Off-grid, grid support, back-up and RE applications

BATTERIES SOLAR PV WIND GENSET GRID

ContainerizedUniversal Battery

Discover® Energy CUB is designed to endure the most extreme environments, and provide robust power and energy storage for off-grid, grid support, battery back up and renewable energy applications.

The Containerized Universal Battery (CUB) combines the best energy storage, power conversion and control systems into a standard 10 foot shipping container. Our CloudEnergy NetworkTM architecture allows for any number of Energy Cells to be connected together, to support a wide range of power and energy storage requirements.

Overview

Benefits & Features

Off-grid, grid support, back-up and renewable energy applications

•Cloud Energy NetworkTM architecture allows containers to be connected together and operate as one

•On board battery management system•Remote diagnostics, monitoring, controls, and data logging•Automated generator controls•Modular architecture, easy to repair and service•Grid-tie capable for selling excess energy back to grid

• Power back-up for grid interruption • Diesel off-set• Off-grid energy storage• Reduce grid consumption • Community electrification

Applications

Architecture & Interface

AC Utility Grid

PVAC Coupled PV Inverter

AC Load Breaker

Panel

Commercial | Industrial load

Remote Monitoring

• Enables graphic display of CUB status.

• Tools for data analytic.

Generator

• Can be installed within existing grid tie solar installations using an AC Coupled Architecture.

• Converts sunlight into electricity.

PV

• Solar PV arrays can be connected directly in a DC coupled architecture.

CLOUD ENERGY NETWORKTM ARCHITECTURE allows you to combine energy cells for more power and energy

20 kW*180 kWhr**

40 kW*360 kWhr**

80 kW*720 kWhr**

* AC Continuous Power Capability** DC Energy Storage Capacity

AC In

AC Out

DC

Communications

Automatic start and stop of generator

OR

InvertersDC Solar Charge

ControllersBatteries

The CUB is designed to endure the most extreme environments, and provide robust power and energy storage for off grid, grid support, battery back up and renewable energy applications. The Containerized Universal Battery (CUB) combines the best energy storage, power conversion and control systems into a standard 10 foot shipping container. Our CloudEnergy NetworkTM architecture allows for any number of Energy Cells to be connected together, to support a wide range of power and energy storage requirements.

www.discover-energy.com

DISCOVER ENERGY

PROJECT APPLICATIONS

OFF-GRID SMART GENERATOR CONVERSION• Generator is prime power source• The CUB allows generators to run less

frequently and at optimal power, resulting in fuel savings and improved cycle life duration

GRID SERVICES AND BACKUP POWER-TELECOM• Grid services including energy

arbitrage, VAR support, renewable support and frequency regulation

• Backup power with and without grid-tied solar

OFF-GRID PRIME SMART POWER• Prime power source is PV, excess

power is stored in batteries• Generator acts as backup• Up to 75% in fuel savings

DEC-10 v1.0 SPECIFICATIONS

Exterior Dimensions • Length 10 ft x Width 8 ft x Height 8 ft 6 inInterior Climate Controls • Fully automated heating, ventilation, and air conditioning

• Fully insulated interiorPower I/O Voltage • Compatible with many worldwide single and three phase systemsContinuous Power Ratings • 4.8 to 40.8 kW depending on configuration

Surge Power Ratings (60 sec) • 9.0 to 72 kW depending on configuration

Available Batteries • Tubular Flooded or Tubular Gel, LithiumMax Energy Storage • 180 kWhr at 20 hour rate using Tubular Flooded Cells

• 360 kWhr at 1 hour rate using LithiumBattery Cycle Life • Tubular Lead Acid up to 3000 cycles at 50% DOD 20° C

• Lithium more than 7000 cycles at 0.5C rate, 100% DOD 25° CMax Dc Coupled Solar • 38.4 kWp at 600 VDC maxAmbient Operating Temperatures • -50° C to +50° CFeatures • Cloud Energy NetworkTM architecture allows containers to be connected

together and operate as one

• On board battery management system

• Remote diagnostics, monitoring, controls, and data logging

• Connectivity and customizable controls over Modbus RS485

• Automated generator controls

• Generator and grid support for extra power

• Modular architecture, easy to repair and service

• Grid-tie capable for selling excess energy back to grid

• AC-Coupled solar architecture compatible

• Built in safety subsystems including H2 detectors, smoke and flame detectors,

optional fire suppression systems

CLOUD ENERGY NETWORKTM ARCHITECTURE allows you to combine energy cells for more power and energy

20 kW*180 kWhr**

40 kW*360 kWhr**

80 kW*720 kWhr**

* AC Continuous Power Capability** DC Energy Storage Capacity

www.discover-energy.com

10 ft

8.6 ft

8 ft

energycub.com

Discover Energy CUB1 Energy Cell Executive Summary

Why CUB?

