10 findings on the growth of hybrid power plants

Nexamp provided energy storage for two community solar farms located in the grid-constrained ISO New England. The Clark Road community solar farm (pictured has 7.1 MW solar capacity and 3MW/6.1 MWh storage. (Courtesy: Nexamp)

Jo Seel & Will Gorman, Lawrence Berkeley National Laboratory

The rapid deployment of wind was one of the most important trends in the electric power system of the 2010s.
Turbines and photovoltaic arrays are two examples of the potential for rapid development. However, early data suggests that there may be a new twist in 2020.
deployment of ‘hybrid’ generation resources.

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Hybrid power plants combine solar or wind power (or other energy sources) and co-located storage.

Just as cost declines drove last decade’s wind and solar expansion, falling battery prices and growing needs to integrate variable renewable energy generation are driving plans to deploy hybrid power plants.

At the end of 2021 there were more than 8000 MW of solar and wind generation connected to storage in the US. There are thousands of solar hybrids, totaling 280,000 MW of solar power and 208,000 MW storage, that have applied to connect to the grid. Even if only a quarter make it to commercial operations, they will have significant impacts on grid operations. Hybridization can help to balance variable demand and supply, but it is still relatively new. Research is needed to facilitate integration.

Grid operations and economics are complicated when you combine the characteristics of multiple energy storage, conversion, and energy sources. System operators, regulators, planners, project developers, and system operators would all benefit from better data and methods to estimate the costs and system impacts of hybrid projects. Hybrids offer a huge opportunity as we move towards greater renewable energy. However, their implications and optimal uses are still not known.

This publication showcases some of Berkeley Lab’s robust research program intended to support private and public-sector decision-making about hybrid plants in the United States. This brief summary summarizes articles we have published in the past two years. It also links to in-depth reports and gives contact information for further discussion on specific research topics. The graph below summarizes our recent top ten findings.

Figure 1: Summary of the Top 10 Findings from Berkeley Lab Research. Below are the Summary of All Findings
  1. Hybrid power plants are attracting strong developer interest.The rise in variable renewable generation and falling battery prices are driving interest in hybrid power plants. There has been a 133% increase of operational capacity (from 2020 to 2021) due to falling battery costs. Current interest is focused on the combination of solar photovoltaic and batteries. There are 286 GW of projects for PV+storage in interconnection queues by 2021. However, there are many other generator-storage pairings.
  2. PV+storage hybrids are low in PPA prices and have high value in certain regions: Reviewing power purchase agreements (PPAs) gives us insight into hybrid plant configurations, pricing, and timing. These agreements are often executed many years before a plant is operational. PPA prices have dropped from $40-$95 per megawatt-hour-PV in 2017 down to $30-$75 in 2021 (Figure 2). While the cost of adding storage to PV is around $10/MWh-PV for a battery sized to 50% of the PV’s capacity, we’ve found value gains between $8-21/MWh-PV, depending on regional and dispatch assumptions.
Figure 2: Levelized PV Hybrid Price Index (PPA) Prices have fallen in recent decades, despite the fact that the battery:PV capacity ratios have risen.
These numbers have increased. Open circles are sized to reflect battery-to-PV ratio; standalone PV plants are the
Filled circles are smaller than sized.
  1. Tax credits and other benefits are driving solar hybridization: Hybrid plants that are co-located with hybrid plants: Although hybrid plants can benefit from tax credits and construction cost savings, hybrid plants with co-located renewable generation generators and batteries may be subject to siting restrictions. Berkeley Lab found that hybridization has a rough equivalent to its costs and benefits. This suggests that local market conditions and configuration choices can have an impact on the values of hybridization (Figure 3).
Figure 3: The penalty of co-locating generation/storage is sensitive to modeling assumptions. However, colocation offers some cost benefits and incentives that may outweigh this penalty
  1. Market prices have incentivized PV batteries of shorter duration.Berkeley Lab used wholesale prices from 2012 to 2019, and a simple model of battery degradation to compare the costs and revenues of different hybrid designs. Hybrid net value has the greatest impact on battery capacity and duration, with batteries of short duration (2-4 hours duration) providing the highest value. The local solar contribution can play a significant role in determining net value. Overall, we found that hybrids were most attractive in CAISO and that solar hybrids had a higher net-value than wind hybrids in most regions—trends that align with commercial activity.
  2. A hybrid’s capacity contribution is less than its parts: The contribution of hybrid projects to the total capacity varies depending on their configuration and operational constraints. Berkeley Lab has created a simple algorithm that calculates the capacity credit of hybrid plants. It is suitable for exploratory analyses. While sharing hybrid project infrastructure may save money, it could also reduce the capacity value.
  3. Ancillary service markets can be a valuable, but fleeting, option for hybridsBerkeley Lab analysis has shown that hybrid projects can unlock significant value in AS markets, at least in certain regions. This could result in additional revenue of $1-33/MWh. However, AS markets are limited and can be overcrowded by battery projects currently in interconnection queues. ISOs/RTOs had an average of 60-800 MW in regulation reserves per year, compared with 289 GW of hybrid and standalone storage in their interconnection queues at the end of 2021. Owners of wind and solar hybrid projects may be cautious about expecting additional AS revenues to offset declining energy or capacity value.
  4. Hybrids are more flexible in engaging with electricity markets: Hybrid projects are more complex and open to multiple configurations, which increases the chances of bidding in electricity markets and dispatching. Developers will be able evaluate the risks and benefits of operating hybrids as one unit or multiple parts with different capabilities. The Federal Energy Regulatory Commission has not yet issued specific electric storage rulings.
  5. Hybrids’ power system value is dependent on how they are used.: A PV+storage hybrid plant’s operational strategies are a key driver of market value. This is in addition to technical characteristics such as location. Berkeley Lab used empirical data for analyzing the value impact on different battery dispatch options. These dispatch strategies can produce large increases in private revenues relative the standalone PV design (approaching 150/MWh) but they don’t optimize storage dispatch for the grid perspective and so often produce lower wholesale premiums ($1-$48/MWh). As the hybrid sector expands, it is becoming more important to understand the battery charge and discharge signals and align incentive structures with grid requirements.
  6. New opportunities arise from the growth of customer-sited hybrid PV+storage systems: Approximately 30% of U.S. battery storage capacity was installed through 2020 in behind-the-meter (BTM), with a lot of that being paired with solar PV. Still, only 6% of residential and 2% of non-residential PV systems include storage nationwide, although these “attachment rates” can be as high as 80% in Hawaii. Storage to BTM PV can increase the total cost of installation by $1000 per kWh.
  1. Where are we going next? Priority areas in hybrid power researchHybridization of power plant offers the opportunity to reduce the burden of managing intermittent renewable resources. However its novelty means that it requires research to promote integration and facilitate innovation. Berkeley Lab’s ongoing work focuses on themes of hybrid valuation, market rule development, and customer resilience opportunities.