Intro and Info

[Gene Sp]

Hello

Name’s Gene. Live in NE Wyoming. Average wind speed here is 6.5 – 7 mph. As of today’s date, sunlight will be 15h 6min.
Currently between jobs and figured this would be a great time to research free electricity systems for my home. Have been to many sites, and now I have some basic knowledge of how build my own solar panels and wind generators. Problem is, now I have many questions.
Family will not listen to me about energy conservation and we use way too much electricity. About 55 KWH per day, and going up every month.

Questions:

1. Calculating production. What is the formula for determining the output of a device in KWH per day? If I build a 100w solar panel, would it take 10 hours at optimum output conditions to create 1 KWH of electricity? ie; 10h x 100w = 1000w = 1 KWH?

2. Most of the DIY projects I’ve seen use extension cords to “plug” your free electricity into a wall outlet.
a. Won’t this power only the circuit into which it is “plugged? What about the rest of the circuits in the house?
b. Will this method stop the flow of electricity back into the grid allowing for the safe working conditions of the workers repairing the problem during power outages?

3. Where might one find the schematic for building an automatic circuit cutout to insure the safety of the electrical workers when repairing a problem with the grid in times of power outages?
a. Could this be less expense than buying a ready to go unit off the shelf?

4. So far in my research I have not seen any mention of electricity loss. Solar panels and wind generators create DC power that must be converted to AC power via an inverter. How much, if any, electricity is lost between the generation source and the supply input to the house circuitry?

I’m sure, as my research progresses, I will come up with many more questions. Just thought I would get some of those questions out there while I was here typing my requested introduction of myself to the forum.

Thank you for your time and
Have a GREAT DAY!!!
Gene

[Rob Beckers]

Welcome to Green Power Talk Gene!

Hello

Name’s Gene. Live in NE Wyoming. Average wind speed here is 6.5 – 7 mph. As of today’s date, sunlight will be 15h 6min.
Currently between jobs and figured this would be a great time to research free electricity systems for my home. Have been to many sites, and now I have some basic knowledge of how build my own solar panels and wind generators. Problem is, now I have many questions.
Family will not listen to me about energy conservation and we use way too much electricity. About 55 KWH per day, and going up every month.

55kWh/day is quite a bit...
With that in mind, it is much cheaper to save a kWh than it is to produce one. Saving energy and improving energy efficiency are normally the first step, before looking at making your own renewable energy. I can see that can be difficult if the other household members are not interested. For many people that will be the case, until they get hit in the pocket book by increasing energy prices.


Questions:

1. Calculating production. What is the formula for determining the output of a device in KWH per day? If I build a 100w solar panel, would it take 10 hours at optimum output conditions to create 1 KWH of electricity? ie; 10h x 100w = 1000w = 1 KWH?

Solar panels are rated at sunshine coming in with an intensity of 1000 Watt per square meter. That is pretty close to "full" sun during the middle of day, but many times the sun will of course be more or less intense and PV output vary accordingly. To make it easier to calculate what the output will be from a PV module the 'insolation' value is used. It normalizes sunlight at 1000 W/m^2, and the number of hours a day that the sun would shine at that intensity. For your location the insolation is somewhere around 5 sun-hours a day, on average, for the whole year, for a PV panel with the tilt set at the lattitude of your location.

That means the output of a 100 Watt PV module would 5*100 = 500 Watt-hours per day on average, or 0.5 kWh per day. Of course, it'll be more in summer than in winter, this is average. Annually that makes 365*0.5 = 182 kWh/year.

Nothing in life and engineering is perfect, there are losses. Modules get dirty, when they are warm they are not as efficient, the inverter has losses etc. For a grid-tied PV setup a reasonable efficiency number is 0.7, or for that 100 Watt module it would make 182*0.7 = 127 kWh/year that can be fed back into the grid. For battery based PV setups the factor to use is more like 0.6 or 0.65.


2. Most of the DIY projects I’ve seen use extension cords to “plug” your free electricity into a wall outlet.
a. Won’t this power only the circuit into which it is “plugged? What about the rest of the circuits in the house?
b. Will this method stop the flow of electricity back into the grid allowing for the safe working conditions of the workers repairing the problem during power outages?

You hit the nail on the head, in that DIY backfeeding onto the grid with dubious equipment can be a danger to linemen. It is also illegal (at least in North America). The legal way is by using a UL1741 or CSA listed inverter, which is made in a way that it will stop backfeeding the grid when it senses the grid is no longer present. There are more requirements, depending on locale, such as an externally mounted disconnect for linemen to switch off the source and lock the switch.

Power fed back the to grid will indeed first go to power local loads. If there's anything left it can be fed back over the wires and transformer(s) to power other houses or the electrical grid at large.


