I need an understanding for electrical consumption

[mkceak]

I am trying to get a conceptual or visual understanding of the amount of work/energy that we consume in electricity each month and when I look at the numbers, they don't seem real (of course it has been a long time since physics, so I could be way off).  

Given:Avg monthly US household consumption in KWH = 1,000 (less but close)

1watt-second = 1 joule

KW-second = 1,000 joules

1KWH = 1KW-s*3600sec/hour = 1,000j*3,600=3,600,000 joules

1ft-lb = 1.355joules

1,000 KWH/mo/us home * 3,600,000 joules/KWH = 3,600,000,000 Joules/mo/us home

divided by 1.355joules/ft-lb = 2,650,000,000 ft-lbs/mo/us home

Which means that it would take the same amount of work to move a 2,650,000 load a 1,000 feet as it does to provide electricity to a house each month.  This seems way too high. If this were true then it would make it almost impossible to find any mechanical means to generate enough electricity to run a house.

I would greatly appreciate anyone's help on this one.

[fcfcfc]

Hi: and I thought I was the only that could make something more complicated than it need be...

Look at your electric bill, total KWH each month. Decide how big a wind turbine (if wind is your choice) you want to invest in. Get a feel for the available wind in your area. Roughly figure your monthly contribution. .. and your done. With RE, unless you live in the desert (for solar) or at the top of a mountain (wind), you will most likely not get all the energy you are used to using if you have always been grid tied, so the dollars you have to invest will determine what you get. Then conserve to try and close the remaining gap... that simple...

[southpaw]

Your calculations are close enough to be correct. My power bill for the month of December was for 1300 kwh about 1/3 more but I live in northern Saskatchewan and use a 750 watt block heater in my vehicle for about 100 hours in December and have about 6 hours of daylight per day. On average 3 hrs of sunlight suitable for solar power.

14,444 watts of solar panels would keep me supplied in December or

If i had a 100% efficient generator it would require about 2 h.p. running 24/7.

What waste!

Southpaw

[Clifford]

You may be right.

I thought your estimate was a bit high for KWH.  But, I found some similar references:

8,900 KWH / year.

http://hypertextbook.com/facts/2003/BoiLu.shtml

I think I was using more on the order of 100 KW/month before my power was shut off.

This site has various conversion factors:

http://www.usefulinformation.eu/c_factor/energy.html

Including:

1 KWH = 2,655,000 Foot Pounds (which you calculated).

------------------------------------------------------

So:

1. cubic yard of water weighs:
   
8. lbs/gallon * 7.481 gallons/cubic foot * 27 cubic feet/cubic yard.  
   
   

thus 1616 lbs / cubic yard.

Drop that cubic yard of water over a 300 foot dam, and one gets:  

300*1616 = 484768.8 foot pounds / cubic yard going over the dam.

Thus...

(2,650,000,000 ft-lbs/mo/us home) / (484768.8 foot pounds / cubic yard going over the dam)

Or: 5467 cubic yards of water over the dam.

I'm showing that the Willamette River (a moderate sized river in Oregon) is running at 1,200 m3/sec  

So...  each house would be using about 5 seconds worth of water going over the dam / month (in an ideal world).

-------------------------------------------------------

Now, if you have a 100 foot hill behind your house.

And, an "ideal tram" coming back down (to carry the equivalent amount of weight up the hill).

A 200 lb person.  Carrying a 100 lb load up the hill (300 ft pounds of work)

So, on foot it would be:

2,650,000,000 / 300

That would only be:

8. ,833,333 trips / month up the hill.
   
94. ,444 trips / day up the hill
    
12. ,268 trips / hour up the hill
    
    

OR

204 trips up the hill a minute.

[cardamon]

That is interesting to see electrical inergy converted to those units.  I see no error with your calculation.  One way to grasp it may be to think of a hydro plant, and imagine how many pounds of water falls every second.  Then imagine that that is only one hydro plant and only  about 10 percent of electricy comes from hydro.  Another way to realized that this is reasonable is to note that 1000KWH per month is equal to a constant load of 1300 watts.  Now our 2650000000 ft-lbs per month is about 1000 ft-lbs per second.  I have a large right angle drill that draws about 1300 watts under load, and I bet wrapping a rope around the spindle it would move about 1000 pounds a foot every second with the correct gearing - maybe not quite but there is some power loss, etc.

[richhagen]

You should look at your electric bill, or read your electric meter, to see what your actual usage is.  There is quite a bit of variance between the amount of usage in different homes.  

Electricity and other sources of energy we use seem artificially cheap when one considers the amount of effort involved in replacing it.  We are currently burning off stored energy in the form of coal and oil that built up over many millions of years, or nuclear energy that was built up in the stars before the earth was even a planet.  

When you consider the size of wind turbine, or solar panel array required to replace your current consumption, you may be surprised at the results and costs.  Still it is an addicting hobby to generate as much of it as you can, and in remote locations, a useful and practical skill to have as well.  

In my case, I used 38 mega joules per day in electricity and 460 mega joules per day in natural gas consumption for heating and hot water on average for a year (2004) from my utility billing statements.  My natural gas cost only 23.4% as much per additional joule used however for the one year period which was analyzed.

When starting, one can usually conserve more total energy than can be easily generated.  About 75% of a typical homes total energy consumption is used for heating and cooling, so unless you have a practical renewable heat source such as wood, and don't bother with air conditioning, most people can conserve more energy by adding insulation, thermal windows, and storm doors than they can generate by building even a modest sized turbine.  