When generating electricity it is immediately consumed as soon as it is produced. Because the generator needs to operate at variable output levels it will not always be able to run within its most efficient range.

In remote commercial operations and living communities, where there is no access to the grid and the main source of electricity is a fuel based generator, the effects of immediate consumption are ever more prevalent. Energy costs are directly proportional to the cost of delivering, storing, and burning fuels. However, when critical infrastructure relies on generators, efficiency isn’t necessarily top of mind. Stored energy shifts the paradigm from immediate consumption to stored energy.

By storing energy, a generator does not need to operate 24/7 at variable output levels and can instead operate for fewer hours at much higher efficiencies. Similarly, with renewable sources like solar PV, a solar array can output maximum power where excess energy is stored during the day and consumed in the evenings.

The Containerized Universal Battery (CUB) platform allows for the integration of energy storage into any remote grid, microgrid, or behind the meter application, and allows for the control of multiple power flows, increasing overall efficiency and reducing energy costs.

What is the CUB?

The CUB Energy Cell is a containerized energy storage system which integrates energy storage from Discover Energy and power conversion electronics from Schneider

Electric into a standard shipping container format. The Energy Cell is a completely self-contained with its own HVAC system. It can be deployed in any location and integrate multiple sources of generation such as generators, the grid, solar PV, and wind turbines.

The Energy Cell manages the flow of power from sources of electricity, energy storage, and loads. This allows all connected sources of generation to operate more efficiently. Diesel generators will be able to run at a higher efficiency and reduce their overall run time, resulting in longer operating life. Renewable sources, such as solar PV, will be allowed to operate at full power where any excess power is stored. The CUB is a highly modular and flexible platform that can be adapted to small and large applications.

A truly turnkey system, minimal on-site installation is required. With its walk-in, walk-out design, installation, commissioning, and maintenance are simplified while still providing security from unauthorized access.

Where can the CUB be used?

Any facility or site that operates off-grid and is relying on a prime generator is the ideal application for CUB. In a Smart Hybrid Generator configuration, similar to a hybrid automobile, the CUB will utilize the generator as a battery charger, allowing it to operate only on demand and at a much higher efficiency, up to 15-30% higher, depending on the size of the generator and loads. All energy stored in the batteries will be distributed to the loads.

Taking it a step further, Prime PV adds a second source of generation, namely Solar PV, to the system. The solar array has been sized to generate the majority of the application’s needs. Any excess power generated by the solar array is stored in the batteries and redistributed to loads when the sun goes down. The generator is used as a backup power source, further reducing runtime, and could reduce overall fuel consumption by more than 75% depending on location and size of renewable resource. Primary applications include remote work camps, communities, telecom installations, and agricultural operations.

Introduction

When generating electricity, whether from a nuclear power plant, solar array, or diesel generator, it is always consumed immediately. The electrical loads dictate the amount of electricity that needs to be generated. With most traditional forms of generating electricity their output is adjusted automatically to follow the load demand.

Different forms of generation can be more or less flexible when it comes to being able to adjust the flow of power to follow demand. Sources of generation that are less flexible, such as a nuclear power plant, are able to produce massive amounts of energy at a very high efficiency. However, it is only able to vary its output very slowly.

Renewable sources, such as solar PV are completely inflexible and therefore cannot follow variations in load. Diesel generators are very flexible in terms of their ability to meet fluctuating load demand, but their conversion efficiency is relatively low, driving its operational cost higher.

For remote off-grid applications, flexibility in following load demand is of the highest importance, followed by fuel availability and operating cost. Diesel Generators have been the traditional choice and are able to meet the majority of these requirements except for operating costs. The CUB offers an alternate choice and is able to meet all the requirements for off-grid applications.

Generator Operations

In a remote off-grid environment, where there is no access to the grid, diesel generators have been the traditional choice as a primary power source. Although a fairly reliable and flexible choice, the operating costs are fairly significant and volatile due to the dependence on diesel fuel. Although diesel fuel accounts for the majority of the overall operating cost many other factors need to be taken into consideration.

Diesel generators convert liquid diesel fuel into electricity, heat, and pollutants. On average, a diesel generator can convert 1 litre of diesel fuel into 3 kWhr of electricity. In addition to the electricity, 7 kWhr of heat and 2.7g of greenhouse gases are emitted. Generator operating efficiency is directly related to the load demand placed on the generator.

From Figure 2 it can be understood that operating a generator at its maximum power output will result in the best fuel efficiency. The size of a diesel generator is selected based upon the anticipated peak loads that could occur at a facility – but these peak loads may only occur for a few minutes every day.

For the remainder of the day, the generator may only be operating at 30% of its total power capability, resulting in a significant decrease in fuel efficiency by as much as 18% or more. In order to operate a generator at its peak efficiency, it must be operating close to its maximum power capability with very little variation in load output.

