Delivering the heat
Renewable energy is too valuable a resource to be lost by the distribution system. Neil Young of Uponor UK discusses how to get the most out of renewable heating systems.
In recent years renewable heating technologies have come to the fore as a way of improving energy efficiency, lowering greenhouse emissions and reducing bills. However, these technologies should not be considered in isolation; they form part of a system, and many people continue to underestimate the importance of properly insulated pipework in connecting the system together.
With the cost of fossil fuels seemingly ever increasing, the rise of renewable technologies is providing businesses with an opportunity to cut heating bills and gain financial reward. However, the full potential of a renewable heat source can only be realised if it is installed correctly and used in conjunction with high-quality distribution pipework.
Ground-source heat pumps are one of the simplest ‘fit-and-forget’ solutions for renewable heat. Applied to a building with the right levels of insulation, they are a highly effective way of accessing free heat and transferring it to a property.
A ground-source heat pump is also a perfect accompaniment to a variety of internal heating systems, including traditional manifold and water-based underfloor heating systems. However, in most cases the heat has to travel a significant distance from the heat pump itself to the property. The further the heat has to travel, the more opportunity there is for it to escape. If that happens, clearly the system will become much less efficient. If the heat pump is supplying more than one property, which is not uncommon, the heat has even more of a chance of escaping.
Ground-source heat pumps aren’t the only renewable technology that requires a robust local heat distribution network to work effectively. The use of biomass as a renewable energy source has increased dramatically in the last few years, especially as an energy-efficient, low-carbon way of supplying heat to a site with multiple properties. As such, it will also require a reliable pre-insulated pipe network to ensure that the system operates as efficiently as possible.
Whilst renewable heating technologies are becoming increasingly common, so too are instances of ‘cutting corners’ to keep installation costs down. Given the tough economic climate, it’s understandable that some installers and contractors may be tempted to compromise on quality to win jobs. However, pre-insulated pipework is one area which cannot and must not be compromised.
|To get the best performance from the pre-insulated pipe, the importance of correct installation should not be overlooked|
For a heating system to offer the end-user the most effective and energy-efficient output, it must actually be viewed as a system — not just a collection of parts and products. Pre-insulated pipe is just as important for improving energy efficiency and reducing bills as the heat pump or biomass boiler, and should not be compromised to reduce the installation cost.
As well as the pipes themselves it is important that system accessories are up to standard. Buried joints in district-heating networks have typically been areas for heat loss and to address this, Uponor recently launched a range of improved insulation sets specifically designed to protect buried underground joint areas from heat loss and external forces.
Another consideration with pipe, fittings and accessories is their robustness once installed underground. With the winter of 2013/2014 officially confirmed as the wettest on record, the impact of groundwater and flooding on installed systems can be significant. Water ingress will negatively affect thermal efficiency, so compliance with an evaluation standard such as BRL 5609, which certifies products against leaks from external water, is essential.
To ensure the system is offering the best value both in terms of cost and energy efficiency, the total cost of a pre-insulated pipe (its ‘whole-life cost’) must be taken into account.
There are a number of key characteristics to look for when choosing pre-insulated pipe.
The first is a flexible core pipe, ideally made of cross-liked polyethylene, which is immune to corrosion and encrustation.
The core pipe should be surrounded by closed-cell multi-layer insulation foam, offering flexibility and aging resistance whilst minimising heat losses from the core pipe.
Finally, an outer jacket ideally made of impact-proof polyethylene, to provide flexibility and resistance to burial loads due to its corrugated profile. Ease of installation is also an important consideration, so fittings that do not require the use of welding or specialist tools are a must.
|The secret is in the construction — this is Uponor’s Ecoflex preinsulated pipe.|
To get the best performance from the pre-insulated pipe, the importance of correct installation should not be overlooked. Bedding the pipe in fine-grain sand or pea gravel ensures the outer jacket is protected from stones. It is also important that the outer jacket is robust enough to withstand buried loads. Ideally you would install the strongest pipe available to you to offer the best protection. Uponor, for example, offers a range of pre-insulated pipe which is independently verified to withstand static loads up to 60 t when buried as shallow as half a metre or as deep as six metres Again, systems that use low-quality or improvised insulated pipes are typically not strong enough to withstand these types of load, which cause compression of the insulation foam and subsequent reduction in heat retention properties.
In summary, failing to install properly insulated pipework can negate the energy-saving benefits of renewable heating systems such as those using biomass boilers and heat pumps. Given the Government’s efforts to have 15% of all energy generated from renewable sources by 2020, the market for these types of installations will continue to grow across both domestic and commercial sectors.
End users have the potential to make significant reductions in their energy consumption and bills by switching from fossil fuels to renewable technologies. However, these savings can only be realised in full if the system is used in conjunction with properly insulated and certified pipework from a reputable supplier.
Neil Young is application manager with Uponor UK.