Watt? I don't know!

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I'm a brand-new "wannabe" and have started making plans. I've got the basic concepts down for water - how to get it, measure it and get rid of it. But I'm at sea when it comes to power. What's a watt? A volt? A BTU (I know - British Thermal Unit, which means it measures heat which is a form of energy . . ) But what does it mean? I certainly don't expect a course on the subject - but what would be a good starting reference for a total city-bred girl like me?

-- Deborah (ActuaryMom@hotmail.com), April 11, 2000

Answers

Deborah: I can help you with BTU. A btu is the amount of heat required to raise the temp of one pound of water, one degree farenheit.

A decent conversion chart will convert watts into btus, btus into watts etc helping you get a feel for energy equivalencies etc. www.homepower.com is the url for homepower magazine. They are entirely devoted to homesized renewable energy systems and can get as technical as you want to get. All of their back issues are on line, free, with a search engine to explore this area. Good luck and have fun.

I don't know where you're located, but you might want to check out one of the renewable energy fairs goin on all over the country this summer. They offer numerous workshops etc. They will also be listed in Homepower magazine.

-- john leake (natlivent@pcpros.net), April 11, 2000.


BTU - heat one pound of water one degree? What does that have to do with a burning a light bulb?

But seriously, thank you so much. I'm sure the website will help incredibly. I live in Chicago and know there's an alternative energy fair in Wisconsin in June - so I'll be there. I'm just hoping to know bit before I show up.

-- Deborah (ActuaryMom@hotmail.com), April 11, 2000.


You asked what a btu is. Thats what it is. To give you something else to think about, one kilowatt (1000watts) is equal to 3415 btu or 3.4 btus/watt.

Seriously though, strongly recommend homepower mag. I know they did a series of articles on basic electricity some time back as well as an article or more on ohms law, THE tool to help you get a handle on this stuff.

The energy fair you refer to is the MREA(midwest renewable energy association) reputed to be the best and largest fair of its kind in the world. Its a three day event and is normally held in Amherst WI during the weekend of the summer solstice but this year its being held in Madison to coincide with the annual convention of the international solar energy society. Zillions of workshops and very worthwhile. Iowa has one also thats quite good from what I hear. More info on each of these will be found on homepower.com and mrea has a website but I've never seen it.

-- john leake (natlivent@pcpros.net), April 11, 2000.


Are you looking to have alternative power or do you just want to be able to wire your new home (connected to the grid)? If you just want to learn how to do wiring you can do it with a basic book like "Step by Step Guide Book on Home Wiring". I've wired our whole new house with that book, a couple of others and the backup of a good electrician to ask questions of and to check on me. He hasn't checked and I haven't had to ask for a long time now. Either way you need to know how much load you are going to put on a circuit. It's not that complicated because every electrical appliance says how much power it needs/draws. Basically you just add the totals to make sure you won't be overloading the circuit. It's only slightly more complicated than that, easy really.

-- Peg (jnjohnsn@pressenter.com), April 11, 2000.

I'm definitely leaning more towards alternative power. Maybe even experiment with it here first. So I'm looking for the whole picture - how to make it, store it, measure it, use it. Most of the stuff I've looked at so far just started talking about watts and volts like you already know what they are. Is a 100 KW generator twice as good as a 50 KW? Is a 4A solar panel a lot, or a little?

-- Deborah (ActuaryMom@hotmail.com), April 11, 2000.


a watt is used to measure the amount of electrical energy you use the easiest way to to determine what size system you would is look at your current electric bill-not an absolute number but a good starting point.JAY

-- jay kessell (jay@townsqr.com), April 11, 2000.

The quick and dirty method of load determination is look at your electric bill. The amount of electricity used during the billing period will be listed in kilowatt hours---the total number of hours you used one kilowatt. Total your monthly kilowatt hours for a year or more and divide by the number of months you used in your sample. That will give you a rough average estimate of your monthly electrical demand. Divide that by 30 days to determine your daily demand and divide that by 24 for your hourly demand.

Since you mentioned a generator I'll use that as an example. Say your hourly demand is 5kw or 5kwh, same thing. Then you would need a minimum of a 5kw generator to meet your demand. The math is easy once you know what to do.

For what its worth, if you're thinking about an off-grid home all renewable energy pros will tell you its cheaper to save energy than to make it, so they are big advocates of conservation measures first. When the load has been reduced by conservation measures then size your system accordingly.

-- john leake (natlivent@pcpros.net), April 11, 2000.


