Electrical Power
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
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:
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
Electricity
Make Your Own
Table of Contents:
An overview of the efficiency of different methods of
electrical energy generation and the key to comprehending just how much
power you are making.
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.
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.
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.
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.
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.
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.
Probably the best we have got - if we can keep them running
for parts and such - and can get or make fuel for them.
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.
Overview
Making Your Own Electricity
The Relative Efficiency
of MethodsWhat 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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