficient way is with water power. In fact this might be the preferred way but most people will not have an adequate water source. The operative words are HEAD and FLOW. Head is the height that the water falls from and 100 feet is considered reasonable. The higher the better. Flow, the amount of water, is the other factor. Low head systems have been problematical but some people feel they have found a solution. I am no exception. I think the solution is low RPM (Revolutions Per Minute) generators with nozzles on the driving waterwheel to efficiently direct the water force. Unfortunately, the government won't let me try out my theory - but I have everything together ready to try when circumstances change. A useful system for complete household use is probably going to cost over 40K to install. A system on our big falls might produce 40KW and this would be 24 hours per day - without any additional cost of fuel. So yes, because we have such an excellent water source, it would pay for itself. However, when you add in the cost of trying to battle the government to put it in - then in becomes useless.

d. The fourth most efficient way to generate electricity is with wind. Wind is much less efficient than water because in most places it does not blow that constantly. Our little wind generators will produce about 400+ watts each (think in terms of four 100 watt bulbs) and since I am planning to put up 8 of them I will get in the neighborhood of what we would get from our one little 5KW gasoline generator. Most people would not have room for such a windmill farm such as we do, and fortuitously located on the highest hill around. Still the installation of the eight windmills will be around 15K to 20K. You can buy a good 5KW generator for one tenth the price - so you can see what I mean by putting this down as the fourth most (actually less) efficient way of generating electricity. But if the power company isn't working and you can't get gasoline then this may be the way to go.

e. The fifth most efficient way is with solar cells. This technology has come a long, long way in the last few years but still remains so inefficient that it would take over 100 years for a system to pay for itself, and in fact it undoubtedly never would if you included what the investment would earn elsewhere in interest and take into consideration that the system will physically depreciate before that length of time. One great draw back to solar cells is that the sun only shines half the day, and because of annual position of the earth and blockage by clouds, in many places your are lucky to get power 20% of the time. Unless you are out in space with sunlight 24/7 or have some very low power need at a remote location - forget it.

f. There are a great many other ways to generate electricity. Waves, thermal heat, animal power (the bicycles), chemical methods, nuclear, hydrogen generators, steam boilers, a great variety of fuels and so on and on. But none of these, and most of the above, are not practical for most individuals. Completely forget the many cons that are going around about getting free electricity from machines being suppressed by the oil companies, the government, and giant corporations. I have looked into these extensively for many years - and there is nothing to them as great as the stories sound. If there were a cheaper way to generate electricity the Japanese or the Russians or the Chinese would do it and no US companies would be able to stop them. Engineers in other countries are not dummies and would greatly love to have the electrical power in order to keep up with American productivity.



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