# Pumped Hydroelectric Storage

## Contents

# Basics

- A Form of a "Gravity Battery" using water as the mass
- Essentially Hydroelectic Dams but modified to work "in reverse"
- So it functions as usual, but can be reversed, or use seperate pumps to store energy

# Marcin Calculations for FeF

Calling the engineers in the audience - I just ran through some calculations on the feasibility of water pumping storage at Factor e Farm, our facility. The numbers look really good on paper. The drawing shows two quarter acre ponds - the contour lines are at 1 foot elevation intervals, so 30 foot drop between the ponds. The calculation yields 24kWhr of energy storage from this using proven microhydro technology - where the elevated pond serves as a reserve that can be pumped during daylight for gravity water storage. This is an open call for review of the calculations, see below.

Explanation:

Can we consider a storage hydro system that pumps during the day and generates electricity by night? Quick calculations: 1/4 acre pond, 6 foot deep. That is about 2000 cubic meters of water. Take another pond 10 m lower. The energy of water going from pond 1 to pond 2 (see drawing attached) is MgH = energy = [2000 cu m]x[1000kg/cu m]x[10 m/s^2]x[10 m] = 200 MJ 200 MJ = 200 MW for 1 second, or 200 kW for 1000 seconds, or 2 kW for 100,000 seconds - but assume 50% system efficiency (85% pumping, 85% generating, then 20% friction loss)

THAT IS over 24 HOURS OF 1KW OF POWER!!!!!!!!!!!!

Note Pelton turbines are 90% efficient [1]

Cost will be $1.5k in 4" pipe (about 1000 ft), $1k in power equipment, $10k in excavation + trenching for 2 ponds. If we have our own dozer, that will be $3k system cost. $3k for 24kWhr ($125/kwhr) of power storage appears to be comparable to batteries (38 whr costs $3 - or $75/kWhr for lithium batteries (which are not sustainable)). But lithium bats live 5 years or so - whereas PVC lives 400 years - so the gravity pond is a 100x better solution if we internalize lifetime design. Sure looks good on paper. Are these numbers sound?

**2019 addendum:** It gets more interesting with 3D printing. Each piece of pipe of 4", 10' long is $10, but if we 3D print these - then the cost of 4" PVC Pipe drops to 65 cents per 10 foot section (10 cents per lb from post-consumer waste plastic). So $100 per 24kWhrs of power. $5/kWhr cost is 10x better than batteries, and 1000x better over a lifetime.

If this works, we will consider this project for a future workshop in permaculture and open source technology, like the ones we're running now (http://bit.ly/1lHE2fw). If anyone can help us develop this project, please let me know.

**2022 Addendum** - if we do a 1 acre pond, 24 feet deep- then we have 16x the energy storage. The 24kW hrs turns into 384kWhr. This would be the scale required for a village enterprise.

### Option B

Take a little further north, 18ft of head instead of 30.

- 30 meter on each side pond, 2m deep - is 2000 cu m. Energy - MGH = 2M kg *10u*6u = 100MJ. That is 27 kWhr. Hydro is 90% efficient.[2]. Take 50% for our system. That is 12kWhr. could be good. Even if it's 6 kWhr - that is sufficient for an efficient house.

# Option C

- Housetop - 32 totes. 8800 gal. 40 cu m.
- Rise would be 20', almost 7m.
- Mgh=40,000*10*7=almost 3 MJ. Or 0.8 kwhr.

# Working Doc

## References

- Pumped Hydroelectric Storage, Chi-Jen Yang - File:Phs.pdf

## Turbine Sources

- Pelton Wheel only - [3]
- From Dan, look ethical and have good equipment - [4]
- Pelton turbine system - [5]
- Platypus Power - [6]
- Survey - http://www.zero.no/publikasjoner/small-scale-water-current-turbines-for-river-applications.pdf

## Contacts

Contacted Regrarians, Permies, TED Fellows on Facebook.

Hi Permies, I've been bouncing this pumped hydroelectric storage idea, which we are considering for a future workshop. This appears feasible at our site, with 30 feet of head, using two quarter acre ponds. I'm contacting http://www.canyonhydro.com/micro/microfaq.html#FAQ_HowMuchPwr to find out more about Pelton turbines - any ideas on other reputable Pelton turbine sources?

Calling the engineers in the audience - I just ran through some calculations on the feasibility of water pumping storage at Factor e Farm, our facility. The numbers look really good on paper. The drawing shows two quarter acre ponds - the contour lines are at 1 foot elevation intervals, so 30 foot drop between the ponds. The calculation yields 24kWhr of energy storage from this using proven microhydro technology - where the elevated pond serves as a reserve that can be pumped during daylight for gravity water storage. This is an open call for review of the calculations, see below. Explanation: Can we consider a storage hydro system that pumps during the day and generates electricity by night? Quick calculations: 1/4 acre pond, 6 foot deep. That is about 2000 cubic meters of water. Take another pond 10 m lower. The energy of water going from pond 1 to pond 2 (see drawing attached) is MgH = energy = [2000 cu m]x[1000kg/cu m]x[10 m/s^2]x[10 m] = 200 MJ 200 MJ = 200 MW for 1 second, or 200 kW for 1000 seconds, or 2 kW for 100,000 seconds - but assume 50% system efficiency (85% pumping, 85% generating, then 20% friction loss) THAT IS over 24 HOURS OF 1KW OF POWER!!!!!!!!!!!! Cost will be $1.5k in 4" pipe (about 1000 ft), $1k in power equipment, $10k in excavation + trenching for 2 ponds. If we have our own dozer, that will be $3k system cost. $3k for 24kWhr of power storage appears to beat batteries by a factor of 5-10 in cost. Sure looks good on paper. Are these numbers sound? If this works, we will consider this project for a future workshop in permaculture and open source technology, like the ones we're running now (http://bit.ly/1lHE2fw). If anyone can help us develop this project, please let me know.

## Other Types of Gravity Storage

- Concrete - [7]
- Concrete Energy Storage Calculations

## Links

- Alexander Slocum, MIT - ocean windmill storage - [8]

# Internal Links

- Pelton Wheel
- Flow battery - the cheapest form of chemical storage possible - $1/kwhr for materials, and $10/kwhr for balance of system

# External Links

- The Wikipedia Page on Pumped Hydroelectric Storage
- A Video by the Youtube Channel "Real Engineering" Titled "The Truth About Pumped Hydro" (It mainly mentions the issues of water use, and more importantly geographic availability)