Hydraulic Rock Storage introduction nov15 v2 1

Hydraulic Rock Storage (HRS) –
an Efficient System for
Large-Scale Energy Storage
An Introduction
November 2015

2© Heindl Energy GmbH, all rights reserved
1. Executive Summary
2. Why Energy Storage?
3. Storage Demand and Market
4. Technical Concept
 Basic Physical Principle
 Construction
 Sealing
 Location
5. Business Models and Competition
6. Current Status and Next Steps
7. About us
Contents

What’s the idea? Hydraulic Rock Storage (HRS) can be
used to store power, in the scale of multi-GWh, for 8 to 14
hours – potentially more efficiently than Pumped Hydro
Storage. We believe that HRS will be a game-changing
solution for the world´s energy supply, as photovoltaic
(PV) and wind power become the cheapest source of
electricity and the demand for power continues to increase
rapidly. HRS offers reliable 24-hour supply of solar and
wind power at steady, predictable costs. Additionally it
may be a contribution to resilience power systems.
How does it work? A piston of rock with diameter >100 m
is excavated in the ground from its natural surrounding
rock. In times of excess power, water is pumped under the
piston. When additional power is needed (e.g. at night or
in times of little wind), water is released from beneath the
piston, allowing it to fall, and used to drive turbines.
Generators are then used to produce electricity, which is
fed into the power grid.
Why so efficient? With each doubling of the diameter,
storage capacity increases at a rate that is roughly
proportional to the fourth power of the diameter (D4) while
construction costs only increase at a rate that is roughly
proportional to the second power of the diameter (D2).
This fact, a result of the applicable laws of physics and
geometry, is of groundbreaking significance for the cost
efficiency of storage. We estimate construction costs of
approx. 130 USD/kWh of storage capacity, with a physical
round-trip efficiency of over 80%.
What other key advantages does it offer? Unlike Pumped
Hydro Storage, HRS does not require any elevation
difference. (Suitable geological conditions are required,
but these can be found in many regions around the world.)
HRS plants can be built using proven technologies from
mining and tunnel construction, and can be expected to
have a service life of 60 years or more. And no chemicals
or other hazardous substances are used during
construction and operation, with water and rock being the
key materials required.
What’s the business case? The most likely business case
(without any subsidies) is a combination of PV or wind
production and HRS, ensuring reliable electricity at a
constant cost for a long time. This represents an attractive
model for a YieldCo based on long term PPAs in a range
of 110-120 USD/MWh.
What next? After developing this concept for the past four
years, we are currently preparing a pilot project to prove
the concept. We are also searching for a suitable site for a
first commercial application.
What can you do? Please contact us to discuss possible
applications you might be interested in for your business.
Executive Summary

Why Energy Storage?
A Vision of Clean and Reliable Power Supply

The wealth and prosperity of mankind have depended for
centuries on the availability and use of stored energy
sources such as coal, oil and uranium.
But times are changing rapidly. While fossil fuels are now
recognized to be damaging to our climate, new technologies
enable unlimited solar energy to be used to produce
electricity, with low environmental impact and at affordable
costs.
We believe that the demand for energy storage will continue
to grow strongly in the decades to come – due, in particular,
to the following global megatrends in electricity supply:
 Solar energy will become the dominant source of power
supply for roughly 80% of the world’s population, with
wind power also featuring strongly in some regions.
 Global energy consumption will continue to increase,
due to the ongoing electrification of daily life (IT, mobility,
cooling, desalination, etc.) in developed economies and
the industrialization of emerging economies.
How Energy Storage will Change the Global Energy System

Our Mission: 24 h Sustainable Energy Supply
Heindl Energy´s mission is to transform
the world’s energy storage landscape,
paving the way towards a sustainable,
clean global power supply.
Hydraulic Rock Storage (HRS), the
company’s brainchild, turns PV energy
into reliable 24-hour power in an
economically and technically feasible way.
By solving the energy storage challenge
in this way, we aim to support the
development of reliable power supply
systems that are 100% based on
production from renewable sources.

Storage Demand and Market

Solar power will become the cheapest source of electricity in many regions of the world, …
reaching costs of between 3.3 and 5.4 ct/kWh in 2025.
In North America, costs for large scale solar photovoltaics will reach 3.2 to 8.3 ct/kWh in 2025.
…The wide cost range due to significant geographical differences within the region.”
Source: Agora Energiewende: Current and Future Cost of Photovoltaics, 2015
PV will soon be the Most Cost-Efficient Source of
Power in the World.

