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<p class="MsoNormal"><span style="font-size:11.0pt">For discussion<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Helvetica;color:black">Hi Jeremiah,<br>
<br>
Thank you for your email. Here are a few comments.<br>
<br>
1. I feel Antora team did not specify their medium. Additional to the literature, the team we contacted from NREL has developed a novel heat storage medium and we could add it into the analysis.<br>
2. The unit could be unified when we put all technologies together and I feel it is fine for them to change the unit by their own for now.<br>
3. Yes, I correct it. It might be a typo when they calculate the RTE.<br>
4. For Antora, it is interesting they have provided the degradation on RTE per year and thus, the range of the efficiency can be estimated based on this loss per year and the designed lifespan.<br>
5. The energy and power are not separated. They are calculated the same system but with different units. It is common to assume the whole system in most literature I read. Additionally, we have the clarification in the note that the total system is a composition
of storage system, power conversion system, balance of plant. However, it seems there are still some miscommunication as the total capital cost could not add up. For example, the the PCS+BOP+storage system=1000$/kW not the 800$/kW.<br>
6. Since the survey is for the reference system, a clear product, we assume it could be easily converted from $/kW to $/kWh.<span class="apple-converted-space"> </span><br>
7. The rating, according to EIA’s definition:<span class="apple-converted-space"> </span><br>
A manufacturer's guaranteed performance of a machine, transmission line, or other electrical apparatus, based on design features and test data. The rating will specify such limits as load, voltage, temperature, and frequency. The rating is generally
printed on a nameplate attached to equipment and is commonly referred to as the nameplate rating or nameplate capacity.<br>
For the rated power/energy of the reference system, it can be a single value as it is a well-defined product or a range as a customizable product.<br>
<br>
The deliverable size is the product that the company could or intend to deliver. For example the Energy Vault build tower but they may not able or not willing to build a tower as high as Empire State Building in NYC. Taking the battery as another example, usually
there is a voltage limit for a single cell determined by the chemistry. Series connection could increase the voltage of the system but not infinitely as the internal resistances become non-negligible. Also, some limits are set by some business and economic
consideration.<span class="apple-converted-space"> </span><br>
<br>
<br>
Happy new year.<br>
<br>
Best,<br>
Rui<br>
> On Dec 30, 2020, at 12:42 PM, Jeremiah Reagan <</span><a href="mailto:jreagan@ucmerced.edu"><span style="font-family:Helvetica">jreagan@ucmerced.edu</span></a><span style="font-family:Helvetica;color:black">> wrote:<br>
><span class="apple-converted-space"> </span><br>
> I meant to send this your way a bit earlier but got sidetracked. You don't have to reply right away, I just wanted to send this out before I forgot further.<br>
><span class="apple-converted-space"> </span><br>
> Last week, Sarah and I were going over the tables (and considering breaking off a chunk to write mini-paper for an upcoming PV conference next year) and attempting to fill in the row for Thermal-PV using the info we got back from Anterra. From that, we made
a few notes for further clarification that I'm supposed to send your way.<br>
> • While we have a response for footprint (about 1 m2/MWh), we don't have anything regarding energy density of the storage itself. Right now we have a placeholder range of 80-500 Wh/L from the Luo paper for the wide variety of thermal in general. Also,
it's not entirely clear if that footprint value they're giving is strictly for the storage medium, or if it's actually inclusive of all the other bits that would go into a site.<br>
><span class="apple-converted-space"> </span><br>
> • Our self-discharge column measures in weekly %, while Anterra sent back daily %. We were wondering whether we should change either the table or the survey so they both match up in the future.<br>
><span class="apple-converted-space"> </span><br>
> • There seems to be an error in Cell 44B of the survey that is dividing by 100 twice instead of the presumably intended once.<br>
><span class="apple-converted-space"> </span><br>
> • As our entries in the tables are intended to be ranges, we really need to nail down the attached uncertainty on values being sent back. For example, they send us back a discharge efficiency of 45% and we're unsure whether that's 44.5% to 45.5% or
if they're rounding to the nearest 5%, making it 42.5% to 47.5%. This applies to all the singular numbers they send back our way, leaving us guessing ranges out of them.<br>
><span class="apple-converted-space"> </span><br>
> • Regarding the economic info, we're not entirely clear on why there's a row for units of power under Storage System Costs. My understanding is that that would be entirely be a matter of energy since that should only cover the storage system. On a
related note, I'm not entirely sure if they're reading the section the same way I am. If the two separate lines of "Total Capital Cost of Reference System" for energy and power are actually separate energy related costs and power related costs, or if they
are just the total cost of the reference system divided by that system's energy in one, and divided by power in the other.<br>
><span class="apple-converted-space"> </span><br>
> • While we have a Fixed Power O&M cost on the survey, we were thinking that we should also add one for Energy. Unless there is some reason why the storage system wouldn't have fixed O&M costs associated with it.<br>
><span class="apple-converted-space"> </span><br>
> • An extra one I'm throwing in, that I thought I had a grasp of at the time, but now realize I'm still hazy on. What are our "Rated Energy Capacity" and "Rated Power Capacity" columns supposed to mean? I took it to mean something like the Energy/Power
capacity of a stated reference system put up as a sort of example test case. Sarah seems to be certain that this should be a range of values, as in the Luo paper, with a minimum deliverable system size and some kind of maximum. The problem being, that maximum
isn't always going to be very well defined (we have a placeholder maximum of 100 times the minimum value), unless there's some threshold of efficiency inherent to the technology that sets an upper limit on the scalability. I could understand a range of typical
values if this was a survey of multiple companies that had already implemented multiple sites, but that doesn't sound like it would work well with less mature tech that hasn't been widely adopted yet. Is there something I'm missing in this Rated Power/Energy
definition?</span><span style="font-size:11.0pt"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="color:black">From: </span></b><span style="color:black">skurtz@ucmerced.edu<br>
<b>When: </b>8:00 AM - 9:00 AM January 6, 2021 <br>
<b>Subject: </b>CEC project Technology evaluation - Jan. 6<br>
<b>Location: </b>https://ucmerced.zoom.us/j/4364884550<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Our first meeting next year, we can revisit version 5 of the spreadsheet to make sure there are no further changes – please think about whether it’s ready to start collecting the data.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">We can also talk about how more data gathering with the companies has gone and what our next steps are.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Have a wonderful holiday!</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Sarah</span><o:p></o:p></p>
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