Methods

An important part of Mark Barrett's expertise is in the development and application of computer models and databases. These models are used to carry out quantitative analysis of technical, economic and environmental features of policies in certain sectors. Typically the models are used to construct strategies for meeting environmental objectives at some future date.

The models generally employ two basic methods:

- Simulation of system behaviour over time - from hours to years.

- Optimisation to achieve environmental and energy goals at least cost. A range of optimisation techniques is used including downhill stepping and genetic algorithms. Generally, optimisation approaches are tailored to the problem in hand. This has the advantage of efficiency, and the optimisers can be used without purchasing proprietary software. Examples of optimisation may be found in the section on energy models.

In addition, Mark Barrett has developed a general optimisation package (called MultiOptimiser) for application to spreadsheets.

A simple animated example is given of MultiOptimiser applied to a building. The optimiser finds the minimum cost design for a building wtih a required volume and given costs of fuel and energy technologies. The optimiser alters building dimensions, U-values, air change rates and heating system efficiencies (heat pump if greater than 100%) to find a least cost design. Two cases are presented: optimum designs with fuel costs of £5/GJ and £10/GJ.

The models are generally written in Microsoft Visual Basic for Applications in an Excel environment. Large databases are held in Microsoft Access.