By Simon Wyatt
This year marks 15 years of the Greater London Authority’s (GLA) London Plan. With the new draft Plan coming into force later this year, we have looked back on its impact and forward to assess what’s coming next.
One of the key objectives of the Plan was to deliver carbon reductions, so how has it faired? To measure success, you need to set a target, the GLA chose to use the Building Regulation’s National Calculation Methodology (NCM), the same approach as BREEAM. This was unfortunate as the NCM is designed for compliance and not energy consumption. By using this methodology, the GLA significantly underestimated energy use, sometimes by a factor of three. The recent introduction of the Building Better Partnerships ‘Design for Performance’ standard provides an accurate methodology for predicting operational energy consumption and provides a realistic alternative approach to the NCM methodology adopted by the GLA.
Initially the key requirement of the Plan was for renewable energy generation on site. The easiest and cheapest way to satisfy the requirement was with the inclusion of biomass boilers. But as they resulted in significant increases in air pollution, most biomass boilers were never switched on and were quickly discouraged by the London Boroughs.
Wind turbines were a popular alternative, some even featuring prominently within the architecture of buildings. However, they failed to deliver the estimated electricity outputs due to turbulence air flows around buildings, with some units failing to generate any energy at all. One popular unit, an attractive vertical axis turbine was so ineffective at low wind speeds that electric motors were fitted for appearance sake which then made it difficult to know which way the electricity was flowing.
The focus then shifted to decentralised heat networks fed by low carbon technologies. For practical and financial reasons this meant natural-gas fired combined heat and power (CHP) units was the prevailing solution. Although these are classed as low carbon technologies, they still burn fossil fuels. As a result, electricity generation through combustion had been reintroduced into London after being phased out in the 1980s, due to concerns with local air quality. This led to a contradiction within the planning process whereby the energy officer could be requesting CHP, whilst the environmental officer was requesting its removal.
This has been the status quo for the last five or so years. Apart from a brief attempt from the policy to maximise low carbon heat generation through ‘trigeneration’ onto the market. This meant using heat from the CHP to generate cooling via inefficient absorption chillers. This proved to be technically impractical and was fortunately dropped.
The case for carbon reduction from CHP was based on the large difference between the emission factors of natural gas vs grid electricity. However, since 2010 (the last time the Building regulation emission factors have been updated), the grid average emission factor has halved with the introduction of renewable energy sources. The next version of the Building Regulations is expected to update the electrical emission factor to reflect this, closing this gap and making CHP more carbon intensive then gas boilers or direct electric heating.
The new London Plan will discourage combustion on site, largely due to air quality concerns and from January 2019 requires the use of the new emission factors. The upshot is, that carbon emissions savings of up to 40% from CHP have disappeared, and their contribution to air pollution means that they will be discouraged for new development. The only apparent solution now for achieving the CO2 and air quality requirements are electric heat pumps.
The new Plan still prioritises connection to district heating systems where available and as the majority of the existing ones are supplied by CHPs the conundrum is on how carbon reductions will be achieved.
Looking forward will the forthcoming 2019 version of the London Plan be more successful than previous attempts at achieving its objectives?
- Unfortunately, it has retained the Building Regulation NCM methodology for quantifying carbon emissions and applying carbon offset payments; this bears little relationship to actual performance in use. This may become apparent with the introduction of the new “be seen” policy to report predicted energy consumption vs operational energy data. Adopting the new Building Better Partnerships’ Design for Performance’ standard, would have been a far better methodology to deliver in operation with the performance predicted at design stage.
- Heat pumps certainly on paper offer significant CO2 savings. However, quoted seasonal efficiencies are rarely achieved, since when the heat demand is greatest, the outside temperatures are lowest, therefore reducing efficiencies.
- In terms of CO2 savings, even at the lower efficiencies, heat pumps are better and with the decarbonisation of the grid provide future proofing.
- An area of concern is the fact that electricity is three to five times more expensive than natural gas, which could lead to significantly higher bills. This puts more people at risk of being pushed into fuel poverty.
In conclusion, for the last 15 years, the Plan has been promoting low carbon design with mixed results, but ultimately failing to achieve significant reductions. At the same time, promoting policies which have been detrimental to our air quality. Going forward the GLA has a real opportunity to transmission to a low carbon, fossil fuel free sociality, but now is the time to ensure that the methodology is robust and does not have the unintended consequence of increasing fuel poverty.