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Archive for the ‘Generating electricity’ Category
Monday, April 20th, 2009
I saw a catalog at NorthernTool.com, and there was a ad for a wind generator 120 volts , not DC and the ad stated “Run your meter backward”. The item number in this catalog is Model #44470. It states it also comes with an inverter built in.
Why would you need a inverter for 120 volts?
Second will this piece of equipment really work as it is in this ad?
If it does work as it is in the ad what if anything else will you need to set it up and does it come under the Federal law that the power company is required to let you use it in the system as long as they are advised of the equipment being on line?
I saw an ad for a car that can go 120 miles per hour, but that does not mean I can drive it down the Interstate at that speed if I buy it. In other words, the ad you reference may say you can turn your meter backwards, but you cannot do it legally unless you install all of the required safety dis-connects as required by your local utility, you complete their application form, and then they replace your existing electric meter with a model that records each in and out electric flow separately. Some states have other requirements like providing the utility with a copy of your homeowners liability insurance policy and having a lockable handle exterior disconnect switch for their use.
Although this company is known for their quality wind products, I don’t like having the inverter mounted 75 feet up a pole and subject to all the weather extremes. The inverter is the weak link in most of these systems and I want a system where this is at ground level and have as few electronic components as possible up on a tall tower and in the weather.
Most small wind systems generate DC power for battery charging. What they have done is mounted a DC to AC inverter inside the wind turbine to convert the DC electricity from the turbine into 120/240 VAC which can feed back into the utility grid. However, you cannot legally just plug this into the wall outlet and “turn your meter backwards”.
On another note, for those readers wanting to do something like this, please understand that the power output from any wind turbine is “wild”, in that it jumps constantly all over the place as the wind changes direction and flow rate. You cannot use a standard DC to AC inverter with a wind turbine since the voltage and current goes to such extremes every few seconds. Most inverter manufacturers make a “modified” version of their solar inverters to work with wind turbines, and most are designed for ground mounting in a protected area.
Also note that there are very few areas of the US with enough wind to make these worth the cost and the easiest way to tell is if there are already other wind turbines nearby. Those areas of the US with lots of wind year-round are usually already covered with wind turbines. Although you might be the first in your area, you may want to check a wind resource map for your state first before paying out $6000 plus.
Monday, March 23rd, 2009
Is there a UL product out there similar to a DC grid tie in inverter that would work for an AC generator?
I am aware of how the DC is converted with an inverter to AC and the phase angle is adjusted as well as the phase voltage to maintain proper alignment of electric main power. I have seen wind generators plugged directly into a breaker in the main panel as a grid tie in and initially was confused on how this was causing a dead short. However, I understand how it is possible now (there is an inverter in the wind generator head which adjusts Phase angle and Phase voltage to allow simultaneous feeding), but, haven’t been able to find anything for AC generators.
What I am looking for is something that will go between my AC generator and the main panel that will allow me to directly connect to the panel without a dead short, and allowing back feeding to the main line. Also an automatic shut off or transfer switch that would turn off the generator’s power supply from pumping electric back into the power grid when the main power goes out.
I am looking for an AC grid tie in device that will not cause a dead short.
Your thoughts would be appreciated,
I can’t imagine why anyone in the world would want to do what your are suggesting, although it is technically possible. Yes, there are special “in phase” monitors that will sync a generator with the grid, but this is only dome with very larger generators like you would find in hospitals or military bases. The main reason they do this is they are on a time of day rate and if they are approaching a peak demand period, by running their generators in sync with the grid they can save hundreds of thousands of dollars per year because these rates usually carry over the high penalty for the next 11 months. In addition, this switchgear to sync the generator with the grid costs more than your house and requires all kinds of coordination between the utility engineers and your installer. You will also be required to carry a huge liability insurance policy listing the utility as the insured in case something goes wrong and your power feeds back into a down line and kills a lineman.
Inverters for solar and wind systems have special circuits that make sure power is not fed back into the grid during a power outage, and the inverters must supply this power within a very narrow window of voltage and cycles. Most smaller generators are not that easy to maintain a constant output under varying loads.
Now that you know the legal issues involved with doing this, I will give you the simple reason why nobody in their right mind would ever do this:
If you count the cost of fuel, generator maintenance, repair parts, added oil changes, and annual service, you will be paid about 20% of what your actual costs will be, because you can never ever generate electricity cheaper than a utility. The only reason many of these solar and wind systems are doing this is either they are receiving some type of grant or tax credit, or they have been given a special feed-in tariff rate.
