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John Benson's picture
Senior Consultant Microgrid Labs

PROFESSIONAL EXPERIENCE:Microgrid Labs, Inc.Senior Consultant: 2014 to PresentDeveloped product plans, conceptual and preliminary designs for projects, performed industry surveys and developed...

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2020 Large PV and PV + Storage Update

image credit: 8minute Solar Energy

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When I recently posted a paper on U.S. Offshore wind, I commented in the Intro of that document that it had been almost a year since I posted a paper similar to that one. While writing the earlier paper I wondered how long it had been since I did a paper on the other major renewable generation technology: photovoltaic (PV) arrays. I looked and it had been well over a year, and thus this post. Also, since PV is often paired with storage in recent projects, I will include this duo. This paper will be limited to projects in the U.S. that are at least 100 MW and that are either recently completed, under construction or planned to be complete by 2022.

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Matt Chester's picture
Matt Chester on May 26, 2020

After doing the market research on what the solar+storage market can expect in coming years, what's your level of optimism that the addition of storage is going to elevate solar capacity/generation to new heights? Or do you think it will remain a costly add-on that's used more for things like frequency regulation? 

John Benson's picture
John Benson on May 26, 2020

Hi Matt. Thanks for the comment/question.

This intreststing thing is, that the answer is different for California (and other parts of the West) verses the rest of the US. I'm working on a paper on long-term storage (longer than 4-hr run time at peak output) that will be posted in Mid-June. The following is an excerpt from that.

I would give long-term storage, at best, a 50% chance of being able to compete in California in the future. This because our weather is really weird compared to regions in the U.S. Midwest and East. First of all we have lots of sunny days. The average for most of the state is 250 to nearly 300 days a year of sunny and partially sunny weather. This means we have lots of solar power, and this continues to grow rapidly. The other thing is that it is very dry. The seasonal peak period for most of the U.S. is summer. Ditto California, but with a difference. The time of peak load is in the late afternoon to early evening. However because of our arid atmosphere, as the sun sinks into the Pacific, our temperature drops rapidly. The further inland you go (where it is much hotter in the mid-afternoon and the air is dryer) the faster it drops. On most days where the temperature touches 100°F, it will be in the 70s by 9:00 or 10:00PM...

This weather means that a 4-hour peak capacity run-time is OK for BESS. This will allow its output to provide energy well past the peak demand time (typically 7:00PM to 8:00PM per CAISO), making it a reasonable add-on to solar (in the summer, solar drops to 50% around 7:00PM)...

Other U.S. regions with normal weather (read: high humidity and hot nights in the summer) require large amounts of base-load generation. As they push their power mix to achieve net zero GHG, and at the same time lose natural gas-fired and some nuclear generation, intermittent renewables plus long-term storage will need to take up the slack.



Rex Berglund's picture
Rex Berglund on May 26, 2020

It was recently announced that Form Energy  will be providing its 1st commercial low cost long duration storage product to Great River Energy, apparently an air breathing aqueous sulfur flow battery.

I'm curious whether you have an opinion on its ability to "take up the slack" for a mainly renewable grid, or if it's just too soon to tell.

Recently there have been some optimistic claims:

"A low-cost, long-lasting form of energy storage that could be built anywhere would be about the closest thing to a silver bullet for cleaning up the power sector. It would make the most of the sharply declining costs of solar and wind, without many of the environmental, safety, or aesthetic problems raised by other ways of balancing out fluctuating renewables."

"But the sun and wind don’t just fade for hours; sometimes they dip for days or weeks. If we want to shift mainly to renewables, we’re going to need a lot more storage that can last a lot longer."

Bob Meinetz's picture
Bob Meinetz on May 27, 2020

"Most of the winning projects will be co-located with existing solar farms that will charge the batteries, making them useful for integrating and smoothing the intermittency of the state’s growing share of renewable generation, as well as providing resource adequacy for times of peak demand in the late afternoons and evenings."

Here,  batteries are described as being "co-located" with existing solar farms "that will charge the batteries," implying that the batteries are only being charged by solar energy.

If the batteries are connected to the grid, however, they will be charged by a grid mix - whatever generation is available at that moment (that they're "co-located" with existing solar farms is irrelevant). Because the grid mix will include generation from a variety of sources, including gas, a California battery installation will add anywhere from 104 to 407 kgCO2/MWh to the emissions of delivered energy, depending on location, due to inherent system inefficiencies connected to transporting electricity to the storage system, bi-directional inversion, and resistance losses inside the batteries.

Alternatively, using only output from the solar farm to charge the batteries would prevent system operators from ever charging with energy from the grid, eliminating a potentially lucrative revenue stream.

What evidence do you have grid batteries co-located with a solar farm are charged by 100% pure solar energy from the farm?


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