Diesel Cogeneration

[deltawhy]

Hello,
I have a client who wishes to go to cogeneration as the price of electricity is now making it economically viable. I have planned on using three diesel generators in parallel that will come on-line and off-line in response to real time demand load. I have estimated the system demand load to be around 300kW. Any heat rejected from the generators will be utilized by domestic hot water and air handling.
My question is: does anyone know of any environmental standards that would disallow such an arrangement? I believe I can prove the viability of the system, but if there are heavy environmental regulations surrounding this then that will become an issue. The location is Canada.

Thanks

 

[waross]

I would look at the economics of one or two generators. You don't have to use 100% output from a generator.
Look at demand charge savings from peak shaving as a plus and possible increased fuel consumption per KWHr at reduced loading as a minus.
Study the utility tariff; If a generator fails during peak usage you may incur a large demand charge and some tariffs may apply for a year after a peak loading event. The implications of this should be discussed with the client.
I would be looking at the plant load profile and then possibly evaluating the following sets or combinations.
1. 1 x 300 kW
2. 1 x 250 kW
3. 2 x 150 kW
4. 1 x 200 kW + 1 x 100 kW
5. 3 x 100 kW
6. 2 x 100 kW

It doesn't sound like this will justify the added cost of an N+1 system.
You will almost certainly need to meet the utility requirements to prevent islanding and/or backfeeds.
For 300 kW you may consider a UPS to provide grid back-feed protection and allow islanding.
A suggested control scheme would be to monitor the incoming current and use a load controller to load the generator (by fuel delivery) so that the demand on the grid is always a set low value.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[deltawhy]

Thanks for the response Bill,
I do have the building utility bill for the past couple years. I have calculated a peak demand of 400kW with an average demand of 300kW (used to calculate fuel consumption). As there will be no paralleling to the utility, the generators will be providing 100% of the building power. The utility will be used as a backup in the event of an outage.
The scheme of 1 x 200kW + 1 x 100kW seems like a good option. However, will load sharing become an issue in this case?

As such, I do not need to meet the utility requirements as there will be no connection to the utility. As well, I'm looking if anyone has experience dealing with certain environmental regulations pertaining to this type of setup.

Thanks again.

 

[catserveng]

On the environmental side it will all be in the hands of your local air quality agency. Not sure how it works in Canada overall but have worked some sites in Quebec and Montreal areas and air quality regulations were similar to Northeastern US.

It is doubtful you will be able to run units without some form of aftertreatment if your facility is in any kind of city, I know of some joint military complexes that use diesel powered on site generation with some heat recovery, but they have been in place for quite some time in remote areas, so I would imagine they are exempt from regulation.

Your best bet would be to find out exactly what your local air quality regulations will allow and if there will be any requirements for emissions controls, then from there you can start making decisions on sizing and equipment selection. You may be required to go with something like Tier 3 or 4 engines, and possibly SCR or particulate trap aftertreatment systems. If aftertreatment systems are required you may want to rethink grid parallel as operating in island mode, while can be done, makes emissions control in strict areas a lot harder.

Mike L.

 

[waross]

Hello;
Back power bills are one of the things I ask for.
However it would be good to have some idea of the daily load profile. How fast must you respond to an increasing demand? You may be able to save quite a bit of fuel if you arrange the controls so that major load increases are inhibited for a few seconds so that the load control panel may bring additional capacity online.
The local genset suppliers may be able to help with emissions information.
You may want to consider a system where some of the rejected heat warms the oil and coolant of the off-line sets.
This installation will be a compromise between economics, technical issues and the willingness of the plant operators to "live with" the system.
Can you share with us any information as to the type of plant? The type of loads?
If you look at fuel consumption data for a 400 kW set and a 100 kW set, both with an 80 kW load you will see why it is a good idea to try to keep the capacity matched to the load, and live with slow starts of some loads. Yes I know 500 kW and 100 kW is a little extreme but it makes the point and when you factor in hours per month the money adds up. You don't want a money saving system that ends up costing more than grid power.
Hint; I was in an area where many people had standby sets. Fuel cost on a gallons per KWHr were about one half of the grid price. The hidden costs of oil, filters repairs overhauls and excess fuel consumption at light loads was such that they all used grid power and used the standby sets for standby only.

Interesting project.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[cswilson]

I agree with Mike that the legality of this will depend on local environmental regulations. In California, it is virtually impossible to use diesel generators for electricity. During the California power crisis about 10 years ago, utilities couldn't get approval to run diesel generators even to avert blackouts. They tried to get waivers, but environmental groups blocked them, concerned about the precedent it would set.

Other areas of the US permit the use of diesel generators for peaking power into the grid. I don't know about the use for on-site generation.

 

[deltawhy]

Thanks for the responses.
The response to loads is one thing I have been thinking about. It is actually a commercial building with some residential, so I can't imagine the load will be able to change very quickly. I believe the largest motor in this system is 15HP. I imagine that when the load increases to 80-90% of the first genset the second will fire up. Warming the oil and coolant of off-line sets is a very good idea.

Thank you.

 

[dpc]

Maybe I missed it somewhere, but is there any chance you could use natural gas instead of diesel? Fuel cost will be lower (at least today)and emissions concerns reduced.

 

[deltawhy]

I would definitely like to use natural gas, but as the location is remote, it is not an option. Thanks though.