Mobile Power Generation Maintains Grid Stability

Issue 11 and Volume 120.

By Frank Pizzileo

Many utility companies are turning to mobile power generation to ensure continuous service to customers during planned and unplanned outages. Photo courtesy: Aggreko

Today’s utilities face many more challenges than just a handful of years ago. Aging infrastructure compounded by peak season demands or natural disasters have placed an enormous strain on grids worldwide, thus increasing the risk for potential power outages. Further, a host of new, less traditional challenges are taking center stage which could impact grid stability: rising cybersecurity threats; more demanding consumers; an influx of unpredictable renewable sources; and, with the shift toward distributed generation, an increasing number of innovative competitors and the growing popularity of “behind the meter” (BTM) on-site generation sources.

Many utility companies are turning to mobile power generation to ensure continuous service to customers during planned and unplanned outages.

Power generation providers can get equipment into place very quickly to meet a utilities load requirements. These engineered solutions help utilities improve customer service by keeping customers energized while planned work is performed or restoring power more quickly during an unplanned outage.

Electric utility companies measure the reliability of their service in a commonly used metric called, Customer Average Interruption Duration Index (CAIDI), which quantifies the average outage duration that any given customer would experience.

When considering a mobile power generation solution, it is important that the temporary power system to be interconnected to the grid matches the specific requirements of the project.

Each temporary generation project is unique and has different needs so there is no such thing as one-size fits all. Therefore, it is critical to work with a third-party generation provider that has in-house technical expertise, such as electrical engineers, that understand how to design a power system that can seamlessly tie into each utility’s infrastructure and adhere to unique grid interconnection processes.

Utility companies worldwide are benefitting from the many advantages mobile power generation provides, from capital avoidance to improved customer service and emergency response plans.

The paragraphs below highlight just a few examples of why these solutions are commonly deployed in the utility industry.

  1. Meet shifting demands quickly with operating budgets Installing permanent infrastructure to meet seasonal demand can be impractical, time-consuming and costly. The right solution – for example a 50 MW plant – can quickly resolve capacity issues without requests for capital expenditure approval. Mobile reciprocating generators can be placed on-site in a matter of weeks, not years, and can be ramped up in only one to two minutes. This option also provides flexibility, where the demand is for a finite period. Finally, mobile generators can be applied to alleviate bottlenecks where transmission and distribution is constrained due to insufficient conductive capacity.
  2. Manage aging infrastructure repairs cost-effectively The massive T&D infrastructure in North America is aging and breaking down in many areas. Capital infusion to upgrade T&D infrastructure is forthcoming, but due to the scale of T&D investment needed, the necessary improvements will span over a couple of decades, rather than a couple of years. The modular design of mobile power generation units allow for rapid mobilization and demobilization, making them ideal for temporary projects where T&D infrastructure is being repaired, replaced, or upgraded. In addition, these temporary power projects can be designed to ensure electric service to customers is uninterrupted while the maintenance work is performed.
  3. Improve emissions and environmental compliance As restrictions on solid fuel plants increase in favor of renewable energy development, emissions controls are being set at ever-higher levels. Power generators using natural gas can provide a much cleaner and more cost-effective option than other alternatives – including diesel units – to reach compliance. They can also provide immediate power in support of green projects, such as wind farms when the wind is not blowing. When used for long-term, continuous operation, natural gas units have been shown to offer total cost savings of 40-45 percent compared to diesel units, primarily due to savings in fuel. Natural gas also burns approximately 85 percent cleaner than diesel.

Rent vs. Buy: Total Cost of Ownership Affects Choice

Once the decision is made to employ mobile power generation as a cost-effective solution, the next question becomes “is it better to rent or own generators?”

While ownership is often assumed to be the better choice, cost analyses consistently show that rented power generation equipment produces a better return on investment.

Because each situation addressed by mobile power varies greatly, and therefore requires different engineered solutions and equipment, utility plant owners’ inventoried generators rarely meet every need.

All too often, purchased equipment is deployed once, stored and then found either unsuitable for the next need or is long-forgotten in a warehouse, producing no long-term value to the purchaser.

Additionally, seldom-used owner equipment typically does not receive the appropriate maintenance or safety and emissions testing that rental fleets routinely undergo.

Because fleet management is a core competency of a power generation rental company, technician training, parts management, fleet availability and highly responsive service crews add significant value to the rental alternative when the true cost of ownership is calculated.

Continuous Power during Infrastructure Changes: A Case Study

Some electric utility companies prefer to outsource the majority of their mobile generator needs, preferring to focus on the T&D work and avoid the hassles (and costs) associated with regular maintenance of diesel driven gensets that is critical to ensuring reliable operation.

In the last couple years, Pacific Gas & Electric (PG&E) used Aggreko’s mobile generation solution to keep customers energized while they perform maintenance and/or upgrades to their grid infrastructure and substation equipment.

One such project took place when 10.5 MW of Aggreko’s power generation equipment energized more than 1,500 PG&E customers in San Luis Obispo County for 13 hours while upgrades were completed at the Cholame substation.

Sixty year-old 12kV distribution lines needed to be upgraded because they were too small to meet new demand. Without the use of these generators, customers in the area would have experienced a “planned” outage for several hours while this work was being performed.

In many cases, the customer is taken offline for incremental periods until the project is completed, increasing the utility company’s CAIDI.

However, whether the end-user is industrial, commercial, residential (or a combination), new types of electrical consumption (e.g., urban medical center) make any planned or unplanned offline incident unacceptable, even for short increments, regardless as to how much notification time is provided by the utility.

For these constraints, temporary power can be delivered without interrupting the customer’s service, such as with the planned Cholame substation outage, one of several dozen substation-level temporary generation projects that have been performed, confirming PG&E’s ability to utilize portable generation systems for both large- and small-scale projects.

Other PG&E projects have focused on improving the restoration time of electric service when an unplanned outage occurs on their T&D system. PG&E serves a large area where unplanned events such as earthquakes, landslides, and wild fires can’t be predicated, but power can nonetheless be restored more rapidly with portable generator units.

Whether the need is for 1 MW or 20 MW, the projects validate that mobile distributed power can deliver repeatable and scalable solutions. PG&E utilized outside expertise to resolve the challenges associated with modernizing a 120-year-old grid while minimizing impact to customers, and building a better proficiency for emergency deployment of distribution-level temporary power generation.

Upgrading a constrained section of the grid no longer means that thousands of customers must be taken offline for hours or even a few minutes. With temporary power solutions, generators can be synchronized so that the electric demand is transferred to the generators without interruption to customers.

In addition to planned upgrades and maintenance, numerous utilities are calling on temporary generators to restore power more quickly in response to unplanned outages. Whatever the application, temporary power solutions are utilized nationwide to help electric utilities provide reliable service to their customers.


Frank Pizzileo is business development manager for Aggreko.