“Closing the Loop” with heat recovery

Reuse of resources and renewable energy are obvious choices for H&M

Global fashion brand H&M has been an Öppen Fjärrvärme supplier from when the initiative was launched in 2013. The company was one of the first to join when Stockholm Exergi invited data center operators to collaborate on developing a new concept for recovering excess heat.

Reusing resources and using renewable energy is part of H&M’s business strategy. For example, H&M was first among multinational companies to launch a global program to collect used clothes for recycling. Based on this initiative, in 2014 H&M launched its first recycled fashion collection. Today, new denim items that are made from material from collected garments are available to buy in their stores.

H&M is now present in 59 countries. As the company continues to grow globally, its online turnover is increasing and expanding in markets outside Europe and the US. As a leading international fashion company, with one of the EU’s most valuable retail brands, it has been critical for the company’s commercial and strategic success to develop a reliable, efficient, and sustainable information and communication technology (ICT) infrastructure.

Reducing the company’s environmental impact: a top priority

Reliable power supply and competitive prices for renewables is what has driven H&M to continue to consolidate its data centers in Sweden. The country’s outdoor climate also offers favorable conditions to use technologies such as free cooling and heat recovery.

In 2010, H&M opened a new global data center in Stockholm. The facility is designed for the long-term in terms of efficiency and sustainability. Reducing the company’s environmental impact and successfully “closing the loop” are two of H&M’s top priorities.

The data center only uses electricity produced from renewable sources and consumes lower amounts of power than in the past. This is partly due to a focus on achieving higher utilization rates, improved spatial planning, more energy efficient hardware, and cooling with a combination of free cooling and heat recovery. Furthermore, H&M continually monitors and optimizes operations at the facility.

During the first two years that the data center was operating, 2011-2012, it was exclusively cooled by a local cooling system. Cooling coils in the computer room are cooled with cold water, which circulates in a closed system. Using heat exchange, the cooling water system is cooled by an external loop that is connected to cooling towers, located outside. The two cooling towers thereby provide free cooling throughout much of a typical year in Stockholm.

An Öppen Fjärrvärme supplier since 2013

H&M was one of the very first companies to join Öppen Fjärrvärme in 2013. Through its co-operation with Stockholm Exergi, its cooling system at the data center was fitted with a connection to the district heating network. This enables the data center to recover excess heat on days when the ambient outside temperature falls below 7°C. This amounts to some 4,300 hours in a typical year.

Furthermore, the new installation and the agreement with Öppen Fjärrvärme now means that the data center has an extra cooling option, available as a reserve during the remaining hours of the year.

It was straightforward to connect H&M’s facility to Öppen Fjärrvärme. The existing cooling loop was connected to a heat exchanger and a circulation pump at the same time. The other side of the heat exchanger was connected directly to Stockholm Exergi’s district heating network.

Cooling of the data center now allows cooling water to be heated to a temperature of 20°C before excess energy is transferred to Stockholm Exergi’s system and transported to a large heat recovery plant in Hjorthagen, just outside central Stockholm. With help of four large heat pumps that have a combined recovery capacity of 24MW, the temperature of returned heat from the data center is increased to an intermediate level, prior to being mixed with high temperature water from the Hjorthagen plant’s cogeneration process for distribution to district heating customers.

Between 2013 and 2015, the data center’s load has virtually doubled. H&M is now able to recover energy and make annual deliveries of up to 1,700MWh in heat to Stockholm Exergi’s network. This amounts to the heat use of some 350 Stockholm inhabitants.

After several years’ experience of heat recovery at the data center, in 2017 H&M decided that their next data center, slated to go online in 2018, would also recover heat. For this data center, H&M is investing in an installation where they generate data center cooling themselves with heat pumps in a redundant N+1 solution and deliver excess heat directly to Stockholm Exergis district heating network. Under this model, Stockholm Exergi pays for capacity (kW) and energy (kWh) dependent upon outside temperatures. The data center is scheduled to have an IT capacity of 1MW, and projected to be able to heat some 2,500 modern apartments.