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Solar with Battery? Nuclear with Hydrogen? What's the Best Hybrid System?

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Rakesh  Sharma's picture
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I am a New York-based freelance journalist interested in energy markets. I write about energy policy, trading markets, and energy management topics. You can see more of my writing...

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Hybrid systems, i.e., those systems that combine energy sources, have become a popular option in recent times. However, a plethora of sources – from solar to hydrogen to nuclear – means that utilities and ESCOs have multiple options for energy generation.  

So, what combination of hybrid energy systems provides the best results?

Recent analysis by the National Renewable Energy Laboratory (NREL) attempts to answer that question. Unfortunately, the analysis fails to reach a satisfactory conclusion and provides little in terms of specifics or metrics to evaluate such decisions.

That said, there might be some takeaways for designers and engineers of hybrid energy systems.

The first one is that the inclusion of solar panels provides a key cost-to-benefit ratio in hybrid systems. “The highest value architecture today varies largely based on PV penetration and peak price periods, including when they occur and how extreme they are,” the authors write. That conclusion is not surprising considering that the economics of solar energy are becoming cheaper by the day.

Within the context of a PV-based system, there was no clear architecture or sizing configuration that proved an outright winner. Even combining PV with battery storage systems does not offer substantial difference in benefits as compared to installing each system separately, the authors write.  

The second takeaway is that hybrid energy systems can reduce overall generation costs. The primary cost reductions occur mainly through shared equipment materials, labor, and infrastructure. Coupling two systems together also multiplies the value of each. For example, a PV system runs the danger of becoming less efficient with age. But combining it with battery storage can prolong its utility by shifting its use to periods when it can provide most value. The battery storage also benefits through increased total revenue from displacing grid-charged energy that might otherwise be expensive due to less efficient systems. However, the analysis fails to provide numbers or use cases to substantiate its assertions.

The third takeaway is that hybrid systems may not always be a panacea or solution for problems relating to incorporation of renewable energy in the grid. “Hybridization can actually reduce value, if the systems are not appropriately configured – which means appropriately sizing and coupling the battery and likely oversizing the PV array relative to the inverter or interconnection limit,” the authors write. They do not specify an optimal combination size, though.

To be sure, it is still early days to determine optimal hybrid energy configurations for utilities. Much of this is due to the fact that, depending on how far along they are in the decarbonizing their setup, utility grids have different compositions.     

Caitlin Murphy, senior NREL analyst and expert on hybrid energy systems, told Scientific American that the DOE has established a “hybrid task force” with NREL and eight other laboratories to fill in “gaps” in existing research. "It's crucial to determine the value that they [hybrids] provide to the grid — in the form of energy, capacity and ancillary services — particularly relative to deploying each technology separately," Murphy said.

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Bob Meinetz's picture
Bob Meinetz on Jun 23, 2021

"Unfortunately, the analysis fails to reach a satisfactory conclusion and provides little in terms of specifics or metrics to evaluate such decisions."

Rakesh, that the National Renewable Energy Laboratory fails to come to a satisfactory conclusion on how to evaluate hybrid renewable energy systems could have been anticipated. As promoters of renewable energy (it's in NREL's Mission Statement), they're in the unenviable position of figuring out how to portray meager, unreliable sources of energy in glowing terms. That, unfortunately, is their job.

Even in the best of conditions, powering an electrical grid with renewable energy is a challenging proposition. But the idea combining several unreliable technologies will improve the situation is, frankly, ass-backwards. Ask an engineer: unnecessarily complicating any system only makes it less efficient and reliable, and with renewable energy there is precious little energy or reliability to begin with.

The metaphor "out of the frying pan, into the fire" comes to mind.

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