Many people still install solar systems as some systems also offer emergency backup, or at least do not need constant fueling or make noise like a generator. The national average cost today to generate electricity from a solar system is 35 cents/kWh. The national average for grid electricity is 9 cents per kWh. You figure it out.
Thanks for the insight and your knowledge on these subjects is amazing. Everyone at times has an idea and can’t figure out why the situation is the way it is; until they ask an experienced individual.
Thank you again. So if I wanted to have some sort of “economical” unit (and I use that term loosely), we would be best off using a UL device DC based unit (solar, wind, hydro) with an inverter monitoring the phase angle and voltage back to the main panel which would shut off when the main power goes out? If we wanted any sort of power when the main power goes out we would be using a battery system or a separate backup AC generator/transfer switch which would not back feed to the main power until main power comes back on. We would then turn off the generator and manually switch the transfer switch back to main power?
I guess I am in the same boat as most people trying to figure out what will work best for my individual circumstance. Oh, yeah I’m not a millionaire so the in phase monitoring for an AC generator would be out of the question.
I will probably be investing in a solar or wind powered DC unit with an inverter for my needs. Would you recommend any companies that you have had a positive experience working with for these devices. Probably, a 2KW-5KW max output would be what my financial situation will allow.
Jeff I can’t thank you enough,
Any inverter designed for grid tie in the US should have the automatic transfer function built in. If you select a battery based inverter, it will also include a built-in transfer switch to disconnect from the grid. Some battery based inverters include a “second” transfer switch to allow also connecting a generator and the grid, and will switch to the generator when the grid is down and the battery charge is low. If you select an inverter that does not have the second transfer switch, then you will need a generator that includes its own transfer switch panel.
Monday, February 2nd, 2009
I have unlimited, free natural gas from a gas well on my property. I would like to produce electricity for my own use from this gas. My electric bill is not that large since I have a gas furnace, gas water heater, gas clothes dryer, and gas range. How would you recommend I use the natural gas to produce electricity?
Thanks in advance .
Lucky you! Wish I had free gas after this winter. Although this may not be the most elegant solution, the easiest way is to buy a contractor- or better-quality gasoline engine generator in the 12 kW range. Almost any quality brand generator can be ordered with a propane/natural gas carburetor and gas control valve. These are easy to retrofit and just require replacing the existing carburetor with one modified to take a flex hose connection. The kits should also include a gas regulator and a gas solenoid valve wired to the run switch.
When the engine tries to start, the electric valve opens and makes gas available to the gas regulator. As long as the engine is “sucking” gas from this regulator, it will allow gas to flow. If the engine stalls or stops and the ignition is still holding the gas valve open, no gas will flow because the “sucking” has stopped so the gas regulator will not allow any gas to flow.
Of course this would require this generator to be running 24 hours per day if you wanted free electricity full time. This would quickly wear out this type of generator, so I would either shut it down at night, or combine it with an inverter and battery bank and let the generator only run 3 or 4 hours per day to re-charge the batteries, then shut down and run the electric loads off the inverter. It can all be set up to do this automatically, and we have had several articles on this type of system in past issues you can read online.
Friday, December 26th, 2008
I am interested in generating electricity by burning wood. I haven’t seen much about this subject on the website. Why would burning wood be a good choice or a bad choice for generating electricity?
Any information that you could pass along would be much appreciated.
The reason you have not much about this subject is it is not very practical today. This does not mean it does not work, but 99% of these systems require a wood-fired steam boiler which could explode if not designed and operated properly, it takes constant fire management to maintain proper steam pressure, it takes a good supply of water that is properly tested and treated to reduce chemical buildup inside water tubes, it takes a daily “blow-down” of the mud drum which will fill up with sediment, it takes daily removal of ash, and it takes regular lubrication and adjustment of all the moving parts.
If you check, you will find that almost all of this equipment is refurbished equipment somebody found or saved from the 1930′s and 40′s. Many states require any steam boiler, regardless of use, to be inspected every year by the states safety inspector, and many require that you maintain liability insurance for its use. Many states require steam boilers above a specific size to be operated by a full time boiler operator, and many states require this operator to be a licensed steam plant operator.
