Maximizing Solar’s Grid Power
Over the past several years, renewable energy has become a major contributor to new generation resources on the electrical grid. This growth is driven by several factors including regulatory changes, state mandates and a rapidly changing mix in the overall generation portfolio. For example, the recent declines of nuclear power due to massive cost overruns and increased risk concerns following the Fukushima meltdown in 2011 have resulted in reduced dependence on this energy source. Likewise, coal is facing an accelerated decline due to expensive Environmental Protection Agency regulations and rising environmental concerns. With these traditional grid contributors declining, new additions to the generation mix have substantially shifted to natural gas and renewables.
Solar energy, in particular, is one of the largest areas of new generation currently added to the grid. Recent data shows that the solar share of new electricity generation in the United States has increased from 10 percent in 2012 to over 36 percent in 2014, with growth second only to natural gas. Further, the U.S. Energy Information Administration estimates that utility-scale solar capacity will continue to increase by more than 60 percent before the end of 2016. As solar energy penetration expands, finding more effective ways to store energy is increasingly important to accommodate intermittent resources. Due to this, many utilities and their customers are evaluating energy storage.
The potential impact on utilities is enormous. Integrated, grid-tied energy storage systems enable greater grid stability, while maximizing energy harvest and ensuring renewable energy investments pay off faster. Modern energy storage technology can also help utilities enhance reliability and reduce peak loading by facilitating shifting, ramp rate control and frequency regulation to improve grid stability.
The Challenges of Renewable Generation
As renewables continue to provide a larger percentage of our energy consumption, utilities may struggle to maintain frequency and voltage tolerances that result from generally uncontrollable sources. Solar and wind energy sources have inherent variations that simply don’t match up power delivery with utility loads, and rapid changes in production levels can occur in a matter of seconds. Grid-tied energy storage can rapidly respond to changes in environmental conditions by absorbing or delivering power to the grid and limiting the change in output. Additionally, these same storage systems can absorb excess power that would otherwise be limited by power ramp rates set by utilities.
Enabled by a relatively small amount of stored energy, ramp power can help control a solar farm to stay within the
limits set by the utility. Batteries, with effectively instantaneous power delivery capacity, also have a unique capability in meeting exceptionally high ramp rate requirements. Additionally, to manage demand, especially peak usage during the day, many utilities have peaking power plants that operate when needed. Yet, peaking power facilities are expensive to build, have a long return on investment and are commonly powered by unsustainable energy sources. Peaking plants also require water to operate, produce significant harmful greenhouse gas emissions and it is often difficult to find suitable sites.
Grid-tied energy storage, however, provides an ideal solution for meeting peak demands, as these solutions have the ability to adapt to changing grid conditions at speeds nearly 1,000 times faster than a peaking plant.
Illustrating the Benefits
To demonstrate the capabilities of large-scale, grid-tied solar energy storage systems, Eaton recently helped a major utility on the West Coast develop a 5-MW energy storage and microgrid demonstration facility. This energy storage facility is integrated with an existing distribution feeder and utility-dispatched distributed generation, forming a high-reliability zone. This distribution feeder needed to have sufficient energy storage and dispatchable generation so that it could be operated either connected to the traditional utility supply or as an independent island. Bringing this system online allowed the utility to demonstrate how renewable energy resources, combined with storage and local standby generation, can increase reliability and efficiency when integrated into a microgrid.
The intelligent microgrid combines solar and energy storage, with standby generators to create a high-reliability zone, which is able to detect faults and island a medium voltage feeder. This helped to improve service reliability. Inside of the high-reliability zone, a 2.5-mile smart feeder system provides reliable power for residential, commercial and light industrial customers.
Additionally, the energy storage system has sufficient capacity to support the microgrid for several minutes, creating a backup power supply in case of an interruption.
Through intelligent power management, the smart grid project can either store or release energy depending on real-time energy market conditions to optimize the generating facilities. The system can also prioritize renewable generation over fossil fuel plants, ensuring that the utility makes the best use of renewable energy that is already available
The Future of Grid-Tied Energy Storage
A smarter grid will enable better control of energy costs, reductions in energy requirements, more effective support of sustainability initiatives and improved power reliability. As the industry continues to make advancements in inverter and battery technology, systems will also become more compact and cost competitive. This will enable vast opportunities for economically locating storage exactly where it is needed. For example, Eaton is working with another major utility to develop grid-tied energy storage systems that can be deployed in distributed or community-based models — with the aility to intelligently monitor loads to provide real-time grid support and stability.
Advancements will allow these systems to fit on a traditional transformer pad, typically going completely unnoticed by community members.
If the local grid is overloaded, the system can signal an integrated inverter, which will then discharge energy from the battery to help reduce the peak demand. When fully charged, these community-based solutions could provide electricity to a typical community center, a light industrial complex or small residential street. Through constant innovation, the renewable energy industry is anticipating the needs, engineering the products and shaping the solutions that will help power the needs of tomorrow — and grid-tied energy storage will play a major role in reshaping the way our world consumes electricity.
Chris Thompson is the grid-power business unit manager for Eaton and has more than 20 years of experience with power conversion systems. In his current role, Thompson manages product lines for high-power inverters that connect both solar and storage systems to the grid. Prior to this, Thompson was the director of advanced power conversion for First Solar, where he was responsible for acquiring and connecting approximately 1 GW of PV systems to the distribution network. He also spent more than 10 years at Schneider Electric in various roles in Japan, Singapore and the United States.
— Solar Builder magazine