In addition, generators may also have a minimum loading factor. When the generator operates at a load less than the minimum load factor, the generator must consume a certain amount of fuel to continue operating, no matter the load. Therefore, if the generator is operating at 10% of its total capability, it will still consume the same fuel as if it was operating at 25%. Generators operate at their lowest efficiency at low load factors.

Generator Operating Costs

There are many factors that affect the overall operating cost of a diesel generator. These costs can include diesel fuel, fuel delivery, fuel storage, generator maintenance, and generator replacement. Diesel fuel is the largest proportion of the overall cost of generator operation.

Figure 2: Diesel Generator Conversion Efficiency

Power Output (%)

Fuel

Effi

cien

cy (k

Whr

/L) 4

3.5

3

2.5

2

0 25 50 75 100

Figure 1: Load following flexibility

With the volatile nature of fuel cost, the relationship between fuel cost and electricity cost needs to be understood. Although quite obvious, as the price of fuel increases, so does the cost of electricity. But, it is important to understand that by operating the generator at a higher efficiency, the overall cost of electricity will decrease.

Delivery costs for fuel can be significant, especially the more remote the location and can sometimes approach the actual cost of the fuel. This must also be included in any total fuel costs.

Generator Environmental Pollution

Burning diesel fuel to produce electricity also produces harmful environmental impacts. Pollutants produced include carbon dioxide (greenhouse gas), carbon monoxide (poisonous), nitrogen oxides (acid rain), hydro carbons (unburnt gas, major greenhouse gas), and particulate matter (major health effects). The only way to reduce these pollutants is to invest in highly complex and expensive emissions systems or increase operating efficiencies.

There is also the possibility of fuel spillage or leakage during transportation or storage, which could have detrimental effects on the local environment.

Lastly, noise pollution is a major factor. If located close to a community 24 hour operation can significantly reduce the standard of living.

Renewables in an Off-Grid Environment

The majority of renewable energy installations, such as solar or wind, are grid connected. The primary goal of a wind or solar farm is to maximize revenue

generation. Usually there is little feedback to the solar or wind farm operator as to what the grid actually needs. Therefore, these farms will attempt to maximize their output at all times.

With fluctuating weather patterns and the day/night cycle, grid operators plan for variations in renewable energy output and utilize complex control algorithms to balance loads and generation output. This is all in an effort to meet the load demand immediately.

One of the key factors in a stable grid is to have a large enough mix of flexible and inflexible sources of generation. For example, a more flexible source of generation, such as a gas turbine generator, can be used to offset variation in output from renewable sources. This arrangement will maximize the output of the renewable source and allow the system to meet variable load demand.

In an off-grid environment, it would be impossible to operate any facility with renewables alone. The nature of needing to have instantaneous load response and the relative unpredictability of renewable availability would make for a very unreliable source of electricity.

In order for renewable sources of electricity to operate within a load following environment, the energy from renewable sources must be stored and released on demand. Energy storage, such as batteries, allow for this storage. If the major loads in a facility are in the evenings, while a solar resource only produces (energy) during the day, batteries can store the energy produced from the solar resource, and supply that load in the evening.

In order to produce usable electricity, batteries must be accompanied by a power conversion device like a battery based inverter. These inverters manage

Figure 3: Diesel Generator Conversion Efficiency$/L Diesel

$/kW

hr E

lect

ricity

$ $1.00 $2.00 $3.00$

$0.10$0.20$0.30$0.40$0.50$0.60$0.70$0.80$0.90$1.00

Highest Efficiency

Lowest Efficiency

Figure 4: Example Load Profile with Solar ProfileTime of Day

Load

(kW

)

4:00 8:00

20406080

100120140160

12:00 16:00 20:00 0:000:000

Load Profile

the power flow between the sources of generation (generator, solar, wind, etc.), the energy storage device (batteries), and the loads, and distribute power as needed. They convert DC sources from batteries or solar panels to AC power to supply loads. It can also convert bidirectionally, converting an AC source from the generator to charge the DC battery bank.

What is the CUB?

The Containerized Universal Battery (CUB) Energy Cell is a containerized energy storage system which integrates energy storage and power conversion electronics into a standard shipping container format.

Completely self-contained with its own HVAC system, the Energy Cell can be deployed into any location, integrate multiple sources of generation like generators, the grid, solar PV, and wind, and manage the flow of power to either storing energy or distributing power to loads. This will allow all connected sources of generation to operate more efficiently. For diesel generators, it will allow them to run at higher efficiency and reduce run time. For renewable sources such as solar PV, it will allow them to operate at full power, allowing any excess power to be stored.

