Guardbridge geothermal technology demonstrator project: feasibility report

9. Energy Centre Design

The proposed well location is principally selected to target the potential geothermal resource and is located witihn the Guardbridge Energy Centre on the former papermill site. The well head, heat pump and heat station are indicated on Figure 8.1.

The proposed geothermal heat resource will provide baseload supply to the network with back-up capacity provided by the biomass energy centre which is under construction (Fig. 9.1). It may be feasible to extract heat from the return of the district heating main pipes connecting the Guardbridge Energy Centre to the North Haugh in St Andrews. This will depend on a number of factors including:

• The biomass boiler specification for feedwater;
• The temperature specification for the customers on the network;
• The return temperature in the network main.

The development trajectory for the proposed development of the site is indicated in Table 5.2 - 5.4; the heat demand will develop over time and it may be appropriate to delay investment in the geothermal well until baseload demand can be guaranteed. The availability of heat from the biomass energy centre allows the network to be developed in the interim period.

The system indicated in Figure 9.1 shows the heat pump providing baseload and operating in parallel with the thermal store and the back-up heat supply from the biomass energy centre. The heat exchanger between the geothermal energy centre and the network will provide hydraulic separation of the systems and allows the control of system temperatures to the Guardbridge site which will operate on a lower flow and return temperature than the main district heating network.

Fig. 9.1: Proposed geothermal energy centre design with backup connection from the Guardbridge Biomass Network.

The geothermal well capacity has been demonstrated above to be limited to approximately 418 kW and the total annual demand on the network in the technical and economic model assumes that the annual load dispatch from the plants will follow the figures indicated in Table 9.1.

Table 9.1: Load dispatch used in energy model

9.1 Combined heating and cooling operation

Figure 9.2 and 9.3 below demonstrate an enhanced system configuration that could be considered at a subsequent stage to provide combined heating and cooling for the site. This would increase the utilisation of the heat pump by operating in combined heating and cooling mode during inter-seasonal periods. The system could also potentially be used to fill separate hot and cold seasonal heat stores. The technical and economic feasibility is not explored further at this stage, but will be worthy of consideration if this project is taken forward.

Fig. 9.2: Summer operation for potential seasonal storage.

Fig. 9.3: Winter operation for potential seasonal storage.