TERMS OF REFERENCE (TOR) DESIGN, SUPPLY AND...

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TERMS OF REFERENCE (TOR)

DESIGN, SUPPLY AND INSTALLATION OF A SMALL SCALE HYBRID

PHOTOVOLTAIC – WIND SYSTEM

A. GLOSSARY OF TERMS

Solar photovoltaic components Crystalline silicon A general category of silicon materials exhibiting a crystalline structure. Symbol: c-Si. (also

single crystalline sc-Si and multi-crystalline mc-Si).

Photovoltaic module or

panel

The smallest complete environmentally protected assembly of interconnected cells. Colloquially

referred to as a "solar module".

Photovoltaic cell The basic photovoltaic device. Colloquially referred to as a "solar cell".

Reference cell A specially calibrated cell that is used to measure irradiance.

Peak capacity STC The power delivered at the maximum power point at standard test conditions (STC).

Hot spot The intense, localized heating of a spot on a cell in a module where a breakdown of the junction

on that cell has occurred due to an excessively high reverse voltage bias or by some damage. This

creates a small, localized shunt path through which a large portion of the module current flows.

Bypass diode (on a module

level)

A diode connected across one or more cells in the forward current direction to allow the module

current to bypass cells to prevent hot spot or hot cell damage resulting from the reverse voltage

biasing from the other cells in that module.

DC converter An electronic component that changes the generator output voltage into a useable d.c. voltage.

Maximum power point

tracking

A control strategy for dc converters whereby the PV generator operation is always near the point

of current-voltage characteristic where the product of current and voltage yields the maximum

electrical power under the operating conditions. Abbreviation: MPPT.

Inverter A system component that converts d.c. electricity into a.c. electricity. One of the family of

components that is included in "power conditioner".

Grid-connected inverter An inverter that is able to operate in grid-parallel with a utility supply authority. Also known as

a grid-tied inverter.

Grid-multi mode inverter A type of inverter that is able to operate in both autonomous and grid-parallel modes according

to the availability of the utility supply authority. This type of inverter initiates grid-parallel

operation.

Autonomous inverter An inverter that supplies a load not connected to an electric utility. Also known as a "battery-

powered inverter" or "stand-alone inverter"

Voltage control inverter An inverter with an output voltage that is a specified sine wave produced by pulse-width

modulated (PWM) control etc.

Current control inverter An inverter with an output current that is a specified sine wave produced by pulse-width


Junction box An enclosure in which circuits are electrically connected and where protection devices can be

located.

Generator junction box A junction box in which the photovoltaic module circuits are electrically connected and where

string protection devices are located.

Utility interface disconnect

switch

A switch at the interface between the photovoltaic system and the utility grid.

Storage Accumulation of electricity in a non-electric form and which can be reconverted through the

system to electricity.

Lead-acid battery An electrochemical electricity storage device commonly used in UPS and autonomous PV

systems.

Vented lead-acid battery A lead-acid battery designed with a vent mechanism to expel gases generated during charging.

Solar photovoltaic power plants Distributed generation

plant

The facility and equipment comprising an electricity generation plant that is interconnected to and

operates in parallel with a distribution system.

Distribution system An electrical facility and its components including poles, transformers, disconnects, isolators and

wires that are operated by an electric utility to distribute electrical energy from substations to

customers. Also referred to as electric grid.

Micro grid A grid that operates at less than 100 kVA of capacity and is electrified by a micro power plant.

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Electric utility The organization responsible for the installation, operation and maintenance of all or some portions

of major electric generation, transmission, and distribution systems.

Genset A colloquial term meaning “engine-generator set” consisting of an engine coupled to a rotating

electric generator.

Individual electrification

plant

A small electric generating system that supplies electricity to one consumption point usually from

a single energy source.

Interconnection the result of the process of electrically connecting a distributed generation plant to a distribution

system in order to enable the two systems to operate in parallel with each other.

Autonomous operation The operating mode in which loads are electrified solely by the PV plant and not in parallel with

the utility. Also known as stand-alone or off-grid.

Grid-connected operation The operating mode in which a PV plant is operating in parallel with an electric grid. Site loads

will be electrified by either or both the utility or the plant. Electricity will be able to flow into the

grid if the utility permits back feed operation.

Grid dual mode operation A grid-connected operation that is able to switch to an autonomous mode and back.

Photovoltaic generator A mechanically integrated assembly of modules or panels and its support structure that forms an

electricity producing sub-system. This does not include energy storage devices or power

conditioners. Also known as array.

Photovoltaic string A circuit of series-connected modules.

Photovoltaic plant A photovoltaic generator and other components that generate and supply electricity suitable for the

intended application. The component list and system configuration varies according to the

application, and could also include: power conditioning, storage, system monitoring and control

and utility grid interface. Also known as a photovoltaic system. Some such plants are grid-

connected and large and others can also be small (micro plants). The following terms describe

common system configurations.

Hybrid photovoltaic plant See multi-source photovoltaic plant.

Multi-source photovoltaic

plant

A power plants with photovoltaic generation operating in parallel with other electricity generators.

Also called a "hybrid" system.

Micro power plant A generating system that produces less than 100 kVA through the use of a single resource or a

multi-source plant.

Site The geographical location of a plant.

Sub-system An assembly of components. The following terms describe common subsystems.

Photovoltaic generator

sub-system

The components that convert light energy into electricity using the photovoltaic effect.

Power conditioning sub-

system

The component(s) that convert(s) electricity from one form into another form that is suitable for

the intended application. Such a sub-system could include the charge controller that converts d.c.

to d.c., the inverter that converts d.c. to a.c., or the charger or rectifier that converts a.c. to d.c..

Storage sub-system The component(s) that store(s) energy.

Monitor and control sub-

system

The logic and control component(s) that supervise(s) the overall operation of the plant by

controlling the interaction between all sub-systems.

Safety disconnect sub-

system

The component(s) that monitor(s) utility grid conditions and open(s) a safety disconnect for out-

of-bound conditions.

Data logging and

evaluation sub-system

The measurement and logic component(s) that register and process all relevant operational

parameters and data of the plant to establish the daily, monthly and annual final yields, losses and

performance of the subsystems.

Solar photovoltaic plant performance parameters Standard test conditions

(STC)

Reference values of in-plane irradiance (GI,ref = 1 000 W.m-2), air temperature (25°C), and air

mass (AM = 1,5) to be used during the testing of any photovoltaic device. Abbreviation: STC.

Voltage of a photovoltaic

generator

the PV generator voltage is considered to be equal to open circuit voltage under worst case

conditions.

Open circuit voltage of a

photovoltaic generator

The open circuit voltage at STC of a PV generator, and is equal to: VOC pvg = VOC MOD X M

,where M is the number of series-connected PV modules in any PV string of the generator. .

Abbreviation: VOC pvg.

Short circuit current of a

photovoltaic generator

the short circuit current at STC of a PV generator, and is equal to: ISC pvg = ISC STC MOD X Sg,

where Sg is the total number of parallel-connected strings in the PV generator.

Load An electrical component that converts electricity into a form of useful energy and only operates

when voltage is applied.

Performance ratio The overall effect of losses on an array's rated output due to array temperature, incomplete

utilization of the irradiation, and system component inefficiencies or failures. Commonly found by

the quotient of the final system yield over the reference yield. Symbol: PR

Yield The equivalent amount of time that a plant would need to operate at its rated capacity at STC in

order to generate the same amount of energy that it actually did generate. A yield indicates actual

device or system operation normalized to its rated capacity.