80% of the World’s Population Lives in Regions
with enough Solar Irradiance to Satisfy Energy Needs.
Many emerging economies, which show the highest growth rate in electricity demand, are located in
regions where solar insolation exceeds 4 kWh/m2 per day.
To become the major power source, PV has to be connected with large scale daily storage for 8-14 h
to provide 24 h supply.

Global Growth of Fluctuating Renewable Power
Blue curve: trend, when average growth of PV and wind between 2011-2014 will continue, red
curve: trend, when average growth since 1992 will continue. Installed power on log scale.
Source: Prof. Heindl

Estimating future global storage demand:
 To satisfy a 24-hour demand, a 1,000 MW PV
farm needs 300 MW of storage power with a
storage capacity of 2 GWh. Considering an
estimated future global PV production of 15,000
GW (should the world‘s electricity needs be
fully met by solar), this would require a global
storage capacity of 30,000 GWh.
 Elon Musk estimates a global storage demand
of even 90,000 GWh in case of a complete
supply of all energy demand (incl. e-mobility) by
PV.
The Massachusetts Institute of Technology (MIT)
states, in a 2015 report on the future of solar
energy: The larger the quantity of added energy
storage capability, the higher the revenues
generated by PV plants and therefore the higher
the profitability of PV investments at any level.
Global Storage Demand

© Heindl Energy GmbH, all rights reserved 12
An important business model for
HRS: Excess power from PV
plants is stored (purchased) during
the day and discharged (sold) at
night.
Utility companies and PV farm
operators must provide a reliable
power supply, at all times of day or
night, and thus need bulk storage.
Grid operators need bulk storage
to catch the ramping loads
occurring during sunrise and
sunset periods.
The Business Case of Bulk Energy Storage

Technical Concept

Technical Concept: Harnessing the Potential of
Gravity
How it works: A rock
piston, which has been
cut from the bedrock in
a selected location, is
lifted using water
pressure (by pumping
water into the space
beneath it), and when
electric power is
needed, pressurized
water is released and
routed to turbines.
150 m = 1 GWh
150m
water
reservoir
Water for
hydraulic
lifting
Large scale
PV farms
Pump and turbine
piston of rock
rolling sealing
Access
tunnel
Mass ~ r³
Height ~ r
Cost of construction ~ r²
Thus: Cost per kWh ~ r²/r4, or 1/r²
Energy storage capacity
E ~ 2 π g ρ * r4
EHRS = (2*ρR -3/2*ρW )* π*g*r4
(where ρR and ρW are densities
of rock and water respectively)
The economical benefit: Storage capacity, which is
roughly proportional to the piston’s mass (~ r³) and the
height lifted (~ r), increases with the fourth power of
the piston’s radius. Construction costs, however, only
increase with the square of the radius. This means that
construction costs increase much more slowly than
storage capacity as radius increases.
1
2
3
4

Construction
 The rock piston is separated from the
surrounding bedrock, both underneath
and around its circumference, using rock
cutting machines.
 All exposed surfaces are sealed with
geomembranes to protect against
environmental impacts and prevent loss
of water.
 The gap between the piston and the
surrounding cylinder is sealed by a
flexible membrane.
 Pumps, turbines, generators, etc. are
fitted as required.
 Planning: 2 - 3 years
 Construction: 3 - 4 years
 Total: 5 - 7 years
 Operation life:> 60 years

Excavation of the Piston
Using established mining and tunneling technology
To excavate the piston (i.e. to separate it from the surrounding bedrock), a spiral
tunnel (approx. 4 m high x 5 m wide), or alternatively a vertical shaft, providing
access to the piston‘s base level, is created by blasting. Working level tunnels are
created at various levels.
Source:
Access shaft
Working level tunnels
Base working level
Base tunnel
Spiral access tunnel
(Alternatively: vertical shaft)
Connection tunnels
Connection tunnel

Excavation of Base of Piston I
1)
2)
3)
The excavation of the base
is a challenge which can be
mastered using mining
technology:
1) Drill holes and insert
explosives
2) Blast rock and remove
debris
3) Stabilize the base of the
piston with rock anchors

