BLOG: Power Perspectives

[#1]

The utility in the U.S. is fairly reliable, but outages happen. To protect against outages, many industries (i.e. healthcare, telecommunications, and data centers) install back up power generation. But most standby generator sets operate for less than 50 hours a year (including routine testing). Utility curtailment is one method to help offset some of the costs of a back up power generation system.

There are many benefits to a utility curtailment program, including:

• Reduced utility rate
• Ability to earn revenue from your excess capacity

However, there are some factors to consider:

• Increased complexity (and cost) in the power distribution equipment
• More generator set run hours = more annual emissions, which may make permitting more difficult

Is this something you have implemented? What other benefits or challenges do you see? Are there other factors that need to be considered?

I am interested in hearing your thoughts on this topic. Please post below.

[#2]

One idea is to save more money rather than make money by adding co-generation (CHP) equipment to the genset. You can sell the excess power to the grid and also harvest the heat for many different applications.

[#3]

If it is a Diesel Standby Generator you first calculate the Cost per kWh generate & compare with utility costs,ie  per unit, max demand kVA charges.

Consider additional costs for preventive, & predictive  maintennace costs , say every 250hrs service or 500hrs service, up first major overhaul say 10000 hrs. You need to consider access permit requirement for the emergency , or periodic maintenance (say for telecom data centeres, and high sequrity areas where high cots involved), and how remote this site for quick access to repair.

Then you can compare with other income options, and costs associated with those if you operate this unit .

Various operating options are indicated as follows;

Consider Peak shaving or peak sharing options. In peak shaving option ; if your peak load align with utility peak time frame then it is better to go for time of day tariff structure and operate the generator during this peak hours. Typically , this peak hours start from 7.00pm until 10.00pm ie 3 hrs per day, and therefore, 1095hrs  per year. Typical operation for standby rated generators are limited to 500hrs per annum which will be an issue for peak shaving option. If your Generator is prime rated or your load factor is less than 60% then you could select this option. If you select this option you have to operate every day during peak hrs to maintain your max demand (kVA) at min level . If you miss one day you cannot save from your max demand for that partucular month.

In peak sharing option you sign a contract with utility (may be simialr to utility curtailment), and install rebate meter from utiilty. You can decide when you want to run the Generator or not ; not like peak shaving. If you have spare capacity to export this would be an ideal choice.

Depending on the type of applications you may need to incoporate synchronising control panel and additional protections to existing systems to facilitate soft transfer back to utility. This would be an additional cost and additional admin / legal work to satisfy utility requirements which you have to sign a connection agreement with utility as a embeded generator (refer, G59 Codes for less than 5MW).

Utilities usually demand following study reports before you connect your Generator to their system (either short time Soft transfer or long time parallel running operation);

Protection Study (this will be required from third party independant consultant - Additional cost)

Stability study (if more than 1MW)

Operating procedures

Maintenance Procedures

Also,  you need to consider how you monitor this operation . If it is a standy mode generator and running 50hrs per year you may not require a permanent operator, and you can remotely monitor the operations.

If you operate this unit with utility you may need a dedicated opeartor or switching person with (for HV switchgear ) licence, and this will be an additional cost.

If this is a new site you can compare installing a Natural Gas operated Continuous rated Generator running 24/ 7 with a Diesel Generator option, and with CHP option.

Best Regards

Sumudu

[#4]

I need to draw your attention in a different direction of application. This may be technically feasible depending on the size of the unit and site load behaviour.

Data centers, telecom sites some times operate in leading power factor and requires a special Generators that can operate on leading power factor. Therefore, for applications which has  leading / and lagging power factor requires a tailor made generator set suit the site operating conditions and will be a special Generator set. In this case if Generator can be decoupled from the Engine using a clutch Generator can be used for power factor improvement at the site.

When utility power available then Generator is disengaged from engine and operate as a synchronous condensor, and should the power fails then Generator will be engaged to the engine, and can be used as a backup power.

[#5]

Interesting indeed!.......I operate and maintain @ 60 diesels in the standby/peak shaving mode for the Municipal Utility industry  @150Mws worth and would like to offer some comments to the previous posts....( I'll try to separate them out so bare with me)

Data centers, telecom sites some times operate in leading power factor and requires a special Generators that can operate on leading power factor. Therefore, for applications which has  leading / and lagging power factor requires a tailor made generator set suit the site operating conditions and will be a special Generator set. In this case if Generator can be decoupled from the Engine using a clutch Generator can be used for power factor improvement at the site.

Integrated grid operators (MISO for my area) are indeed very interesting in standby units ability to create vars.  The idea of separating the gen and motorizing it  to act as load and pull the grid power factor up has been researched at length.  We discovered that the cost of clutching a gen to the power producer is complicated and cost prohibitive at best. In the upper Midwest there has only been one attempt at this and it was on a smaller CT. We also found the generator manufacturers are not enthused about the idea!. 