In other words, turning firewood into steam is not as simple as you think and is not very cost effective unless you already have the equipment and have lots of time to operate and maintain all the working parts. Most of these systems today are part of a steam show or other event. At one time I had a 20 kW steam driven generator that was new WW2 surplus and it was almost 10 feet tall and weighed 4 tons. It was too big, too heavy, and too much trouble to keep operational so I finally scrapped the whole thing.
Here is a test for you. Put a very large pan on your stove full of water right out of your tap. Now boil it until all of the water has been boiled off, then see how much scale and chemical deposits remain on the sides and bottom of your pan. Now do this 24 hours per day and how long do you think it will take to totally coat the pan with deposits you can’t remove and that reduce heating efficency. Now imagine this was boiler tubing inside a steam boiler to convert water to steam to drive a steam boiler.
Good Luck and be safe!
Sunday, November 23rd, 2008
I just purchased an old mill here in SC and along with it are 2 very large hydro power generators that have been stored for several years. One is a 1000 KW Westinghouse and the other is a 1200 KW General Electric.
I am trying to find a market to sell these to be used instead of just scrapping them
If you have any ideas please send me some contact info.
If I had just purchased an old mill with generators this large I would be looking into putting them back into service. With electric rates getting ready to climb through the roof in the next 2 years, these would provide all of your power needs plus selling lots of excess power back to the utilities. I would not scrap these as there are many old mills across the country that have been placed back in service by private owners and I am sure they are looking for replacement equipment and parts. As long as these have been protected from the weather they should be in good condition since they are just a rotating coil of wire.
Here is a friend of mine that is involved in this field who may be able to help you: Old Mill Power Company
Wednesday, November 19th, 2008
Can I hook up a engine driven generator to the grid in a net metering arrangement? Can I do this with an AC generator head? Can I do this with a DC generator head? How would I go about it and what equipment would I need?
If your state allows net metering then you can do this, but I do not know why you would want to. By every measurement I have seen, you cannot generate electricity with a generator cheaper than what you are paying the utility for power. The only way this might work out would be if the utility has very high rates and you ran the generator on waste methane gas from a large refuse pile or other source of free gas. Still, the wear and tear on the generator and replacement cost usually still makes this not a very good economic process.
If you do try this, most utilities will NOT under any circumstances allow a direct connect between your generator and the grid. You must separate with a power inverter that has been tested and approved for grid inter-connect. Without this separation the grid power will blow out your generators windings if the grid is energized, and if you did try this during a power outage, the 240 VAC backfeed from your generator will go through the utility line transformers “backwards” and be stepped up to thousands of volts that could kill a utility worker repairing the power lines down the street.
Thanks. I understand that much. I have already been in contact with the Utility Company and New Jersey DEP. I qualify for net metering. I also have a source of free or cheap fuel that I plan to burn, so that has been thought through. My question was about availability of equipment that would allow me to use an AC generator head to grid connect. Alternatively, if I use a DC generator head, can I simply hook it up to the inverter the way I would do for an array of solar panels? Thanks, and I appreciate your time. I had tried getting answers from the inverter-companies, but got no-where.
If you connect a fuel-driven generator to back-feed the utility grid, it is not only illegal, IT WILL BLOW UP YOUR GENERATOR!
One way you can make this work is by using an inverter certified for grid-tie application and designed to operate with a DC battery bank. The inverter serves as the “translator” between the DC battery bank and the utility grid to match the grid voltage, current, and 60 cycle wave form. The battery serves as a “buffer” . One manufacturer recently introduced a grid-tie inverter that can take the straight output from a DC wind turbine without using a battery bank, but you most likely would need to have a high voltage DC head on your generator to match the DC input required for this inverter.
In the battery-based system, the generator is separately connected through a battery charger to charge the battery bank which means you can use either a DC or AC generator depending on the battery charger. If this system will be under 8 kW, you might check into the several grid-tie inverters that are available that have connection for a generator input and include a battery charger. With the proper sizing of the generator, battery charger, and inverter, the batteries should never become discharged since you are supplying battery charging into the battery bank at the same rate the inverter is taking battery power out of the batteries at the other end.
Large utility size mega-watt co-generator plants and gas fired peaking plants do connect their generators directly into the the utility grid without first charging batteries, but they use custom designed power conditioning equipment and extensive safety equipment to prevent all of the many power and safety problems that can occur. I assume you do not have several million dollars for this equipment and do not want to spend another $100,000 for the utility permit and inspection process to allow direct inter-connection.
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