The Energy Cell is a flexible platform, which allows for any combination of power and storage to meet the technical requirements of a broad range of applications. Energy is stored in batteries which have been selected to minimize the overall life cycle cost of the system. Power conversion electronics are manufactured by Schneider Electric, a worldwide leader in the design and manufacturing of electrical distribution and renewable energy products.

Bringing together all these components into a containerized system simplifies transportation

logistics, reduces installation costs, and eliminates on-site installation risks. The CUB is designed to allow for simplified diagnostics, can be easily serviced, and integrates multiple redundant systems.

Energy Storage

The CUB is able to accept a wide range of energy storage options, but the two main options available are tubular lead acid and lithium batteries. Both of these are excellent options and have their own strengths and weaknesses. No matter which battery bank is used, the nominal DC voltage is 48 VDC, which is classified as low voltage DC. The low voltage architecture does not require specialized safety training or equipment, simplifying service and maintenance.

Tubular Lead Acid Batteries

Tubular lead acid batteries utilize a unique positive plate in order to significantly improve cycle and design life relative to typical flat plate designs. The use of tubular positive plates, combined with sliding pole technology, allow these batteries to achieve a 20 year design life and excellent cycling capability (3000 cycles at 50% DOD @ 20° C). Tubular lead acid batteries come either in flooded electrolyte models that utilize transparent SAN containers to allow for easy monitoring of electrolyte levels or GEL electrolyte maintenance free models with fully sealed ABS containers.

Tubular Positive Plate: Typical flat plate lead acid construction utilizes grid plates with pasted active material. When cycling the active material grows and shrinks and can shed active material, reducing the capacity of the cell. In a tubular plate design, instead of using a grid, a comb-shaped current collector is used where each spine extends along the height of the battery. Each spine is encapsulated by woven polyester tubes and are arranged in gauntlets which holds the active material against the spine.

Figure 5: Example of Grid Connected Energy Storage and Power Conversion System

Grid-tie Backup with DC-Coupled PV

Figure 6: Tubular Flooded and Gel Batteries

Figure 7: 6.9 kWhr 48 VDC Advanced Energy System

During charge and discharge, the volume of the active material grows and shrinks. The polyester tube expands and contracts elastically, holding the active material together and in even contact with the spine. This reduces mass shedding and spine corrosion, significantly improving cycle and design life.

Sliding Poles: Over the life of the battery, the positive plate will grow in size at a rate of approximately 0.5 mm per year. With no sliding pole, eventually the positive pole will push through the cover, resulting in cover cracks and electrolyte leakage. The sliding pole design will allow for total positive plate growth of 15 mm allowing for an estimated total design life of 20 years. The sliding pole is fully sealed allowing for pole growth and maintaining a tight seal.

Lithium Advanced Energy Systems

Discover Energy’s Advanced Energy Systems utilize next generation lithium iron phosphate batteries, allowing for unprecedented cycle life, along with significantly lower volume and mass. The Advanced Energy Systems come prepackaged in 6.9 kWhr, 48 VDC blocks, fully enclosed and protected in its own enclosure.

Each system includes a full battery management system (BMS) which monitors the battery continuously and ensures that the battery continues to operate efficiently and safely. The BMS also includes its own integrated solid state contactor allowing the system to protect itself in the case of any unsafe operation.

Lithium batteries allow for significant improvements in battery performance, both electrically and mechanically, but come at an increased cost relative to any lead acid battery. The Advanced

Energy Systems include specialized controls and communications with the power electronics in order to operate at an optimal level.

Battery Cycle Life

When implementing an energy storage system into an off-grid application, one of the most important performance metrics is battery cycle life. As batteries are utilized, battery materials slowly degrade as evidenced by decreased battery capacity and increased internal resistance. The number of cycles that a battery can delivery prior to being considered at end of life is called cycle life. However, cycle life has many conditions that must be understood.

Depth of Discharge: Battery capacity is usually expressed in terms of the numbers of amps that can be extracted from the battery over a certain period of time. If a battery is said to have 500 Ahr of capacity, that could mean that the battery could delivery 500 A for 1 hour or 250 A for 2 hours, etc.

Depth of discharge (DOD) is the percentage of the total capacity of the battery that is utilized during discharge. Using that same 500 Ahr capacity battery, if the battery was discharge at 250 A for 1 hour, the battery is under a depth of discharge of 50%.

DOD is similar to State of Charge (SOC). While DOD counts up from a fully charged battery, SOC counts up from a fully discharged battery. For example, 25% DOD means that 25% of the total Ahr of the battery have been discharged. Equivalently, 75% SOC means that 75% of the remaining capacity of the battery is available.