Excavation of Base of Piston II
Approved methods from underground mining
In order to ensure
stability, rock bolts will
probably have to be
installed in the roof
immediately after
excavation in each area.
The separation of the piston base from the
underlying rock is initially based on the well-
established “bord and pillar” method of
mining/extraction, with a series of parallel
tunnels (approx. 4m high and 5m wide, 5 m
apart) excavated as a first step. The
remaining 5m-wide walls of rock between the
tunnels initially support the weight of the
piston above. Reinforced concrete pillars, of
approx. 5m diameter, are then constructed at
regular intervals along each tunnel. With
these pillars in place, the remaining rock can
be excavated, at which point the weight of
the piston transfers to the new concrete
pillars. The concrete pillars, which are
securely anchored into the rock above and
below, are split at mid-height, with a stainless
steel sliding sheet inserted between the
upper and lower parts, enabling the piston to
move transversely and avoiding the build-up
of destructive constraint forces. The space
between the pillars will remain free, allowing
water to be pumped under the piston to lift it
and facilitating future access for maintenance
etc.

Assessment of Geophysical Stability
Effects of deformation of the rock cylinder and piston
Source:
Deformation of cylinder and piston at a diameter of 500 m (corresponding to a capacity of 124 GWh!).
Deformation of cylinder:
Max 3.5 cm
Deformation of piston:
Max 3.2 cm
3.5 cm
deformation

The Sealing Challenge: The “Rolling Membrane”
 Typical pressure at sealing membrane: 40 bar
 Forces absorbed by steel cables
 Flexibility accommodates piston movements
 Self-centering
 Production similar to conveyor belts
 Full access for maintenance
PistonCylinder

Capacity [GWh] 0.2 1 2.1 3.2 8 124
Radius, Lift [m] 50 75 90 100 125 250
Diameter [m] 100 150 180 200 252 500
Volume of water
[1000 m3]
392 1,325 2,290 3,141 6,284 49,087
Pressure [bar] 21 31 37 41 52 103
Size Variants at a Glance
HRS can be built with various diameters. At a diameter of
about 250 m, the storage capacity of a typical large pumped
hydro storage plant is already achieved.
These pressures are not very high; they are generally in the same range than in
pumped hydro stations.
The need for water is also far lower than in pumped hydro stations.

Location Requirements

Location Requirements
Geology:
• Compact homogeneous rock with little
tendency to fracture. The more compact
the rock, the lower the cost of
construction.
• Young’s modulus (E) of at least 10,000
MPa
• No mountain or elevation difference
required!
Hydrology:
• Proximity to a water supply and drainage,
but large-scale upper and lower basins
(as required by pumped hydro storage)
not required. A single, smaller reservoir is
sufficient.

Advantages:
• Good rock quality generally available
at bottom of quarry
• Geological conditions largely known
• Already used for surface mining
• Largely out of sight since below the
surrounding ground level
• Water often present in old mines
• Good infrastructure, grid connection
Possible Locations I
Quarries
Illustrative, not a real project

Large PV power plants
Possible Locations II

Hydraulic Rock Storage: The case of Las Vegas
1 GW of PV (300 MW finished, 700 in planning), with an 8 GWh HRS plant
HRS plant
(real scale!)
Large PV power plants
Possible Locations III

HRS Business Models and Competition

Costs of Constructing the Piston and Cylinder
0 €/kWh
60 €/kWh
120 €/kWh
180 €/kWh
240 €/kWh
,,0
100,000,000
200,000,000
300,000,000
400,000,000
50 m 75 m 100 m 125 m Radius
Cost in mn USD
Cost per unit of
storage capacity
270 USD/kWh
66 USD/kWh
0 USD/kWh
132 USD/kWh
198 USD/kWh
440
330
220
110
0
8 GWh1 GWh Capacity
Source:
(excluding turbines, pumps, generators, grid connection etc.)
We show the costs of constructing the piston and cylinder separately from the total costs (following
slide) due to make the figures more comparable to other technologies. Many number used in the debate
about costs of storage do not include total costs.

Total Costs of Construction
200MWh ; 595$/kWh
1.000MWh; 278$/kWh
2.100MWh; 203$/kWh
3.200MWh; 172$/kWh
8.000MWh; 124$/kWh
16.000MWh;
100$/kWh
$/kWh
100 $/kWh
200 $/kWh
300 $/kWh
400 $/kWh
500 $/kWh
600 $/kWh
700 $/kWh
100 MWh 1.000 MWh 10.000 MWh 100.000 MWh
USD/kWhstoragecapacity
MWh storage capacity (log)
Larger radius leads to a
very cost efficient storage
falling below USD 100
(EUR 91) / kWh capacity
when 16 GWh (= 160 m
radius) are equipped with
1’000 MW turbines (= 16
hours).

