District Heating and Cooling Solutions

It is now beyond doubt that the burning of fossil fuels and the subsequent release of carbon into the atmosphere is heating up the planet. This reliance on fossil fuels has to cease.

The current political instability and volatile trading conditions of these fuels all add emphasis to the fact that we need to find cleaner, smarter, sustainable and affordable ways to heat homes & commercial buildings.

For decades, District Heat networks have been successfully deployed across Europe and are a proven method of providing heat to properties while simultaneously reducing carbon emissions.

The graphs below shows the increasing volume of heat supplied to buildings via Swedish District Heating systems between 1969 and 2015 by heat source type. The second graph shows the change in input fuel during that increase and details the subsequent vast reduction in CO₂ emissions, during that time, despite the increase in output.

There is now an even greater variety of renewable energy sources available and the concept of sector coupling further increases the available energy. But how do we utilise all the various options

District Heating Systems are the great facilitator!

District Heating systems are source agnostic and allow for multiple energy sources to be utilised, sometimes even on the same network. District heating therefore both increases the resilience of heat supply while also creating the opportunity for building owners, councils, towns and cities to reduce their carbon emissions.

What makes District Heating efficient or inefficient

As you would expect, there are multiple things that effect how efficient or inefficient the district network is. Each issue generally comes down to either increasing or decreasing the network delta T. Small delta T’s equal an inefficient network, large delta T’s equal an efficient network. The greater the delta T the lower the flow rate required to supply a given amount of energy. Typically, the flow temperature will be fixed and therefore, lowering the return temperature should be the focus as this will increase the delta T.

At every stage of the design, installation, commissioning and operation, the focus should be on maximising the delta T. If the result of a design change, system change etc. Would be to reduce the delta T, it should be considered very carefully before the change is made.

It should also be noted that reducing the return temperature will allow the majority of renewable sources to provide a greater part of the total output. Solar and heat pumps, for example, will struggle to increase the temperature much beyond 55°C. If the network return is 55°C or above, they cannot provide any energy into the building. Some ‘higher grade’ heat sources producing higher output temperatures can also suffer. CHP for example will struggle to ‘get rid’ of its heat and the engine may shut down regardless of the thermal or electrical demand of the building.

Summary of design considerations to maximise District Heating efficiency: