District heating with heat pumps- ‘A no-regret option’

A critical pathway to delivering low-carbon heat is revealed in the shift from natural gas to electrified heating systems, and an increasingly decarbonised power grid; heat pumps combined with district heating schemes are set to play a key role in this

There are many reasons why heat pumps have the capacity to underpin district heating and cooling grids and thus make a major contribution to the decarbonisation of heating. They can, for example, employ low-temperature and waste heat sources, facilitate the integration of renewable power in electricity networks, and minimise grid losses.

Furthermore, heat pumps combined with storage systems have the potential to be a key technology in district heating grids because they can balance the grid when the electrical production from intermittent renewable energy sources fluctuates.

The pressing need for more district heating and heat pumps was outlined in a recent decarbonisation progress report from the Climate Change Committee (CCC). It found that the UK Government had made limited headway in its net zero aspirations because of the slow pace of heat pump installations, and the UK must rapidly scale up work to expand the fitting of heat pumps and district heating use.

The CCC said: ‘Progress both on buildings’ decarbonisation and energy supply infrastructure are needed now, rather than waiting a further three years for more complete information – pace should be prioritised over perfection.’

It added: ‘Heat pumps and heat networks are no-regret options in many cases; industry needs encouragement to invest and roll them out at pace.’

So why are these devices not more widespread? According to the International Energy Agency (IEA) allied Heat Pump Centre (HPC), a barrier to the large-scale integration of heat pumps is the high temperature of the existing heat networks, which reduces the efficiency of the heat pumps.

However, it adds an important qualification: ‘The implementation of low-temperature networks helps overcome this barrier at the same time as the heat losses from the grids are reduced.’

Moreover, large-scale heat pumps can increase low-grade heat for efficient and reliable application in district heating systems.

Playing a key role in the energy grid and supply for the future

A landmark HPC report published in late 2019 examines how heat pumps can be implemented in both new and old district heating systems in the best way. It reveals: ‘District heating in general and heat pumps connected to the grids in particular are predicted to play a key role in the energy grid and supply for the future. With the implementation of district heating, it is possible to cover up to 50% of the heating demand in Europe, and heat pumps can deliver around 25% of the energy to the district heating grid.’

The report adds that heat pumps can be a key technology in the future district heating grid in different ways. They can act as a balancing technology when the electrical production fluctuates and phase out fossil fuels from the energy system.

They also make it possible to use low (below 60°C) and ultra-low (below 45°C) temperatures in the district heating grid and minimise grid losses in the district heating grid.

What is the best heat pump arrangement to maximise the effectiveness of district heating schemes?

One answer is the pioneering Engie Refrigeration Spectrum Water supplied by Klima-Therm. This ultra-high- efficiency heat pump is designed for industrial and commercial applications or integration into heat networks and district heating in housing developments.

The 12 models in the series boast nominal heat outputs of 350 to 3,100kW, a condenser leaving water temperature of up to 65°C, and the choice of four refrigerants – R1234ze, R515B, R513A, and R134a.

The Spectrum Water heat pump offers outstanding energy efficiency and superb operational reliability thanks to a combination of innovative components, including oil-free turbo compressors with magnetic bearings, an efficiency-boosting open-flash economiser, and an intelligent Siemens S7 PLC for smart operation.

Among the benefits of the Spectrum are high efficiency due to a unique combination of turbo compressors with magnetic bearing, flooded shell and tube condensers, and the open-flash economiser as standard.

The device also offers reliability – instead of employing a single compressor, overall capacity is split among multiple compressors, which creates redundancies that maximise operational reliability. It features oil-free operation, ensuring stable performance and efficiency throughout the machine’s service life. It also makes for a simple and low-maintenance machine design, as no oil management peripherals are required.