Once we were chosen we were responsible for progressing the design to RIBA Stage 4, where the Technical Design has been finalised.  To do this we worked in consultation with the client and their professional team to progress the design and this began by combining CIBSE benchmarks with our database of high resolution, real-life heating data to predict the heat demands.  By introducing our database of historical heating data we were able to create more accurate profiles for the new build sections of the development.  For the existing buildings we were able to take the gas usage data to model future energy needs.

We then diversified the data to give us a clear picture of average usage across the site which allowed our designers to begin sizing the major plant.  During this process our designers had to make some important decisions about the sizing of the heat pumps and we worked closely with Star Renewables who were designing and building the heat pumps.

To design water source heat pumps, it is essential to fully understand the water source and for the Queens Quay project this is a tidal, saltwater river which is under the protection of the Scottish Environment Protection Agency and has a range of both plant and aquatic life.  This meant we had to fully acquaint ourselves with the information including:

• Average water temperature
• Seasonal water temperature
• Flow rates
• Wildlife and ecostructure

We began by building a comprehensive picture of the river and how that would affect our design.  The initial stages involved desktop research to map the river’s temperatures throughout the year, establishing that it generally ranges from between 6-12 degrees Celsius.

One of the main hurdles facing our designers was that the heat network would be made up of a mixture of new-build premises and older existing buildings.  The older buildings had been designed for historic heating systems which favour a higher 82°C flow and 71°C degree return and whilst the ammonia based heat pumps are capable of delivering that, the new building’s heating systems are designed specifically for efficient district heating and are based around a 75°C flow and 45°C return.

To create the energy centre we worked with the building contractor to deliver the optimum layout.  One issue was that the building had received planning permission, so we were working with a set building footprint.  Our designers then set out with these restrictions to, not only to create an efficient layout, but also one in which operation and maintenance could be delivered in a safe and efficient manner.

To achieve this we created a mezzanine solution which allowed us to optimise the space available to us.  We then designed the standard energy ventilation to ensure this met all essential legislation, but due to the fact that the heat pump process uses ammonia as a refrigerant we also needed to create an emergency ventilation scheme to ensure it would not harm anyone in the energy centre or further afield.  To do this we created a box which housed the heat exchangers and a ventilation system which led to a 30m flue.  In the unlikely event of a leak the gasses could immediately be expelled into the atmosphere where they would safely disperse.