MISO is currently seeking equipment data from generator operators specifically generator VAR curves.  Just about half of our "fleet" now consist of Cat 3500 and 3600 series diesel gen sets. As many already know it is not recommended to operate these machines in a leading power factor. In fact most if not all of ours have automatic PF controllers  set to operate within specific range and protection against leading. The rest of our units are comprised of what I call "old tech" machines i.e. Coopers, Enterprise,Nordberg, Fairbanks. Superior.  These units DO have the ability to produce VARS by running the generator in a leading condition. There are some drawback to this mode of operation. Making VARs produce heat in the generator over an extending it may cause wedges to loosen and insulation to break down. It also increase wear ion the engine and increases fuel consumption. We are currently assessing the cost to run in this mode as MISO will offer grid VAR support in it's ancillary service market. It should be noted that the MAJOR cause for this need is the amount of Wind Power being tied to the integrated grid but I think thats a different discussion.................

Various operating options are indicated as follows;

Consider Peak shaving or peak sharing options. In peak shaving option ; if your peak load align with utility peak time frame then it is better to go for time of day tariff structure and operate the generator during this peak hours. Typically , this peak hours start from 7.PM until 10.PM IE 3 hrs per day, and therefore, 1095hrs  per year. Typical operation for standby rated generators are limited to 500hrs per annum which will be an issue for peak shaving option. If your Generator is prime rated or your load factor is less than 60% then you could select this option. If you select this option you have to operate every day during peak hrs to maintain your max demand (kVA) at min level . If you miss one day you cannot save from your max demand for that partucular month.

The majority of system transmission (69KV and up) grid owners/ operators have specific prohibitions against peak shaving and distribution  under 69kKV)operators in most cases have PPA (power purchase agreements) that prohibit it as well. The operation of units "behind the meter" is difficult at best even with a system control center.Cost of power fluctuates minute to minute. with various peaks during the day both morning and afternoon. for the last 2 years real time energy cost have been well below the cost to operate a oil fired generator or any size. The chance of any one individual monitoring the cost are dispatching engines is poor indeed (we tried for 2 yrs and lost bad). We currently have put  our units "in front of the meter" These means that the Grid controller (http://www.midwestiso.org/home dispatches our units and pays us for that service. It also means that we have to comply with some very complicated procedures including GADS (With the permanent Resource Adequacy Requirement (“RAR”) filed with Federal Energy Regulatory Commission (FERC) on Dec 27, 2007 – Midwest ISO is requiring generating resources designated as capacity resources submit generator availability data. Documents related to Midwest ISO’s Generating Availability Data System (GADS) project are posted here. Stakeholders are requested to send any comments/questions related to the content to this email address: gads@midwestiso.) If you care to take time to review the MISO link it may help answer some questions.

As for the original point of this article I suggest that owners of standby units in search of a revenue stream look into selling the capacity from those unit to their utility. You have to come up with a cost that considers more run/maint time the you may be used too  and you have to relinquish some control but it worth real dollars. We currently pay 2.00 to 3.00 dollars per kw and haven't called units to run in a year.....

Todd

[#6]

The problem with what you are proposing is that by getting an economic benefit takes the generators from being emergency generators to non-emergency generators; which is a very big distinction for air permitting.  For example, in the Northern Virginia non-attainment area, the air permits for data center emergency generators explicitly state that if the permittee wishes to use peak shaving or load regulation (non-emergency generation), they must add SCR.  I am sure that come January 2011, that will change to being interim Tier 4 compliant (SCR and PM add-on controls), instead of remaining Tier 2 for emergency generators.

In NJ and in the San Francisco Bay Area, non-emergency generator SOTA (state-of-the-art for NJ) and BACT (best available control technology for BAAQMD) is to operate the generators burning natural gas because it is the lowest achievable emission rate of NOx, VOC, PM and SO2.  You won't even get an air permit for a non-emergency generator that burns diesel fuel in those jurisdictions.

I suspect the rules in other non-attainment areas are pretty much the same.   There is a huge difference in potential to emit for 50 to 500 hours per year (for emergency generators) and for 8,760 hours per year (non-emergency generators).

So, if you are going to negotiate the lower electrical rate, make sure that you add-in the cost of add-on pollution controls.  For a typical 2 meg emergency generator, that is about $500K per generator.

[#7]

Keep Engine as Stand By application . Use alternator as Synchronous Motor  along with Inverter /converter section , flywheel.   Advantage of using this system will be - "Power Factor improvement ( By angle adjustment in voltage and current waveform ), Harmonics Filteration  and it will serve for NO BREAK SYSTEM ".  Whenever power failure takes place synchronous motor acts as a alternator , and prime mover will be flywheel . After some seconds engine as a prime mover comes and will fed the load , Also after EB recovered flywheel will discharge thro alternator for short period and EB will fed to load.

So ultimately  Load will not observe any power outage.

Shailesh Andhare