DOD is an important factor related to usable energy. Lead acid battery cycle life is highly dependent on DOD, where the deeper the DOD, the lower the overall cycle life. Operating lead acid batteries at high DOD

Figure 8: DOD and Temperature Relationship with Cycle Life for Tubular Batteries

Num

ber o

f Cyc

les

0%0

DOD %10% 20% 30% 40% 50% 60% 70% 80%

1000200030004000

5000

6000

70008000

Tubular Gel RE Series Cells

Expected Number of Cycles vs DOD

20°C/68°F25°C/77°F30°C/86°F35°C/95°F40°C/104°F45°C/113°F

tends to increase stresses on the positive plates, resulting in increased degradation and lower cycle life. For frequent cycling applications, a 50% DOD limitation is recommended when using lead acid batteries in order to maximize cycle life. This means that the usable energy in a lead acid battery when utilized in a frequent cycle battery should be restricted to 50% of its overall capacity.

Lithium batteries do not have the same dependence on cycle life and will provide even performance no matter what DOD the batteries are cycled to. For example, when using lead acid batteries in a frequent cycling application, where DOD is limited to 50%, if 100 Ahr of storage is required, 200 Ahr of lead acid batteries would be recommended. Since Lithium battery cycle life is not affected by DOD, only 100 Ahr of Lithium batteries are needed.

Nevertheless it is recommended when sizing systems in an off-grid environment that some reserve capacity be built into the battery bank in order to maintain operation in extreme circumstances.

Discharge Rate and Duration: In most applications where batteries are installed, the battery will be discharged at various rates and will rarely be discharged at one constant rate over its entire life. A discharge rate for a battery is usually expressed in terms of the number of amps being discharged. The duration of that discharge is the length of time that the battery is discharged until it is completely discharged or empty.

When discharging a battery a load is applied to a battery that draws current from it. This load reduces the potential of the battery decreasing the voltage. If more load is applied the voltage will decrease more and at a faster rate.

All batteries have a low voltage cutoff point at which point the battery can no longer be discharged safely. If this cutoff voltage is reached earlier due to a higher rate of discharge, then the delivered energy will be less than if the battery was discharged at a lower rate. This is an example of Pukert’s Law, which describes that as the discharge rate increases the battery’s available capacity decreases.

When a lead acid battery capacity is published, it is usually listed in Ahr. The Ahr rating is associated with a duration with published figures usually utilizing the 20 hour rate. Therefore, if a battery is rated at 100 Ahr at the 20 hour rate, it is able to deliver 5 Amps for 20 hours until it is completely discharged. That same battery, if

it were discharged at a higher rate of 50 Amps, would only be able to deliver 50 Amps for 1 hour until it was completely discharged. If it were rated at the 1 hour rate, it would actually be a 50 Ahr battery. Lead acid battery capacity ratings are usually rated in duration ranges from 1 hour to 240 hours.

It is important to understand that since the rate of discharge has a significant impact on the available capacity of a lead acid battery, it will also have a effect on the cycle life of the battery. For a given application, if the average discharge rate was estimated to be 50 Amps, but instead turned out to be 75 Amps, this would affect the overall capacity of the battery bank. This in turn will affect the overall DOD of the battery, resulting in an increased DOD that will decrease the overall cycle life performance of the battery.

Lithium battery systems are on a completely different performance scale when it comes to discharge rates and durations where typical durations are in the range of 10 minutes to 2 hours. Any duration above 2 hours and the available capacity is essentially the same. In other words, Lithium battery systems are able to output large amounts of power over very short durations while still being able to delivery large amounts of energy. Lithium batteries still experience Pukert’s Law, but this is usually when comparing discharge durations between 1 hour and 10 minutes.

Figure 9: Example of Pukert’s Law with Lead Acid Batteries

Ah

Cap

acity

00

Discharge Duration (Hr)50

1000

500

1500

2000

2500

3000

3500

4000

100 150 200 250

Testing Conditions: 25°C / 77°F , 0.5C Charge. 100% DOD

C-Rate

Cyc

les

0

1000

2000

3000

4000

5000

6000

7000

8000

0 1 2 3 4 5 6

Cycles vs C-Rate

Figure 10: Discharge Rates (C-Rate) vs Cycle Life for Lithium Batteries

Lithium batteries will experience decreased cycle life as the discharge rate increases. At such high discharge rates, large amounts of heat are generated within the battery cell, reducing the overall available cycles.

Temperature: When any battery is in an elevated temperature environment, the battery cycle life decreases. In general, higher operating temperatures will degrade battery materials faster, which results in decreased cycle life. The reverse is true at lower temperatures. However, at lower temperatures, the chemical reactions within the battery become more sluggish, resulting in decreased performance and decreased overall capacity. The optimal temperature for operating any battery is 20° C.

Battery Selection

Selecting the best battery for a given application requires a thorough understanding of the performance characteristics of all battery options. The CUB is capable of utilizing a broad range of battery types, which are described in Table 1.

