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General Idea

The performance of solar photovoltaic (PV) systems can degrade over time, we aim to provide a tool to check the performance. The user fills in as input location and specifications of the system. Our app will then calculates if the performance is acceptable.

We created a web app that allows users to check the status of their solar installations by evaluating if the energy production is at a normal state. Our application aims at providing a quick verification of the monthly energy production of rooftop solar panels. The user will provide the following input:

1. Location of the solar panel: address
2. Size of PV: area in m2
3. Capacity kWp
4. 12 months of production data

The app looks up the estimations from sonnendach, compares the the input with the reference values and returns:

1. Location on map (*)
2. Status: ok or not ok
3. Monthly comparison of actual vs. reference values as a bar chart

(*) - this is currently broken due to CORS (likely), but results1.html still shows is a demo page

Methods and tools

• web app running on AWS S3 (HTML, CSS, JS) and REST interface built on API GW + Lambda (Python 3.6)
• basic statistics
• web-based chart(s) using nv.d3.js

Screens

Working Prototype

First prototype

(1) the user input interface

(2) the output results

Comparison to a test system

We tested our workflow on data from various systems. The following plots shows a comparison between the actual production (measured) of a PV system and the data from sonnendach. As shown below differences vary month to month and amount to 4.53 kWh/m2 is this case.

To determine if the system is not working properly we perform statistical significance tests, assuming that the measurements and reference data from sonnendach are normally distributed. Below an illustration of the concept, showing the relation between measured (i.e. Gesamt-Stromerzeugnung) and sonnendach, with a linear regression and confidence intervals. These intervals and comparisons with neighbours could then be used to flag those months that are significantly outside a reasonable performance.

For the details of the statistical testing see here

Possible extensions

Data

• Allowing automated / continous data input (similar to sonnenertrag.eu). This would enable warnings.
• Historic data of real installations to identifiy the variance and detect outliers
• Collecting feedback of users if the prediction was correct, after they had a professional check. This would allow learning and finetuning the

Frontend

• Bulk check of installations for companies (e.g. utilities)
• Provide adresses for local provessional services to do a detail check
• Gamification: comparing to neighbours / similar PV installations
• Adding estimates on the rentability of the installation (e.g. use http://www.vese.ch/pvtarif/ / https://www.statista.com/statistics/216791/price-for-photovoltaic-cells-and-modules/)

Logic

• Historic comparison. Currently sonnendach only provides the last 12months.
• Adding the age of the installations to take into account the natural degrading of panels (e.g. 0.8% per year)
• Finetuning benchmart algorithm to take into account installation specifics (e.g. paneltype, converter, wirkungsgrad).
• Take into account shading effects of for example trees

Business

• Providing the service as a subscription with warnings

Links Misc

• sonnendach docs
• Map of PV installations
• PV Health check tool
• List of PV installations
• Rentability
• sonnenertrag
• vei
• vei-homeenergy
• solar radiation databases
• PV tarifs

Data

• Ueberlandstrasse 2d, 8953 Dietikon: here

• Test system