What time of natural gas fed electric generator would you recommend? 2

[Hercules28]

Dear all,

Assuming I have a good high pressure supply of natural gas, what kind of electrical power generator would you recommend?

I am pretty new to the subject and was told to look into microturbines, fuel cells, turbine etc.

The facility that we are looking to power consumes about 3MWh per month or else 100.000KWh per day.

How would you comment on the different technological options? Capital investment/Efficiency
and do you happen to know major players in the market?

Thanks,

Herc

 

[MikeHalloran]

One data point:
One brand of microturbines, with recuperators, run on Diesel fuel, consume about 20 pct more fuel than a Diesel at the same power level. Revealed from fuel consumption curves provided by each manufacturer. This stuff does not appear in brochures; you have to dig deeper and get the details from every source.



Mike Halloran
Pembroke Pines, FL, USA

 

[EdStainless]

What peak generating capacity are you looking for? 4kW (your average) or will you need 10kW on less than 24x7 service?

Look at high performance diesels. With heat recovery and in some cases ORC turbines running off of the exhaust heat you can get some very impressive eff values.

Though you might consider using fuel cells and then fueling a diesel with the waste gas. Then add a bottoming cycle to this. It all depends what the eff is worth to you.

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Plymouth Tube

 

[MJCronin]

This is a tough call.....no one selection is best.

IMHO, I would consider looking at:

- Gas fed IC engine (as mentioned above) especially if there is a need for modest amount of waste heat

- Microturbines, gas fired if the load is continuous and there is a greater need for waste heat

- Used gas turbine ~ 4 MWe range if your electrical load will vary considerably.

Good luck !

Tell us about your electrical and thermal loads......

 

[ccfowler]

Unless you establish a clear understanding of the load profile and the actual significance of reliability during each segment of the load profile, you don't have the slightest chance of arriving at a coherent and useful conclusion. The previous comments indicating the significance of bottoming cycles or cogeneration options should be considered thoroughly as these can dramatically influence the wisdom of some options that you may wish to consider.

Beware of any form of gas turbines if the load profile dictates that it (or they) must operate for significant periods at reduced loading. Gas turbines, particularly combined cycle units, are capable of very high efficiencies, but those high efficiencies are only realized at full load. Their efficiency drops rapidly as the loading is reduced. It is not unusual for a gas turbine operating at synchronous idle to consume fuel at rates in the range of 80% to 90% of their full load fuel consumption rate.

From your posting, it appears that your system could be operating as a modest size "power island." If this is true and you have some proportionately very large loads that must be started, you would be wise to consider including diesel(s) to provide the required nearly instantaneous power increment while using other prime movers for the bulk of the generation capability. Dual-fuel engines (engine running a very lean mix of gas as the main fuel with about 1% diesel fuel serving as the ignition fuel) can serve this same function if the diesel injectors can be used to provide the large instant fuel requirement until the system can absorb and adjust to the large load increment(s). Unless their dynamic effects are properly considered, starting or dropping relatively large loads can cause very serious stability problems for a relatively small system. Unless there are some very unusual aspects to your system, it is most likely that a mix of several different prime movers will need to be included to optimize cost, load vsriation, and reliability needs.

Valuable advice from a professor many years ago: First, design for graceful failure. Everything we build will eventually fail, so we must strive to avoid injuries or secondary damage when that failure occurs. Only then can practicality and economics be properly considered.

 

[davefitz]

For many years the high price of natural gas had spelled economic doom for users of micro tubines- it was impossible to economically compete with a large central station gas fired combined cylce plants with their 50-60% LHV efficiency. And so Capstone stock tumbled the day after I bought it.

Today's low cost of natural gas ( in the US), projected to remain in the $2-4/ MMBTU for the next 20+ yrs, implies that the market for microturbines need not be limited to backup power demands , and that converting fleets of diesel power trucks to CNG is the next disruptive wave. It also means that developing IGCC is a complete waste of capital in the USA.