Cycle Life: The number of cycles the battery can perform before it is considered at end of life.Design Life: The number of years the battery can be installed in an application before the battery is no longer usable. Design life is separate from cycle life, as it is more related to aging of materials over time as opposed to cycling degradation.Volumetric Efficiency: The volume per unit energy contained within each battery. Density: The mass per unit energy contained within each battery.Initial Investment: The relative upfront cost for each battery per kWhr of energy.Life cycle Cost: The relative cost per kWhr of energy discharged from the battery over the life of the battery. Similar to lifetime operating cost.

Power Conversion Electronics

The CUB both stores energy and manages power flow between sources of generation and loads. The devices that enable this power flow are the bidirectional battery based inverter/chargers. These inverter/chargers allow for the conversion of DC to AC voltage bidirectionally, to and from batteries, from sources of electricity, to loads. The CUB utilizes inverter/chargers from Schneider Electric called the Conext XW+. The XW+ allows for the ultimate in flexibility for system design and offers a simple interface with automated controls.

Inverter/Charger Basics

The major components within an inverter/charger are the inverter, which converts DC to AC voltage bidirectionally, the transformer, which transforms the voltage output from the inverter to a usable voltage, and the transfer switches, which manages the flow of power. The inverter/charger is connected to the battery bank, an AC source like a generator or grid, and the AC loads.Battery Type

SOPzV Tubular

Gel Lead Acid

OPzV Tubular

Gel Lead Acid

OPzS Tubular Flooded

Lead Acid

Lithium Advanced

Energy System

Cycle Life2300 Cycles

at 50% DOD, 20°C

2950 Cycles at 50%

DOD, 20°C

3000 Cycles at 50%

DOD, 20°C

7500 Cycles at 100%

DOD, 20°C, 2 hour rate

Design Life 12 years 20 years 20 years >10 years

Volumetric Efficiency 102 Whr/L 67 Whr/L 64 Whr/L 120 Whr/L

Density 36.5 Whr/kg 27 Whr/kg 28 Whr/kg 86 Whr/kg

Initial Investment $$ $$$ $ $$$$$

Life cycle cost $$$$ $$$ $$ $

Testing Conditions: 2C Discharge. 0.5C Charge. 100% DOD

Cyc

les

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

Temperature (°C)

32 68 104 140Temperature (°F)

0 20 40 60

Cycles vs Temperature

Figure 11: Temperature and Cycle Life Performance of Lithium Batteries

Table 1: Performance Metrics for various Batteries Types

AC AC OutAC

1

2

Transfer Switch

Grid/GeneratorConnection

LoadConnection

Transformer

Bidirectional Inverter

Battery Bank

Figure 12: Simplified Inverter/Charger Layout

Depending on the position of the transfer relay, different power flow arrangements are possible, changing how power flows from source of generation, storage, and loads. Each mode of operation assumes that a generator is connected as the primary source of power.

Invert

When the transfer switch is open, the generator is disconnected from the system. DC power from the batteries is converted to AC power to feed the loads. No power flows from the generator. The system will remain in invert mode until the battery level is too low. These triggers are usually based upon the battery DOD or when a large load is activated.

Pass Through

When the transfer switch is closed, the generator is connected to both the loads and inverter. With a direct connection to the loads, the generator is feeding the loads directly. No power from the generator is flowing into the inverter – the inverter system is essentially idle.

Pass Through Charging

When the transfer switch is closed, the generator is connected to both the loads and inverter. Similar to pass through, the generator is directly connected to the loads, feeding the loads directly. In addition to feeding the loads, the generator is also charging the batteries. The charge rate is dictated by the maximum current rating of the generator and the magnitude of load demand. Priority is given to feeding the loads. If any excess power is available, relative to the maximum generator load, that excess power is used to charge the batteries. When the batteries are fully charged, the generator may now shutdown and return to invert mode.

Generator Support

When the transfer switch is closed, the generator is connected to both the loads and inverter. Similar to pass through, the generator is directly connected to the loads, feeding the loads directly. If the system is configured to do so, the inverter may assist the generator to power loads, thereby permitting the generator to power loads that are larger than the set power limitation of the generator. This is limited by the overall current capability of the transfer switches provided there is sufficient charge remaining in the batteries.

AC AC OutAC

1

2

Figure 13: Invert Mode

AC AC OutAC

1

2

Figure 14: Pass Through Mode

AC AC OutAC

1

2

Figure 15: Pass Through with Charging Mode

AC AC OutAC

1

2

Figure 16: Generator Support Mode

CUB Architecture

The CUB integrates batteries from Discover Energy and inverter/chargers from Schneider Electric into one standard 10 foot shipping container format. The shipping container is highly modified to add full insulation, an HVAC system, and mounting points for all components. With it’s walk-in walk-out design, the CUB is easy to install, commission, service, and maintain, with all components easily accessible within the container.

