As part of its Heat and Buildings Strategy1, the UK government wants to increase the proportion of energy from heat networks from 2% to 18% in the next five years.
One of the benefits of this approach is that heat networks can supply both commercial and residential buildings from a range of centralised heat sources – large air source heat pumps; nearby water sources such as rivers; or by using waste heat from data centres, for example.
But are we missing an opportunity to deliver cooling the same way? While much is made of the heating capability of these networks, the cooling element has been largely overlooked in the UK. Interestingly, the UK strategy documents mention networked cooling as an effective way to deliver cooling, however there is no policy directly relating to its wider delivery.
Kings Cross
District cooling works in a similar way to heat networks, moving chilled water through a piped network. Heat exchangers or heat pumps in each building on the network ensure that the building’s cooling requirements are met accurately by modulating the temperature of water provided.
But we are yet to see district cooling used at scale. One example is the district energy centre at Kings Cross2 which provides cooling as well as heating from a central system powered by renewable energy. The shortage of ‘district cooling’ circuits reflects the UK’s colder climate, yet this approach has been successfully adopted in warmer climates such as Dubai and Singapore to support their need for sustainable and energy efficient cooling.
But the UK is getting hotter with an increasing likelihood of heat waves, and we must consider how to tackle rising temperatures not only in workspaces but also homes (particularly the growing number of apartment buildings in major cities). District cooling is low-carbon and energy efficient, with some estimates that it can be up to 50% more efficient than traditional single-building cooling systems.
In any closed circuit that relies on water as the medium for delivering cooling (or heating), water quality is a critical factor for success.
Protecting the energy carrier
It cannot be overstated that water treatment must be considered an integral part of these systems – not an add-on, because of the significant impact water quality has on energy efficiency and long-term system performance.
The science behind this is that by-products of corrosion, scale and biofouling can build up in closed systems, reducing the energy transport characteristics of water. This not only disrupts water flow but also reduces the cooling/heating efficiencies of the system. So, water treatment and filtration directly impact energy efficiency and hence operational carbon emissions from greater energy use.
System optimisation
Enwa has worked on several district heating projects, helping clients protect their systems from these issues. Our EnwaMatic Side Stream water treatment technology is designed to prevent problems before they lead to energy waste or system breakdown.
EnwaMatic Side stream works to remove debris to less than 10 microns. Independent testing shows that suspended solids in treated water are reduced to levels comparable with potable water. It also provides pH regulation, corrosion inhibition and scale control, contributing to a harsh environment for bacterial growth.
District heating and cooling networks are complex and costly to build, requiring a great deal of up-front capital. Water treatment will help to protect this investment, and keep the system optimised for operators and end users.
While the UK may not yet be in need of cooling at scale, that time is coming. The growth of cities and rising UK temperatures point to a future where cooling becomes much more of a critical issue for occupant health at home and work.
Adding cooling to the mix also makes heat networks even more efficient. As the Heat and Buildings Strategy notes: “Depending on their heat source, they can deliver cooling, which means they can be used throughout the year and enable cities to adapt to climate change and the heat island effect.”
This is already being recognised internationally. As the International Energy Agency (IEA) District Heating and Cooling Technology Collaboration Programme3 notes: “DHC has proven to be a major contributor to greenhouse gas reduction in many countries and recognition of its importance is growing.”
A modern approach
As the UK climate changes, we must consider every technology that will help us meet the challenge of rising temperatures, while also achieving our carbon reduction targets. Adding cooling networks to the mix could provide affordable cooling for households and businesses alike. A modern approach to water treatment, supporting robust performance and energy efficiency, will help to achieve that goal.
