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Photovoltaic Advancements

image credit: 8MINUTE-Solar-Energy
John Benson's picture
Senior Consultant, Microgrid Labs

PROFESSIONAL EXPERIENCE: Microgrid Labs, Inc. Advisor: 2014 to Present Developed product plans, conceptual and preliminary designs for projects, performed industry surveys and developed...

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  • Nov 17, 2020

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The last deep dive I did on photovoltaic (PV) technology was about a year and a half ago. However PV technology is has been advancing rapidly since the above-linked post, and it’s time for an update.

Bob Meinetz's picture
Bob Meinetz on Nov 17, 2020

John, there's a common assumption "paired" solar and storage facilities are only storing energy from the solar farm. Yet charging their batteries from a grid mix would be a far more flexible and profitable use of their expensive investment.

What leads you to believe the batteries at 8-Minute Energy's Eland 1 & 2 solar/battery facility, shown in your photo, are only being charged by the solar panels on-site? If they're being charged by a grid mix, they're adding anywhere from 100-400 kg/MWh of CO2 emissions from resistance and bi-directional inversion losses.


John Benson's picture
John Benson on Nov 17, 2020

Hi Bob:

It might be more efficient from a physics standpoint to charge the batteries from the PV panels, and from a physics standpoint this is what will happen (electricity goes where it wants to). But from an economics standpoint, 8minute and LADWP probably don't care. The PV power will probably be sold to the highest bidder, consistent with other contract commitments. The power to charge the BESS will be bought from the lowest supplier (ditto).

Both transactions will also include transmission charges to move the power from where it is generated to where it is consumed. Given the low price of the PV power from this project, plus the lack of transmission charges to move the (probably DC) power from the PV arrays to the BESS, it is highly likely (all other things being equal) that power from the PV will be lowest cost and end up (contractually) charging the BESS. But the market will determine this, day-ahead and in real-time.

The success of PV+ storage has more to do with market-forces than the laws of physics.


Bob Meinetz's picture
Bob Meinetz on Nov 18, 2020

If the batteries are charging from a grid mix, proximity is irrelevant. Electrical energy travels at very close to the speed of light, thus they will be charged with the same mix of electrical energy whether the solar panels are adjacent or 100 miles away.

"But from an economics standpoint, 8minute and LADWP probably don't care."

Obviously they don't care - they're able to sell their electricity as clean electricity, whether it is or isn't.

"The success of PV+ storage has more to do with market-forces than the laws of physics."

Raising the question of whether the purpose of "PV + storage" is to enrich investors or prevent climate change. Their batteries are, depending on the current grid mix, creating an additional 100-407 kg/MWh of CO2, making it considerably dirtier than using no batteries at all. Thus it would be fraudulent to promote it as "clean energy," would it not?

Earth's climate, unfortunately, has a lot to do with the laws of physics (but at least it's honest).

"Bulk energy storage is generally considered an important contributor for the transition toward a more flexible and sustainable electricity system. Although economically valuable, storage is not fundamentally a “green” technology, leading to reductions in emissions. We model the economic and emissions effects of bulk energy storage providing an energy arbitrage service. We calculate the profits under two scenarios (perfect and imperfect information about future electricity prices), and estimate the effect of bulk storage on net emissions of CO2, SO2, and NOx for 20 eGRID subregions in the United States. We find that net system CO2 emissions resulting from storage operation are nontrivial when compared to the emissions from electricity generation, ranging from 104 to 407 kg/MWh of delivered energy depending on location, storage operation mode, and assumptions regarding carbon intensity."

Bulk Energy Storage Increases United States Electricity System Emissions

Matt Chester's picture
Matt Chester on Nov 17, 2020

Thanks for sharing, John. I'm always interested in trackers and why they don't seem to be more pervasive-- is it a cost/maintenance issue? Is the value-add not terribly great? Or is it just limited by practicalities like space (e.g. only larger operations would really benefit from them an appreciable amount)?

John Benson's picture
John Benson on Nov 17, 2020

Hi Matt, thanks for the question.

As per my answer to Bob, above. It's all about economics, and the economics for a solar project are really complex. In this case we trading the cost of leasing the land for the project vs. the cost of electro-mechanical assemblies (trackers). Trackers will make the project produce more power per acre, but so will higher output modules, bifacial modules, etc. The cost of land in rural inland Southern to Central California has traditionally been relatively inexpensive. But the price of trackers has been coming down (albeit slowly compared to modules which are heavily driven by silicon technology). 

As the paper pointed out, the use of trackers over time is increasing slowly.


Jim Stack's picture
Jim Stack on Nov 19, 2020

I agree that any storage of power is great. The GRID has not had real storage ever since it was created. Storing any excess and using it when it is a critical time is a great improvement to the GRID. 

John Benson's picture
Thank John for the Post!
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