A new care home for the elderly was commissioned by the RMBI (Royal Masonic Benevolent Institution) at Cramlington, Northumberland in Spring 2007.  The new care home was built in the grounds of the original building at Scarbrough Court, Cramlington and comprised 55 bedrooms together with kitchens, dining rooms, lounge areas, hairdressers, administration and other common rooms.

Due to the higher room temperatures normally required for a care home for the elderly, together with the large quantity of hot water required for washing and laundry, the RMBI required a heating system that reduces the heating bills, reduces carbon emissions and comprised an  integral system of multiple energy sources  in case of a temporary fault with any one individual system. 

To meet the demands of the care home, the following critical factors were identified during the design of the Ground Energy System at Scarbrough Court to ensure the heating system met the requirements of the RMBI:

1.  Back up systems were required to ensure continuity of heat to the elderly residents;

2. The care home uses a large quantity of hot water for baths, showers and laundry;

3. The area and depth of land available for thermal collectors was limited and so an accurate assessment of available sustainable ground energy was required.

To address these critical factors, the decision was made by the RMBI to place a Ground Source Energy System at the heart of the heating supply.  The Ground Energy System comprised three NIBE ground source heat pumps.  Two heat pumps were dedicated to space heating with one dedicated to domestic hot water.  To accompany the Ground Energy System, other systems were integrated.  These were:

1. A gas boiler to boost domestic hot water temperatures required to meet care home regulations.

2. Roof top solar panels to provide domestic hot water.  The solar panels were also used to recharge the ground with excess heat produced in the summer months.

3. Supplementary gas boiler integrated with the ground source heat pumps.

4. Back up electric immersion heater in the unlikely event of temporary fault with both gas boiler and ground source heat pumps.

To ensure the supply of sustainable ground energy to the system, OGI conducted a Ground Energy Resources Assessment (GERA).  This assessment commenced with a desk study to identify the depths of abandoned mineworkings beneath Scarbrough Court.  Once a safe drilling depth was established, a Thermal Response Test (TRT) was conducted by drilling three boreholes to 30m depth. 

In the heating borehole GSB1, a ground loop collector was installed, with thermal sensors placed in the two observation boreholes MB1 and MB2.  A steady 3kW heat supply was introduced to the thermal borehole GSB1, with the temperature rise monitored in the other two boreholes MB1 and MB2.  A back analysis of the observed data produced in-situ values of the thermal conductivity (kW/m°C) and the volumetric heat capacity (kJ/m³°C).

With the thermal properties established, OGI used a mathematical model to assess the sustainability of the thermal borehole collector array, and to optimise the number and spacing of the boreholes. 

OGI’s models were used to ensure an even distribution of heat abstraction over each borehole and also to ensure that the overall thermal array would meet the peak demand of the three heat pumps, which when combined, provided a peak 120kW of heat and hot water to the building.  A model was also developed to asses the long term temperature of the ground to ensure that the abstraction of ground energy could be sustained for at least 50 years.  This model took into account the excess heat recharge to the boreholes from the solar panels and from fluid circulating through near surface collectors during the summer.

To enhance the energy available from the ground, the following was designed into the system:

1. Sufficient ground collectors were installed to match with the peak heat pump output.

2. Thermal recharge of the borehole collectors in the summer from excess heat collected by the roof top solar panels.

3. Collection of heat from near surface collector pipes in the summer and recharge of the deep borehole collectors for later heat recovery in the winter.

4. The integration of the ground source heat pump with a supplementary gas boiler to top-up heat during extreme cold weather.

Since the occupation of the care home by residents in 2008, the Ground Energy System at Scarbrough Court has proved to be extremely reliable and efficient.  During this period, ground   temperatures together with heat supply to the building have been monitored, which has demonstrated that the system is working well within the design parameters.