Go to:

www.solarelectric.com

www.backwoodssolar.com

www.sunwize.com

Check out their bookstores. Write down the titles you would like to read and go the library. Read them first and decide which ones you want to buy. I highly recommend THE PASSIVE SOLAR HOUSE: USING SOLAR DESIGN TO HEAT AND COOL YOUR HOME, by James Kachadorian. There was another book but I can't remember the exact title. I think it was PEOPLE AND HOMES THAT USE SUN, WIND AND WATER. It is a new edition of an older book. Look through the above bookstores and maybe you can figure out which one it was. Good luck.

-- Vaughn (vdcjm5@juno.com), April 11, 2000.


This is so cool!

John - just to clarify - according to ComEd my average daily load is 18.7kWh which works out to be about 3/4 kWh per hour. So I'd only need a generator that puts out 3/4 kW? Or would it need to be big enough to take the max load - right now, that would be TV, computer, lights, VCR, stereo and microwave (hey, I just got started! Downsizing is first, I know).

-- Deborah (ActuaryMom@hotmail.com), April 12, 2000.


Deborah, you'd need enough of a generator to handle peak loads, but a generator is a very expensive way to run a household. If you DO use a generator, you'd most likely use it as a backup for some other source of power, such as solar (also quite expensive) or hydro (can be cheap, if you've got a decent amount of water and head, or fall) or wind (can be either very expensive or relatively cheap, depending on your wind situation).

With most of these alternatives, you will probably (unfortunately) need to have a battery bank to store energy when it is produced in order to use it when it is needed. There are exceptions to this, like if you have a very powerful source of water power year round. Also, you can power some types of equipment (such as fans and water pumps) directly, without batteries.

This is a very oversimplified explanation. There is no way to tell you all you need to know here. You'll have to start doing some research. I'd recommend searching the net, asking people who have personally used (and preferably designed) their own systems.

One thing I'd like to point out, and this is something a lot of people seem to have trouble with, even mrsolar.com, when last I checked his site. A watt is not the same as a watt hour, and they certainly cannot be used interchangeably.

John, my literature says that a kilowatt hour is equal to 3413 Btu's. I won't quibble about the difference between 3413 and 3415, as I don't know which is more accurate, nor do I care. But the important thing is it's kilowatt HOURS, not kilowatts.

This is an important thing to remember in order to compare relative costs, and relative values, of different energy systems. For instance, if you are trying to decide between an electric or a propane water heater, you could compare the costs per unit of power between these two power sources. A gallon propane contains 92,000 Btu's. Let's assume your propane costs are $1.00 per gallon (that's what I have to pay here in SW Oregon, should I decide to buy propane).

Now, 92,000 Btus divided by 3413 Btu's per kilowatt hour gives almost exactly 27 kilowatt hours. If your electricity costs $.055 per kilowatt hour, that means you'll be paying 27 kwh times $.055 per kwh, which equals $1.49 for the equivalent amount of power.

Then you have to figure out efficiency of the two water heaters. The electric one is simple: 100%, assuminmg you're not using a heat pump type water heater, which is going to be higher than 100%, believe it or not. The water heater will be less than 100% efficient. For the sake of argument, let's use 80% efficiency. The cost for the propane then becomes $1.00 divided by 80%, or $1.25, compared to the electric's cost of $1.27.

If your cost per gallon of propane is different than mine (and were I to buy "delivered":propane it would be significantly higher cost), or your cost per kilowatt is different than mine, you'll have to adjust the figures, but the idea is you can at least compare one fuel cost versus another. Once you learn how to do this, you'll find that lots of equipment dealers "fudge" the numbers to make their products sound better than they are in reality. For instance, I once saw a high efficiency oil heater claiming it could heat a peron's house for less than half as much money as an electric heater could do it. But they used very low cost per gallon of oil, and very high cost per kilowatt hour for this comparison.

If you're seriously considering alternative power, my favorite spot, so far, is a site run by Windy Dankoff. There's a lot of honest information to be gleaned at this site.The URL is http:// www.dankoffsolar.com/

Remember, learning about alternative energy can be half the fun!

-- jumpoff joe (jumpoff@echoweb.net), April 12, 2000.



Deborah, I grew up in an electronics family (dad was TV repairman), and in later years I owned and operated my own electronics/appliance service business for over 14 years. In all, almost 40 years of electrical/ electronics experience. Maybe I can help answer your questions. Voltage is electrical pressure, where amperage is quantity. A wide slow flowing river has high quantity (amperage), whereas a garden hose has high pressure (voltage). Electricity is little different. A watt is the quantity of 'power' used. To figure a watt, multiply amperage by voltage. 120 volts x 10 amps = 1200 watts. 240 volts times 10 amps equals 2400 watts. Remember the formula as "watts over E (voltage) times I (amperage)", or, "watts equals E times I". W=ExI

W ----- E x I

An appliance's rating tag will often state wattage and voltage but not amperage. Divide watts by volts to get amperage. 1200 watt heater divided by 120 volts equals 10 amps. 1200 watt heater divided by 240 volts equals 5 amps. You must have knowledge of the wattage formula above to figure other needs (such as using PV panels, wind generators, or such). By understanding the wattage formula above, along with the ohm's law formula (E=IxR), there isn't anything electrical you can't figure out or repair. If you have to figure useage for a specific need, email me and I can give you *almost* exact numbers. For PV panel output subtract 20% for efficiency loss, for wind power subtract up to 90% for efficiency loss. Hope this helps.

