Margaret,
This is a great question. I'm excited to see how other facilities
approach this.
I am not yet charging my LHe users, but we are moving to a cost recharge
model (the current plan is to begin Jan 2024). I spent a lot of time this
past summer analyzing the past 2.5 years of data running our recovery
system and making projections for major repairs, annual LHe replacement,
etc. I have a detailed discussion <
https://chembio.byu.edu/cost-analysis
of how I estimate maintenance schedules and future costs and what the
resulting final price per L is, etc. An important thing to note is that
the price per L that you need to offset future maintenance costs will
change dramatically depending on the amount of He that you're recovering
per year (see comparison at the end).
Here's an overview of my facility:
*Facility/User Details:*
- CryoMech LHeP22 with automatic purifier
- Nominal liquefaction rate = 22 L/hour
- Observed liquefaction rate = 24 L/hour
- 6 magnet cryostats + 2 transfer dewar cryostats
- CryoMag PPMS (cycles from +9 T to -9 T), boil off = 26 L/week
- Bruker FTICR (~7 T), boil off = 4.6 L/week
- Varian DDR2 SS-NMR 500 MHz, boil off = 2.6 L/week
- NMR Facility, boil off = 5.4 L/week
- Varian Inova 30 MHz
- Varian DDR/VNMRS 500 MHz
- Bruker Avance Neo 500 MHz
- 2 LHe transfer dewars, boil off = 9.1 L/week and 15 L/week
- Total boil off = 63 L/week (9.0 L/day)
*LHe stats*
- I liquefy 5100 L of LHe per year (i.e., this is the amount I push out
of the collection dewar).
- I collect 3900 L of LHe in my transfer dewars (average flash is
23-24%; i.e., I collect 1200 L/year of LHe from the flash during transfer
dewar fills).
- I deliver 2700 L of LHe to the magnets (i.e., I collect 1200 L/year of
LHe from boil off to passively cool the transfer dewars).
- I collect 600 of LHe per year from the flash during magnet fills
(average flash of 23-24%).
- I replace 210 L of LHe per year from actual losses.
- That's 95% recovery relative to the 5100 L of LHe that I push out of
the collection dewar (that's when losses begin, be they leaks or transfer
losses, etc.)
- Or, 92% recovery relative to the 2700 L of LHe that are actually
delivered to the magnets (easier to compare with traditional measures of
LHe purchased)
*Costs*
- LHe added to the system to replace losses (210 L/year) plus UHP He for
regenerating the adsorber. Using current prices + 20% is about $7000/year.
- Projecting maintenance/replacement schedules and using current costs +
30% yields an average yearly amount that I need to recovery of about
$8000/year.
- The liquefier and purifier need oil adsorbers replaced every
20,000-25,000 hours. The current prices are about $2.5k to $3k with
replacement schedules of about 3.8 and 2.3 years.
- The cold heads need to be refurbished every 40,000 hours (both the
purifier and the liquefier). The current prices are about $6.6k to $7.5k
with replacement schedules of about 6.1 and 4.7 years.
- There are a variety of other parts to replace periodically
(purifier ground pin, liquefier purity sensor, tip seals for pump, etc.).
These work out to about $2k per year.
- Using the amount of LHe liquefied per year lets you estimate how
often this maintenance will happen so you can divide the costs over that
time period (plus a markup because future costs will be more than the
current price).
- $15,000 annually; delivering 2700 L/year = $5.66 per L of LHe
delivered.
- If I want to give users a credit for the flash gas that we collect
during magnet fills, I would need to bump that price up (for example, $6.25
per L LHe delivered with a credit of $3.12 per L LHe collected from
flash).
*Current Plan*
- I'm not currently planning to do the whole credit for flash gas
approach because I'm the one filling all the magnets, so I make sure the
flash gas is collected.
- The simple approach is roughly *$6 per L* of LHe delivered (i.e.,
removed from the transfer dewar) vs. our current price of *$26 per L* of
LHe from our vendor.
- However, more than half of our LHe production is a result of a single
user (the PPMS!) and for political reasons, I won't be able to charge a
single user $10k per year. My current plan is to have a *monthly cap of
$630* for LHe charges. That brings the price up to about *$10 per L* of
LHe, which is still better than the commercial price of *$26 per L*.
*Notes*
- With fewer magnets on the system, you spend less time liquefying, but
more time keeping everything cold. While this does result in longer times
between major maintenance costs, those costs are spread across fewer L per
year of LHe, so the cost per L goes up significantly for smaller setups. I
have used my statistics to estimate what the costs would be for other
scenarios:
- If I only had the 4 NMR magnets + the FTICR (i.e., remove the
PPMS), I end up with $8.60 per L instead of $5.66 per L.
- If I only have 3 NMR magnets (i.e., just the NMR facility), I end
up with $16.40 per L instead of $5.66 per L.
- The calculations above do not include the cost of electricity (I never
see an electrical bill - someone else on campus worries about that).
However, other facility managers expressed interest in how that affects the
numbers as some people do have to worry about electrical costs. Using the
rate for electricity that my university pays ($0.07/kWhr) I get
- $8.49 per L (with all six magnets on the system)
- $13.45 per L (without the PPMS on the system)
- $26.11 per L (with only the 3 magnets in the NMR facility)
Sorry if this is too much information, but I figured I would attempt to
give a big picture.
-Scott
On Thu, Sep 14, 2023 at 11:34 AM Eastman, Margaret margaret.eastman_at_okstate.edu> wrote:
> AMMRL:
>
> If you are running or participating in a helium recovery system for which
> users need to be charged for recovered liquid helium, please let me know
> how these charges are determined.
>
> I presume that over time working with the system, efficiency is
> established, and some ability to track recovered helium for example from a
> certain magnet and determine effective cost of liquid helium returned to
> that magnet is possible with experience, which takes time. But what
> actually is involved in doing that? Do you have a fixed charge per liter or
> something more complicated?
>
> I am also looking for a good starting approximation for what charges
> should be at the outset when we have no experience yet. Perhaps if you have
> a fixed price per liter for recovered helium and could let me know what
> that is as a percentage of the market price in your location for helium,
> along with the efficiency of the recovery system, that would be helpful.
>
> Thanks so much for any help.
>
> Margaret
>
>
>
>
>
--
Dr. Scott Burt
Professor
NMR Facility Manager
Department of Chemistry and Biochemistry
Brigham Young University
C414 BNSN / C008A BNSN
Provo, Utah 84602-5700
Phone: (801) 422-2404
Fax: (801) 422-0153
chembio.byu.edu/nmr-facility/
email: scott_burt_at_byu.edu
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