Diesel Genset or Gas Trurbine for 300kW System

[moeen]

Reaching out to all the seasoned folks, what would you use if you were to provide a 300 kW power generation system? A diesel genset or a combination of gensets, or a gas turbine. I dont want to include solar in the discussion.
A quick pro/con summary would be great. I know this is not directly a PLC question, but I am sure there are plenty of knoweldegable people on this forum who can shed some light on it.
Reliability ranks high on this project, followed closely by cost.
Thanks in advance.

 

[iant]

and ...
Sorry mate - what are you asking
Surely as the system you want is cost driven.
this is also dependent on fuel and load demand.
So a lot more info please.
Are you doing a Uni Course?

 

[moeen]

Thanks iant.

Well this is not a uni course, I am investigating a real life power generation system in a remote rural area in Asia. The peak demand in the beginning is expected to be about 250kW, hence my interest in a 300kW system. The fuel available is diesel, kerosene, and natural gas. But I want to stay away from natural gas as my understanding is that gas gensets need lot more servicing.

 

[Lancie1]

...a real life power generation system in a remote rural area

Those two words mean you should go with diesel, because there may be a few local mechanics that can work on a diesel engine, but probably not any within 500 miles that can service a gas turbine.

 

[moeen]

Thanks Lancie.

My (brief) understanding about diesel gensets is that they dont like being run underloaded, i.e. they are more efficient when operating at about 65-75% of their full capacity. Does that mean I should try to go for multiple sets of 100kW each?

Another concern is cost, I do realise that I dont have many options, but would somebody have a rough cost of per kWhr (capital and ongoing)for a diesel genset system that would produce roughly 300kW.

Thank you for your time gents.

 

[Lancie1]

Does that mean I should try to go for multiple sets of 100kW each?

Using several smaller units has some advantages for a remote rural area. The ability to adjust for smaller loads may be very useful until the villagers are able to buy more electrical appliances. At first they will have very few things to run with the power. Also, if they can't keep 3 units running, they might rob parts from one to get 2 generators running. But then with 3 units there will be temptation to remove parts off the non-running units to use in tractors and and other machines!

I once went to the Costa Rican jungle to start up a generator to power the village of Horquetas. That generator ran off of wood gas (gas from burning wood). It was a German modified hybrid-diesel engine that had spark plugs. The wood gas was generated by burning scrap wood (from the local logging industry) in a reactor, collecting the gas and piping over to the wood-gas engine. I think it was a 250 KW unit. About 2 years later, I heard that the Costa Rican power company ran a utility line into the village, and the local farmers took apart the equipment to get the parts.

 

[BobB]

Chicken poo load. I rarely work with sets under 1000 kW these days and often 4-9 mWatts.
If the peak load is 250 kW I would suggest you require 2 x 300 kW sets so that one is online and the other is being maintained.
Diesel would be best - long way to go to maintain a gas engine. Generally speaking gas engines are absolutely useless if there is a load step of more than perhaps 8% of total capacity - they die. They are also generally cranky. Best to check with the manufacturer - and question them because generally they will lie to you to get the sale.
Diesel generators generally do not like being loaded under 40% - they are pretty inefficient also at that load - so are gas engines. Diesel engines run below 40% start to slobber - leak oil and the cylinders get glazed.
For control I would look at 2 x Woodward easYgen controllers - they are good and available from PM Controls in Sydney - I use them all the time. A screen is also available to mount in the panel face and manual control is available from the screen. That way you can synchronise and ramp load up and down to transfer from one generator to the other. There are cheaper brands out there but I will not use the majority of them for many reasons - have been doing emergency generator and power station systems for nearly 20 years now - learned a bit in that time. Had a look the other day and have done over 300 generator jobs in that time.
You have to have full redundancy in these types of application.
You are in Sydney - so am I. Contact me via PM if you wish. I can tell you plenty of pretty nasty stories about generators and installed systems. You also have to consider compatible alternators etc. Great when you put 2 so called compatible alternators together and find 2000 amps of circulating currents between the 2 on the neutral because 1 is 2/3 rds pitch and the other is 5/6 ths.

 

[Chris Taylor]

Well some interesting comments, so I’ll thru in my two bobs. A few years ago I spent 18 months in the Philippines installing and commissioning a few hundred small (500KW) diesel sets for the small island grids. (Plenty of stories for another day). There is one thing I learnt. Keep it very simple.

For the most part these installations don’t need spot on frequency control, so an electronic governor is not necessarily required. Is an electronic set controller really needed, BobB is right the Woodward EasYgen is a good bit of kit but if it fails 200K by boat from the nearest agent you may find an old fashioned relay based system your friend. Synchronizing can be achieved with three lamps and load sharing can be done manually using droop settings just like it was for years before the digital processor.
The same goes for engines, digitally controlled engines are great for the environment but you can’t do anything with them without a laptop and increasingly an expensive license.
There nothing wrong with advanced kit, you just have to make an assessment regarding maintainability, too often manufactures supply up their standard product (cos its easier to make) into installations that aren’t suitable from a local maintenance. The local population may not have the funds to keep getting agents engineers to attend and the equipment just becomes junk.
A gas turbine will need less maintenance and the load factor is less of an issue but the cost is very high.