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Reference yield The amount of time that the irradiance would need to be at reference irradiance levels to contribute

the same incident irradiation as actually occurred. It is calculated from the quotient of the total

irradiation over the reference irradiance. Symbol: Yr. NOTE: If GI,ref = 1 kW⋅m−2 then the

irradiation as expressed in kWh⋅m-2 over any period of time is numerically equal to energy as

expressed in kWh⋅kW-1 over that same period. Thus Yr would be, in effect, "peak sun-hours" over

that same period.

Final plant yield The net energy that was supplied during a given period of time by the photovoltaic generator

normalized to its rated PV capacity. Symbol: Yf.

Final annual yield The total photovoltaic energy delivered to the load during one year per unit of installed PV capacity.

Losses The electrical power or energy that does not result in the service that is intended for the electricity.

Normalized losses The amount of time that a device or system would need to operate at its rated capacity in order to

provide for system energy losses. These are commonly calculated from a difference in yields.

Plant rated power Pertaining to PV autonomous plants: The power generated when connected to a rated load.

Pertaining to PV grid-connected plants: The power that can be injected under standard operating

conditions.

Generator rated capacity The rated power generation of a photovoltaic generator, usually at STC.

Generator yield The photovoltaic energy generated per unit of installed generator capacity. Also referred to as array

yield. Symbol: Ya.

PV generator capture

losses

The normalized losses due to photovoltaic generator operation, found by the difference between

the reference yield and the generator yield. It includes mismatch losses, temperature effect and non

dispatchable yield. Symbol: Lc.

Module mismatch loss The difference between the total maximum power of devices connected in series or parallel and the

sum of each device measured separately under the same conditions. This arises because of

differences in individual device I-V characteristics. Units: W or dimensionless expressed

normalized.

Efficiency The ratio of output quantity over input quantity. The quantity specified is normally the power,

energy, or electric charge produced by and delivered to a component. Symbol: η is commonly

used. Units: dimensionless, usually expressed as a percentage (%).

Rated efficiency Pertaining to a device: The efficiency of a device at specified operating conditions, usually standard

test conditions (STC).Pertaining to an inverter: The efficiency of an inverter when it is operating

at its rated output.

Power efficiency The ratio of active output power to active input power.

Partial load efficiency The ratio of the effective inverter output power to its input power at a specified load.

Weighted average

conversion efficiency

A method of estimating the effective energy efficiency. It is calculated as the sum of products of

each power level efficiency and related weighting coefficients depend on a regional irradiance

duration curve. When the plant is an autonomous type with a storage subsystem, the weighting

coefficients depend on the load duration curve.

Storage rated capacity The energy (or charge) that can be withdrawn from the storage device under specified discharge

rate (time) and temperature conditions.

Residual capacity The charge or energy capacity remaining in an electrical storage device following a partial

discharge.

State of charge The ratio between the residual capacity and the rated capacity of a storage device. Abbreviation:

SOC. Units: dimensionless, usually expressed as a percentage (%).

Partial state of charge A state indicating that an electrical storage device has not reached a full charge. Abbreviation:

PSOC. Units: dimensionless, usually expressed as a percentage (%).

Depth of discharge A value to express the discharge of an electrical storage device. The ratio of the discharge amount

to the rated capacity is generally used. Abbreviation: DOD. Units: dimensionless, usually

expressed as a percentage (%).

Charging efficiency A generic term to express ampere-hour efficiency (or less commonly, watt-hour efficiency.

Ampere-hour efficiency The ratio of the amount of electrical charge removed during discharge conditions to the amount of

electrical charge added during charge conditions in an electrical storage device.

Watt-hour efficiency The ratio of the amount of electrical energy removed during discharge conditions to the amount of

electrical energy added during charge conditions in an electrical storage device.

Inverter rated power The power that can be supplied by the inverter at 25 ºC. In grid-connected mode it refers to a

continuous operating condition, in autonomous mode it usually refers to a 30’ surge.

Inverter efficiency The ratio of the useful inverter output to its input.

Overload capability Output power level beyond which permanent damage occurs to a device or system. It is expressed

by the ratio of overload power to rated load power for a period of time. Units: dimensionless

(usually expressed as a percentage, %), and minutes.

No load loss Input power of the converter when its load is disconnected and output voltage is present.

Standby loss The power drawn by a power conditioner when it is in standby mode. Units: W. Pertaining to stand-

alone power conditioners: The d.c. input power. Pertaining to grid-connected power conditioners:

The power drawn from the utility grid.

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Environmental parameters Ambient temperature The temperature of the air surrounding a PV generator as measured in a vented enclosure and

shielded from solar. Symbol: Tamb. Unit: °C.

Angle of incidence The angle between the direct irradiant beam and the normal to the active surface.

Azimuth angle The projected angle between a straight line from the apparent position of the sun to the point of

observation and a horizontal line normal to the equator. This is measured from due north in the

southern hemisphere and from due south in the northern hemisphere. Negative azimuth values

indicate an eastern orientation and positive values a western orientation. Symbol: α.

Solar elevation angle The angle between the direct solar beam and the horizontal plane. Symbol: θ.

Tilt angle The angle between the horizontal plane and the plane of the module surface.

Irradiance Electromagnetic radiated power incident upon a surface, most commonly from the sun or a solar

simulator. Symbol: G. Unit: W⋅ m-2.

Global irradiance Irradiance on a horizontal surface. This equals horizontal direct irradiance plus horizontal diffuse

irradiance.

In-plane irradiance Total irradiance on the plane of a device. Symbol: GI.

Solar energy Common term meaning irradiation.

Irradiation Irradiance integrated over a specified time interval. Symbol: H. Unit: J⋅ m-2.]

Testing and certification Inspection Evaluation for conformity by measuring, observing, testing, or gauging the relevant characteristics

as required by the technical specifications.

Tests Technical operations to establish of one or more characteristics of a given product or service

according to a specified procedure.

Acceptance testing Site-specific testing to assure acceptable performance as required by the technical specifications.

Verification Confirmation by examination and recording of physical evidence that specified requirements have

been met.

Verification testing Site-specific, periodic testing to assure continued acceptable performance.

Certificate of conformity A label, nameplate, or document of specified form and content, directly associated with a product

or service on delivery to the purchaser, attesting that the product or service is in conformity with

the requirements of the certification program (e.g., with the referenced standards and

specifications).

Miscellaneous Electromagnetic

interference

The condition where electromagnetic energy interferes with the proper operation of equipment.

Abbreviation: EMI.

Total harmonic distortion The ratio of effective signal of total harmonic to effective signal of basic frequency. Units:

dimensionless, usually expressed as a percentage (%).

Safe extra low voltage

(SELV)

An extra-low voltage system which is electrically separated from earth and from other systems in

such a way that a single fault cannot give rise to the risk of electric shock.

Extra-low voltage (ELV) Voltage not exceeding not exceeding 50 V a.c. and 120 V ripple free d.c (a ripple content not

exceeding 10% r.m.s). Some national standards consider 75 V dc as a maximum. In consideration

of ELV status, VOC of the PV generator must be used

Low voltage.(LV) Voltage exceeding extra-low voltage, but not exceeding 1 000 V a.c. or 1 500 V d.c.

High voltage (HV) Voltage exceeding low voltage.

Class II equipment Equipment in which protection against electric shock does not rely on basic insulation only, but in

which additional safety precautions such as double insulation or reinforced insulation are provided,

there being no provision for protective earthing or reliance upon installation conditions

Class III equipment Equipment in which protection against electric shock relies on supply at SELV and in which

voltages higher than those of SELV are not generated.

Double insulation Insulation comprising both basic insulation and supplementary insulation.

Earthing A protection against electric shocks.

Wind Turbine Components Airfoil The shape of the blade cross-section, which for most modern horizontal axis wind turbines is

designed to enhance the lift and improve turbine performance.

