Heat Networks The Future or the Past?

The introduction of heat networks into new building projects on urban sites has become a de facto standard in London. Heat networks cost about £1-3,000 per metre, depending on location, so using them to link bungalows doesn’t make sense, using them to link multi-storey urban buildings does. GLA guidance is very clear: Policy 4A.5 states that ‘Boroughs…should maximise the opportunities for providing new networks that are supplied by decentralised energy … [and]ensure that all new development is designed to connect to the heating and cooling network’.  The accepted truth is that heat networks systems are a cost-effective way of meeting carbon reduction targets. Is this really the case?

Some pros and cons are outlined below

Lifecycle cost: Typically heat networks cost more than individual installations, but they last much longer, so over a twenty five year period where boilers will be replaced twice, a heat network is cheaper to install. But in most cases, the heat network is installed by a developer and the building tenant or eventual owner is not part of the discussion.

Physical Network:  Like any network, heat networks have to be well designed to work and there are not that many people in the UK that have experience of designing and installing them. Consequently there are a number of reports of problems from building owners. Overheating in common areas is a particular issue caused by poor insulation of pipework and overcirculation of hot water.

Heat Delivery:  Heat networks need a system for delivering the heat into the dwelling. This is usually a heat exchanger  about the size of a combi boiler and needs to be sited close to the network for easy access to maintenance.

Management:  Many housing associations are put off by heat networks because of concern about maintaining a system that is unfamiliar. Many of the companies that design and install these systems can also maintain them and manage the complex billing systems that are required to ensure that residents only pay for the heat that they use. A reason that many of these heat networks were removed from housing estates in the eighties is that they were poorly managed by local authorities and usually did not meter the heat to individual users.

Costs to Users: This is one of the trickiest areas. When heat networks are installed, someone needs to pay for it, This is usually dealt with by adding a service charge to bills of the users of the system. This is a relatively small amount but pays back the installer over a long period.  The heat user pays no upfront cost, but their bill is larger.

CO2 reductions: This is an even trickier area.  Heat networks lose a proportion of their heat through the network; this can be up to 50%. So any calculations of CO2 emissions must take this into account. Compared to individual boilers there is no reason to use communal systems  for CO2 reductions unless part of the heat is going to be supplied by a CHP engine. CHP uses the spare heat produced by generating electricity to boost the efficiency way above what can be achieved with a boiler only model. A typical CHP system saves about 60% CO2 compared to a conventional boiler. If the CHP can be fuelled by renewable fuel, then the savings are over 100% because the electricity offsets electricity produced from the grid. But renewably fuelled CHP systems are barely a glint in the eye of system manufacturers so treat with caution.

Density:  Heat networks cost about £1,000 per metre, so using them to link bungalows doesn’t make sense, using them to link multi-storey urban buildings does.

The Big Issue: A strategic problem with heat networks is that there is a plan to reduce their business case by about 50% over the next thirty years, this is called the Green Deal. We need to reduce our heating demand by this much if we are to have any chance at reducing our CO2 emissions from heating systems. Heat networks provide a flexible mechanism for delivering heat, but if they don’t need to deliver so much heat, are they worth the effort, and would our investment be better directed elsewhere?

This article was first published in the AJ

http://www.architectsjournal.co.uk/sustainability/footprint-heat-networks/8616912.article

See here for the AJ Sustainability blog:

http://blog.emap.com/footprint/2011/07/01/footprint-in-the-aj-the-pros-and-cons-of-district-heating-networks/

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