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About Carbon Mixing

As Building Regulations tighten on carbon emissions and planning approval increasingly requires new developments to hit renewables targets, the task for designers becomes harder and harder. The process of calculating CO2 emissions for a development is one of:

  • Calculating energy demands (different buildings have different energy demands for heating, cooling, hot water and power for electrical appliances)

  • Selecting energy supply systems, and calculating how much fuel these supply systems will use.

It is the burning of fuel, directly or indirectly (e.g. fuel burnt at a power station in order to generate electricity), that results in CO2 emissions with different fuels producing different quantities of CO2. Whilst this process is not rocket science it requires a methodical approach if it is not to result in confusion.

Consider a mixed use development with a range of building types, each of which have different energy demands. The energy supply strategy for this development could be based around a number of systems including solar hot water, photovoltaic power, ground source heat pumps, and combined heat and power, as well as conventional gas boilers and grid-sourced electricity. These systems will have varying efficiencies which, combined with the type of fuel they use, will result in a wide variety of CO2 emission levels.

Now add in costs for the various system components (both capital and running costs) as well as the cost of fuel and perhaps even the polluting cost of the CO2 emissions, and the calculation of emissions and costs starts to become more complicated.

And these complications really mount up when we want to undertake 'what if?' studies:

  • What if we use ground source heat pumps instead of gas boilers?
  • What if we put wind turbines on the site instead of photovoltaic panels?
  • What if the price of fuel doubles in the next 10 years?

screenshot of original carbon mixer software

Above: Original Carbon Mixer for professionals

The original Carbon Mixer software for professionals, developed by Bobby Gilbert Associates, was designed to make the process of comparing scenarios consistent, reliable and robust. It stores the characteristics of buildings along with the specifications of different heating, cooling, power and renewable energy systems in a database, from which it is easy to mix and match combinations and work out total CO2 emissions and costs. The use of graphs to visually represent data means that users can instantly see how a mix is working, and where strengths and weaknesses lie.

Carbon Mixer is used by architects, developers, energy consultants, and local authorities to provide a clear and transparent language for energy strategies. It is the recommended tool by the 21 local authorities forming the North East Assembly in the UK.