Blade The aerodynamic surface that catches the wind.

Hub The center of a wind generator rotor, which holds the blades in place and attaches to the shaft.

Shaft The rotating part in the center of a wind generator or motor that transfers power.

Alternator A device that produces Alternating Current from the rotation of a shaft.

Generator A device that produces Direct Current from a rotating shaft.

Dump load A device to which wind generator power flows when the system batteries are too full to accept

more power, usually an electric heating element. This diversion is performed by a Shunt

Regulator, and allows a Load to be kept on the Alternator or Generator.

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Tower A structure that supports a wind generator, usually high in the air.

Brake Various systems used to stop the rotor from turning.

Nacelle The body of a propeller-type wind turbine, containing the gearbox, generator, blade hub, and other

parts.

Rotor The rotating part of a wind turbine, including either the blades and blade assembly or the rotating

portion of a generator.

Bearing A device that transfers a force to structural supports. In a wind generator, bearings allow the Shaft

to rotate freely, and allow the machine to Yaw into and out of the wind.

Gearing Using a mechanical system of gears or belts and pulleys to increase or decrease shaft speed. Power

losses from friction are inherent in any gearing system.

Balance of System In a renewable energy system, refers to all components other than the mechanism used to harvest

the resource (such as photovoltaic panels or a wind turbine). Balance-of-system costs can include

design, land, site preparation, system installation, support structures, power conditioning,

operation and maintenance, and storage.

DC converter See Inverter.

Inverter A device that converts direct current (DC) to alternating current (AC). One of the family of

components that is included in "power conditioner".

Grid-connected inverter An inverter that is able to operate in grid-parallel with a utility supply authority. Also known as

a grid-tied inverter.

Grid-multi mode inverter A type of inverter that is able to operate in both autonomous and grid-parallel modes according

to the availability of the utility supply authority. This type of inverter initiates grid-parallel

operation.

Battery multi mode inverter A type of inverter that is able to operate in both autonomous and grid-parallel modes according

to the availability of the utility supply authority. This type of inverter initiates autonomous

operation.

Autonomous inverter An inverter that supplies a load not connected to an electric utility. Also known as a "battery-

powered inverter" or "stand-alone inverter"

Voltage control inverter An inverter with an output voltage that is a specified sine wave produced by pulse-width


Current control inverter An inverter with an output current that is a specified sine wave produced by pulse-width


Junction box An enclosure in which circuits are electrically connected and where protection devices can be

located.

Generator junction box A junction box in which the photovoltaic module circuits are electrically connected and where

string protection devices are located.

Utility interface disconnect

switch

A switch at the interface between the photovoltaic system and the utility grid.

Storage Accumulation of electricity in a non-electric form and which can be reconverted through the

system to electricity.

Lead-acid battery An electrochemical electricity storage device commonly used in UPS and autonomous PV

systems.

Vented lead-acid battery A lead-acid battery designed with a vent mechanism to expel gases generated during charging.

Wind Power System Distributed generation

power system

The facility and equipment comprising an electricity generation plant that is interconnected to and

operates in parallel with a distribution system.

Distribution system An electrical facility and its components including poles, transformers, disconnects, isolators and

wires that are operated by an electric utility to distribute electrical energy from substations to

customers. Also referred to as electric grid.

Grid The utility distribution system. The network that connects electricity generators to electricity users.

Micro grid A grid that operates at less than 100 kVA of capacity and is electrified by a micro power plant.

Electric utility The organization responsible for the installation, operation and maintenance of all or some portions

of major electric generation, transmission, and distribution systems.

Anemometer A device to measure the wind speed.

Genset A colloquial term meaning “engine-generator set” consisting of an engine coupled to a rotating

electric generator.

Individual electrification

plant

A small electric generating system that supplies electricity to one consumption point usually from

a single energy source.

Interconnection The result of the process of electrically connecting a distributed generation plant to a distribution

system in order to enable the two systems to operate in parallel with each other.

Autonomous operation The operating mode in which loads are electrified solely by the Wind Turbine and not in parallel

with the utility. Also known as stand-alone or off-grid.

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Grid-connected operation The operating mode in which a Wind Turbine is operating in parallel with an electric grid. Site

loads will be electrified by either or both the utility or the plant. Electricity will be able to flow into

the grid if the utility permits back feed operation.

Grid multi mode operation A grid-connected operation that is able to switch to an autonomous mode and back.

Wind generator/turbine A device that captures the force of the wind to provide rotational motion to produce power with an

alternator or generator. It comprises a rotor, a generator or alternator mounted on a frame, a tail

(usually), a tower, a wiring and the “Balance Of System” components

Wind farm A group of wind turbines often owned and maintained by one company. Also known as a wind

power system.

Hybrid wind power

system

See multi-source wind power system.

Multi-source wind power

system

A power system with wind generation operating in parallel with other electricity generators. Also

called a "hybrid" system.

Micro power plant A generating system that produces less than 100 kVA through the use of a single resource or a

multi-source plant.

Site The geographical location of a plant.

Sub-system An assembly of components. The following terms describe common subsystems.

Wind generator sub-

system

The components that convert wind energy into electricity using the kinetic energy of the wind.

Power conditioning sub-

system

The component(s) that convert(s) electricity from one form into another form that is suitable for

the intended application. Such a sub-system could include the charge controller that converts d.c.

to d.c., the inverter that converts d.c. to a.c., or the charger or rectifier that converts a.c. to d.c..

Storage sub-system The component(s) that store(s) energy.

Monitor and control sub-

system

The logic and control component(s) that supervise(s) the overall operation of the plant by

controlling the interaction between all sub-systems.

Safety disconnect sub-

system

The component(s) that monitor(s) utility grid conditions and open(s) a safety disconnect for out-

of-bound conditions.

Data logging and

evaluation sub-system

The measurement and logic component(s) that register and process all relevant operational

parameters and data of the plant to establish the daily, monthly and annual final yields, losses and

performance of the subsystems.

Wind Power System Performance Parameters Average wind speed The mean wind speed over a specified period of time.

Cut-in wind speed The wind speed at which a wind turbine begins to generate electricity.

Cut-out wind speed The wind speed at which a wind turbine ceases to generate electricity.

Start-up wind speed The wind speed at which a wind turbine rotor will begin to spin. See also Cut-in wind speed.

Open-Circuit Voltage The voltage that a alternator or generator produces when it is NOT connected to a Load.

Downwind On the opposite side from the direction from which the wind blows.

Upwind On the same side as the direction from which the wind is blowing—windward.

Furling A passive protection for the turbine in which the rotor folds either up or around the tail vane.

HAWT Horizontal axis wind turbine.

VAWT Vertical axis wind turbine.

Power coefficient The ratio of the power extracted by a wind turbine to the power available in the wind stream.

Power curve A chart showing a wind turbine power output across a range of wind speeds.

Weibull distribution A probability distribution function often used for wind regime presentation. This is the probability

of the wind having a specified speed in a certain period, e.g. a year. This distribution function

depends on two parameters, the shape parameter, which controls the width of the distribution and

the scale parameter, which depends on the average wind speed. The probability of wind occurrence

over each year remains similar, hence annual power production of turbines is reasonably

predictable.

Betz Coefficient 59.3 percent. This is the theoretical maximum efficiency at which a wind generator can operate, by

slowing the wind down. If the wind generator slows the wind down too much, air piles up in front

of the blades and is not used for extracting energy.

Rated output capacity The output power of a wind machine operating at the rated wind speed.

Rated wind speed The lowest wind speed at which the rated output power of a wind turbine is produced.

Rotor diameter The diameter of the circle swept by the rotor.

Rotor speed The revolutions per minute of the wind turbine rotor.