Each container allows for any number of Conext XW+ inverters, to a maximum of 6. Each inverter is capable of outputting 6.8 kW of continuous power, resulting in a maximum power for one CUB energy cell of 40 kW.

Depending on the number of inverters that are installed, the remaining space in the Energy Cell is reserved for installing the battery bank. If 3 inverters are installed, the equivalent of 180 kWhr of tubular gel lead acid battery can be installed. If 6 inverters are installed, 120 kWhr of batteries may be installed. For Lithium Advanced Energy Systems, the maximum amount that may be installed in each 10 foot container is 360 kWhr.

Many containerized energy storage systems on the market today utilize high voltage battery banks, allowing for a reduction in conductor size due to lower current carrying requirements. But, working with high voltage requires that battery system designs take special care in design for insulation. Insulation limits exposure to electrical potential, which can cause severe injuries. This increases the design complexity and also requires more stringent safety protocols during manufacturing and service. The CUB utilizes a low voltage battery bank, allowing for simplified designs and reduces safety risks during assembly and service.

If more power and energy is needed beyond what can fit within a single energy cell, additional energy cells may be connected together. These connected systems will link together and operate as one, however, they are limited in that no one set of loads may be greater than 80 kW. For example, if 4 energy cells with 40 kW of power each are connected together, the total available power is 160 kW. The energy cells must be split into groups of two, where each group is able to supply a set of loads no greater than 80 kW.

Load Connection

Connection to next EC-10E

Schneider Electric Conext XW+ Battery Based Hybrid Inverter

MPPT 80 600 Solar Solar PV Charge Controller

Generator / Grid

ConnectionHVAC System

Solar PV Input

Battery Monitor

Automatic Gen Start

Conext Combox

System Control Panel

Battery Bank

CUB1 Energy Cell EC-10E

Figure 17: CUB Energy Cell Architecture

20 kW180 kWhr

40 kW360 kWhr

80 kW720 kWhr

Figure 18: Example of System Stacking

80 kW240 kWhr

160 kW480 kWhr Total

80 kW240 kWhr

Figure 19: Example of System Stacking Greater than 80kW

Load Center 1 80 kW Load Center 2 80 kW

down. In order to meet anti-islanding regulations, grid tie solar systems must disconnect from the grid during all grid outages. When disconnected, the grid tie solar system cannot generate any power since they require a grid connection to operate. Utilizing the CUB Energy Cells, when the grid is down, it will provide backup power from the batteries.

Due to its grid forming capability, any grid tie solar that is connected to the Energy Cells will continue to operate and will supply the loads and recharge the batteries. Backup power from the CUB Energy Cells is fully compliant with anti-islanding regulations.

While the grid is up, the Energy Cells can provide additional functionality to reduce energy costs. These functions include offsetting grid penalties such as peak demand and time of use charges.

Grid Support and Services: The CUB Energy Cell can be connected directly to the grid to supply grid support and services such as frequency regulation, voltage support, and VAR support. When installed within a renewable energy installation, they can also provide shifting and smoothing services to even out supply to the grid.

Application Example

In Southern Ontario, Canada, a machine shop facility has been operating off-grid for many years. Although they have had no major issues operating on a diesel generator, they have been frustrated by the increasing operating costs of their facility.

Their business has been fairly stable, but their operating expenses continue to increase. The main culprit was the mounting cost of diesel to operate their facility.

GensetAC Coupled Solar Array

DC Coupled Solar Array

Grid Tie Solar

Inverter

Community Power

Distribution Centre

Community Power Distribution Center

AC Coupled Solar Array Grid Tie Solar

InverterGenset

DC Coupled Solar Array

Commercial /Industrial Facility

AC Coupled Solar Array

Grid Tie Solar Inverter

DC Coupled Solar Array

System Configurations

The CUB’s flexible system architecture allows it to be installed in many different types of applications.

Off-Grid Prime Power: The primary focus of the CUB in an off-grid environment is to minimize generator runtime. By utilizing its energy storage capability, it will provide power to all loads until the battery bank is depleted. The Energy Cell will start the generator to charge the batteries back up and supply the loads, allowing the generator to operate at a much higher efficiency.

By integrating renewables into this solution as a secondary power source, the generator will operate much less frequently, resulting in significant reduction in run time and fuel consumption.

Commercial Backup Power: One of the misunderstandings about grid-tie solar systems is that they will continue to operate when the grid is

Figure 20: Off Grid Prime Example

Figure 21: Commercial Backup Power Example

Figure 22: Renewable Grid Support Example

The given load profile shows that the machine shop operates approximately 6 days a week. In the evenings, the shop needs to maintain some power on, which means the generator needs to operate 24 hours per day. On average, the shop consumes 845 kWhr per day. The absolute peak power draw is 170 kW.