Chris

 

[Lancie1]

There is one thing I learnt. Keep it very simple.

For this type of project, that sentence cannot be said too many times. Complicated equipment will become someone's yard ornament.

 

[BobB]

Synchronizing can be achieved with three lamps and load sharing can be done manually using droop settings just like it was for years before the digital processor.

I would never go back there again I can assure you - seen too many generators crashed together and badly damaged - one lot I saw was done by a qualified RAAF power station operator - destroyed 2 alternators and knocked one engine off its mounts - not pretty. Too many knobs too twiddle.

The same goes for engines, digitally controlled engines are great for the environment but you can’t do anything with them without a laptop and increasingly an expensive license.

Pretty hard to find one that is not electronic these days - also virtually impossible to buy the software and interface cable - try buying one from Caterpillar or MTU for example. That being said electronic engines rarely cause a problem - they are pretty reliable but there are a couple of brands I would never use by choice.
If both engines are the same the cost of carrying a spare easYgen and front panel is really quite inexpensive and it could be loaded with the settings and left to standby.
In another direction, I am just commissioning a job where I had to use 2 x easYgens per generator - 1 online and the other on standby. I had to program the PLC to change them over each month and reset the resultant alarms. If the online one fails, switch to the other one. Stupid thing is the most common problem that has gotten me out of bed at 2AM over the years is batteries and/or battery chargers. I normally use 2 chargers and battery sets and combine them through bridge rectifiers for redundancy of DC supply. On this job the failure of a battery charger or battery set is acceptable but the far less likely failure of a generator controller is not acceptable. Fail to work some consultant engineers out sometimes.

 

[iant]

I would never go back there again I can assure you - seen too many generators crashed together and badly damaged - one lot I saw was done by a qualified RAAF power station operator - destroyed 2 alternators and knocked one engine off its mounts - not pretty. Too many knobs too twiddle.

Pretty hard to find one that is not electronic these days - also virtually impossible to buy the software and interface cable - try buying one from Caterpillar or MTU for example. That being said electronic engines rarely cause a problem - they are pretty reliable but there are a couple of brands I would never use by choice.
If both engines are the same the cost of carrying a spare easYgen and front panel is really quite inexpensive and it could be loaded with the settings and left to standby.
In another direction, I am just commissioning a job where I had to use 2 x easYgens per generator - 1 online and the other on standby. I had to program the PLC to change them over each month and reset the resultant alarms. If the online one fails, switch to the other one. Stupid thing is the most common problem that has gotten me out of bed at 2AM over the years is batteries and/or battery chargers. I normally use 2 chargers and battery sets and combine them through bridge rectifiers for redundancy of DC supply. On this job the failure of a battery charger or battery set is acceptable but the far less likely failure of a generator controller is not acceptable. Fail to
work some consultant engineers out sometimes.

I remember the 3 light method shown to us during our third year apprenticeship 32 years ago - let it rest in peace.
as BobB has stated look at the area and redundancy or Maintenance requirements. I have worked at a kids camp in Licola it has been powered by diesel gensets for more than 35 years. they recently replaced them all, due to old age.(the area was an old logging camp 30 plus older again)
Still Diesel and 50km's (1 Hour drive) away from support.

 

[KalleOlsen]

Diesel engines run below 40% start to slobber - leak oil and the cylinders get glazed.

Gosh, I didn't know this. Is there a theory behind, or is it empirical?

Kalle

 

[Chris Taylor]

BobB
Your probably right about the three lamps, prehaps a synchroscope (as one consultant described once as the "plus and minus meter"), I suppose my point was that a consideration of the local maintenance abilities should figure quite high when developing a scope of equipment.


Electronic engines are reliable but when somthing goes wrong it can be tricky to find out without a laptop and the CAT/MTU/ANOther engineer. a simple oil presssure switch problem can end up causing two/three days down when on an older engine it could be fixed in a jiff.


I'm not saying its worse now, because for the most part its not, just horses for courses.



KalleOlsen



The theory is quite simple, the cylinders don't run hot enough and result in unburnt fuel and oil deposits in the exhaust manifold which causes slobbering, also as the pistons are not hot enough the rings don’t seal as well as they should and so oil is pushed passed, increasing the slobber but also leaving mineral deposits on the inside of the liners as the oil burns. This is a particular issue for generators as they are constant speed machines, a few hours on full load can usually sort out most cases but can also set the silencers on fire if you’re not careful, done that before now



Chris

 

[KalleOlsen]

@Chris
Thanks for the info!

Kalle

 

[iant]

I hate to put the cat amoungst the pigeons...
But.
Wouldn't it be a good - expensive - idea if the syncroscope became a secondary available system and use a full blooded automatic switching system.
The manual system being an option rather than the only way.
there are both negatives and positives for this
But it is worth thinking about it