3. Where might one find the schematic for building an automatic circuit cutout to insure the safety of the electrical workers when repairing a problem with the grid in times of power outages?
a. Could this be less expense than buying a ready to go unit off the shelf?

As mentioned above, it's illegal to use your own, unless you get it through UL1741 testing and listing. At that point you'll have spent many tens of thousands of dollars and buying a UL listed inverter would be much cheaper.

Inverters are not easy devices to build, they contain some pretty tricky power electronics. There probably are schematics floating around the Internet if you want to experiment, just don't hook the thing up to the grid.


4. So far in my research I have not seen any mention of electricity loss. Solar panels and wind generators create DC power that must be converted to AC power via an inverter. How much, if any, electricity is lost between the generation source and the supply input to the house circuitry?

For a good inverter and installation a factor of 0.7 is reasonable, as mentioned above.


I’m sure, as my research progresses, I will come up with many more questions. Just thought I would get some of those questions out there while I was here typing my requested introduction of myself to the forum.

Thank you for your time and
Have a GREAT DAY!!!
Gene

-RoB-

[Joe Blake]

G'day Gene, from "Down Under".

In Australia, we've finally got some action on home power generation, and the Federal Government (and State governments) are giving grants (up to $8000) for homeowners to fit PV panels and feed into the grid. The local power supplier is now installing "Two way" meters to read power going into and coming out of each house, and paying for the excess. As a requirement to get the payments the system must have an automatic shut-off so that when the main grid goes down for any reason, household generating their own power are isolated for safety.

I'm pretty amazed at your figure of 55 KWH/day. I'm only a single person but my consumption as at my last bill was 11 KWH/day. And that includes my business and at least part of my transport costs. The (Australian) national average is reckoned at about 15-16 units.

I agree entirely with Rob about saving energy as opposed to generating it. There are many avenues to explore in this field such as insulation of roof and walls, double glazing windows, fitting low energy light globes. Of course each region has its own problems and its own solutions.

Hope your visit to the forum is fruitful.

Joe

[Stewart Corman]

Gene,,
let me chime in here a bit as far as overall perspectives:

a great time to research free electricity systems for my homeno such thing as free ..the hardware costs a fortune!

About 55 KWH per day, and going up every monthget a Kill-a-watt meter for $20 and find out where your juice is going.
Your useage is 2x mine and I have a lot of toys.

Average wind speed here is 6.5 – 7 mphat ground level or 100ft up??? trees or open air?

stop right here ...I have 12mph avg (winter) wind speed and my application is submarginal ..with a 10ft/1.5KW turbine, I'd be lucky to heat domestic hot water to save about $15/mo in juice ...considering the tower can cost as much as the turbine, you can never get a viable ROI ...forget wind power at your location

So far in my research I have not seen any mention of electricity loss. Solar panels and wind generators create DC power that must be converted to AC power via an inverter. How much, if any, electricity is lost between the generation source and the supply input to the house circuitry?hmmm, losses are everywhere unless you do direct resistance heating ..then AC or DC doesn't matter ...the higher the voltage , the less line losses to get it to your house ...I will be running 400v/3phase AC 250 ft run at <1% loss. The people who use battery banks (because they are offgrid), automatically lose over 1/3 of the collected energy :

http://www.greenpowertalk.org/showpost.php?p=7482&postcount=12

if you want a technical paper just on battey banks:
http://photovoltaics.sandia.gov/docs/PDF/batpapsteve.pdf

note that charging is a loss and the batteries only function at 90% for a small % of the discharge range, whereby 50% is more typical. Also, batteries cost decent $ and have to be replaced after 8 years avg.

I have a buddy in Rochester,NY who installed a 3.4KW solar array with a grid tie inverter w/o battery bank ...that is most efficient setup, but expensive ...list price was $35K but with NY rebates his out of pocket was $15K ...that is what you need if you are serious ...note that his install has (2) inverters that cost $3500 each. He saves about $1K in electric bill/yr ie 15yr ROI. However, his logic is that the unit has a 50year rated life, so the value added to the house upon sale will be the $35K.
I think his math is a little fuzzy with net present value and new generation solar cells may cut the future install cost by 1/5x.


Where might one find the schematic for building an automatic circuit cutout to insure the safety of the electrical workers when repairing a problem with the grid in times of power outages?there are purists on this board who would really bash me for this, but here goes:
If you install a DPDT relay on a resistance heating device like a domestic hot water heater ..then either the grid is connected or the RE source is connected ...nothing ever feeds back into the grid ...it only trips on when the RE power is suffcient. Presume the full install of solar w/grid tie inverter is about 92% efficient. Oddly, in winter you get almost as much out of solar with the shorter days because the ambient temp adversely affects panel efficiency.

OT- you didn't mention it, but the least expensive, easiest to build DIY project is passive solar heating of domestic hot water.

Hope this helps,
Stew Corman from sunny Endicott