HEATING SYSTEMS ENERGY EFFICIENCY
designers should look ‘to optimise the network and use existing structures’ such as tunnels and car parks, to transmit the heat to where it was needed. ‘Look closely at the energy density to
make sure it makes financial sense,’ said Woodward. ‘There will be heat losses, but these can be minimised through good design.’ He also urged system designers and
operators to resist the temptation to ‘pump water around at 130C’, and instead look to run the system at as low a temperature as possible. The risk of building ‘white elephants’ to
take advantage of government subsidies has increased in recent years, but Woodward called for the industry to take responsibility for developing robust business cases for all proposed plants. He added that end-users should not be
forced to pay more for ‘green’ energy. ‘Avoid the cost-recovery model. Connecting to a district scheme should not be at a green premium – it should not cost the user more than if they had their own individual scheme. There must always be a business case.’ The financial model for ground-source
The photovoltaic solar panels are often not providing heat when it is needed WHAT THEY SAID....
It is relatively easy to cut carbon by using lots of clean energy, but that is no longer acceptable as it dramatically pushes up costs
Controls are critical because, too often, systems have been found working back to front so the panels release heat into the atmosphere
Clients are now buying the performance, not the products, and the Green Deal is putting this into a financial context
If electricity is decarbonised, embodied carbon would become 50% more significant for a typical office
The key factor for a ground-source heat pump is seasonal CoP over the heat pump’s life cycle
Thermal storage using ice or phase-change materials is a good application for renewables that often provide energy when you don’t need it
34 CIBSE Journal February 2012
heat pumps (GSHP) is also improving, according to Brian Mark of Mott Macdonald. However, he criticised manufacturers for quoting very high and misleading coefficient of performance (CoP) figures. ‘The key factor is seasonal CoP over the
heat pump’s lifecycle,’ said Mark. ‘If this is good, reduced carbon emissions will follow, but then you should check the cost/benefit model to make sure it is appropriate.’ Energy Savings Trust field trials had
revealed that none of the installations had a higher COP than 2.5. ‘This means none were as good as just burning gas,’ said Mark. ‘Advanced applications could achieve more than 5 for heating and up to 20 for cooling,’ he claimed. ‘The RHI is wrestling with this. If you get
the calculations wrong, you could get tariff payments for a while, but then find they have been taken away again.’ The industry average CoP for GSHP is
just 2.3; yet, unless it is over 2.6, it can’t be classified as renewable, according to Mark. And this will not improve until installers understand system design better, he said. ‘Ground-source systems must be
combined with the lowest possible temperature heating system. There is not much wrong with the technology; it is how it is applied that has been the problem.’ CJ
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