science

Photovoltaic system performance

Photovoltaic system performance is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Photovoltaic system performance rather than just read about it. In short: Photovoltaic system performance is a function of the climatic conditions, the equipment used and the system configuration. PV performance can be measured as the ratio of actual solar PV system output vs expected values, the measurement being essential for proper solar PV facility's operation and maintenance.

Key takeaways

Photovoltaic system performance belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Photovoltaic system performance to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Photovoltaic system performance from memory before moving on to harder problems.

Reference excerpt

Photovoltaic system performance is a function of the climatic conditions, the equipment used and the system configuration. PV performance can be measured as the ratio of actual solar PV system output vs expected values, the measurement being essential for proper solar PV facility's operation and maintenance. The primary energy input is the global light irradiance in the plane of the solar arrays, and this in turn is a combination of the direct and the diffuse radiation. The performance is measured by PV monitoring systems, which include a data logging device and often also a weather measurement device (on-site device or an independent weather data source). Photovoltaic performance monitoring systems serve several purposes - they are used to track trends in a single photovoltaic (PV) system, to identify faults in or damage to solar panels and inverters, to compare the performance of a system to design specifications or to compare PV systems at different locations. This range of applications requires various sensors and monitoring systems, adapted to the intended purpose. Specifically, there is a need for both electronic monitoring sensors and independent weather sensing (irradiance, temperature and more) in order to normalize PV facility output expectations. Irradiance sensing is very important for the PV industry and can be classified into two main categories - on-site pyranometers and satellite remote sensing; when onsite pyranometers are not available, regional weather stations are also sometimes utilized, but at lower quality of data; the Industrial IoT-powered sensorless measurement approach has recently evolved as the third option. Sensors and photovoltaic monitoring systems are standardized in IEC 61724-1 and classified into three levels of accuracy, denoted by the letters "A", "B" or "C", or by the labels "High accuracy", "Medium accuracy" and "Basic accuracy". A parameter called the 'performance ratio' has been developed to evaluate the total value of PV system losses.

Principles Photovoltaic system performance is generally dependent on incident irradiance in the plane of the solar panels, the temperature of the solar cells, and the spectrum of the incident light. Furthermore, it is dependent upon the inverter, which typically sets the operating voltage of the system. The voltage and current output of the system changes as lighting, temperature and load conditions change, so there is no specific voltage, current, or wattage at which the system always operates. Hence, system performance varies depending on its architecture (direction and tilt of modules), geographic location and the time of day, weather conditions (amount of solar insolation, cloud cover, temperature), and local disturbances such as shading, soiling, state of charge, and system component availability.

Performance by system type

Solar PV parks

Solar parks of industrial and utility scale may reach high performance figures. In modern solar parks the performance ratio should typically be in excess of 80%. Many solar PV parks utilize advanced performance monitoring solutions, which are supplied by a variety of technology providers.

Distributed solar PV

In rooftop solar systems it typically takes a longer time to identify a malfunction and send a technician, due to lower availability of sufficient photovoltaic system performance monitoring tools and higher costs of human labor. As a result, rooftop solar PV systems typically suffer from lower quality of operation & maintenance and essentially lower levels of system availability and energy output.

Off-grid solar PV

Most off-grid solar PV facilities lack any performance monitoring tools, due to a number of reasons - including monitoring equipment costs, cloud connection availability and O&M availability.

Performance measurement and monitoring

A number of technical solutions exist to provide performance measurement and monitoring for solar photovoltaic installations, differing according to data quality, compatibility with irradiance sensors as well as pricing.

Weather data acquisition Weather data acquisition is generally relying on physical weather sensors and remote sensing with satellites.

Energy generation data availability and quality An essential part of PV system performance evaluation is the availability and the quality of energy generation data. Access to the Internet has allowed a further improvement in energy monitoring and communication. Typically, PV plant data is transmitted via a data logger to a central monitoring portal. Data transmission is dependent on the local cloud connectivity, thus being highly available in OECD countries, but more limited in developed countries. According to Samuel Zhang, vice president of Huawei Smart PV, over 90% of global PV plants will be fully digitalized by 2025.

Performance monitoring In general, monitoring solutions can be classified to inverter manufacturer-provided logger and monitoring software solutions, independent data-logger solutions with custom software and finally agnostic monitoring software-only solutions compatible with different inverters and data-loggers.

Monitoring solutions by inverter manufacturers Dedicated performance monitoring systems are available from a number of vendors. For solar PV systems that use microinverters (panel-level DC to AC conversion), module power data is automatically provided. Some systems allow setting performance alerts that trigger phone/email/text warnings when limits are reached. These solutions provide data for the system owner and/or the installer. Installers are able to remotely monitor multiple installations, and see at-a-glance the status of their entire installed base. All the major inverter manufacturers provide a data acquisition unit - whether a data logger or a direct means of communication with the portal. These solutions have the advantage of providing of a maximum information from the inverter and of supplying it on a local display or transmitting it on the internet, in particular alerts from the inverter itself (temperature overload, loss of connection with a network, etc.). Some of those monitoring solutions are:

Fronius accessible via Solar.web portal; SMA's Webbox/Inverter Manager/Cluster-Controller loggers accessible via Sunnyportal and EnnexOS portals; SolarEdge accessible via SolarEdge Monitoring and MySolarEdge (only application) portals; Sungrow accessible via the iSolarCloud portal;

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Photovoltaic system performance

Start with the simplest possible case. Write down what Photovoltaic system performance claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Photovoltaic system performance before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Photovoltaic system performance ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Photovoltaic system performance

In research: Photovoltaic system performance appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Photovoltaic system performance in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Photovoltaic system performance is common in secondary-school and first-year university syllabi. It links to neighbouring topics Maintenance, Photovoltaics, so understanding it makes those chapters shorter.
In everyday life: Look for Photovoltaic system performance outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Photovoltaic system performance in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Photovoltaic system performance means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Photovoltaic system performance out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Photovoltaic system performance in simple terms?

Why does Photovoltaic system performance matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Photovoltaic system performance?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Photovoltaic system performance.