Swept area The area swept by the turbine rotor, A = π R2, where R is the radius of the rotor.

Tip speed ratio The speed at the tip of the rotor blade as it moves through the air divided by the wind velocity. This

is typically a design requirement for the turbine.

Yaw The movement of the tower top turbine that allows the turbine to stay into the wind.

Load An electrical component that converts electricity into a form of useful energy and only operates

when voltage is applied.

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Performance ratio The overall effect of losses on an array's rated output due to array temperature, incomplete

utilization of the wind resource, and system component inefficiencies or failures. Commonly found

by the quotient of the final system yield over the reference yield. Symbol: PR

AEP Annual Energy Production, the calculated or measured energy delivered by a wind turbine.

Expressed in kWh/y.

Losses The electrical power or energy that does not result in the service that is intended for the electricity.

Normalized losses The amount of time that a device or system would need to operate at its rated capacity in order to

provide for system energy losses. These are commonly calculated from a difference in yields.

Efficiency The ratio of output quantity over input quantity. The quantity specified is normally the power,

energy, or electric charge produced by and delivered to a component. Symbol: η is commonly

used. Units: dimensionless, usually expressed as a percentage (%).

Rated efficiency Pertaining to a device: The efficiency of a device at specified operating conditions, usually standard

test conditions (STC).Pertaining to an inverter: The efficiency of an inverter when it is operating

at its rated output.

Power efficiency The ratio of active output power to active input power.

Partial load efficiency The ratio of the effective inverter output power to its input power at a specified load.

Weighted average

conversion efficiency

A method of estimating the effective energy efficiency. It is calculated as the sum of products of

each power level efficiency and related weighting coefficients depend on a regional irradiance

duration curve. When the plant is an autonomous type with a storage subsystem, the weighting

coefficients depend on the load duration curve.

Storage rated capacity The energy (or charge) that can be withdrawn from the storage device under specified discharge

rate (time) and temperature conditions.

Residual capacity The charge or energy capacity remaining in an electrical storage device following a partial

discharge.

State of charge The ratio between the residual capacity and the rated capacity of a storage device. Abbreviation:

SOC. Units: dimensionless, usually expressed as a percentage (%).

Partial state of charge A state indicating that an electrical storage device has not reached a full charge. Abbreviation:

PSOC. Units: dimensionless, usually expressed as a percentage (%).

Depth of discharge A value to express the discharge of an electrical storage device. The ratio of the discharge amount

to the rated capacity is generally used. Abbreviation: DOD. Units: dimensionless, usually

expressed as a percentage (%).

Charging efficiency A generic term to express ampere-hour efficiency (or less commonly, watt-hour efficiency.

Ampere-hour efficiency The ratio of the amount of electrical charge removed during discharge conditions to the amount of

electrical charge added during charge conditions in an electrical storage device.

Watt-hour efficiency The ratio of the amount of electrical energy removed during discharge conditions to the amount of

electrical energy added during charge conditions in an electrical storage device.

Inverter rated power The power that can be supplied by the inverter at 25 ºC. In grid-connected mode it refers to a

continuous operating condition, in autonomous mode it usually refers to a 30’ surge.

Inverter efficiency The ratio of the useful inverter output to its input.

Overload capability Output power level beyond which permanent damage occurs to a device or system. It is expressed

by the ratio of overload power to rated load power for a period of time. Units: dimensionless

(usually expressed as a percentage, %), and minutes.

No load loss Input power of the converter when its load is disconnected and output voltage is present.

Standby loss The power drawn by a power conditioner when it is in standby mode. Units: W. Pertaining to stand-

alone power conditioners: The d.c. input power. Pertaining to grid-connected power conditioners:

The power drawn from the utility grid.

Environmental parameters Ambient temperature The temperature of the air surrounding a PV generator as measured in a vented enclosure and

shielded from solar. Symbol: Tamb. Unit: °C.

Turbulence The changes in wind speed and direction, frequently caused by obstacles.

Wind shear A term and calculation used to describe how wind speed increases with height above the surface

of the earth. The degree of wind shear is a factor of the complexity of the terrain as well as the

actual heights measured. Wind shear increases as friction between the wind and the ground

becomes greater. Wind shear is not a measure of the wind speed at a site.

Testing and certification Inspection Evaluation for conformity by measuring, observing, testing, or gauging the relevant characteristics

as required by the technical specifications.

Tests Technical operations to establish of one or more characteristics of a given product or service

according to a specified procedure.

Acceptance testing Site-specific testing to assure acceptable performance as required by the technical specifications.

Verification Confirmation by examination and recording of physical evidence that specified requirements have

been met.

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Verification testing Site-specific, periodic testing to assure continued acceptable performance.

Certificate of conformity A label, nameplate, or document of specified form and content, directly associated with a product

or service on delivery to the purchaser, attesting that the product or service is in conformity with

the requirements of the certification program (e.g., with the referenced standards and

specifications).

Miscellaneous O&M costs Operation and maintenance costs.

Electromagnetic

interference

The condition where electromagnetic energy interferes with the proper operation of equipment.

Abbreviation: EMI.

Total harmonic distortion The ratio of effective signal of total harmonic to effective signal of basic frequency. Units:

dimensionless, usually expressed as a percentage (%).

Safe extra low voltage

(SELV)

An extra-low voltage system which is electrically separated from earth and from other systems in

such a way that a single fault cannot give rise to the risk of electric shock.

Extra-low voltage (ELV) Voltage not exceeding 50 V a.c. and 120 V ripple free d.c (a ripple content not exceeding 10%

r.m.s). Some national standards consider 75 V dc as a maximum.

Low voltage.(LV) Voltage exceeding extra-low voltage, but not exceeding 1 000 V a.c. or 1 500 V d.c.

High voltage (HV) Voltage exceeding low voltage.

Class II equipment Equipment in which protection against electric shock does not rely on basic insulation only, but in

which additional safety precautions such as double insulation or reinforced insulation are provided,

there being no provision for protective earthing or reliance upon installation conditions

Class III equipment Equipment in which protection against electric shock relies on supply at SELV and in which

voltages higher than those of SELV are not generated.

Double insulation Insulation comprising both basic insulation and supplementary insulation.

Earthing A protection against electric shocks.

B. TECHNICAL SEPCIFICATIONS

1. GENERAL REQUIREMENTS

1.1 Environmental and climatic conditions

All equipment shall be fully operational in the following conditions:

Relative humidity up to 95%

Ambient temperature from 10ºC to 45ºC

Rural environment with high presence of dust, insects, etc.

External equipment shall additionally withstand the following conditions:

High ultra violet radiation

Wind speeds up to 120 km/h

The ability of the equipment of the same basic design and size to operate correctly in the indicated

environmental and climatic conditions shall be proven by appropriate documentation on

successful operation of at least 5 years.

1.2 Functional configuration

The selected sites requiring the backup facilities have priority loads with the main consumption

during the daytime. This means that under typical average conditions the coincidence factor

between the load profile and the PV generation is high (> 80%) and for WTG is estimated to be

lower ((> 40%).

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To size the backup facilities, it has been considered the solar resource as the main sizing factor.

Wind is not considered as a sufficient reliable source to provide the average daily energy needed

for each installation. So the wind is to be considered only as a complement RE source to help the

PV generators for battery charge or load feeding depending on grid status.

In sites where equipment is running 24/7, the coincidence factor would be higher. Also when

people are present 24/7 therefore using some load during night time such as lighting and TV.

Coincidence factor between the load profile and RE generation is estimated to be around 85%.

When there is grid supply, the RE generation helps to reduce the consumption from the utility grid

by supplying the priority load of the facility and charging the battery, as well as potentially back-

feeding to the grid any surplus production.

