The realities of lower carbon emissions

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A 60% cut in London’s carbon emissions by 2025 — Nicky Gavron, Deputy Mayor of London.
Cities and towns of the future will be markedly different from those of today, according to pictures painted at CIBSE’s national conference last month — driven by efforts to mitigate and adapt to the effects of climate change.As CIBSE’s president David Hughes said at its national conference last month, ‘Everything about the work we are doing is changing. It is a period of immense change. What clients want from buildings now and in the future is very different from even two years ago. We must bridge the gap between these differences.’ One of the key driving factors for change is the threat of climate change and the need to reduce carbon emissions from all sources — including buildings. It was inevitable, therefore, that the main focuses of the conference were the need to reduce carbon emissions, how to reduce them and actual experience and success stories. Putting UK use of energy into perspective, Nicky Gavron, Deputy Mayor of London, told delegates, ‘In the 1950s, we used as much oil in a year as we now do in six weeks!’ She is leading the Mayor of London’s campaign to mitigate the impact of climate change, including the recent launch of the London Climate Change Agency (LCCA). Her portrayal of the challenge is that the level of carbon dioxide in the atmosphere must be stabilised at 450 ppm in only a very few years to avoid run-away climate change. For Nicky Gavron, the Government target of reducing carbon emissions by 60% by 2050 compared with 1990 will be far too late. The target for London is 60% by 2025 — 25 years sooner than the Government target date. Nicky Gavron sees cities such as London having a key role to play in reducing carbon emissions. ‘Half the people of the world live in cities,’ she explained, ‘and 80% of carbon-dioxide emissions are from cities. By 2030, two-thirds of the world’s population will live in cities.’ About 75% of London’s carbon emissions come from buildings and around 25% from transport (ignoring aviation). That is why energy use in buildings is a major focus for the LCCA. Nicky Gavron elaborated. ‘41% of emissions are from existing buildings. Seven million square feet of new commercial space is built each year, but two to three times as much is refurbished — providing major prospects for reducing carbon emissions.’ Central to the LCCA’s policy is mixed-use development and centralised generation of energy. Generating electricity locally avoids transmission losses and enables waste heat to be exploited for both heating and cooling using absorption chillers. Mixed-use developments lend themselves to CHP, with residential and commercial property providing a balanced demand for energy around the clock. Mixed-use development also reduces the need for travel, which could reduce transport emissions by 16%. On-site renewable energy is another LCCA objective, with a target of 20% in the future — but of a lower demand as other energy-saving measures take effect. Current thinking also embraces generating energy from waste, not by incineration but by anaerobic digestion to produce gaseous fuel that could be used by CHP plant — making possible zero-carbon CHP. Sewage waste could also be a source of renewable gas. Delivering Nicky Gavron’s aspirations for London is the task of Allan Jones, chief executive of the LCCA. He is well known for his work in Woking as director of the borough council’s energy and environmental services company Thameswey Ltd. From 1991 to 2004 a range of measures based on decentralised energy generation reduced carbon-dioxide emissions by 77.5% from 1990 levels and Woking having nearly 10% of the UK’s total installed solar photo-voltaics and the first fuel-cell CHP in the UK. Underpinning Allan Jones’s commitment to the local generation of power is the fact that power stations in the UK are responsible for 54% of carbon-dioxide emissions. He explains that the annual thermal efficiency of UK power stations fluctuates around 40% — lower for gas and nuclear and better for gas — and that grid losses are 2% for transmission and 7% for distribution. ‘A third of the power is lost on the way to the consumer,’ he says, ‘more than enough to heat every home in the UK.’ His vision of decentralised energy generation in London is for it to reduce carbon emissions by 20% by 2025 and meet 25% of London’s energy needs. He stresses the importance of trigeneration to provide cooling with far lower carbon emissions than electric cooling and the future potential of gaseous and liquid fuels from renewable sources.
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— The importance of mixed-use developments with decentralised energy generation — Allan Jones, chief executive of the London Climate Change Agency.