I can't build a large wind turbine where I live, but I likely use enough less energy now than I could generate with a 10 foot diameter turbine since I have been trying to conserve.  I still have a lot of things I can do to reduce my consumption further.  Your objectives may differ, but my personal goal is not to do without, or live an austere life style, but just to conserve what I can by eliminating waste.  

You are on the right track to try to measure your usage.  Many people start trying to replace or duplicate grid power, and don't have a realistic idea of the task that they have undertaken.  There are many examples of people who post here who live good quality of lives with no grid connection at all, generating all or most of the power that they use, yet enjoying most modern conveniences because they make practical decisions about what to power and what to replace or do without.  

Have fun, Rich Hagen

[stop4stuff]

yep mkceak, seems daunting doesn't it?

here's something to consider...

1hp = 746W = work (energy) needed to lift 33,000 lbs 1 foot in 1 minute

a 100hp car engine is a 74.6kW engine

that 100hp engine (at max power) would put out as much power in 13.4 hours as the average US household uses in 1 month...

that 100hp car engine is about 33% (or less) efficient... the other 66% (149.2kW) of energy is lost as heat!!!

a 100hp engine is 'small' these days...

the Bugatti Veyron at max warp outputs the same US monthly average power in about 1 hour 20 mins

the CAT-LINK V (Awarded the Blue Riband  - US to UK, 1998) passenger & car ferry at max warp outputs the same US monthly average power in about 141 seconds

a 747 at max warp outputs the same US monthly average power in about 75 seconds

the space shuttle lauch rockets (first 2 minute burn) outputs the same US monthly average power in about 0.4 seconds

it would take 7 Tour de France cyclists (~200Wh each) peddaling for all they're worth (24/7/365) to match the average consumption!!!

[mkceak]

I appreciate the help, but this is depressing.  I don't have the ability to put up a wind turbine and in South Florida, I can do without heat but must have a/c.  I could probably reduce my consumption to 600KWH/month (still have to run the pool pump) and I am not going without washer/dryer and dishwasher (too many kids).

I am amazed at the amount of energy needed per house (from a visual perspective).  It seemed (incorrectly) that if you had a family of four, that there should be some way to combine 30 minutes of cardio per person and 30 minutes of weight training per person, then combine it with other forms of mechanical energy (such as using the water pressure, maybe a small wind turbine, possibly some solar panels (although I am not a fan of solar) and take care of a good chunk, if not all of the electrical consumption.

BUT...........

If everyone does 10 different weight stations and does 10 reps of 100#'s and they did the 100#'s up and down and the rage of motion was 2' then we would still only be looking at

4people*(10stations)*(10reps)*(100#'s)*4ft(up & down) = 160,000 ft-lbs.  THIS IS NOTHING.

What got me a little interested was the magnetic bearing, vacuum sealed flywheels but you still need some mechanical energy to get them and keep them moving AND this isn't going to work.

[fcfcfc]

Why are you not a fan of solar, especially in FL..??.. Is it the economics of PV or something else..??.. Do you at least have solar thermal DHW..??.. DHW is the second largest energy gulper in the normal res and for you with a lot of kids, its probably pretty big....

[elvin1949]

mkceak

 To many kid's to do away with the dishwasher.

My Momma said she had 7 dishwasher's,why go buy another one.[7 kid's] A/C is not a necessity there.

My sister live's in St Augustine she don't use her's over 5 or 6 day's a year.Fan's the rest of the time.

 I could go on for a while but i ain't.PLEASE quit

wasting power,it will save some for your KID'S.

later

Elvin    

[byndhlpng]

 OK:   My electric bill said I consumed 4700 kwh for the billing period (month).  What size system and blade size could I use to offset the most of those kwh as possible?  I live in central Indiana and I will put daily wind speeds at 7 or 8 mph on the average, ith a range teween 10 to 14 being common.  For the sake of this question and possible solutions please use 8 mph as a daily WS.  I dont expect to offset the whole 4700 kwh.  Then give me a ballpark figure as far as cost.  I would consider either wind or solar or even a hybrid system.  One more piece of information that might effect the outcome.  I believe I would need a tower at least 60 ft tall on my property to get above the trees.  Other than trees, when above 60 ft there aint squat for miles and miles.

Byndhlpng

[DamonHD]

Goodness!  My whole house and family is only using just over 200kWh/month of electricity!

Knocking ~25% off that with solar PV is costing me of the order of US$15,000.

Wind is just not viable for more than a secondary trickle-charge source for many urban situations, including mine, for all sorts of reasons including wind speed and zoning/planing and safety restrictions.

Rgds

Damon

[TomW]

Thread hijacking at its finest..

[byndhlpng]

Tomw,

Would you suggest I start another posting?  Then they can rip me up for asking a  newbiequestion thats already been discussed two years ago?  The people here seemed likely to give me a more accurate answer. (judging by their responses to the topic at hand) Sorry if I horned in.............

Do you have a positive reaction?

Im leaving now to go scope out further innocent victims lol

Byndhlpng

[mungewell]

I appreciate the help, but this is depressing.  I don't have the ability to put up a wind turbine and in South Florida, I can do without heat but must have a/c.  I could probably reduce my consumption to 600KWH/month (still have to run the pool pump) and I am not going without washer/dryer and dishwasher (too many kids).

In addition to reducing your electrical consumption you should spend some time looking how you can adapt the physically aspect of the house to cope better with your climate.

For example: Maybe an attic fan would make a huge difference to heat build up during the day.

20KW.Hr production a day is do-able, it's just a large investment.

Anyway good luck,

Mungewell.