HEST Technical Solutions Used for Design and Construction
of Stationary Energy Storage Facilities
I hope HEST will motivate
·
energy storage customers to engage in a competent discussion with concerned
parties regarding the opportunities and conditions for organizing a call for
proposals for the design and construction of a HEST-based energy storage
facility, including the R&D activities
·
EPC contractors to engage in a competent discussion with concerned
parties and potential customers regarding the opportunities and conditions for
implementing the HEST design and construction works, including the R&D
activities
Hereby I kindly invite to a systemic professional
dialogue those companies that have the ambitions, competencies and motivation
to possess an adequate industrial grade energy storage technology.
This document presents the brief information on the
HEST. With this information and my support, your line specialists will be able
to present the HEST to you as a simple and convincing solution. The principles
behind the HEST will be made clear, and you will learn about its main technical
solutions. You will receive trustworthy conclusions regarding the HEST design
and construction complexity. You will also be aware of the range of feasible
technical and economic parameters of HEST-based energy storage facilities. You
will understand the HEST technical conditions and design options, as well as
their variability in connection with the technical and economic parameters of
the construction project.
Learning about the HEST technical solutions, we will
go into some details and find justified answers to these two questions:
·
Will
the declared HEST parameters be feasibly achieved and confirmed by the design
project?
·
Can
the HEST-based energy storage facilities be designed and built right away?
Answering YES to the above questions will pave us the
way to negotiating the conditions for cooperation.
HEST comprises three key systems
plus a stock of working weights:
1. Main
energy accumulation system (gravitational solid-state accumulators or GSSA)
·
The
GSSA features a complex of vertical or inclined lifting vehicles that perform
shuttle-type displacement of solid working weights from the lower storage
horizon to the upper storage horizon. During the upward displacement, the
potential energy is being accumulated by the weights. Energy is being released
when the weights are moving downwards under the gravity force - through
transferring the kinetic energy of the moving weights to an electric generator.
·
The
GSSA is used to accumulate the energy retrieving it from the grid, store it
with no losses for as long as needed, and return the energy to the grid when
required.
2. Backup
power system (BPS)
·
The
BPS comprises battery systems of specified capacity (Li-Ion or capacitor-based
systems), electric current convertor and a control system.
·
The
BPS is used to ensure a quick response of the HEST facility to short-term
fluctuations of incoming and outgoing grid power. The BPS is also used to
consume short-term excessive power from the GSSA or compensate the short-term
power deficit for the GSSA electric drives, which rules out interruptions in
the GSSA working cycles and ensures the electric machinery functioning in the
nominal modes.
3. Automatic
Control System (ASC)
·
The
HEST ACS is a multi-level automatic control system that manages the HEST
performance in its entirety as an integrated technological controlled object.
The ACS provides for developing and executing algorithms to control all
electric drives, mechanisms and devices of the HEST facility.
·
The
ACS links and controls functional groups of equipment, safety and security
systems, maintains the technological parameters within the acceptable ranges,
protects the equipment from overloads and performs other functions.
4. Stock
of working weights
·
Each
GSSA lifting vehicle is equipped with a stock of working weights. The total
stock of working weights in a HEST facility determines its indicative energy
storage capacity in the GSSA.
The HEST grid connectivity designs, HEST electric
machines and devices power supply schemes, regular ACS functional algorithms
are developed in a standardized manner to comply with the technical
requirements and conditions of each specific HEST construction project. The
above elements are mentioned here but not described in detail.
All principal HEST technical
solutions, i.e. construction design, building elements, machines and
mechanisms, power supply systems, surveillance, control and automation systems,
are developed in accordance with the standard industrial design/development
requirements and procedures.
Below are the elements of the concept GSSA. Some details will be presented during substantive consultations.
Below are the elements of the concept GSSA. Some details will be presented during substantive consultations.
Fig. 2. Main
elements of a lifting vehicle and working weight transportation devices.
Fig. 3. Outline of interactions between HEST main systems and
selected BPS elements.
HEST Key Parameters and
Components
1. GSSA Performance Efficiency
Performance efficiency of the GSSA, in general, is in
line with the overall HEST efficiency, with a small (1-2%) correction for the
energy consumption by the auxiliary systems.
Parameter
|
Required Value
|
Feasible Value
|
|
GSSA Efficiency Ratio
|
70% and more
|
Up to 74%
|
For vertical GSSA designs
|
From 70%
|
For inclined GSSA designs
|
The GSSA efficiency
ratio characterizes the GSSA performance efficiency being a proportion of the amount
of energy retrieved from storage to the amount of energy used for the full
cycle of working weight displacement.
Energy consumption
for the full cycle of GSSA working weight displacement amounts to
·
energy
used for the work of the electric drive of the lifting vehicle that lifts the
working weight from the lower to the upper storage horizon – productive energy
inputs
·
energy
used for the work of machines and mechanisms that pick up the working weight
from storage place, transport it to the loading platform of the lifting
vehicle, unload the weight from the platform at the upper horizon, transport it
to storage place and mount it there, as well as for the same processes in
reverse order during the power generation phase of the cycle – logistical energy
inputs, which also include energy used to move idle (unloaded) loading platforms.
