Use case A (Performance Ratio)

String of 12 PV-Modules on standard inverter

Use case

This use case consist of one string having 12 PV-Modules connected to the grid using a standard single phase inverter.

As this is the most basic setup for PV-Blocks it will be simple to configure. We will need to measure the irradiance and the electrical AC output power of the inverter.

Each PV-Blocks system uses the PV-Base pack. We will start the configuration by adding that.

PV-Base pack

The PV-Base pack is the heart of any PV-Blocks system. It is responsible for computing(PV-LINK), power(PV-PSU) and communications(PV-BASE). Without these 3 DIN-rail components a PV-Blocks system cannot be used.

PV-Blocks to use

The PV-PSU is a high quality 24VDC power-supply. It is used to power the PV-Link computer and all connected PVBlocks.

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The PV-LINK is an industrial computer that runs a robust Linux distribution. All measurements are orchestrated by this component. It runs a local database to store up to 10 years of continuous data (depending on the system size), as well as a webserver that can be used to configure the system. The computer can be connected to the internet to access the pvblocks cloud, however it will run perfectly without an active internet connection as well.

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The PV-Base is the communication gateway to all installed PVBlocks.

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To measure the irradiance there are several possibilities. First we have to choose between a pyranometer, a Si-pyranometer and a silicon reference cell. There are several reasons why you would choose one over the other. For now the decision about the irradiance sensor type is left to the user, of course you can contact us directly to help you select the best irradiance sensor.

An irradiance sensor can have an analog or digital output. Both types are supported by PV-Blocks.

Analog Sensors:

An analog irradiance sensor is a device that outputs a voltage that represents the irradiance received by the detector. This voltage is measured and converted to irradiance by the PV-Blocks systems. The PV-Block to use for this is the PV-IRR.

Digital sensors:

Digital sensors have gained popularity over the last years as these are less sensitive for noisy environments. A digital sensor communicates over a digital bus to transfer the measured irradiance. Typically multiple digital irradiance sensors can be connected to one bus. The PV-Blocks system supports many digital irradiance sensors for example the MS80S of EKO Instruments. The PV-Block to use for digital irradiance from EKO Instruments is the PV-MOD-MSXXS.

PV-Blocks to use

The PV Irradiance block is a DIN-rail module that has 4 analog inputs. Each input can measure a voltage between 0-100mV. You can connect any analog sensor directly to this PV-Block.

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This PV-Block enables the measurement of digital irradiance sensors from EKO Instruments (MS40S, MS60S, MS80S). Up to 4 irradiance sensors can be connected to a single PV-MOD-MSXXS.

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For this system we will use a Si-pyranometer(ML-01) from EKO Instruments. As this is an analog sensor, we will have to add a PV-IRR PV-Block to the system. The PV-IRR PV-Block can measure up to 4 analog sensors, but for this use case we will only use one input.

AC Output

The second parameter to measure is the AC output of the system. The AC output can only be measured ‘behind’ the inverter. To measure this AC output, we will use an off-the-shelf electricity meter as there are many precise meters available. PV-Blocks supports 1-phase and 3 phase AC networks. In this use case our inverter generates AC power in a single phase. The AC meter will be a B21-112-100 from ABB. This meter can be directly connected to the PV-MOD-AC PV-Block by means of its digital interface.

ABB AC meter

ABB AC meter

The PV-KWH-1P is a DIN-Rail device that can be mounted inside the grid connection enclosure close to the inverter. It will measure the generated AC power continuously. The meter is an ABB B21-112-100.

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This PV-Block communicates directly to AC electricity meters that support the RS485 interface.

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We will add the PV-MOD and PV-KWH-1P electricity meter to the system:

The resulting system to measure the Performance Ratio is now ready to install. It has a PV-BASE pack, a PV-IRR and a PV-MOD-AC.

Web interface

The operator can setup the PV-Blocks system by means of an ethernet connection using any web browser. Setting up the system in completely handled by the internal webserver. The PV-Blocks system runs standalone and does not need any maintenance besides a regular backup. The measured values are stored locally on the internal computer. Depending on the amount of PV-Blocks connected, about 10 years of data can be stored locally. Measured data can be downloaded from the web-interface directly.

Application Programming Interface (API)

The PV-Blocks system is completely open to developers by means of an extensive API. Developer can create their own programs to retrieve the data and analyze it in any possible way. An example python script is included with the system that should help a developer to get started.

PV-Blocks Cloud

You can use the PV-Blocks cloud to off-load all data automatically online. Dashboards (Grafana) can be build directly and shown to any audience. Of course the cloud solution complies to the highest security standards.