Full Potential of Utility-grade Solar Requires "Intelligent" Management

Recently, the Solar Energy Power Association (SEPA) issued its “Top Ten Utility Solar Rankings” report [PDF], which indicates that utility use of solar doubled in 2008. SolarBuzz confirms this, stating that worldwide solar installations increased to 5,948 MW in 2008, up from 2,826 MW in 2007. So, it is clear that the utilities have a deep, vested interest in utilizing solar in the smart grid and are making an effort to deploy systems that will help them to scale their offerings to serve all markets.on

While increased interest in solar by utility customers is encouraging, there is a shift that still needs to take place to move from mere utilization of solar as part of the overall power portfolio mix to truly achieving utility-grade solar smart grid offerings. Because the total output of a single solar plant is usually far less than that of a traditional energy plant, many more renewable plants are required to produce a similar amount of electricity. As a result, managing solar electric power production requires a new technical and operational paradigm. 

The Paradigm Shift

So, what exactly is involved in this new technical and operational paradigm shift required to realize the full potential of solar in the smart grid, and how do we get there?

The primary technical and operational issues that need to be addressed to successfully implement solar throughout the smart grid include:

• Dispatchability — The ability to be able to turn solar services on and off at a moment’s notice.
• Stability — The ability to manage the fluctuation of grid currents caused by the introduction of solar systems.
• Manageability — The ability to effectively manage the different aspects of traditional and renewable energies as they coexist throughout the grid.

Dispatchability. One key element of any smart grid deployment is the ability to deploy power as needed, based on fluctuating demand. This is referred to as “dispatchability” of power. A “dispatchable” power plant is one that can be directly called upon by grid operators to produce power, and whose output can be modulated in response to real-time fluctuations in demand for electricity. Figure 1 shows a graphical representation of the systems needed to manage distributed, dispatchable power plants.

Figure 1. Fat Spaniel Technologies’ Solar Plant Vision is one example of an intelligent energy management system capable of managing many distributed, dispatchable solar power plants. A segment of Solar Plant Vision is shown here.

To enable a dispatchable power environment, smart grid operators must be able to coordinate power plant operations to handle the load on the grid at any particular time. Solar, however, is an intermittent power source — one whose distribution the smart grid operator cannot directly control, and, therefore, maintaining complete control over the dispatchability of solar energy requires a new approach:

• Higher solar plant density and greater distribution. First, it is critical that solar power plants be deployed in sufficient volume to make a difference. Since solar energy plants are only producing energy when the sun is shining, a greater distribution of them throughout the smart grid is also imperative.
• Availability. It is not enough to know how much solar energy is (or will be) available; you must also know whether each solar plant is operating at full capacity. For example, when a plant is under maintenance, or one or more components has failed (an inverter or sub-array, for example), the reduced capacity needs to be reflected in the calculation for the total amount of dispatchable power available from that plant.
• Battery and storage technology. This higher concentration of solar plants must be paired with complementary battery and storage technologies to enable the solar energy created during sunny hours to be effectively stored for later use. Pairing solar with wind, which typically generates electricity at night, is also effective.
• Granular control. Finally, smart grid operators can compensate for the intermittent nature of solar energy by deploying more granular control systems that can effectively predict weather patterns (to determine when the most solar energy will be created) and to create energy demand predictions. These control systems can help forecast and balance generation with demand.

So, even though solar is an intermittent power source, it is still capable of meeting the dispatchability need of smart grid operators. With the proper concentration of solar power plants, complementary battery and energy storage technology, and granular control systems, Smart Grid operators can effectively predict, store, and deploy energy as needed to ensure that everything keeps running, even when the sun isn’t shining.

Stability. Due to the variable nature of solar and other renewable energy technologies, it is not only critical to be prepared for the times when power is not being created (i.e., when the sun isn’t shining), but also the times when too much solar energy is being produced. The high amounts of power created by large solar plants on sunny days (or by wind plants, etc.) can overrun the current grid, which was not designed to have energy entering the system from multiple locations. As a result, this higher level of power entering the grid can change the harmonics of the grid, thus causing issues such as damage to grid transmission elements.

The existing grid was able to avoid this problem because it only had to deal with one-way power distribution. Power was generated at a central source, and distributed from that central source to the point of demand. Today’s grid is multi-directional; power is generated at multiple locations throughout the grid, with energy flowing back and forth from distributed solar plants to the central plant, from distributed plants directly to the point of demand, or from distributed plants to the central plant and then to the point of demand.

The higher levels of power being created, as well as the new two-way nature of distribution, can cause stability issues throughout the grid. To overcome any stability issues, Smart Grid operators who deploy solar and other renewable energy sources must also deploy energy management systems. These enable operators to manipulate parameters in inverters and other grid components in real time, enabling them to accommodate the fluctuating production and distribution needs of today’s Smart Grid.

With solar power plants deployed throughout the grid, the only way to cost-effectively ensure stability is to deploy energy management systems that can provide central control of many distributed sites. This requirement leads us to the final major technical component that needs to be addressed for successful deployment of solar in the Smart Grid:

Manageability. With the new operational paradigm of the Smart Grid — including the distributed nature of power generation sources — comes a need to adjust the IT paradigm of existing energy systems. In a distributed PV environment, where efficiency and cost-reduction are primary goals, it becomes hard to justify having on-site personnel at each solar power plant.

So, you now have a higher concentration of power plants, but you need to run them at a fraction of the cost of previous centralized plants. How is that accomplished?

This new operational paradigm requires the implementation of distributed Energy Intelligence systems, which are industrial-grade offerings that give utility companies fast, easy management with a comprehensive set of applications that include:

• Real-time plant management. Provides a full range of data collection, troubleshooting, and performance tracking for renewable energy component technologies, thus maximizing production while minimizing costs.
• Advanced analytics for optimizing performance. Provides complete analysis of system performance, identifies fault conditions, and provides proactive recommendations for resolving faults to increase performance and efficiency.
• Mobile and remote user capability. Enables the support of mobile personnel, as well as the ability to dispatch separately contracted third-party field service personnel.
• Revenue management. A suite of revenue-generating services, including agency reporting, renewable energy certificate (REC) registration, environmental reporting, and back-office integration.

These Energy Intelligence systems provide power plant monitoring and management via integration with a wide variety of components for data collection, inverter management, power metering, communications networking, and environmental assessment. Robust solutions are also available for wired and wireless communications, IT component failure detection, and end-to-end security.

Conclusion

Though the increasing deployment of solar technologies by today’s utilities and Smart Grid operators is encouraging, there are still a number of considerations that need to be addressed to truly achieve utility-grade solar. The requirement for many distributed solar power plants to be deployed to generate the amount of power needed, the variable nature of solar energy production, and the stability issues that can be caused when fluctuating PV sources overrun the existing grid all add a new level of complexity to the implementation of solar in the Smart Grid.

But the dispatchability, stability, and manageability challenges presented by solar in the Smart Grid can be overcome. The right combination of solar power plant density, complementary battery and energy storage technology, and distributed energy management systems can help today’s utilities take full advantage of the cost and efficiency benefits of today’s solar while preserving the dependability and predictability of the grid.

Acknowledgment

Solar Plant Vision is a trademark of Fat Spaniel Technologies.

Randy Rajagopal received his MS in computer science from the U. of Illinois and Urbana-Champaign, and studied Strategic Marketing of High-Tech Products at Stanford U. He is the director of product management at Fat Spaniel Technologies.