When faced with a large number of buildings and heavy energy usage on Edinburgh university’s campus at George Square, energy manager David Somervell set to work.
And over the past two decades he has helped the university develop Combined Heat and Power (CHP) plants, which use natural gas to provide the varying electricity and heat demand of lecture rooms, laboratories, student accommodation and all educational facilities.
The George Square campus has its own 1.6 MW gas-fired CHP engine, two 6 MW and one 3 MW low-temperature hot water boilers, a 600kW absorption chiller, and a 75 cu m thermal store, along with the insulated piping and private wire electricity network necessary to distribute energy to their buildings.
Heating, chilling and electricity supply are all handled by the installation. The university buys natural gas, and uses a large engine coupled with variable speed drives to produce both heat and electricity with over 80% efficiency, more than double traditional coal-fired power station.
The electricity output is used as it is generated, and the hot water is either pumped direct to buildings around the plant to provide heating and hot water or stored in an accumulator.
Once the heating and power needs are met, any additional heat is employed in an absorption chiller, which is largely used to cool the servers in the university’s new Informatics Block.
David Somervell said that the installation is like a mini-power station where all the outputs are used to their maximum benefit. The university’s system remains linked to the electricity grid, so there is always back-up power available too.
Gas boilers are held in reserve to cut-in and provide heat when, during periods of cold weather, the heat generated by the engine is less than the users need that day. The University gains a financial benefit to taking control of their own energy needs.
Whilst the fuel is natural gas, the efficient way that it is used to meet fluctuating local energy needs for power, heat, chilling and some energy storage is impressive.