Capital idea

Offshore wind turbines may not be the everyday concern of most building engineers but other developments in renewable energy will be very soon. The need to address climate change by reducing emissions of carbon dioxide from fossil fuel use is filtering down through the layers of government policy, national planning policy, Building Regulations and local planning approvals, to finish up on the nation’s buildings? And it is the engineers who must make it work, both efficiently and cost-effectively. While offshore wind farms and tidal schemes catch the headlines and attract large grants, building integrated renewables also feature significantly in current thinking.

By taking a lead through policy, the Mayor of London and the more dynamic London Boroughs will influence the approach to building integrated renewables nationally. Ken Livingstone’s London plan states: ‘The Mayor will, and boroughs should, require major developments to show how the development would generate a proportion of the site’s electricity or heat from renewables, wherever feasible.’

Proposal 13 of The Mayor’s Energy Strategy also says: ‘To contribute to meeting London’s targets for the generation of renewable energy, the Mayor will expect applications referable to him to generate at least 10% of the site’s energy needs (power and heat) from renewable energy on the site where feasible. Boroughs should develop appropriate planning policies to reflect this strategic policy.’

This means that every major development in the London area will require a feasibility study on the use of renewable energy sources within the development which in most cases will be building integrated, before planning permission is granted. The objective is to demonstrate that the carbon emissions from energy use on the site, will be reduced by a minimum of 10% by the on-site renewable sources. Subsequently the approved renewables must be designed and built into the scheme.

The London Borough of Merton already has developments under way incorporating an agreed proportion of renewable energy and the recently published Planning Policy Statement 22: Renewable energy (PPS 22) puts an obligation on planning authorities to ‘…specifically encourage [small scale renewable energy] schemes through positively expressed policies in local development documents.’

The renewable contribution

Faber Maunsell’s sustainable development group has just completed work for London Renewables, the body set up to support the Mayor’s Energy Strategy by facilitating renewable energy in London. London Renewables, match funded by the Department of Trade and Industry, commissioned an implementation methodology for the renewables policy in the London Plan, which will inform supplementary planning guidance on renewable energy – the result is the Renewables Toolkit.

The Toolkit was designed to support planners, developers and others who may have little knowledge of building related renewable energy sources, but who need to make decisions about developments. Planners are unlikely to be experts in renewable energy but need to understand the possibilities for renewables in different developments and to be able to review planning applications they receive. Developers, including clients, financiers and organisations such as registered social landlords, are unlikely to have renewable energy as a core interest but need to understand the best way to provide the required renewables according to their vision and the potential use of the proposed development. Another important objective for the Toolkit was to set down clear definitions, calculation methods and benchmarks so that the different stakeholders were all working to the same set of rules.

In practice the users of the Toolkit are not restricted to planners and developers. The information ranges from general descriptions to detailed calculation methods, gives decision paths and benchmark figures, all of which are usable in feasibility studies and outline designs.

Inside the Toolkit

Work on the Toolkit started by defining in detail certain aspects of the Mayor’s Energy Strategy. First, the measurement unit of energy demand and supply was defined to be kilograms of carbon (kgC) emissions, as this is the unit of measurement now being used by government. Using carbon is the best solution for adding together the impact of different energy sources, gas, oil and electricity for example, to give the total energy demand of the site. Second, the question of what energy demand should be used for the baseload for a development was defined as all the estimated energy demand of the whole development including all building uses, external lighting and any equipment and process demand. Third, the most suitable renewable energy resources for London are identified; seven in total – wind, photovoltaics, solar water heating, biomass combined heat and power, biomass heating, and ground source heating and cooling. Other Mayoral policies deal with energy efficiency measures and things like passive solar design, district heating and cooling, conventional chp and heat recovery. The door is left open for other renewable energy sources, as they may become available, such as hydrogen from renewable sources, gas from anaerobic digestion, solar air heating and micro-hydro.

It is engineers who must make renewable energy policy work, both efficiently and cost-effectively.

Also as part of the Toolkit is the Technology Guide, prefaced by a review of energy efficiency measures applicable to buildings which should be considered first, followed by general descriptions of relevant renewable energies.

The main technical chapter ‘Including renewables in development proposals’ starts with the process or route map and flow diagrams to highlight the major issues to consider for each renewable technology. Next, methods of working out the basic energy demand and carbon emissions of a development are given either using benchmark figures or calculations which can take into account energy conservation measures such as chp, if intended for the development. Benchmark energy figures assembled from standard sources are given for most types of building use classes. And importantly, a method of calculating the net energy contributions of each of the seven renewable sources is given, together with lookup tables of results of calculations for typical developments. There are also sections on working out the cost of the renewable provision and which information on the renewables study should be included in a planning application.

Subsequent chapters look at grants available, how developers cost their development plans, the planning framework relating to renewables, and a list of further information.

As part of the background study for the Toolkit, different development scenarios across London were analysed, from central areas to suburban areas, from flats to prestige offices. These demonstrate which renewable sources are most likely to be appropriate, what proportion of renewable energy they could provide and what it would cost. The resulting analysis tables are also included.

The Toolkit gives guidance on the technical and financial feasibility of the different renewable sources available in urban areas and their use in different types of development. Both energy use and renewable opportunities vary greatly from a prestige central office to a suburban housing development. While the Mayor’s target for 10% renewables in housing can be met easily by solar water heating, in the prestige office, the requirement for cooling energy may be the best use of renewable energy.

In summary…

Good engineering satisfies a need with an efficient, elegant and cost-effective solution. Renewable energy integrated into a development will supply energy at the point of use, normally when it is needed, and without environmental pollution. To do this cost-effectively is a great challenge for the designer since currently most renewable sources do not come cheap. They will be best achieved if designed in from the start, not bolted on the end. The Toolkit gives the general picture with ball park figures on performance and costs. This is fine for the feasibility stage but detailed design requires integration of the source physically into the building and efficient use of the energy in the development or on occasions exported to the grid. One’s thing for certain , engineers face an exciting future.

Simon Burton is an associate director with the sustainable development group at Faber Maunsell. E-mail: simon.burton@fabermaunsell.com

The Toolkit is available on www.london.gov.uk/mayor/environment/energy/london_renew.jsp