In Braunschweig, waste heat is not secondary

Worldwide, the number of data centers continues to grow. As large producers of waste heat (also known as secondary heat), they have become a promising energy resource. Recovery projects using heat networks have already emerged in France and internationally. A pilot project is being rolled out in Braunschweig, Germany.
Published in the dossier of April 2018




Data centers - gigantic sites that host computer data and information systems for businesses and individuals in mainframes and servers - are big producers of so-called waste heat. This energy, from a site whose primary purpose is not heat production, has traditionally been released into the atmosphere it helps to warm. Technological progress in recent years has allowed us to change perspective: from being waste, this energy is now an opportunity. Recovered and stored, it can heat a building or a whole district. This is the challenge being met by Veolia's experiment in Braunschweig, Germany

A data center at the heart of the Heinrich-der-Löwe energy-efficient district

Through its thermal power plant connected to a heating network, BS | ENERGY, a Veolia subsidiary, supplies electricity and heat to residents of Braunschweig, the second largest city in Lower Saxony. In parallel, two decentralized heat networks are being tested, also led by BS | ENERGY..

"On one hand there is the Hungerkamp project, which consists of producing energy from biomass, and on the other hand the ReUseHeat concept, which aims to recover waste heat from data centers. It is about injecting this otherwise lost heat into a decentralized heating network connected to the existing main network," explains Julien Mounier, Veolia's Energy Director in Germany. "As it happens a data center is currently being built in the heart of an innovative energy efficiency district. It’s a great opportunity for Veolia to participate in its development," he continues.

To increase its data processing capacity, the industrial partner acquired 3.6 hectares of land out of the 36 in the future Heinrich-der-Löwe residential and commercial zone, where 600 new homes will have to be supplied with energy. In short, an ideal test site for the European ReUseHeat demonstration project (see box below or see opposite), which aims to promote the recovery of waste heat for district heating purposes.


With ReUseHeat, the European Union recovers waste heat

Data centers represented 4% of global energy consumption in 2015, a figure that is growing by 5% per year (according to RTE). Their cooling systems alone absorb up to 40% of the total energy consumed by a data center. In part, this is the observation that prompted the ReUseHeat program, established by a consortium of 16 partners on four pilot sites: Braunschweig (data center), Nice (wastewater), Madrid (hospital cooling system) and Bucharest (subway station). Launched in 2017 for a four-year period, ReUseHeat is funded by the European Union's Horizon 2020 Energy Efficiency program. The four pilot sites will design the first advanced, modular and replicable system for waste heat recovery and use. The EU has therefore allocated €400,000 for both the development of the EEQ HDL project in Braunschweig and knowledge transfer.

Nothing is lost, everything is transformed

The temperature of the waste heat released by the data center is between 18° and 25°C. A pump pushes it through to the urban network. The temperature is boosted to 70°C with a heat pump for heating the city’s buildings and water. An ecological solution, where even the electricity needed to operate the heat pump is renewable:

"It is designed to optimize power consumption," says Ansgar Böhm, technical director at Veolia in Germany and a ReUseHeat team member.

The system’s flexibility further enhances energy optimization: the heat generated by the data center will cover the basic needs of the district all year round, but connecting it to the traditional central network will make it possible to meet varying heating needs, particularly when consumption peaks in winter.

Test, demonstrate, replicate

The first customers will be connected to this 4th generation district heating network In 2019.
In addition to heat networks, BS | ENERGY manages electricity, drinking water, gas, sewerage and street lighting networks and contributes to fiber optics deployment and electric mobility in Braunschweig. To optimize this next-generation heat network, the company has deployed an innovative monitoring system. The next step is to replicate this solution on other sites...

Braunschweig key figures

Less than 10%: the level of heat loss achieved thanks to low-temperature district heating networks (LTDH), a considerable technical performance
3 km: the length of the heat network that will supply 4.2 GWh to 600 homes annually.
€330,000: the turnover set to be generated by the waste heat recovery for the site