The facility currently uses a Cummins QSB7-G4 170 kW prime power diesel generator. On an annual basis, the generator consumes 147,000 L of fuel, with an average fuel efficiency of 3.27 kWhr/L. Operating 24/7, the generator will require replacement or a complete overhaul every 3 years. At current fuel prices, including the cost of delivery and storage of fuel, and periodic maintenance, the current operating costs are approximately $210,000 per year.

Option 1: Smart Hybrid GeneratorWhen utilizing a generator as the primary power source, the generator must vary its output constantly to meet load demand, which prevents the generator from operating in its most efficient operating range. This is especially prevalent in the evenings when the power consumption is low. Due to the minimum operating range of the generator, when load demand is low, the fuel efficiency decreases significantly. By allowing the generator to only run when necessary, and when running, only operate within its highest efficiency band, fuel consumption can be reduced significantly.

By adding 3 CUB Energy Cells with a total continuous power of 100 kW and energy storage totaling 500 kWhr a significant decrease in fuel consumption can be achieved.

Option 2: Prime PV PowerBy taking the Smart Hybrid Generator concept further, by adding a solar PV array, significant reductions in fuel consumption can be achieved.

As a result of adding a 200 kW solar array to the system, the solar array will generate 68% of the energy needs of the machine shop. These values are for Southern Ontario specifically and will be different for any other location. Of course, the benefits of adding a renewable source of energy are most beneficial when solar or wind resources are readily available. There is significant seasonal variability with solar; therefore, it is still very important to have the generator as an on-demand source of electricity. Variability is demonstrated in Figure 24. During the summer months, solar PV provides almost 90% of the total energy, whereas in the winter months the generator bears almost 70% of the load.

Generator Only Generator with 3X EC-10P

Generator Fuel Consumption 147,831 L 90,385 L

Generator Operating Hours 8760 hours/year 2032 hours/year

Generator Replacement Period 3 years 12.3 years

Generator Fuel Costs $184,788 $112,981Table 2. Performance of Smart Hybrid Generator Setup.

Generator OnlyGenerator with 3X

EC-10P and 200kW Solar

Generator Fuel Consumption 147,831 L 29,280 L

Generator Operating Hours 8760 hours/year 887 hours/year

Generator Replacement Period 3 years 28 years

Generator Fuel Costs $184,788 $36,600Table 3. Performance of Prime PV System.

Figure 23: Weekly Load Profile

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Gen200 Solar

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Figure 24: Annual Solar Output vs Generator

Conclusion

The CUB Energy Cell is a flexible solution ideal for off-grid environments where energy efficiency is the primary concern. By installing CUB Energy Cells, fuel consumption can be reduced significantly, decreasing overall operating costs.

Further to reducing overall operating costs, the CUB Energy Cell offers distinct advantages including:

• Turnkey systems that can be transported and installed anywhere, with minimal on-site expertise and installation time, resulting in significant startup cost savings.

• Flexible systems that can be scaled to any power or energy requirement.

• Broad range of energy storage options, including best in class tubular lead acid and Lithium Advanced Energy Systems.

Specifications

Exterior Dimensions • Length 10 ft x Width 8 ft x Height 8 ft 6 in• Total length up to 12ft with HVAC

Interior Climate Controls • Fully automated HVAC with BARD 2 ton cooling, 6kW heating, with economizer• Interior fully insulated to R20 wakks, R24 ceiling and floor

Power I/O Voltage • 120/240 VAC, 230 VAC, single phase, split phase, 3 phase, 50 or 60 Hz

Continuous Power Ratings • 4.8 to 40.8 kW depending on configuration per container• Systems can be stacked for more power

Available Batteries • Tubular Flooded or Tubular Gel, Lithium

Max Energy Storage• 180 kWhr at 20 hour rate using Tubular Flooded Cells• 360 kWhr at 1 hour rate using Lithium• Systems can be stacked for more energy

Battery Cycle Life • Tubular Lead Acid up to 3000 cycles at 50% DOD 20° C• Lithium more than 7500 cycles at 0.5C rate, 100% DOD 25° C

Max DC Coupled Solar • 57.6 kWp at 600 VDC max (8X MPPT 80 600)

Operating Temperatures • -50° C to +50° C (with HVAC)

• Best in class power electronics from Schneider Electric, the most bankable solar supplier in the world.

• Low voltage architecture does not require specialized safety training or equipment, simplifying service and maintenance .

• Remote connectivity allows for remote monitoring, diagnostics, and data logging.

• Built in HVAC and insulated container provide the ideal environment for the batteries and power electronics, eliminating requirements for separate facilities.

• Fully automated controls manage power flows automatically and ensure efficient operation.

• Walk-in walk-out design allows for easy access to all components, simplifying installation and maintenance