Press release | 2 May 2022 | wrt

Carbon-free energy, every hour of every day

How a 24/7 approach to carbon-free electricity can revolutionize energy markets

Researchers at the Technical University (TU) Berlin are using their open-source software PyPSA to investigate the effects of a new way of tracking and trading green electricity. Here, it is not just an annual quota of electricity from renewable energies that is sold, but hour-by-hour matching of users’ energy consumption with purchases of carbon-free power. While up to now 100 percent green electricity tariffs had to fall back on electricity from fossil sources, especially at night and when there was no wind or in the event of strong peaks in electricity consumption,

a 24/7 carbon-free energy approach matches a user’s energy consumption with purchases of clean energy on an hourly basis. In partnership with Google, the TU Berlin will now use the PyPSA software to run through various scenarios of how a 24/7 carbon-free electricity supply to the Google data centers in Europe could be made possible and what effects this would have on the entire energy system.

Google has been matching 100 percent of its global, annual electricity consumption with purchases of renewable energy since 2017. A number of large corporations, also in Germany, have followed this example. While this approach has been an important step forward for corporate clean energy procurement, it also has limitations. Often, there is simply not enough clean electricity from wind power and photovoltaics available at night to cover the needs of a given company. Nevertheless, electricity does of course come from the socket – and that comes from the mix available at the time on the electric grid, which often includes coal-fired or gas-fired electricity. In previous contracts with electricity providers, these gaps were made up for by producing a lot of green electricity on other, very sunny and windy days, i.e. more than is currently necessary to supply all "100 percent clean electricity” companies on those days. The result is that a company’s clean energy purchases are matched to their consumption on an annual basis, even though at many hours throughout the year there is not sufficient clean energy available on the grid to match their actual energy consumption.

Social aspects of network operation

For this reason, Google, as one of the world's largest buyers of carbon-free electricity, has now set itself the goal of only purchasing electricity from non-fossil sources every day and every hour by 2030. "This 24/7 claim is not only an incentive for the expansion of renewable energies, but also has a social aspect, so to speak," says Prof. Dr. Tom Brown, Head of the Department of Digital Transformation in Energy Systems at the TU Berlin. With the current procedure, wind and solar is not matched to the customer’s consumption and this forces the rest of the power grid to balance the system. “The 24/7 contract approach can support the deployment of clean energy that really matches consumption, supporting the needs of the system overall.”

TU Berlin is to examine the EU market

The PyPSA software developed by Tom Brown and his team is now being used to evaluate the opportunities, benefits, and costs of the 24/7 approach in Europe. It combines global weather data that is relevant for photovoltaics and wind energy with the architecture of the energy grids in the different countries and with the locations where electrical energy can be generated and stored. While Google works with Princeton University and their software solution for the US electricity market, the choice fell on the TU Berlin for Europe. “Google is pleased to collaborate with TU Berlin to explore the benefits of 24/7 carbon-free energy goals for the European electricity system. We are excited to support this important research utilizing the state-of-the-art PyPSA model and drawing on TU Berlin’s many years of experience analyzing the EU electricity market,” says Caroline Golin, Global Head of Energy Markets and Policy at Google.

Just what you need for the energy transition

“What makes PyPSA special is that the code has been optimized for very large networks and long time series. Exactly what you need for simulating the variability of wind and solar,” says Tom Brown. Because PyPSA is open source software, it can be easily adapted to the specific needs of different users. It is also relatively fast: getting an initial overview of the network situation of individual countries takes only a few minutes. A high-resolution simulation for the entire EU, however, takes 12 hours. “We have also designed PyPSA in a particularly user-friendly way with an easy-to-use interface and detailed documentation.”

The last mile will be the most expensive

Whereas Google has been matching 100 percent of its annual electricity consumption with renewable energy since 2017, the company now matches 67 percent of its hourly electricity consumption with clean energy globally. In Germany it will be closer to 80 percent, thanks to a 24/7 contract with the French energy company Engie. However, according to preliminary findings from TU Berlin, getting to 100 percent will be even more challenging. "One of the first results of our modeling is that the step from 80 percent to 100 percent 24/7 share in the purchase of carbon-free electricity is just as expensive as the step from 0 to 80 percent," explains Brown.

What PyPSA Can Answer

The most important questions that the researchers now want to answer with the help of PyPSA are: Which technologies will be particularly helpful on an electricity user’s journey to 100 percent 24/7 carbon-free energy in Europe? Batteries that efficiently store grid power for only hours, or hydrogen technology that can do so for many days and weeks? What role could geothermal energy play in providing dispatchable energy, and what about fossil energy sources that become clean by capturing CO2 (carbon capture)? "We also want to understand the importance of generating power close to Google's data centers and whether computation jobs could be moved between data centers depending on the weather," explains Tom Brown. Because one thing is certain: "Somewhere in Europe the wind is always blowing."

Growing interest in 24/7 carbon-free electricity

There are today more than 65 signatories to the 24/7 Carbon-free Energy Compact, a new coalition organized by the international organization “Sustainable Energy for All” to enable 24/7 carbon-free electricity and accelerate the transition to carbon-free electricity grids. “Institutes, think tanks and network operators have been working with our open source product for several years. Therefore, as word of the benefits of 24/7 spreads further, we anticipate many more studies with PyPSA in this area,” says Brown. One of the interested parties is the grid operator 50Hertz based in Berlin: “As part of the EU’s Energy Track and Trace project, we are already involved in the development of a European industry standard for a 24/7 representation of renewable energies. We are therefore very excited about the results of the Technical University's project. After all, the decarbonisation of industry is one of the most important building blocks for achieving our ambitious national and international climate goals," emphasises Dr Dirk Biermann, Managing Director Markets and System Operations at 50Hertz.

Trading granular certificates

Tom Brown sees the possibility that "24/7 certificates" could be traded on an hourly basis in the future. The industry-led initiative “EnergyTag“ has just released a new international standard for “granular” energy certificates that adds a time stamp to the “renewable energy certificates” in North America and the “guarantees of origin” in Europe, showing the hour or the half-hour in which the electricity was produced. This could also help to certify that electrolytic hydrogen is made with green electricity, which would accelerate the uptake of green hydrogen to decarbonise industry processes.


Prof. Dr.

Thomas William Brown

Organization name Digital Transformation in Energy Systems

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