• Antonios Chrysopoulos

How utilities can help prosumers monitor their solar production

Renewables Market Development

Due to the increasingly serious energy crisis and environmental pollution, the utilization of renewable energy resources have become the only viable solution for ensuring secure and sustainable energy supply. In recent years, the installed capacities of renewable generations such as wind power and photovoltaic are rapidly increasing, transforming the power generating resources from predominantly fossil power generation to high penetration of renewable generations [ref].

Wind and solar photovoltaic technologies are expected to continue their growth trajectory as generation costs involved with these sources are becoming more competitive, thereby encouraging more projects and customers to be set up in the coming years. The emergence of newer markets will further drive uptake for wind and solar energy sources, as it can be seen in the following graph [ref].

In recent years, it is commonplace in most developed countries under the Paris Agreement for the governments to provide subsidy incentives on consumer solar installations, so that countries and social housing corporation solar installations meet their CO2 reduction targets. Thus, it has become more and more attractive to environmentally sensitive customers to become prosumers of electric energy (consumer + producers) by installing photovoltaic panels on their roofs or gardens.

How Photovoltaic (PV) Panels Work [ref]

A PV module is an assembly of photovoltaic cells mounted in a framework for installation. Solar PV cells are made from layers of semiconducting material, usually silicon. Photovoltaic cells use sunlight as a source of energy and generate direct current electricity. More specifically, when light shines on the material, electrons are knocked loose, creating a flow of electricity.

A collection of PV modules is called a PV Panel, and a system of Panels is an Array. Arrays of a photovoltaic system supply solar electricity to electrical equipment. Modules and arrays come in a variety of shapes and sizes. Most PV systems are made up of panels that fit on top of the roof, but they can also be installed on the ground, or fit solar tiles.

The electricity generated is direct current (DC), whereas the electricity used for household appliances is alternating current (AC). An inverter is installed along with the system to convert DC electricity to AC.

There are several major factors that affect the Solar Production of the installed PV module:

1. The quality and the capacity of the installed solar panel/array. As it is natural, the larger the capacity of the installation, the more electricity is going to be produced. However, important roles also play the material and the connection of the photo-voltaic cells.

2. The weather conditions. The cells don’t need direct sunlight to work, they can work on a cloudy day. However, the stronger the sunshine, the more electricity generated.

3. The photovoltaic panel’s pitch angle towards the sun. The roof space should ideally face south, unshaded, and at a pitch angle of about 30 or 40 degrees. East- or west-facing roofs could still be considered, but north-facing roofs are not recommended.

4. The surrounding environment. Any nearby buildings, trees or chimneys may be potential objects that could shade the area that the PV module is installed, which will have a negative impact on the performance of the system.

The added benefits for a prosumer that has an PV module installed are the following:

1. Cutting electricity bills. Even though the installation of a photovoltaic module/array installation requires an initial capital, this investment will reduce the electricity costs significantly. One is able to find out how much you could save by using the Solar Energy Calculator.

2. Cut your carbon footprint. Solar electricity is green renewable energy and doesn't release any harmful carbon dioxide or other pollutants. A typical residential solar PV system could save around 1.3 to 1.6 tonnes of carbon per year.

3. Worthwhile Investment. The installation of a photovoltaic panel is one of the main contributors for improving your housing energy label, which leads to an increase in the value of your home. Additionally, in most countries, there are net metering and tax incentives towards that direction, paying a portion of the initial investment. To this end, investing in solar is much more attractive than having money on your savings account.

Daily Solar Production Examples

We have gathered a few example figures of solar production from different types of days, in order to provide an overview of real-life production cases. For presentation purposes, an installation in Central Europe with a solar capacity of 2000 Watts was selected.

  • Spring day, with no clouds

  • No residents present

  • Daily Solar Production: 14 kWh

  • Peak production: appr. 1600W

  • Summer day, with clouds

  • Heavy appliance usage during daylight hours

  • Daily Solar Production: 11 kWh

  • Peak production: appr. 2000W

  • Cloudy Winter day

  • Heavy usage of appliances during daylight hours

  • Daily Solar Production: 2 kWh

  • Peak production: appr. 400W

Contribution - Solar Production Monitoring Cases

As mentioned above, it is important for a customer that has invested in a solar panel installation to be able to monitor his/her solar production on a daily basis or even in real time. Having this information available enables (a) better comprehension on how and when the installed solar panel functions and produces energy, and (b) taking preliminary actions against maintenance or installation problems that may arise in the future, based on the metrics of historical efficiency of the installed panels.

In case an energy service company wants to provide information about solar production to its customers, there are actually three ways that allow for solar production monitoring, each one having its pros and cons:

· Retrieving information from the Inverter using Software. Most of the solar panel providers are willing to provide (near) real-time measurements from the solar panel production. The most common information provided is the solar production level (in Watts) at a 1/10/15 minutes granularity. However, in order to retrieve this kind of information, a software connection with the API of the installed inverter needs to be implemented. The good thing about this service is that you have a very accurate depiction of the actual solar production. On the other hand, there are too many models and types of inverters out there, each one having its own API / App, making it near impossible to create a unified approach to retrieve data information from all of them. Also, the time granularity plays an important role in removing the solar production time series, in order to retrieve the actual consumption time series of the installation.

· Installing a second metering equipment. In this case, another metering equipment has to be installed directly in the solar panel inverter, providing information in real time. This case is perfectly accurate, since the metering equipment retrieves only the solar production measurements and the time granularity is controlled from the metering equipment, which in most smart metering equipment is 1 second. However, as it is obvious, this solution is more intrusive and costly than the first one.

· Implement a software solution on the Analytics side. The final approach for extracting useful information from the solar panels is to create a smart service that is capable of extracting the solar production time series using the NET consumption measurements available from the main smart metering equipment. This is a non-intrusive approach, without any additional cost on the customer side. The only drawback is that the results may not be perfectly accurate, since the prediction error is dependent on the quality of the implemented smart solution and the retrieved data measurements.

NET2GRID Solar Production Services

At NET2GRID, we made the strategic decision to go with the third approach. To this end, we have implemented an intelligent, non-intrusive, inverter-agnostic service which provides an overview of an installation’s solar production on a daily basis in a very cost-efficient way. Our approach utilizes a number of state-of-the-art AI techniques in order to estimate the actual solar production time series, without using additional metering equipment or utilizing the inverters’ API, while at the same time resulting in a mean accuracy of 90% on our solar production predictions. Additionally, we are supporting solar production on a total installation level, meaning that the approach is independent of the amount of installed panel capacity or having multiple different brands of inverters (apps) being installed over time, since, lately, it is really common for people to continuously extend their solar investment.

Our algorithm utilizes the following inputs:

1. The installation’s Net daily total consumption time series (the Net time series of an installation represents the overall time series as it is retrieved from the Grid, meaning the time series that can be acquired by subtracting the solar production from the total consumption of the installation), as it is retrieved from the smart meter equipment of the installation, in 1-second granularity. In case of a three-phase installation, providing all three phases can make the algorithm more robust and accurate.

2. (Optional) The weather conditions that are present at the time of analysis. More specifically, our approach utilizes measurements from Solar Irradiance, Temperature, Cloud Coverage, in case they are available.

3. (Optional) The historical values of the solar production time series from days that have presented similar weather conditions in the past month.

In order to estimate the solar production time series as accurately as possible, the following steps are applied on the inputs:

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