Revision as of 20:13, 1 April 2020

Initial Notes

3kW hr of energy storage at 8 bar requires 65 cubic meters of volume - [1]. Low Tech Magazine on Compressed Air Storage.
- This is 510 cubic meters. But air is free.
But - if you use high pressure, you can reduce that volume down to 300 bar simply using a $300, 1800W Scuba compressor. (can this handle methane or hydrogen? )
Scuba compressor on AliExpress - $300 - [2]
80 cu ft tanks cost $200. That is 2 cubic meters. They are rated for 3000 psi. Standard is 200 bar [3]
For DIY - take schedule 80 steel pipe.
510 cubic meters reduced by 200x is 2.5 cubic meters or 90 cu ft
Take 12" Schedule 160 pipe at 2700 psi rating [4].
A 20' stick of this pipe gets us 15 cubic feet. Need 6 of these pipes to provide 3 kWhr of energy. That pipe is over 100 lb/foot!
Would need 3kWhr PV array to generate the pumping power if we assume 16% overall storage efficiency. This storage efficiency is brute force - would need to look for more efficient expanders. But 6 of these are 12000 lb of steel!
Solution: (1) go to slightly lower pressures. (2) Possibly 3D print plastic pipe. (3) Use automotive high pressure tanks. (4) Use more efficient systems - improve from 16% officiency to 50% efficiency or up to 85% using methods discussed in Low Tech Magazine link above
Schedule 80, 8" pipe may be better- [5] - weight of 43 lb/foot. 1/2" wall.
Or Schedule 40 8" pipe - 1000 psi - 30 lbs/ft [6] - $600 in cost per 20 foot stick.

Cost per 1kWhr of storage compared to $300/kW/2 years. 18650 Battery Life.

$159 for 10 feet of 4" Sch 40 pipe - [7]. Pipe Chart shows 660 PSI working pressure, 5000 PSI burst. Volume - 0.9 cubic foot.
$207 for 10 feet of 6" sch 40 - [8]. 4000/530 PSI. 2 cubic feet vol. 20% better than the last.

6" PVC - schedule 40 - $40 for 10 feet. PVC Pipe. 180 PSI working. Volume - 2 cu ft.
1" polyethylene rolls - 200 PSI -
12" - $12/ft - [9]. 8 Cubic feet. 10 atm. So 80 STP cubic feet. Need 90' for 1kW storage - or $1100 in PVC off the shelf.

133 cu ft - $2500. [10]. Say 10 atmospheres. 1330 cu ft STP gas. This makes it possible to store 1 kWhr is a 500 gallon propane tank.

12" pipe at 10 atm - weighs 11 lb/ft. 110 lb/10'. 5 day prints with Supervolcano nozzle.
Appears to cost $16/foot - [11]

Even off-the-shelf at $1100 for PVC - it does make sense to capture 1kWhr - very inefficiently! Because lifetime of PVC pipe is 100 years - so this is effectively equivalent to $100/kWhr battery storage costs!
Simple air with PVC pipe is a long-term energy storage option.
Unlike metal tanks - it won't corrode from the inside from moist air.
This is considering very low conversion efficiency (40%?)

Volume Calculator
Baseline for air storage: 20 cubic meters (700 cu ft) STP per 1kWhr storage.
Tesla warranties cars for 8 years or 150k miles, with 70% of battery life left. [12]. That is pretty amazing.
Cubic meter = 35 cubic feet

@@ Line 31: / Line 31: @@
 *12" pipe at 10 atm - weighs 11 lb/ft. 110 lb/10'. 5 day prints with Supervolcano nozzle.
 *Appears to cost $16/foot - [https://pvcpipesupplies.com/12-x-10-schedule-40-pvc-pipe-h0401200pw1000.html?gclid=EAIaIQobChMIuOXZ8IHI6AIVReDICh0FYQyXEAQYBiABEgIaSPD_BwE]
+=Conclusions=
+*Even off-the-shelf at $1100 for PVC - it does make sense to capture 1kWhr - very inefficiently! Because lifetime of PVC pipe is 100 years - so this is effectively equivalent to $100/kWhr battery storage costs!
+*Simple air with PVC pipe is a long-term energy storage option.
+*Unlike metal tanks - it won't corrode from the inside from moist air.
+*This is considering very low conversion efficiency (40%?)
 =Notes=