Larry

-- Larry Gowdy (sesquiq@mail.com), April 12, 2000.


Joe: You're right about the use of a generator as primary power. They're more suited as a backup. In your explanation of the propane numbers for a generator I think you forgot to factor in the efficiency losses for an IC engine. Do that and the costs just about triple, assuming 33% efficiency.

-- john leake (natlivent@pcpros.net), April 12, 2000.

You guys are so great!

No, I would never consider a generator as primary power source. I think we just ended up with that as an example. I'm using 300kWh a month now. I hope to cut that significantly. My current thought is to start with nothing and then build up as needed. But in estimating costs to build, I figure I'll price out something that could run my current (city) house, and something that could run half as much. I'm also thinking of adding a few solar panels to my (current) roof since I'm due to put on a new roof anyway.

-- Deborah (ActuaryMom@hotmail.com), April 13, 2000.


While all this seems simple it's not quite that basic.. During the times of peek activity in your home you must take the thid=s into consideration.. While you can limit electriial usage of items by putting them on timers so that they operate when not at peek family activity ie freezers, water htrs ect. addinga wood burning furnace to heat home and awater is a project that i am seriouly looking into as i have a lot of wood. Was even thinking of running cooling line sthru the pond to help with ac costs during the summer

-- Paul Reece (hd1@hotmail.com), April 16, 2000.

I just noticed that in my discussion of water heaters, I said, "The water heater will be less than 100% efficient." I left out the word "propane" I MEANT to say "The propane water heater will be less than 100% efficient". I hope this saves someone some confusion.

John, I'm glad you pointed that out about the efficiency of an internal combustion engine. I was comparing electric versus gas water heaters, space heaters, etc. I suppose the formulae would work for generators as well, though. But I don't like to even use the words "gas generator" and "efficiency" in the same sentence! Generators are noisy, smelly expensive, and inefficient, and I would never have one except for emergencies. I didn't even buy gas for mine for y2k, choosing other methods entirely.

Truth is, you don't HAVE to have electricity at all, although it certainly simplifies a lot of projects. I built my first house with all hand tools. (I had a particularly large right arm at the time :) I'd never do so again, but it can surely be done. I had a gas refrigerator, a propane and kerosene lights, wood heat, and a gas motor (shudder) on a pump jack to draw water out of my well. Without a decent source of electricity, you'll probably find , as I did, that a large part of your life is dedicated to doing things that most of us take for granted. Like turning on the tap and getting water. Like having hot water. Like having a light switch to turn on lights. You'll find out. It's not all bad, by any means, and is a great learning experience. But I'm glad I've got "grid" power now. (I still use lots of alternative power sources, tho--just not ALL alternative power sources)

Paul, you're moving in the right direction. Keep it up. I used to have a wood powered water heater, which also heated the home. It was a lot less efficient for space heating because of its water jacket though. If I were doing it again, I'd probably get one of the wood powered water heaters which does nothing else. They can be purchased at Real Goods, among other places. My cooling costs are mitgated by using a ground source heat pump. Awesome. But I hardly ever have to use it for cooling, because I can cool the house at night with a whole house fan, and it almost never gets too hot without aircon. Climate is important here; it gets very cool at night here in the summer (SW Oregon)

JOJ

-- jumpoff joe (jumpoff@echoweb.net), April 17, 2000.



Debora My wife and i use alt energy for all of our household needs when you decide to start to make any purchases we bought every thing from sunelco also get there product catologe it will explain alot of what you need to know just add . com for there web adress

-- bob vad (julvad@up.net), May 21, 2000.

I would recommend the following book:

Homemade Money; How to Save Energy and Dollars in Your Home by Richard Heede, Owen Bailey

The best place to start energy conservation is by conserving with what you've already got, IMHO. Start now, then compare month-to-month and see how you're improving. Once you get to the least-you-can-stand (or whatever point you decide), then look at the cost of alternative energy. HomePower magazine has a neat couple of articles over the past 2 years (I think) that describes taking your bedroom off the grid (or whatever room you want) as a starting point for alternative energy. This way you can get a hands-on and a good feel for the cost involved.

Best of Luck.

j

-- j (jw_hsv@yahoo.com), May 22, 2000.


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