During grid black outs, power is taken from the DC side (RE generators and battery) to fill the

gap and provide back-up electrical supply to the secured priority loads whilst the non essential

loads remain disconnected until the grid is available again.

The functional description of the facility can be summarized as follows:

Grid with normal supply

Grid with poor voltage conditions

Autonomous operation to supply secured loads in case of grid black out

Battery charging from RE.

Back feeding to the internal grid

Back feeding to the utility grid

The modes of operation are automatically triggered by the load management and plant supervision

strategy and the state of charge of the battery, RE generation and conditions of the day: switch off

certain loads, charging exclusively from RE or not, etc. Also data will be recorded to validate the

optimum strategies of operation.

Grid with normal supply:

The RE generator works independently of the grid supply. Therefore, if there is resource (solar

radiation or wind accordingly), it will charge the battery or maintain its floating voltage level.

The dual inverter and the battery’s supervisory control shall measure the battery voltage and the

current to/from the grid and to the priority loads and give priority to consume energy from the RE

generator and, if there is surplus generation, back feed of any excess. If there are other loads

connected on the general feeders, they will be also partially supplied from this surplus and if there

are not, the surplus will back feed into the grid.

If the battery state of charge is abnormally low, the inverter that supplies the priority loads can

also be used to charge the battery. In any case, the total current drawn from the grid by the inverter

shall be limited to 20A.

To be noticed that for particular cases where no grid feeding is allowed, the surplus of energy, if

any, will be use exclusively by feeding the other loads on the general feeder line. Then if there is

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more RE production than the total loads, both PV and Wind generator would start to regulate their

output to match the demand.

Grid with poor voltage conditions:

When the grid has a voltage sag, but it is above 165V AC, the dual inverter shall operate at such

a low voltage and continue to charge or inject power. The tolerances shall be configured after

preliminary testing.

Operation of the RE back up in case of grid black out:

A black out condition exists if the grid is out or has a continuous voltage lower than 165V AC.

Even considering that black outs can be longer, it has been estimated that the longest back up

period will be 6 hours because the schools’ typical opening hours are up to 6 hours The supply of

the secured loads is done from the battery through the multi-mode inverter. Since the facilities

selected consume during the daytime, most of the time the PV generator will, at the same time,

keep the battery charged.

During daytime, the WT generator will help the PV generator to keep the battery charge. During

night time the WT generator will charge the battery in case that solar resource was not enough

during the past day.

During the backup mode all the non essential loads in the premises remain disconnected. The

capacity of the RE generators has been calculated to provide, under average conditions, at least

50% of the energy of the maximum rated secured load.

It has been also estimated that larger installations have more capacity to manage the secured load

and reduce it on days with poor RE generation. Thus, the practical capacity of the battery has been

calculated to provide, under average conditions, from 1 day of autonomy at the rated secured load

for smaller facilities to 0,5 days for the larger ones.

Return to the initial conditions:

Once the interruption is over, the plant can restart the interconnection to the grid through the

transfer switch. The inverter shall measure the phase and synchronize before resuming back-

feeding or battery charging.

Battery charging from the grid :

After a black out, the battery may need to be recharged either from the RE generator or from the

grid side, It is important to take into account the fact that adequate charging requires a sequence

with bulk charge, equalization and floating. The Battery supervisory controller and data logger

shall monitor the general conditions of RE availability, period of the year, etc. and the RE battery

charger, PV and WTG where applicable, shall control the PV/WTG duty cycle. The dual inverter

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shall be programmed so that it charges the battery only to reduced floating charge voltage so that

during RE generation there is still some room available for storage.

1.3 General layout

To achieve modularity and economies of scale, the designs have a similar configuration and the

difference is in the size and ratings of some of the components.

The MSB micro power plants (multi source back up) are a solution with both PV and WTG for

sites where PV generator represent the main RE potential and is complemented by WTG. Wind

resources in the selected site are not steady enough to be considered reliable and as a consequence

the sizing of the MSB micro power plant is done regarding solar resources.

They design consists of a Wind Turbine Generator and its interface module and DC voltage

controller, a PV generator, a dual-mode inverter, a battery, a PV charge controller (MPPT), a

supervisory control and data logger with its sensors, load management switchgear and its

associated ancillary and surge overvoltage protection equipment.

1.4 Mechanical design and exposure to environmental conditions

Support structures and mounting arrangements should comply with applicable building codes,

regulations and standards. Particular attention should be given to wind loads on PV and WT

generators and their structures so that they withstand up to 120 km/h.

All structures shall be made of corrosion resistant materials e.g. aluminium, galvanized steel,

treated wood structures, etc. If the structure is metallic, aluminium or hot dipped galvanized steel

are well suited to this type of use. The same applies to all bolts, nuts, guy wires and fasteners.

Provisions shall be made in order not to create electrochemical corrosion between the structures

and the building on the one hand, and the structures and photovoltaic modules on the other. The

negative conductor should be connected to the earth electrode as this arrangement will reduce

electro-chemical degradation of the electrode and other metallic parts.

Outdoor generator wiring and associated components are exposed to UV, wind, water and other

environmental conditions. Wiring and components should be fit for this purpose and built in such

a way as to minimize exposure to detrimental environmental affects. Particular attention is drawn

to the need for prevention of water accumulation in cable/module supports.

1.5 Safety issues

1.5.1 Protection against electric shock in the d.c. side shall be achieved by extra-low voltage

(SELV systems) together with components and systems classified as Class III or better and

galvanic isolation or equivalent of the inverter.

If the WTG output voltage exceeds SELV all the wiring and equipment at that voltage shall be

classified class II or better.

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For the a.c. side, protection by double or reinforced insulation between any live conductor and

any earthed or exposed conductive part is required.

1.5.2 Protection against fire

Direct current systems, and photovoltaic generators in particular, pose various hazards in addition

to those derived from conventional a.c. power systems, for example the ability to produce and

sustain electrical arcs with currents that are not much greater than normal operating currents. A

fire-fighting extinguisher for electrical fires shall be provided attached to the equipment cabinet.

1.5.3 Protection against over current

Battery over current protection: All battery cables over current protection shall be placed as close

as possible to the battery.

The inverter’s cable over current protection shall be installed between the battery and the inverter

as close as possible to the battery.

The WT generator’s cable over current protection shall be installed between the battery and the

charge controller as close as possible to the battery or d.c. bus bar.

The PV generator’s cable over current protection shall be installed between the battery and the

charge controller as close as possible to the battery or d.c. bus bar.

In the PV generator protection against over current in required in the strings: Fault currents due to

short circuits in modules, in junction boxes or in module wiring or earth faults in wiring can result

in over current in a PV generator. PV modules are current limited sources but because they also

connected to batteries, they can be subjected to over currents caused by either multiple parallel

adjacent strings or from external sources or both. For this reason over current protection in each

string is required.

1.5.4 Protection against effects of lightning and surge over-voltage

DC side:

Damage caused by over-voltage is ultimately due to the failure of insulation between live parts or

between live parts and earth. The intention of over-voltage protection is to equalize all exposed

metallic sections of an installation to a common potential during the event of an over-voltage.

Equipotential bonding is therefore required as an important over-voltage protection measure and

shall be done in accordance with recognized standards or acceptable state of the art procedures.

To avoid the formation of wiring loops between earthed conductors and d.c. cabling, equipotential

bonding conductors should run parallel and as close as possible to the d.c. cabling. It is also

recommended to branch the bonding conductor to run parallel with all the d.c. cabling branches.

The installation of a PV generator on a building has a negligible effect on the probability of direct

lightning strikes; therefore it does not necessarily imply that a lightning protection system should

be installed if none is already present.

