[LDES-technology] LDES Tech assessment meeting - Nov. 18

[Sarah Kurtz]

I haven’t done very well about confirming agendas, so I’ll try to do better this week:
Our plan is to discuss the survey – if you didn’t complete it yet, please fill it in along with your feedback and return to Noah and Rui.

Russ also suggested some questions for ETES as a follow up to our meeting last week. This is a complementary (collecting specifics about the company) approach to the survey that Rui developed, which is a standardized survey that would ask everyone the same questions and not try to collect specifics.
I suggest that we start with the discussion about the survey that Noah and Rui circulated and then try to take a few minutes to talk about the complementary approach.

For your reference, here is what Russ drafted.

Dear Maximillian and Daniel,

Thanks very much for your time on Wednesday to introduce the ETES technology to our team. It was very informative.

In order to accurately reflect the technology in our capacity planning software tools, we will need information about the cost expectations and technical properties. I can imagine several use scenarios:

  1.  Use as a daily cycle ~10-hour storage for making “baseload” energy supply from solar + wind (mostly solar) energy
  2.  Use as a multi-day storage facility with say 72-hours storage enabling such “baseload” systems to achieve steady power through several days of bad weather
  3.  Use as a deep-winter interseasonal multi-GW facility, in which it might need to store energy for 3 months and discharge almost continuously for a couple of weeks in mid-winter
  4.  Use as an off-taker for energy that would otherwise be curtailed, and supplying industrial process heat (leaving open the question of how the industrial need can be satisfied in the winter when there is no such excess solar energy available
It would seem to me that for the first two cases, ETES competes with many other emerging storage technologies including batteries, flow batteries, potential energy systems (off-river pumped hydro or moving weights), etc., whereas for the latter two cases ETES offers some characteristics that those other solutions could not readily offer, and would mainly compete with hydrogen or other electro-chemical storage approaches.

I think our team would be happy to include ETES in capacity expansion scenarios for all of the cases above, although #4 is particularly challenging because our model does not extend to non-electricity energy loads (but we could potentially account for it as a revenue flow from curtailed energy and thus capture the economic benefit).  Thus far our team is fairly sure that the biggest challenge for a 100% carbon-free California electricity grid will be assurance of adequate capacity through the winter, and that some type of interseasonal storage will definitely be needed; and it also seems likely that there will need to be some remuneration of a generation facility operator for providing the winter reserve capacity, since the system will be fully charged and discharged just once per year.

Can you help us to assess the technology with the following data / forecast of future ETES systems?

  *   Capital cost

     *   Needs to be divided into cost per GW of power capacity and per GWh of storage capacity, and the storage capacity cost may need to be represented as a function of intended charge hold time (e.g., due to insulation costs).
     *   Needs to include a forecast of future costs through 2045 as the technology matures and production of components increases — this could be an estimated learning curve or (better) specific forecasts in 5-year intervals through 2045, accounting for both learning effects and market growth

  *   Operational costs for maintenance
  *   Power ramp rate

     *   Output power for dispatchability
     *   Input power for initial energy capture (sort of reverse dispatchability)
     *   Is there a difference in the charge versus discharge rate? Or this is an engineered property?
     *   Is the ramp rate a function of the size of the storage reservoir?

  *   Self-discharge rate

     *   What is the expected self-discharge rate for the various applications? E.g. it might be reduced for the really long duration storage by better insulation

  *   Depth of discharge

     *   For electricity generation this would correspond to the minimum exit temperature to operate the steam turbine, compared to the maximum temperature

  *   Round-trip efficiency

     *   This may be a function of the exit temperature and thus to the charge state
     *   I think we also need the one-way efficiency to evaluate the industrial process heat option

  *   Expected operational life of the system (which drives levelized cost of storage) in years, and/or in cycles
I’m sure I’ve missed something even after this long list. We will welcome any data you can provided addressing the above needs, as well as any comments or questions.

I have one additional design question if you would care to comment: what considerations led you to choose air as a heat transfer fluid, rather than water?

Best regards
Russ Jones  ☼   Jones Solar Engineering  ☼   +1-714-206-2556 (m)  ☼   +1-310-469-9045 (VOIP worldwide)


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