HRS Business Models
Each of these models can be combined and varied with respect to:
• the number of cycles per year
• the design and capacity of the required pump and turbine equipment
HRS strives for profitability without reliance on subsidies.
The PPA model is the most promising one at present, being likely to be
profitable already in sunny regions.
PPA (Power Purchase
Agreement):
Combine PV or wind
energy production with
HRS, delivering 24-hour
electricity at a fixed price
(120-140 USD/MWh) for
20 years or more. Could
ideally be run as a
YieldCo.
Arbitrage model:
Charge storage at low
prices, sell energy at
higher prices.
Providing system
services:
As a source of flexibility
and security of supply.
Ancillary services, black-
out prevention etc.
Energy-intensive
industries:
Reducing peak loads.

Preferred Markets and Target Regions for HRS
1. For use as daily storage in
regions with high PV energy
production. PPA for “production plus
storage” at a reliable long-term
price.
2. In regions with particularly high
demand for supply security and
ancillary services, and where
• Electricity demand is growing
significantly
• Steep ramping occurs
• PV and wind energy generation
is expanding
• Security of supply is considered
to have particular value for the
national/regional economy
• Pumped hydro storage is not
possible due to the lack of
height difference in the local
terrain
The so-called “duck curve”:
The increasing ability of PV in the years to come
to directly meet daytime energy needs will result
in increasingly steep ramping towards evening.
This causes demand for stored energy.
Source:https://energyathaas.wordpress.com/2013/07/29/whats-the-point-of-an-
electricity-storage-mandate/

Current Status and Next Steps
About us

Current Status and Next Steps
What has been completed:
• Patents granted for the system
• Patents applied for sealing
• Feasibility studies with respect to geology, geomechanics and construction
• Development of sealing concepts
• Cost estimates
• Financial model incl. revenue scenarios
• A suitable site for a pilot project has been found. Design, preplanning and calculation
has been completed.
• Technology Partners for sealing and engineering.
What is ongoing:
• Application for approval for construction of the pilot project
• Search for investors and public funding to realize the pilot project
• Presentation of the concept to the global energy industry and science community
• Search for sites for commercial application of HRS
What are the next steps (2016 and beyond):
• Commencement of planning for pilot project
• Estimated time for approval and planning: 1 year
• Estimated time of construction: 2-3 years
• First commercial applications commissioned in 2024

Heindl Energy‘s purpose is to develop and,
together with its partners and investors,
realize the Hydraulic Rock Storage as a
beneficial and profitable means of energy
storage. The company is currently planning a
pilot project to prove the concept‘s viability,
and already holds all required patents.
Heindl Energy was founded 2013 and is
based in Stuttgart, Germany.
The company’s founder and main
shareholder is Professor Eduard Heindl, and
the main investor is HTG Ventures AG,
Switzerland.
Further information:
www.heindl-energy.com
About us
HeindlEnergyGmbH, Stuttgart, Germany
Prof. Dr. Eduard Heindl,
Managing Partner
Robert Werner,
Executive Director
Prof. Dr. Simone
Walker-Hertkorn,
Head of Geology
Dr. Karin Widmayer,
Project Management
Management Team:

 Profitability:
 Economy: Construction cost per unit of storage capacity decreases
rapidly with increasing radius (proportional to 1/r²)
 Particularly promising business cases in combination with PV (without
subsidies)
 Efficiency: High, at 80% (comparable with pumped hydro storage)
 No elevation difference needed (unlike pumped hydro storage)
 Construction technologies have long been used (e.g. in mining and
tunneling industries)
 Low running costs
 Sustainability:
 low raw material requirement, “just rock and water”
 Low land footprint
 Requires less water than pumped hydro storage (~ 1/4)
 Long service life of over 60 years
 Reliability:
 Security of supply: buffers fluctuating power on an Gigawatthour-scale
 System services: ancillary services, black start capability, rotating masses
 Easy operation
Advantages of Hydraulic Rock Storage

Thank you for your attention.
Heindl Energy GmbH
Meitnerstrasse 9
70563 Stuttgart
Germany
Tel.: +49 711 6569689-0
info@heindl-energy.com
www.heindl-energy.com

Hydraulic Rock Storage introduction nov15 v2 1

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