Fig. 4. GSSA energy inputs visualization.
Retrieved (generated) energy to
productive energy inputs ratio limit
For vertical
GSSA design, the retrieved energy exceeds 80% of the productive energy inputs.
For inclined
GSSA design, the retrieved energy exceeds 76% of the productive energy inputs.
The use of inclined weight transportation option increases the energy
consumption proportionately to the inclination angle: the bigger the angle, the
longer the working weight transportation distance compared to vertical
displacement. The performance efficiency requirements set the limit of the
maximum inclination angle for HEST design works.
Fig. 5. Outline of GSSA lifting vehicles in vertical and
inclined design.
The following solutions are used for achieving the
desired performance efficiency when designing GSSA.
The lifting vehicle is equipped with a multi-engine
drive (Fig. 6). The multi-engine drive is a gearless direct drive. The
multi-engine drive uses reversible asynchronous electric machines. The electric
machines work as electric engines during the weight lifting phase, and as
electric generators during the weight drop phase. The shafts of the electric
machines, through electric clutches, perform pre-defined configurations of
coaxial connection between the electric machines and the winch drum. The
electric machines connection configurations provide for the power multiplication.
Rotation of the winch drum enacts reeling of the cable attached to the loading
platform, and therefore moves the platform. The weight of the platform is
balanced by a counterweight that is also attached to the winch drum by a cable.
Fig. 6. Multi-engine drive of the
lifting vehicle and the electric machines connection configurations.
When designing the multi-engine drive of the lifting
vehicle, certain technical conditions must be complied with in order to ensure
maximum energy savings, i.e. ensuring the effective
use of reversible asynchronous
electric machines with confirmed efficiency ratio of 94-96%.
Technical requirements for the effective work of
reversible asynchronous electric machines
|
Conditions for the effective work of reversible
asynchronous electric machines envisaged by the HEST
|
Operation in
nominal modes
|
HEST BPS and ACS
ensure each GSSA drive cyclic operation without interruptions and with a
constant load. Electric machines work in nominal modes.
|
Minimum influence
of electric machines’ inertia
|
A multi-engine
system provides for using the electric machines with indicative inertia
parameters.
|
Minimum energy
losses in braking modes
|
Braking modes are
executed through increasing mechanical resistance when connecting additional
generation power. For the duration of braking, an additional electric machine
is connected to the configuration of the multi-engine drive’s electric
machines that are completing the generation phase. This additional machine
works in the generation mode and creates extra mechanical resistance used for
effective braking.
|
Selection of electric clutches, drives’ mounting
bearings and winch mechanism, guiding bearings of the loading platform is
performed with consideration of acceptable energy consumption and mechanical
resistance parameters. Design works should provide for selecting those hardware
parts that match the established energy consumption limit. The energy
consumption limit for the work and mechanical resistance of all lifting vehicle
elements, except for the multi-engine drive’s electric machines, must be under
4% of the productive energy inputs for the complete working weight displacement
cycle (weight lifting phase and weight dropping phase).
Logistical energy inputs limit
The HEST includes technical solutions that provide for
a fully automated process of shuttle displacement of working weights.
At this, the GSSA design is performed in compliance
with the logistical energy inputs limit. The logistical energy inputs limit for
the full cycle is up to 6% of the productive energy inputs used to perform this
cycle. The following pattern should be considered: the bigger the weight
vertical displacement, the less are relative logistical energy inputs. The
optimum recommended vertical displacement between the lower and upper storage
horizons is 200 m and more.
The following HEST technical solutions provide for
keeping the logistical energy inputs within the limit while ensuring the
optimum technical and economic parameters.
Purpose of HEST technical solutions
and their effect on lowering the logistical energy inputs:
Fig. 7. Variable rail inclination system.
The variable rail inclination system is used to
minimize the logistical energy inputs. Rails of the upper
and lower weight storage areas of each lifting vehicle are equipped with an
inclination angle alteration system.
Before a GSSA cycle phase change to energy
accumulation or release, the rail inclination changes. The inclination angle
changes in a way so that the rail-guided loaders with loaded weight always move
down the slope.
The rail inclination angle is changed by
electric-driven hydraulic lifting jacks. The jacks are installed under the
stiffening girders upon which the rails are mounted.
Fig. 8. Rail-guided loader.
The rail-guided loader is used to minimize the
logistical energy inputs when transporting the weights at the storage horizons.
The rail-guided loader also ensures a full automation of the processes of
weights mounting and dismounting to/from their storage places. The rail-guided
loader interacts with the loading platform for a fully automated
loading/unloading of the weights to/from the loading platform.
The rail-guided loader is positioned at the lower and
upper weight storage horizons of each lifting vehicle.
The inverted U frame of the loader has shelves
designed to carry respective weights. Each shelf is positioned at the height of
technological apertures of working weights that are stacked for storage. Each
shelf has a block of electrically-driven coupled hydraulic lifts (Fig. 8) that
work from opposite sides in the same horizon.
The rail-guided loader uplifts the working weights and
moves them from the storage place to the loading platform. The unloading from
the platform takes place in reverse order.