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The WTG may pose some concern depending of the location. Manufacturer’s specific

recommendations should be followed strictly.

AC side: Additionally, electronic components used in a back up application have to be protected

from surge overvoltage coming from the public distribution grid by EDL (outdoor-cables) during

storms.

1.6 EARTHING SYSTEM

The objective is to create an earth connection to which all relevant components of the new

installation will be bonded and also to protect the new distribution installation with differential

switches. Place as many earth rods as necessary at the appropriate location as to ensure a resistivity

value around 30 Ohm (max 80 Ohm) (several rods would most likely be enough), and install a

ground box with 16 mm2 wire between rods and box. Connect metallic chassis of all electronic

equipment and PV structure with 6 mm2 ground wire. Ground also the negative pole of the battery

(on the component side of the fuse). The SPD (Surge Protection Device) shall also be grounded.

Install two differential switches, one at the AC utility side of the inverter and one at the AC outlet

of the inverter. These shall be located either at the existing main panel (if there is enough space)

or on a new complementary panel near it. The new feeder line for priority loads shall have 2 cables

+ earth.

2. COMPONENTS

2.1 The PV Generator

2.1.1 Orientation for optimum yield

To optimize the PV generator’s production with respect to the estimated load it is necessary to

fulfil the following requirements:

The tilt angle and azimuth of the modules has been established to optimize the production in

relation to the needs which are mainly in the morning hours. However, if the building does not

allow the orientation of these two parameters within the specified range (roof not orientated south,

partial shading, etc) it shall be clearly accounted for in the siting phase to recalculate a larger STC

rated capacity of the PV generator to achieve an equivalent production.

The surface for fitting photovoltaic modules to structures shall be perfectly flat in order not to

induce mechanical stresses on securing the modules. Moreover, there shall be accessibility to

perform for periodical cleaning and inspection.

The PV generator can be mounted on south walls, south facing tilted roofs or flat roofs preferably

in single rows. If they have to be arranged in rows, no shadow should be generated from one row

to another.

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Shadowing of the PV modules from trees, buildings or any other obstacles should be minimized

over the whole day and there shall be no shadows in a period of ± 4h w.r.t. solar noon.

A shadow partially blanking off a photovoltaic cell may cause hot spots and loss of almost the

whole production of this module, significantly reducing the performance of a complete string.

2.1.2 PV modules

They shall be crystalline silicon PV modules that comply with the norm IEC 61215 edition 2 and

shall be qualified to and be classified by Class according to IEC 61730.

The modules shall be made of a series-connection of 36 cells. Amorphous silicon and other thin

film type cells are not acceptable under this tender.

The outside junction boxes with the positive and negative terminals shall incorporate bypass

diodes that have the function of preventing any possibility of the electrical circuit inside the

module being broken due to the partial shading of a cell.

The design is based on a module capacity at STC of 75 Wp but it is technically possible to achieve

the same characteristic of the PV generator with larger modules and a different layout. Offerors

can propose other module capacities for approval as long as the total PV generator capacities in

the general specifications are met and each string has not more than the modules in series so that

the Voc of the generator is within the specifications.

2.1.3 PV generator junction boxes

PV generator junction and fuse boxes are exposed to the environment, shall be readily available,

shall be at least IP 65 and shall be UV resistant. The terminals must be clearly marked with + and

– for the corresponding connections. Connections shall be of a screw type with a capacity of at

least two 4 mm2 wires.

2.1.4 Switching devices

All switching devices, shall comply with the following requirements:

- Have a voltage rating equal to or greater than 1,2xVOCpvg.

- Not have exposed live metal parts in connected or disconnected state.

- Interrupt all poles.

2.1.5 Cables

The typical distance between the PV generator and the cabinet was assumed to be 20 to 30m.

However, if during siting, longer distances are detected the cable sizes for the PV generator cable

shall be determined with regard to both the minimum current capacity and the maximum voltage

drop requirements. The larger cable size obtained from these two criteria shall be applied. Please

note that an additional control cable for sensors needs to be installed between the PV generator

and the cabinet.

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Cables used within the PV generator shall:

have a voltage rating of at least 1,2 VOCpvg that in this case is not a major requirement since ELV

has been chosen for safety reasons; have a temperature rating higher than 40 °C above ambient

temperature; be UV-resistant, or the cables be installed in UV-resistant conduit; water resistant

and it is recommended that they be flexible (multithreaded) to allow for thermal/wind movement

of modules.

Where cable ties are used as a primary means of support they must have a lifetime greater than or

equal to the life of the installation. (No plastic cable ties exposed to UV shall be used)

2.1.6 Fuses

Fuses used in PV generators shall be rated for d.c. use, have a voltage rating equal or greater than

1,2xVOCpvg, be rated to interrupt fault currents from the PV generator and any other connected

power sources such as the battery.

2.1.7 Disconnecting means

Disconnecting means shall be provided in PV generator according to the drawings to isolate it

from the Charge controller/ dc bus bar and vice versa and to allow for maintenance and inspection

tasks to be carried out safely.

2.1.8 Support Structure

The support frames shall be anchored to the roof of the selected sites with great attention to the

water proofing / thermal insulation already exist at the roof of the sites. In case that Owners of the

sites do not approve direct anchoring to the roof of the houses / sites, concrete bases shall be

provided to receive the anchors of the support frames with great attention to the existing water

proofing / thermal insulation

The support frame shall be of either light weight aluminium or galvanized steel and it shall be

easy for installation and maintenance.

2.2 The WT Generator

2.2.1 Location for optimum yield and safety

The objective of the WTB’s is to produce a minimum average daily electricity yield based on the

site specific wind resource given (see dwg # 41-00, dwg # 48-00 and dwg # 55-00). This can be

achieved by one larger unit or up to a maximum of 3 smaller machines. The WT shall be mounted

on towers. To select the location of the WTB the existing obstacles together with the wind rose

shown in the drawings shall be carefully considered for maximum yield. Shading and turbulence

from trees, buildings in the direction of the prevailing winds should be minimized.

Because wind speeds increase with height, the turbine is mounted on a tower. The higher the

tower, the more power the wind system can harvest. The tower also raises the turbine above the

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air turbulence that can exist close to the ground because of obstructions such as hills, buildings,

and trees. A general rule of thumb is to place the wind turbine on a tower with the bottom of the

rotor blades at least 10 meters above any obstacle that is within 80 meters of the tower.

Mounting turbines on rooftops is not recommended except in particular cases where other options

are not as feasible. All wind turbines vibrate and can transmit the vibration to the structure on

which they are mounted. This can lead to noise and structural problems with the building and the

rooftop can cause excessive turbulence that can shorten the life of the turbine.

Safety to people and risk of theft/vandalism also has to be considered.

2.2.2 Wind turbine generators and WTG charge controllers

They shall conform to IEC standards and follow the provisions in directives IEC 1400-2 (small

wind turbines). The type shall be horizontal axis, up wind with a permanent magnet brushless

generator. Since the sites have relatively low wind speeds it shall be a low starting machine (2,5

to 3,0 m/s) while, at the same time have the adequate speed control to protect itself during storms.

Its protection rating shall be IP55. Low sound emission is a requirement.

It shall be supplied together with its own power management and control equipment to charge

batteries of 48 V DC rated voltage with an adjustable set point between 52 and 58 V DC. An

interface module and MPPT is a preferred arrangement but other options of charge control of the

battery are acceptable as long as they are approved by the manufacturer. An output signal of the

power output is recommended (for example RS-485).

An electrical turbine brake switch or equivalent is required to prevent over speed and high open

circuit voltages in case of operation at no load during maintenance or repairs.

