Calculations

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Models have been developed to collate the evidence base for developing planning policy on renewable and low carbon energy,  which :

• Allow data on the existing building stock, future developments, and local resources and constraints to be inputted
• Calculate energy and CO₂ emissions baselines and forecasts, based on a range of scenarios for energy efficiency and energy supply. These calculations are similar to the energy calculations for development control
• Calculate the trajectory that energy and CO₂ emissions will need to follow and provide interim targets, based on input long term targets
• Present results graphically, including a link to GIS mapping tools

Although some standard models are available to process the data and produce figures, including Carbon Descent’s VantagePoint tool and the energy module of EDAW’s Social Infrastructure Framework, each model needs to be customised for a local authority area. A significant amount of work is required to:

• Collect local information
• Ensure the input data is of a high enough quality. This can be challenging, especially where survey data is used
• Develop assumptions on the type of energy efficiency measure, renewable or low carbon energy technology and infrastructure that could be applied in a given area
• Estimate the contribution each measure or technology could make to energy supply or emissions savings
• Interpret the results and develop suitable policies and targets

Calculating the potential contribution from renewable and low carbon technologies for development control purposes can be done by following the general stages set out below.

Task	Notes
1. Estimate baseline energy demand for the development, taking into account any savings from energy efficient design	Benchmarks are available for non-residential (CIBSE TM46) SAP and SBEM are the Building Regulations approved methods for estimating regulated energy demand for dwellings and non-residential buildings respectively. More sophisticated models can also be used. The Code for Sustainable Homes provides a method for estimating unregulated energy use from dwellings CIBSE Guides provide data on unregulated energy use, including site uses such as external lights and communal lifts
2. Convert baseline energy demand to CO2 emissions	The Building Regulations emissions factors can be used to convert energy demand to CO2 emissions. SAP and SBEM do this automatically
3. Identify which technologies are feasible	Consider the issues listed for each technology, including spatial requirements, suitable location, suitable balance of heat and power demand on the site, climate
4. Estimate how much useful energy each feasible technology could supply and emissions they produce	Suppliers will provide data on potential annual output of various technologies - consider how realistic this is, and whether it is maximum possible or a reasonable average Consider when heat and/or power will be generated and how much will be used on site Calculate emissions from any fuel used by the technology, eg biomass, gas for CHP, electricity used for heat pumps
5. Calculate the emissions saved by using each feasible technology	Estimate how much site CO2 emissions could be avoided by using the alternative energy sources. Note – there are special emissions factors for grid electricity use avoided Calculate savings due to each technology as a % of the baseline site CO2 emissions If CHP is used with other renewable energy sources, the % savings from CHP are sometimes calculated first, then the saving s from renewable energy sources are calculated as a % of the remaining emissions from the site after CHP

General guidance on calculations and useful figures available in:

• The Standard Assessment Procedure (SAP)   and the Simplified Building Energy Model (SBEM)
• The Low or Zero Carbon Energy Sources: Strategic Guide, which supports the 2006 edition of Part L of the Building Regulations.
• The London Renewables Toolkit, 2004
• Town and Country Planning Association (TCPA) guide to sustainable energy “Sustainable Energy By Design”, 2006,

The figures calculated for a site should reflect the wording of the policy and targets, ie what renewable and low carbon energy technologies are considered eligible, whether the target is defined as a percentage of energy demand on site or CO₂ emissions, and whether all emissions, or just regulated emissions are taken into account. Any financial data calculated should take into account what information the planning policy requires to be provided to demonstrate viability.

A similar process can be followed to estimate energy demand and emissions and contribution from renewable and low carbon technologies, on a larger scale, for the evidence base for developing planning policy.

There is a choice of bespoke calculator tools or off-the-shelf software to help development control officers make approximate estimates of the potential contribution from renewable and low carbon energy for a given site. There are advantages and disadvantages to each. Some of the issues are set out in the table below.

Bespoke tool	Off-the-shelf software
Eg. Kirklees toolkit	Eg. C-Plan, Carbon Mixer (licence fee) Low Carbon Designer (free)
Content and capabilities tailored to meet specific needs of the users	May not provide all the features or the format that the users require
Requires on-going maintenance to keep it up to date	Some software will be regularly updated
Technical support will need to be provided	Technical support may be offered as part of the package
Initial development cost may be high, but there will not be any limit on number of users	Ongoing licence fees may need to be paid and there may be a limit on number of users

Initial consultation with officers from across Yorkshire and Humber indicated that it would be useful for local authorities throughout the region to adopt a standard tool. It was also viewed as helpful to select a tool which could be used both by applicants to prepare and present the energy strategy proposed for their site and by development control officers to review the proposals and interrogate the figures.Whatever tool is selected, it is important that it is kept up to date and makes use of good quality technical data, and that someone in local authority is trained to use it.