Fig.9. Loading platform.
The loading platform is used to minimize the
logistical energy inputs and ensure a fully automated process of working weight
loading, transportation by the lifting vehicle and unloading. Loading or
unloading of the working weights to/from the loading platform is carried out by
the rail-guided loader at the storage tier determined for each working weight.
The loading platform is kinematically connected by a
cargo cable with the winch drum of the transportation vehicle’s multi-engine
drive.
The loading platform is equipped with a working weight
transportation platform and mechanisms that provide for its sliding movement
and articulation with the matching elements of the rail-guided loader. The rail-guided
loader puts the working weight down onto the platform when loading or uplifts
it when unloading.
Fig. 10. Transportation
of an unloaded loading platform. Separate drive.
Fig. 11. Ratio: efficiency, power
generation and energy inputs.
2. HEST Response Time to
Short-term Load Fluctuations
Fig. 12. Power fluctuations chart.
а – range
of GSSA power stepped changes
b – range
of short-term power fluctuations in the external grid
The BPS is used to ensure quick HEST response to the short-term fluctuations of incoming and outgoing grid power in the specified range (b) (Fig. 12). The BPS also consumes short-term excess power from the GSSA or compensates for short-term power deficits for the GSSA electric drives (a). This is required to complete the full cycles of GSSA electromechanical machinery without interruptions, which provides for GSSA electric machines’ operation in nominal modes.
The BPS also delivers emergency power supply to the HEST
systems.
The BPS is composed of Li-Ion or capacitor-based
energy storage systems (BPS batteries), an AC to DC and DC to AC electric
current converter, and a BPS control system. To ensure guaranteed performance,
the total capacity of the BPS batteries will not exceed 10% of the total
deployed GSSA storage capacity.
Response time to power
fluctuations under 200 ms is a standard value for Li-Ion or capacitor-based
energy storage systems (used as BPS batteries).
3. Degree of Automation
The ACS performs the
following functions to control the load:
·
Continuous
calculation of short-term projections for incoming or outgoing load parameters
·
Analysis
of implementation of actual GSSA load vs planned, and respective selection of
the algorithm of GSSA units connection (number of lifting vehicles in use and
their working modes). The total planned GSSA power should match the projected
grid load parameters. Parameters corresponding to connected GSSA units when
executing the complete cycle are used for analyzing the planned load delivery.
Algorithms of GSSA delivered power alteration when completing cycles are used
as well.
·
Regulation
of GSSA performance in accordance with the calculated planned load parameters
Any difference
between the delivered GSSA power and the current grid power is covered by the
BPS. The recommended indicative HEST power distribution parameter is GSSA
93-95% min and BPS 5-7% max.
Fig. 13. Indicative
delivered power distribution parameter
4. Working Weights
Fig. 14. A
working weight.
Working weights are made of ferroconcrete structures
of specified geometry and weight. The hollows inside the structures are filled
with soil. The structures’ geometry envisages technological recesses that match
the corresponding elements of the rail-guided loader’s lifting devices.
5. Service Life
When designing a HEST facility, special attention
should be paid to the utilization of only the standardized, simple and reliable
solutions with confirmed performance parameters.
*Note: this ratio will improve with an increase in the ratio of storage capacity to installed power.
6. Additional Parameters
No.
|
HEST Storage Facility Construction
Budget Items
|
*Estimated
Share in Total Budget, %
|
Service
Life, Years
|
1
|
Set of
working weights
|
50
|
100+
|
2
|
Construction
elements
|
25
|
70-80
|
3
|
Electric
drives, moving parts, power equipment, control and automation systems
|
20
|
25
|
4
|
Backup power
system
|
4
|
10-15
|
5
|
Highly
wearable parts, lifting cables
|
1
|
1
|
6. Additional Parameters
The HEST solutions allow for power multiplication. To
do this, the number of working weights simultaneously lifted by one GSSA
lifting vehicle is multiplied, and respectively the backup electric machines of
the multi-engine drive are put into use. Each lifting vehicle has three
operational modes: standard, enhanced and extreme. These modes can be used in
various combinations to alter the energy accumulation power or energy release
power.
Fig. 15. Outline
of working weight multiplication.
7. Variability / Scalability
Fig. 16. HEST deployed power and stored energy capacity augmentation variability chart.
When required, HEST allows for increasing the
following parameters:
·
Deployed
power – through modernization of lifting vehicles’ multi-engine drives (d)
(Fig. 16) or adding up extra batteries (f)
·
Deployed
power and energy storage capacity – through constructing and linking up
additional GSSA units (e)
·
Energy
storage capacity – through increasing the number of working weights (g)
Fig 17. HEST in closed version. It is
used in climatic conditions with a high level of formation of snow cover or
where protection against sand is required.
Conclusion
I hope that after our
consultations on HEST we will have a common understanding and creed regarding
the HEST feasibility and applicability.
The prospects will inspire us by
their magnitude and accessibility, the risks will be clearly identified and
fully addressed.
We will negotiate the conditions
of cooperation having the practical experience of reaching mutual understanding
and an effective style of interaction.
