Kevin Quirion, Contributor
One of the diversion dams on Cache la Poudre River in Colorado near Fort Collins supplying water for farmland irrigation, fall scenery with gold foliage and low flow. Credit: Shutterstock.
Many hydropower plants are fed by reservoirs that are used by homeowners, boaters, swimmers, hikers, wildlife and others. The operating license issued by the Federal Energy Regulatory Commission (FERC) may have conditions that require a minimum water release to benefit wildlife, tourism and recreational activities. Historically, the main generating units of the dam have produced the total electrical output of the plant, but these units are not designed to operate during very low flow periods of the year and may periodically be shut down for other reasons. During these times the water flowing through the minimum flow system has not been harnessed to generate power.
Constructing a small powerhouse adjacent to the dam to capture electricity from the continuous water flow required can do more than supplement generation; it can change the model for power markets. Owners of hydroelectric power projects can become continuous power producers, maintaining a unit connected to the grid at all times. Therefore Independent System Operators (ISOs) may allow owners to use other generating assets to swing during peak times, maximizing profitability by supporting electrical usage during peak demand.
By establishing an extremely efficient, compact powerhouse and fast-tracking project construction; the payback on the new powerhouse can be greatly improved.
The Case For Minimum Flow Projects
Minimum flow projects can be developed with minimal impact on the environment and communities — taking advantage of generating capacity from existing impoundments. These run-of-the-river hydroelectricity projects typically involve small-scale generating capacity, yet can have dramatic impact on overall system profitability.
Generating power from a minimum flow system, owners can provide a uniform power source for base load requirements. The regional or independent transmission organization (RTO or ISO) may then allow project owners to use the energy generated from the rest of the system to meet peak power demand and therefore profit more from the rest of the system’s generating assets. There may also be renewable energy grants available for these projects. Overall, there is a powerful case for developing minimum flow systems.
With that said, most minimum flow projects require a multi-year process that involves applications for license amendments and related meetings and studies, as well as the manufacture of turbine and auxiliary equipment and engineering development.
How To Determine if You Can Benfit from a Minimum Flow Project
The first step is an analysis of existing generation assets and expansion potential. It may be possible to take advantage of existing infrastructure to reduce project costs. Beyond looking at the existing system, the impact of the new capacity on the entire system should also be assessed.
Remote circuit breaker racking. Credit: Eaton.
Once the basic, upfront analysis has occurred and the new generating system is designed, the value of the minimum flow project can be established. This typically accounts for energy, capacity, reserves and any renewable energy credits available. The energy calculation should account for additional generation for day-ahead and real-time market bidding or for selling forward, capacity factor, and operations during peak and off-peak hours. Project owners may be well advised to also evaluate capacity and the potential to contract capacity with others in order to hedge long-term price risk. Utilizing minimum flow assets connected to the grid virtually all of the time, power producers can dispatch other units into the spinning reserve markets.
Powerhouse Design Considerations And Best Practices
Constructing a powerhouse for hydroelectric facilities typically is complex. There may be limited space to store equipment, inconvenient site access, tight project schedules and coordination with other system assets that may include aging electrical equipment. A project partner able to provide turnkey services from start to completion can help reduce risk of project delays and problems — yielding a safer, more reliable and cost-efficient power system.
Key design aspects include safe and reliable switchgear, system monitoring and control. Switchgear provides centralized control and protection for power distribution equipment, while the monitoring and control systems allow local and remote access to real-time data — providing the information maintenance personnel need.
The switchgear installed at hydroelectric facilities has been known to operate for several decades. It is critical that the equipment employed is designed to enhance safety, protect personnel during routine maintenance and maintain production reliability. Front access only designs minimize space requirements with a small footprint and allow for flexible location of equipment within a facility. Today’s most innovative equipment can even extend arc-resistant ratings during routine maintenance.
The 24/7 nature of the power generation business makes remote telemetry critical in any location, particularly at automated, unattended plants. The control system can allow project owners to optimize output, enhance reliability and manage the facility remotely. Smart phones can allow operators to remain informed of plant status and alarm conditions and even provide access for remote control. This is accomplished using a mixture of technologies including SMS text messaging of alarm conditions generated by the station HMI, automated status and production reporting via email and even remote access and control through web-enabled smart phones.
Best Practices for Small Hydroelectric Power System Designs
1. Engage with service organizations that can take the project from start to finish and provide a single point of accountability.
2. Engage with a single team to design, construct and commission the project.
3. Work with manufacturers able to provide a high-level of technical support, not just during the project, but also after all the equipment is installed and commissioned.
4. Ensure suppliers can provide product and technology training.
5. Look for project partners able to reduce procurement cycle times and help expedite the project.
6. Full function factory acceptance testing for switchgear, protection and controls, and generator simulator can minimize on-site time and construction costs.
7. Manufacturer-created wiring harnesses can further drive down costs.
8. Remote racking mechanisms for switchgear help advance safety by providing a means to remotely insert or remove circuit breakers and auxiliary drawers – the technology helps increase the distance between the operator and live components.
Switchgear with type 2B arc-resistant ratings. Credit: Eaton.
To further extend safety during maintenance, projects can incorporate industry-leading switchgear designs that extend type 2B arc-resistant ratings, even with the instrument and breaker secondary terminal door.
According to the U.S. Energy Information Administration, an additional 250 GW of power will be needed by 2035 in the U.S. Minimum flow projects can help meet this demand sustainably and help owners improve profitability. Robust service organizations are helping advance minimum flow projects and improve costs and system performance — to maximize project return on investment. ◑
Kevin Quirion is an engineer and manager at Eaton.