Which heat network is best for your development?
Alan Wilson, Business Development Director at property services business Liberty, discusses how alternative heat sources can help to achieve net zero emissions targets
To meet current emissions targets, analysis suggests we must decarbonise nearly all heat in buildings by 2050.
Heating and hot water in homes accounts for around 15% of the UK's annual carbon footprint.
As a result, the government is investing heavily to develop greener and more sustainable heat sources.
In February, it pledged £40 million towards seven new low-carbon district heat networks across London, Leeds, Liverpool and Bristol. And this is just the beginning.
Replacing fossil-fuelled boilers with renewable alternatives can make a significant contribution to a greener future.
Options to consider when replacing or upgrading plantrooms
When replacing larger heating systems, the logical choice used to be to install a similar system.
However, as many larger commercial size heating systems have a lifespan of more than 20 years, we need to be thinking about low-carbon alternatives now.
At Liberty, we support clients through this process by carrying out in depth options appraisals to help identify the best solution for the unique circumstances.
Ground source heat pumps
Ground source heat pump (GSHP) systems convert energy stored in the ground into heat for heating and hot water production.
Heat pumps are considered a renewable form of energy. Even though they require electricity to operate, they typically have a coefficient of performance (COP) of three or more. That means they produce three to four units of heat for every one unit of electricity used – making them 300-400% efficient.
If they’re powered by 100% renewable electricity, a ground source heat pump can be a zero-carbon form of heating. A heat pump can extract heat from ground water directly (open loop) or from the ground via collector pipes (closed loop) depending on the situation.
GSHPs can be installed as one large communal system or placed in individual homes via a shared ground array.
Heat is delivered to the home in various ways from underfloor heating and radiators to air handling units and chilled beams.
GSHP key considerations
There are several factors that will impact whether a GSHP is feasible. But key is the size of land available.
Some properties situated in dense urban areas may struggle. However, less land is often required that you think. On sites with space constraints, boreholes are more often used.
Where larger amounts of ground space is available, horizontal collectors can be a cheaper alternative.
Air source heat pump
Air source heat pump systems (ASHP) work in the same way as grounds source systems, but they convert energy stored in the air into heat for heating and hot water production.
Electrical heat pumps are considered a renewable form of energy, even though they require electricity to operate. They typically produce 2.5 -3.5 units of heat for every one unit of electricity.
This efficiency does decrease with very low temperatures, which is why they are generally considered to be less efficient than GSHPs in the UK.
ASHP key considerations
ASHP systems generally offer lower installation costs than GSHPs and provide greater installation flexibility. They can be installed individually or as part of larger district or communal systems.
Commercial applications range from community and public buildings through to care homes and offices, hospitals.
Both air source and ground source heat pumps can be eligible for renewable heat incentive (RHI) payments both for domestic and commercial installations.
In commercial situations supplying more than one domestic property, RHI is paid for 20 years based on the amount of renewable heat produced.
This makes them cost-effective compared to non-renewable alternatives over their lifespan.
Combined heat and power (CHP)
As the name suggests, CHP systems generate both heat and power (electricity) by utilising waste heat - usually as steam - to drive a generator creating electricity, which can be used on site or potentially exported.
While CHP systems can run on gas, they are only considered a renewable heating system when run on biomass.
There are various sizes of CHP systems, ranging from single homes to whole districts and towns.
CHP systems are generally considered more appropriate for larger more constant heat demands such as large mixed-use developments, given the variable heat demands between residential and non-residential developments.
Improving communal and heat network efficienciesBuilding Management Systems
Even if you’re not looking to replace your current heating system, there are ways to check your system is running as efficiently as possible, including reviewing your Building Management System (BMS) settings.
Often BMS systems are set when the system is commissioned. Over time either through ad hoc changes or changing uses within the building, the system becomes less efficient.
Install, upgrade or just service your BMS systems to ensure it is operating at maximum efficiency.
Another low-cost solution to reduce heat losses is to apply more insulation particularly where this may be missing parts such as on valves, flanges, filters and fittings.
Utilising wrap around insulation covers means these can be easily maintained by engineers, making them a low-cost and reusable option.Flow return temperatures
Flow and return temperatures can be key indicators of heat network efficiency. This measures water temperate when it leaves the plant room, compared to when it returns.
By being able to reduce your flow and return temperatures and increase your delta T - the difference between flow and return temperatures - you will reduce heat losses throughout the system.
Cooler return pipes will lower heat losses as well as improving the efficiency of boilers, heat pumps and CHPs.
Lower flow and return temperatures can also reduce overheating that can occur due to heat loss from pipework. This can become an issue in well-insulated buildings during summer.
A diagnostic test by an experience engineer is recommended.
Sometimes fixes can be as simple as BMS changes or closing off bypasses ranging to more costly in-built design issues.
However, most older systems - and even some newer ones - will benefit from having this reviewed.
The CIBSE/ADE Heat Networks Code of Practice is a good starting point when address these key issues.
The power to boost the bottom line
When switching from a gas or other fossil fuel systems to an electrical heat pump with a cooling requirement in summer, solar photovoltaics (PV) are worth considering if suitable roof space is available.
Even with feed-in tariffs no longer available, PV systems are extremely economical.
If a PV system provides more energy than is needed, consider adding a battery storage to save surplus electricity for later use or selling it to the National Grid such as through firm frequency response or Capital Market to generate increased revenue.
There is little doubt heat networks are here to stay for many years to come. They are transforming the way we approach commercial and communal developments.
It is a positive step towards a cleaner, greener and sustainable future.