electric generation

[screenzzzz]

Now, I maybe on the wrong site for this and then again I might not! so I figured I'd ask anyway.
I am looking to build my own standby electric generation system and would appreciate opinions on the best type of generating motors. I am looking at 12kw and 24kw and something that can run 7/24 for long periods if necessary.

Thanks Gary



Be courageous. I have seen many depressions in business. Always America has emerged from these stronger and more prosperous. Be brave as your fathers before you. Have faith! Go forward!” Edison

[Geof]

Diesel is probably the most reliable but in some locations with natural gas this is used to power stand by systems.

Are you planning on hard wiring it with with contactors so that you isolate your system from the grid and then turn on the standby generator? This needs proper design and engineering and probably installation by a licensed electrician and approval from your power company.

You also have to consider routine maintenance and testing unless your power goes out frequently so your system operates regularly. With diesel you have to worry about the fuel going off so if you are not consuming it you need to either replace it or get it treated. You also have to worry about condensation in the fuwel tank and water build up. You have to periodically run the motor to splash oil around and stop things gumming up. The battery needs to be on a trickle charger if the system is going to sit for months without being run.

Or you can push your luck like people do and hope that it will fire up every once in a blue moon when it is needed even if you totally ignore it for the rest of the time.

[screenzzzz]

Thanks for the response Geof.

Actually I don't think I came off right! What I am trying to ask for info on is not what system to run the motor on i.e. diesel/gas but the best type of dynamo, generator, alternator with brushes or brushless etc. the motor that actually converts the energy to electricity.

And yes Geof I will be getting a licensed electrician to install thanks for the pointer.





Be courageous. I have seen many depressions in business. Always America has emerged from these stronger and more prosperous. Be brave as your fathers before you. Have faith! Go forward!” Edison

[Geof]

Dynamo, generator and alternator are pretty much synonymous terms. Nearly every electricity generating device these days is an alternator; the one in you car has diodes to rectify the output because you need DC but for mobile generator sets which output AC this is not done of course. All of them will have brushes running on sliprings for exciting the rotor.

[martinw]

Originally Posted by screenzzzz Now, I maybe on the wrong site for this and then again I might not! so I figured I'd ask anyway. I am looking to build my own standby electric generation system and would appreciate opinions on the best type of generating motors. I am looking at 12kw and 24kw and something that can run 7/24 for long periods if necessary. Thanks Gary Be courageous. I have seen many depressions in business. Always America has emerged from these stronger and more prosperous. Be brave as your fathers before you. Have faith! Go forward!” Edison

Dear Gary,

What do you want to generate the electricity for, and why? None of my business really, but if you could tell us your supply problem in a bit more detail, better men than me will advise.

Best wishes,
Martin

[screenzzzz]

To answer Martins question 1st, I have not been that electrically inclined but, I am getting more and more interested. Expenses are high, electric bill is high, where can I cut back in the long term.

I have a river, wind and sun why am I paying for electricity? I am looking for a way (through trial and error) to create my own power, I have the time and want to try a bunch of methods. Initially I am not looking to hook into the house, when I get to that point I'll hire a pro.

Geof, Thanks for the basics! Now for the real question, What is the best alternator out there as far as compact, longevity and reliability.

[TOTALLYRC]

24 kw is a lot of power to get from the sun or the wind, at least on a trial and error based budget. The river sounds good, but if I remember correctly, the amount of power that can be extracted is based on the vertical drop, as it is ultimately gravity that provides the power to move the water to turn the generator and the Sun that provides the power to put the water on the top of the hill in the first place.

I am in the process of setting up a small cogen station for my house. I have a lpg powered Onan generator and will be using it to power my work shop and the waste heat to heat/suppliment the heating of my shop. If the waste heat is sufficent, I will also use it to preheat the hot water for the house winter and summer. Since all of the efficency losses wind up as heat, I will use the propane I would normally use to heat the building to first turn the generator and then heat the shop. I could also use power to run electric heaters so that all of the energy goes to heat the shop. My only real problem/question is wether or not it will be cost effective enough to make it worth while.

Since I already have the generator(got it cheap), and backup power makes sense, since the power is unreliable in the winter due to all of the monster trees in town, not to mention all off the idiots who hit telephone poles, I will install it anyway and try it out.

I will keep watching for your progress.

Mike

[martinw]

Originally Posted by TOTALLYRC 24 kw is a lot of power to get from the sun or the wind, at least on a trial and error based budget. The river sounds good Mike

Dear TOTALLYRC,

That was a brilliant post.

Cogen has a lot going for it. If you can use the "waste" heat, you are doing a whole lot better than powerplants that work at about 40% efficiency in electricity generation, and p@ss the rest away as heat up the cooling towers.

The river does sound interesting though. I have heard that "in-river" turbines might be a whole lot better than conventional ones, and that they do not require a head like conventional ones. There are , of course, all kinds of practical difficulties like weed clogging etc etc.

Thanks,

Martin

[TOTALLYRC]

In river turbines still need water velocity to turn them, so if the river has a slow current, you may not get all that much power, but I know nothing about them, so I will see what you come up with.

Good fuel injected engines, ie; internal combustion engines are at best 50% efficent IIRC, and my Onan, being flat head style, is definitely less, so not using the waste heat would be a sin.

At work they were looking into some cogen stuff, like 2 megawatt and there were 2 ways to size them.
One way was electrical load, and the other was heating load. You could have lots of heat production, which would be used to make steam for the steam heaters, or you could decide how much electricity you wanted and then deal with all the heat. I think we were going to base it on the heat output and then take whatever electricity it gave us. It would have been a 5-6 year break even.

There are also AC/cooling units that take heat input and give cool air as an output, but I forget the name of them. Using these will improve the overall efficency of the total system, but of course drive up the initial cost. I would like to investigate a small one for my shop but I think it will be too expensive.

[Geof]

Originally Posted by TOTALLYRC ....There are also AC/cooling units that take heat input and give cool air as an output, but I forget the name of them. Using these will improve the overall efficency of the total system,...

Absorption cooling, I just Googled to confirm it. More than a century old and displaced by electrical motors and mechanical cooling but likely to make a comeback as it is possible to use solar heat to run them.

You cogen idea is good, I have a diesel gen set that runs my home machines and have as yet unfulfilled plans to collect the waste heat for heating my workshop in the winter. I even included a loop in the exhaust piping that can be removed and replaced by a heat exchanger. My plan is to have a few hundred gallons of water which is used as a heat reservoir when the diesel is running.

Your comments on engine efficiency I once thought about with regards to a natural gas powered cogen system. Methane has a very high octane rating so it should be possible to run at a higher compression ratio which of course gives a higher expansion ratio and higher thermodynamic efficiency. If the electrical amount is configured with ballast resistors heating water so that the electrical load is always constant the motor can be desigend for a very very small rpm range again increasing efficiency and the exhaust could drive a turbine and high speed alternator to serve all the parasitic loads on the motor. I think overall a very high efficiency could be obtained.

[TOTALLYRC]

Thanks Geof, that is exactly what I was looking for.

I was thinking of building my own, but with the chemicals involved, I am not so sure.

If we heat cool and generate electricity, is it called tri-gen????

Once the work shop is a little more complete, I will be working on setting up the generator, as it is a good idea to have some sort of backup power.
Sounds like the basis for a build thread.

Mike

[martinw]

Dear TOTALLYRC,

I forgot about the Fiat Totem that appeared in Europe in about 1980. I saw one running at a low energy exhibition at about the same time.

It is a small (900cc?) automobile engine that is enclosed in a highly insulated box. It generates electricity, and the waste heat is used for heating the house. The engine was modified to run on household gas (gaseous), not automobile gas (liquid). I think it produced about 15kW.

I have no idea about its efficiency, but condensing boiler technology has evolved since then, and might be employed on a Totem style gizmo.

Google "Fiat Totem". You may have better luck than my brief search.

I still like the river though...

Best wishes,

Martin