FEATURE HVAC The future of energy is in district heating

Steve Richmond, head of marketing and technical at Rehau’s Building Solutions division, discusses what companies are producing to drive the latest generation of district heating solutions in today’s energy market


he Committee for Climate Change (CCC) published a report in February

2019 with suggestions for reducing emissions worldwide, resulting in the government unveiling legislation for achieving net zero carbon emissions by 2050. This move also coincided with the establishment of the Future Homes Standard for 2025, which bans the installation of fossil fuel boilers in newbuild homes. Developers are now looking at

alternatives, such as heat pumps, supplying a district heating network. Indeed, the tenth version of the Standard Assessment Procedure for building regulations (SAP 10) consultation states that an emissions factor for electricity value of 0.233 kgCO2/kWH should be used, as opposed to the current SAP 2012 value of 0.519. Since this initial consultation, the Draft SAP 10.1 consultation, published in October 2019, has proposed an even lower value of 0.136 - a 75 per cent improvement from the SAP 2012 figures for electricity- derived carbon savings from heat pump usage. This was published alongside new Part L and F Building Regulations which are due to come into force in 2020 and define minimum carbon reductions. In addition, when awarding their grants

and loans from the UK government, the Heat Networks Investment Project (HNIP) favours projects that use these types of centralised commercial-scale heat pumps and very low or ambient temperature distribution systems.

FOURTH GENERATION District heating networks supply heat from a central heat source via a network of underground pre-insulated pipes. In terms of energy efficiency, supplying multiple buildings from one heat source reduces carbon emissions, while eliminating the need for individual maintenance and its ensuing costs. Most current district heating networks in

operation are third-generation, typically using fossil fuels to circulate water at 70-95o

C. To help meet the UK’s carbon

reduction targets, district heating systems are best used in conjunction with a renewable or waste heat source. Developers must ensure new heat networks do not exceed 70o

C flow temperature according to CIBSE / ADE CP1 16 WINTER 2019 | ENERGY MANAGEMENT Rehau 

– the code of practice setting out minimum requirements for heat networks. Suited to the lower flow temperatures C, the latest fourth generation

of 40-60o

district heating networks often use centralised air, water or ground source heat pumps or waste heat, meaning carbon emissions are significantly reduced compared to fossil fuel networks. The lower heat losses along with a more energy efficient heat source mean district heating networks can satisfy consumer demand in both an environmentally friendly and energy efficient way. Reductions in heat losses from lower

flow temperatures, smaller pipe sizes, and the resulting reduced capital and operational costs, have made the fourth generation technology the preferred choice of key developers. Improved energy efficiency and emissions rates, along with lower installation and maintenance costs also mean district heating systems deliver on the government’s demands for net zero emissions, as well as lower energy bills.

POLYMER PIPEWORK A growing preference for cost effective and energy efficient district heating networks has resulted in increased demand for modern, efficient systems, particularly those that use polymer pipework. To meet consumer, government and developer demand, companies such as Rehau are developing district heating solutions that help lower emissions and capital costs. Rauvitherm and Rauthermex,

pre-insulated pipework solutions from Rehau, are both reliable polymer solutions

for use in district heating networks. Combining flexibility and low heat losses, Rauvitherm is an ideal option for small-medium size heat networks or house connections from a main spine. For larger networks, the insulation afforded by the high performance polyurethane rigid (PUR) foam used in Rauthermex ensures minimal heat losses and enhances system efficiency across the network. Additionally, polymer pipework removes

the need for costly system failure and repair work that can derive from corrosion associated with its traditional steel counterpart. The lower flow temperature of a fourth generation network allows for a lifespan well in excess of 50 years for polymer pipes. Quick and easy installation with no need for welding also affords developers and contractors flexibility throughout both the design and onsite construction processes. With the implementation of polymer

solutions, developers, specifiers and contractors can keep up with the rapidly changing market, that is moving toward lower temperature, energy efficient renewable heat networks. Following the drive to reduce carbon from government policy and changing regulations, heating our homes and buildings with efficient district heating networks has become an even more viable option.

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