2.2.3 WTG generator junction boxes

WTG junction and fuse boxes that are exposed to the environment, shall be readily available, shall

be at least IP 65 and shall be UV resistant. The terminals must be clearly marked with + and – for

the corresponding connections. Connections shall be of a screw type.

2.2.5 Cables

For the purpose of this ITB the typical distance between the WTG generator and the cabinet is 50

to 70m. However, if during siting, longer distances are detected the cable sizes for the generator

cable shall be determined with regard to both the minimum current capacity and the maximum

voltage drop requirements. The larger cable size obtained from these two criteria shall be applied.

Cables used within the WTG generator shall have a voltage rating of at least 1,2 Vmaxwtg; have

a temperature rating higher than 40 °C above ambient temperature; be UV-resistant, or the cables

be installed in UV-resistant conduit; water resistant and it is recommended that they be flexible

(multithreaded) to allow for thermal/wind movement.

Where cable ties are used as a primary means of support they must have a lifetime greater than or

equal to the life of the installation. (exposed outdoor cable ties shall be UV resistant)

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2.2.6 Fuses

Fuses or breakers used in WTG generators shall be rated for d.c. use, have an adequate voltage

rating.

2.2.7 Disconnecting means

Disconnecting means shall be provided in WTG generator to isolate it from the dc bus bar and

vice versa and to allow for maintenance and inspection tasks to be carried out safely. This must

designed as to not damage the WTG from no load operation.

2.2.8 Support Tower

The tower shall be of galvanized steel. Scissor or guyed tower types, fixed or tilt-up are allowed

as long as it shall be easy for installation and maintenance of the WTG.

2.2.9 Lightening Protection

All mounting structures and enclosures shall be earthed for safety following local codes.

For grounding and lightening protection of the equipment the instructions of the manufacturer

should be followed. Typically the generator output wires are not earthed and the negative battery

connection is earthed. Lightning arrestors shall be fitted at the junction box or interface module

input.

2.3 ELECTRICAL STORAGE

2.3.1 Battery

2.3.1.1 Application

The battery feeds the priority loads during black outs in the daytime, while being charged by the

RE generator. Reliability of service is a very important criterion and preference shall be for

batteries which have a proven capability under high cycling and deep discharge conditions.

2.3.1.2 Type

The battery shall be lead-acid, deep discharge type with a permissible repeated deep discharge

without damage. Automotive or starting type batteries are not acceptable under this tender.

The batteries shall be of the open “vented” type and transparent enclosure for easy inspection of

electrolyte level. (Preference is given to tubular construction of the positive plates).

The batteries must be manufactured according DIN 40736-1:Stationay batteries with tubular

positive plates. Capacities, measurements and weights.

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2.3.1.3 Rating

The battery shall have a 48V nominal operating voltage. The battery may be made up of 24 series

connected 2V cells or 8 series connected 6V batteries or 4 series connected 12V batteries but the

price quoted shall be for a complete 48V battery. Parallel connection of cells or batteries is not

acceptable.

The battery shall have at least the rated capacity specified in the drawings at the C100 discharge

rate according to DIN 43539-9.

2.3.1.4 Battery performance

The battery shall have a self-discharge, when new, of less than 5% per month (at 25oC and fully

charged) of its rated capacity.

The battery shall have a Coulombic efficiency of at least 85% and energy conversion efficiency

of at least 85% when new and charged to more than 50% of capacity.

The battery cycle life for discharge/charge regular cycles down to 75% DOD shall be more than

1 000 cycles (According to IEC 896-1).

2.3.1.5 Lifetime

The design lifetime of the batteries shall be of at least 8 years without losing more than 10% of

the rated C100 capacity.

2.3.1.6 Labelling

On each battery the following information has to be provided:

Manufacturer

Serial number

Rated capacity C100

Manufacturing date

Clear indication of the positive and negative pole

Clear indication of maximum and minimum electrolyte level

Safety warning

2.3.2 Cables

The dc bus bar or connexion point to the battery has to be as close to it as possible. Cables used

to connect the battery shall have a temperature rating higher than 20 °C above ambient

temperature.

It is recommended that they be flexible (multithreaded) to allow for easy installation and

maintenance.

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2.3.3 Fuses

Fuses in cables that connect components to the battery shall be rated for d.c. use, be installed

separately as close as possible to the battery terminals and rated to interrupt high fault currents

from the battery

2.3.4 Tray

The battery tray to contain any electrolyte spills shall be constructed of impact and acid resistant

material and shall have the minimum capacity as shown in the drawings.

2.4. MONITOR AND CONTROL SUB-SYSTEM

The PV back-up micro power plants will be delivered and installed with or without monitor and

control sub-system. For the sites were a monitor and control subsystem is required, it should fulfil

the following requirements:

Irradiance Sensor:

Reference pv solar cell with voltage output (aprox 75mV at 1 000W/m2).

DC Current and Voltage Transducers:

Internal or external DC current transducers to measure: Electrical energy from PV

generator, electrical energy to inverter and electrical energy from inverter into battery;

current rating: 200 A.

AC Meters:

Digital single phase meters with output pulse signal (open collector 1 000 p/kWh); class II;

230V-50Hz; input: 5(32) A,. Dimension 1-DIN module, compatible with monitor system

Temperature Gauge:

External ambient temperature sensor to install near PV modules with monitor system.

Communication and Signal Interface:

Device for RS232 interface to PC for real time visualization and download of stored data

and connection of signal from external sensors and meters.

Energy Management and Display Unit:

Energy management computing with display at least of: Power values of PV generator,

power in/out from the inverter (W); battery State of availability (kWh), temperature (ºC)

and voltage (V); irradiance (W/m2); ambient temperature (ºC); installation reference

number; charge controller settings).

The Contractors will have to mount the monitor and control sub-system in the cabinet and wire it.

The final arrangement of components inside the cabinet shall be approved by the projects

supervisor.

Enclosure:

Enclosure to contain the above components to be installed inside a general cabinet.

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Fastening Brackets:

Fastening brackets to install components into a cabinet at the purchaser’s premises

following shop sketches to be provided.

2.5. DATA LOGGER.

The RE back-up micro power plants will be delivered and installed with or without monitors and

control sub-system. For the site where a monitor and control subsystem is required, data logger

should fulfil the following requirements:

Data Logger:

Data logging capacity that computes, averages or integrates at least the following hourly

values: Month, day, hour, Irradiation, PV energy generation, inverter/charger energy input

to the battery, battery energy output to loads (inverter) , AC consumed by the building, AC

delivered to the grid, battery availability, battery temperature, average voltage. The logger

shall have at least the capacity to store one year of data.

Evaluation software

Software PC compatible to perform monthly evaluation reports with at least the following

indicators: year, month, energy values (kWh), in plane avg. daily reference yield (hp), avg.

daily pv generator normalized yield (hp), avg. daily final normalized yield (hp),

performance ratio (%), solar fraction (%), AC energy consumed from the grid, AC energy

delivered to the grid.

Enclosure:


Fastening Brackets:



The Contractors will have to mount the data logger in the cabinet and wire it. The final

arrangement of components inside the cabinet shall be approved by the projects supervisor.

2.6 PV BATTERY CHARGE CONTROLLER

PV charge controller provided with a monitor and control sub-system should fulfil the following

requirements:

MPPT DC/DC converter:

Rated input current: ≥60 A DC;

Input voltage range: 24V to 60V DC;

Nominal battery voltage: 48V DC;

Type of conversion: Step-up/down MPPT;

Topology: PWM;

Battery management system:

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Embedded control with at least the following features:

Recharge algorithm: 3 stages, bulk, equalize and float with battery temperature

compensation and adaptive settings according to battery charge history;

Voltage settings: preset at 2,5 and 2,3 V/cell (20ºC) but adjustable;

Calculation of battery State of Charge: Based on energy balance and operating conditions

of the battery (range from 50 to 3 000 Ah);

Status Indicators:

LED or display status indicators: PV charge condition, bulk/floating.

Temperature Gauge:

External temperature sensor and 2.5 m wiring to attach to battery casing compatible with

charge controller and with monitor system.

Terminals (Power)

Positive and negative terminals for connection of the PV generator and the DC bus bar for

a minimum wire cross section of 16 mm2.

General Switch

Double pole switch between controller and battery with a minimum rating of 50 A

Include switchgear to manually desconnect PV and battery with ratings ≥ 50 A

Terminals (Sensors)

As required to connect the provided sensors.

Enclosure:


Fastening Brackets:



2.7 DUAL-MODE INVERTER

The multi-mode inverter for this application is a 4 000 kW (nominal) bidirectional sinusoidal

inverter. It can operate in autonomous mode as well as grid-tied mode through a transfer switch.

It also requires some additional special functions:

- The operating parameters of the unit shall be configurable as to adjust the power ratings of each

functionality (voltage control inverter, current control inverter, charger and boost). A lower

threshold of battery voltage for the boost function shall be established to ensure an energy reserve

for the blackout situation.

- A boost function which can add power from the dc side to the ac source from the grid according

to the input limit current that shall be configured.

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-A RE priority function which adjusts the instantaneous power consumed from the source

according to the battery voltage. The operation of the solar priority function shall be done with an

automatic adjustment algorithm of the input limit current. The input limit current is decreased, if

there is enough energy available at the DC side, from the initial. The lower the input current, more

power to the load is provided from the dc side by the boost function.

The offeror shall supply also one inverter remote control unit that shall be used for the

configuration of all the inverters.

2.8 ELV DC DISTRIBUTION ELECTRICAL SWITCH AND PROTECTION BOX

All fuses and switch gear on the dc side shall meet the specifications in the drawings and be rated

for dc. The two output lines of inverter (AC IN and AC OUT) will be adapted with the existing

boxes of the buildings with their own safe switches, as shown in the drawings.

2.9 TECHNICAL CABINET

2.9.1 Application

Excluding the PV generator and the AC board and interconnection to the grid, all the components

- i.e. the energy manager, PV charge controller, battery, multi-mode inverter, main board, switches

and protective devices as well as connection of the different components shall be installed in a

cabinet that shall be placed in an accessible area near the main fuse and metering box of the

building.

2.9.2 Size and type

The cabinet size must be adequate to contain all the components and also allow enough space on

top of the battery for inspection, measuring the density of the electrolyte and adding distilled water

as required during maintenance procedures. The size shown on the drawings is only indicative.

The cabinet must, at least, have one transparent side to allow easy visual inspection of the

components. Displays from the inverter, battery management system and charge controller must

be placed as high as possible to facilitate readings by the operator and the bidder can offer taller

cabinets as long as this is taken into consideration.

The cabinet must have two segregated compartments with independent ventilation outlets. No

switches or any spark producing device is allowed on the lower battery compartment. The battery

compartment shall resist the effect of sulphuric acid and have a tray to contain potential spills.

If battery cells are placed in several rows, the cells on the back side shall be higher to allow for

easy visual inspection of the electrolyte level

2.9.3 Labelling

A drawing on the cabinet shall provide warning about safety hazards, e.g. smoking, acid handling,

etc. as well as emergency shutdown procedures.

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A panel on the cabinet shall provide basic operation instructions in Arabic as well as in French or

English.

The contractor shall install a general project information banner at the entry of the school and one

with up keeping and operating instructions for the beneficiary attached to the cabinet. These

banners shall be supplied by the purchaser.

2.10 AC LV LINE CONNECTING TO GRID

2.10.1 Connection point

The line AC IN will be connected after the general safety switch of the existing box of the building

and a differential switch. When the grid is on, this line feeds the non-essential loads and the

Priority Loads it these are higher than the PV production. This line is prepared to back-feed to the

grid when the grid is on and all the Loads are less than the PV production and the battery is full.

2.10.2 AC meters

Energy received from the grid and energy delivered to the grid will be monitored using small AC

meters that can fit in a standard 35mm guide. They will be supplied with the charge controller and

logger and have to be installed in the main or complementary panel. Signal wiring will have to be

installed from this box to the cabinet.

2.10.3 Voltage Surge protection

To protect against surge overvoltage from the utility side it is required to install an SPD (Surge

Protective Device) as near to the inverter as possible. This equipment will leak the energy of the

overvoltage to the ground. For this reason, it is essential that earth terminals be of a good quality

and moreover, it is required that all of the earth terminals be properly connected so as to assure

equipotentiality.

The required SPD has to be able to discharge high currents caused by an induced overvoltage, for

that reasons, it needs to be a type 2 according with IEC 61643 standard. To ensure the good

behaviour of the equipment, it needs to be at least 40kA as maximum current (Imax). Due to the

inverter is a very sensitive equipment, the SPD needs to have been tested, in addition, as a type 3.

The type 3 SPDs are specially designed to protect the most sensitive equipments. In addition to

this technical features, the SPD must incorporate an EMI filter in order to protect the SPD itself

and the equipment from the electromagnetic noise of the electrical grid.

3. INSTALLATION REQUIREMENTS

3.1 General

Site constrains shall be taken into account and pre-installation site visits are required to collate

space available, distances between sub-systems, shading, special loads, etc.

The RE generators shall be placed as near to the storage and power conditioning cabinet meeting

the requirements as specified in the drawings and other clauses.

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For PV, tilt and orientation have been optimized for best performance from September to June

and mostly morning and early afternoon operation.

3.2 PV Generator structure mounting

The PV generators and power and control wiring to the cabinet shall be mounted on flat or pitched

roofs or on buildings façades as necessary to meet the selected site and shall meet the tilt and

orientation and wind resistance as specified in the drawings.

Anchorage of the mounting structure to roofs should take into consideration existing

waterproofing and thermal protection.

Material compatibility, and the use of dissimilar metals shall be considered. PV modules and

mounting hardware (bolts, screws, washers, etc) shall be well protected from corrosion. Steel-

mounting hardware in contact with aluminium hardware is an example of metal combinations that

have a high potential for corrosion.

Dissimilar metals can be separated by washers made of fluorocarbon polymer, phenolic, or

neoprene rubber.

3.3 WT Generator and tower mounting

The height is limited to 24 m above ground level but offerors are encouraged to consider the

optimum arrangement that combines safety and performance. Ground mounted towers are

preferred although, for smaller machines proposed towers could be installed on buildings as long

as there is no risk to building or people and water tightness of the roofs are ensured.

3.4 Placing the cabinet

The cabinet shall be placed near the building’s main electrical protection and metering box. The

exact location must be agreed by beneficiary. The transparent side of the cabinet shall face in the

adequate direction for easy inspection by the user

3.5 Interconnection to the grid

The interconnection to the grid is done in the existing main panel if it can be adapted to house

more devices or in a new additional panel installed besides the existing one.

3.6 Selection and segmentation of the high priority loads

The priority loads will be chosen by the contractor and the purchaser’s representative to meet the

power and energy criteria and, also, the requirements of the facility.

3.7 Installing the electric efficiency set

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The purpose of the electric efficiency set (EES) is to optimize the efficiency and the operation

strategy of the high priority loads. Since there are different types of beneficiary facilities it will

require certain adaptation to the particular needs that shall be approved by the beneficiary.

4. VERIFICATION TESTS

After completing the installation, certain verification and acceptance tests shall be performed

before the PV micro plant enters into operation.

TERMS OF REFERENCE (TOR) DESIGN, SUPPLY AND...

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