Integration Of Utility-Scale PV And Storage – Lessons From An Implementation

PNM demonstrates that battery storage can successfully integrate utility-scale PV but standards are lacking.
Published: Fri 28 Nov 2014

Combining storage with utility-scale PV generation opens the way for multiple benefits, including smoothing of this intermittent power source and peak shifting, Public Service Company of New Mexico (PNM) has found with its Prosperity energy storage project.

The project, which was supported with a US Department of Energy Smart Grid Demonstration grant, came on-line in September 2011 and was fully commissioned in February 2012. It has been running since then, with additional functionality being added over time. In a new case study by Jon Hawkins, PNM’s Manager, Advanced Technology and Strategy, for the Smart Grid Interoperability Panel (SGIP), the results and lessons learned are presented.

Prosperity energy storage project

The project  combines 500kW of fixed PV panels with a 500kW “ultra” lead-acid battery system (with integrated ultra-capacitor) for smoothing and a 1MWh advanced lead-acid battery (providing 250kW for 4 hours) for firming for peak shifting, peak shaving and storage arbitraging. Location is near Mesa del Sol, south of Albuquerque.

Data collection is through a PNM designed data acquisition system.

Among the results, the system was found to successfully both “smooth” and “firm” the output from the PV plant. PNM, which developed its own smoothing algorithm with Sandia National Labs, found that “substantial smoothing” was preferable to “perfect smoothing”, due to the energy saving that results. However, the question of what is the optimum amount of smoothing is still under investigation.

The smoothing was also found to result in a substantial reduction in the number of tap change operations.

In the peak shaving application a 15% reduction of the feeder load was demonstrated.

Lessons learned from the Prosperity project

The case study report states that the Prosperity project has been a really interesting, groundbreaking project, and it has demonstrated real world benefits.

However, in deploying such a new type of system, PNM needed to make the best of non‐matching puzzle pieces to implement a working solution. Some interoperability obstacles include:

● Standards are not mature in all areas

● Even with mature standards, vendors may not have implemented them yet

● Even when vendor equipment is compliant with a standard, it may not be interoperable with

another vendor’s equipment which is also compliant with the same standard

● Creativity is needed in integrating and utilizing legacy systems that are in place

● Organizational and cultural challenges related to the deployment and optimization of smart grid applications should not be discounted.

Further reading

SGIP: System Integration of Utility-Scale PV  Plus Battery Storage – Interoperability and “Lessons Learned”

Engerati: 42 Ways in Which Energy Storage Can Save Money or Make Money: Lessons Learned From Different Types of Projects