OPINION RIGHT SOLUTION


James Thonger makes a number of valid points in his


article on combined heat and power (CHP)/district heating (DH) (CIBSE Journal, March, page 55) – such as the importance of including all DH energy uses in any calculation. However, in relation to electricity emission factors, there appears to be confusion between the relative savings of new gas-fired power stations and gas-fired CHP with the actual CO2 savings that CHP will deliver. It is important to understand whether gas-fired CHP is more energy efficient than separate heat and power from gas-fired boilers and gas-fired power stations, so that we can establish the best use of a scarce fossil fuel and reduce CO2 savings. The paper I presented to the CIBSE Technical Symposium last year (December 2011 Journal, page 28) clearly shows that there is still a saving in CO2 compared with gas-fired boilers when the electricity emission factor is


Your views from across the built environment


District heating systems can and are delivering low carbon solutions and should not be dismissed by engineers, argues Paul Woods in response to an article in the Journal


around 400g/kWh – the best that is likely to be achieved from gas- fired combined cycle gas turbine (CCGT) power stations. But when a gas-fired CHP system is installed it will, in practice, deliver greater savings as it will be displacing a mix of power stations, including some coal-fired plant. If James Thonger’s analysis


was correct, then new gas-fired CCGT power stations would not save CO2, which is clearly false given that the main reason we met our Kyoto obligations was the construction of CCGT power stations in the 1990s. Gas-fired CHP benefits from displacing older coal and gas power stations, as does new CCGT plant. His article also discussed the long-term position of gas-fired CHP in a decarbonised grid and suggested that DH networks would become redundant. There will certainly come a point when the use of gas-fired CHP without carbon capture and storage (CCS) should be curtailed at times when


MANUFACTURER’S VIEWPOINT


We should not underestimate the value of social media for our sector, writes Martin Fahey of Mitsubishi Electric


Anyone witnessing last year’s 'Arab Spring' cannot have failed to notice the significance of social media in helping empower individuals and convey a mood swing in popular opinion. Now I am not suggesting we adopt a similar approach to politics here in the UK, nor making any comment on the democratic process, however, the phenomenal influence of Twitter and other social media channels does


16 CIBSE Journal April 2012


highlight how important they can be in engaging anyone and everyone in a debate.


As a central part of the built environment, anyone involved in building services – whether designing, manufacturing, specifying, installing, operating, using or maintaining – can play an important individual role in helping reduce energy consumption. We realised this more than five years ago when we embarked on our


there is surplus wind energy on the system. Initially this will occur at times of low demand and high wind speeds. During these periods the DH network should be supplied either from a thermal store using surplus heat from gas- fired CHP operating at other times, or from an alternative low carbon source. There are many options here for DH – larger networks, for example, could use heat extracted from steam turbines in gas or coal power stations fitted with CCS. Large-scale heat pumps could


also be used. Thonger asks what the benefits might be when compared with using air-source heat pumps (ASHPs) in dwellings. There are several advantages: lower capital costs for the heat pump; the potential for using low-grade heat sources not available to dwellings (the sea, rivers, waste effluent and industrial waste heat); combining heat production with the provision of district cooling; the lower price of electricity supplied in bulk at HV; the ability to use


Green Gateway process, and this has already led to some important carbon reduction milestones for both ourselves and some of the partners and companies we work with. Green Gateway is designed to highlight the discussions we need to be having so that we as an industry can address the triple challenges of fuel poverty, fuel security and emissions targets.


Now we are inviting everyone and anyone to join in the debate on both Twitter and LinkedIn so that we can all promote sustainable thinking. We see this as a straightforward way to generate a lively ongoing debate that involves as many people as possible. Visitors to the Green Gateway LinkedIn group will be able to view


larger-scale, more efficient heat stores to operate at night using off-peak power; and the potential to operate alongside CHP to deliver a smarter grid. Above all, the use of DH will avoid the need to reinforce the local electricity grid to supply the peak power needed for ASHPs. These advantages will need to be sufficient to outweigh the additional heat losses and pumping energy required for DH networks and the likely use of higher supply temperatures from the heat pump. For the next 15 years or so DH networks can be developed using gas-fired CHP systems or local waste to energy or biomass power stations, but in the longer term we will need to adapt to make optimal use of other low carbon heat sources, including heat pumps and, preferably, heat from major power stations fitted with CCS. The locations of new power stations should be planned so that low carbon heat can be readily supplied to DH networks in the future.


the latest thoughts of group members from across the UK building industry and contribute to the on-going discussion. The new Twitter account (@green_gateway) will offer followers a chance to receive up-to-the-minute news and views from those within and outside the industry, including key opinion leaders. We know that no one person or company has all the answers but, as an industry, we do have the technology and the expertise to really make a difference if we can find ways of getting our heads together. Further details on Green Gateway and the company's approach to renewable energy can be found by visiting www.greengateway. mitsubishielectric.co.uk


www.cibsejournal.com


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