Looking to the use of renewable energy, he believes that private wire is the only way to exploit sources such as solar PV. The best use of CHP in trigeneration systems is by mixed-use developments, rather than individual buildings. ‘The energy profiles of mixed-use developments overlap,’ he explains. ‘Mixed-use communities are sustainable communities — combining schools, leisure, residential and commercial.’ Looking further ahead, Allan Jones highlights the need to replace natural gas for powering CHP installations with renewable gas, the use of absorption chillers driven by waste heat and the trading of electricity with other island sites rather than the grid. The first tranche of projects of the energy supply company set up to deliver the vision comprises 11 projects over the next couple of years. representing an investment of £100 million. They will include 170 MW of CHP capacity, doubling the current installed capacity. There will also be an 11 MW wind farm and other sources of renewable energy. Fuel cell CHP is also planned. The overall objective of these projects is to reduce carbon-dioxide emissions by 310 000 t a year. An example of mixed-use development is the regeneration of the Elephant & Castle by Southwark Council, which was described by Tony Moseley. The area covers 39 ha, and the redevelopment, due for completion by 2016, will have treble the floor area of the present site with no increase in carbon emissions. 85% of the total energy requirement of the development will be delivered by CHP plant, representing over 37 000 MWh a year. This gas-fired plant will be augmented by biomass boilers at peak loads. Chilled water from absorption chillers will be made available for air-conditioning systems. Hot- and chilled-water services will be provided by indirect connections to give developers freedom of design. A dual water supply will see non-potable water drawn from boreholes and delivered through separate pipes than potable water. Non-potable water is expected to meet 20 to 30% of demand. Always a popular speaker at this type of event, Dick Bradford, principal designer and energy engineer with Barnsley Metropolitan Borough Council, reminded not a few delegates of how his work will meet the 2050 carbon target by 2010 but also provided an update on his progress by refurbishing coal-fired heating installations to biomass using wood chips and, occasionally, wood pellets and boiler plant for new buildings being fuelled by such biomass Despite having reduced Barnsley MBC’s energy consumption by 20% from 1986 to 1990, Dick Bradford reset his base on which to measure future reductions in energy consumption. The Government’s target for a 20% reduction in energy consumption by 2010 compared with 1990 was achieved during 2001. Nevertheless, Dick Bradford and Barnsley MBC did not sit back, but went on to achieve the 40% target for 2020 during 2005. They are now working on the 60% target for 2050 — and will achieve it within this decade! Not only are carbon emissions being slashed, but so too are fuel costs — with a payback within three years for a new biomass installation in the council’s Westgate Plaza One development compared with gas-fired boilers. The conversion of central boiler plant for blocks of flats from coal to wood chips and the installation of tenant controls and heat meters in each flat has reduced individual heating costs by 50 to 70%, simply because tenants now pay for what they want rather than getting what they had previously paid for. One installation is a works depot with large doors that are normally open. It has a 500 kW wood-chip boiler serving radiant heating panels. Another project is the direct changeover from coal to wood pellets for a boiler in a secondary school. The ratio of fuel to air has been adjusted, and the wood is burned with an efficiency of 86%. Such is the confidence of Dick Bradford in biomass boilers, that a 90kW boiler in a branch library does not have a back-up oil or gas boiler. To meet the Government’s 2050 target, Barnsley MBC still has to reduce its emissions by just 14 000 t a year. That is really no challenge says Dick Bradford, since the council still consumes over 6500 t of solid fuel a year in 133 coal-fired boilers on 66 sites. Just converting that plant to carbon-neutral wood would reduce carbon-dioxide emissions by 15 500 t — exceeding the Government’s target by 10%. By then the council will have reduced its carbon-dioxide emissions by 66% compared with 1990 and 76% compared with 1986. Speakers at the CIBSE national conference who began working on reducing energy consumption before it assumed a high profile on the political agenda have exceeded targets by decades. Such acts should be easy to follow — not hard.
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