Solar DHW avoids complications
The DHW requirements of a school in Derbyshire are met by a combination of solar thermal and continuous-flow water heaters.
The installation at Burbage Primary school at Buxton uses Rinnai continuous-flow gas-fired water heaters with solar thermal for a new stand-alone classroom and facilities block for 75 children, their staff and helpers. The hot water is used for washing hands and utility sinks.
Solar energy is stored in a 500 litre tank so that water preheated by solar energy can be supplied to the Rinnai HD 50i water heater. On a typical days with sunny periods, water could be supplied to the water heater at 45°C and require only a 15 K rise to be delivered to the system at 60°C. For safety, this water is blended at the outlets to 43°C.
Mark Lowe, mechanical design engineer with Derbyshire County Council, says, ‘Any solar input is made use of, even if it is only a few degrees. Also, there is no conflict, as there is with a storage and boiler approach of the boiler pre-empting the solar panels and heating a whole tank of water which then cannot accept any solar contribution.’
